EFFECT OF CYTOSOL ON LIPID PEROXIDATION IN FLOUNDER SARCOPLASMIC RETICULUM

Studies were carried out to determine the effects of cytosol on sarcoplasmic reticulum lipid peroxidation. Upon addition of unfractionated cytosol to the lipid peroxidation system, inhibition was observed. Fractionation revealed that both the low molecular weight (LMW) cytosol (<10,000 MW) and high molecular weight (HMW) cytosol (>6,000–8,000 MW) fractions inhibited lipid peroxidation. It is suggested that either inorganic phosphate compounds or nucleotides may be responsible for the LMW cytosol's inhibitory characteristics. Addition of the HMW cytosol fraction to the system necessitated the presence of additional adenosine 5′-diphosphate (ADP) for optimal activity. ADP bound to the HMW cytosol fraction may be incapable of chelating the iron and preventing its precipitation as the ferric hydroxide.     

OXIDATION OF LIPIDS IN SARCOPLASMIC RETICULUM OF MUSCLES FROM PASTURE- AND GRAIN-FED CATTLE WITH OR WITHOUT VITAMIN E SUPPLEMENTATION

The effect of different α-tocopherol contents in sarcoplasmic reticulum (SR) membranes on lipid oxidation was investigated. Muscle membranes contain high contents of polyunsaturated fatty acids that are very susceptible to oxidation during chilled or frozen storage. SR was prepared from M. longissimus dorsi, M. semimembranosus and M. gluteus medius muscles of pasture- and grain-fed steers supplemented with vitamin E (0, 500 or 2500 IU α-tocopheryl acetate) for 105 -132 days. Vitamin E supplementation increased the α-tocopherol concentration in SR of grain-fed cattle but did not change that of pasture-fed cattle. SR from pasture-fed beef had more linolenic and less linoleic acid than that of grain-fed meat and, compared with the other treatment groups, SR of control grain-fed cattle was significantly more prone to lipid oxidation, corresponding with its lower α-tocopherol content. Thus, α-tocopherol content appears to play a major role in determining the extent of lipid oxidation in muscle membranes, especially in those from pasture-fed beef that contained more polyunsaturated fatty acids.     

EFFECT OF POSTMORTEM AGE OF FLOUNDER SARCOPLASMIC RETICULUM ON INHIBITION OF ENZYMIC LIPID PEROXIDATION BY CYTOSOL

On aging in situ or in vitro, flounder muscle sarcoplasmic reticulum became less sensitive to inhibition by the soluble fraction of the muscle tissue. This decrease in sensitivity to inhibition was the result of the change in balance between the response to a dialyzable inhibitor and a large molecular weight activator found in the soluble fraction. With aging, the sarcoplasmic reticulum became more sensitive to the stimulatory activity of the large molecular weight activator.     

SOLUBLE AND BOUND IRON EQUALLY EFFECT LIPID OXIDATION OF SARCOPLASMIC RETICULUM

ABSTRACT Iron over the range of 25–250 μM FeCl3 in the presence of ADP and histidine bound in increasing amounts to fish sarcoplasmic reticulum. Binding of iron was not reversed either by washing in water or after oxidation of the membrane lipid. There was no difference in the rate of lipid oxidation measured as TBA-reactive substances catalyzed by iron bound to the sarcoplasmic reticulum or by iron in the soluble phase of the assay medium when expressed on an iron basis. These results imply that for either bound or soluble iron there is a common rate-determining step. In addition, soluble and bound iron were similar with respect to both inhibition by thiourea of their ability to catalyze lipid oxidation and their generation of hydroxyl free radicals measured by production of methane sulfinic acid from dimethyl sulfoxide in the presence of hypoxanthine and xanthine oxidase.     

VITAMIN E SUPPLEMENTATION EFFECTS ON COLOR AND LIPID STABILITY OF WHOLE AND GROUND LAMB

Crossbred wethers averaging 44.1 kg were fed a diet supplemented with 2000 IU α-tocopheryl acetate/day for 49 days. The controls received the same diet without supplement. Muscles from lambs supplemented with vitamin E contained higher concentrations of a-tocopherol than the controls (P<0.05). There were no differences between control and supplemented animals for myoglobin stabiliry of two muscle slices stored at 4C (P>0.05). Ground semimembranosus (SM)from supplemented animals exhibited higher "a" values and lower Hue angle values (P < 0.05) than meat from control animals at 6 days of storage and longer indicating enhanced color stability due to vitamin E. Vitamin E supplementation decreased lipid oxidation of ground SM at 3, 6, 9, and 12 days of storage at 4C (P < 0.05) and it partially stabilized color of ground lamb. Color stability of whole lamb slices was not affected by vitamin E supplementation.     

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.     

EFFECT OF POSTMORTEM AGING ON CHICKEN BREAST MUSCLE SARCOPLASMIC RETICULUM

FSR (fragmented sarcoplasmic reticulum) isolated from chicken breast muscle (Pectoralis major) at 0 hr, 48 hr and 7 day postmortem was purified using linear density gradient centrifugation. The Ca⁺⁺accumulating ability of the FSR was found to increase with postmortem aging. No loss in ATPase activity was noted nor was any significant change observed in the SDS-gel electrophoresis patterns of the proteins with postmortem aging. The FSR from the aged muscle contained a higher proportion of phospholipids These studies indicate that the Ca⁺⁺ sequestering properties of sarcoplasmic reticulum from chicken breast muscle are not impaired during postmortem aging.     

STORAGE STABILITY OF PORK FROM BERKSHIRE AND HAMPSHIRE SIRED PIGS FOLLOWING DIETARY SUPPLEMENTATION WITH VITAMIN E

Effects of vitamin E supplementation on pork quality of two genotypes were evaluated using 240 pigs (initial body weight was 87 0.35 kg). Berkshire or Hampshire sired pigs were fed either 12, 55, 99, 174, and 351 IU/kg of vitamin E for 6 weeks prior to slaughter. Loins from Hampshire sired pigs had increased (P < 0.001) levels of drip loss, were paler, more red, and more yellow than loins from Berkshire sired pigs following refrigerated display storage for up to 8 days or vacuum packaged storage for up to 55 days. Vitamin E supplementation did not improve fresh pork quality in either genotype. However, results indicate that vitamin E supplementation improved oxidative stability of pork chops during refrigerated display storage and this effect was more pronounced in the leaner Hampshire sired pigs. Therefore, vitamin E supplementation could be strategically applied to improve storage stability in select genotypes.     

EFFECT OF DIETARY VITAMIN E AND SURFACE APPLICATION OF OLEORESIN ROSEMARY ON IRON/ASCORBATE-STIMULATED LIPID OXIDATION IN MUSCLE TISSUE AND MICROSOMES FROM RAINBOW TROUT (Oncorhynchus mykiss)

The effect of dietary α-tocopheryl acetate and surface application of oleoresin rosemary on iron/ascorbate-induced lipid oxidation in rainbow trout ( Oncorhynchus mykiss ) muscle and microsomes was investigated. The 2-thiobarbituric acid-reactive substances (TBARS) values of muscle and microsomes isolated from fish fed the higher concentration of α-tocopherol (500 mg/kg feed) were smaller than those of fish fed the lower concentration (100 mg/kg feed). The protective effect of oleoresin rosemary on lipid oxidation in fish muscle was also observed. Analysis of variance revealed a significant (p < 0.01) interaction between dietary treatments and incubation time. Dietary α-tocopherol supplementation significantly increased the α-tocopherol concentration of muscle microsomal membranes, thereby increasing the oxidative stability of the membrane lipids.     

EFFECTS OF DIETARY SUPPLEMENTATION OF VITAMIN E ON FROZEN STORAGE STABILITY OF PRECOOKED BEEF CRUMBLES

Holstein steers supplemented for 122 days with 0, 300 or 1300 IU/day vitamin E (EO, E300, E1300) provided semimembranosus muscle for manufacturing crumbles processed with 1.5% salt and possessing either 10 or 20% fat. They were precooked, packaged (nonvacuum), frozen at -29C and stored at -18C. Following storage for 2, 90 or 180 days, lipid oxidation was measured by TBA and a trained flavor panel. TBA values at 2 days were higher (P < 0.01) for EO than E300 and E1300 crumbles. These values at 180 days for E1300 crumbles were similar to EO and E300 samples at 90 days. Lower TBA values were obtained for 10% vs 20% fat crumbles at 90 days for both E300 and E1300 treatments. Intensity ratings for rancid flavor at 90 days were highest for EO and lowest for E1300 (P < 0.001). Vitamin E exhibited antioxidant properties but additional protection is needed for this product.     

A RESEARCH NOTE DIETARY SUPPLEMENTATION OF VITAMIN E AFFECTS THE PEROXIDE VALUE OF SUBCUTANEOUS LAMB FAT

Lipid oxidation is a major problem causing flavor deterioration in meat products. The objective of this research was to utilize an iodometric peroxide value method (PV) to analyze the effects of dietary Vitamin E on lipid oxidation of subcutaneous lamb fat. Peroxide value analyses demonstrated lower lipid oxidation in the fat from animals fed 300 IU (7 days and 21 days) of Vitamin E than in the fat from animals fed diets supplemented with 15 IU (control) (P < 0.05). At 9 and II days of storage, PV analyses also demonstrated a greater rate of increase (P < 0.05) in lipid oxidation in fat from lambs fed control diets than in fat from animals fed 300 IU of Vitamin E. Results indicate that higher dietaty Vitamin E for either 7 days or 21 days antemortem reduced the rate and initiation of lipid oxidation in subcutaneous lamb fat.