石榴采后病害及贮藏保鲜技术研究进展

石榴果实色泽鲜艳、籽粒营养丰富、鲜食味美可口,深受消费者喜爱,但石榴采后易发生果皮褐变和腐烂变质而严重影响其商品价值。本文对石榴采后病害、贮藏环境因素和相关保鲜技术进行综述,着重介绍石榴贮期生理病害和微生物病害的起因、症状及防控措施,在确定贮藏温度、相对湿度、气体成分、环境净度为影响贮藏品质的相关因素的基础上,详细叙述了机械冷藏、自发气调包装贮藏、气调贮藏、涂膜贮藏等保鲜方法,并对未来贮藏保鲜技术的发展方向进行展望,旨在为石榴贮藏保鲜提供理论参考。      

Hot water and curing treatments reduce chilling injury and maintain post-harvest quality of 'Valencia' oranges

‘Valencia’ oranges [Citrus sinensis (L.) Osbeck] were harvested at optimal maturity and either dipped in hot water at 53 °C for 3 or 6 min or at 48 °C for 12 min or cured at 53 °C for 1 or 6 h or at 48 °C for 12 h. The fruits were not degreened, waxed or treated with any post‐harvest fungicides. All fruit samples were stored at 4 °C for 6 months following the treatments. Both hot water dip and curing treatments reduced chilling injury and decay when compared with the untreated control. The most effective treatments were curing of fruit at 53 °C for 6 h and at 48 °C for 12 h. Weight loss and juice yield were higher in cured fruits than those from other treatments, but the heat treatments had no consistent effects on titratable acid, soluble solids, ascorbic acid and peel colour. It was concluded that a pre‐storage hot water dip and curing at high temperatures might be beneficial in preventing chilling injury and decay of ‘Valencia’ oranges for 6 months of storage at 4 °C.     

Antimicrobial activity of torilin isolated from Torilis japonica fruit against Bacillus subtilis

ABSTRACT:  Torilis japonica fruit has been used in therapeutic antimicrobial treatments in Korea and China since ancient times, but there is still little information on the mechanism underlying this activity. We found that the ethanol extract of T. japonica fruit showed excellent antimicrobial activity against Bacillus subtilis ATCC 6633 spores and vegetative cells. The crude ethanol extract (75%) reduced the spore concentration by 3 log cycles and the vegetative cell concentration to lower than the detection level (reduction in spore concentration by more than 6 orders of magnitude) at a concentration of 1% (w/v). The ethanol extract of T. japonica fruit was fractionated into n -hexane (H) and a water layer. The active antimicrobial compound was isolated and purified from the hexane layer, and identified as torilin (5-[1-(acetyloxy)-1-methylethyl]-3,8-dimethyl-2-oxo-1,2,4,5,6,7,8,8a-octa-hydroazulen-6-yl(2 E )-2-methylbut-2-enoate; C₂₂H₃₂O₅). Torilin immediately reduced vegetative cells counts by 5 to 6 orders of magnitude, and reduced spores counts by 1 order of magnitude. The integrity of structures such as the inner, middle, and outer layers of the coat and the cortex, protoplast membrane, and core are vital to spores. Torilin functions as a surfactant with hydrophilic and hydrophobic properties related to denaturalization of various proteins. The distortion of coat proteins due to direct binding polar groups of spore coats with hydrophilic groups of torilin may be responsible for the observed rapid inactivation of bacterial spores.     

The effects of 1-methylcyclopropene on peach fruit (Prunus persica L. cv. Jiubao) ripening and disease resistance

In order to learn how 1‐methylcyclopropene (1‐MCP) affects ripening and disease‐resistance of peach fruit (Prunus persica L. cv. Jiubao) after harvest, they were treated with 1‐MCP and some were inoculated with Penicillium expansum. Treating peach fruit with 0.2 μL L^?1 of 1‐MCP at 22 °C for 24 h effectively slowed the decline in fruit firmness. The minimal concentration of 1‐MCP able to inhibit fruit softening was 0.6 μL L^?1. Changes in other parameters related to peach ripening, such as content of soluble solids, total soluble sugar, titratable acidity, soluble pectin and ethylene production were also significantly reduced or delayed by 1‐MCP. Repeated treatment of peach with 1‐MCP resulted in more effective inhibition of ripening. Post‐harvest decay of peach fruit was reduced by treatment with 1‐MCP and disease progress in fruit inoculated with P. expansum was reduced. The activities of phenylalanine ammonialyase, polyphenoloxidase and peroxidase in the inoculated fruit were also enhanced by 1‐MCP.     

采后处理与贮藏条件对柑贮藏效果的影响

通过对椪柑贮藏历年来的相关实验研究,即预贮、包装等不同的采后处理方法并结合砃峦ǚ缈夂屠淇庵兄?藏结果观测比较,找出了不适宜椪柑果实贮藏的采后处理方式和利于其贮藏的某些方法、设施。常温通风预贮预冷显著好于冷库冷风预冷;无论在常温通风库还是冷库中贮藏75d以上,单果包装均显著好于打蜡处理。正交实验进一步明确了包果袋宜薄不宜厚,预贮时间较长为宜。     

5种药剂对柑橘贮藏病害的防控效果评价

柑橘果实在贮藏运输期间极易发生青霉病、绿霉病、炭疽病、酸腐病等各类病害。为了减轻病害造成的损失,本文在自然通风贮藏库内用保鲜剂对柑橘果实进行保鲜效果实验,结果表明5种保鲜剂在常规剂量范围内对柑橘贮藏病害均有较好的防治效果。对柑橘果实总的保鲜效果和酸腐病的效果,以百可得最优,贮藏保鲜的时间最长,异菌脲其次;对青霉病、绿霉病、炭疽病,则以咪鲜胺最好,抑霉唑其次;贮藏15~45d,5种药剂处理对柑橘的失重率没有影响,贮藏到60d后有一定差异;果实外观色泽与清水对照没有差异,口感则以百可得和异菌脲风味略好;5个药剂处理15~30d后对果实品质没有不利影响。      

烟草赤星病拮抗芽胞杆菌的筛选及培养基优化

以赤星病原菌Alternaria longipes为筛选指示菌,采用平板共培养初筛和发酵上清滤液复筛的方法,筛选了烟草赤星病拮抗芽胞杆菌3株。其中菌株K₁₁的菌体径向生长抑制率（PIRG）为63.64%,发酵上清滤液的PIRG值达67.44%。盆栽试验证明,该菌对烟草赤星病具有良好的拮抗能力。经鉴定菌株K₁₁为枯草芽胞杆菌（Bacillus subtilis）。由单因素实验和正交实验优化得到了K₁₁菌株生物量较高的摇瓶发酵培养基配方：葡萄糖20.0 g/L,豆粕30.0 g/L,K₂HPO₄·3H₂O 1.0 g/L,MgSO₄·7H₂O 0.1 g/L。优化后生防菌株K₁₁的生物量比对照提高6.5倍,生物量高达1.28×10¹⁰ CFU/mL,芽胞形成率在95%以上。     

不同真空处理对水蜜桃贮藏效果的研究

对水蜜桃在10～20 kPa和20～30 kPa不同时间的真空处理后进行常压冷藏试验,研究了水蜜桃贮藏过程中的生理生化变化.结果表明,采用10～20 kPa的高真空处理水蜜桃7 d以上,可明显提高水蜜桃的贮藏效果,而真空处理时间少于4 d时,其贮藏效果与普通常压冷藏差异不明显,其中以10～20 kPa高真空压力处理7 d,调节真空压力至20～30 kPa再处理7 d后移入常压库冷藏的贮藏效果最佳.     

1-MCP对黄花梨冷藏品质和抗氧化特性的影响

为探讨1-MCP处理对黄花梨冷藏品质及氧化还原水平的作用,黄花梨果实采后先经1μL/L的1-MCP处理12h,再在1℃下贮藏120d,随后20℃存放7d,监测果实硬度、可溶性固形物、失重率、电导率、丙二醛(MDA)含量、超氧阴离子(O-2·)生成速率、可溶性蛋白含量和抗氧化酶活性的变化。结果显示,1-MCP处理可显著抑制果实可溶性蛋白分解,提高超氧化物歧化酶(SOD)和过氧化物酶(POD)的活性,促进过氧化氢酶(CAT)活性下降,降低MDA含量和O-2·生成速率,同时可延缓失重率和电导率上升,保持果实硬度,抑制可溶性固形物含量上升。本研究表明,贮前1-MCP处理可延缓黄花梨果实的衰老变质,其作用与较高的抗氧化水平有关。     

国内外微生物源食源性疾病监测及其防控进展

微生物源食源性疾病是一个世界性的公共卫生问题,其暴发不仅严重危害了人类健康,还带来了严重的经济损失,受到各国的高度重视。全面了解国内外微生物源食源性疾病监测的网络和机制、食源性疾病暴发相关的原因食品以及国内外微生物源食源性疾病的发病季节和分布规律,有助于我们对食源性疾病的监测、预防和控制。本文总结了食源性疾病爆发的相关知识,介绍了世界卫生组织、发达国家(美国、英国、丹麦和澳大利亚)以及我国对常见微生物源食源性疾病的监测现状。通过了解和借鉴世界各国的监测方式,提出了预防和控制食源性疾病的措施,包括:加强食源性疾病监测网络建设,加大食品安全监管力度,扩大食源性疾病监测范围和加强对食源性疾病的宣传教育,为我国食源性疾病的监控和防控提供有价值的参考。     

Exploitation of microbial antagonists for the control of postharvest diseases of fruits: a review

Fungal diseases result in significant losses of fruits and vegetables during handling, transportation and storage. At present, post-production fungal spoilage is predominantly controlled by using synthetic fungicides. Under the global climate change scenario and with the need for sustainable agriculture, biological control methods of fungal diseases, using antagonistic microorganisms, are emerging as ecofriendly alternatives to the use of fungicides. The potential of microbial antagonists, isolated from a diversity of natural habitats, for postharvest disease suppression has been investigated. Postharvest biocontrol systems involve tripartite interaction between microbial antagonists, the pathogen and the host, affected by environmental conditions. Several modes for fungistatic activities of microbial antagonists have been suggested, including competition for nutrients and space, mycoparasitism, secretion of antifungal antibiotics and volatile metabolites and induction of host resistance. Postharvest application of microbial antagonists is more successful for efficient disease control in comparison to pre-harvest application. Attempts have also been made to improve the overall efficacy of antagonists by combining them with different physical and chemical substances and methods. Globally, many microbe-based biocontrol products have been developed and registered for commercial use. The present review provides a brief overview on the use of microbial antagonists as postharvest biocontrol agents and summarises information on their isolation, mechanisms of action, application methods, efficacy enhancement, product formulation and commercialisation.     

采后涂膜处理对山竹果壳细胞代谢物和果肉品质的影响

以山竹果为材料,研究了采后涂膜处理常温贮藏(1%壳聚糖和1%海藻酸钠)对山竹果壳细胞代谢物及果肉品质的影响。结果表明:采后涂膜处理常温贮藏中山竹果壳中超氧阴离子、膜脂过氧化产物丙二醛(MDA)、过氧化氢的含量随着贮藏时间呈上升趋势,贮藏15d时,常温、1%壳聚糖、1%海藻酸钠涂膜处理的丙二醛含量比初期分别增加了94.4%、67.0%和38.9%。果壳代谢物可溶性糖和总酚含量均先上升后下降,2种涂膜处理均能有效延缓果壳细胞代谢物的增加。其中1%壳聚糖涂膜处理能够显著延缓果肉VC和总糖含量的下降,减慢营养物质的消耗,抑制果实的腐烂。     

The effect of temperature on microbial growth in apple cubes packed in film and preserved by use of orange juice

Red delicious apple cubes were packed in fresh orange juice containing chemical preservatives (citric and ascorbic acid, potassium sorbate) and covered with plastic films of different gas permeabilities (polyethylene and EVA‐SARAN‐EVA) before storage at 4, 10 and 20 °C. The concentration of potassium sorbate in the product was optimized with respect to colour and microbial growth. Yeast and mould growth was modelled by Gompertz and linear equations to derive parameters such as lag phase, maximum microbial population and specific microbial growth or rates of decline. Activation energies for the specific growth rates were estimated from Arrhenius‐type equations and the time required to reach microbial counts of 10^6±0.2 CFU g^?1 was determined in all cases. At 4 °C, these values were longer than 25 days in all systems tested. The use of a low gas permeability film and an adequate potassium sorbate concentration extended storage life at higher temperatures.     

The use of biodosimetry to measure the UV-C dose delivered to a sphere, and implications for the commercial treatment of fruit

Commercialization of UV-C treatment of horticultural produce in order to induce beneficial responses in the produce following treatment requires both accurate dose delivery and a method of treating large quantities of produce efficiently. Furthermore, it has long been assumed that such effects require the entire surface of the horticultural commodities - typically fruit - to be exposed to UV-C. This has invariably been achieved by manually rotating the fruit in a UV-C field whilst reducing the dose delivered at each rotation in direct proportion to the number of rotations. However, the resulting UV-C dose distributions achieved under these circumstances are generally not reported in the literature. In the work described here a polystyrene sphere (dia. 70 mm) was used to simulate fruits such as tomatoes, apples, peaches, etc., that have an approximately spherical form in order to provide a means of measuring the total doses of UV-C accumulated during treatment and comparing such estimates to theoretically-derived ones. This was achieved using dosimetry based on spores of Bacillus subtilis in which spore-impregnated membranes were attached to the surface of the sphere. The fraction of spores surviving exposure was used to estimate dose from a dose-response curve for the spores. Under irradiation conditions leading to a theoretically calculated dose of 10.6 J, spore dosimetry yielded estimates of 9.1, 10.7 and 6.1 J for UV-C delivered in, respectively, one, two or four exposures. In the case of exposure of the sphere during continuous mechanical rotation for the same length of time (80 s) a value of only 3.5 J was obtained. Irradiation conditions resulting in the spores being subject to intermittent exposure to UV-C led to dose estimates below the theoretically derived ones. The circumstances under which spore dosimetry can be used to obtain surface dose distributions are discussed.     

The effects of topical treatments with 6-pentyl-2-pyrone and structural analogues on stem end postharvest rots in kiwifruit due to Botrytis cinerea

The picking wounds in kiwifruit formed by breaking off the pedicels at harvest were treated topically with the naturally occurring lactones 6-pentyl-2-pyrone (6PP), decano-δ-lactone (DL) and 2-deceno-δ-lactone (massoialacetone: ML), and with the synthetic fungicide vinclozolin. 6PP was applied at rates from 0·4 to 4 mg, neat or diluted in oil, water or acetone. 6PP treatments consistently reduced the incidence of Botrytis cinerea storage rots to low levels in both inoculated and naturally infected fruit. For inoculated fruit, control was achieved even when treatment was delayed up to 2 days from inoculation. ML gave significant but lesser control than 6PP, while DL was not generally effective. DL was also less effective than ML or 6PP at suppressing B cinerea inoculum germination in vitro. Much lower rates of vinclozolin (8 or 70 μg) also gave significant control of storage rots. Such topical treatment methods permit control of storage diseases with similar application quantities to currently accepted preharvest fungicide treatments. © 1998 SCI.