Omega—3系多不饱和脂肪酸的生理作用

本文主要阐述近年来研究报道Omega-3系多不饱和脂肪酸的生理作用。     

Effects of fatty acids on meat quality: a review

Interest in meat fatty acid composition stems mainly from the need to find ways to produce healthier meat, i.e. with a higher ratio of polyunsaturated (PUFA) to saturated fatty acids and a more favourable balance between n-6 and n-3 PUFA. In pigs, the drive has been to increase n-3 PUFA in meat and this can be achieved by feeding sources such as linseed in the diet. Only when concentrations of α-linolenic acid (18:3) approach 3% of neutral lipids or phospholipids are there any adverse effects on meat quality, defined in terms of shelf life (lipid and myoglobin oxidation) and flavour. Ruminant meats are a relatively good source of n-3 PUFA due to the presence of 18:3 in grass. Further increases can be achieved with animals fed grain-based diets by including whole linseed or linseed oil, especially if this is "protected" from rumen biohydrogenation. Long-chain (C20-C22) n-3 PUFA are synthesised from 18:3 in the animal although docosahexaenoic acid (DHA, 22:6) is not increased when diets are supplemented with 18:3. DHA can be increased by feeding sources such as fish oil although too-high levels cause adverse flavour and colour changes. Grass-fed beef and lamb have naturally high levels of 18:3 and long chain n-3 PUFA. These impact on flavour to produce a 'grass fed' taste in which other components of grass are also involved. Grazing also provides antioxidants including vitamin E which maintain PUFA levels in meat and prevent quality deterioration during processing and display. In pork, beef and lamb the melting point of lipid and the firmness/hardness of carcass fat is closely related to the concentration of stearic acid (18:0).     

Omega-3脂肪酸磷脂制备方法综述

Omega-3脂肪酸磷脂生理功能明确,生物利用度高,在医药、保健品领域具有巨大的市场潜力,其制备方法是全球磷脂研究开发的新动向。综述了目前Omega-3脂肪酸磷脂的制备方法,包括天然提取法、酶促转化法、化学合成法及微生物发酵法。天然提取法是最早获得Omega-3脂肪酸磷脂产品的方法,主要包括溶剂萃取法、膜分离法、柱层析法和盐沉淀法;酶促转化法主要包括酶促酯交换法和酶促酯化法,是目前Omega-3脂肪酸磷脂合成效率最高、最常用的方法;化学合成法及微生物发酵法处于初步研究阶段,为Omega-3脂肪酸磷脂的制备提供了新的思路。     

Dietary manipulation of muscle long-chain omega-3 and omega-6 fatty acids and sensory properties of lamb meat

The effects of dietary manipulation of muscle long-chain omega-3 fatty acids (FA) on sensory properties of cooked meat in second cross ([Merino×Border Leicester]×Poll Dorset) wether lambs were evaluated. Lambs fed dietary supplements of fish meal (FM, Exp. 1) and fish oil (FO, Exp. 2) showed moderately (P<0.01) and markedly (P<0.001) increased muscle long-chain omega-3 FA content compared with those fed the basal diet of lucerne chaff and oat chaff. Protected canola seed (PCS, Exp. 1) significantly (P<0.001) increased omega-6 FA content of the longissimus muscle. In each of the 2 experiments (1 and 2), after being fed experimental diets for 6 weeks lambs were slaughtered at a commercial abattoir. At 24 h post-mortem (PM) the semitendinosus and biceps femoris muscles were removed from animals and stored at -20°C until evaluation of sensory properties using experienced panel members. The muscle samples were stored for 3 (Exp. 1) and 12 (Exp. 2) months then removed, thawed and cooked for sensory evaluation. The meat samples were cooked under standardized conditions in a convection microwave at 180°C (20-25 min) to an internal temperature of 75°C. Cooked samples were tested for flavour, aroma, juiciness and overall palatability. The significant increase in muscle long-chain omega-3 with FM (Exp. 1 and 2) and FO (Exp. 2) or omega-6 FA with PCS (Exp. 1) were not detrimental to sensory panel evaluations of flavour or aroma of cooked meat when compared with the basal diet. However, meat from FM (Exp. 1) had lower juiciness and FO (Exp. 2) had lower overall palatability. Protected sunflower meal protein with FO (Exp. 2) significantly lowered ratings for flavour, juiciness and overall palatability. Lamb meat with increased levels of long-chain omega-3 FA can be produced without altering the sensory quality (flavour or aroma) of the cooked meat.     

Omega-3多不饱和脂肪酸性质、功能及主要应用

多不饱和脂肪酸是一大类重要的功能性油脂,根据双键的位置主要分为ω-3系和ω-6系,其中ω-3系主要包括α-亚麻酸(ALA)、二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)。ω-3多不饱和脂肪酸具有降血脂、增强免疫力、辅助改善记忆等方面的卓越生理功能,已被广泛用于食品、药品和保健品。本文综述了Omega-3多不饱和脂肪酸来源及生理功能,阐述了ω-3系多不饱和脂肪酸ALA、EPA和DHA的结构、来源、性质、生产技术和生理功能,归纳分析了omega-3多不饱和脂肪酸在婴幼儿食品、休闲食品和膳食补充剂方面的主要应用,并展望了未来利用现代生物技术获得高含量目标产物原料品种、并不断完善分离纯化技术和制剂技术为今后研究方向。     

Omega-3 fatty acids affected human perception of ground beef negatively

The objective was to determine the impact of increasing levels of Eicosapentaenoic acid (EPA; C20:5n3) and Docosahexaenoic acid (DHA; C22:6n3) on beef palatability. Two commercial supplements of EPA and DHA were added to 85% lean ground beef patties (176.2 ± 3.76 g) with different levels (0, 0.3, 0.4, 0.5, 0.6, 0.7, and 1% as-is). Olive oil was added so that all patties contained 1% added lipid. A control treatment was also prepared with no supplement or olive oil. Sensory evaluation and fatty acid analysis was conducted. Ground beef flavor decreased linearly (P<0.001) with increasing levels of EPA and DHA. Off-aroma and off-flavor increased linearly and then plateaued with increasing levels of EPA (P<0.0001). In conclusion, EPA had a greater negative impact on beef palatability than DHA. Also, the panelists were more sensitive to EPA in off-flavor perception than off-aroma.     

Effects of dietary fats on meat quality and sensory characteristics of heavy pig loins

Forty-eight crossbred growing-finishing pigs were used to study the effects of polyunsaturated fatty acids (PUFA 31%= low and 50%= high) and fish oil (0, 0.2, and 0.4% capelin) diets on fatty acid composition, chemical traits, and sensory properties of the longissimus muscle, fat, and sausages. High levels of PUFA, independent of the level of fish oil, increased oxidation and rancidity for whole muscle (stored at 1 and 8 months at -23?°C) and sausages (TBARS 0.6-1.3). Fish oil at 0.4% in the diet increased TBA values of loin, but did not affect sensory evaluation scores. An interaction between PUFA and fish oil occurred for TBARS values and rancid odour in sausage, where the 0.4% fish oil and high PUFA level showed highest oxidation (TBARS 1.9). Although fish oil and high PUFA levels might contribute to a more healthy meat, their undesirable affects on palatability would limit their use.     

Nutritional and sensory aspects of light lamb meat enriched in n−3 fatty acids during refrigerated storage

Fatty acid content and sensory characteristics of meat from light lambs fed three diets supplemented with different sources of n−3 fatty acids (fish oil, extruded linseed and extruded linseed plus microalgae) and a control diet during refrigerated storage have been studied. The meat from lambs fed linseed diets had the highest levels of C18:3 n−3, while animals fed fish oil had the highest long-chain n−3 polyunsaturated fatty acids (PUFA). Thus, 100 g of meat from lamb fed the fish oil diet provided 183 mg of long-chain n−3 PUFA, representing 40% of the daily recommended intake. The levels of n−3, n−6 and long-chain n−3 PUFA decreased during a 7-day storage period. The meat from lambs fed the fish oil diet had high scores of fish odour and flavour and rancid odour and flavour and the lowest overall liking. Rancid odour and flavour increased after storage, mainly in supplemented groups.     

Effect of branched-chain fatty acids, 3-methylindole and 4-methylphenol on consumer sensory scores of grilled lamb meat

Tenderness, flavour, overall liking and odour are important components of sheepmeat eating quality. Consumer assessment of these attributes has been made for carcasses from the Information Nucleus Flock (INF) of the Cooperative Research Centre for Sheep Industry Innovation. The concentrations of three branched chain fatty acids, 4-methyloctanoic (MOA), 4-ethyloctanoic (EOA) and 4-methylnonanoic acids (compounds related to ‘mutton flavour’ in cooked sheepmeat) and 3-methylindole and 4-methylphenol (compounds related to ‘pastoral’ flavour) were determined for 178 fat samples taken from INF carcasses. Statistical modelling revealed that both MOA and EOA impacted on the ‘Like Smell’ consumer sensory score of the cooked meat product (P < 0.05), with increasing concentration causing lower consumer acceptance of the product. None of the compounds though had an effect on the liking of flavour. Obviously, reducing the effect of MOA and EOA on the odour of grilled lamb will improve consumer acceptance of the cooked product but other factors affecting the eating quality also need to be considered.     

Oil-in-water emulsions as a delivery system for n-3 fatty acids in meat products

The oxidative and physical stabilities of oil-in-water emulsions containing n-3 fatty acids (25 wt.% oil, 2.5 wt.% whey protein, pH 3.0 or pH 6.0), and their subsequent incorporation into meat products were investigated. The physical stability of fish oil emulsions was excellent and neither coalescence nor aggregation occurred during storage. Oxidative stability was better at pH 6.0 compared to pH 3.0 likely due to antioxidative continuous phase proteins. Incorporation of fish oil emulsions into pork sausages led to an increase in oxidation compared to sausages without the added fish oil emulsion. Confocal microscopy of pork sausages with fish oil emulsions revealed that droplets had coalesced in the meat matrix over time which may have contributed to the decreased oxidative stability. Results demonstrate that although interfacial engineering of n-3 fatty acids containing oil-in-water emulsions provides physical and oxidative stability of the base-emulsion, their incorporation into complex meat matrices is a non-trivial undertaking and products may incur changes in quality over time.     

感官评价原理在肉质评价中的应用

论述了感官评价原理的基本内容及其在肉质感官评价中的应用。着重论述了肉质评价员的选拔与培训、肉质评价专门实验室的建设原则、肉质评价程序的设计原则、肉质感官评价结果的分析。最后简单分析了我国肉质感官评价存在的问题及对策。     

Genotype with nutrition interaction on fatty acid composition of intramuscular fat and the relationship with flavour of pig meat

Forty-one autumn-born Friesian bull calves were allocated to two production systems (Extensive='E'and Intensive='I'). In the E-system, animals were loose-housed and fed a roughage-based diet from October to May, followed by a grazing period from May to October. Ten animals were slaughtered directly from pasture in October [360 kg body weight (BW)] and 11 after a 10-week finishing period in tie-stalls (460 kg). The E-bulls were compared with intensively-fed tie-stall-housed young bulls (I) slaughtered at comparable weights (360 kg, n=11 and 460 kg, n=9). The myofibril fragmentation index (MFI) was measured 24 h post mortem in semitendinosus (ST), longissimus dorsi (LD), and supraspinatus (SU) muscles, and meat quality characteristics and sensory evaluation of LD were performed on aged meat. Intramuscular fat content was lower (P<0.001) in all three muscles of E- compared with I-bulls. MFI of ST and LD was lower in E-bulls compared with I-bulls, but only at 360 kg. In contrast, MFI of SU was higher in E- compared with I-bulls at 360 kg. In E- compared with I-bulls, shear force value of ST was higher (P<0.003) at 360 kg, but not at 460 kg. Panel scores for tenderness, taste and juiciness were all lower (P<0.006 to 0.001) and remarks for off-flavour higher in E- compared with I-bulls, the effects being most pronounced at 360 kg. A 10-week finishing period improved all meat and eating quality characteristics of E-bulls. In LD, the correlation between MFI and tenderness was 0.79 (P<0.001), which indicates a potential of MFI as an early predictor of tenderness.     

Changes in fatty acid composition and improved sensory quality of backfat and meat of pigs fed bacterial protein meal

A total of 48 pigs (11.4 and 107.2 kg initial and final weight) were used to evaluate increasing dietary levels of bacterial protein meal (BPM) produced on natural gas (0, 50, 100, or 150 g kg⁻¹) on fatty acid composition, sensory properties, and susceptibility of pork to lipid oxidation. Increasing levels of BPM to diets increased the content of C16:1 fatty acids in backfat and muscle and total monounsaturated fatty acids in muscle, but decreased the content of polyunsaturated fatty acids and iodine value in backfat and muscle. Pigs fed diets containing BPM had reduced thiobarbituric acid reactive substances (TBARS) value in backfat and muscle, reduced intensity of odor and rancid odor and taste in pork after short-time storage, and reduced off-odor and off-taste after intermediate-time storage. To conclude, adding BPM to diets for pigs changed the fatty acid profile, improved the oxidative stability, and sensory quality of pork.     

肉类脂肪酸的营养与免疫调节作用

综述了肉类脂肪中饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸及共轭多不饱和脂肪酸构成特性及其对人体的营养与健康功能,以及肉类脂肪中三酰甘油、磷脂、固醇类等的免疫调节作用与疾病的关系。     

Predicting beef cuts composition,fatty acids and meat quality characteristics by spiral computed tomography

The potential of X-ray computed tomography (CT) as a predictor of cuts composition and meat quality traits using a multivariate calibration method (partial least square regression, PLSR) was investigated in beef cattle. Sirloins from 88 crossbred Aberdeen Angus (AAx) and 106 Limousin (LIMx) cattle were scanned using spiral CT. Subsequently, they were dissected and analyzed for technological and sensory parameters, as well as for intramuscular fat (IMF) content and fatty acid composition. CT-PLSR calibrations, tested by cross-validation, were able to predict with high accuracy the subcutaneous fat (R², RMSECV = 0.94, 34.60 g and 0.92, 34.46 g), intermuscular fat (R², RMSECV = 0.81, 161.54 g and 0.86, 42.16 g), total fat (R², RMSECV = 0.89, 65.96 g and 0.93, 48.35 g) and muscle content (R², RMSECV = 0.99, 58.55 g and 0.97, 57.45 g) in AAx and LIMx samples, respectively. Accurate CT predictions were found for fatty acid profile (R² = 0.61–0.75) and intramuscular fat content (R² = 0.71–0.76) in both sire breeds. However, low to very low accuracies were obtained for technological and sensory traits with R² ranged from 0.01 to 0.26. The image analysis evaluated provides the basis for an alternative approach to deliver very accurate predictions of cuts composition, IMF content and fatty acid profile with lower costs than the reference methods (dissection, chemical analysis), without damaging or depreciating the beef cuts.     

Effect of lipid type on growth performance,meat quality and the content of long chain n − 3 fatty acids in pork meat

The aim of the present study was to produce pork with enhanced nutritive value for humans, both in terms of fatty acid profile (mainly long chain n − 3 fatty acids by feeding fish oil) and selenium. Forty-eight female pigs were allocated to one of six treatment groups: animal by-products and plant feedstuffs with tallow, plant feedstuffs with a blend of soybean oil and linseed oil with or without a supplement (CLA, selenium, vitamin E and vitamin C), plant feedstuffs with tallow and supplement, plant feedstuffs with fish oil and supplement. The diets containing the fish oil were fed up to either 49 days or 28 days before slaughter. The dietary treatments had no significant effects on growth performance, carcass characteristics and meat quality. When fish oil was included in the diet, higher levels of EPA, DPA and DHA were measured in the subcutaneous fat (up to 3.74%).     

浅析乳制品中脂肪酸类营养强化剂检测方法

本文将乳制品经酸水解后,利用乙醇-乙醚-石油醚提取脂肪酸,在碱性条件下进行甲基化反应,用气相色谱-质谱法测定出添加的7种脂肪酸类营养强化剂。本检测方法前处理简单快捷,易于操作,方法重现性良好,其RSD可达0.82%～1.78%;回收率可达89.9%～103.6%;灵敏度高,检测限为0.1 mg/kg。