Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged. Received: 16 March 1998 / Revised version: 17 June 1998     

Fatty Acids of Neutral and Phospholipids, Rancidity Scores and TBA Values as Influenced by Packaging and Storage

The fatty acid (FA) of neutral lipids (NL) and phospholipids (PL) and this composition's relationship to rancidity score and TBA values of cooked beef patties, during frozen storage at times up to 4½ months under vacuum and nonpackaged conditions were studied. The predominant FA in the NL was C_18:1 (46.0%), followed by C_16:0 at 29.2%. However, the PL fraction gave a more balanced distribution of FA. In the neutral lipid fractions, reduction in the C_16:1 and C_18:2 fatty acids made significant contributions to increased rancidity scores and TBA values but in the phospholipid fraction, changes in the C_18:3 and C_20:4 were of greatest importance. After 3 months of frozen storage a regression model containing the neutral lipid fatty acids C_18:1 and C_18:2 and the phospholipid fatty acids C_18:3 and C_20:4 accounted for 88% and 85% of the variation in rancidity score and TBA value.     

Lipid content and fatty acid composition of green algae Scenedesmus obliquus grown in a constant cell density apparatus

The lipids of alga Scenedesmus obliquus grown under controlled conditions were separated and fractionated by column and thin-layer chromatography, and fatty acid composition of each lipid component was studied by gas-liquid chromatography (GLC). Total lipids were 11.17%, and neutral lipid, glycolipid and phospholipid fractions were 7.24%, 2.45% and 1.48% on a dry weight basis, respectively. The major neutral lipids were diglycerides, triglycerides, free sterols, hydrocarbons and sterol esters. The glycolipids were: monogalactosyl diglyceride, digalactosyl diglyceride, esterified sterol glycoside, and sterol glycoside. The phospholipids included: phosphatidyl choline, phosphatidyl glycerol and phosphatidyl ethanolamine. Fourteen fatty acids were identified in the four lipid fractions by GLC. The main fatty acids were C18:2, C16:0, C18:3(alpha), C18:1, C16:3, C16:1, and C16:4. Total unsaturated fatty acid and essential fatty acid compositions of the total algal lipids were 80% and 38%, respectively.     

Fatty acid composition of the total, neutral and phospholipids of pond-raised Brazilian Piaractus mesopotamicus

Seven sample lots of farmed Piaractus mesopotamicus , fed a set diet, collected at different times during the year were analysed. The total lipids (11 ± 3% fresh weight, muscle) consisted of 94% neutral lipids and 5% phospholipids. Sixty-seven fatty acids and dimethylacetals were detected in the total lipids, the principal acids being 18:1ω9±ω7 (41.0 ± 1.7%), 16:0 (24.2 ± 1.2%), 18.2ω6 (9.1 ω 0.5%), 16:1ω7 (8.9 ± 0.7%), 18:0 (7.7 ± 0.5%) and 14:0 (3.2 ± 0.5%). The neutral lipids exhibited a similar profile. The phospholipids had a higher proportion of polyunsaturated fatty acids, the major components being 18:1ω6 (9.1 ± 0.7%) (17.5 ± 1.8%), 16:0 (16.7 ± 2.0%), 20:4ω6 (11.6 ± 1.3%), 22:6ω3 (11.0 ± 1.3%), 18:2ω6 (9.1 ± 0.7%), 18:0 (8.9 ± 1.1%), 22:5ω (5.8 ± 0.7%). No definite trend was seen in relation to season (water temperature, 7–26°C). The fish samples analysed were poor in ω3 fatty acids, which appeared to reflect the low ω3 fatty acid content of the diet.     

Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged.     

Changes in lipid composition and fatty acid profile of Nham,a Thai fermented pork sausage,during fermentation

Changes in lipid composition and fatty acid profile of Nham during fermentation were investigated. Total lipids of Nham were in the range 2–3%. The extracted lipid of initial Nham mix consisted mainly of triglycerides (TG), accounting for more than 75% of the total lipid, followed by phospholipids (PL) and a trace amount of diglycerides (DG) and free fatty acid (FFA). During fermentation, TG, DG and PL decreased with a concomitant increase in FFA, indicating lipolysis of Nham lipids during fermentation. Changes in fatty acids of the total lipids, non-polar and polar lipid fractions were observed during fermentation. In both total and non-polar lipid fractions, the major fatty acids found in a descending order were oleic (C18:1), linoleic (C18:2) and palmitic (C16:0) acids, which together accounted for 90% of the total fatty acids. Increases in fatty acid contents in both total and non-polar lipid fractions, were observed with a corresponding decrease in the quantity of fatty acids of phospholipids. As the fermentation proceeded, peroxide value generally increased while TBARS values decreased. Overall, lipid oxidation in Nham occurred during fermentation but did not cause the objectionable odour and taste in any Nham tested.     

Changes in phospholipids of buffalo meat during processing and storage

Effect of broiling and pressure cooking as well as alterations during refrigerated (4°C) and frozen (-10°C) storage on the phospholipids of adult male buffalo muscles viz. Triceps brachii (TB), Longissimus dorsi (LD) and Biceps femoris (BF), i.e. from three different locations were studied. Muscles differed significatly in their total lipid and phospholipid content. Cooking methods significantly altered the total phospholipid content and its fractions. Storage period did not show any significant effect on total phospholipids during refrigerated and frozen storage, whereas certain phospholipid classes viz. lysophosphatidyl choline and lysophosphatidyl ethanolamine + sphingomyelin increased significantly and major phospholipid classes viz. phosphatidyl choline and phosphatidyl ethanolamine decreased significantly. The changes in phospholipid classes were similar both in refrigerated and frozen samples but relatively more pronounced in the former. Palmitic, stearic, oleic and linoleic acids were the four predominant fatty acids in the phospholipids of buffalo meat. The effects associated with the location of muscles were evident. Differences in fatty acid composition of individual muscles in response to heat processing were observed. Heat processing significantly increased the total saturates in TB and LD muscles while it decreased in BF. The total monounsaturated and total polyunsaturated fatty acids of phospholipids decreased during refrigerated and frozen storage indicated by a significant decreass in oleic, linoleic and arachidonic acids.     

Seasonal variations in lipid composition of spanish wild rabbit (Oryctolagus cuniculus) meat

Four batches of wild rabbit (Oryctolagus cuniculus: winter, spring, summer and autumn) were caught at the end of the respective season of the year. A study of the meat chemical composition of these animals was carried out. The classes and amounts of total, apolar and polar lipid fractions, and their fatty acids, have been extensively studied. The total, apolar and polar lipid contents from the muscle of the four batches ranged from 37 to 14, 30-1 to 8–4 and 9–0 to 4–8 g kg^?1 FW respectively. Triglycerides accounted for more than 59% of the apolar lipids, and phosphatidylcholine and phosphatidyl-ethanolamine were the major phospholipids (>44% and >35% of total phospholipids, respectively). Almost always, 16:0, 18:0, 18:1 and 18:2 were the more abundant fatty acids of the total lipid fraction. Many seasonal differences may be observed in the fatty acid composition of total and apolar lipid fractions which are obviously related to the kinds of feed available in each season. One of the most significant differences is in 18:1 concentration. This fatty acid accounted for more than 50% in the apolar lipids from rabbits caught in autumn whereas the same fatty acid never reached 30% in other seasons. On the contrary, 18:2 and 20:0 showed a lower concentration in the autumn batch by comparison with those of the other seasons.     

Lipid and fatty acid composition of rabbit meat: Part 2.-Phospholipids

The phospholipid contents (and their fatty acid composition) of the meat of two rabbit breeds (New Zealand white and the commercial hybrid HYLA) fed with two commercial diets of different protein and fibre contents, have been determined. The phospholipid contents in the meat of both rabbit breeds ranged from 9% to 19% total lipid. In this fraction seven different phospholipid classes were detected but phosphatidylcholine (PC) and phosphatididylethanolamine (PE) had average percentages of 50 and 20 of the total phospholipids. The major fatty acids of both phosphatidylcholine and phosphatidylethanolamine were C-16:0, C-18:0, C-18:1 and C-18:2, these together representing more than 70% of the total fatty acids. In general, the PC had an higher saturated fatty acid content than PE, which had a lower percentage of C-16:0 but higher C-20:4. Although differences in the fatty acid composition of the phospholipid fractions of the rabbit meat were observed, the only clear influences of age, sex, breed, and/or feeding were found with the C-16:0, C-18:0 and C-18:2 fatty acids.     

Phospholipids of marine origin. VI. The octopus (Octopus vulgaris)

The composition of octopus (Octopus vulgaris) phospholipids was determined by analysis of hydrolytic breakdown products and by chromatography on silicic acid. The most remarkable feature of octopus phospholipids was the high content (13%) of ceramide aminoethylphosphonic acid. In addition the phospholipids contained phosphatidylcholine (42%), phosphatidylethanolamine (30%), phosphatidylserine (5%), phosphatidylinositol (4%) and sphingomyelin (3%). The fatty acid distribution of the phospholipids and the non-phosphorylated lipids was determined by gas chromatography. The major saturated fatty acids in the phospholipids and non-phosphorylated lipids were 16:0 (24 and 23%, respectively) and 18:0 (10 and 15%, respectively). The major highly unsaturated fatty acids in phospholipids and non-phosphorylated lipids were 20:5 (18 and 7%, respectively) and 22:6 (23 and 9% respectively).     

Changes in milk fat phospholipids during lactation

Changes in lipid composition were studied in milk obtained on postpartum d 3 (colostrum), 7, 42, and 180 from 12 Holstein cows. Triglycerides, 96 to 97% of total lipids, were relatively constant during lactation. Phospholipids and cholesterol declined with advancing lactation. Concentrations of the fatty acids synthesized within the mammary gland, C10:0 to C16:0, increased about 50% from 7 to 42 d of lactation. During this period, compensatory decreases were observed in C18:1. The phospholipids were separated into five major classes: sphingomyelin, phosphatidyl choline, serine, inositol, and ethanolamine for fatty acid analysis. The changes that occurred in milk total fatty acids were reflected in phosphatidyl phospholipid fatty acid composition: an increase in medium-chain fatty acids and a decrease in polyunsaturated fatty acids of 18, 20, and 22 carbon atom chain length as lactation progressed. These changes are consistent with the theory that milk phospholipids are synthesized de novo entirely in the mammary gland.     

Lipid and fatty acid composition of rabbit meat: Part 1.-Apolar fraction

The apolar lipid contents and the fatty acid composition of meat from two rabbit breeds (New Zealand white and commercial hybrid HYLA) fed two commercial diets of different protein and crude fibre levels have been studied. The total and apolar lipid content of meat from both rabbit breeds ranged from 4·9 to 10·5% (wet weight). The individual lipid classes of the apolar fraction are described. Triglycerides accounted for more than 80% of total apolar lipids. The fat from rabbit meat is comparatively richer in palmitic acid (about 40% being always the major fatty acid), in linoleic acid and in myristic acid and poorer in stearic acid than other meats. Although differences in the fatty acid compositions of meat were observed, only clear influences of age, sex, breed, and/or feeding on the fatty acids C-16:0, C-18:0 and C-18:2 of total and apolar lipids were found.     

Effects of dietary α-linolenic acid on the fatty acid composition, storage stability and sensory characteristics of pork loin

Effects of dietary α-linolenic acid on the fatty acid composition, storage stability and sensory characteristics of cooked pork were studied. Dietary α-linolenic acid (LNA) significantly (p < 0.05) increased the proportion of n−3 fatty acids and the degree of unsaturation in the neutral lipids and phospholipids. The increases in n−3 fatty acids were observed in the total lipids, triglycerides, phosphatidylethanolamine and phosphatidylcholine, and mainly consisted of C18:3n3, C20:5n3 and/or C22:5n3.The thiobarbituric acid reactive substances (TBARS) values (mg malondialdehyde per kg meat) of cooked vacuum packaged loins remained below 1.5, but in loose packaged loins TBARS values increased more than 3 times those of 0 time values during 2-day storage at 4 °C. The TBARS values of loins after LNA-enrichment were significantly higher than those of the control in both vacuum and loose packaging, and the increase of unsaturation in fatty acids had a strong prooxidant effect. The increase in dietary LNA enrichment increased oxidation (TBARS values) and had a detrimental effect on the acceptability of cooked pork loins held for 2 days in loose packaging.     

烹饪方式对凡纳滨对虾（Penaeus vannamei）脂质及挥发性物质的影响

为探究风味差异的形成机制,以凡纳滨对虾为研究对象,研究蒸制和微波加热2种烹饪方式对脂质组成、脂质氧化水解程度及挥发性物质的影响。结果表明,凡纳滨对虾在烹饪后总脂和脂质组成(磷脂、甘油三脂及游离脂肪酸)含量均显著降低(P<0.05)。蒸制和微波加热的对虾,其脂质组成也有所差别,与蒸制相比,微波加热虾肉中的磷脂含量偏高,而游离脂肪酸含量偏低。鲜虾烹饪后饱和脂肪酸含量显著下降,不饱和脂肪酸含量显著上升(P<0.05),可能与磷脂的水解有关。蒸制和微波加热加速了脂质的氧化水解,酸价和硫代巴比妥酸反应物值均显著升高(P<0.05)。电子鼻分析结果显示鲜虾、蒸制和微波加热虾肉的气味特征有明显不同,且微波加热气味变化更大。采用气相色谱-离子迁移谱从虾肉中分离鉴定出25种挥发性物质,其中2,3-戊二酮、2-丁酮、2-甲基丁醛、己醛、1-辛烯-3-酮和戊醛等是熟虾肉主要的风味物质,且在微波加热的样品中含量更高。Pearson相关性分析结果表明,脂质的氧化水解对风味形成有重要贡献,游离脂肪酸中的C_14:0、C_15:0、C_16:1     

LIPIDS AND FATTY ACIDS OF WILD EDIBLE MUSHROOMS OF THE GENUS BOLETUS

Fifteen species of wild edible mushrooms belonging to the genus Boletus (phylum Basidiomycota) were examined by high-performance thin-layer chromatographic (HP-TLC) analysis and gas chromatography–mass spectrometry (GC-MS) analysis for the presence of neutral, glyco-, phospholipids, betaine lipids and fatty acids. The most abundant fatty acids were oleic acid (9-18:1, 15–42%), linoleic acid (9,12-18:2, 38–58%) and palmitic acid (16:0, 7–17%), but a great variation of the ester composition from one to another one was found. A comparison of neutral lipids, glycolipids, polar lipids and fatty acid composition of four species was done. Diacylglyceryltrimethylhomoserine and phosphatidylcholine were found as major components among polar lipids. Chemical constituents were characterized by GC-MS, HP-TLC and other chemical methods. Biologic activity of some isolated compounds from the genus Boletus is also discussed.

PRACTICAL APPLICATIONS

Mushrooms are important wildlife food in the Mediterranean countries. The lipids of mushrooms, sampled from the Upper Galilee, Golan Heights and Mount Carmel areas, and also from the forest around Jerusalem, were examined. The benefits of including fatty acids in the diets of humans are well documented. Fatty acids play a major role in the functioning of the immune system and the maintenance of all hormonal systems in the body. Mushrooms from the genus Boletus are an excellent source of both fatty acids and neutral and polar lipids. Boletus mushrooms are one of the most popular treats in Israeli houses.     

银离子固相萃取法测定反刍动物反式脂肪酸异构体含量

利用氨丙基硅胶柱从反刍动物脂质中分离甘油三酯和磷脂,以氢化大豆油作为对照。采用银离子固相萃取柱分离甘油三酯和磷脂中反式脂肪酸异构体,气相色谱仪测定反式脂肪酸含量。结果显示:在3种反刍动物脂质中检测出trans-16:1,trans-18:1和trans18:2 3类反式脂肪酸,其中总脂质和甘油三酯总反式脂肪酸含量最高的是羊肉脂质,分别占总脂肪酸的7.64%和7.38%;磷脂中总反式脂肪酸最高的是牛肉脂质,占总脂肪酸的5.89%。银离子固相萃取柱能够从反刍动物脂质中分离出9种trans18:1异构体,其中含量最高的是11t18:1,分别为总脂质、甘油三酯和磷脂trans18:1的30.33%~39.03%,38.08%~45.09%和27.10%~44.47%。通过PLS-DA分析3种反刍动物反式脂肪酸异构体之间的差异,羊肉脂质中甘油三酯中的9t18:1和磷脂中的11t18:1含量均显著高于牛奶脂质和牛肉脂质(P<0.05);牛肉脂质中磷脂中的9t18:1和15t18:1含量均显著高于牛奶脂质和羊肉脂质(P<0.05);牛奶脂质磷脂中的12t18:1和16t18:1的含量均显著高于牛肉脂质和羊肉脂质(P<0.05)。反刍动物磷脂中的反式脂肪酸异构体有较大差异。     

Stability of lipids and fatty acids in frozen and gamma irradiated Patagonian toothfish (Dissostichus eleginoides) from the Southwestern Atlantic

Patagonian toothfish were captured in the Southwestern Atlantic Ocean (FAO Zone N° 41). The fatty acid profile of total lipids and the triacylglycerol and phospholipid content of control and irradiated samples (1 and 5 kGy) stored at −18 °C were analyzed at 0 and 293 days post irradiation. The fatty acids are mainly monounsaturated acids (47 g/100 g total fatty acids), the most abundant one being oleic acid (18:1 n-9). This is followed in order of abundance by saturated fatty acids (26 g/100 g total fatty acids), consisting mainly of palmitic acid (16:0). Polyunsaturated fatty acids were less abundant (17 g/100 g total fatty acids) and consisted mainly of eicosapentaeonic (20:5 n-3) and docosahexaenoic (22:6 n-3) acids. Triacylglycerol content was 563.07 mg/mL oil, whereas phospholipids were 11.21 mg/mL oil. Gamma irradiation did not significantly affect the fatty acid profile or triacylglycerol and phospholipid content of P. toothfish stored for 293 days at −18 °C. The results suggest that the species exhibits a marked stability when subjected to irradiation and prolonged storage in the frozen state.     

Lipid changes during germination of fenugreek seeds (Trigonella foenum-graecum)

Fenugreek seeds were germinated in the dark for 96 h. Total lipid extracts were prepared and found to decrease on germination. Ultraviolet, visible and infra-red spectra were estimated for the lipids of ungerminated and germinated fenugreek seeds. Free fatty acids (FFA), total chlorophyll and carotenoid pigments increased greatly after germination. On the other hand, triglycerides, phospholipids and unsaponifiable matter decreased. Determination of individual phospholipids showed that phosphatidylcholine (PC) and phosphatidylethanolamine (PE) constitute about 67% of the total phospholipids of ungerminated seeds. After germination PC and PE decreased whilst phosphatidic acid (PA) and phosphoglyceric acid (PG)—degradation products of phospholipids by phospholipases—increased. The fatty acid composition showed that the total unsaturated fatty acids decreased whilst the total saturated fatty acids increased on germination. The fatty acids 18:2 and 18:3 were the most abundant acids in the lipids of the ungerminated seeds and fell after germination from 41·2% to 31·8% and 23·2% to 14.4%, respectively. The minor constituent fatty acids 20:0, 22:0 and 20:1 increased by 3·3-, 3·0- and 7·8-fold, respectively after germination.     

Effect of fermentation,processing and storage on lipid composition of sauerkraut

The changes in lipid composition and fatty acid distribution of sauerkraut during fermentation, canning, processing and storage were investigated organoleptically and chemically. Treatments were significant throughout the experiment. pH, lactic acid, and moisture content did not reveal any substantial changes. Total lipids, neutral lipids, and glycolipids increased, whereas phospholipids were unaltered during fermentation and processing. Quantitative changes in nonpolar and polar lipids during storage were in opposite directions, and net lipid content did not change. The changes in fatty acid composition were primarily in the distribution of palmitic, stearic, oleic, linoleic and linolenic acids during fermentation, processing and storage. Total lipids did not relate to organoleptic evaluation. However, polar lipids, specifically phospholipids, were directly related to storage stability and increased amounts of general acceptability. The formation of phospholipids may be catalysed by a reaction between tin from the cans and polar lipids at the expense of neutral lipids.     

Role of triglycerides and phospholipids on development of rancidity in model meat systems during frozen storage

The effect of triglycerides, phospholipids and total lipids on development of rancidity during frozen storage at ?18° C for 8 months was studied using lipid-free muscle fibres in combination with added triglycerides, phospholipids and total lipids. Results showed that added phospholipids greatly increased TBA values. Oxidation took place in two stages. Phospholipids were the first to oxidise, with their rate of oxidation decreasing with time. Oxidation of the triglycerides began only after a prolonged induction period. Results demonstrated that both triglycerides and phospholipids contribute to development of rancidity, although phospholipids make the greatest contribution. The influence of triglycerides on the development of rancidity was shown to depend upon the degree of unsaturation and the length of time in frozen storage. The relationship between oxidation of the polyunsaturated fatty acids (PUFAS) of the phospholipids and development of rancidity was confirmed.