大米蛋白酶解物的ACE抑制活性研究

为了考察大米四种蛋白经模拟体外消化后能否产生ACE抑制活性肽及其活性状况,本研究以大米为原料,Osborne法提取大米四种蛋白。体外模拟胃肠道消化过程,研究消化酶解ACE抑制活性肽产生情况及其活性大小,同时检测酶解产物的水解度和分子量分布。实验结果表明,大米四种蛋白经胃蛋白酶消化30min,酶解产物的ACE抑制活性均达到较高水平,随后经过胰蛋白酶作用,酶解产物的ACE抑制活性下降。大米清蛋白、球蛋白、醇溶蛋白和谷蛋白的4h消化产物半抑制浓度IC50值分别为1.45mg/mL、0.91mg/mL、1.19mg/mL和0.75mg/mL,分子量集中在1000u以下,是易于被人体吸收的ACE抑制活性肽。同时,未经酶解的蛋白几乎没有ACE抑制活性。结果说明大米四种蛋白的体外消化酶解物具有不同大小的ACE抑制活性,其中大米谷蛋白消化产物的ACE抑制活性最高,人体正常食用大米蛋白,经胃肠消化可以产生被人体吸收的ACE抑制活性肽。     

热处理对丙二醛氧化米糠蛋白体外胃蛋白酶消化性质的影响

采用不同浓度的丙二醛氧化米糠蛋白,通过95℃水浴热处理氧化米糠蛋白,研究热处理对丙二醛氧化米糠蛋白体外胃蛋白酶消化性以及消化产物抗氧化性的影响。结果表明:随着丙二醛浓度的增加,米糠蛋白羰基和二硫键含量增加,游离巯基含量下降,证实丙二醛致米糠蛋白氧化。随着丙二醛浓度增加,米糠蛋白体外胃蛋白酶消化率、初始消化速率和消化产物中分子质量分布在500～1 500 u的活性肽含量均逐渐下降。同时,米糠体外胃蛋白酶消化产物ABTS~+·,DPPH·,·OH和O_2~-·清除能力、金属螯合能力以及还原能力持续下降。热处理可提高米糠蛋白的体外胃蛋白酶消化率、初始消化速率以及消化产物中活性肽含量和抗氧化性。结论:丙二醛氧化可降低米糠蛋白的消化性以及消化产物的抗氧化性,适当的加热处理可在一定程度上增强米糠蛋白的消化性以及消化产物的抗氧化性。     

脂质体外消化过程中氧化评价模型与检测方法研究进展

脂质是人体所需三大营养素之一,其全摄入链的安全和健康特性备受重视。胃肠道内含有羟基、活性氮族等多种促氧化因子,使脂质在胃肠道消化过程中易产生氧化反应。体外模拟消化相比体内消化评价具有耗时短、无伦理问题等优点,是研究脂质胃肠道消化的优选方法。同时,考虑到人体消化道环境的复杂性和脂质的多样性,消化后脂质氧化状态的真实评价也尤为关键。在研究脂质消化过程以及脂质在消化道中的氧化状态时,需要将这些方法整合利用以求对相关问题进行全面性的探索。作者介绍了脂质在体内的消化过程和目前研究脂质常用的体外消化模型,阐述了脂质消化过程中氧化产物的检测方法,对于系统研究特定脂质消化过程中的氧化机理、氧化途径具有重要意义。     

6种富含α-亚麻酸食用油脂的主要组成成分及消化特征研究进展

α-亚麻酸(ALA)是人体必需脂肪酸,在维持人体正常生理活动中具有多重作用。旨在确定ALA在食用油脂中的物质基础与其功能的构效关系,实现精准的膳食脂质营养,对6种富含ALA食用油脂的总脂肪酸组成、甘油三酯中脂肪酸的位置分布情况、甘油三酯分子构成、脂质伴随物和消化特性等研究内容进行了总结和分析。6种富含ALA食用油脂主要脂肪酸组成为棕榈酸、硬脂酸、油酸、亚油酸、ALA,其中：紫苏籽油、亚麻籽油和牡丹籽油的ALA含量较高;不同富含ALA食用油脂甘油三酯中脂肪酸的位置分布存在显著差异,蚕蛹油的ALA主要分布在sn-2位,牡丹籽油和火麻仁油的ALA主要分布在sn-1,3位;不同富含ALA食用油脂甘油三酯的分子结构类型存在显著差异;富含ALA食用油脂的脂质伴随物主要为维生素E和甾醇,其中沙棘籽油的维生素E和甾醇含量均高于其余5种食用油脂;富含ALA食用油脂的消化程度和消化速率均低于非富含ALA食用油脂。     

食用植物油中4种不饱和脂肪酸在sn-2位含量分析

植物油的sn-2位不饱和脂肪酸比sn-1(3)位的不饱和脂肪酸更易被人体吸收,因此对食用植物油中sn-2位脂肪酸含量进行分析有实际意义。实验采用气相色谱法对油酸(C18∶1n9c)、亚油酸(C18∶2n6c)、γ-亚麻酸(C18∶3n6)、α-亚麻酸(C18∶3n3)等4种不饱和脂肪酸在10种共计12个食用植物油样品中总脂肪酸和sn-2位的具体含量进行检测。总脂肪酸中油酸(C18∶1n9c)含量最高的为花生油,为40.06 g/100g,而sn-2位油酸含量最高的是茶籽油,为1.11 g/100g。大豆油在总脂肪酸中含亚油酸(C18∶2n6c)最多,为68.49 g/100g,但在sn-2位中含亚油酸最多的是核桃油,为0.97 g/100g。sn-2位γ-亚麻酸(C18∶3n6)、α-亚麻酸(C18∶3n3)含量最高的则是亚麻籽油,分别为0.09 g/100g和0.32 g/100g。通过分析常见植物油的4种不饱和脂肪酸总量及在sn-2位上的含量,可为食用植物油的营养价值分析、相关的食品和保健品等产品研发提供科学的数据支持。     

脂质氢过氧化物氧化对核桃分离蛋白结构的影响

采用脂肪氧合酶催化亚油酸构建脂质氢过氧化物——核桃分离蛋白氧化体系,研究脂质氧化反应中产生的氢过氧化物对核桃分离蛋白结构特性的影响。结果显示,向100 m L 0. 05 mg/m L蛋白溶液中添加9 m L亚油酸,核桃分离蛋白溶解度下降至6. 89%,游离巯基含量由2. 82μmol SH/g下降至1. 92μmol SH/g,羰基含量由2. 26 nmol/mg增加至4. 23 nmol/mg,表明氧化后核桃蛋白理化特性产生变化。圆二色谱分析表明,蛋白质氧化导致核桃分离蛋白α-螺旋和β-折叠含量下降,β-转角和无规则卷曲含量上升。随着亚油酸添加量的增加,蛋白质氧化程度加大,核桃分离蛋白表面疏水性从429. 66下降到405. 24。内源荧光最大荧光峰位红移,内源荧光强度下降,此结果表明,脂肪氧合酶(lipoxygenase,LOX)催化亚油酸氧化诱导核桃分离蛋白聚集,并进一步使蛋白质二级和三级结构发生变化。体积凝胶色谱法结果显示,核桃分离蛋白氧化后,小分子多肽含量下降,高分子量聚集体含量增加,说明脂质氢过氧化物氧化修饰导致核桃蛋白结构改变,形成氧化聚集体。     

过氧自由基氧化对大米蛋白结构的影响

采用不同浓度2,2’-盐酸脒基丙烷(AAPH)在有氧条件下热分解产生的过氧自由基代表脂质氧化过程中的脂质自由基,研究过氧自由基氧化对大米蛋白结构的影响。结果表明,当AAPH浓度从0增加至25 mmol/L,大米蛋白羰基和二硫键含量分别由3.77和13.88 nmol/mg增加至7.26和15.73 nmol/mg,游离巯基由7.32 nmol/mg下降至1.97 nmol/mg,表明过氧自由基诱使大米蛋白发生了氧化;傅里叶红外分析表明蛋白质氧化导致大米蛋白α-螺旋和β-折叠含量下降,β-转角和无规卷曲含量上升。随着大米蛋白氧化程度的增加,大米蛋白粒径从126 nm增加到216 nm,表面疏水性从1053下降到568,内源荧光最大荧光峰位蓝移,内源荧光强度下降,并且在分子量分布图中高分子量聚集体含量逐渐增加。表明过氧自由基氧化修饰导致大米蛋白结构改变和形成氧化聚集体。     

中餐烹制工艺对鸡胸肉理化品质的影响

以新鲜鸡胸肉为研究对象,分别进行油炸、炒制、水煮和蒸制4种中餐烹制工艺处理,研究烹制工艺对鸡胸肉烹制损失率、质构、微观结构、电子鼻分析、氨基酸和脂肪酸组成的影响,并通过测定挥发性盐基氮（Total volatile basic nitrogen,TVB-N）和脂质过氧化产物（Thiobarbituric acid reactive substances,TBARS）分析烹制工艺对鸡胸肉蛋白质和脂肪氧化的影响,同时运用体外消化模拟方式研究了烹制前后鸡胸肉蛋白质消化率的变化。结果表明:油炸组鸡胸肉的烹制损失率最高;水煮组鸡胸肉的硬度值和TBARS值最高,分别为1531.55和6.01 mg MDA/kg;蒸制组鸡胸肉的TVB-N值最高,为11.00 mg N/100 g,且鸡胸肉肌节和肌纤维排列较为紧密;电子鼻分析显示4组鸡胸肉挥发性风味差异不显著（P>0.05）;油炸组鸡胸肉的氨基酸总量（31.89 g/100 g）和鲜味氨基酸含量（11.65 g/100 g）均为最高,且脂肪酸种类也最多;体外消化模型表明,油炸后的鸡胸肉胃蛋白酶消化率最高,为28.41%,而炒制后鸡胸肉的胃蛋白酶消化率最低,为8.59%。     

新疆打瓜籽油中亚油酸的尿素包合纯化工艺研究

采用尿素包合法纯化新疆打瓜籽油中的亚油酸,以产物的碘值和得率为评价指标,在单因素试验的基础上,对纯化工艺进行Box-Behnken响应面试验优化。结果表明,最优的纯化工艺条件为包合时间13 h、包合温度4℃、95%乙醇与尿素体积质量比4∶1、尿素与混合脂肪酸质量比3∶1,在最优工艺条件下产物的碘值(I)为146.14 g/100 g,得率为46.55%。采用气相色谱对产物进行脂肪酸组成分析发现,经过尿素包合后,绝大多数的饱和脂肪酸被除去,亚油酸含量明显升高,由原来的72.910%上升到97.249%。     

抗氧化肽在真空冷冻干燥过程中对乳双歧杆菌Probio-M8的保护作用

目的：探究乳清蛋白水解物经分离纯化获得的抗氧化肽HP3-2在真空冷冻干燥过程中对乳双歧杆菌Probio-M8的保护作用。方法：以10%海藻糖为基础冻干保护剂并添加5 mg/mL的乳清蛋白为对照组，以添加分离纯化的抗氧化肽HP3-2为试验组，分别与乳双歧杆菌Probio-M8按质量比1∶1.5混合，真空冷冻干燥后，使用平板计数法、流式细胞术、气相色谱质谱联用仪对乳双歧杆菌Probio-M8的活菌数、细胞膜脂肪酸组成、细胞膜流动性、细胞内外pH值、Na⁺浓度、细胞膜电位、细胞内ROS水平和脂质氧化产物丙二醛含量进行测定。结果：5 mg/mL抗氧化肽HP3-2能够提高乳双歧杆菌M8在真空冷冻干燥后的菌种存活率(80.40±3.34)%，显著高于含有乳清蛋白的对照组(64.69±2.47)%，同时还能够降低乳双歧杆菌Probio-M8胞内活性氧，使脂质氧化产物丙二醛的含量(2.14±0.06)nmol/mL显著低于WP组(2.30±0.05)nmol/mL和T组(2.33±0.05)nmol/mL，维持细胞膜电位和质子梯度，使细胞膜中的不饱和脂肪酸含量(51.49±1.2...     

Evaluation of lipid oxidation in spaghetti pasta enriched with long chain n−3 polyunsaturated fatty acids under different storage conditions

This study investigated lipid oxidation in spaghetti enriched in long chain n−3 polyunsaturated fatty acids (LC n−3 PUFA) by the addition to semolina of an integrator containing eicosapentaenoic acid and docosahexaenoic acid. Two oxidative parameters were evaluated: peroxide value (PV), to assess primary oxidation and oxidised fatty acids to quantify secondary oxidation products. Functional spaghetti had a shelf life comparable to control pasta. LC n−3 PUFA were not significantly implicated in the onset of oxidation in spaghetti stored under daylight and accelerated oxidation in a laboratory heater. Storage decidedly affected shelf life: PV in functional spaghetti increased from 7.1 to 43.4 meq O₂/kg of fat under light exposure over 12 months, and from 7.1 to 16.2 meq O₂/kg under accelerated ageing at 55 °C for 27 days, reproducing about 18 months at room temperature. Oxidised fatty acids increased in fortified spaghetti from 4.8 to 13.8 g/100 g of fat under light exposure over 12 months and from 4.8 to 7.8 g/100 g of fat at 55 °C in 27 days. The high sensitivity of spectrophotometric and chromatographic analytical methods permitted the evaluation of primary and secondary oxidative derivatives in small amounts of fat.     

Mechanisms of Oxidative Processes in Meat and Toxicity Induced by Postprandial Degradation Products: A Review

Antioxidant system loss after slaughtering, reactive species production, cell disruption, contact with oxygen and light, heme and nonheme iron, and irradiation starts up mainly by 2 related oxidative processes: lipid peroxidation and protein oxidation. Products generated in these processes are responsible for meat quality loss, and some of them are suspected to be toxic to humans. This review article is focused on reactive species implicated in oxidative processes in meat, on lipid peroxidation mechanisms, heme protein, and nonheme protein oxidation, and on some toxic oxidation and digestion products. Nonenzymatic fatty acid peroxidation is exemplified by an arachidonic acyl group, and the initiation of chain reaction can be described by 3 pathways: singlet oxygen, hydroxyl radical from the Fenton reaction, and perferrylmyoglobin. Enzymatic oxidation of fatty acids is exemplified using linoleic acid, and the main characteristics of lipoxygenase are also presented. Heme protein oxidation is described in an interrelation with lipid peroxidation and the significance for food quality is shown. For protein oxidation, 3 different mechanism types are described: oxidation of amino acid residues, oxidation of protein backbone, and reactions of proteins with carbonyl compounds from lipid peroxidation. The effects of oxidative damage on protein properties and bioavailability are also shown. At the end of each oxidative process, the postprandial toxicity induced by oxidation products and the dietary degradation products are presented. Also discussed are reports by some researchers who suggest that dietary lipid and protein oxidation products and heme iron from red meat are in part cytotoxic and/or genotoxic.     

Prooxidant Activity of Oxidized α-Tocopherol in Vegetable Oils

ABSTRACT:  The effect of oxidized α-tocopherol on the oxidative stabilities of soybean, corn, safflower, and olive oils and the oxidation of oleic, linoleic, and linolenic acids were studied. The 0, 650, 1300, and 2600 ppm oxidized α-tocopherol were added to soybean, corn, safflower, and olive oils and 10000 ppm oxidized α-tocopherol to the mixture of oleic, linoleic, and linolenic acids. Samples in the gas-tight vials were stored in the dark for 6 or 35 d at 55 °C. The oxidative stabilities of oils were determined by headspace oxygen with GC and peroxide value. Fatty acids were determined by GC. As the concentration of oxidized α-tocopherol in soybean, corn, safflower, and olive oils increased, the depletion of headspace oxygen and the peroxide values of oils increased during storage. The prooxidant effects of oxidized α-tocopherol on soybean and corn oils with about 55% linoleic acid were greater than those on safflower and olive oils with about 12% linoleic acid, respectively ( P  < 0.05). The changes of fatty acids during storage showed that the oxidation ratios of oleic, linoleic, and linolenic acids were 1 : 2 : 3, 1 : 12 : 26, and 1 : 8 : 16 after 5, 30, and 35 d of storage, respectively. The oxidation of α-tocopherol in oil should be prevented and the oxidized α-tocopherol should be removed to improve the oxidative stability of oils.     

豉香型白酒肥肉浸制产脂肪油及脂质氧化研究

以黑米、黑豆、黑木耳为原料,以木糖醇代替蔗糖,将黑米黑豆黑木耳混合液与牛乳共同发酵,研制一种低糖复合发酵乳,并采用单因素及正交试验优化其发酵工艺条件。结果表明,通过高温烘焙香气试验确定黑米、黑豆烘烤条件分别为160 ℃烘烤8 min、180 ℃烘烤10 min。低糖复合发酵乳的最佳工艺条件为黑米∶黑豆∶黑木耳=3∶2∶1（g∶g）,黑米黑豆黑木耳混合液∶牛乳=6∶4（V/V）,混合菌种（保加利亚乳杆菌∶嗜热链球菌=1∶2）接种量4.0%,木糖醇添加量8%。在此优化工艺条件下,低糖复合发酵乳的感官评分为94.2分,脂肪含量为3.6%,蛋白质含量为5.9%,酸度为79 °T,还原糖含量为5.2%,全乳固体为16.1%;乳酸菌数为1.91×106 CFU/g;未检出致病菌,符合相关国家标准。     

泡酒肥肉浸制过程中脂肪氧化和脂肪酸组成的变化

泡酒肥肉是豉香型白酒(玉冰烧)生产过程\     

Intake and performance of lactating cows grazing diverse forage mixtures

Twenty multiparous Holstein cows in midlactation grazed pastures of 4 forage mixtures in a 12-wk study repeated during 2 grazing seasons to determine if forage mixture complexity affected intake and productivity of lactating dairy cows. The forage mixtures were 1) orchardgrass plus white clover [2 species (SP)]; 2) orchardgrass, white clover, and chicory (3SP); 3) orchardgrass, tall fescue, perennial ryegrass, red clover, birdsfoot trefoil, and chicory (6SP); and 4) 6SP mixture plus white clover, alfalfa, and Kentucky bluegrass (9SP). Total herbage intake was similar among forage mixtures, averaging 12.0 kg/d across all forage mixtures and years. Milk production and composition were not affected by forage mixture or year, and averaged 34.6 kg/d, 3.4%, and 2.8% for milk production, milk fat percentage, and milk protein percentage, respectively. The conjugated linoleic acid content of milk fat was higher for cows that grazed the 3SP, 6SP, and 9SP mixtures than from cows that grazed the 2SP mixture (1.02 vs. 0.87 g of conjugated linoleic acid/100 g of fatty acids, respectively). Blood glucose, blood urea nitrogen, and nonesterified fatty acids were not affected by forage mixture and averaged 69.2 mg/dL, 13.4 mg/dL, and 277.5 μEq/L, respectively. The results of this study indicate that altering the forage mixture in pastures did not affect dry matter intake, milk production, or blood metabolite profiles of lactating cows. The use of complex mixtures of forages in grazing systems should not affect dairy cow performance.     

Effect of prickly pear and algarrobo pod syrup coatings on consumer acceptance and stability of roasted almonds

BACKGROUND: The objective of this study was to evaluate the oxidative stability of roasted almonds coated with prickly pear and ‘algarrobo’ pod syrups and the effect of these coatings on consumer acceptance. RESULTS: Prickly pear syrup had higher moisture, proteins, ashes and lipids, and lower carbohydrate content, than algarrobo pod syrup. Phenolics and antioxidant activity such as inhibition percentages of diphenyl picryl hydrazyl radical were higher in prickly pear syrup than algarrobo pod syrup. Roasted almonds had higher protein and lipid contents and lower total carbohydrates than coated almonds. Three main fatty acids detected in all almond products were palmitic (63.2 g kg^?1), oleic (727.0 g kg^?1) and linoleic (208.0 g kg^?1) acids. The overall acceptance means in roasted almonds, roasted almonds coated with prickle pear syrup and roasted almonds coated with algarrobo pod syrup were 6.83, 6.65 and 6.70, respectively, on a 9‐point hedonic scale. The peroxide and anisidine values increased in all products. The increase was higher in roasted almonds without coating. CONCLUSION: These results indicated that the syrup coatings provided protection against lipid oxidation in almond products. Prickly pear syrup showed better protection against lipid oxidation. Copyright © 2009 Society of Chemical Industry     

Changes in lipid composition,fatty acid profile and lipid oxidative stability during Cantonese sausage processing

Lipid composition, fatty acid profile and lipid oxidative stability were evaluated during Cantonese sausage processing. Free fatty acids increased with concomitant decrease of phospholipids. Total content of free fatty acids at 72 h in muscle and adipose tissue was 7.341 mg/g and 3.067 mg/g, respectively. Total amount of saturated, monounsaturated and polyunsaturated fatty acids (SFA, MUFA, and PUFA) in neutral lipid exhibited a little change during processing, while the proportion of PUFA significantly decreased in the PL fraction. The main triacylglycerols were POO + SLO + OOO, PSO (P = palmitic acid, O = oleic acid, L = linoleic acid, S = stearic acid), and a preferential hydrolysis of palmitic, oleic and linoleic acid was observed. Phosphatidylcholines (PC) and phosphatidylethanolamines (PE) were the main components of phospholipids and PE exhibited the most significant degradation during processing. Thiobarbituric acid values (TBARS) increased while peroxide values and hexanal contents varied during processing.     

Production and oxidative stability of a human milk fat substitute produced from lard by enzyme technology in a pilot packed-bed reactor

Residence time and time of production were investigated during the enzymatic production of a specific structured lipid/human milk fat substitute (SL-HMFS), on a kg scale, made from lard and soybean oil fatty acids, using a packed-bed reactor and short path distillation. There were no effects of residence time or time of production on C18:2 and C18:3 incorporation or on acyl migration in the sn-2 position. In addition, the SL-HMFS was compared to commercial human milk fat substitute (HMFS) regarding fatty acid composition, content of antioxidants and oxidative stability. Fats were stored at 60 °C for four days and the oxidative stability evaluated by analysis of peroxide value (PV) and volatile secondary oxidation products. SL-HMFS had a lower oxidative stability than did commercial HMFS products or lard, probably due to a lower level of tocopherol in SL-HMFS.