Effect of different blanching times on antioxidant properties in selected cruciferous vegetables

This study aimed to evaluate the effect of different blanching times on the antioxidant properties (antioxidant and free radical scavenging activities) and phenolic content of selected cruciferous vegetables. The study revealed that a 10‐min blanching time had a significant effect (p < 0.05) on the antioxidant properties and phenolic content of all the vegetables except for cabbage and mustard cabbage. The loss of antioxidant activity was highest in Chinese cabbage (40%) after 15 min of blanching, followed by cabbage (27%), Chinese white cabbage (19%), mustard cabbage (9%) and red cabbage (4%). Red cabbage had lost a total of 40% scavenging activity after 15 min of blanching followed by Chinese cabbage (38%), cabbage (36%), mustard cabbage (23%) and Chinese white cabbage (11%). Only Chinese cabbage showed an increase (p < 0.05) in total phenolic content after 15 min of blanching compared with other vegetables. Minimal heat treatment through blanching process is recommended to prevent the major loss of antioxidant properties and phenolic content in selected cruciferous vegetables. Copyright © 2005 Society of Chemical Industry     

Blanch Temperature/Time Effects on Rheological Properties of Applesauce

Peeled and cored ‘Idared’ and ‘Rome’ apples were blanched in water for 20, 40, and 60 min at 35°. 47°. 59°. 71°. and 83°C minor to making into applesauce by a conventional process each month from Nov. through March. USDA Consist meter values decreased as blanch temperature increased from 35° to 59°C and increased again from 71° to 83°C. There was little variation in flow behavior index (“n” values). Yield stress increased as blanch temperature increased from 35° to 59°C and decreased from 71° to 83°C. The consistency index (K) and serum viscosity were almost unchanged by blanching temperature but both decreased with increasing storage time of fresh fruit. Blanching apples at 59° to 71°C before making into applesauce gave substantially thicker sauces than unbalanced apples.     

Chemical and physical pretreatments of fruits and vegetables: Effects on drying characteristics and quality attributes – a comprehensive review

Pretreatment is widely used before drying of agro-products to inactivate enzymes, enhance drying process and improve quality of dried products. In current work, the influence of various pretreatments on drying characteristics and quality attributes of fruits and vegetables is summarized. They include chemical solution (hyperosmotic, alkali, sulfite and acid, etc.) and gas (sulfur dioxide, carbon dioxide and ozone) treatments, thermal blanching (hot water, steam, super heated steam impingement, ohmic and microwave heating, etc), and non-thermal process (ultrasound, freezing, pulsed electric field, and high hydrostatic pressure, etc). Chemical pretreatments effectively enhance drying kinetics, meanwhile, it causes soluble nutrients losing, trigger food safety issues by chemical residual. Conventional hot water blanching has significant effect on inactivating various undesirable enzymatic reactions, destroying microorganisms, and softening the texture, as well as facilitating drying rate. However, it induces undesirable quality of products, e.g., loss of texture, soluble nutrients, pigment and aroma. Novel blanching treatments, such as high-humidity hot air impingement blanching, microwave and ohmic heat blanching can reduce the nutrition loss and are more efficient. Non-thermal technologies can be a better alternative to thermal blanching to overcome these drawbacks, and more fundamental researches are needed for better design and scale up.     

Drying of Orthosiphon aristatus leaves: Mathematical modeling,drying characteristics,and quality aspects

The stage of maturity for Orthosiphon aritatus (OA) leaves revealed that stage I (young leaves) provided the highest bioactive compounds. Vacuum blanching (VB) for 75?s gave the highest sinensetin (28.4% increment) and eupatorin (21.0% increment) compared with heated water blanching (HWB). The modified Henderson model was the most suitable desorption isotherm model for the OA leaves. The VB and unblanched OA leaves were dried by different drying methods, including convection tray drying (CTD, 40–60°C), heat pump dehumidify drying (HPD, 40–60°C), mixed mode solar drying (64.6°C), and freeze-drying. Three-parameter model (TP) was the best model to explain all drying curves. The drying constant, K in the TP and activation energy were fitted to the Arrhenius model. Effective moisture diffusivities were increased with the VB, drying temperatures, and HPD. The highest specific moisture extraction rate was obtained from the VB and dried in the HPD at 60°C. The quality aspects of sinensetin (10.2% retention), eupatorin (10.7% retention), total phenolics, and antioxidant activity revealed the best quality for the OA leaves pretreated by the VB and dried in the HPD at 60°C and could reduce drying time by 44.8% compared with the CTD. The VB of the OA leaves and dried using the HPD at 60°C were recommended.     

Product formulation for ohmic heating: blanching as a pretreatment method to improve uniformity in heating of solid-liquid food mixtures

ABSTRACT:  The electrical conductivity of food components is critical to ohmic heating. Food components of different electrical conductivities heat at different rates. While equal electrical conductivities of all phases are desirable, real food products may behave differently. In the present study involving chicken chow mein consisting of a sauce and different solid components, celery, water chestnuts, mushrooms, bean sprouts, and chicken, it was observed that the sauce was more conductive than all solid components over the measured temperature range. To improve heating uniformity, a blanching method was developed to increase the ionic content of the solid components. By blanching different solid components in a highly conductive sauce at 100 °C for different lengths of time, it was possible to adjust their conductivity to that of the sauce. Chicken chow mein samples containing blanched particulates were compared with untreated samples with respect to ohmic heating uniformity at 60 Hz up to 140 °C. All components of the treated product containing blanched solids heated more uniformly than untreated product. In sensory tests, 3 different formulations of the blanched product showed good quality attributes and overall acceptability, demonstrating the practical feasibility of the blanching protocol.     

Polyphenoloxidase Activity and Color of Blanched and High Hydrostatic Pressure Treated Banana Puree

The effects of blanching and high hydrostatic pressure (HHP) treatments on natural flora evolution, polyphenoloxidase (PPO) activity and color of banana puree adjusted to pH 3.4 and water activity (a_w) of 0.97 were evaluated during 15 days storage at 25°C. Standard plate as well as yeast and mold counts of HHP treated purees were <10 CFU/g throughout storage. Blanching time was found to affect (P<0.05) puree color. HHP treatments retained the initial color of the banana purees. Longer browning induction times and slower browning rates were observed when a longer blanching time was combined with a 689 MPa pressure treatment. A residual PPO activity < 5% was observed in the puree when a 7 min blanch was followed by HHP treatment at 689 MPa for 10 min.     

热烫叶菜在冷链储运及微波复热过程中的品质变化

论文以上海青和菜心作为研究对象,探究了叶菜在热烫加工、冷链贮藏和微波复热过程中亚硝酸盐含量、硝酸盐含量、菌落总数、维生素C（Vc）含量等指标的变化。结果表明：因亚硝酸盐易溶于水,热烫处理能有效降低叶菜中的亚硝酸盐含量;冷藏过程前期叶菜中的Vc协助抑制亚硝酸盐增长,而冷藏后期随着Vc的消耗和微生物增长,亚硝酸盐含量逐渐增加,上海青和菜心在4 ℃分别冷藏5 d和4 d后亚硝酸盐含量仍能维持在4 mg/kg的安全标准内,而10 ℃冷藏的只能保证2 d内的安全性;微波复热过程由于水分散失导致硝酸盐和亚硝酸盐的浓度增加,因此复热过程应避免大面积敞口加热。本文探索了热烫叶菜在冷链储运及微波复热过程中亚硝酸盐的累积机理,为其应用于冷链盒饭提供理论依据。     

速冻加工过程中慈姑挥发性风味成分分析

为探讨速冻加工对慈姑风味的影响,采用顶空固相微萃取与气相色谱-质谱联用技术,分析烫漂和速冻加工处理过程中慈姑挥发性风味化合物的组分及变化。结果表明：慈姑烫漂和速冻处理后分别检测到33 种和29 种挥发性风味化合物。烫漂慈姑中相对含量较高的为烯类、含硫类、醚类、醛类和醇类等,二甲基硫醚、壬醛、辛醛、己醛、D-柠檬烯、柠檬烯、石竹烯、庚醇、泪柏醚等对烫漂慈姑风味有较大贡献;速冻慈姑中相对含量较高的为烯类、醚类、醛类、醇类和含硫类等,二甲基硫醚、壬醛、辛醛、己醛、庚醛、石竹烯、戊醛、庚醇、苯甲醛、2-戊基呋喃、泪柏醚等对速冻慈姑有较大贡献。慈姑经速冻后降低了对慈姑产生负面影响的风味化合物相对含量,如二甲基硫醚;增加了对风味有较大贡献的化合物种类,有利于风味化合物的保存和改善。     

不同热处理过程中鲜食甜玉米类胡萝卜素含量变化研究

为研究加工热处理对鲜食甜玉米中主要类胡萝卜素组分的影响,以晶甜5号鲜食甜玉米为原料,采用高效液相色谱法分析速冻甜玉米烫漂条件、罐装甜玉米预煮和灭菌时间对甜玉米中常见类胡萝卜素变化的影响。结果表明：速冻甜玉米烫漂处理相同时间,蒸汽烫漂甜玉米籽粒中类胡萝卜素含量高于沸水烫漂,且随着烫漂时间的增加,类胡萝卜素的含量在两种烫漂方式下均逐渐下降。对于罐装甜玉米,在20 min内,预煮时间越短总类胡萝卜素含量越高,随着预煮时间增加,仅α-隐黄质含量有所增加,其余均逐渐下降,但预煮时间超过20 min后,总类胡萝卜素含量无明显变化;在10 min内,灭菌处理可以显著提高总类胡萝卜素含量,随着灭菌时间的增加,总类胡萝卜素含量、各种类胡萝卜素组分含量均呈下降趋势。