LIPID COMPOSITION OF PORK MUSCLE AS AFFECTED BY SIRE GENETIC TYPE

Lipid composition of the muscle Semimembranosus was analyzed in the offspring of five different sire genetic types: Danish Duroc (DU), Dutch Large White (LW_D), English Large White (LW_E), Belgian Landrace × Landrace (EL × LR) and Belgian Landrace (BL), all of them mated to Landrace × Large White sows. The animals sired by DU boars showed the highest intramuscular fat, nonpolar lipid and free fatty acid contents. Fatty acid composition of triglycerides was little affected by genetic type. However, the fatty acid composition of phospholipids was strongly affected, the highest monounsaturated fatty acid (MUFA) and the lowest polyunsaturated fatty acid (PUFA) percentages being found in the animals sired by BL × LR boars. On the other hand, the animals sired by BL boars, which showed the highest phospholipid content, showed the highest PUFA percentage.     

WATER ACTIVITY AND TEMPERATURE EFFECTS ON LIPID OXIDATION IN MUSCLE FIBERS

The effects of temperature and water activity on lipid oxidation in washed muscle fibers stored at water activities ranging from 0.96 to 0.70 and at various temperatures were studied. Fluorescence measurements at −20C, revealed no significant change over 50 days at any water activity. At 4C and 20C, there was an initial increase in fluorescence for all samples over the first few days, then a more rapid decrease with no further change up to 40 days. At 80C, no change in fluorescence was seen over a 100-min period. Rancidity did develop in some samples but was not always detected by fluorescence. Through use of oxygen uptake as a measure of lipid oxidation, it was possible to see differences between samples at different water activities and temperatures. However, the limited amount of oxygen and the temperature limitation of the oxygen electrode prohibit studies over extended time periods and at high temperatures (> 50C).     

LIPID COMPOSITION OF BOB AND SPECIAL-FED VEAL

Four muscles were studied to determine the lipid composition of Bob (BV) and Special-fed (SFV) veal. No differences existed for proximate analysis values of muscles from carcasses of different weight classes (P> 0.05). Muscles from SFV were higher in fat (P < 0.05) and generally displayed more protein and less moisture than the BV. BV contained more cholesterol than SFV (P< 0.001); however, there was no difference among the 4 muscles for cholesterol content (P > 0.05). SFV contained more 14:0 and 18:2, and less 16:1, 18:0 and 18:1 fatty acids than BV (P< 0.05). Fatty acid composition on a g per 100 g tissue weight basis was higher in 14:0, 16:0, 17:0, 18:2 and 20:4 (P< 0.05) for SFV. The longissimus contained more 14:0, 16:0, 18:0 and 18:1 than the other muscles studied (P< 0.05). The results indicate that veal is an appropriate low-fat muscle food which meets modern dietary guidelines concerning fat consumption.     

ENZYMIC LIPID PEROXIDATION IN BEEF MUSCLE MICROSOMES AS AFFECTED BY ELECTRICAL STIMULATION AND POSTMORTEM MUSCLE EXCISION TIME

Left sides of 10 beef carcasses were electrically stimulated at I h postmortem; right sides were not stimulated. Longissimus dorsi (LD) and trapezius (TP) muscles were removed from stimulated and nonstimulated sides after 1.5 and 24 h of chilling (0–2°C). Microsomal lipid peroxidizing activity (the amount of malonalde-hyde produced per mg of microsomal protein) was not affected by electrical stimulation, was higher for muscles removed after 24 h chilling than for those removed after 1.5 h chilling, and was higher for TP than for LD muscles. Differences observed in lipid peroxidizing activity could not be explained readily by microsomal fatty acid compositions.     

PROXIMATE AND LIPID COMPOSITION OF NONDAIRY IMITATION MILK IN COMPARISON WITH MILK

Comparative studies of milk and nondairy imitation milks showed that their proximate compositions were similar. Qualitative and quantitative studies revealed that saturated fatty acids were abundant in milk, while unsaturated fatty acids (C _18:1 and C _18:2 ) were predominant in nondairy imitation milks. This was confirmed by the higher melting points of the fat fractions of milk compared with those of nondairy imitation milks. Finally, lipid peroxidation level of samples were low as determined by the 2-thiobarbituric acid test.     

PHOSPHOLIPIDS AS RELATED TO TOTAL LIPID AND DNA IN LIGHT AND DARK PORTIONS OF PORCINE SEMITENDINOSUS MUSCLE

SUMMARY –Phospholipids of the light and dark tissue of porcine semitendinosus muscle were studied in relation to total lipid and DNA concentrations. The dark portion contained more moisture and less lipid than the light. Phospholipid concentration was higher in dark than light tissue whether expressed in terms of tissue weight or as percent of total lipid. No difference was found in relative concentrations of lecithin, cephalin or sphingomyelin in the two portions. DNA content was higher in the dark tissue than in the light. Expression of phospholipid content in terms of DNA resulted in a reversal of the apparent difference between the two muscle portions: the phospholipid-DNA ratio was higher for light than for dark tissue.     

LIPID CONTENT AND FATTY ACID COMPOSITION IN THE GREEN-LIPPED MUSSEL PERNA VIRIDIS (L.)

The lipid content and fatty acid profile in soft tissue of the green-lipped mussel Perna viridis, a widely distributed tropical and subtropical bivalve species, were investigated. The total and neutral lipid contents were 6.17 ± 0.71 and 2.71 ± 0.42 mg per 100 mg dw, respectively. The content of docosahexaenoic acid (DHA, C22:6n-3) was 24.38 ± 2.50 mg/g dw whereas eicosapentaenoic acid (EPA, C20:5n-3) was present at 12.29 ± 2.12 mg/g dw. These two fatty acids were also at the top high percentage among all the fatty acids, with 38.06 ± 0.86% and 17.89 ± 1.24% (w/w) in total lipids and 34.64 ± 2.74% and 20.33 ± 1.05% (w/w) in neutral lipids, respectively. Therefore, green-lipped mussel is a rich source of DHA and EPA, the two n-3 polyunsaturated fatty acids that are beneficial to human health and nutrition.     

LIPID PEROXIDATION IN SARCOPLASMIC RETICULUM AND MUSCLE OF TILAPIA IS INHIBITED BY DIETARY VITAMIN E SUPPLEMENTATION

Lipid peroxidation was analyzed in muscle and sarcoplasmic reticulum (SR) of hybrid tilapia fed diets containing 0, 100, 200, and 300 IU vitamin E/kg for 8 months. Iron-catalyzed NADH-dependent lipid peroxidation in SR of tilapia fed diet containing no supplemented vitamin E was significantly greater than that of fish fed other diets (P < 0.05). No difference was observed in SR lipid peroxidation between fish fed 200 and 300 IU vitamin E/kg. Thiobarbituric acid reactive substances (TBARS) produced in muscle stored at either 4C or -40C for 7 days and 8 weeks, respectively, increased when storage time increased. When muscle TBARS were plotted against storage time, the lag phases were longer for fish fed high vitamin E (≥ 200 IU/kg) diets than those from fish fed low vitamin E diets.     

LIPID COMPOSITION OF AEROBICALLY AND ANAEROBICALLY PROPAGATED BREWER'S BOTTOM YEAST

Aerobically grown pitching yeast is very rich in unsaturated fatty acids and sterol esters compared to traditional, anaerobic yeast. The principal fatty acids in aerobic yeast cells are unsaturated palmitoleic and oleic acids, whereas in anaerobic cells saturated palmitic acid predominates. The difference in fatty acid distribution between aerobic and anaerobic cells is most marked in the sterol esters. The fatty acids of phospho-lipids are more stable, although remarkable differences are observed. The sterols of aerobic cells are almost entirely in esterified form and zymosterol is the principal sterol. During the first hours of fermentation a rapid synthesis of palmitoleic acid is observed when anaerobic yeast is used for pitching and the wort is aerated. The synthesis of oleic acid requires more oxygen and time than is available under normal brewing conditions. When aerobic pitching yeast is used no more unsaturated fatty acids are synthesised and the lipid stores of pitching yeast are distributed among the daughter cells. The decrease in acetate ester production by aerobic pitching yeast is concluded to be due to a decrease in acetyl CoA synthesis, which may be caused by the high proportion of unsaturated fatty acids in membrane lipids.