猕猴桃酿酒过程中维生素C变化的研究

中华猕猴桃是近十几年来国际上迅速发展起来的一种新型水果。猕猴桃有很高的维生素C,具有很高的营养价值。我国有大量的野生猕猴桃资源,其果实以加工为主。猕猴桃酒是我国猕猴桃加工的一项重要产品。猕猴桃酒具有特殊的风昧,很受人们欢迎,新西兰利用达不到出口标准的猕猴桃果实加工的猕猴桃酒曾在欧洲举办的评酒会上获得过四次金奖,三次...     

猕猴桃香蕉果酱的研制

本试验以猕猴桃和香蕉为原料进行果酱的研制,通过对加工工艺的研究,探讨了甜味剂和增稠剂对产品品质的影响,确定了生产猕猴桃香蕉果酱基本加工工艺。通过设计正交实验,得出猕猴桃香蕉果酱最佳配比为:白砂糖添加量20%,麦芽糖添加量5%,三氯蔗糖添加量0.015%,黄原胶添加量0.3%。在此最优配方下测得可溶性固形物含量为45%,总酸含量为2.35g/100g,总糖含量为27.87g/100g,Vc含量为35.91mg/100g,微生物含量在国标规定范围内。制成的猕猴桃香蕉果酱口感细腻、香气宜人、营养丰富,组织形态好。     

猕猴桃胡萝卜复合果酱的研制

以猕猴桃和胡萝卜为原料,采用正交试验对猕猴桃胡萝卜复合果酱的工艺配方进行优化,并对产品中VC的保存方法进行研究。最佳工艺配方为:猕猴桃与胡萝卜质量比为1:2,白砂糖添加量为45%,柠檬酸添加量为0.3%,煮制时间为50min。最佳的VC保存方法为:猕猴桃切块后马上置于100℃的p H为3的柠檬酸溶液中热处理1min。在最佳的制备条件下,可制得营养价值高且口感独特的新型复合果酱。     

长白山野生软枣猕猴桃果酱的研制

本研究以长白山野生软枣猕猴桃为主要原料,通过正交试验研究野生软枣猕猴桃果酱的配方,得到最佳配方是:野生软枣猕猴桃果浆40%、白砂糖12%、黄原胶0.04%、柠檬酸0.06%。可制得颜色纯正、具有野生软枣猕猴桃特有滋气味、组织状态均匀一致的软枣猕猴桃果酱。     

软枣猕猴桃鲜果、果酒和果酱中氨基酸组分分析

为了更好评价软枣猕猴桃的营养价值,对软枣猕猴桃鲜果、果酒和果酱的氨基酸组分进行了分析比较。结果表明,软枣猕猴桃含有17种氨基酸,蛋氨酸+胱氨酸为软枣猕猴桃的第一限制性氨基酸,加工果酒和果酱中17种氨基酸的种类没有变化,含量略有降低,但氨基酸比值系数分值升高,说明加工后必需氨基酸的配比更加合理,更有利于人体吸收利用。     

软枣猕猴桃鲜果、果酒和果酱中氨基酸组分分析

为了更好评价软枣猕猴桃的营养价值,对软枣猕猴桃鲜果、果酒和果酱的氨基酸组分进行了分析比较。结果表明,软枣猕猴桃含有17种氨基酸,蛋氨酸+胱氨酸为软枣猕猴桃的第一限制性氨基酸,加工果酒和果酱中17种氨基酸的种类没有变化,含量略有降低,但氨基酸比值系数分值升高,说明加工后必需氨基酸的配比更加合理,更有利于人体吸收利用。      

维生素C和复合维生素中维生素C稳定性的比较研究

探究复合维生素中维生素C(CVC)的稳定性,对指导含复合维生素的食品体系中,提高维生素C(VC)的稳定性具有实际意义。本研究采用荧光分析法测定维生素C含量,比较CVC和VC在不同温度、pH值、金属离子、光照、氧化还原剂和碳水化合物等条件下的稳定性差异。结果表明,CVC相较于VC具有更强的耐热性、耐碱性和抗光照稳定性。氧化剂过氧化氢显著降低CVC和VC残留率,用体积分数2.7%的过氧化氢处理后,CVC和VC的残留率接近于0;不同浓度的抗氧化剂表没食子儿茶素没食子酸酯对提高CVC和VC稳定性不显著,而降低CVC稳定性的效果强于VC。金属离子对CVC和VC影响效果不一,Mg~(2+)和Zn~(2+)对CVC残留率影响较小,Fe~(3+)和Na~+影响较大;Na~+对VC残留率的影响较小,而Zn~(2+)的影响最大。低葡萄糖含量(≤5%)仅能提高CVC稳定性,而高葡萄糖含量(≥10%)可同时提高CVC和VC的稳定性。结论:CVC和VC表现出差异化稳定性,说明在食品加工过程中应根据添加维生素C的种类,调整相应的加工条件。     

苦瓜酒中维生素C测定方法的比较

采用紫外分光光度法(UV法)及高效液相色谱法(HPLC法)测定苦瓜酒中维生素C的含量。试验结果表明两种方法操作均简便、快速,但UV法的回收率偏小,HPLC法的回收率较高,结果准确,数据可靠,适用于苦瓜酒中维生素C的含量测定。     

挤压猕猴桃猪肉干维生素C损失预测模型研究

[目的]探索双螺杆挤压猕猴桃猪肉干中维生素C的损失规律,解决挤压过程中营养物质损失的“黑箱”问题。[方法]使用双螺杆挤压机生产猕猴桃猪肉干,采用高效液相色谱法测定物料挤压前后的维生素C含量,以平均停留时间作为物料在机筒内的反应时间,对不同挤压条件下维生素C损失率进行动力学分析。[结果]挤压过程中增大机筒温度和水分含量、降低螺杆转速和果干添加量会使挤出物维生素C损失率增大,平均停留时间与维生素C损失率变化规律基本保持一致,动力学分析表明挤压过程中维生素C损失遵循一级动力学模型,维生素C损失速率常数为0.003 54～0.006 05 s^-1。[结论]平均停留时间是影响维生素C损失率变化的重要原因,通过多元回归分析得到维生素C损失率的预测模型,可实现不同条件下维生素C损失率变化规律的合理预测,降低生产成本。     

黔野生猕猴桃果酱的制备及体外抗氧化性研究

该文旨在制备一款以黔产野生猕猴桃为主要原料的果酱并对果酱在体外的抗氧化功能进行初步的研究。通过单因素试验探讨白砂糖添加量、柠檬酸添加量、增稠剂添加量等工艺参数对黔产野生猕猴桃果酱质量的影响,从而确定黔产野生猕猴桃果酱基本加工工艺。通过设计正交试验,采用加权评分法与感官评价分析确定黔产猕猴桃果酱的最优工艺配比为白砂糖的添加量为50%,黄原胶0.6%+海藻酸钠0.6%,柠檬酸添加量0.5%。采用清除1,1-二苯基苦基苯肼(1,1-diphenyl-2-picryl-hydrazyl,DPPH)法对果酱在体外的抗氧化性进行测定,试验结果表明本试验中黔产野生猕猴桃果酱对DPPH自由基的IC50值为10.898 mg/mL,该果酱在体外具有一定的抗氧化活性。     

猕猴桃果酱加工中Vc损失及保护的研究

探索微波、真空浓缩技术等对控制猕猴桃果酱中猕猴桃Vc损失的效果.实验结果表明:微波热烫有利于猕猴桃Vc的保存,微波热烫80s已达到较好的软化效果,还原型Vc保存率为87.15%、总Vc保存率为87.76%,明显高于蒸汽热烫.真空浓缩果酱能保持猕猴桃自然的绿色,制品口感较常压浓缩果酱好,在真空浓缩条件为:真空度93.32kPa、加糖量1:0.8、浓缩温度90℃时,猕猴桃果酱还原型Vc保存率为83.47%、总Vc保存率为85.26%,分别比常压浓缩条件下提高了23.04%和7.06%.杀菌工序对果酱中Vc含量影响不大,高压短时杀菌有利于猕猴桃Vc的保存,还原型Vc和总Vc保存率分别为95.85%和95.64%.     

婴幼儿奶粉中维生素C检测方法的研究

目的 应用荧光分光光度计对婴幼儿乳品中维生素C的含量进行测定。方法 以婴幼儿奶粉为例, 依据国家标准GB 5413.18-2010《食品安全国家标准 婴幼儿食品和乳品中维生素C的测定》, 应用日立F-4600型荧光分光光度计测定婴幼儿乳品中维生素C的含量。结果 线性方程为Y=457.79X 28.877, 相关系数为0.9993, 方法检出限为0.1 mg/100 g。在50 mg/100 g、100 mg/100 g 两个加标水平下, 加标回收率为91.8%~101.8%, 相对标准偏差为0.36%~0.85%(n=6)。结论 此方法操作简便, 线性良好是测定食品中维生素C含量的理想方法。     

Comparative evaluation of UV-HPLC methods and reducing agents to determine vitamin C in fruits

Vitamin C is one of the most important antioxidant supplied by fruits and vegetables. Therefore a reliable and easy method is needed for its determination. In this work, two UV-HPLC methods for the determination of ascorbic acid were validated and compared in strawberries, tomatoes and apples. In addition, two different reducing agents [dl-1,4-dithiotreitol (DTT) or 2,3-dimercapto-1-propanol (BAL)] were tried for differentiate dehydroascorbic acid and determine vitamin C. Reliability resulted satisfactory for the UV-HPLC methods in each fruit. UV-HPLC methods resulted linear up to 5 mg/100 g and the least detection and quantification limits were <0.18 mg/100 g and <0.61 mg/100 g, respectively. Precision, as relative standard deviation, ranged from 0.6% to 3.9% and the recovery between 93.6% and 104.4%. Although, the UV-HPLC methods resulted useful for the routine analysis of AA and vitamin C in fruits, the best reliability was achieved when using a C18 column and DTT as reducing agent. Moreover, it may be the UV-HPLC method of choice because it is the easiest and cheapest to perform.     

A comparison of the vitamin C content of fresh and frozen vegetables

This study, using vitamin C (ascorbic acid) as ‘marker’, allowed a direct comparison of the nutritional quality of fresh vegetables at various stages of distribution and storage, with the same vegetable commercially quick-frozen and stored deep frozen for up to 12 months. The nutrient status of frozen peas and broccoli was similar to that of the typical market-purchased vegetable and was superior to peas that have been stored in-home for several days. Fresh peas and broccoli retained their quality for up to 14 days when stored under chill conditions. The nutrient status of frozen whole green beans and frozen carrots, with no loss on freezing, was similar to the fresh vegetable at harvest. Frozen spinach also compared reasonably well with the harvested fresh vegetable and was clearly superior to all market produce.     

pH梯度法制备维生素C脂质体

制备维生素C脂质体,并考察其包封率的影响因素。采用pH梯度法制备维生素C脂质体,以紫外分光光度法和粒度仪分别测定脂质体的包封率和粒径,并考察外水相pH、超声时间、载药温度及药脂比对包封率的影响。结果显示包封率随外水相pH的降低而增加,最佳超声时间为15 min,随着载药温度的增加包封率有提高的趋势,最佳药脂比为1∶5。该条件下pH梯度法制备的维生素C脂质体的包封率为(49.79±1.6)%(n=3),平均粒径为(118.3±9.6)nm。     

气相色谱法测定食品中丙酸盐的方法改进

建立样品处理使用凯氏定氮仪进行蒸馏,提高磷酸浓度,采用毛细管气相色谱法进行检测,降低初始柱温,优化升温程序测定食品中丙酸的含量。本法在丙酸10μg/m L~250μg/m L范围内,呈良好的线性关系,相关系数r大于0.9999,精密度试验相对标准偏差(RSD)0.24%,样品重复性试验相对标准偏差(RSD)2.39%,方法的加标回收率87.88%~103.31%,以S/N=3确定检出限,方法的检出限0.003g/kg,满足检测要求。     

Technical note: A comparison of methods to determine pH in silages

The techniques used to assess pH in silages vary greatly. The aim of this study was to evaluate the effects of water-to-sample ratio, extraction procedure, and standing time on pH determination. Silage samples (n = 20 for each silage) were chosen to represent diverse crops (corn, elephant grass, sugarcane, and forage peanut) to have a varied ensilability index and thus a wide range in final pH. Three water-to-sample ratios and 2 extraction procedures were used to measure pH at 0, 5, 10, 15, 30, 60, and 120 min of standing time. The ratios (undried silage to water) were 9:60, 25:100, and 30:270. The samples with the first 2 ratios were manually extracted, using a glass beaker and a glass stirring rod. The samples with the 30:270 ratio were extracted by using a stomacher blender for 4 min at 200 rpm. An electrode was used to perform pH readings. Dry matter (DM), water-soluble carbohydrates, and lactic acid concentrations were determined. The experimental design was completely randomized using a mixed repeated-measures model. Mean separation was performed using the Tukey test at P < 0.10 using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). The DM concentrations ranged from 24.5 to 40.2, 15.8 to 25.9, 26.9 to 30.6, and 17.8 to 21.4% for corn, elephant grass, sugarcane, and forage peanut silages, respectively. The lactic acid concentrations ranged from 2.9 to 10.1, 1.8 to 4.4, 0.7 to 11.4, and 0.3 to 1.4% of DM for corn, elephant grass, sugarcane, and forage peanut silages, respectively. The pH values measured by the 9:60 method were greater than other techniques at any standing times. The pH values from the 25:100 and 30:270 methods did not differ for elephant grass and forage peanut silages at any standing times. However, the 30:270 method had greater pH values for corn and sugarcane silages than the 25:100 technique at any standing times. The pH values measured by the 30:270 method did not vary for any of the silages according to standing time. Nevertheless, the pH values of the 25:100 method were greater from 0 to 10 min than for other standing times for all silages. Thus, for this method, there was pH stabilization from 15 min of standing time on. Overall, the 25:100 and 30:270 methods are recommended for assessment of silage pH. Fifteen minutes of standing time should be used for the 25:100 method but the pH reading can be performed immediately after mixing for the 30:270 technique.