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.     

LIPIDS IN WILD RUMINANT ANIMALS AND STEERS

Lipid was extracted from the biceps femoris and longissimus dorsi muscles of pronghorn antelope, mule deer, elk, range steers and feedlot steers after being trimmed of subcutaneous fat and connective tissue. Muscles of game animals contained more phospholipids than those of steers and muscles of antelope and deer were higher in cholesterol. Muscles of feedlot steers contained the most total lipid and triglycerides. Polyunsaturated lipid was highest in muscles of game animals due to higher levels of phospholipids. Polyunsaturated:saturated lipid ratios were highest in muscles of game animals followed by those in the muscles of range steers and lastly by those in the muscles of feedlot steers. In addition, the proporation of 18:3, an omega-3 polyunsaturated fatty acid, in total polyunsaturated acids measured were higher in the muscles of game animals and range steers than in those of feedlot steers.     

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.     

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.     

共轭亚油酸的功能性质及安全性评价

介绍了共轭亚油酸及其对健康的益处，综述了共轭亚油酸对动物和人体机体组成影响的研究进展，并讨论了共轭亚油酸添加物的安全性问题。研究认为，共轭亚油酸对健康和机体组成等均具有较好的作用，但人体服用共轭亚油酸的安全性问题有待进一步的研究。     

功能性油脂共轭亚油酸及其在食品工业中的应用

作为一种新型功能性油脂，共轭亚油酸由于具有抑癌、减肥、抗动脉硬化、提高免疫力等多种有益作用．在国际上越来越受关注。本文分别从其来源、生理功能及其在食品工业上的应用等方面进行综述。     

LIPASE-CATALYZED ACIDOLYSIS OF CORN OIL WITH CONJUGATED LINOLEIC ACID IN HEXANE

Lipase-mediated acidolysis of corn oil with conjugated linoleic acid (CLA) was studied in hexane. The largest extent of incorporation was obtained using a weight ratio of CLA to corn oil of 1:7 (1:2.22 mole ratio). Commercial immobilized lipases from Rhizomucor miehei and Candida antarctica effectively catalyzed interesterification. Of the total acylglycerols in the products, triacylglycerols constituted >90%. For both immobilized enzymes, CLA residues were esterified mainly at the sn-1,3 positions.     

CONJUGATED LINOLEIC ACID CONCENTRATIONS IN COOKED BEEF CONTAINING ANTIOXIDANTS AND HYDROGEN DONORS

Conjugated linoleic acid (CLA) is a potential anticarcinogenic compound found in beef. The ability of antioxidants and hydrogen donors to influence CLA concentrations in ground beef during cooking (broiled, 80C) and storage was determined. Addition of food additives such as carnosine, cysteine, ascorbate, whey protein concentrate or beef plasma to ground beef did not result in any significant increases or decreases in CLA concentrations in freshly cooked beef. Additives which inhibited formation of thiobarbituric acid reactive substances in stored meat including 2.0% WPC, 0.5 and 2% beef plasma, ascorbate (0.5%) and carnosine (0.5%) were not any more effective at increasing or decreasing total CLA concentrations than additives which did not inhibit lipid oxidation during storage (0.5% WPC and 0.5% cysteine). Lack of changes in CLA in the presence of antioxidants suggests that these additives could be used to inhibit flavor deterioration of cooked beef products without decreasing CLA concentrations.     

DETERMINATION OF COLLAGEN SOLUBILITY AND CONCENTRATION IN MEAT BY NEAR INFRARED SPECTROSCOPY

This paper examines the feasibility of measuring collagen properties by near infrared spectroscopy (NIRS) in ovine Semimembranosus and Biceps femoris muscles. Because collagen concentration within a muscle was rather narrow, the R for collagen concentration was never more than 0.55. By contrast, R for solubility was better, especially for Semimembranosus, always exceeding 0.80. No one scanning method — fiberoptic probe or the in-built transport module — was superior, either in reflectance or transmittance modes. The equations developed were tested for predictive power by cross-validation procedures within muscles and between muscles. In the latter case, Biceps femoris data were used in a Semimembranosus equation and vice versa. The equations worked in any combination. However, there were indications that the correlations were sensitive to the state of the meat, whole tissue or homogenized, although the wavelength range 910 to 950 nm did not vary with sample state.     

天然活性物质共轭亚油酸的化学合成与生物转化

介绍了近年来在共轭亚油酸的化学合成及生物转化领域中取得的进展，并做了简要评述。     

LIPIDS AND FATTY ACIDS OF FIVE FRESHWATER FOOD FISHES OF INDIA

Five species of carp important in the diet of many of the people of India were examined for principal lipids and in particular for the highly unsaturated fatty acids with potential biomedical benefits. Muscle lipid was about 1% in four species but 2.5% in muscle of Labio bata. The livers however had lipid contents in the 5–10% range. The principle lipid classes were separated and the fatty acids were determined by open-tubular (capillary) gas-liquid chromatography; forty-seven fatty acids were quantified. Saturated fatty acids were approximately 40–50% of total fatty acids in muscle lipids and monoethylenic fatty acids were 24–39%. Functionally important fatty acids of triacylglycerols in the muscle of all species included about 5% each of 18:2n-6 and 18:3n-3. The longer chain lengths 20:4n-6, 20:5n-3, and especially 22:6n-3, were found mostly in the polar lipids     

FUNCTIONALITY OF MILK PROTEINS AND CORN GERM PROTEIN FLOUR IN COMMINUTED MEAT PRODUCTS1

Effects of corn germ protein flour (CGPF), nonfat dry milk (NFDM), whey protein concentrate (WPC), and sodium caseinate (SC) on quality characteristics of comminuted meat products were studied. Water holding capacity (WHC) was lowest and cooking loss was highest for the control formulation, whereas formulations extended with CGPF and milk proteins were higher in WHC and lower in cooking losses. Shear force and firmness increased as extenders were added, except WPC. All frankfurters with extenders were firmer than the control, except those extended with WPC. Hue angle was highest for samples with CGPF, while no differences were found in hue angle between control and milk proteins containing samples, except samples with WPC. Frankfurters with CGPF and SC add had a stronger atypical aroma than the control. Meaty aroma score was higher for the control than for the other products, except those with WPC. Meaty flavor score was higher for the control than for all other products. The product with CGPF added had a stronger atypical flavor than the control. Frankfurters containing extenders were not as juicy as the all-meat control.     

嗜酸乳杆菌发酵生产共轭亚油酸工艺研究

共轭亚油酸是一种具有多种生理活性的天然脂肪酸。以盐生植物紫花苜蓿的种籽油为底物，用嗜酸乳酸杆菌（Lactobacillus acidophilus）1．1854催化紫花苜蓿籽油中的亚油酸转化为共轭亚油酸。通过单因孝实验分析了发酵过程中pH、温度、预培养和苜蓿籽油的浓度对生产共轭亚油酸的影响。