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Article

The Influence of Feeding Type on Quality and Nutritional Characteristics of Pork Fat

by
Agata Górska
1,*,
Magdalena Wirkowska-Wojdyła
1,
Ewa Ostrowska-Ligęza
1,
Krzysztof Dasiewicz
2 and
Mirosław Słowiński
2
1
Department of Chemistry, Institute of Food Sciences, Warsaw University of Life Sciences, 159c Nowoursynowska Street, 02-776 Warsaw, Poland
2
Department of Food Technology and Assessment, Institute of Food Sciences, Warsaw University of Life Sciences, 159c Nowoursynowska Street, 02-776 Warsaw, Poland
*
Author to whom correspondence should be addressed.
Appl. Sci. 2024, 14(18), 8291; https://doi.org/10.3390/app14188291
Submission received: 2 August 2024 / Revised: 11 September 2024 / Accepted: 12 September 2024 / Published: 14 September 2024
(This article belongs to the Special Issue Emerging Analytical Techniques in Food Industry and Agricultural Products)
Versions Notes

Abstract

:
The purpose of the study was to analyze the effect of feeding type on selected quality parameters and the nutritional characteristics of pork fat. Fats were extracted by using the modified Folch method from the groin, jowl and trimming shoulder of pigs fed two types of diets: liquid and dry. The peroxide values and fatty acid profiles, as well as their distribution, in the triacylglycerol molecules were determined. Additionally, nutritional indexes and thermal properties, including the oxidative stability of pork fat, were assessed. Among the tested fats, the groin fat was characterized by the best oxidative stability which did not depend on the diet type used. In the case of jowl and trimming shoulder, a higher share of monounsaturated fatty acids was determined in fats of pigs fed a liquid diet, whereas in the groin, jowl and trimming shoulder fats of pigs fed dry feed, a higher share of polyunsaturated fatty acids was found. Fats extracted from the groin, jowl and trimming shoulder of pigs fed a liquid diet showed a more favorable ratio of n-6 to n-3 acids. Despite the different feeding systems used, tested fats were characterized by a similar distribution of fatty acids in triacylglycerol molecules with a positive effect on fat digestibility. It is worth emphasizing that especially in the case of trimming shoulder fat, the influence of a diet used in pigs’ nutrition on quality parameters was noticeable. The trimming shoulder fat of pigs fed a liquid diet was characterized by a longer induction time of oxidation, contained less saturated fatty acids and presented a more favorable fatty acid profile with a beneficial distribution of fatty acids in triacylglycerol molecules.

1. Introduction

Nutrition is one of the most important factors influencing the fat content and composition of fatty acids in meat. Fatty acids from the diet are originally absorbed from the intestine and are then introduced into the tissues. Polyunsaturated fatty acids (PUFA) cannot be synthesized in situ; therefore, their concentration in tissues quickly responds to changes in PUFA content in the diet. Saturated (SFA) and monounsaturated fatty acids (MUFA) are synthesized de novo, and their concentration is less susceptible to the influence of feeding type [1,2,3]. As pigs grow, fat is synthesized sequentially, initially in the subcutaneous fat tissues, then in the intermuscular fat tissues, and finally in the intramuscular fat tissues. The casing of the carcass is subcutaneous fat that constitutes 65% of the total carcass fat tissue, followed by intermuscular fat (30%) and internal fat (about 5%) [4]. The fatty acid composition is the main factor taken into account when determining the nutritional value of meat. The composition of fatty acids affects the quality of meat, especially tissue elasticity, freshness, and taste [5]. Fatty acids are characterized by very different melting points, so any changes in the composition of fatty acids can influence the firmness and softness of the fat in the meat. These changes occur mainly in subcutaneous and intramuscular fat, but also can take place in intermuscular fat [6,7]. The composition of fatty acids can be changed during animal breeding by introducing appropriate changes in the diet. As consequences of diet modifications, it is possible to reduce the share of SFA and increase the share of PUFA, e.g., long-chain n-3 fatty acids with a positive impact on the nutritional value of meat [7,8,9]. It was shown that the addition of oleic acid belonging to MUFA to the diet reduced the level of cholesterol in human blood plasma [10]. The level of n-3 PUFA can be increased by enriching feed with linseed. It was proven, that the use of feed with the addition of linseed led to an increase in the content of n-3 fatty acids in pork fat [11]. Doichev et al. [12] found that the addition of 4% and 8% of linseed to the diet of fattening pigs changed the composition of fatty acids, and caused an increase in the content of α- linolenic acid. It was confirmed that sunflower oil can also be added to feed to improve the fatty acid profiles of fat. Mitchaothani et al. [13] reported a positive effect of 5% sunflower oil supplementation on fatty acid profiles of pork fat by increasing the content of PUFA and reducing the content of saturated and monoenoic fatty acids. Nuernberg et al. [14] used a 5% addition of olive oil and linseed oil to feed to enrich the diet of pigs. There was a significant increase in the content of α-linolenic acid in the fat of pigs fed linseed oil. Wasilewski et al. [15] examined the effect of feed with the addition of CLA diene on the fatty acid profile of bacon fat. They found that with the increased concentration of CLA in the diet, the content of MUFA decreased and the content of PUFA increased [15,16]. Migdał et al. [17] also conducted studies on the incorporation of CLA in pig diets and confirmed that supplementation with CLA can positively affect the nutritional value of pork without changing its taste.
Pork fat presence in products such as sausages and hams is considered to be beneficial as it ensures the right flavor and consistency. Pork fat is characterized by an unfavorable ratio of fatty acids from the n-6 to n-3 families, which significantly exceeds the recommended ratio of 4:1 [18]. Feed modifications can be useful in improving the fatty acid profile and quality of pork fat. Supplementation of the diet with properly selected oils makes it possible to reduce the content of SFA in favor of a greater share of MUFA and PUFA. Correct feeding management can be an effective way to improve pork quality by increasing the intramuscular fat content and improving the pork amino acid and fatty acid profiles in finishing pigs [19,20,21]. Liu et al. [22] investigated the effects of fermented mixed feed (FMF) on growth performance, carcass traits, meat quality, muscle amino acid, and fatty acid composition in finishing pigs. The dietary treatments included a basal diet, a basal diet enriched with 5% FMF, and a basal diet with 10% FMF. The authors reported that a diet supplemented with 10% FMF significantly increased the concentration of n-3 polyunsaturated fatty acids, n-6 PUFA, and total PUFA, and the PUFA to SFA ratio. They concluded that 10% FMF dietary supplementation improved the pigs’ growth performance and meat quality, as well as altering the profiles of muscle fatty acids and amino acids in finishing pigs. The type of diet can also influence the growth intensity, feed consumption, and carcass characteristics. Mykhalko et al. [23] investigated the fattening and carcass qualities of Irish-origin pigs fed liquid and dry diets. They studied the quality of the carcasses, including the slaughter characteristics; the weight and proportion of valuable parts of the carcass; and the total weight and proportion of meat, fat, and bone. They reported that the liquid fattening of pigs resulted in an increase in average weight at weaning, an increase in growth intensity and relative growth, and a reduction in age to 100 kg weight. Pigs fed liquid diets also had higher meat mass and higher fat percentage. The authors concluded that the study of fattening and slaughter indicators of pigs revealed a reliable advantage of a liquid feeding system compared to feeding system involved the use of dry feed. Vázquez et al. [24] investigated the effect of wet feeding of finishing pigs on production performance, carcass composition and meat quality. They pointed out that wet-fed pigs had higher hot and cold carcass weights than dry-fed pigs. The authors found no differences in the protein and carbon content, pH, or water holding capacity of the meat between the two forms of feeding. They reported that the hardness, gumminess, chewiness, and toughness of the meat were higher in dry-fed pigs than wet-fed pigs. The shear strength, adhesiveness, elasticity, and cohesiveness were independent of the diet. They concluded that the wet-fed pigs had better productive performance, carcass composition and meat characteristics than the dry-fed pigs.
To the best of our knowledge, no studies have been conducted on the influence of dry and liquid feed forms on the precise pork fat quality.
Taking the above into consideration, the objective of this study was to analyze the impact of feeding type on the quality and nutritional characteristics of pork fat, including peroxide values, fatty acid profiles, and their distribution between the sn-2 and sn-1,3 positions in the triacylglycerol molecules. Additionally, oxidative stability and nutritional indexes—such as the polyunsaturated fatty acid/saturated fatty acid ratio, atherogenicity index, thrombogenicity index, hypocholesterolemic/hypercholesterolemic index, and health-promoting index—were assessed.

2. Materials and Methods

2.1. Material

The protocol was conducted in compliance with the European Union’s regulations concerning the protection of experimental animals. Since the study protocol did not introduce any additional actions than routine farm practices, no approval by the Local Ethical Committee was necessary. The study was performed on a private commercial pig farm located in central Poland. The feeding experiment was conducted in two groups of animals comprising 40 individuals each: a control group, in which a dry diet was applied, and an experimental group, fed a liquid diet. Fattening was carried out in two periods: in the first period (33 days), during which the weight of pigs increased from 40 to 70 kg, the animals received a mixture of grower, and during the second period (48 days) with weight increases from 70 to 110 kg, the animals were fed a mixture of finisher. During the experiments, the animals were kept in group pens equipped with nipple drinkers. A semi ad libitum feeding system was used (the amount of the mixture given to pigs was increased depending on the individual intake of the daily food ration). Liquid and dry feed systems were developed based on the specifications presented in Table 1. When the pigs reached a body weight of about 110 kg, they were slaughtered in accordance with good production practice in an industrial slaughterhouse. After post-slaughter treatment, the carcasses were immediately cooled in a two-stage system to a temperature no higher than 7 °C. After the maturation process (2 days), the carcasses were disassembled into basic elements and research material was obtained. Fat samples (from each tested element: groin, jowl, and trimming shoulder) were collected from each animal individually. Then, the collected samples were combined and homogenized by mixing. A total of approximately 5 kg of fat from the trimming shoulder, jowl, and groin was selected for analysis. The samples were vacuum-sealed in barrier polyethylene bags immediately after collection and transported to the laboratory under cold conditions.

2.2. Methods

2.2.1. Fat Extraction

Fat from pork samples was extracted using the modified Folch method according to the procedure described by Boselli et al. [25,26]. Before extraction, samples were mechanically ground to facilitate lipid release from the matrix. Then, 100 mL of a mixture of methanol and chloroform in a 1:1 (v/v) ratio was added to 60 g of pork material (groin, jowl, and trimming shoulder). The resulting mixture was mixed using a shaker for 3 min. After shaking, the samples were placed in a dryer at 60 °C for 20 min. The samples were removed from the dryer and cooled down. Then, 100 mL of chloroform was added, and the mixture was shaken for 3 min. The obtained mixture was filtered through a filter funnel and 70 mL of aqueous KCl solution was added. Then, the mixture was transferred to a separatory funnel where it was separated into two phases. The lower phase was collected into a flask and anhydrous MgSO4 was added to remove the remaining water. The solvents were evaporated using a vacuum evaporator. Residual solvents were removed in an atmosphere of nitrogen. The obtained fat samples were stored at −20 °C until analysis.

2.2.2. Oxidative Stability of Pork Fats

The oxidative stability of fat was assessed using pressure differential scanning calorimetry (PDSC) by determining the induction time of oxidation reaction. The analysis was performed using the Thermal Analysis DSC Q20 apparatus (TA Instruments, Newcastle, DE, USA). The weight of the fat sample used for determinations ranged from 3.4 to 3.8 mg. The test was performed in isothermal conditions at three different temperatures—100 °C, 120 °C, and 140 °C—at a pressure of 1400 kPa [27].

2.2.3. Determination of Peroxide Value

With an accuracy of 0.001 g, 2 g of fat was weighed on an analytical scale. Then, 25 mL of a mixture of chloroform and acetic acid in a 2:3 (v/v) ratio and 1 mL of potassium iodide were added. The flask was immediately capped, stirred for 1 min, and left in the dark for 5 min. After 5 min, 75 mL of distilled water and five drops of 2% starch solution were added. The released iodine was titrated with Na2S2O3 solution (0.002 mol/L) until discoloration lasted at least 2 min. A blank test was also performed [28].

2.2.4. Determination of Fatty Acid Profiles

The determination of fatty acid profiles was performed using a gas chromatograph YL6100 GC (Young Lin Bldg., Anyang, Hogyedong, Republic of Korea). First, the samples were transformed into volatile derivatives in the following procedure: one drop of fat was mixed with 2 mL of hexane, and then 2 mL of 1 mol/L KOH solution in methanol was added. The samples were stored in a dryer at 40 °C for 20 min. The top layer was removed and transferred to vials with anhydrous MgSO4 [29]. For determinations, 1 μL of methylated fatty acids was used. Nitrogen was applied as the carrier gas. The apparatus was equipped with a BPX-70 capillary column (SGE Analytical Science, Milton Keynes, UK) with the following parameters: length: 60 m; film thickness: 0.25 μm; and inner diameter: 0.25 mm. The conditions in the chromatograph during the separation of fatty acid methyl esters were as follows: initial temperature: 70 °C; time: 30 s; temperature increase to 160 °C (rate 15 °C/1 min); temperature increase to 200 °C (rate 1.1 °C/1 min); temperature increase to 225 °C (rate 30 °C/1 min); final temperature 225 °C/1 min; detector temperature: 250 °C; and injector temperature: 225 °C [30]. The fatty acids were identified based on retention times on the chromatogram compared to the FAME mixture standard (Supelco 37 Component FAME Mix, Sigma-Aldrich, Bellefonte, PA, USA). The individual fatty acids from fatty acid composition analysis were reported as a percentage of the total fatty acids.

2.2.5. Nutritional Indexes

The results for the fatty acid profiles enabled nutritional indexes, such as polyunsaturated fatty acid/saturated fatty acid ratio PUFA/SFA [31], index of atherogenicity (IA) [32], index of thrombogenicity (IT) [32], hypocholesterolemic/hypercholesterolemic index (HH) [33], and health-promoting index (HPI) to be calculated [34].

2.2.6. Distribution of Fatty Acids between sn-2 and sn-1,3 Positions of Triacylglycerols

In order to define the distribution of fatty acids between the sn-2 and sn-1,3 positions, enzymatic hydrolysis using pancreatic lipase was performed. To the centrifuge tube with 0.1 g of fat sample, the following solutions were added: 1 mL of aqueous TRIS-HCl solution (1 mol/L), 0.1 mL of CaCl2 solution (2.2%), and 0.25 mL of bile salt solution (0.05%). The sample was mixed using a vortex for 30 s. Then, 20 mg of pancreatic lipase was added, and the solution was mixed again for 30 s using vortex. The reaction was stopped by adding 1 mL of 6 mol/L hydrochloric acid. Additionally, 4 mL of diethyl ether was added to recover lipid fraction from the hydrolysis medium. The samples were placed in a centrifuge for 5 min at 4000 rpm. After centrifugation, the upper layer was transferred to a 10 mL tube. The samples were dried under nitrogen to a volume of 0.2–0.5 mL and then applied to chromatographic plates and placed in a chamber with the development solution (hexane–diethyl and ether–acetic acid in ratio 50:50:1 (v/v/v)). The gel containing monoacylglycerols fraction with fatty acids in the sn-2 position was scraped off into a screw-capped test tube, extracted twice with 1 mL of diethyl ether and centrifuged. The ether layers were collected and entirely evaporated under nitrogen, and then the sample was dissolved in n-hexane and derivatized to volatile fatty acids methyl esters, as described above for the determination of the fatty acid profiles, and injected into the gas chromatograph to obtain the fatty acid profiles [30]. The proportion of fatty acids esterified at the sn-1,3 positions of the triacylglycerols was calculated using the following formula:
sn-1,3 = [3 × (FA in TAGs) − (FA in sn-2 MAG)]/2
sn-1,3—percentage of a given fatty acid in the sn-1 and sn-3 positions [%],
FA in TAGs—percentage of a given fatty acid in starting triacylglycerols [%],
FA in sn-2 MAG—percentage of a given fatty acid in sn-2 monoacylglycerols [%].

2.2.7. Statistical Analysis

The results were analyzed in the Statistica program; one-way analysis of variance and Tukey’s test were used with a significance level of α = 0.05 to compare significant differences among samples. Means and standard deviations were calculated in Microsoft Excel 2010. The determinations were performed in triplicate.

3. Results and Discussion

3.1. Oxidative Stability of Groin, Jowl, and Trimming Shoulder Fats

The results for the oxidative stability of groin fat, jowl fat, and trimming shoulder fat are presented in Table 2.
Based on the results regarding the oxidative stability of pork fats at a temperature of 100 °C, the influence of the type of feed on the induction time in jowl fat and trimming shoulder fat can be observed. Fat extracted from the jowl of pigs fed dry feed was characterized by a longer induction time of oxidation (91.65 min) than fat from pigs offered liquid feed (89.05 min). In the case of trimming shoulder fat, an inverse result was observed. Fat extracted from the trimming shoulder of pigs fed a liquid diet was more oxidatively stable. There were no statistically significant differences in the oxidative stability of groin fat; induction time of oxidation in both cases (GF_L and GF_D) was approximately 108 min. In the oxidative stability test carried out at the temperature of 120 °C (Table 2), the influence of the type of feed on the oxidative stability of pork fat obtained from jowl and trimming shoulder was found. In the case of fat extracted from the jowl of pigs fed liquid feed, the induction time was longer (21.76 min) than in the fat of dry-fed pigs (20.70 min). The use of liquid feed had a positive effect on the oxidative stability of fat extracted from jowl and trimming shoulder by extending the length of induction time of oxidation. In groin fat, there was no dependance between the type of feed and the induction time of pork fat oxidation. Pork groin fat was less prone to oxidation than fats obtained from the jowl and trimming shoulder. The worst oxidative stability was observed in the case of jowl fat of pigs fed dry feed (20.70 min). In the oxidative stability test carried out at a temperature of 140 °C (Table 2), the influence of the feed system on the induction time of the oxidation process in the case of jowl and trimming shoulder fats was found. In the case of trimming shoulder fat, a shorter induction time of oxidation reaction was observed for fat samples of dry-fed pigs. An inverse result was demonstrated in pig jowl fat. The fat of pigs fed a liquid diet was characterized by a shorter induction time (4.04 min) compared to the fat of pigs offered dry feed (5.29 min). In the case of groin fat, no statistically significant differences were found between the oxidation induction time of fats from liquid- and dry-fed pigs. Based on the obtained results, it can be summarized that the influence of feed type on oxidative stability was found in pork fats extracted from jowl and trimming shoulder at all three test temperatures. However, in groin fat, no statistically significant differences were found in the induction time of fat oxidation. Comparing the oxidation induction time, it can be concluded that the pork fat extracted from groin was characterized by the best oxidative stability, which could be influenced by the highest SFA content, while the jowl fat, with the lowest SFA content, was the least oxidatively stable. In the case of trimming shoulder fat at all three test temperatures (100 °C, 120 °C, 140 °C), the fats of pigs fed a liquid diet presented better oxidative stability than the fats of dry-fed pigs. In the context of the obtained results, the oxidation is a complex reaction which results in many new products. Hydroperoxides, the quite unstable primary oxidation compounds, are formed during the induction period in the earlier stages of oxidative degradation [35,36]. In the advanced stages of oxidation, they can be easily transformed to secondary oxidation products. These secondary products—originating from rearrangements in monomeric products; from decomposition into lower-mass products, such as aldehydes, alcohols, and hydrocarbons; or from polymerization (dimers and oligomers) [37,38]—can be formed at different temperatures and can affect the oxidative stability of fats. Moreover, oxidative stability is significantly influenced by the presence of pro- and antioxidant substances in the diet. There is still a need to conduct more detailed studies on topics including the influence of the above-mentioned aspects on the oxidative stability of groin, jowl, and trimming shoulder fats.

3.2. Peroxide Value of Groin, Jowl, and Trimming Shoulder Fats

The peroxide values of the analyzed pork fat samples are presented in Table 3. Regardless of the fat type, pork fats of pigs fed a liquid diet were characterized by a higher peroxide value than fats of pigs fed dry feed. The highest peroxide values were determined for the groin and jowl fats of pigs fed liquid feed: 1.42 meq O2/kg of fat and 1.41 meq O2/kg of fat, respectively. The lowest peroxide value was determined in the case of jowl fat of dry-fed pigs (0.71 meq O2/kg of fat). The largest difference between fat peroxide values depending on the type of feed was observed in the case of jowl fat (1.41 meq O2/kg of fat for JF_L versus 0.71 meq O2/kg of fat for JF_D). In the case of groin or trimming shoulder fat, the differences in the peroxide value were much smaller than those obtained for the jowl fat. In the case of groin fat of dry-fed pigs, a 17.6% lower peroxide value than that for the fat of pigs offered liquid feed was observed, while in the case of trimming shoulder fat, a 13.01% reduction in peroxide value was determined. Based on the obtained results, it can be stated that the type of diet influenced the peroxide value of tested fats. The use of dry feed in pig nutrition reduced the peroxide value of pork fats extracted from groin, jowl, and trimming shoulder.
Krupska and Olkiewicz [39] conducted research on the influence of the location of fat in a pork carcass on its physicochemical properties. The authors determined the peroxide, acid, and iodine values of jowl, groin, bacon, and lard fats. For groin fat, the peroxide value reached 1.09 meq O2/kg of fat. This result was similar to the value obtained for the groin fat of dry-fed pigs in this study (1.17 meq O2/kg of fat). The jowl fat of pigs fed a liquid diet was characterized by an average peroxide value of 1.41 meq O2/kg of fat. Krupska and Olkiewicz [39] reported a similar peroxide value for jowl fat (1.37 meq O2/kg of fat).

3.3. Fatty Acid Profiles and Health Indexes of Groin, Jowl, and Trimming Shoulder Fats

In Table 4, the percentage composition of fatty acids in groups of the tested pork fats is presented. Three main groups of fatty acids were identified: monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and saturated fatty acids (SUFA) in fats extracted from groin, jowl, and trimming shoulder of pigs fed liquid and dry diets. MUFAs were the main group of fatty acids found in groin, jowl, and trimming shoulder fats, their average share ranged from 46.11% ± 3.03 for GF_L to 52.15% ± 4.14 for TSF_L. The highest MUFA share was found in trimming shoulder fat of pigs fed a liquid diet. In the case of groin fat, no statistically significant differences were found between the average MUFA share in fat of liquid-fed (46.11% ± 3.03) and dry-fed (46.50% ± 2.84) pigs. The type of feed influenced the MUFA content in jowl fat and trimming shoulder fat. In both cases, the fats of pigs offered liquid feed (JF_L and TSF_L) were characterized by a higher MUFA percentage content. The greatest influence of the type of diet was found in the share of MUFA in trimming shoulder fat. The fat of pigs fed liquid feed (TSF_L) contained 10.72% more MUFA than the fat of pigs offered dry feed (TSF_D).
Saturated fatty acids (SFA) were the second group of fatty acids in terms of average percentage content in the fatty acid groups. The highest SFA share was found in the groin fat of liquid-fed pigs (43.11% ± 1.32), and the lowest in the jowl fat of pigs fed a dry diet (35.89% ± 0.86). Groin and jowl fats extracted from pigs fed dry feed (GF_D, JF_D) contained less SFA than fats from pigs offered liquid feed (GF_L and JF_L). The opposite result was reported in the case of trimming shoulder fat—the fat of pigs offered liquid feed was characterized by a lower SFA share. The consumption of saturated fatty acids, according to the FAO/WHO dietary recommendations [40], should be less than 10% of the daily energy. The high consumption of these fatty acids may lead to the development of diseases such as obesity, circulatory system disorders, and digestive system cancers. Therefore, it is very important to modify the pigs diet to replace saturated fatty acids in the diet with mono- and polyunsaturated fatty acids.
It is worth emphasizing that the type of feed system influenced the average percentage content of PUFA in all three types of fat. The average PUFA content in groin, jowl and trimming shoulder fats ranged from 10.78% ± 1.02 for GF_L to 13.67% ± 1.89 for TSF_D. A higher PUFA content was found in fat extracted from dry-fed pigs compared to the fat of pigs fed a liquid diet. Alonso et al. [41] examined the influence of fat in the diet of fattened pigs on the quality of meat, the profile of fatty acids and the sensory quality of pork. The following feed systems were used in the study: control, with the addition of animal fat, soybean oil (1%) and calcium soaps from palm oil (1%). In the intramuscular fat of pigs fed a soybean-oil-supplemented diet, the average SFA content was 34.64%, MUFA content was 45.66%, and PUFA content was 18.45%. Lu et al. [42] conducted research on the effect of soy addition on the fatty acid profile of pork fat. In their research, soybean meal (18.60%) and soybean oil (3%) were used in pigs’ diets. The average SFA content reached 34.97%. This value was consistent with the result obtained in this study for the jowl fat of pigs fed dry feed (JF_D). In the research conducted by Lu et al. [42], the PUFA content (16.31%) was higher than the values found in this study in the case of groin, jowl, and trimming shoulder fats, for which the PUFA share did not exceed 14%.
In Table 4, the results determining the ratio of fatty acids from the n-6 to n-3 families in groin fat, jowl fat, and trimming shoulder fat are presented. Pork fats of pigs fed a liquid diet are characterized by a lower ratio of n-6 to n-3 fatty acids than the fats of dry-fed pigs. In fats extracted from groin and trimming shoulder fats, statistically significant differences were found depending on the feed type. The greatest difference in the n-6 to n-3 ratio was observed in the trimming shoulder fat. In the case of fat of pigs fed a liquid diet, it reached 8.57, and fed dry feed—11.01. In studies conducted by Alonso et al. [41], in intramuscular fat of pigs fed a diet with the addition of 1% soybean fat, the n-6 to n-3 ratio of 11.03 was reported. This result is in agreement with the value obtained in this study for TSF_D. For jowl and groin fats (dry feed), the values of n-6 to n-3 fatty acids ratio were lower: 10.54 and 10.37, respectively. According to the recommendations, the ratio of n-6 to n-3 fatty acids should be less than 5:1; unfortunately, in the daily diet of Europeans, this proportion is much higher and amounts even to 15–20:1. Therefore, groin, jowl and trimming shoulder fats of liquid-fed pigs, characterized by a lower n-6 to n-3 fatty acid ratio, can be considered as more beneficial from a health point of view than the fats of pigs offered dry feed.
Based on the results obtained for groin, jowl, and trimming shoulder fats referring to health indices—such as the atherogenicity index (IA), thrombogenicity index (IT), hypocholesterolemic/hypercholesterolemic ratio (HH), and health-promoting index (HPI) (Table 4)—it can be stated that no significant effect of the diet used on health indices values was observed. The lowest atherogenic index was calculated for JF_D (IA = 0.44), whereas the highest value of IA was observed for GF_L (IA = 0.57). The IA has been widely used for evaluating seaweeds, crops, meat, fish and dairy products. In the case of meat samples, the IA reached values ranging from 0.165 to 1.320, depending on the meat type. Mir et al. [43] studied the properties of chicken (Caribro Vishal) meat and reported IA indexes reaching values from 0.165 to 0.634. The authors demonstrated the significant impact of a flaxseed-oil-supplemented diet on the lowering of IA value. Salvatori et al. [44] calculated IA for two different lamb types (Gentile di Puglia and Sopravissana) and reported the values from 0.99 to 1.32. In the case of the intramuscular fat of the Longissimus dorsi muscle of high- and low-birth-weight pigs at 150 days of age, the IA reached values within the range of 0.27–0.31 [45]. Considering the thrombogenicity index, the lowest value was found for JF_D (IT = 1.01) and the highest value for GF_L (IT = 1.35). The obtained IT values are in agreement with the results presented by other authors. Majdoub-Mathlouthi et al. [46] reported, that in the case of Barbarine lambs reared on rangelands or indoors on hay and concentrate, IT reached values within the range of 1.10–1.15. In the study of Wójciak et al. [47], the influence of sonication on the oxidative stability and nutritional value of organic dry-fermented beef was examined. The authors reported that IT for testes samples reached the values 1.10–1.34. In the present study, the jowl fat of pig-fed dry feed was characterized by the highest value of the HH index (HH = 2.51), whereas in the case of groin fat (liquid feed) the lowest value of that index (HH = 1.99) was calculated. Similar results were reported by other authors for chicken meat (HH—2.658–2.786) [48], lamb meat (HH = 1.92) [33], and beef cattle meat (HH = 1.56–2.08) [49]. HPI calculated for studied fats reached values from 1.75 for GF_L to 2.27 for JF_D. The obtained results are similar to those obtained for intramuscular lipids of the longissimus thoracis muscle from pigs receiving a diet with different n-6/n-3 PUFA ratios. The authors reported HPI values of 2.21 and 2.23 in the case of diets with a low n-6/n-3 PUFA ratio (1.4:1) and high n-6/n-3 PUFA ratio (9.7:1), respectively [50]. Dal Bosco et al. [51] studied the nutritional indexes of the breast meat of two poultry genotypes with different growth rates—slow-growing (SG, growth rhythm < 20 g/d) and fast-growing (FG, growth rhythm > 40 g/d)—and calculated HPI values for SG and FG chickens of 1.81 and 1.59, respectively.
It is worth mentioning that both IA and IT can provide information regarding the potential impact of individual fatty acids on the likelihood of atherosclerosis occurrence and the tendency for thrombus and clot formation in blood vessels. Fats characterized by lower IA and IT values are thought to have beneficial health effects due to minimizing the risk of cardiovascular diseases. Special attention should be paid to fats with IA values below 1.0 and IT values below 0.5 as they are particularly desirable for human nutrition [52,53]. Based on the obtained results, it can be summarized that in the case of studied pork fats, all samples were characterized by IA lower than 1.0, but IT was found to exceed the recommended value, which can have consequences for the increased risk of clot formation in the blood vessels and cardiovascular disease.
In Table 5, Table 6 and Table 7, the share of selected fatty acids in pork fat of the groin, jowl and trimming shoulder is shown. In the analyzed fats, the dominant fatty acid was oleic acid (C18:1 n-9), its share ranged from 42.30% for GF_L to 48.10% for TSF_L. Another fatty acid found in significant amounts was palmitic acid (C16:0) with a percentage content ranging from 22.07% for JF_L to 25.16% for GF_D. The most abundant PUFA was linoleic acid (C18:2 n-6) (8.91% for TSF_L—11.87% for TSF_D).
An influence of the feeding type on the content of linoleic acid (C18:2 n-6) was found in groin fat (Table 5). In the case of fat of pigs fed a liquid diet, the average content of linoleic acid was 9.17%, and in dry feeding system—it was higher (10.44%). In groin fat, the feeding system had no effect on the content of the following acids: myristic (C14:0), palmitic (C16:0), stearic (C18:0), and oleic (C18:1). The share of oleic fatty acid (C18:1) in the groin fat of pigs fed liquid or dry feed reached 42.30% and 42.66%, respectively. Lu et al. [42] reported a similar oleic acid content in their research. The fat of pigs fed a diet containing soybean raw materials contained 42.40% of oleic acid.
In the case of jowl fat, oleic acid (C18:1) was the dominant fatty acid (Table 6). In the fat of pigs fed liquid feed, its average content was higher (47.83%) than in the fat of pigs fed a dry diet (46.93%). Alonso et al. [41] determined a similar content (45.58%) of oleic acid in their studies. There was no statistically significant effect of the feed type on the content of palmitic acid (C16:0). The content of palmitic acid in the tested fats was very similar to the values obtained by Alonso et al. [41] (22.15%) and by Lu et al. [42] (21.94%). The percentage content of myristic (C14:0) and stearic (C18:0) acids was higher in pork fat of pigs fed liquid feed than in the fat of pigs offered dry feed. It is worth mentioning that the feed type had an influence on the share of linoleic acid (18:2 n-6), which was present in higher amounts in the jowl fat of dry-fed pigs.
In the pork fat of trimming shoulder, the greatest influence of the feeding type on the content of fatty acids was found (Table 7). The share of MUFA was higher in the case of pork fat of pigs fed a liquid diet. The fat of liquid-fed pigs contained 48.1% oleic acid (C18:1), while the fat of pigs fed dry feed contained 42.81%. The difference in the oleic acid percentage content in these two fat samples (TSF_L and TSF_D) was statistically significant. Lu et al. [42] reported a very similar content of oleic acid (42.40%) as in this study for fat of pigs offered dry feed. The saturated fatty acids found in large amounts in trimming shoulder fat were palmitic acid (C16:0) and stearic acid (C18:0). The content of these fatty acids was lower in pork fat of pigs fed a liquid diet. In the study conducted by Lu et al. [42], the percentage composition of fatty acids in pork fat was similar to that reported in this study. According to Lu et al. [42], the highest content of oleic fatty acid (C18:1) (42.40%) was found in the pork fat of pigs fed a diet containing soy raw materials. A high content of palmitic acid (C16:0) was also found (24.28%). In the research conducted by Lu et al. [42], the content of linoleic acid (C18:2 n-6) was higher than that found in this study and amounted to 13.66%. In this study, in the tested jowl, groin, and trimming shoulder fats, the content of linoleic acid did not exceed 12%. Notably, in the case of trimming shoulder fat, a higher share of linoleic acid was found when a dry feeding system was applied.

3.4. Distribution of Fatty Acids between Internal (sn-2) and External (sn-1,3) Positions of Triacylglycerols in Groin, Jowl, and Trimming Shoulder Fats

In Table 5, Table 6 and Table 7, the distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols (TAG) of groin, jowl, and trimming shoulder fats, as well as the share of individual acids in the internal position, are presented.
In groin fat, the highest content of palmitic acid (C16:0) was found in the sn-2 position, 61.67% and 62.14% in the case of fat extracted from the groin of pigs fed liquid and dry feed, respectively (Table 5). The share of this fatty acid in the sn-2 position in the groin fat of pigs offered liquid feed was 84.04%, and it was higher than in the case of the dry feeding system (82.32%). In the fat extracted from pigs fed liquid feed, the lowest amount of stearic acid (C18:0) was found in the sn-2 position, and its share in this position reached 10.93%. However, in the fat of dry-fed pigs, the lowest amount of myristic acid (C14:0) was determined in the sn-2 position, and its share in internal position was similar to that of palmitic acid (C16:0). The share of linoleic acid (C18:2 n-6) in the sn-2 position was higher in triacylglycerols of pork fat of pigs fed a liquid diet (19.77%) than in the triacylglycerols of fat of pigs offered dry feed (17.52%).
In the case of jowl fat, the dominant acid in the sn-2 position was palmitic acid (C16:0) (Table 6). In the triacylglycerol molecules of fat of dry-fed pigs, a higher content of palmitic acid was found in the sn-2 position—59.03%, than in the fat of pigs fed a liquid diet—57.49%. The share of this fatty acid in the sn-2 position of triacylglycerols in the case of both fats was approximately 88%. Based on the obtained results, it can be stated that palmitic acid (C16:0) was mainly located in the internal position in the triacylglycerol molecule and unsaturated fatty acids (oleic acid and linoleic acid) occupied mainly external positions in triacylglycerol molecules as their share in the sn-2 position was not high.
In the pork fat extracted from trimming shoulder fat (Table 7), as in the case of groin and jowl fats, palmitic acid (C16:0) was most abundant in the sn-2 position. Its share in internal position reached 84.35% for TSF_L and 82.29% for TSF_D. The share of unsaturated fatty acids in the sn-2 position was much lower—in the case of oleic acid, it reached 14.44% for TSF_L and 14.43% for TSF_D. Considering the share of linoleic acid, it can be observed that 21.29% and 19.29% of this fatty acid was esterified in the sn-2 position in TSF_L and TSF_D samples, respectively. Taking the above into consideration, it can be concluded that in the studied fats, unsaturated fatty acids were mainly located in the external positions of triacylglycerol molecules.
Summarizing the obtained results regarding the distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols of groin, jowl, and trimming shoulder fats and the share of individual fatty acids in the internal (sn-2) position, it can be stated that the internal position in the triacylglycerol structure in the case of studied fats was mainly occupied by saturated fatty acids: myristic (14:0) and palmitic (C16:0) acids. These results are in accordance with the literature, as pork fat was reported to contain 80–90% of palmitic acid at the sn-2 position [54,55]. The share of unsaturated oleic and linoleic fatty acids in the sn-2 position was not high. This proved that unsaturated fatty acids were mainly located in external positions (sn-1,3) in the triacylglycerol molecules of pork fats. Taking into account the structure of triacylglycerols, it can be stated that there was no significant differences in the distribution of fatty acids between internal (sn-2) and external (sn-1,3) positions in groin, jowl, and trimming shoulder fats of pigs fed dry or liquid diets. Such distribution of fatty acids among positions in triacylglycerols is typical of pork fat [56,57].
It is worth highlighting that the distribution of fatty acids in the triacylglycerol molecules of fats is very important from a technological and health point of view. It affects the digestion and absorption of fatty acids in the human body. Pancreatic lipase, taking part in fat digestion, is capable of detaching fatty acids located only in the external positions (sn-1,3) of triacylglycerol molecules, and after this process, monoacylglycerols with a fatty acid in the internal position (sn-2) are formed. Pork fat contains more saturated fatty acids in the sn-2 position than vegetable fats, in which this position is occupied mainly by unsaturated fatty acids. In lard, for example, the sn-2 position is mainly occupied by palmitic acid (C16:0). When saturated fatty acids are located in the sn-2 position, it has a positive effect on the fat absorption process. Saturated monoacylglycerols and polyunsaturated fatty acids and their salts obtained after hydrolysis have a high absorption rate. A large share of saturated fatty acids in the external positions (sn-1,3) of triacylglycerols has an adverse effect on fat digestibility. Saturated fatty acids present in these positions, detached from triacylglycerol molecules after the digestion process, tend to form poorly soluble calcium salts, which may result in calcium deficiencies in the body and significant deterioration of fat absorption [55].
Authors have reported many advantages of applying liquid feeding systems compared to dry feeding. These include improved nutrient utilization, the possibility of using liquid by-products, and improved animal performance [58,59,60]. Additionally, introducing liquid to a diet can help digestion by facilitating the breakdown of nutrients, which can further enhance feed conversion efficiency. Liquid feeding form can also enhance gut health, reduce the need for feed medications and improve animal well-being [60,61]. Liquid feeding systems often improve the palatability of the feed, which can lead to increased feed intake. This increase in feed intake can often lead to improved growth rates, as the pigs are consuming more nutrients that are vital for their development. Notably, fat quality is influenced by physical and nutritive characteristics, which are both related to the fatty acid composition of the fat depots. The major issues related to fat quality are fat softness, oxidative rancidity, and the impact of the composition of pork fat on human health. The composition of dietary fat, used in liquid and dry feeding systems in this study (Table 1), could affect the quality of the fat deposits in pigs. Benz et al. [61] reported that pigs’ diets supplemented with soybean oil increased the amount of unsaturated fat deposited. Increasing the feeding duration of soybean oil increased C18:2 n-6, PUFA, UFA:SFA ratio, and PUFA:SFA ratio and decreased C18:1 cis-9, C16:0, SFA, and MUFA concentrations in jowl fat and backfat. It should be highlighted that feeding ingredients with relatively high levels of unsaturated fatty acids increase the degree of unsaturation of the fat tissue, consequently decreasing fat firmness, and negatively impacting fat quality.
The empirical results reported herein should be considered in the light of some limitations. The primary limitation to the generalization of these results is the size of the research group. More studies with larger sample sizes should be conducted to reconfirm the findings. The second limitation concerns the lack of previous research studies on the topic, so the possibility of comparing the results with those of other authors was limited. The third limitation is the lack of information about the content of each fatty acid contributed by the type of diet (in mg/100 g), so it is likely that the amounts are different in the liquid and dry formulations which could influence the results presented in the study.
There is still a need for additional studies regarding the impact of the liquid and dry feeding systems on the quality of pork fat, including fatty acid profiles, their distribution between internal and external positions in triacylglycerol molecules, peroxide value, oxidative stability, and nutritional indexes.

4. Conclusions

Based on the results obtained in this study, it can be concluded that there was no effect of feeding system on the oxidative stability of groin fat, whereas in the case of jowl and trimming shoulder fats, the influence of the chosen diet on the susceptibility of fats to oxidation was reported. Trimming the shoulder fat of pigs fed a liquid diet was more oxidatively stable than the fat of pigs offered dry feed. The opposite dependence was determined for jowl fat. The obtained results showed that the feeding system influenced peroxide values of tested fats. Pork fats of pigs offered liquid feed were characterized by a higher peroxide value. There was a positive effect of the liquid diet form on the average MUFA content in pork jowl and trimming shoulder fats, whereas groin, jowl, and trimming shoulder fats of dry-fed pigs were characterized by a higher polyunsaturated fatty acids share. It is worth mentioning, that in the case of applying liquid feeding system, pork fats were characterized by a more beneficial ratio of n-6 to n-3 acids. Feeding type did not influence the distribution of fatty acids in triacylglycerol molecules, which was typical for pork fat with saturated fatty acids mainly located in the internal position and unsaturated fatty acids—in external positions of the triacylglycerol structure. Notably, the influence of diet on quality and nutritional characteristics was especially noticeable in the case of trimming shoulder fat. The trimming shoulder fat of pigs offered a liquid diet was more oxidatively stable, contained less saturated fatty acids and presented a more favorable fatty acid profiles, with a more beneficial distribution of fatty acids in triacylglycerol molecules.

Author Contributions

Conceptualization, M.S., K.D. and A.G.; methodology, M.S., K.D., A.G., M.W.-W. and E.O.-L.; investigation, A.G., M.W.-W. and E.O.-L.; formal analysis, E.O.-L., A.G. and M.W.-W.; writing—original draft preparation, A.G., M.S. and K.D.; writing—review and editing, A.G., M.S. and K.D. All authors have read and agreed to the published version of the manuscript.

Funding

The study was financially supported by sources of the Ministry of Education and Science within funds of the Institute of Food Sciences of Warsaw University of Life Sciences (WULS), for scientific research. Some research equipment was purchased as part of the “Food and Nutrition Centre—modernisation of the WULS campus to create a Food and Nutrition Research and Development Centre (CŻiŻ)” co-financed by the European Union from the European Regional Development Fund under the Regional Operational Programme of the Mazowieckie Voivodeship for 2014–2020 (Project No. RPMA.01.01.00-14-8276/17).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data generated or analyzed during this study are available from the corresponding author on reasonable request.

Acknowledgments

The authors would like to thank Anna Kańkowska for her help in carrying out the analyses and technical support.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Averette, G.L.; See, M.T.; Hansen, J.A.; Sutton, D.; Odle, J. The effects of dietary fat sources, levels, and feeding intervals on pork fatty acid composition. Anim. Sci. J. 2002, 80, 1606–1615. [Google Scholar] [CrossRef] [PubMed]
  2. Rosenvold, K.; Andersen, H.J. Factors of significance for pork quality—A review. Meat Sci. 2003, 64, 219–237. [Google Scholar] [CrossRef]
  3. Stephenson, E.W.; Vaughn, M.A.; Burnett, D.D.; Paulk, C.B.; Tokach, M.D.; Dritz, S.S.; DeRouchey, J.M.; Goodband, R.D.; Woodworth, J.C.; Gonzalez, J.M. Influence of dietary fat source and feeding duration on finishing pig growth performance, carcass composition, and fat quality. Anim. Sci. J. 2016, 94, 2851–2866. [Google Scholar] [CrossRef]
  4. Mourot, J.; Hermier, D. Lipids in mono gastric animal meat. Reprod. Nutr. Dev. 2001, 41, 109–118. [Google Scholar] [CrossRef] [PubMed]
  5. Teye, G.A.; Sheard, P.R.; Whittington, F.M.; Nute, G.R.; Stewart, A.; Wood, J.D. Influence of dietary oils and protein level on pork quality. 1. Effects on muscle fatty acid composition, carcass, meat and eating quality. Meat Sci. 2006, 73, 157–165. [Google Scholar] [CrossRef]
  6. Wood, J.D.; Richardson, R.I.; Nute, G.R.; Fisher, A.V.; Campo, M.M.; Kasapidou, E.; Sheard, P.R.; Enser, M. Effects of fatty acids on meat quality: A review. Meat Sci. 2003, 66, 21–32. [Google Scholar] [CrossRef] [PubMed]
  7. Apple, J.K.; Maxwell, C.V.; Galloway, D.L.; Hutchison, S.; Hamilton, C.R. Interactive effects of dietary fat source and slaughter weight in growing-finishing swine: I. Growth performance and longissimus muscle fatty acid composition. J. Anim. Sci. 2009, 87, 1407–1422. [Google Scholar] [CrossRef]
  8. Piotrowska, A.; Świąder, K.; Waszkiewicz-Robak, B.; Świderski, F. Możliwość uzyskania mięsa i przetworów z mięsa wieprzowego o podwyższonej zawartości wielonienasyconych kwasów tłuszczowych n-3. ŻYWNOŚĆ Nauka Technol. Jakość 2012, 84, 5–19. (In Polish) [Google Scholar]
  9. Wood, J.D.; Enser, M. Manipulating the Fatty Acid Composition of Meat to Improve Nutritional Value and Meat Quality. W: New Aspects of Meat Quality—From Genes to Ethnics (red. P. P. Purslow); Woodhead Publishing: Cambridge, UK, 2017; pp. 501–535. [Google Scholar]
  10. Górecka, D.; Lipidy, W. Mięso—Podstawy Nauki i Technologii (Red. A. Pisula i E Pospiech); Wydawnictwo SGGW: Warszawa, Polska, 2011; pp. 167–177. (In Polish) [Google Scholar]
  11. Kouba, M.; Ensert, M.; Whittington, F.M.; Nute, G.R.; Wood, J.D. Effect of high-linolenic acid diet on lipogenic enzyme activities, fatty acid composition, and meat quality in the growing pig. J. Anim. Sci. 2003, 81, 1967–1979. [Google Scholar] [CrossRef]
  12. Doichev, V.; Angelov, A.; Szostak, S.R.; Katzarov, V. Fatty acid composition of fat tissue triglicerides and skeletal muscle tissue histostructure of pigs fed diet containing flax seed. Technol. Aliment. 2003, 2, 135–141. [Google Scholar]
  13. Mitchaothani, J.; Yuangklang, C.; Wittayakun, S.; Vasupen, K.; Wongsutthavas, S.; Srenanul, P.; Hovinier, R.; Everts, H.; Beynen, A.C. Efects of dietary fat type on meat quality and fatty acid composition of various tissues in growing-finishing swine. Meat Sci. 2007, 76, 95–101. [Google Scholar] [CrossRef] [PubMed]
  14. Nuernberg, K.; Fischer, K.; Nuernberg, G.; Kuechnmeister, U.; Klosowska, D.; Eliminowska-Wenda, G.; Fiedler, I.; Ender, K. Effects of dietary olive and linseed oil on lipid composition, meat quality, sensory characteristics and muscle structure in pigs. Meat Sci. 2005, 70, 63–74. [Google Scholar] [CrossRef] [PubMed]
  15. Wasilewski, P.D.; Nowachowicz, J.; Michalska, G.; Bucek, T.; Lynch, B.; Mullen, A.M. Backfat fatty acid profile of crossbred pigs fed a diet supplemented with conjugated linoleic acid or sunflower oil. Ann. Anim. Sci. 2012, 12, 433–443. [Google Scholar] [CrossRef]
  16. Dilzer, A.; Park, Y. Implication of conjugated linoleic acid (CLA) in human health. Crit. Rev. Food Sci. Nutr. 2012, 52, 488–513. [Google Scholar] [CrossRef]
  17. Migdał, W.; Paściak, P.; Wojtysiak, D.; Barowicz, T.; Pieszka, M.; Pietras, M. The effect of dietary CLA supplementation on meat and eating quality, and the histochemical profile of the m. longissinus dorsi from stress susceptible fatteners slaughtered at heavier weights. Meat Sci. 2004, 66, 863–870. [Google Scholar] [CrossRef] [PubMed]
  18. Turyk, Z.; Osek, M.; Milczarek, A.; Janocha, A. Skład chemiczny mięsa i lipidogram krwi tuczników żywionych mieszankami zawierającymi jęczmień lub pszenżyto. Rocz. Nauk. Pol. Tow. Zootech. 2015, 2, 71–79. (In Polish) [Google Scholar]
  19. Luo, J.; Zeng, D.; Cheng, L.; Mao, X.; Yu, J.; Yu, B.; Chen, D. Dietary b-glucan supplementation improves growth performance, carcass traits and meat quality of finishing pigs. Anim. Nutr. 2019, 5, 380–385. [Google Scholar] [CrossRef]
  20. Wen, W.; Chen, X.; Huang, Z.; Chen, D.; Yu, B.; He, J.; Luo, Y.; Yan, H.; Chen, H.; Zheng, P.; et al. Dietary lycopene supplementation improves meat quality, antioxidant capacity and skeletal muscle fiber type transformation in finishing pigs. Anim. Nutr. 2022, 8, 256–264. [Google Scholar] [CrossRef]
  21. Zhong, Y.; Yan, Z.; Song, B.; Zheng, C.; Duan, Y.; Kong, X.; Deng, J.; Li, F. Dietary supplementation with betaine or glycine improves the carcass trait, meat quality and lipid metabolism of finishing mini-pigs. Anim. Nutr. 2021, 7, 376–383. [Google Scholar] [CrossRef]
  22. Liu, S.; Du, M.; Tu, Y.; You, W.; Chen, W.; Liu, G.; Li, J.; Wang, J.; Lu, Z.; Wang, T.; et al. Fermented mixed feed alters growth performance, carcass traits, meat quality and muscle fatty acid and amino acid profiles in finishing pigs. Anim. Nutr. 2023, 12, 87–95. [Google Scholar] [CrossRef]
  23. Mykhalko, O.H.; Shostia, A.M.; Usenko, S.O.; Verbelchuk, T.V.; Verbelchuk, S.P.; Koberniuk, V.V.; Lavryniuk, O.O.; Kryvoruchenko, L.V. Fattening and slaughter performance of pigs on liquid and dry feeds. Bull. Sumy Natl. Agrar. Univ. Ser. Livest. 2023, 4, 30–40. [Google Scholar]
  24. Vázquez, N.A.; Barragán, H.B.; Aguilar, N.C.V.; Brenner, E.G.; Dávila, F.S.; Trejo, A.M.; Ramírez, M.C. Effect of wet feeding of finishing pigs on production performance, carcass composition and meat quality. Rev. Mex. Cienc. Pecu. 2021, 12, 370–385. [Google Scholar]
  25. Folch, J.; Lees, M.; Sloane Stanley, G.H. A simple method for the isolation and purification of total lipides from animal tissues. JBC 1957, 226, 497–509. [Google Scholar] [CrossRef]
  26. Boselli, E.; Velazco, V.; Caboni, M.F.; Lercker, G. Pressurized liquid extraction of lipids for the determination of oxysterols in egg-containing food. J. Chromatogr. A 2001, 917, 239–244. [Google Scholar] [CrossRef]
  27. Dolatowska-Żebrowska, K.; Ostrowska-Ligęza, E.; Wirkowska-Wojdyła, M.; Bryś, J.; Górska, A. Characterization of thermal properties of goat milk fat and goat milk chocolate by using DSC, PDSC and TGA methods. J. Therm. Anal. Calorim. 2019, 138, 2769–2779. [Google Scholar] [CrossRef]
  28. ISO 3960; Animal and Vegetable Fats and Oils—Determination of Peroxide Value—Iodometric (Visual) Endpoint Determination. International Organization for Standardization: Geneva, Switzerland, 2017.
  29. Polish Norm: PN-EN ISO: 5509:2001; Oil and Vegetable and Animal Fats. Preparation of Methyl Ester of Fatty Acids. Polish Committee for Standardization: Warsaw Poland, 2001.
  30. Bryś, J.; Flores, L.F.V.; Górska, A.; Wirkowska-Wojdyła, M.; Ostrowska-Ligęza, E.; Bryś, A. Use of GC and PDSC methods to characterize human milk fat substitutes obtained from lard and milk thistle oil mixtures. J. Therm. Anal. Calorim. 2017, 1, 319–327. [Google Scholar] [CrossRef]
  31. Chen, J.; Liu, H. Nutritional indices for assessing fatty acids: A mini-review. Int. J. Mol. Sci. 2020, 21, 5695. [Google Scholar] [CrossRef]
  32. Ulbricht, T.L.V.; Southgate, D.A.T. Coronary heart disease: Seven dietary factors. Lancet 1991, 338, 985–992. [Google Scholar] [CrossRef]
  33. Santos-Silva, J.; Bessa, R.J.B.; Santos-Silva, F. Effect of genotype, feeding system and slaughter weight on the quality of light lambs: II. Fatty acid composition of meat. Livest. Prod. Sci. 2022, 77, 187–194. [Google Scholar] [CrossRef]
  34. Chen, S.; Bobe, G.; Zimmerman, S.; Hammond, E.G.; Luhman, C.M.; Boylston, T.D.; Freeman, A.E.; Beitz, D.C. Physical and sensory properties of dairy products from cows with various milk fatty acid compositions. J. Agric. Food Chem. 2004, 52, 3422–3428. [Google Scholar] [CrossRef]
  35. Jain, S.; Sharma, M.P. Stability of biodiesel and its blends: A review. Renew. Sustain. Energy Rev. 2010, 14, 667–678. [Google Scholar] [CrossRef]
  36. Pereira, G.G.; Marmesat, S.; Barrera-Arellano, D.; Dobarganes, M.C. Evolution of oxidation in soybean oil and its biodiesel under the conditions of the oxidation stability test. Grasas Aceites 2013, 64, 482–488. [Google Scholar]
  37. Frankel, E.N. Lipid oxidation: Mechanisms, products and biological significance. J. Am. Oil Chem. Soc. 1984, 61, 1908–1917. [Google Scholar] [CrossRef]
  38. Knothe, G. Some aspects of biodiesel oxidative stability. Fuel Process. Technol. 2007, 88, 669–677. [Google Scholar] [CrossRef]
  39. Krupska, A.; Olkiewicz, M. Wpływ lokalizacji tłuszczu w tuszy wieprzowej na jego właściwości fizykochemiczne. Postępy Nauk. Technol. Przemysłu Rolno-Spożywczego 2012, 67, 43–52. (In Polish) [Google Scholar]
  40. FAO 2010; Fats and Fatty Acids in Human Nutrition. Report of an Expert Consultation. FAO: Rome, Italy, 2010.
  41. Alonso, V.; Najes, L.M.; Provincial, L.; Guillen, E.; Gil, M.; Roncales, P.; Beltran, J.A. Influence of dietary on pork eating quality. Meat Sci. 2012, 92, 366–373. [Google Scholar] [CrossRef]
  42. Lu, P.; Zhang, L.Y.; Yin, J.D.; Everts, A.K.R.; Li, D.F. Effects of soybean oil and linseed oil on fatty acid compositions of muscle lipids and cooked pork flacour. Meat Sci. 2008, 80, 910–918. [Google Scholar] [CrossRef] [PubMed]
  43. Mir, N.A.; Tyagi, P.K.; Biswas, A.K.; Tyagi, P.K.; Mandal, A.B.; Kumar, F.; Sharma, D.; Biswas, A.; Verma, A.K. Inclusion of flaxseed, broken rice, and distillers dried grains with solubles (DDGS) in broiler chicken ration alters the fatty acid profile, oxidative stability, and other functional properties of meat. Eur. J. Lipid Sci. Technol. 2018, 120, 1700470. [Google Scholar] [CrossRef]
  44. Salvatori, G.; Pantaleo, L.; Di Cesare, C.; Maiorano, G.; Filetti, F.; Oriani, G. Fatty acid composition and cholesterol content of muscles as related to genotype and vitamin E treatment in crossbred lambs. Meat Sci. 2004, 67, 45–55. [Google Scholar] [CrossRef]
  45. Alvarenga, A.; Sousa, R.V.; Parreira, G.G.; Chiarini-Garcia, H.; Almeida, F. Fatty acid profile, oxidativestability of pork lipids and meat quality indicators are not affected by birth weight. Animal 2014, 8, 660–666. [Google Scholar] [CrossRef]
  46. Majdoub-Mathlouthi, L.; Saïd, B.; Kraiem, K. Carcass traits and meat fatty acid composition of Barbarine lambs reared on rangelands or indoors on hay and concentrate. Animal 2015, 9, 2065–2071. [Google Scholar] [CrossRef]
  47. Wójciak, K.M.; Stasiak, D.M.; Ferysiuk, K.; Solska, E. The influence of sonication on the oxidative stability and nutritional value of organic dry-fermented beef. Meat Sci. 2019, 148, 113–119. [Google Scholar] [CrossRef]
  48. Winiarska-Mieczan, A.; Kwiecień, M.; Kwiatkowska, K.; Baranowska-Wójcik, E.; Szwajgier, D.; Zaricka, E. Fatty acid profile, antioxidative status and dietary value of the breast muscle of broiler chickens receivingglycine-Zn chelates. Anim. Prod. Sci. 2020, 60, 1095–1102. [Google Scholar] [CrossRef]
  49. Correa, L.B.; Zanetti, M.A.; Del Claro, G.R.; de Melo, M.P.; Rosa, A.F.; Netto, A.S. Effect of supplementation of two sources and two levels of copper on lipid metabolism in Nellore beef cattle. Meat Sci. 2012, 91, 466–471. [Google Scholar] [CrossRef]
  50. Minelli, G.; D’Ambra, K.; Macchioni, P.; Lo Fiego, D.P. Effect of pig dietary n-6/n-3 polyunsaturated fatty acids ratio and gender on carcass traits, fatty acid profiles, nutritional indices of lipids depots and oxidative stability of meat in medium-heavy pigs. Foods 2023, 12, 4106. [Google Scholar] [CrossRef]
  51. Dal Bosco, A.; Cartoni Mancinelli, A.; Vaudo, G.; Cavallo, M.; Castellini, C.; Mattioli, S. Indexing of fatty acids in poultry meat for its characterization in healthy human nutrition: A comprehensive application of the scientific literature and new proposals. Nutrients 2022, 14, 3110. [Google Scholar] [CrossRef]
  52. Khalili Tilami, S.; Kourimská, L. Assessment of the Nutritional Quality of Plant Lipids Using Atherogenicity and Thrombogenicity Indices. Nutrients 2022, 14, 3795. [Google Scholar] [CrossRef]
  53. Acay, A.; Ulu, M.S.; Ahsen, A.; Ozkececi, G.; Demir, K.; Ozuguz, U.; Yuksel, S.; Acarturk, G. Atherogenic index as a predictor of atherosclerosis in subjects with familial Mediterranean fever. Medicina 2014, 50, 329–333. [Google Scholar] [CrossRef]
  54. Lisa, M.; Velinska, H.; Holcapek, M. Regioisomeric characterization of triacylglycerols using silver-ion HPLC/MS and randomization synthesis of standards. Anal. Chem. 2009, 81, 3903–3910. [Google Scholar] [CrossRef]
  55. Hunter, J.E. Studies on effects of dietary fatty acids as related to their position on triglycerides. Lipids 2001, 36, 655–668. [Google Scholar] [CrossRef] [PubMed]
  56. Segura, J.; Rey, A.I.; Olivares, Á.; Cambero, M.I.; Escudero, R.; Ávila, M.D.R.; Palomo, A.; López-Bote, C. Free-Range Feeding Alters Fatty Acid Composition at the sn-2 Position of Triglycerides and Subcutaneous Fat Physicochemical Properties in Heavy Pigs. Animals 2021, 11, 2802. [Google Scholar] [CrossRef]
  57. Nagy, K.; Sandoz, L.; Destaillats, F.; Schafer, O. Mapping the regioisomeric distribution of fatty acids in triacylglycerols by hybrid mass spectrometry. J. Lipid Res. 2013, 54, 290–305. [Google Scholar] [CrossRef]
  58. productivity and food safety. Recent Adv. Anim. Nutr. 2001, 13, 49–63.
  59. Canibe, J.; Jensen, B.B. Fermented and nonfermented liquid feed to growing pigs: Effects on aspects of gastrointestinal ecology and growth performance. J. Anim. Sci. 2003, 81, 2019–2031. [Google Scholar] [CrossRef]
  60. Lawlor, P.G.; Lynch, P.B.; Gardiner, G.E.; Caffrey, P.J.; O’Doherty, J.V. Effect of liquid feeding weaned pigs on growth performance to harvest. J. Anim. Sci. 2002, 80, 1725–1735. [Google Scholar] [CrossRef]
  61. Benz, J.M.; Tokach, M.D.; Dritz, S.S.; Nelssen, J.L.; DeRouchey, J.M.; Sulabo, R.C.; Goodband, R.D. Effects of choice white grease and soybean oil on growth performance, carcass characteristics, and carcass fat quality of growing-finishing pigs. J. Anim. Sci. 2011, 89, 404–413. [Google Scholar] [CrossRef]
Table 1. Ingredients of liquid and dry feed with nutritional specifications (on dry matter basis).
Table 1. Ingredients of liquid and dry feed with nutritional specifications (on dry matter basis).
IngredientsShare of Ingredients (%)
Grower Feed Finisher Feed
LiquidDryLiquidDry
Wheat41.3038.2538.6235.15
Barley13.7712.6512.8711.75
Wheat food10.0010.0020.0020.00
Soybean meal18.372.0010.05-
Full-fat soy-21.50-12.50
Rapeseed meal5.005.0010.0010.00
Fishmeal2.502.50--
Fat mixture---2.50
Soybean oil5.962.005.362.00
Molasses-3.00-3.00
Minerals and vitamins3.103.103.103.10
Nutritional specification of feed
LiquidDryLiquidDry
DE (MJ/kg)14.7514.7214.1314.22
Lysine (%)1.221.170.940.89
Calcium (%)0.790.900.730.83
Phosphorus (%)0.680.670.590.56
Sodium (%)0.400.420.400.40
DE—digestible energy.
Table 2. Induction time of pork fat oxidation at 100 °C, 120 °C, and 140 °C.
Table 2. Induction time of pork fat oxidation at 100 °C, 120 °C, and 140 °C.
SampleOxidation Induction Time (min)
100 °C120 °C140 °C
GF_L108.46 ± 1.03 d25.24 ± 0.89 e6.06 ± 0.24 c
GF_D108.56 ± 2.07 d25.59 ± 1.13 e5.92 ± 1.28 c
JF_L89.05 ± 0.11 a21.76 ± 1.42 b4.04 ± 0.47 a
JF_D91.65 ± 0.08 b20.70 ± 0.76 a5.29 ± 0.29 b
TSF_L103.70 ± 0.05 c23.63 ± 0.51 d5.92 ± 0.28 c
TSF_D91.49 ± 0.03 b23.01 ± 0.95 c5.31 ± 0.63 b
GF_L—groin fat (liquid feed); GF_D—groin fat (dry feed); JF_L—jowl fat (liquid feed); JF_D—jowl fat (dry feed); TSF_L—trimming shoulder fat (liquid feed); TSF_D—trimming shoulder fat (dry feed). Values represent means ± standard deviations. Data denoted by the same lowercase letters are not statistically different (α = 0.05) in terms of oxidative stability at a certain temperature.
Table 3. Peroxide value of pork fats.
Table 3. Peroxide value of pork fats.
GF_LGF_DJF_LJF_DTSF_LTSF_D
Peroxide value
(meq O2/kg of fat)		1.42 ± 0.39 d1.17 ± 0.24 b,c1.41 ± 0.24 d0.71 ± 0.24 a1.23 ± 0.24 c1.07 ± 0.24 b
GF_L—groin fat (liquid feed); GF_D—groin fat (dry feed); JF_L—jowl fat (liquid feed); JF_D—jowl fat (dry feed); TSF_L—trimming shoulder fat (liquid feed); TSF_D—trimming shoulder fat (dry feed). Data denoted by the same lowercase letters are not statistically different (α = 0.05) in terms of peroxide value.
Table 4. Fatty acid groups and health indexes of pork fats.
Table 4. Fatty acid groups and health indexes of pork fats.
Fatty Acids GroupGF_LGF_DJF_LJF_DTSF_LTSF_D
MUFA (%)46.11 ± 3.03 a46.50 ± 2.84 a 51.97 ± 3.01 c51.16 ± 4.01 b 52.15 ± 4.14 c 46.56 ± 2.38 a
PUFA (%)10.78 ± 1.02 a12.05 ± 1.81 c 11.37 ± 1.98 b12.95 ± 3.03 d10.59 ± 1.14 a13.67 ± 1.89 e
SFA (%)43.11 ± 1.32 f41.45 ± 0.99 e36.66 ± 1.07 b35.89 ± 0.86 a37.26 ± 0.98 c39.77 ± 1.16 d
PUFA/SFA0.250.290.310.360.280.34
n-6/n-39.48 a10.37 bc9.26 ab10.54 bc8.57 a11.01 c
IA0.570.540.450.440.480.50
IT1.351.291.051.011.071.19
HH1.992.032.482.512.392.20
HPI1.751.842.202.272.092.00
GF_L—groin fat (liquid feed); GF_D—groin fat (dry feed); JF_L—jowl fat (liquid feed); JF_D—jowl fat (dry feed); TSF_L—trimming shoulder fat (liquid feed); TSF_D—trimming shoulder fat (dry feed). MUFA—monounsaturated fatty acids; PUFA—polyunsaturated fatty acids; SFA—saturated fatty acids; IA—index of atherogenicity; IT—index of thrombogenicity; HH—hypocholestrolemic/hypercholesterolemic index; HPI—health promoting index. Data denoted by the same lowercase letters are not statistically different (α = 0.05) in terms of fatty acid group content.
Table 5. The distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols (TAG) of pork groin fat and the share of individual acids in the internal position.
Table 5. The distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols (TAG) of pork groin fat and the share of individual acids in the internal position.
Fatty AcidFatty Acid Percentage in TAG (%)Fatty Acid Percentage in Positions (%)Fatty Acid Share in sn-2 Position (%)
sn-2 sn-1,3
GF_L
14:01.97 ± 0.45 a5.060.4385.62
16:024.46 ± 2.03 e61.675.8684.04
18:015.16 ± 1.02 d4.9720.2610.93
18:1 n-942.30 ± 2.87 f15.9955.4612.60
18:2 n-69.17 ± 1.27 b5.4411.0419.77
GF_D
14:01.64 ± 0.38 a4.040.4482.12
16:025.16 ± 1.84 e62.146.6782.32
18:013.83 ± 0.95 d4.3918.5510.58
18:1 n-942.66 ± 2.53 f15.6856.1512.25
18:2 n-610.44 ± 1.36 c5.4912.9217.52
14:0—myristic acid; 16:0—palmitic acid; 18:0—stearic acid; 18:1 n-9—oleic acid; 18:2 n-6—linoleic acid. GF_L—groin fat (liquid feed); GF_D—groin fat (dry feed). Values represent means ± standard deviations. Data denoted by the same lowercase letters are not statistically different (α = 0.05) in terms of individual fatty acid content.
Table 6. The distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols (TAG) of pork jowl fat and the share of individual acids in the internal position.
Table 6. The distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols (TAG) of pork jowl fat and the share of individual acids in the internal position.
Fatty AcidFatty Acid Percentage in TAG (%)Fatty Acid Percentage in Positions (%)Fatty Acid Share in sn-2 Position (%)
sn-2 sn-1,3
JF_L
14:01.63 ± 0.25 b4.290.3087.73
16:022.07 ± 1.48 g57.494.3688.83
18:011.92 ± 0.86 f4.6115.5812.89
18:1 n-947.83 ± 2.49 i20.7161.3914.43
18:2 n-69.62 ± 1.11 c5.9811.4420.72
JF_D
14:01.45 ± 0.71 a3.920.2290.11
16:022.34 ± 1.21 g59.033.9988.08
18:011.24 ± 1.42 e4.1614.7812.34
18:1 n-946.93 ± 3.01 h19.1360.8313.59
18:2 n-611.06 ± 0.82 d6.4813.3519.53
14:0—myristic acid; 16:0—palmitic acid; 18:0—stearic acid; 18:1 n-9—oleic acid; 18:2 n-6—linoleic acid. JF_L—jowl fat (liquid feed); JF_D—jowl fat (dry feed). Values represent means ± standard deviations. Data denoted by the same lowercase letters are not statistically different (α = 0.05) in terms of individual fatty acid content.
Table 7. Distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols (TAG) of trimming shoulder fat and the share of individual acids in the internal position.
Table 7. Distribution of selected fatty acids in the internal (sn-2) and external (sn-1,3) positions of triacylglycerols (TAG) of trimming shoulder fat and the share of individual acids in the internal position.
Fatty AcidFatty Acid Percentage in TAG (%)Fatty Acid Percentage in Positions (%)Fatty Acid Share in sn-2 Position (%)
sn-2 sn-1,3
TSF_L
14:01.83 ± 0.56 b4.690.4085.43
16:022.52 ± 2.07 g56.995.2984.35
18:011.75 ± 0.99 d4.9415.1614.01
18:1 n-948.10 ± 2.96 j20.8361.7214.44
18:2 n-68.91 ± 0.77 c5.6910.5221.29
TSF_D
14:01.50 ± 0.39 a3.860.3285.78
16:024.02 ± 2.69 h59.306.3882.29
18:013.27 ± 1.23 f4.9917.4112.53
18:1 n-942.81 ± 2.64 i18.5354.9514.43
18:2 n-611.87 ± 0.86 e6.8714.3719.29
14:0—myristic acid; 16:0—palmitic acid; 18:0—stearic acid; 18:1 n-9—oleic acid; 18:2 n-6—linoleic acid. TSF_L—trimming shoulder fat (liquid feed); TSF_D—trimming shoulder fat (dry feed). Values represent means ± standard deviations. Data denoted by the same lowercase letters are not statistically different (α = 0.05) in terms of individual fatty acid content.
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Górska, A.; Wirkowska-Wojdyła, M.; Ostrowska-Ligęza, E.; Dasiewicz, K.; Słowiński, M. The Influence of Feeding Type on Quality and Nutritional Characteristics of Pork Fat. Appl. Sci. 2024, 14, 8291. https://doi.org/10.3390/app14188291

AMA Style

Górska A, Wirkowska-Wojdyła M, Ostrowska-Ligęza E, Dasiewicz K, Słowiński M. The Influence of Feeding Type on Quality and Nutritional Characteristics of Pork Fat. Applied Sciences. 2024; 14(18):8291. https://doi.org/10.3390/app14188291

Chicago/Turabian Style

Górska, Agata, Magdalena Wirkowska-Wojdyła, Ewa Ostrowska-Ligęza, Krzysztof Dasiewicz, and Mirosław Słowiński. 2024. "The Influence of Feeding Type on Quality and Nutritional Characteristics of Pork Fat" Applied Sciences 14, no. 18: 8291. https://doi.org/10.3390/app14188291

APA Style

Górska, A., Wirkowska-Wojdyła, M., Ostrowska-Ligęza, E., Dasiewicz, K., & Słowiński, M. (2024). The Influence of Feeding Type on Quality and Nutritional Characteristics of Pork Fat. Applied Sciences, 14(18), 8291. https://doi.org/10.3390/app14188291

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