EFFECTS OF SESAME LIGNAN EXTRACT ON LINOLEIC ACID, LIPID OXIDATION, COLOR AND TEXTURAL PROPERTIES OF GROUND PORK, AND SAUSAGE PRODUCTS

Sesame lignan extract was prepared from roasted sesame oil and added at 0.02, 0.05, 0.10 and 0.20% (w/w) to linoleic acid and ground pork products. Cooked ground pork containing more than 0.02% of lignan extract showed TBA values lower than those containing butylated hydroxyanisole (BHA) during storage. Sausages containing 0.05% of lignan extract had lower thiobarbituric acid (TBA) values when stored at 4C for 14 days; they also showed higher CIE color values than the control meat sample (P < 0.05). There were no differences in textural properties such as hardness, cohesiveness and chewiness between the control and the sausages containing lignan extract when determined by Instron Testing Machine. Thus, lignan extract prepared from roasted sesame oils was highly antioxidative when used in cooked ground pork at > 0.02% or in sausages at > 0.05%.     

COMPARISON OF LINOLEIC AND CONJUGATED LINOLEIC ACIDS IN ENZYMATIC ACIDOLYSIS OF TRISTEARIN

The acyl incorporation and migration of linoleic and conjugated linoleic acids in enzymatic acidolysis were compared in a solvent-free system. Two systems were used in the Lipozyme RM IM-catalyzed acidolysis at 60C temperature and 5% by weight enzyme load (based on substrates). One included tristearin (SSS) and linoleic (L) or conjugated linoleic (cL) acids (1:6, mol/mol). The other was between tristearin and the mixture of linoleic and conjugated linoleic acids (1:3:3, mol/mol/mol). Acyl incorporation and migration together with triacylglycerol composition of the products were monitored with gas chromatography, pancreatic lipase hydrolysis, and high performance liquid chromatography. Both acyl incorporation and migration of linoleic acid were faster than those of conjugated linoleic acid. At 5 h reaction, there were 13.0% LLL, 46.5% LSL, 27.7% LSS, and 5.6% SSS in the product for a system between tristearin and linoleic acid; whereas there were 2.4% cLcLcL, 10.4% cLScL, 50.9% cLSS, and 36.2% SSS in the product for a system between tristearin and conjugated linoleic acid. The results suggest that linoleic acid was more reactive than conjugated linoleic acid in the enzymatic acidolysis probably because of the rigid structure of the latter.     

FATTY ACID COMPOSITION IN TISSUES OF MICE FED DIETS CONTAINING CONJUGATED LINOLENIC ACID AND CONJUGATED LINOLEIC ACID

The influence of 1% alpha-eleostearic acid (α-ESA, cis9,trans11,trans 13-18:3) and 1% punicic acid (PA, cis9,trans11,cis13-18:3) on fatty acid composition in mouse tissues was compared with conjugated linoleic acid (CLA, mixture of primarily cis9,trans11- and trans10,cis12-18:2) in the present study. The content (% total fatty acids) of 18:2n-6 was significantly reduced in the heart and adipose tissues, and total polyunsaturated fatty acids (PUFAs) and n-6 PUFA were significantly reduced in adipose tissue by α-ESA, PA and CLA feeding. The content of 22:6n-3 and total n-3 PUFA were significantly increased in the liver, kidney and heart by PA feeding, but not by α-ESA. In contrast to PA, supplementation with CLA significantly decreased 22:6n-3 in the liver, kidney and heart. The content of 20:4n-6 was significantly decreased in the liver and kidney by CLA feeding, but not by α-ESA and PA. The present results indicate that α-ESA, PA and CLA have differential effects on 22:6n-3 and 20:4n-6 content in mouse tissues.

PRACTICAL APPLICATIONS

Conjugated linolenic acid (CLnA), a group of octadecatrienoic acid isomers with a conjugated triene system, has been reported to exhibit favorable physiological effects, including anticancer properties and regulation of lipid metabolism. Punicic acid and alpha-eleostearic acid, two isomers of CLnA, have been shown to convert into cis 9, trans 11-18:2 in vivo . The effect of CLnA on fatty acid composition in mouse tissues was investigated in comparison with CLA mixtures in the present study. The data obtained here could provide information for the potential application of CLnA-containing seeds as functional food ingredients, a natural source of endogenously formed cis 9, trans 11-18:2 and a dietary feeding strategy to beneficially modify the fatty acid composition of animal tissues.     

LIPID OXIDATION IN A CHICKEN MODEL SYSTEM: ROLE OF LIPID AND PROTEIN FIBERS

Chicken muscle model systems were exposed to varying concentrations of lipid and protein fibers to clarify the role of these constituents in lipid oxidation. In this study, the lipid substrates examined included triacylglycerols, membrane phospholipid fractions, isolated phospholipid fractions, and free fatty acids. In iron-ascorbate catalyzed systems, increases in lipid concentration failed to lead to enhanced levels of oxidation at the examined times. Lipid was therefore not considered a rate limiting factor in the oxidation of muscle systems. Protein fibers accelerated oxidation only in sarcoplasmic reticulum (SR) membrane systems when catalyzed by iron-ascorbate. Enhanced interaction of the low molecular weight iron with the membrane lipids may be responsible for this unique response. Preferential oxidation of sulfhydryl groups in protein fibers, on the other hand, could account for the antioxidant effect displayed by protein fibers in methemoglobin catalyzed systems.     

EFFECT OF DIETARY FATS ON THE FATTY ACID CONTENTS OF CHICKEN ADIPOSE TISSUE

SUMMARY— 150 broiler-type chicks were reared from hatching to 4 wk of age on a low-fat ration before being fed diets containing 10% of either corn oil, lard, beef tallow or hydrogenated coconut oil. Analyses of treatment effects were made at 2 wk intervals until the chicks were 10 wk old. The fatty acid content of extracted total lipids were characteristic of the dietary fats and dietary fatty acid patterns were incorporated into the adipose tissue within 2 wk after the experimental diets were fed. The total lipids when separated into solid fats and liquid oils at room temperature also reflected the fatty acid pattern of the experimental diets. Neutral triglycerides from the adipose tissue contained less linoleic acid and more palmitic and oleic acids than the total lipid fraction. High amounts of palmitic and oleic acids were observed in all of the fractions analyzed. No significant differences were found in total cooking loss, drip loss, taste preference, or TBA values of skin or adipose tissue among the 10 wk old chickens fed different experimental diets.     

EFFECTS OF CONJUGATED LINOLEIC ACID ISOMERS ON SERUM TUMOR NECROSIS FACTOR-A CONCENTRATION IN MICE

In previously studies, we showed that tumor necrosis factor‐α (TNF‐α), a cytokine involved in a variety of biologically important events, is partially involved in the effects of conjugated linoleic acid (CLA). In this report, we further tested the effects of individual CLA isomers on serum TNF‐α concentration along with other biological markers in mice. The animals were fed experimental diets (control, 0.5% CLA‐mixed isomer, 0.25% cis‐9,trans‐11 CLA or 0.25% trans‐10,cis‐12 CLA) for 5 days and were then challenged with endotoxin. Both cis‐9,trans‐11 and trans‐10,cis‐12 CLA isomers reduced serum TNF‐α levels compared to control. CLA had no effect on the other biological markers examined. These results suggest possible early involvement of CLA in immune and/or inflammatory responses, followed by reduction of body fat. Its effect on TNF‐α helps explain in part how CLA modulates other biological functions such as immune response, insulin responses, atherosclerosis and cancer.     

LIPID OXIDATION IN RETAIL BEEF, PORK AND CHICKEN MUSCLES AS AFFECTED BY CONCENTRATIONS OF HEME PIGMENTS AND NONHEME IRON AND MICROSOMAL ENZYMIC LIPID PEROXIDATION ACTIVITY

Muscles of beef, pork and chicken purchased in two seasons were analyzed for lipid oxidation potential, concentrations of total pigments, myoglobin and nonheme iron, and microsomal enzymic lipid peroxidation activity. To determine lipid oxidation potential, thiobarbituric acid (TBA) assays with antioxidant protection were conducted on raw and cooked comminuted muscles stored at 4°C. TBA values of raw chicken muscles (white and dark) and pork muscles were low and changed little during 2–6 days of storage, whereas the values of raw beef muscles were higher and increased progressively. However, TBA values of cooked muscles of all three species increased during 2–4 days of storage with no marked differences among the species. Total pigment and mycglobin concentrations best explained the differences in TBA values of stored, raw muscles among the three species.     

LIPID AND CHOLESTEROL OXIDATION,COLOR CHANGES,AND VOLATILE PRODUCTION IN IRRADIATED RAW PORK BATTERS WITH DIFFERENT FAT CONTENT1

An emulsion-type product was prepared to determine the effect of irradiation on lipid and cholesterol oxidation, color change, and volatile production in raw pork with different fat contents. Lipid oxidation increased with an increase in fat content or irradiation dose. Irradiated batters had higher cholesterol oxides than nonirradiated, and the major cholesterol oxides formed in irradiated pork batters were 7α- and 7β-hydroxycholesterol. Hunter color a- and b-values of raw pork batters were decreased by irradiation regardless of fat content. Irradiation increased the amount ofvolatiles significantly. Although lipid oxidation of high fat products (10 and 15% fat) was higher than that of low fat products (4%), high fat products did not always produce greater amount of volatiles. In summary, irradiation increased lipid and cholesterol oxidation, volatiles production and had detrimental effects on the color of raw pork batters under aerobic condition.     

THE EFFECTS OF DIETARY α-TOCOPHEROL AND SURFACE APPLICATION OF OLEORESIN ROSEMARY ON LIPID OXIDATION AND CHOLESTEROL OXIDE FORMATION IN COOKED RAINBOW TROUT (Oncorhynchus mykiss) MUSCLE

The inhibitory effect of dietary α-tocopherol supplementation (100 and 500 mg α-tocopheryl acetate/kg diet) and an oleoresin rosemary dip on lipid and cholesterol oxidation in cooked rainbow trout ( Oncorhynchus mykiss ) during storage at 4C for 48 h was investigated. The 2-thiobarbituric acid-reactive substances (TBARS) values of cooked fish muscle increased during storage for all treatments. Dietary α-tocopherol supplementation partially inhibited lipid oxidation. Surface application of oleoresin rosemary further enhanced this protective effect. Cholesterol oxides were formed in all the samples following cooking and storage. The major cholesterol oxidation products (COPS) were identified as 7 β-hydroxycholesterol, α- and β-epoxides, and 7-ketocholesterol. Formation of COPS was reduced by dietary supplementation with α-tocopherol and surface application of oleoresin rosemary. Statistical analysis revealed a highly significant (p < 0.01) inhibitory effect of oleoresin rosemary on COPS formation.     

THE EFFECTS OF FROZEN STORAGE ON THE RETAIL ACCEPTABILITY OF PORK LOIN CHOPS AND SHOULDER ROASTS

Uncured shoulder roasts and loin chops were utilized to evaluate the effects of frozen storage for different intervals (0, 56, 84, 112, 140, 168 and 196 days) in different protective storage wraps (oxygen–permeable retail wrap, polyethylene bags, aluminum foil, and freezer paper) upon factors contributing to their retail acceptability after thawing and 24 h of subsequent display. The composite results of this study indicate that uncured pork cuts can be successfully frozen and stored for at least 196 days at ?30° C in still air, in the dark, in any of the protective storage wraps evaluated, and be thawed for 24 h at 2° C prior to being retailed and generally be as acceptable as their fresh counterparts during 24 h of retail display.     

二十二碳六烯酸(DHA)、二十碳五烯酸(EPA)、亚油酸、亚麻酸和花生四烯酸(AA)在婴幼儿配方奶粉中的测定

建立了气相色谱法同时测定婴幼儿奶粉中的DHA,EPA,亚油酸,亚麻酸和花生四烯酸AA含量的方法。采用色谱柱为脂肪酸型色谱柱DB-23,氢火焰离子化检测器（FID）,优化了色谱条件。结果表明,DHA,EPA,亚油酸,亚麻酸和花生四烯酸AA分离效果很好。DHA的最低检出限为0.02g/L,回收率为99.8%,变异系数为0.88%;EPA的最低检出限为0.01g/L,回收率为94.9%,变异系数为1.01%;亚油酸的最低检出限为0.02g/L,回收率为97.7%,变异系数为0.80%;亚麻酸的最低检出限为0.01g/L,回收率为99.9%,变异系数为0.95%;AA的最低检出限为0.01g/L,回收率为98.9%,变异系数为0.93%。     

INFLUENCE OF FEED FAT SOURCE ON FATTY ACID COMPOSITION, UNSATURATION AND LIPID OXIDATION OF BACKFAT AND SENSORY QUALITY OF PORK

The effect of different fats in a 9% fishmeal feed on backfat fatty acid composition, oxidation and pork sensory attributes was studied. The hydrogenated fish oil group (HFO) had significantly increased uptake of certain fatty acids in contrast to the other groups. Iodine values were highest in the fish oil group, followed by the lamb tallow group (LT) with the control group, containing no added fat, tailing. Backfat from the HFO group had more polyunsaturated fatty acids compared to the other groups and stearic/linoleic acid ratio suggested more oxidative problems with this group. The HFO group led the LT group in oxidation with the control group being most stable. Sensory traits of fresh and frozen pork chops correlated with the oxidation results. Fat from pigs fed hydrogenated fish oil in their diet are therefore more susceptible towards oxidation possibly due to more polyunsaturated fatty acids and oxidation products in the backfat.     

气相色谱-质谱联用法分析苏尼特羔羊肉中共轭亚油酸含量

共轭亚油酸是亚油酸的一组几何和位置异构体，具有多种生理功能。作为瘤胃微生物的产物，反刍动物肉制品是共轭亚油酸异构体较丰富的天然来源，本研究利用气相色谱-质谱联用法分离测定了5月龄苏尼特羔羊肌肉和腹部脂肪中共轭亚油酸总含量，研究结果表明，背最长肌间脂肪中CLA相对百分含量平均为0．83％，腹部脂肪中CLA相对百分含量平均为0．99％。     

THE EFFECTS OF FROZEN STORAGE AND PROTECTIVE STORAGE WRAP ON THE RETAIL CASE-LIFE OF PORK LOIN CHOPS

Loin chops from 60 pork carcass sides were utilized to evaluate the influences of frozen storage and protective storage wrap upon factors contributing to the retail case-life of thawed chops. The composite results of this study indicated that pork loin chops could be frozen and stored for 168 days or less at ?30° C and have a retail case-life of at least 6 days, under the conditions employed in the present study. The possible exception is an amount of drip in the packages of chops stored in certain protective wraps which may be unacceptable when displayed for prolonged periods.     

LIPID OXIDATION AND SENSORY CHARACTERISTICS OF FRESH AND CURED SAUSAGES FROM α-LINOLENIC ACID ENRICHED PORK

Forty-eight female piglets were raised with four levels of α-linolenic acid (0, 1.5, 2.5, 3.5%) to determine the effect of dietary fat on the fatty acid composition, sensory and storage stability of pork products. The degree of polyunsaturation in neutral lipids and phospholipids were increased significantly by the dietary LNA. The thiobarbituric acid reactive substances (TBARS) vaues of freshly prepared breakfast sausages with vacuum packaging remained low, but those of the loosely packaged, i. e., nonvacuumized, sausages increased more than 3 times during the 48 h storage period. The TBARS values of breakfast sausages frozen-stored for 3 months showed extensive lipid oxidation. The dietary LNA treatments and packaging had significant effects on the susceptibility of breakfast sausages to lipid oxidation. However, the oxidative stability of cured products was not affected by the dietary treatments. The results indicated that the pork enriched with polyunsaturated fatty acids could be used in cured products or uncured meat products protected by ‘hot vacuum packaging’without any sensory or quality deterioration due to lipid oxidation.     

VARIATION IN THE CONJUGATED LINOLEIC ACID CONTENT OF THREE TRADITIONAL GREEK CHEESES DURING A 1-YEAR PERIOD

The fat and fatty acid content of three traditional Greek cheeses were determined monthly for a period of 1 year. The analyzed cheeses, feta, graviera and manouri, are traditional Greek dairy products made exclusively or primarily from sheep milk. In all cheeses, the content of the fatty acids varies during several months, especially the conjugated linoleic acid (CLA) content of feta, graviera and manouri ranged between 0.5 and 0.9, 0.5 and 1.0 and 0.4 and 0.8 g/100 g total fatty acids, respectively. The average content of CLA in graviera and feta was similar (0.75 and 0.72 g/100 g fatty acids, respectively). On the other hand, the CLA content of manouri (0.54 g/100 g fatty acids) was less than that of the other two cheeses. In every case, the analyzed cheeses can be characterized as good or very good CLA sources.

PRACTICAL APPLICATIONS

No data exist about the variation in the fatty acid composition of standardized cheeses during the various months of the year. Several investigations were carried out in order to determine the fatty acid composition and especially the conjugated linoleic acid (CLA) content of various kinds of cheese. However, cheeses were produced from milk and it is suggested that the milk composition is affected by seasonal factors. In the present investigation, we tried to find out if the beneficial fatty acid content of cheeses, which were previously found as rich CLA sources, is season dependent. The results of this research are a potential tool for food technologist in order to provide CLA-enriched diets.     

EFFECTS OF A CRYOGENIC AND THREE HOME FREEZING METHODS ON SELECTED CHARACTERISTICS OF PORK LOIN CHOPS

SUMMARY— Thirteen pairs of pork loin chops from each of four carcasses were assigned randomly to 13 treatments to study effects of freezing by liquid nitrogen vapor and by three home methods, and effects of 1 and 4 wk of storage in three types of home freezers. Regardless of freezing method, cooking losses (total, volatile and drippingl were higher (P < 0.01) and water-holding capacity of the LD muscle lower (P < 0.05) for frozen than for fresh chops. Acid number, flavor scores and over-all acceptability scores were higher (P < 0.05, P < 0.01, P < 0.01) for fresh than for frozen chops. Both immediately after freezing and after 1 and 4 wk of storage, liquid nitrogen freezing produced chops superior in appearance to home-frozen chops. Total and dripping cooking losses were greater (P < 0.05 and 0.01), and total moisture of the LD lower (p < 0.05) for liquid nitrogen-frozen than for home-frozen chops. Free fatty acid was higher (P < 0.05) in liquid nitrogen-frozen than in home-frozen chops. Tenderness and over-all acceptability scores were higher (P < 0.05) for chops stored in a one-door refrigerator-freezer than for those stored in a two-door refrigerator-freezer or an upright household freezer. Regardless of freezing method or storage conditions, volatile cooking losses and free fatty acids increased (P < 0.05), and over-all acceptability and tenderness scores decreased (P < 0.01) between 1 and 4 wk of storage. The interaction between storage conditions and storage time resulted in greater (P < 0.051 increase in free fatty acids between 1 and 4 wk for chops stored in a one-door refrigerator-freezer than for those stored in the two other types of home freezers. Flavor and over-all acceptability scores decreased (P < 0.05) between 1 and 4 wk for chops stored in either refrigerator-freezer combination, but did not decrease during 4 wk of storage for chops in the upright household freezer.