脂肪氧合酶诱导脂质氧化与大豆制品品质的关系

大豆因其价廉、营养价值高而广泛应用于食品加工中。然而,普通大豆种子含有脂肪氧合酶,该酶催化多不饱和脂肪酸氧化产生氢过氧化物及其降解产物,作为潜在的反应物质它们可引起大豆蛋白质和氨基酸等的劣变,从而影响豆制品的品质。本文综述了氧化脂质与蛋白质和氨基酸的相互作用,以及脂肪氧合酶诱导脂质氧化与大豆制品品质的关系。简要回顾了通过控制脂肪氧合酶的活性,实现大豆制品品质及风味改善方面的最新进展。     

不同贮存条件下大豆油氧化指标的比较

对四个等级的大豆油在不同存放条件下的过氧化值、羰基价、茴香胺值等氧化指标的变化规律进行了研究。结果表明:在阳光直射条件下,随着贮存时间的延长,不同等级的大豆油被氧化的程度明显不同,贮存样品以过氧化值、羰基价、茴香胺值等氧化指标的上升速度排列:大豆一级油＞大豆二级油＞大豆三级油＞大豆四级油。而在其它贮存条件下,不同等级的大豆油被氧化的程度差别不明显。     

脂质氧化诱导的大豆蛋白质聚集机理的研究

利用脂肪氧合酶、亚油酸和大豆分离蛋白构建的模拟体系，研究了脂质氧化诱导的大豆蛋白质聚集的机理。结果表明，在制备大豆分离蛋白的模拟体系中同时添加亚油酸和脂肪氧合酶会使样品的蛋白质氧化值与表面疏水性增加，巯基与二硫键的含量下降，说明脂肪氧合酶催化的脂质氧化可使大豆蛋白结构发生明显的改变。SDS-PAGE电泳表明大豆蛋白7S和11S的各个亚基均参与了反应，尤其是7S部分反应更为明显。HPLC凝胶色谱和激光光散射分析进一步证实反应后的大豆蛋白（RSPI4和5）形成了相对高分子质量和颗粒粒径较大的聚集体。现有的实验证据表明，高度聚集蛋白质的形成可能是通过包括二硫键在内的共价变联，以及诸如氢键、盐桥，尤其是疏水相互作用等的非共价相互作用，形成较大的聚集体。由脂肪氧合酶诱导的蛋白质一脂质相互作用模拟实验的结果说明。脂质氧化对大豆蛋白具有明显的影响；在大豆分离蛋白加工的过程中，控制脂肪氧合酶的活力或脂质的含量是非常重要的。     

Packaging and Irradiation Effects on Lipid Oxidation and Volatiles in Pork Patties

Raw-meat patties were prepared from three pork muscles, irradiated in different packaging environments, and stored for 0 or 3 days before cooking. Lipid oxidation by-products were formed in the raw meat during storage and the baseline lipid oxidation data of raw meat was used to measure the progression of lipid oxidation after cooking. Thiobarbituric acid-reactive substances (TBARS) and volatiles data indicated that preventing oxygen exposure after cooking was more important for cooked meat quality than packaging, irradiation, or storage conditions of raw meat. Propanal, pentanal, hexanal, 1 -pentanol, and total volatiles correlated highly (P < 0.01) with TBARS values of cooked meat. Hexanal and total volatiles represented the lipid oxidation status better than any other individual volatile components.     

Packaging Cooked Turkey Meat Patties while Hot Reduces Lipid Oxidation

Elimination of oxygen by “hot packaging” reduced the 2-thiobarbituric acid reactive substances (TBARS) value of meat patties by about 50% in control and myoglobin added, and between 30-40% in ferrous iron added turkey patties, as compared with “cold packaging.” The TBARS values of hot and cold vacuum packaged patties were significantly lower than those of loosely packaged patties after 1 wk refrigerated storage. Most lipid oxidation in meat patties occurred at day 0, and only small changes in TBARS values were observed after 1 wk storage. Although the prooxidants in meat were major factors in promotion of lipid oxidation of cooked meat, hot packaging minimized their effects.     

紫外吸收剂及其在皮革化学品上的应用

紫外线吸收剂是一类可防止太阳光或其它人造紫外光引起聚合物降解的物质。针对现有无机、有机紫外吸收剂的应用发展现状和趋势,介绍了有机紫外吸收剂中的二苯甲酮类、苯并三唑类、受组胺类以及无机紫外吸收剂中纳米氧化锌、纳米二氧化钛和稀土类纳米氧化物的紫外吸收原理和应用。最后针对紫外吸收剂在皮革用染料、皮革用加脂剂、皮革用涂饰剂等皮革化学品中的应用现状进行介绍,并对以后的发展趋势进行展望。     

Kinetic Studies of Oxygen Dependence During Initial Lipid Oxidation in Rapeseed Oil

Lipid oxidation was studied in rapeseed oil, stored at 35 or 50°C in 0.03, 0.3, 1.0 or 1.8% oxygen for 42 days. Peroxide value (PV), oxygen consumption, tocopherol consumption and production of volatile compounds were analyzed to follow the oxidation. At 50°C, lipid oxidation measured as oxygen consumption or PV was only slightly influenced by oxygen concentration ≥1%. Below 0.5% the influence was strongly enhanced. The production of volatiles showed different relationships to oxygen concentration and some compounds were produced in larger amounts at lower O₂, than at higher O₂, concentrations.     

Iron-Catalyzed Oxidation of Menhaden Oil as Affected by Emulsifiers

The ability of Tween 20 and whey protein isolate (WPI) to influence lipid oxidation was investigated by evaluating the effects of emulsifier concentration and physical location on iron-catalyzed oxidation of emulsified Menhaden oil. Addition of Tween 20 or WPI to the aqueous phase of a 0.5 wt% Tween 20 stabilized emulsion increased lipid oxidation as determined by both thiobarbituric acid reactive substances (TBARS) and lipid peroxides. Tween 20 (2.0 wt%) and WPI (0.05–1.0 wt%) combinations inhibited TBARS formation 23–60%. Oxidation of a WPI-stabilized emulsion decreased with decreasing pH (3–7) but in a Tween 20 stabilized emulsion oxidation increased with decreasing pH. The low oxidation rate for the WPI-stabilized emulsion at pH 3 was increased when Tween 20 displaced WPI from the droplet interface. Results indicate that the oxidative stability of emulsifed Menhaden oil could be increased by controlling emulsifier type, location and concentration.     

Lipid Oxidation in Cooked Pork as Affected by Vitamin E, Cooking and Storage Conditions

The individual and combined effects of muscle vitamin E level, cooking conditions (duration, temperature and rate) and packaging on lipid oxidation in refrigerated cooked pork were examined. Oxidative stability following cooking was higher in pork with a higher vitamin E level (p<0.01), cooked at a lower cooking temperature (p<0.01), cooked for a shorter time (p<0.01), cooked at a faster cooking rate (p<0.05) or stored in vacuum packs (p<0.01). Significant two-way and three-way interactions were observed between the effects of muscle vitamin E level, cooking conditions and packaging on lipid oxidation. Adopting more than one of these approaches to minimize lipid oxidation was more effective than adopting a single approach.     

Prevention of Lipid Oxidation in Precooked Turkey Meat Patties with Hot Packaging and Antioxidant Combinations

The effects of antioxidants or hot packaging and their combination on lipid oxidation were quite variable depending on the additives in turkey meat. The TBARS values of cooked patties were greatly affected by the degree of oxidation in the raw meat, and the effectiveness of antioxidants varied with added prooxidants. Ascorbate and free radical terminators had stronger antioxidant effects than iron chelators, and chelating iron alone could not eliminate lipid oxidation in either raw or cooked meat with added NaCl. The combination of hot packaging and antioxidants provided cooked patties with better protection from lipid oxidation than either treatment alone.     

新型磷脂酶Lecitase Ultra用于大豆油脱胶的研究

植物油的酶法脱胶是完全有希望取代化学脱胶的一种新方法。利用新型磷脂酶Lecitase Ultra进行了大豆油脱胶的研究，确定了该酶较优的反应条件：加酶量20mg／k，pH5．0，温度48℃，加水量2％，大豆油含磷量能降到5mg／kg以下。研究认为，Lecitase Ultra是一种更适合涵脂酶法脱胶的磷脂酶。     

Whey Improves Oxidative Stability of Soybean Oil

Whey powder and Maillard reaction products (MRP) produced from whey suppressed the formation of hydroperoxides and thiobarbituric acid-reactive substances, and lowered oxygen uptake in the model system. The antioxidant activity of whey was dependent on concentration and preheating treatment. Unheated whey and whey heated for at 24 hr were most effective in retarding lipid oxidation. Whey solutions of 16% were most effective antioxidants followed by 10% and 3% solutions. As MRP indicators increased antioxidant activity increased. Whey may be useful as an antioxidant in some processed foods.     

Lecitase Novo用于大豆油脱胶的研究

利用新型微生物磷脂酶A1Lecitase Novo进行大豆油脱胶的研究，探讨了若干操作参数对大豆油脱胶效果的影响，最佳pU值为4．5～5．0、最佳温度为40～45℃、最佳加酶量为200LEU／kg油，1％～6％的加水量对脱胶无显著影响。在优化条件下进行酶法脱胶，脱胶油中含磷不超过8mg／kg。     

Oxygen Availability Affects Prooxidant Catalyzed Lipid Oxidation of Cooked Turkey Patties

The catalytic effect of free ionic iron, hemoglobin and/or NaCI, and the effect of total lipid, class of lipid, and fatty acid composition on lipid oxidation of precooked refrigerated meat patties were highly significant only when oxygen was freely accessible to the patties during storage. With limited oxygen contact (cold vacuum-packaging) after cooking, the 2-thiobarbituric acid reactive substances (TBARS) values of patties were much lower than the values for patties with free oxygen contact (loose packaging) and did not increase substantially during storage. However, the TBARS values of cold packaged patties were higher (P<0.05) than those of hot packaged patties which had almost no oxygen contact after cooking. Elimination of oxygen during storage (hot or cold vacuum-packaging after cooking) resulted in prooxidants, fat content, fatty acid composition or the class of lipids having no effect on lipid oxidation.     

酶改性大豆分离蛋白作为壁材微胶囊化海豹油研究

传统以天然大豆分离蛋白(SPI)作为壁材微胶囊对芯材包埋性不够理想,微胶囊表面有很多凹陷。该研究采用经酶法改性SPI作为壁材主要原料对海豹油进行微胶囊化,通过单因素和正交实验研究最佳壁材组合为:总固形物浓度25％、芯材／壁材30％、明胶／麦芽糊精(MD)1+3、乳化剂用量1．25％,在最优组合下所得微胶囊化产率为94．5％,效率为94．9％;所得产品形状有规则,表面无裂纹及凹陷,贮藏实验表明,微胶囊贮存稳定性大为改善。     

Measuring Lipid Oxidation Volatiles in Meats

A relatively simple, low cost vacuum distillation method for trapping and concentrating meat volatiles for identification and quantification by gas chromatography (GC) was developed. The method was used to measure the oxidative stability of cooked chicken meats from birds fed different diets. Volatiles were distilled under vacuum (< 4 mm Hg) and absorbed onto a Sep-Pak cartridge prior to GC. The method allowed the specific analysis of individual volatile products and total volatiles from lipid oxidation. The analytical data provided similar information to TBA numbers and sensory data relative to effectiveness of antioxidants in the diet for controlling oxidative deterioration of meat.     

中式香肠中脂肪氧化对蛋白质氧化的影响

以中式香肠为研究对象,通过对加工、储藏过程中包装、温度、光照以及抗氧化剂的不同处理,建立中式香肠的脂肪氧化模型,结合对其蛋白质氧化的跟踪检测,分析了中式香肠中脂肪氧化与蛋白质氧化之间的相关性。结果表明:对于脂肪氧化的抑制作用,有效抑制了蛋白质氧化形成羰基类物质,且与脂肪氧化初级和次级产物均表现较好的相关性;脂肪氧化对于蛋白质游离硫醇基流失的促进作用是由脂肪氧化次级产物挥发性醛类物质引起的。     

Lipid Oxidation Determination in Butter and Dairy Spreads by HPLC

Butter and dairy spread were stored for 14 wk at 20°C. Lipid hydroperoxides were analyzed by HPLC. Two methods were tested with chemiluminescence detection based on a post-column reaction with cytochrome c and luminol. One was for separation of neutral lipids and one for separation of phospholipids. Lipid oxidation in triacylglycerols and phospholipids in both butter and dairy spread increased during storage. A linear relationship was observed between the chemiluminescence response of oxidized triacylglycerols and the peroxide value. Correlation coefficient was 0.97 for stored butter and 0.99 for stored dairy spread (PV-range 0.1-1.4 and 0.2-5.4 meq/kg, respectively). The method is sensitive, fast and reliable for detection of primary oxidation in dairy products.     

脂肪氧化诱导鱼蛋白聚集变性研究进展

综述鱼脂肪氧化、鱼蛋白质变性以及脂肪氧化对蛋白质影响等方面的研究进展.明确提出鱼品质的下降的一个重要原因是由脂肪氧化诱导引起蛋白质劣变,下一步研究重点是探索脂肪氧化诱导蛋白质变性的机理.     

Lipid Oxidation in Cooked Turkey as Affected by Added Antioxidant Enzymes

Catalase (CAT) and glutathione peroxidase (GSH-Px) were added to turkey which had been cooked (80°C) to provide minimal activity of both enzymes, to determine their effects in development of lipid oxidation. CAT (100–500 U/g muscle) decreased the formation of thiobarbituric acid reactive substances (TBARS) 4–28% during 2 days of storage. GSH-Px (4.0 U/g muscle) decreased TBARS 8–11%. CAT (170 U/g muscle) and GSH-Px (1.3 U/g muscle) in combination decreased TBARS formation 7–14%. Reduced glutathione concentrations in the turkey were unaffected by cooking. These data suggest that heat inactivation of CAT and GSH-Px was not the only factor involved in heat-induced lipid oxidation reactions in turkey thigh muscle.