Chitosan based powder coating technique to enhance phytochemicals and shelf life quality of radish shreds

Minimally processed radish forms an important segment of the rapidly growing minimally processed industry worldwide. Radish shreds have a short shelf life thus necessitating the use of chemical additives. However, demand for natural preservatives in foods has increased. Chitosan is a natural antimicrobial biopolymer with a good film forming ability. Hence, it is used as an edible coating on whole and fresh cut fruits and vegetables. The present investigation explored powder coating technique using purified chitosan and chitosan lactate for shelf life extension of shredded radish. Macro perforated LDPE resealable pouches were used to pack the samples. Samples were stored at 10 °C for 10 d. Physicochemical characteristics, phytochemicals, antioxidant activity, respiration rate and color were analyzed periodically. The study also determined microbial load and sensory acceptability in the stored samples. Chitosan treated samples exhibited a lower degree of weight loss, respiration rate, titrable acidity, % soluble solids and higher content of phytochemicals, moisture, and pH compared with control samples. The treated samples also exhibited better sensory acceptability, lower exudate volume, lesser browning and lower microbial load compared to control. This indicated better potential marketability of the coated radish shreds. Chitosan powder coating could be used as an efficient technique for quality maintenance and shelf life extension of radish shreds with feasibility for large scale application.     

杨树冰核细菌溃疡病寄主抗病良种的筛选

通过良种区域品评调查和良种区域栽培试验结果表明、以抗病性、抗逆性、生长量和形质为综合评价．新选用材、绿化杨树抗病优良品种、品系：黑龙江省为 ６１３（银×中）、美黑 ３号（美杨×欧洲黑杨）、黑小 ２号（欧洲黑杨×小叶杨）：吉林省为白城２号（小叶杨×钻天杨）、白林３号（小叶杨×欧洲黑杨）、白林１号（白城２４ ×欧洲黑杨）和白城 ５号（小叶杨×钻天杨）；辽宁省为美洲黑杨与欧美杨杂交种的辽宁杨、辽河杨、盖杨。     

Grafting effects on postharvest ripening and quality of 1-methylcyclopropene-treated muskmelon fruit

In addition to managing soil-borne diseases in muskmelon (Cucumis melo L.) production, grafting with resistant rootstocks may impact fruit quality. The ethylene antagonist 1-methylcyclopropene (1-MCP) has been shown to extend shelf life of fresh muskmelon fruit. Postharvest characteristics of 1-MCP-treated melon fruit as affected by grafting, however, have not been well examined. This study was conducted to explore the influence of grafting with different rootstocks on ripening and quality attributes of 1-MCP-treated muskmelon fruit during postharvest storage. Grafted ‘Athena’ muskmelon with two commercial squash interspecific hybrid rootstocks including ‘Strong Tosa’ and ‘Tetsukabuto’ as well as non-grafted and self-grafted ‘Athena’ were grown in replicated field plots at the University of Florida Plant Science Research and Education Unit (Citra, FL, USA) during April–June 2010. Half-slip fruit from two harvests were treated with 1.0 μL L⁻¹ 1-MCP (18 h, 20 °C) and analyzed during storage at 13 °C. For fruit from the 27 May harvest, whole fruit and mesocarp firmness, titratable acidity, soluble solids, and ascorbic acid content were measured, while production of ethylene and CO₂ was determined on fruit from the 29 June harvest. Grafting did not show a significant impact on fruit yield but affected the fruit shelf life significantly. Fruit from non-grafted ‘Athena’ and ‘Athena’ grafted onto ‘Strong Tosa’ demonstrated a shelf life of 31 d for the first harvest and 22 d for the second harvest. Shelf life of fruit from self-grafted ‘Athena’ and ‘Athena’ grafted onto ‘Tetsukabuto’ declined by 6 d and 3 d for the first and second harvest, respectively. Whole fruit firmness decreased by approximately 15.5% on average from 13 to 31 d except day 19 as a result of grafting, but to a lesser extent with ‘Strong Tosa’ rootstock. Mesocarp firmness of grafted melon was reduced by about 30.2% at days 13 and 19 compared to non-grafted ‘Athena’ fruit. In contrast, titratable acidity, soluble solid content, and ascorbic acid concentration were less affected by grafting. All the measurements except for ethylene and CO₂ production declined during storage regardless of the grafting treatment. Compared with ‘Strong Tosa’ rootstock, ‘Tetsukabuto’ resulted in a more rapid ripening under 1-MCP application, as reflected by earlier increase in ethylene production and higher respiratory rate. The study demonstrates that grafting effects on postharvest ripening and quality of ‘Athena’ muskmelon can vary markedly with rootstocks used.     

Effect of oxygen and carbon dioxide absorbers on strawberry quality

This study investigated the effect of active modified atmosphere packaging on quality of fresh strawberries. Strawberries were treated with one oxygen and two different carbon dioxide scavengers throughout storage at 4 °C for 4 weeks. The effect of active packaging was assessed by comparing gas concentrations, pH, electrical conductivity, total soluble solids, surface color, decay incidence, texture profile analysis, sensory analysis, and FT-NIR analysis values. pH values were significantly higher in the controls (package without absorbers) during storage compared with other treatments. The package headspace with CO₂ absorbers, had the lowest CO₂ accumulation and O₂ absorbers resulted in constant O₂ levels (5 kPa) during storage. Total soluble solid contents of all treatments were between 10.34% and 7.7% except for the control which had a value of 6.94% at the end of the storage. CO₂ absorbers are clearly effective for maintaining soluble solid contents. Electrical conductivity was lowest with CO₂ absorbers throughout storage and color was better maintained in all treated fruit. Firmness values of the controls were significantly lower than those of the treatments. Results of sensory evaluation showed that the controls had the lowest scores for all attributes. This study shows that the FT-NIR is a powerful-nondestructive tool for monitoring quality of strawberries and produces rapid readings during storage. In general, our study showed that the use of active packaging preserves strawberry.     

冰核细菌对棉铃虫结冰温度影响的研究

 以棉铃虫为对象，采取喷雾和喂食两种接种方法，研究了冰核细菌对昆虫的结冰温度的影响。结果表明：两种方法接种的冰核细菌均能明显提高棉铃虫的结冰温度，但不同接种方法间存在差异。喷雾接种的虫体结冰温度比对照高5.14-10.79℃,接种1天后就将结冰温度提高5.90℃，在棉铃虫化蛹后还能将结冰温度提高7.71℃。喂食接种虫体接种两天后才与对照的结冰温度之间出现明显的差异，能将结冰温度提高2.25-4.56℃,化蛹后仅能将结冰温度提高0.93℃。试验证明，冰核细菌能在昆虫体上起到异源冰核的作用，从而提高虫体的结冰温度。为探索一条利用生物冰核降低越冬害虫的过冷却能力，诱发虫体在较高温度下发生结冰，破坏细胞组织，造成虫体死亡，以此来提高越冬害虫的死亡率，压低来年虫源，减轻危害的促冻杀虫新途径提供了科学依据。     

热处理方式对冬枣货架期品质的影响

通过不同温度热水处理和不同时间热蒸汽处理,研究了热处理方式对冬枣货架期品质的影响.结果表明:53℃热水处理6 min效果最好,不仅延缓冬枣衰老,保持其风味,抑制生理和病理伤害,还可降低腐烂指数、软化率和失水率等.     

杨树冰核细菌溃疡病发病的主导因素

在我国东北地区、杨树上普遍存在的冰核活性（INA）细菌，能在温度-4℃以下产生冰核活性，主要种类为：成团泛氏菌[Pantoea agglomeransGavinietal=Erwinia herbicola]、菠萝泛氏菌[Pantoea ananas(Serrano)Mergaert et al=E.ananas]、大黄欧文氏菌[Erwinia rhapontici(Millard)Burkholder]、噬夏孢欧文氏菌[Erwinia uredovara(Pon.et al)Dye]和丁香假单胞菌[Pseudomonas syringae pv.syringue Van Hall]。它们主要分布于感病寄主的冻枝、冻死芽、枝干肿包、溃疡瘤、病枝、真菌溃疡病斑等部位，春秋两季为活动期和侵染期，出现频率最高，占细菌分离数的50%以上，泛氏菌占优势，在病部内外均有分布，内部较多，杨树冰核活性细菌在春秋季节霜冻条件下能造成杨树冻达，并引起肿茎型细菌溃疡病，是病害发生的主导因素，研究还证明，杨树冰核活性细菌能增强真菌溃疡病菌的侵染，促进真菌溃疡病的发生。     

防腐冰对鱼类保鲜效果研究↑（*）

防腐冰是水中添加防腐剂制成的，它能够增强对鱼在冰鲜期间的保藏效果。本文采用感官检定和ＴＶＢ－Ｎ等鲜度指标，研究了几种Ｎａ＿２－ＥＤＴＡ冰和苯甲酸钠冰对鲅鱼和带鱼的保鲜效果。结果表明：（１）１‰Ｎａ＿２－ＥＤＴＡ冰具有较稳定、持久的抑菌效果，能有效地延缓鱼品感官质量下降和ＴＶＢ－Ｎ上升，冰藏８天的带鱼细菌数，普通冰组为３．７×１０￣５个／ｇ，而１‰。Ｎａ＿２－ＥＤＴＡ，冰组仅为２．１×１０￣４个／ｇ。（２）以感官检定８０分为基准，与使用普通冰相比，使用１‰Ｎａ＿２－ＥＤＴＡ冰保鲜鲅鱼，保藏期由１１６ｈｒ提高到１４０ｈｒ，保鲜带鱼，保藏期由１０４ｈｒ提高到１６４ｈｒ。     

乙酸喷淋对酱牛肉微生物及有害物质的控制研究

[目的]考察乙酸喷淋对延长酱牛肉的货架期及保质期的作用。[方法]以酱牛肉成品为研究对象,先在酱牛肉成品上分别喷淋1%乙酸(10 ml/kg)和蒸馏水,再于4和25°C储存。研究喷淋乙酸对其后续储存、销售过程中品质指标及有害物质含量的影响。[结果]试验发现,乙酸喷淋酱牛肉可降低产品的菌落总数,降低硝酸盐、亚硝酸盐和生物胺的含量,同时对成品的口感、色泽、外观等感官指标无不良影响;持续3个月的工厂实际应用效果表明,乙酸喷淋酱牛肉后,在出厂和开始销售10 h这2个时间点的菌落总数和亚硝酸盐的合格率均有不同程度的上升,尤其是开始销售10 h的合格率分别提高45.56%和14.44%。[结论]研究可为提高酱牛肉成品的货架期提供一种新的思路和手段,值得深入拓展应用到其他酱卤肉制品。