鲜榨橙汁中Vc的含量及稳定性研究

用直接碘量法测定鲜榨橙汁中Vc的含量,并研究了在不同存放条件下鲜榨橙汁中Vc含量的变化情况。结果表明,鲜榨橙汁中Vc含量较高,为51.27 mg/100 g;其Vc稳定性较高,避光、避氧冷藏10 h,Vc的保存率可为100%;同时,实验证明,用直接碘量法测定橙汁中Vc含量,其准确度与精确度均较高。     

不同加工方法对鲜乳中Vc含量的影响

研究了不同的加工方法对乳制品中Vc含量的影响。采用分光光度法进行测定,并比较了6种不同乳样中Vc的含量,从而得出最佳的鲜乳加工方法。结果表明：以超高瞬时灭菌法（UHT）对鲜乳中Vc的破坏最小,损失率仅为9.0%。     

抗氧化剂对控制猕猴桃加工中Vc损失的研究

研究了猕猴桃加工工艺中打浆工序对猕猴桃中的还原型Vc和氧化型Vc含量的影响及在打浆前添加抗氧化剂对控制打浆工序中猕猴桃Vc损失的效果。实验结果表明,打浆过程中损失的主要是还原型Vc。打浆前,在猕猴桃中添加抗氧化剂能提高Vc保存率;0.03%植酸与0.02%茶多酚组合可使猕猴桃还原型Vc保存率高达95.24%,总Vc保存率高达95.90%。     

不同处理措施对草莓汁加工过程中Vc保存率的影响

以新鲜草莓果实为原料，对草莓汁加工过程中的Vc含量变化及其控制方法进行了研究。结果表明，快速清洗有利于草莓果中Vc的保存；微波热烫较热水热烫的Vc保存率高；热压榨方式有利于保持草莓的Vc含量；草莓汁灭菌时采用90℃灭菌15min的效果最好，灭菌后快速冷却有利于草莓汁中的Vc保存。     

高压脉冲电场灭菌对木瓜果酒中维生素C损失的影响

研究了高压脉冲电场在不同电场强度和处理时间对木瓜果酒Vc损失的影响,还进一步比较了高压脉冲电场和热处理灭菌后的木瓜果酒的菌落总数和Vc含量的变化。结果表明,随着高压脉冲电场的电场强度的增大和处理时间的延长,木瓜果酒的Vc损失越来越大,35 k V/cm、400μs处理时,混合木瓜果酒的Vc含量下降了18.75%,而100℃热处理的Vc含量降低了79%;高压脉冲电场灭菌效果良好,与传统热处理相比,高压脉冲电场处理的木瓜果酒中Vc损失程度更小。     

陕北不同产地红枣VC含量的测定与比较

测定不同产地红枣中Vc的含量。利用2,4-二硝基笨肼比色法测定陕北各红枣主产区红枣中V。的含量。结果：每100g红枣中，Vc含量在2．64mg-69．7mg之间，含量差别较大。结论：佳县、清涧、米脂枣果Vc含量较高，横山、神木枣果Vc含量较低。     

番茄酱加工中还原型Vc与氧化型Vc变化的研究

研究了在番茄酱加工过程中Vc含量的变化,结果表明:经过蒸汽热烫后的番茄中Vc含量比热水热烫后的番茄中Vc含量要高;番茄打浆前加入0.08%TBHQ能有效控制Vc损失;真空浓缩有利于保持番茄酱Vc,通过正交试验得其最优条件为:真空度0.055kPa、加糖量2.0%、温度65℃;高压杀菌比常压杀菌更有利于番茄酱Vc的保存。     

牛羊乳不同菌种发酵前后Vc含量变化研究

发酵乳制品中含有丰富的维生素,是人体获取维生素的重要途径。本研究对牛羊乳经不同菌种组合发酵前后的Vc含量变化进行测定,以了解不同菌种组合在发酵过程中对Vc含量的影响,为提高发酵乳的营养价值提供科学依据。结果表明,牛羊乳中四种菌种发酵后Vc损失率最低的是Lb+St组;经Lb+St+La+BBR组合发酵后的Vc含量损失率最高。     

湘西原香醋抗氧化性研究

文章测定湘西原香醋中总酚、总黄酮含量,采用分光光度法研究了其抗氧化作用,并与Vc进行比较.结果表明,湘西原香醋中总酚含量、总黄酮含量分别达到2.212 mg/mL和1.623 mg/mL,除了在羟基自由基·OH和超氧阴离子·O2-体系中,其清除能力低于对照样Vc外,在清除DPPH·的体系中,样品的清除能力接近Vc,在还原能力体系中,其还原能力超过对照Vc.     

烹饪方法对叶菜中总酚含量和抗氧化活性的影响

研究水煮、清炒不同烹饪方法对生菜和紫甘蓝中总酚含量、抗氧化活性以及Vc含量的影响。结果表明:紫甘蓝具有较高的总酚及Vc含量,抗氧化活性亦优于生菜;生菜经水煮后总酚含量、Vc含量以及抗氧化活性均下降显著,经清炒后总酚含量及抗氧化活性保持较好,Vc含量下降显著;紫甘蓝经水煮以及清炒后总酚含量、Vc含量及抗氧化活性均下降显著。生菜、紫甘蓝抗氧化活性与总酚含量显著相关,抗氧化活性与Vc含量非显著相关。基于生菜和紫甘蓝生食脆嫩鲜香及营养成分保持考虑,建议生菜与紫甘蓝清洗切分后生食,生菜清炒次之,紫甘蓝水煮次之。     

面团发酵过程中蛋白质和VB6变化

蛋白质和B族维生素是面粉及其制品中的重要营养成分。通过对蛋白质含量和VB6含量的测定，发现4种分离蛋白在发酵过程中均成波动变化，而不同酵母添加量对VB6含量影响不大，但在整个发酵过程中的变化趋势受微生物生长和繁殖速度的影响上下波动。     

VITAMIN AND SELENIUM CONTENT OF RIBEYE CUTS FROM GRASS- AND GRAIN-FINISHED BISON OF THE SAME HERD

Individual ribeye cuts from 10 grass‐ and 8 grain‐finished bulls of the same herd were analyzed for vitamin and selenium content. Vitamin A, vitamin E, thiamin, vitamin B₆, vitamin B₁₂ and selenium concentrations of ribeye cuts from grass‐ and grain‐finished bulls were similar. Vitamin C and folic acid levels were not detectable in ribeyes from both groups. Ribeyes from grass‐finished bulls contained significantly higher quantities of β‐carotene (P < 0.0005) and niacin (P < 0.01) and significantly lower (P < 0.0001) quantities of riboflavin than those from grain‐finished bulls. Bison ribeyes from both groups were rich sources (>20% Daily Values) of vitamin B₁₂ and selenium and good sources (10–19% Daily Values) of thiamin, niacin and vitamin B₆.     

天然维生素E及其抗氧化机理

天然维生素E是人们最早发现的维生素之一,是非常重要的阻断自由基链式反应的抗氧化剂.本文综述了天然维生素E的来由、性质、来源以及具体的抗氧化机理.     

A RESEARCH NOTE DIETARY SUPPLEMENTATION OF VITAMIN E AFFECTS THE PEROXIDE VALUE OF SUBCUTANEOUS LAMB FAT

Lipid oxidation is a major problem causing flavor deterioration in meat products. The objective of this research was to utilize an iodometric peroxide value method (PV) to analyze the effects of dietary Vitamin E on lipid oxidation of subcutaneous lamb fat. Peroxide value analyses demonstrated lower lipid oxidation in the fat from animals fed 300 IU (7 days and 21 days) of Vitamin E than in the fat from animals fed diets supplemented with 15 IU (control) (P < 0.05). At 9 and II days of storage, PV analyses also demonstrated a greater rate of increase (P < 0.05) in lipid oxidation in fat from lambs fed control diets than in fat from animals fed 300 IU of Vitamin E. Results indicate that higher dietaty Vitamin E for either 7 days or 21 days antemortem reduced the rate and initiation of lipid oxidation in subcutaneous lamb fat.     

高维生素E小麦胚芽油涂抹食品的研制

本文介绍了以小麦胚芽油为原料,生产高VE含量涂抹食品的工艺、配方,及理化、卫生指标。     

VITAMIN E SUPPLEMENTATION EFFECTS ON COLOR AND LIPID STABILITY OF WHOLE AND GROUND LAMB

Crossbred wethers averaging 44.1 kg were fed a diet supplemented with 2000 IU α-tocopheryl acetate/day for 49 days. The controls received the same diet without supplement. Muscles from lambs supplemented with vitamin E contained higher concentrations of a-tocopherol than the controls (P<0.05). There were no differences between control and supplemented animals for myoglobin stabiliry of two muscle slices stored at 4C (P>0.05). Ground semimembranosus (SM)from supplemented animals exhibited higher "a" values and lower Hue angle values (P < 0.05) than meat from control animals at 6 days of storage and longer indicating enhanced color stability due to vitamin E. Vitamin E supplementation decreased lipid oxidation of ground SM at 3, 6, 9, and 12 days of storage at 4C (P < 0.05) and it partially stabilized color of ground lamb. Color stability of whole lamb slices was not affected by vitamin E supplementation.     

超高压杀菌对鲜榨猕猴桃汁中Vc含量变化的影响

探讨了超高压杀菌过程中压强变化对鲜榨猕猴桃汁中Vc含量的影响。实验结果表明，经超高压处理后猕猴桃汁中的总Vc保存率在85％以上，还原型Vc在83％以上，保存率远远高于热力杀菌技术。     

EFFECT OF ACTIVATED CHARCOAL ON WATER-SOLUBLE VITAMIN CONTENT OF APPLE JUICE

The effect of activated charcoals (0, 0.5, 1.0, 2.0 and 3.0 g/L of powdered and granular activated charcoals) on the content of several water-soluble vitamins in apple juice was studied. Apple juice samples with activated carbon added were mixed for 0 (control), 5, 10, 20, and 30 min, respectively. The content of water-soluble vitamins was analyzed by HPLC. Considerable reduction in ascorbic acid (Vit C), niacin, pyridoxine (Vitamin B₆), thiamine (Vitamin B₁) and biotin concentrations was found while there was a dramatic improvement in the color and clearness of apple juice. The highest decrement in water-soluble vitamins was obtained at 3.0 g/L powdered activated charcoal. Statistical analysis of the data showed highly significant differences (P |< 0.05, P < 0.01) in the water soluble vitamins, color and clearness of the apple juice samples between the dosages of activated charcoals but no significant differences induced by the mixing periods.     

SUPPLEMENTATION OF VITAMIN E TO BOVINE FEMALES IN "WHITE COW", MATURE BEEF, UPGRADING PROGRAMS

Forty cull cows were used to determine the effects of feeding supplemental dietary Vitamin E and a high-concentrate feedlot finishing diet on fresh meat retail caselife and oxidized flavor of roast beef from carcasses of such cows. They were either fed a feedlot finishing diet not supplemented with Vitamin E (control; N=8) or were fed a feedlot finishing diet supplemented with Vitamin E for 14, 28, 42 or 56 days (N=8 for each time-on-feed). During the feeding period, the 32 cows in treatment feeding groups had access to a total of 50,400 IU of supplemental Vitamin E; cows in the 14 day time-on-feed group received the highest daily dose (3,600 IU/day) and those in the 56 day time-on-feed group received the lowest daily dose (900 IU/day) of supplemental Vitamin E. On average, tissue α-tocopherol levels were increased from 2.39 μg/g (control) to 4.21–5.44 μg/g by 14–56 days of supplemental feeding. Supplemental feeding of dietary Vitamin E and a feedlot finishing diet had the greatest effect on the visual color and percent surface discoloration of top round and top sirloin steaks and had the least effect on the visual color and percentage surface discoloration of ground beef patties, tenderloin and strip steaks. Taste panelists were able to detect a slightly, but significantly, greater quantity of warmed-over flavor components in the control roast beef than in the roast beef from cattle fed supplemental dietary Vitamin E and a feedlot finishing diet.     

OCHRATOXIN A, HYDROXYMETHYLFURFURAL AND VITAMIN C LEVELS OF SUN-DRIED GRAPES AND SULTANAS

Ochratoxin A (OTA), hydroxymethylfurfural (HMF) and l ‐ascorbic acid (vitamin C) levels were detected in sun‐dried sultanas and raisins (Vitis vinifera L. cv. Sultanina). Ochratoxins produced by Aspergillus ochraceus, Aspergillus spp., Penicillium viridicatum, Penicillium cyclopium and Rhizophus spp. The main toxin of this group is OTA. It is nephrotoxic and immunotoxic. HMF can occur during nonenzymatic browning reactions that take the form of condensation reactions between amino acids and reducing sugars. It is known as a mutagenic and carcinogenic compound. The sultanas and raisin research samples were sun dried in the field and stored over a long period in the plant. Toxicological quality patterns evaluated for OTA and HMF levels were also evaluated. These are very important compounds for food safety. They are important critical control quality criteria of sun‐dried grapes. Vitamin C was examined because of sensitivity against physical and chemical factors such as oxygen, light, thermal treatments, alkali treatment and heavy metals, as well as being important for food labeling. The mean values of OTA in sultanas and raisins were 4.64 and 2.98 µg/kg, respectively. It is determined that the studied samples could be evaluated for safety limit of OTA, which is suggested by the European Community as 10 µg/kg. The HMF values of the samples were 5.50 and 33.57 mg/kg, respectively. The raisins were sun dried. The two types of samples without any pretreatment had a long sun drying period, and they showed higher mean of HMF level with content is had showed higher mean HMF level sultanas. The HMF content is with a critical control point for human health. The mean vitamin C levels of sultanas and raisins were 3.67 and 5.15 mg/100 g, respectively. The mean vitamin C values of sultanas were lower than those of raisins. It was estimated that alkali treatment could cause the destruction of l ‐ascorbic acid. The vitamin C content of sun‐dried grapes does not contribute much to nutrition.