Effects of Holding Methods and Time on the Vitamin Contents of Five Tropical Leafy Vegetables

Five tropical leafy vegetables, Pterocarpus soyauxii (“oha”), Pterocarpus santalinodes (“nturukpa”), Gongronema latifolium (“utazi”), Corchorus olitorius (“ahihiara”) and Amaranthus hybridus (“green”) were held for four days at ambient condition using three different popular local methods used in the Southeastern states of Nigeria. Each leafy vegetable was divided into three lots. Lots I and II were unwrapped while lot III was wrapped with broad cocoyam leaves. The three lots were held under a shade. In addition, lot II was regularly taken outside to the open at nights where it was exposed to cool air and early morning dews. The vitamin contents of each leafy vegetable lot were analysed initially and on daily basis for four days. The beta carotene and ascorbic acid contents ranged respectively from 4.88 – 9.84 μg and 105.62 – 278.65 mg per 100 g of the leafy vegetable. The five leafy vegetables are fair sources of thiamin, riboflavin and niacin. There were losses in the vitamins as holding time increased, regardless of the holding method employed. The rate of loss of vitamins was highest in Lot I (the unwrapped leaves that were kept in a shade both day and night). The rate of loss of vitamins was lowest in Lot III (the wrapped leafy vegetables).     

Determination of Mineral Content in Commonly Consumed Leafy Vegetables

Vegetables used by the people of Assam (India) found to be highly nutritious to maintain general balance diet. Nutritional information is used increasingly by public agencies and agricultural industries to promote different traditional fresh product. The work aimed at determining few nutritionally important minerals (calcium, iron, magnesium, phosphorus, and potassium) in leafy green vegetables widely consumed in Assam. The objective of the present work was to examine the variability in the mineral content.     

水分含量对花生仁储藏过程中的品质影响研究

通过花生仁露空储藏与真空储藏的加速对比试验,研究了不同水分含量的花生仁水分活度、过氧化值、酸价的变化趋势,试验结果表明,初始湿基湿含量为5.15%的样品较其他样品具有更好的储藏特性,真空包装样品过氧化值在整个储藏期增加46.23%,酸价增加56.79%,/较其他水平样品增幅减少约60%以上.研究发现,花生仁的水分含量过...     

果蔬采后诱导抗病研究进展

诱导果蔬采后的自然抗病性能够防治贮藏过程中真菌病害,延长保鲜期,是果蔬采后生物防治技术的重要手段之一。能够有效诱导果蔬采后抗病性的因子主要有物理、化学、生物等,其机理是通过生态学和生理生化的变化来提高果蔬对病原菌的抗病性。文中综述了主要诱导抗病制剂在果蔬采后病害防治中的的应用效果、方式、机理与研究进展,并分析了采后诱导抗病研究中的存在问题和发展方向。     

热处理对果蔬贮藏品质和采后生理的影响及应用

热处理(35～50℃)是一种无毒、无农药残留的物理保鲜方法,可延长采后果蔬的货架期.本文综述了热处理方法,热处理对果蔬营养风味、色泽、硬度和失重等贮藏品质的影响,热处理对果蔬呼吸作用、活性氧代谢、膜脂过氧化和酚类物质代谢等采后生理的影响,及热处理技术在果蔬贮藏保鲜中的应用.提出了热处理在果蔬贮藏保鲜研究中存在的问题和进...     

发酵香肠的pH值、水分含量与水分活度(Aw)的关系及其对制品贮藏性的影响

对发酵香肠的 pH值、水分含量与水分活度 (Aw)的关系及其对制品贮藏性的影响作了初步的研究。结果表明 :水分活度的下降与 pH值及水分含量均是呈直线关系 ,随制品 pH和水分含量的降低 ,水分活度逐渐下降 ,但 pH值对水分活度的影响较小 ,水分含量影响较大。香肠的 pH值、水分含量和水分活度值越底其贮藏稳定性越高。     

Osmotic Dehydration of Tropical Fruits and Vegetables

Because of the microstructural complexity of plant tissue, osmotic dehydration cannot simply be explained as a pure osmotic process in which cell membranes act as a semipermeable barrier allowing water to pass through. Instead, osmotic dehydration is considered a process in which many simultaneous mechanisms, acting at different levels, are responsible for mass transport. Different compositional and structural profiles are induced in fruits and vegetables, depending on process variables and the tissue microstructure. Compositional-structural profiles that are developed with gas-liquid exchanges in the tissue during osmotic process have a significant impact on physical (optical), textural and chemical properties (e.g., flavour profile) of the final product, which is in part influenced by the differences in the number of cells that are altered and unaltered during the treatment. This review focuses on changes in the physical, chemical, and cellular structure of fruits and vegetables, some technologies commonly applied to increase mass transfer during osmotic dehydration (OD), potentials and industrial applications of OD, and the challenges of osmo-drying technology.     

Improvement of Water Status Methodology for Leafy Vegetables Reduces Consumption of Time, Skilled Labor, and Laboratory Resources

When determining the water status of leafy vegetables with oven-drying techniques, consumption of time and resources is inevitable. The aim of this work was to evaluate the performance of both relative water content (RWC) and free water and bound water content (FW–BW) techniques to obtain the water content index (WC) of different leafy vegetables in order to dispense with the traditional methodology for water content determination. By doing this, not only consumption of time is reduced, but also skilled labor and laboratory resources. Butterhead lettuces harvested at different growing stages and stored at different postharvest conditions were evaluated. In all cases, water content values obtained with RWC technique were statistically equivalent to those obtained with the traditional methodology. Instead, water content values obtained with FW–BW technique were considerably higher than the original WC. Consequently, using RWC technique data to obtain water content, the time required to determine water status in butterhead lettuce is reduced by 25%. In addition, fresh plants of swiss chard, akusay (chinese cabbage), and romaine lettuce were evaluated in order to validate the simplified methodology. Results obtained were similar to those observed for butterhead lettuce.     

Influence of Water Stress on Cold-Induced Sweetening in Leafy Vegetable, Brassica juncea L.

The occurrence of low temperature sweetening in Brussica juncen L., an apparently chilling-tolerant leafy vegetables, has been investigated in relation to the effect of water stress and postharvest age (i.e. fresh harvest vs previously stored samples). The magnitude of cold-induced sweetening in B. juncea leaves was estimated to vary from 10–145% relative to the corresponding nonchilled samples. Previously stored leaves showed greater tendency to accumulate sugars but was apparently less responsive to cold-induced sweetening than freshly harvested leaves. Water stress synergistically enhanced this low temperature sweetening response; markedly greater and/or faster accumulation of sugars occurred in leaves that were both chilled and stressed. The majority of the total sugar increase was attributable to non-reducing sugars.     

水分胁迫对冷藏韭菜叶片衰老和活性氧代谢的影响

与保水处理韭菜相比,对照(CK)韭菜冷藏期间,失水很快,遭受严重水分胁迫,其叶片叶绿素含量和色调角(hueangle)值显著降低。水分胁迫降低了韭菜抗氧化剂、类胡萝卜素和抗坏血酸含量,抑制了抗氧化酶特别是SOD(超氧化物歧化酶)和CAT(过氧化氢酶)活性,促进了H2O2和膜脂过氧化产物MDA(丙二醛)的积累。采后水分胁迫促进了冷藏韭菜衰老,其机制与水分胁迫促进活性氧代谢失调和膜脂过氧化有关。     

Quality of Frozen Cauliflower during Storage

A study was conducted on the changes occurring in vitamin C content in frozen cauliflower stored under different conditions. During storage at -22°C, 25% vitamin C was lost after 13 months and 62.2% after 30 months. An acceptable sensory quality was conserved for 10 months; after this time, a decrease began in the characteristic flavor. Storage in a display freezer did not affect vitamin C; however, storage with temperature fluctuations was very harmful, especially regarding sensory characteristics.     

水分对酵子储存品质影响的研究

酵子是中国人自己的传统发酵剂,在中国北方许多城市依旧使用。而酵子的研究却刚刚开始,水分是影响酵子储存品质的重要因素。制作10%、18%、30%、40%、46%不同水分含量酵子,分别测定其发酵力、pH及制作出的酵子馒头质构与白度,并作馒头感官评价。结果显示,高水分(30%、40%、46%)酵子储存品质不稳定,各项指标总体呈下降趋势;10%水分酵子因水分过低,品质虽稳定但各项指标偏低;18%水分酵子品质稳定,且各项指标优良。因此酵子储存的适宜水分为18%。     

粮食在贮藏过程中品质变化分析

分析了粮食在贮藏过程中生命力、营养成分变化的情况,同时以稻米、小麦与面粉、大豆为例,分析了贮藏过程中食用品质的变化。粮食在贮藏过程中发生霉变,可影响粮食籽粒的发芽率;粮食陈化以后,碳水化合物、蛋白质、氨基酸、脂类、酸性物质、维生素等都会受到不同程度的破坏,食用品质大大降低。     

米饭贮藏过程中的品质变化

研究了在封口和不封口条件下,米饭的硬度、粘性和感官品质变化.结果表明:先封口的条件下制得的米饭在贮藏过程中感官品质较好;随着贮藏时间的延长,米饭的硬度逐渐增加,粘性则逐渐下降,在贮藏过程中,室温解冻1.5 h测得的米饭的硬度高于微波加热1.5 min+冷却1.5 h的米饭,而粘性则低于微波加热1.5 min+冷却1.5...     

浓香型白酒在陈酿过程中的酒质变化

对白酒的感官指标、酒精度、理化指标（总酸、总酯）、卫生指标（甲醇、杂醇油）、固形物含量、色谱骨架指标、pH值、电导率等在陈酿过程中的变化趋势进行研究。结果表明,不同的酒体在陈酿过程中,质量（口感）都会有很大的改善,浓香型大曲原酒（原度）经过8个月陈酿之后各项指标最终形成一种动态平衡,口感更加绵柔,醇厚;浓香型大曲降度酒（45度）以及42度浓香型成品酒指标变化规律性不强,质量（口感）在陈酿3-4个月后,协调性、缔合性达到最佳效果;陈酿时间过长,新型白酒易产生水味,香料与酒精易分离;陶缸陈酿效果优于不锈钢大罐陈酿。     

包装猪肉贮藏过程中品质变化分析

以新鲜猪肉为研究对象,采用普通包装和真空包装两种方式进行包装,并于25℃条件下贮藏,重点研究包装猪肉在贮藏过程中的品质与肉中H2S含量、包装顶空H2S含量之间的变化关系。结果表明,随着贮藏时间的延长,包装猪肉的TVB-N值、菌落总数、普通包装顶空CO2含量均不断增大。并随着TVB-N的增加,包装猪肉中的含巯基(-SH)化合物含量增大,含巯基(-SH)的氨基在微生物的作用下,又进一步产生H2S,肉中H2S含量超过一定量时又迅速并扩散到包装顶空。使肉中的H2S含量降低,顶空H2S含量升高。     

温、湿度对贮藏苦荞品质的影响

本文研究了不同温、湿度条件下 ,贮藏不同时间后 ,苦荞籽粒中的游离脂肪酸、芦丁、叶绿素的变化 ,探讨了其作用机制。结果表明收获后的苦荞籽粒干燥至其水分含量 <14 % ,贮藏在Aw <0 .6 1相对干燥的低温环境中 ,利于品质保存。     

米发糕的储藏品质研究

以大米为原料,采用专用发酵剂制作米发糕,研究包装方式和温度对米发糕储藏品质的影响,为方便型米发糕的工业化生产提供技术参数。结果表明,储藏温度、包装方式对米发糕储藏品质有显著影响。储藏过程中米发糕菌落总数上升,结晶度、硬度、咀嚼度增加,弹性、黏聚性和水分含量降低,导致感官品质下降。CO2气调包装后低温度储藏有利于抑制水分损失和细菌繁殖,米发糕于-18℃储藏,菌落总数、水分变化缓慢。-18℃储藏米发糕的结晶度小于4℃储藏时的结晶度。气调包装有利于保持米发糕的质构特征。米发糕采用CO2气调包装后于-18℃储藏,使米发糕的保质期可达10天以上。     

小麦实仓储藏过程中杂质对微生物活动及储藏品质的影响

在小麦实仓储藏过程中,依据小麦入仓时不同落点、杂质含量及分布,将整仓小麦划分为非杂质区和杂质区,在两区域中进行定点定时取样,并检测所取样品的各类杂质含量、外部霉菌量及储藏品质指标,结果表明:在杂质区,当筛下物、麦皮和麦秸含量较高时,粮堆水分较高;筛下物、麦皮、麦秸等有机杂质携带的微生物较多,对小麦籽粒表面的霉菌量影响较大,而无机杂质则影响较小;杂质区的小麦储藏品质变化较快,随着储藏时间的延长,杂质区与非杂质区的脂肪酸值、过氧化物酶活性、发芽率存在显著性差异.