Internal Modified Atmospheres of Coated Fresh Fruits and Vegetables: Understanding Relative Humidity Effects

ABSTRACT: Internal atmosphere modification in fruits and vegetables by surface film coatings depends on film permeability, coating thickness, and fruit surface coverage. Research in this area has been mostly empirical, with unpredictable results and diverse conclusions. To reduce variability, it is necessary to have a better understanding of factors that may influence the response of coatings applied to fruits. One factor is relative humidity (RH), which is known to affect the permeability of biopolymer films. By using steady-state mathematical models as tools, we hypothesize that fruits coated with hydrophilic films will be largely influenced by the RH of storage conditions. For hydrophobic materials, RH would have less influence on coating performance.     

Internal Modified Atmospheres of Coated Fresh Fruits and Vegetables: Understanding Relative Humidity Effects

ABSTRACT: Internal atmosphere modification in fruits and vegetables by surface film coatings depends on film permeability, coating thickness, and fruit surface coverage. Research in this area has been mostly empirical, with unpredictable results and diverse conclusions. To reduce variability, it is necessary to have a better understanding of factors that may influence the response of coatings applied to fruits. One factor is relative humidity (RH), which is known to affect the permeability of biopolymer films. By using steady-state mathematical models as tools, we hypothesize that fruits coated with hydrophilic films will be largely influenced by the RH of storage conditions. For hydrophobic materials, RH would have less influence on coating performance.     

Advances in Edible Coatings for Fresh Fruits and Vegetables: A Review

Edible coatings are an environmentally friendly technology that is applied on many products to control moisture transfer, gas exchange or oxidation processes. Edible coatings can provide an additional protective coating to produce and can also give the same effect as modified atmosphere storage in modifying internal gas composition. One major advantage of using edible films and coatings is that several active ingredients can be incorporated into the polymer matrix and consumed with the food, thus enhancing safety or even nutritional and sensory attributes. But, in some cases, edible coatings were not successful. The success of edible coatings for fresh products totally depends on the control of internal gas composition. Quality criteria for fruits and vegetables coated with edible films must be determined carefully and the quality parameters must be monitored throughout the storage period. Color change, firmness loss, ethanol fermentation, decay ratio and weight loss of edible film coated fruits need to be monitored. This review discusses the use of different edible coatings (polysaccharides, proteins, lipids and composite) as carriers of functional ingredients on fresh fruits and vegetables to maximize their quality and shelf life. This also includes the recent advances in the incorporation of antimicrobials, texture enhancers and nutraceuticals to improve quality and functionality of fresh-cut fruits. Sensory implications, regulatory status and future trends are also reviewed.     

Design of Rigid Modified Atmosphere Packages for Fresh Fruits and Vegetables

A procedure was developed for designing rigid MA packages for fresh fruits and vegetables that takes into account the change in total pressure inside the package. The procedure was demonstrated by designing a package for kiwifruit using available data. Some practical considerations in designing MA packages such as time to reach steady-state conditions, variation in respiration rate, film permeability, and changes in temperature were included. Small deviations in respiration rate and permeability could lead to large variations in steady-state gas concentrations.     

果蔬可食性涂膜剂结构组分与功能的研究进展

随着人们绿色消费和环保意识的增强,可食性涂膜剂成了国内外学者研究的热点,其添加剂成分也向天然、可食的方向发展。文中综述了果蔬可食性涂膜剂结构组分与功能的研究进展,包括多糖类膜、蛋白质膜和脂质膜,以及添加于可食性涂膜剂中的抗氧化剂、杀菌剂和其他助剂的研究情况。     

水果可食保鲜膜的应用选择

介绍了可食膜的发展概况、在水果中应用可食膜进行短期保鲜所存在的问题,并从保鲜膜本身的气体渗透性、果蔬组织的扩散性、果内气体组成成分等三个方面的计算和测量着手,阐述了得到可食膜保鲜最佳效果的方法。     

Modified Atmosphere and Modified Humidity Packaging of Fresh Mushrooms

Sorbitol and sodium chloride were used to modify the in-package relative humidity (IPRH) of fresh mushrooms (water irrigated and CaCl₂ irrigated) stored in a modified atmosphere package (MAP) at 12°C. No differences were observed for maturity index and microbial population between mushrooms stored in modified atmosphere package (MAP) with or without moisture absorbers. Lower IPRH was observed in packages containing water irrigated (normally grown) mushrooms with sodium chloride, but resulted in over-drying of mushrooms and did not improve color. Normally grown mushrooms with 10 and 15g sorbitol had the best color. IPRH of 87–90%, within 9 days storage was considered optimum. No improvements in quality were found with moisture absorbers with normally grown mushrooms. However, a small amount of sorbitol helped to avoid condensation with CaCl₂ irrigated mushrooms.     

Oxygen Barrier Properties of Whey Protein Isolate Coatings on Polypropylene Films

Oxygen permeation characteristics of whey protein isolate (WPI) coatings on polypropylene (PP) films were investigated to examine the feasibility of WPI coating as a novel biopolymer oxygen barrier for food packaging applications. Heat‐denatured aqueous solutions of WPI with several plasticizers including glycerol, sorbitol, sucrose, propylene glycol, and polyethylene glycol were applied on the surfaces of PP films previously treated with corona discharge. Among plasticizers used, sucrose conferred the best oxygen barrier property to the WPI‐coated films. Oxygen permeability (OP) of the resulting WPI‐coated films increased significantly with temperature, showing very good agreement with the Arrhenius model. OP of the coated films also increased exponentially with relative humidity.     

乙醛蒸气处理对果蔬贮藏特性的影响

综述了乙醛蒸气处理对果蔬采后生理如后熟软化、乙烯合成、呼吸作用、风味色泽等方面的影响 ,还介绍了乙醛处理对果蔬采后病害的控制     

塑料包装袋保鲜果蔬的研究

本文对果蔬的生理特征、保鲜机理和保鲜技术进行了比较系统的研究。结果表明，适宜的塑料包装袋可以延缓果蔬衰老、减少失重率、延长果蔬贮藏期、维持良好的贮藏质量和降低果蔬的变质率。     

我国果蔬气调保鲜技术及装备的现状及发展趋势

气调保鲜包装技术是可延长果蔬等易腐败产品的重要技术。对国内外果蔬气调保鲜包装技术及装备的发展动态进行了研究,分析了气调保鲜各领域技术和装备的研究现状,尤其针对我国农业发展的现状,为我国果蔬气调保鲜技术及装备的进一步发展研究提供了参考。     

Peanut and Walnut Rancidity: Effects of Oxygen Concentration and Relative Humidity

Accelerated tests for oxidative rancidity of blanched peanuts, blanched dry-roasted peanuts, blanched oil-roasted peanuts and shelled Persian walnuts were performed at high and low oxygen content at controlled intermediate and low relative humidities. The results confirmed and quantified the importance of oxygen content, relative humidity and roasting process in the oxidative rancidity of peanuts and walnuts. There is a potential to extend shelf-life of roasted peanuts and walnuts by edible coatings with low oxygen permeability or nitrogen-flushing with oxygen barrier packaging. Static headspace chromatography was useful to monitor oxidative rancidity in walnuts and roasted peanuts.     

气调包装果蔬贮藏寿命预测

在分析气调包装果蔬生理特性的基础上,提出以干物质的分解量作为果蔬产品质量的控制指标,结合气调包装气体交换机理及包装内气体浓度的变化,建立气调包装果蔬的贮藏寿命预测模型。并对一樱桃果品气调包装进行其贮藏寿命的预测。     

Microbiological Quality and Safety of Fresh Fruits and Vegetables at Retail Levels in Korea

The aim of this study was to evaluate the microbiological quality and safety of fresh produce at retail level in Korea in order to periodically update information and establish available risks associated with consumption of fresh fruits and vegetables. The samples from different markets located in 3 provinces of South Korea were collected. The protocol in the Korean Food Standards Codex was applied and generic Escherichia coli, coliforms, aerobic mesophilic bacteria (AMB), and yeast and mold (YM) in 360 packaged and unpackaged fresh fruits and vegetables were analyzed. Presence of pathogens was examined using real‐time polymerase chain reaction (q‐PCR) after enrichment of samples. For all, the microbial counts ranged from 1.7 to 10.6 log cfu/g for AMB, 2.2 to 7.9 log cfu/g for coliforms, and 5.5 to 7.9 log cfu/g for YM. Three lettuce samples were contaminated by E. coli with a bacterial load ranging from 2 to 4 log cfu/g. Salmonella spp. were not detected in any fresh produce. Listeria monocytogenes, E. coli O157:H7, and Staphylococcus aureus were found in 1 (0.6%), 3 (0.8%), and 5 (1.4%) fresh produce samples, respectively. Bacillus cereus (50.3%) and Clostridium perfringens (13.3%) had the highest prevalence. These results indicate the need for employing strict control measures and developing preventive strategies to improve the quality and safety of fresh produce in Korea.     

The use of packaging techniques to maintain freshness in fresh-cut fruits and vegetables: a review

Browning and other discolourations, softening, surface dehydration, water loss, translucency, off-flavour and off-odour development, as well as microbial spoilage are some of the most frequent causes of quality loss in fresh-cut products. Nowadays, the use of innovative modified atmospheres and edible coatings stands out among other techniques in the struggle for maintaining freshness and safety of fresh-cut fruits and vegetables. A few studies have demonstrated the effectiveness of these techniques when applied to different fresh-cut commodities. However, treatment and storage conditions for fresh-cut fruits are still being largely explored to better keep their fresh-like quality attributes. This review discusses the recent advances in the use of innovative modified atmosphere packaging (MAP) systems to maintain freshness of fresh-cut fruits and vegetables. Furthermore, special attention is devoted to the development of coatings that can be used as a complement or alternative to MAP.     

Effect of Temperature and Relative Humidity on Drying Kinetics of Fresh Japanese Noodle (Udon)

The effects of temperature and relative humidity (RH) on the drying kinetics were investigated to identify the optimal drying conditions for Japanese noodle (udon). Drying of fresh udon was carried out under nine conditions involving three temperatures (20, 30 and 40°C) and three RHs (60, 70 and 80%) at a constant airflow. The apparent moisture diffusivities were determined using a diffusion model taking into account both the internal and external mass transfer resistances. The effect of RH on the apparent moisture diffusivity was found to be smaller than that of temperature, but could not be neglected. A modified Arrhenius-type equation of diffusivity involving a RH term was proposed and used for the calculation of moisture content with time. The proposed equation was found to be effective for representing the drying process of fresh udon.     

磁场在果蔬冷藏保鲜中的应用研究

目的:研究了磁场对果蔬冷藏的保鲜效果。方法:进行了有无磁场以及不同磁场强度下果蔬冷藏保鲜试验。通过感官评定、失水率变化、VC和Fe含量变化,比较分析保鲜效果。结果:果蔬在磁场作用下其失水率降低,VC和Fe损失减小。结论:磁场可应用于果蔬的冷藏保鲜中。     

真空低温油炸对果蔬营养成分的影响

对采用真空低温油炸技术制备的甘薯、马铃薯、胡萝卜、南瓜、苦瓜、苹果等果蔬脆片中的多种营养成分进行检测,并以甘薯为原料分析了真空低温油炸脆片与常压油炸薯片营养成分的差异。结果表明,膳食纤维以紫心甘薯脆片最高,为28.8g/100g;类胡萝卜素含量以红心甘薯脆片和胡萝卜脆片最高,分别为21.3mg/100g和19.6mg/100g;维生素C以马铃薯脆片和红心甘薯脆片含量最高,分别为26.2mg/100g和25.8mg/100g;微量元中素以钾、钙、磷的含量较高,铁和硒含量较低,变异系数:钾>钙>磷>铁>硒。真空低温油炸条件下,甘薯脆片中维生素C、蛋白质及钙、铁、磷等含量均明显高于常压油炸,其中维生素C的保存率约为36%,几乎是常压油炸的3倍;甘薯脆片中的粗脂肪含量只有常压油炸的36.1%。     

温度和相对湿度对采后葡萄浆果硬度的影响

本文研究温度和相对湿度对采后葡萄浆果硬度的影响,并建立了相应的预测模型。以酶反应动力学为基础了建立葡萄浆果硬度变化的基础模型,并进一步引入温度、相对湿度和水蒸汽压差对硬度的影响,对基础模型进行了修正,结果表明模型的预测值和实验测量值间吻合良好(R2=0.93601,E=4.72%)。     

海藻糖在果蔬食品中的应用

本文主要讲述了海藻糖的特性和在食品工业中的应用,重点研究了海藻糖在果蔬加工中的重要作用,并对其应用前景进行展望。