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Gastón Ares Claudia Lareo & Patricia Lema 《International Journal of Food Science & Technology》2008,43(9):1671-1677
The objective of the present work was to study the influence of both passive and active modified atmosphere packaging on sensory shelf life of butterhead lettuce leaves, stored at 5 and 10 °C. Results showed that the efficacy of active modified atmosphere with respect to passive modified atmosphere depended on the storage temperature considered. When stored at 10 °C, despite being subjected to different package atmosphere composition, lettuce leaves in active and passive modified atmosphere showed the same sensory deterioration rate and sensory shelf life. On the contrary, when stored at 5 °C, lettuce leaves in active modified atmosphere packages showed lower deterioration rate and higher sensory shelf life than those in passive modified atmosphere. Sensory shelf life of lettuce in modified atmosphere packages was estimated using criteria determined according to consumers' rejection to purchase percentage, which consisted on an improvement over more arbitrary criteria presented in most studies. 相似文献
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为解决生菜加工贮藏过程中出现的褐变问题,研究了结球生菜多酚氧化酶(polyphenol oxidase,PPO)动力学特性,分析了pH、温度及底物浓度等因素对PPO活性的影响,建立了结球生菜褐变的反应动力学方程。结果表明,结球生菜最适pH为8.0,最适温度为40℃。用Michaelis-Menten机理描述可得结球生菜PPO相应的动力学参数Km=0.0691mol/L,vmax=26.5957U/min。生菜叶片组织中的PPO活性较强,叶柄和茎部组织中的PPO活性差异不大,均低于叶片组织中的PPO活性,且结球生菜茎部切口处已经发生褐变的部分PPO活性为6.12U/min,远高于没有发生褐变的部分。 相似文献
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为建立不同温度下鲜切结球莴苣中单增李斯特菌生长模型,将单增李斯特菌接种到鲜切结球莴苣表面,并于不同温度下贮藏,获得其在4、8、16、24和32℃下的生长数据,选用Gompertz模型进行拟合,建立初级生长模型。在此基础上建立二级模型研究温度对初级模型中单增李斯特菌生长动力学参数的影响,并进行数学检验。结果表明,对最大比生长速率和延滞时间建立平方根模型,结果呈良好的线性关系,相关系数R2分别为0.977 2和0.984 7,所建立的预测模型能很好地描述不同温度下单增李斯特菌的生长动态。 相似文献
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不同清洗剂对鲜切豇豆品质的影响 总被引:2,自引:0,他引:2
将新鲜豇豆清洗切割后用苯甲酸钠(5g/L)、双氧水(50ml/L)、次氯酸钠(0.01%)溶液及蒸馏水浸泡5rain,蒸馏水作为对照,沥干后置于无菌托盘中37℃贮藏。通过测定贮藏过程中各处理豇豆的失重率、维生素c含量、亚硝酸盐含量、各种菌落数以及进行感官评价,研究相对最佳的清洗方法。结果表明:4种清洗剂对鲜切豇豆失重率的影响不大,维生素e含量呈现下降趋势,影响作用最强的为双氧水。双氧水对增加亚硝酸钠含量作用最强,对各种微生物的抑制作用最强,但不能保持豇豆的外观;次氯酸钠也能很好的抑制微生物的生长,同时可以保持鲜切豇豆的外观品质;苯甲酸钠也能在一定程度上抑制微生物的生长,但作用效果次于次氯酸钠。所以次氯酸钠应为鲜切豇豆最佳的清洗剂,可以在各种果蔬清洗剂中加入次氯酸钠以便更好的清洗果蔬。 相似文献
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Broccoli develops a fast senescence that deteriorates the nutritional quality of the product. In this work, a combined treatment with hot air and UV-C were applied to minimally processed broccoli florets to investigate their effects on the antioxidant system during storage at 20 °C. Application of UV-C and heat enhanced by approximately 13% the levels of total antioxidants immediately after treatment. These levels were lower than initials in both control and treated samples. Nevertheless, higher values (ranged from 12 to 50%) were also detected in treated samples during storage. In general, higher values of antioxidants were correlated with elevated levels of phenols (from 10 to 17%) and ascorbic acid (from 11 to 17%) in treated florets. The increment in the content of phenolics in treated broccolis was correlated to an increased phenylalanine ammonia lyase (PAL) activity. The combined treatment also affects the activity of enzymes involved in removal of reactive oxygen species. An increase of about 50% in superoxide dismutase activity was detected after treatment. During the first days of storage this higher activity was about 40%. Enzymes that remove H2O2 like catalase and ascorbate peroxidase showed an enhanced activity toward the end of storage. The combined treatment diminished the peroxidase (POX) activity approximately 60% after the treatment and near 50% after two days of storage, suggesting a minor role of this enzyme in detoxification of H2O2. In conclusion, combined treatment may contribute to enhance the protection against oxidative molecules not only by increasing levels of phenolics and ascorbic acid but also by enhancing the activity of enzymes involved in removing reactive oxygen species. 相似文献
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The optimal conditions of washing iceberg lettuce with acidified warm water to improve the hygienic and sensory product quality were determined with the aid of a central composite design. To determine the criteria of product quality, in the course of storage for 13 days at 4 °C lettuce was subjected every 2 days to sensory evaluation. The sensory values were found to correlate with the physical measurements of color (a* value) (R2=0.83) and texture (specific energy of deformation) (R2=0.77), respectively. Color, texture and overall visual quality correlated with product acceptability (R2=0.96, 0.97, 0.96, respectively). In the experiments of series I, the effect of temperature at washing (45–50 °C), pH (4–5) and treatment time (5–10 min) were investigated and the results were used for the construction of a model to describe the effects on color and texture and to define an area of sensory product acceptance. In series II the parameters were changed to ranges of temperature (45–50 °C), pH (4.6–6) and treatment time (2–5 min), and the effect on the reduction of bacterial counts within the area of product acceptance was defined. In that area reduction rates of total counts by 0.9–2.9 log cfu/g and Enterobacteriaceae by 0.8–3.0 log cfu/g were achieved. The initial germ- reducing effect was sustained until the end of storage for 7 days at 4 °C. At 50 °C, washing for 5 min at pH 4.93, the total bacteria and Enterobacteriaceae were reduced by 2.9 and 3.7 log cfu/g, respectively. The removal of the two groups of bacteria exhibited characteristic differences. Two independent experiments confirmed the reliability of the models. 相似文献
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In recent years, wet (washing, bleaching, etc.) and dry (abrasive, laser shaping, rodeo, etc.) operations applied on fashion denim products have become an important factor to increase the added value. However, these wet and dry processes applied to the denim products may have adverse effects on the strength of the fabric and other supplementary materials of denim products. For example, thread breakages affect the repair ratios and quality of products, which causes time and profitability losses in companies. The main objective of this study is to analyse how the types of washing affect the strength of the sewing threads that are commonly used in the production of denim trousers. In this study, 100% cotton denim fabric with a weight of 11.5 ounces and two different sewing threads were used. The fabrics are sewn as trouser legs with chain and lock stitch. Five different washes were applied to the trouser legs. The obtained data were evaluated in the R statistical program. As a result of the analyses made it is proven that the washing techniques used have an effect on the sewing threads’ tensile strength and elongation at break. The tensile strengths of lock stitch and chain stitch decrease averagely 35% and elongation at break of lock stitch decreases %22 and chain stitch decreases 29.8%. 相似文献
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新亚纸业集团制浆造纸废水主要是碱法全化学漂白麦草浆中段废水和碱法半化学麦草浆中段废水的混合废水,SS含量高,BOD/COD比值低,不易生化处理,并且水质变化很大.针对这种情况,选择水解酸化氧化沟工艺,在同一条沟中交替完成厌氧、好氧的过程,可得到较高的COD去除率,运行效果良好,运行费用较低.为改善碱回收状况和提高碱回收率,同时介绍了提高蒸煮质量所采取的措施. 相似文献
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Karin Hassenberg Christine Idler Eleanor Molloy Martin Geyer Matthias Plöchl Jeremy Barnes 《Journal of the science of food and agriculture》2007,87(5):914-919
Bacteria such as Escherichia coli and Salmonella spp. may cause serious problems for the quality maintenance of pre‐packaged lettuces. The aim of this study was to evaluate the bactericidal effect of ozonated water in the washing of iceberg lettuce. For this purpose an ozone generator was integrated into a commercial lettuce‐washing facility. Lettuce samples were removed from this process and analysed for mesophilic total viable count (TVC), E. coli, Salmonella spp., vitamin C and sugar content. The analyses were carried out either directly after washing or at the end of best‐before date (BBD), in which lettuces were stored at 4 °C for 6 days. Water samples were analysed for total organic carbon (TOC) content and pH. Through the addition of ozone to the wash water the quality of lettuce during storage time was unaffected while there was only a limited observed decrease in populations of microorganisms. Copyright © 2007 Society of Chemical Industry 相似文献
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Mst. Sorifa Akter Maruf Ahmed Jong Bang Eun 《International Journal of Food Science & Technology》2010,45(7):1464-1471
Dietary fibre components, hydration properties and antioxidant activities such as 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, reducing power, metal chelating and 2,2′‐azino‐bis,3‐ethyl‐benzo‐thiazoline‐6‐sulphonic acid (ABTS) radical scavenging activities of persimmon peel powders using different washing treatments (tap water at 20 °C and hot water) were investigated. Peel powder obtained from hot water‐washed peels (74.95 g per 100 g) had higher dietary fibre content than tap water‐washed (65.50 g per 100 g) and unwashed (60.99 g per 100 g) peels. The higher content of total phenolic and ascorbic acid were found in peel powder obtained from unwashed peels, whereas washed peels had more β‐carotene content. The EC50 values of scavenging DPPH and ABTS radical for peel powders obtained from unwashed, tap water‐washed and hot water‐washed peels were 75.44, 142.18 and 110.17 μg mL?1 respectively and 5.31, 5.34 and 5.39 μg mL?1 respectively. Therefore, hot water washing is recommended to obtain better quality products from persimmon peel for use as a fibre supplement. 相似文献
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臭氧协同气调包装对鲜切叶菜的保鲜作用研究 总被引:1,自引:0,他引:1
采用臭氧水处理鲜切大白菜,并进行气调包装贮藏,通过正交实验法分析相关生理指标与保鲜效果,主要研究了4℃贮藏期间菌落总数、失重率、细胞膜透性、多酚氧化酶活性、VC含量和感官品质的变化。实验结果显示:臭氧水处理结合气调包装能有效控制微生物数量,保护了细胞膜透性及降低了VC含量的损失,并对多酚氧化酶有抑制作用,感官品质优良,可使鲜切白菜在4℃条件下保藏至20d以上。极差分析表明:优化的工艺参数为1.44mg/L的臭氧水处理5min协同5%O2/20%CO2/75%N2的气调包装。 相似文献
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It is widely believed that natural antioxidants found in food are significantly lost during processing. Nevertheless, it was recently demonstrated that processed fruits and vegetables may retain their antioxidant activity. In the present work, the changes in the overall antioxidant properties as a consequence of fermentation of cabbage and/or heat treatment of cabbage juices and extracts were studied. Fermentation processes as well as heat treatment increased the initial values of antioxidant activity. While a decrease in the antioxidant potential of sauerkraut juice was found for short heat treatments, a partial recovery of these properties was observed by prolonging heating periods. The TLC analysis showed that during fermentation and thermal processes, some substances with reactivity towards Folin–Ciocalteu reagent, hence with possible antioxidant activity, were released. We demonstrated that in contrast to common expectation, typical culinary processing of cabbage increases its antioxidant potency. The gain in antioxidant activity of heated samples coincided with the formation of both F–C reagent reactive compounds as well as brown early Maillard reaction products. This information may encourage the consumption of heat processed cabbage, especially that the release of antioxidants during heating may prevent oxidation of other food components, e.g. fats. 相似文献