苜蓿中维生素Ｃ含量测定及变化规律

在国家标准GB 6195-86《水果、蔬菜维生素C含量测定法(2,6-二氯靛酚滴定法)》方法的基础上,探讨不同制样方法对苜蓿中维生素C含量的影响以及不同部位、热烫时间、贮藏时间等条件下苜蓿中维生素C含量的变化规律。结果表明,手工研磨法制样测得维生素C含量高于组织捣碎法,但差异不显著(P0.05),且直接加浸提剂制成匀浆要显著高于匀浆后加浸提剂(P0.05);不同部位测定结果为叶片嫩茎;贮藏时间愈长,热烫时间愈长,维生素C含量损失愈多,因此,建议采摘后立即食用,若不能及时食用,低温贮藏2 d为宜;热烫时间最好能控制在3 min以内。     

番茄汁饮料维生素C稳定性的研究

以新鲜番茄果实为原料,研究了影响番茄汁加工和储藏过程中的维生素C稳定性的因素。结果表明:从加工过程来看,与正常清洗和慢速清洗相比,快速清洗方式更有利于保存番茄果中的维生素C;30%火力微波热烫60 s较热水热烫的维生素C保存率高;热榨较冷榨更有利于保持番茄汁中的维生素C的含量;添加剂的添加量对维生素C含量的影响采用L9(34)正交试验设计,其中,蔗糖对维生素C的变化影响不大,柠檬酸对其有显著影响,抗氧化剂对其有极显著影响。添加剂的最佳添加量为:0.03%植酸+0.03%EDTA,1.4‰柠檬酸,8%蔗糖;90℃灭菌15 min、灭菌后快速冷却有利于保存番茄汁中的维生素C;从保藏条件来看,利乐包较其它包装材料维生素C的保存率更高,储藏温度以冷室(15℃~18℃)条件为宜,储藏时间越短,番茄汁中维生素C的损失越少。     

鼓风干燥机制备黄瓜粉的工艺实验研究

探索了将鼓风干燥机用于制备蔬菜粉的可能性。以黄瓜为原材料,按照一定的工艺流程对其进行打浆、均质、干燥成粉,并进行鼓风干燥机的运行参数优化实验。结果表明:热烫温度在60～100℃区间内温度越高,热烫时间在2～12min区间内时间越长,黄瓜中的过氧化物酶(peroxidase,POD)和多酚氧化酶(polyphenol oxidase,PPO)越容易失活;当黄瓜汁浓度为500g/L,液厚度为5cm时,护色剂HA的添加量为300mg/kg,干燥箱内温度设定为70℃,干燥18h,制备的黄瓜粉粒径分布比较均匀,护色效果较好。     

热烫对真空油炸豌豆品质的影响

研究了热烫条件对真空油炸豌豆品质的影响,实验结果表明:最佳的热烫温度是95℃。热烫时间影响豌豆的色泽、松脆性、含水率、含油率、维生素C和叶绿素的质量分数。综合比较发现:热烫2 min,总体可接受性最好,而且真空油炸豌豆的含水率、含油率很低;超过2 min,含油率、含水率降低不是很明显,而且维生素C、叶绿素质量分数迅速降低。     

列车冷链快餐中莴苣菜肴烹饪方式、贮藏品质研究

"冷链快餐"是列车上主要的供食类型,但人们对于蔬菜菜肴的冷配送研究并不多。将莴笋作为研究对象,将莴苣经过油炒、微波和热烫三种烹饪方式包装后,贮藏于1℃和4℃条件下,放置7 d。观测其硝酸盐、亚硝酸盐、维生素C和菌落总数等指标的变化,研究不同烹饪方式和贮藏温度对莴苣菜肴贮藏时的品质影响。结果表明:1℃下能明显增加硝酸盐含量,但能明显减少亚硝酸盐含量,同时能减少菌落总数,维生素C受温度影响较小。各个指标均随着贮藏时间发生显著变化(p0.05)。三种烹饪方式中,热烫能减缓硝酸盐和亚硝酸盐的增加,减弱维生素C的减少,感官评价分数也高于微波和油炒。试验表明:最好选用热烫的烹饪方式贮藏在1℃下并缩短贮藏时间,尽早食用。     

热烫前处理对花椒芽品质特性的影响

该文以新鲜的花椒芽为原料，探讨热烫处理的温度和时间对花椒芽的色泽、营养及风味等品质的影响。结果表明，随热烫温度的升高和时间的延长，花椒芽的色泽变暗，绿度降低，维生素C和蛋白质等营养物质含量均呈下降趋势。热烫温度达到90℃,时间达到180 s后可有效钝化多酚氧化酶和过氧化物酶活性，叶绿素、维生素C和蛋白质含量在此热烫条件下的损失率分别为37.22%、53.14%、24.12%,此热烫温度和时间是花椒芽最佳热烫条件。随热烫温度的升高和时间的延长，特征麻味物质羟基-ε-山椒素和羟基-β-山椒素的含量先减少后增加，羟基-α-山椒素的含量则一直减少。90℃处理180 s时，羟基-ε-山椒素和羟基-β-山椒素的含量分别增加了14.07%、3.11%,羟基-ɑ-山椒素的含量减少了20.83%。花椒芽中风味物质主要分为酯类、烯烃类、酮类、醇类和醛类五大类，在热烫过程中其相对含量均呈无规律的变化，主要的风味物质烯烃类和酮类在最佳热烫条件下与未热烫处理组相比无显著差异(P>0.05)。该研究旨在为提升花椒芽在加工过程中的品质提供理论指导。     

蔬菜维生素C保留因子的研究

目的:通过比较不同蔬菜、不同烹调方法间维生素C保留因子(RF)的差异,探讨影响蔬菜维生素C保留因子的因素。方法:选取常见的12种蔬菜,以炒、炖、炸、蒸、焯、盐腌的方法进行烹调,分别记录烹调前后蔬菜的质量。采用GB/T5009.86-2003荧光法测定蔬菜烹调前后维生素C的含量,计算相应的质量保留因子(保留率)和维生素C保留因子(保留率)。结果:鲜豆类蔬菜,焯和炖的维生素CRF>75,两种腌制菜肴的维生素C保留率仅为5%。根茎类蔬菜的情况比较复杂,缺乏规律性。叶菜类蔬菜,炒较之焯更利于维生素C的保留,RF值在80左右。炒对于茄果类蔬菜不会造成维生素C损失较大,RF>70。结论:炸、盐腌、蒸的烹调方法使维生素C损失较大,炒的烹调方法的维生素C保留率较高;温度、时间、蔬菜的品种是影响维生素保留因子的重要因素。     

不同烹调方法及冷冻贮藏对食物中硒含量的影响

研究了不同烹调方法及冷藏对食物中硒含量的影响,结果表明,热烫、炖煮等不同处理均能引起蔬菜、菌藻类及肉类样品中硒含量的损失,其平均损失率为9.87%～28.7%。在-25℃冷藏一个月后,硒损失率为4.34%～12.2%。结论:不同烹调方法及冷藏能引起食物中硒含量的损失,损失程度:炖煮>热烫>冷藏,蔬菜类>菌藻类>肉类。     

厨房中,餐桌上 不能惯的六个毛病

蔬菜久存不吃由于种种原因,一些人习惯在周末到市场买菜,新鲜的蔬菜存在家里达一周时间甚至更久。蔬菜久存不吃,其中的维生素就会损失掉,比如将菠菜置于20℃的环境中一段时间,维生素C会损失达84％。如果蔬菜必须要在家里存放一阵子,您可以选择避光、通风、干燥的地方存放。烧菜时不加锅盖人们在烧菜时常常会忘记了盖上锅盖。据测定,盖住锅盖烧菜,蔬菜中的维生素B。只损失15－20％,如果不盖锅盖,维生素B。就会损失2－3倍;不加锅盖煮菜7分钟所损失的维生素C和盖了锅盖煮25分钟所损失的量一样多Z不加锅盖煮菜,蔬菜中的维生素A也…     

脱水甘蓝护色工艺研究

针对热烫对蔬菜颜色的影响,通过试验得出脱水甘蓝的热烫工艺条件为:pH8.5、温度95℃、时间为80s,在此条件下生产出的干燥产品护色效果最好。     

Application of thermal inactivation of enzymes during vitamin C analysis to study the influence of acidification,crushing and blanching on vitamin C stability in Broccoli (Brassica oleracea L var. italica)

The effectiveness of heat inactivation of oxidative enzymes e.g., ascorbic acid oxidase (AAO) to stabilise vitamin C during extraction and analysis was evaluated. The influence of different sequences of performing treatments including acidification (pH 4.3 vs. pH 6.5), crushing, high temperature short time (90 °C/4 min–HTST) and low temperature long time (60 °C/40 min–LTLT)) blanching on vitamin C stability in broccoli florets and stalks was also investigated. Heat inactivation of enzymes prior to matrix disruption resulted in higher vitamin C values mainly in L-ascorbic acid (L-AA) form, while lack of enzyme inactivation resulted in high vitamin C losses resulting from conversion of L-AA to dehydroascorbic acid. Various treatments and their sequence of application influenced vitamin C stability as follows: (i) crushing prior to blanching reduced vitamin C stability and (ii) in the absence of heating, acidification increased vitamin C stability (iii) blanching prior to crushing resulted in higher vitamin C retention, with HTST blanching retaining more vitamin C than LTLT blanching.     

热烫处理对南瓜叶化学成分及色泽的影响

为探明热烫处理过程中南瓜叶的品质变化,研究了蒸汽热烫、微波热烫及热水热烫对南瓜叶中VC、可溶性蛋白、叶绿素及草酸含量、过氧化物酶（peroxidase,POD）活性及色泽的影响。结果表明：3 种热烫方法对南瓜叶POD活性均有明显的抑制作用,蒸汽热烫可在60 s内使POD残余酶活力降低至7.10%,热水热烫对POD活性的抑制作用受温度影响较大,在95 ℃以上即对POD活性有明显抑制作用,此温度条件下热烫60 s,POD残余酶活力可降至4.85%;于微波功率480 W条件下热烫50 s,南瓜叶POD残余酶活力降至5.05%;经热水热烫的南瓜叶VC、可溶性蛋白含量最高,其次是微波烫漂,蒸汽热烫的最低;热水热烫的南瓜叶草酸含量亦较低,且L*值最大而a*值最小,即热水热烫的南瓜叶色泽最优。热水热烫是南瓜叶最适宜的热烫方式,其最适宜的烫漂条件为95 ℃、60 s。     

烫漂过程中荠菜过氧化物酶失活动力学模型研究

采用一级动力学模型、Weibull分布模型、Logistic模型对荠菜烫漂过程中过氧化酶失活动力学模型进行拟合。以决定系数（R2）、卡方（x2）、均方根误差（RMSE）、精确因子（A_f）、偏差因子（B_f）等为评价指标，分析模型的拟合效果。利用模型预测不同烫漂温度的烫漂工艺条件，同时以维生素C的含量为指标，评价不同烫漂工艺对维生素C含量的影响。结果表明:Logistic模型拟合烫漂过程中荠菜过氧化物失活动力学效果好，拟合精度高，拟合值与实测值偏差小，其决定系数R2为0.9980，x2为0.96×10?4，RMSE为0.0097，A_f为1.1304，B_f为1.0070。在过氧化物酶95%失活的条件下，依据Logistic模型预测，100 ℃下烫漂20 s，80 ℃下烫漂287 s，POD相对酶活在0.050±0.001之间；烫漂后维生素C含量也存在显著性差异，高温短时烫漂后的维生素C损失较少。POD失活动力学模型预测烫漂工艺条件，可以减少维生素C等热敏性营养成分损失。     

烫漂温度及空气炸时间对鲶鱼鱼皮品质的影响

为了解烫漂温度及空气炸时间对鲶鱼鱼皮品质的影响,本文研究了50、70、90 ℃烫漂后鲶鱼鱼皮的蒸煮损失率和热稳定性,在烫漂的基础上分别炸制2、4、6、8、10、12 min后对其水分、脂肪、脆度、横向弛豫时间（T₂）进行了测定,并对不同烫漂温度及其空气炸12 min的鱼皮微观结构进行了分析。结果表明:70 ℃烫漂的鱼皮蒸煮损失率为2.15%,热稳定性温度分别为121.97、146.88 ℃,在空气炸12 min时水分含量为2.89%,脂肪含量为10.85%,形变距离为0.13 mm;相比较50 ℃和90 ℃,70 ℃烫漂的鱼皮,蒸煮损失率适中,热稳定性较好,在空气炸12 min时,水分含量最低,形变距离最小,脂肪含量较低,结构均匀平整。由此可见,70 ℃烫漂下的空气炸鱼皮整体更利于后期产品的开发。     

莴笋烫漂过程中过氧化物酶失活动力学模型的建立

为有效预测一定时间、温度条件下的过氧化物酶活力,避免过度烫漂导致莴笋品质的损坏,本研究对75～95℃条件下莴笋烫漂过程中过氧化物酶失活的动力学特性建立数学模型。利用一级动力学模型和Weibull分布模型进行拟合,以决定系数(R2)和卡方(χ2)为评价指标,分析了两种模型的拟合效果。此外以VC含量为指标优化烫漂工艺条件,将模型应用于实际预测中。结果表明：Weibull分布模型的拟合效果较好,R2均大于0.9900,χ2均小于0.0024,高温短时条件下的VC含量损失较少。     

Evolution of antioxidant compounds in lime residues during drying

This work aimed at studying the effects of pretreatment, namely, hot water blanching, and hot air-drying (60–120 °C) on the evolutions of vitamin C, phenolic compounds, nomilin and limonin, which are potential bioactive compounds in lime residues during drying. Blanching was found to decrease both the antioxidant contents and activities of the residues due to thermal degradation and loss with the blanched water. During drying, nomilin and limonin contents first increased, probably due to the remaining enzyme activity after blanching. After this period, the amounts of both nomilin and limonin dropped rapidly, due to thermal degradation. Product temperature was found to be a major factor controlling the changes of limonoids and there was no direct correlation between the moisture change during drying and limonoid contents. During degradation of vitamin C and phenolic compounds, the amounts of both substances decreased as the product temperature increased and the moisture content decreased during drying. The amount of phenolic compounds correlated well with the total antioxidant activity and phenolic compounds were found to be a major contributor to antioxidant activity of the product.     

Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

The objectives of this work were to evaluate infrared (IR) dry blanching in comparison with conventional water blanching prior to hot air drying of mango to inactivate polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes, and to study its effect on color change and retention of vitamin C and β‐carotene. Mango cylinders were blanched under similar temperature–time conditions either by IR heating or by immersion in a water bath during 2 min at 90 °C (high‐temperature‐short‐time—HTST) or for 10 min at 65 °C (low‐temperature‐long‐time—LTLT). After blanching mango was hot air dried at 70 °C. PPO was completely inactivated during the blanching treatments, but AAO had a moderate remaining activity after LTLT treatment (～30%) and a low remaining activity after HTST treatment (9% to 15%). A higher retention of vitamin C was observed in mango subjected to IR dry blanching, 88.3 ± 1.0% (HTST) and 69.2 ± 2.9% (LTLT), compared with water blanching, 61.4 ± 5.3% (HTST) and 50.7 ± 9.6% (LTLT). All‐trans‐β‐carotene retention was significantly higher in water blanched dried mango, 93.2 ± 5.2% (LTLT) and 91.4 ± 5.1% (HTST), compared with IR dry blanched, 73.6 ± 3.6% (LTLT) and 76.9 ± 2.9% (HTST). Increased levels of 13‐cis‐β‐carotene isomer were detected only in IR dry blanched mango, and the corresponding dried mango also had a slightly darker color. IR blanching of mango prior to drying can improve the retention of vitamin C, but not the retention of carotenoids, which showed to be more dependent on the temperature than the blanching process. A reduction of drying time was observed in LTLT IR‐blanching mango.     

甘薯嫩叶中Vc在加工过程的变化

采用2,4- 二硝基苯肼比色法测定甘薯嫩叶中VC 含量,分析不同贮藏条件及干制、腌制、速冻、烹饪等不同加工方式对VC 含量的影响。结果表明：甘薯嫩茎叶中VC 含量高达26.48mg/100g;甘薯嫩叶采后营养价值随存放时间而递减,低温冷藏和冷冻均能降低其营养损失速度,在6℃下贮藏9d VC 含量为15.96mg/100g;干制及腌制对VC 有较大的损害。甘薯嫩叶的烹饪以适当的高温及尽可能短的时间为佳,在160℃、50s 下VC 残留含量为16.85mg/100g。烹饪过程中适当添加调味料如食醋和蔗糖,可以减少VC 的损失。     

Effects of water blanching on pea seeds.

Laboratory scale experiments were conducted to elucidate the main mechanisms responsible for changes in the proportions of ascorbic acid (AA) and dehydroascorbic acid(DHA) in peas during water blanching. Studies utilized hand-harvested peas from specially grown Dark Skinned Perfection (DSP), Swan and Swift cultivars. The influence of pea size/maturity, blanch time and damage to the pea were studied over the temperature range 35–97°C.
With increasing DSP pea size/maturity, the proportion of AA oxidized increased, and the proportion of AA leached into the water decreased when blanching between 45 and 65°C. Maximum AA oxidation occurred at 60°C and leaching became the prime mode of loss above 70°C. Leaching of AA from DSP peas increased almost linearly from 40 to 97°C.
Damaging peas by bruising and slitting the testa, induced enhanced AA oxidation below 60°C and allowed immediate leaching of vitamin C largely as DHA even at the lowest blanch temperatures. Results suggested that the oxygen content of the tissues was a factor limiting the amount of AA oxidation. Cultivars Swift and Swan contained higher proportions of DHA particularly in the testa tissues, and calculations indicated that greater proportions of vitamin C were leached as DHA. A negligible proportion of AA was oxidized and some 28% of the initial AA was leached into the water when undamaged DSP peas were blanched at 97°C for 1 min. Bruised plus slit peas lost significantly more AA than undamaged peas when blanched at 97°C. Further evidence indicated that the micropyle serves as a major pathway for leaching losses.