Effects of chitosan coating on shelf life of cold-stored litchi fruit at ambient temperature

Postharvest pericarp browning of litchi fruit results in an accelerated loss in shelf life and a reduced commercial value. Visual quality was lost in only 6 h at ambient temperature when fruit were removed from storage at 2 °C, due to browning. The experiment was conducted to test the role of chitosan coating in inhibiting skin browning and extending shelf life of cold-stored litchi fruit at ambient temperature. Litchi fruit were treated with 2 g chitosan/100 g solution and then stored for 20 days at 2 °C and 90–95% relative humidity (RH), prior to shelf life evaluation at 25 °C and 80–90% RH. Changes in polyphenol oxidase (PPO) activity, anthocyanin concentration, colour index, eating quality and concentrations of total soluble solids and titratable acidity were measured. The effects of chitosan coating on disease incidence were also evaluated. Application of chitosan coating delayed the decrease in anthocyanin content, the increase in PPO activity and the changes in colour index and eating quality, reduced the decrease in concentrations of total soluble solids and titratable acidity, and partially inhibited decay. The results suggested that treatment with chitosan coating exhibited a potential for shelf life extension at ambient temperature when litchi fruit were removed from cold storage.     

壳聚糖衍生物对香菇生物涂膜保鲜的研究

研究了水溶性壳聚糖衍生物———羧甲基壳聚糖(CMC)对香菇的保鲜效果,分别测定4℃贮藏期间香菇感官品质、失重率、呼吸强度、细胞膜透性、还原糖含量、Vc含量、丙二醛(MDA)含量、多酚氧化酶(PPO)活性等生理生化指标,并比较了与未经修饰的壳聚糖对香菇的保鲜效果。结果表明:CMC涂膜处理能有效降低香菇菇体的腐烂、变色;降低香菇的呼吸强度,细胞膜透性变小、MDA含量减少、降低失重率和PPO活力;同时还原糖含量和Vc含量明显降低缓慢;在4℃贮藏24 d仍保持较高的感官品质和营养品质。     

The nutraceutical quality of tomato fruit during domestic storage is affected by chitosan coating

Fruits and vegetables are highly perishable foods which usually undergo a gradual loss of nutraceuticals during storage. Chitosan‐based edible coatings are extensively studied thanks to antimicrobial activity and great potential to extend the shelf life. However, little information is presently available on the nutraceutical quality of chitosan‐coated products. The present study is addressed to evaluate accompanied by a delayed degradation of some phenolic compounds during storage. These results indicate that chitosan coating is effective in maintaining the quality parameters, the coated fruit showed less weight loss (?16%) and more firmer (+40%) than control fruit, chitosan‐coated tomato emitted significantly lower ethylene (?41%) than control, and slowing down the nutraceutical loss occurring in postharvest, mainly of the lycopene, main carotenoid, found in tomato fruits. These results indicate that chitosan coating is effective in slowing down the nutraceutical loss occurring in postharvest, thus representing a promising tool to preserve bio‐protective phytochemicals during fruit conservation.

Practical applications

During storage and domestic conservation, the nutraceutical quality of fruits and vegetables usually decreases and can undergo deterioration due to physiological disorders and mechanical damages. In the last decade, use of edible coatings has attracted interest as a promising technology to prolong the shelf life of particularly perishable foods. These coatings act as protective barriers decreasing transpiration rate and gas transfer across the product surface, thus promoting the maintenance of nutritional quality.     

Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)

The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits.     

壳聚糖涂膜对南湖菱果实贮藏生理及品质的影响

以新鲜南湖菱果实为试材,研究壳聚糖涂膜对南湖菱果实贮藏期间品质和生理的影响。用1.0g/100mL和2.0g/100mL壳聚糖溶液对果实涂膜后,4℃±1℃、相对湿度(90±2)%条件下贮藏15d,测定果实贮藏期间质量损失率、VC、总酚、可溶性总糖、蔗糖、还原糖和可溶性固形物含量变化与多酚氧化酶(PPO)、抗坏血酸过氧化物酶(APX)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)比活力以及丙二醛(MDA)含量的变化。结果表明:1.0g/100mL和2.0g/100mL壳聚糖涂膜显著减少果实表面失水,减缓VC、总酚、可溶性总糖、蔗糖、还原糖和可溶性固形物含量下降,维持果实营养品质;同时抑制褐变酶PPO比活力,减缓抗氧化酶APX和SOD比活力上升,减少膜脂过氧化产物MDA积累。因此,1.0g/100mL和2.0g/100mL壳聚糖涂膜能够有效地保存果实营养物质,延缓果实衰老,可以作为安全廉价的保鲜方法应用于南湖菱果实贮藏保鲜。     

壳聚糖处理对脐橙采后品质及抗病性的影响

研究不同质量浓度壳聚糖处理对纽荷尔脐橙采后品质及抗病性的影响。结果表明：在冷藏(8℃)条件下,壳聚糖处理抑制了脐橙果实的呼吸强度、延缓了总糖的上升和可滴定酸的下降并保持了较高的VC 含量,从而保持了较好的果实品质。同时,在贮藏后期壳聚糖处理也提高了脐橙果实超氧化物歧化酶、苯丙氨酸解氨酶、几丁质酶和β-1,3- 葡聚糖酶的活性,增强了果实的抗病性。但不同处理间存在着差异,其中以1.5g/100mL 壳聚糖效果最好,2.0g/100mL 壳聚糖次之,1.0g/100mL 壳聚糖最差。     

Effect of chitosan coating combined with postharvest calcium treatment on strawberry (Fragaria × ananassa) quality during refrigerated storage

Strawberries (Fragaria × ananassa Duch.) were coated with either 1% or 1.5% chitosan (CS) or chitosan combined with calcium gluconate (CaGlu). Following treatment, strawberries were stored at 10 °C and 70 ± 5% RH for one week. The effectiveness of the treatments in extending fruit shelf-life was evaluated by determining fungal decay, respiration rate, quality attributes and overall visual appearance. No sign of fungal decay was observed during the storage period for fruit coated with 1.5% CS (with or without the addition of CaGlu) or 1% CS + 0.5% CaGlu. By contrast, 12.5% of the strawberries coated with 1% CS lacking calcium salt were infected after five days of storage. The chitosan coating reduced respiration activity, thus delaying ripening and the progress of fruit decay due to senescence. Chitosan coatings delayed changes in weight loss, firmness and external colour compared to untreated samples. Strawberries coated with 1.5% chitosan exhibited less weight loss and reduced darkening than did those treated with 1% chitosan, independently of the presence or absence of CaGlu. However, addition of calcium to the 1% chitosan solution increased the firmness of the fruit. Coated samples had greater visual acceptability than had untreated fruits. The addition of calcium gluconate to the chitosan coating formulation increased the nutritional value by incrementing the calcium content of the fruit.     

Shelf life extension of fresh fruit and vegetables by chitosan treatment

Among alternatives that are currently under investigation to replace the use of synthetic fungicides to control postharvest diseases in fresh produce and to extend their shelf life, chitosan application has shown promising disease control, at both preharvest and postharvest stages. Chitosan shows a dual mode of action, on the pathogen and on the plant, as it reduces the growth of decay-causing fungi and foodborne pathogens and induces resistance responses in the host tissues. Chitosan coating forms a semipermeable film on the surface of fruit and vegetables, thereby delaying the rate of respiration, decreasing weight loss, maintaining the overall quality, and prolonging the shelf life. Moreover, the coating can provide a substrate for incorporation of other functional food additives, such as minerals, vitamins, or other drugs or nutraceutical compounds that can be used to enhance the beneficial properties of fresh commodities, or in some cases the antimicrobial activity of chitosan. Chitosan coating has been approved as GRAS substance by USFDA, and its application is safe for the consumer and the environment. This review summarizes the most relevant and recent knowledge in the application of chitosan in postharvest disease control and maintenance of overall fruit and vegetable quality during postharvest storage.     

机械损伤对橄榄采后品质及其生理的影响

通过人工上树采摘、拦网采摘和自然掉果三种采收方式,探讨不同程度的机械损伤对橄榄采后商业品质及其生理的影响,结果表明:橄榄果实受到机械损伤后,在贮藏期间,果实的失重率和可溶性固形物呈线性增加,细胞膜透性增大,有机酸和VC的含量减少,含水量快速下降,呼吸速率迅速提高,PPO、POD、CAT活性上升,加速了果实的衰老进程.轻采轻放,减少机械损伤,对延长橄榄果实贮藏寿命,提高果品商业品质具有积极意义.     

Influences of preharvest spraying Cryptococcus laurentii combined with postharvest chitosan coating on postharvest diseases and quality of table grapes in storage

The effects of preharvest spray with Cryptococcus laurentii combined with chitosan coating after harvest on decay and quality of table grapes during storage periods were evaluated in the present study. Preharvest spray with C. laurentii (PreA) significantly decreased decay index (DI), and postharvest chitosan coating (PCC) enhanced the effectiveness of the pre-harvest spray when fruits were stored at 0 °C. PreA combination with PCC increased the activities of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) of fruit in storage. PreA + PCC treatment was effective in reducing weight loss of fruits by 85% at 17 d storage and 38% at 42 d storage as compared to PreA alone at the same stage. In addition, PreA enhanced the ratio of soluble solids content (SSC) to titratable acid (TA) by 12% at harvest time, 7% at 17 d storage and 25% at 42 d storage, mainly by increasing SSC and decreasing TA in fruit stored at 0 °C. These results suggested that integration of preharvest spray with C. laurentii and postharvest chitosan coating treatment may be a promising management strategy for decay control and quality maintenance of table grapes.     

1-甲基环丙烯及仲丁胺对枇杷贮藏效果的影响

探讨1-MCP (1- 甲基环丙烯)及仲丁胺(2-AB)对枇杷采后处理的效果,以延长其贮藏期及货架期。采用“大红袍”枇杷为试材,研究在4℃冷藏条件下,采用不同剂量1-MCP 加上相同剂量0.1mL/L 2-AB 对枇杷进行熏蒸处理,定期观察果实好果率、失水率、总糖、VC、可溶性固形物、呼吸强度、多酚氧化酶及过氧化物酶活性的变化。结果表明：在固定浓度为0.1mL/L 2-AB 时,20mL/L 1-MCP 处理对枇杷的保鲜效果最佳,可显著抑制果实呼吸强度, PPO 和POD 活性,从而抑制果实的后熟与衰老,降低枇杷果实的失水率,保持较高的好果率,延缓总糖、VC 含量的下降,有利于枇杷品质的保持,贮藏64d 果实外观色泽鲜艳,品质良好,保鲜效果理想。     

Ultrasound-Assisted Chitosan–Surfactant Nanostructure Assemblies: Towards Maintaining Postharvest Quality of Tomatoes

A novel ultrasound-assisted chitosan–surfactant nanostructure assembly was developed to allow better delivery of chitosan particles into intact fruit tissues for extension of postharvest life. Three solutions of 1 % chitosan–surfactant nanostructure assembly with micelle sizes of 400, 600 and 800 nm were prepared and applied as an edible coating on tomatoes. The fruits were stored at 15?±?2 °C and 70–80 % relative humidity for 20 days. The indicators of tomato ripening, which included loss of firmness, decline of titratable acidity, decline of chlorophyll content and increase in soluble solid content, were delayed in the treated fruits in comparison to the control (p?<?0.05). A delay of approximately 5 days in ripening was observed by evaluating the colour evolution from green to red. The treatment significantly (p?<?0.05) enhanced the phenolic content while maintaining a lower level of respiration in comparison to the control, throughout most of the storage duration. However, weight loss was higher in the treated fruits in comparison to the control. No significant difference in the resultant effects was observed by using chitosan–surfactant nanostructure assemblies of different micelle sizes (p?>?0.05).     

壳聚糖/EGCG@MNPs纳米复合包装对低温和常温贮藏蓝莓保鲜效果的影响

本研究以壳聚糖作为薄膜基质,加入负载表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）的黑色素（melanin）纳米颗粒（EGCG@MNPs）,制备了一种活性包装薄膜,用于延长采后蓝莓的贮藏期。首先,壳聚糖/EGCG@MNPs纳米复合膜采用流延法成功制备,装入新鲜蓝莓后形成独立热封包装袋,分别于4和25 ℃条件下贮藏。贮藏期间分析不同时期内蓝莓果实失重率、腐烂率、硬度、呼吸强度、微生物、表观品质等感官指标和理化指标,以探讨该纳米复合包装膜的保鲜效果。结果表明,壳聚糖/EGCG@MNPs纳米复合膜显著延缓了蓝莓果实贮藏期间的失重率、腐烂率和硬度的下降（P<0.05）,有效抑制了蓝莓的呼吸强度,减小了活性物质的消耗和果实表面的褐变程度。贮藏结束时,经过纳米复合包装处理的蓝莓仍保持了较高的花色苷含量,在4和25 ℃环境下保留率分别为90.1%和99.0%;DPPH自由基清除活性分别比对照组高了6.2%和6.3%,使蓝莓果实保持了较好的抗氧化能力,并显著抑制了多酚氧化酶（polyphenol oxidase,PPO）的活性和微生物的生长（P<0.05）,有效改善了蓝莓的感官品质,延缓了蓝莓果实的衰老。综合各项结果得出,壳聚糖/EGCG@MNPs纳米复合包装结合低温的贮藏方法对采后蓝莓的保鲜效果最好。     

丁香提取液可食性复合涂膜对新余蜜橘常温保鲜效果的影响

为了开发新余蜜橘保鲜的新技术和延长其贮藏时间,探讨50 mg/mL丁香乙醇提取液复配1.0%羧甲基纤维素、700 mg/L柠檬酸、1.0%蔗糖酯及1.0%丙酸钙制成可食性复合涂膜,在常温(20±1℃)下,考察复合涂膜处理对新余蜜橘果实保鲜效果及采后生理生化变化的影响。结果表明:与对照相比,复合涂膜显著降低新余蜜橘果实常温贮藏期间腐烂率和失重率,两者的减少幅度分别为对照组的27.3%和24.6%,延缓了可溶性固形物、可滴定酸及抗坏血酸含量的下降;有效抑制了果实呼吸强度和丙二醛含量的升高,同时还能保持果实较高SOD、POD、PPO和PAL活性,延缓果实衰老。与CMC涂膜相比,加了丁香提取液的复合涂膜可显著降低果实的腐烂,对果实品质无不良影响,同时可以诱导PPO和PAL活性的上升,提高新余蜜橘果实的抗病性。丁香提取液可食性复合涂膜用于新余蜜橘的常温保鲜切实可行。     

魔芋葡甘聚糖涂膜对采后西番莲果实品质影响

以西番莲为原料,研究常温条件下不同浓度魔芋葡甘聚糖(Konjac Glucomannan,KGM)溶液(0.5%、1.0%和1.5%)涂膜对西番莲果实采后品质的影响。结果表明,KGM涂膜可减少西番莲果实水分蒸发,延缓果实皱缩指数和失重率的上升;维持较高的外果皮L*、a*、b*值,使西番莲在常温贮藏时保持较好色泽。同时,KGM涂膜有效抑制西番莲果实可溶性糖、可滴定酸和可溶性固形物(TSS)的降解,维持西番莲果实的风味及营养品质。其中,浓度为1.0%的KGM涂膜保鲜效果最佳,可作为提高西番莲果实采后贮藏品质、延长保鲜的适宜处理条件。     

水溶性壳聚糖涂膜处理对采后绿芦笋贮藏品质的影响

研究了0.50%的水溶性壳聚糖(WSC)和羧甲基壳聚糖(CMC)分别对在2℃贮藏条件下采后绿芦笋的涂膜保鲜。通过感官品质、失重率、抗坏血酸含量、叶绿素含量、丙二醛(MDA)含量、总酚含量、多酚氧化酶(PPO)等生理生化指标的测定,以未经处理的绿芦笋为对照。结果表明:经0.50%的CMC和WSC进行涂膜处理,均可有效地降低芦笋的失重率,维持其硬度,延缓其抗坏血酸和叶绿素营养物质的消耗。而且CMC处理可以明显抑制绿芦笋总酚含量的下降及其PPO、POD和SOD活性的变化,其感官品质也明显优于对照组,使绿芦笋的贮藏时间延长至35 d。     

壳聚糖涂膜对延缓菜心采后衰老效果的研究

研究了菜心在不同浓度壳聚糖涂膜处理后4℃下贮藏时的质量损失、叶绿素含量、主要营养和过氧化物酶活性的变化。结果表明,与对照相比,壳聚糖涂膜处理明显减少了菜心的质量损失,延缓了菜心的叶绿素、蛋白质、可溶性总糖及Vc含量的下降速度,降低了过氧化物酶活性。2%和3%的壳聚糖处理显著延缓了菜心采后衰老,延长了冷藏菜心的保鲜期。     

氧化玉米淀粉涂膜对低温贮藏期间甜樱桃生理及品质的影响

以“红灯”甜樱桃为材料,研究在采后0 ℃和7 ℃条件下氧化玉米淀粉涂膜对果实保鲜效果的影响。结果表明,氧化玉米淀粉涂膜可有效延缓低温贮藏期间甜樱桃果实的质量损失率和呼吸强度,降低细胞膜透率,抑制丙二醛的积累。此外,氧化玉米淀粉涂膜还可有效维持果实的可溶性固形物、可滴定酸、抗坏血酸（VC）含量,保持果实的外观、风味和口感;0 ℃条件下涂膜处理的保鲜效果要显著优于7 ℃。由此表明,氧化玉米淀粉涂膜可有效延缓冷藏期间甜樱桃果实的成熟衰老,最大限度地保持果实品质,可作为新型的果蔬涂膜材料,应用于水果、蔬菜的实践采后保鲜过程。     

可食性复合涂膜对芒果货架期生理品质的影响

以壳聚糖和可食性淀粉为成膜剂,添加有机酸等亲水性助剂,配制3种可食性复合膜(M1、M2和M3),研究(20±0.5)℃条件货架期内不同可食性复合涂膜处理(以蒸馏水浸泡做空白对照)对芒果转黄率、转色指数、腐烂率、呼吸强度、硬度、质量损失率、可溶性固形物含量(soluble solid content,SSC)、维生素C(VC)和多酚氧化酶(polyphenol oxidase,PPO)活性等生理指标的影响。结果表明：芒果货架期期间,涂膜处理可以有效地抑制果实转黄和腐烂,推迟果实呼吸高峰的到来,显著降低芒果果实的转色指数和软化程度,提高果实硬度。同时,M3处理还可较好地保持果实的质地,有效减缓果实SSC上升的速度和幅度,维持果实较高的VC含量,但对果实PPO活性的抑制与其他涂膜处理间差异不显著。研究表明,涂膜处理可以显著改善芒果货架期期间品质劣变情况,尤以M3涂膜处理效果最好。     

壳聚糖涂膜对沂州木瓜贮藏品质的影响

以沂州木瓜为试材,研究壳聚糖涂膜对木瓜的保鲜作用。在室温条件下采用不同质量分数的壳聚糖溶液对沂州木瓜进行涂膜处理,测定其总糖、VC含量、感官品质、质量损失率、硬度和腐烂率的变化。结果表明：壳聚糖涂膜处理能延缓果实硬度、总糖含量、VC、质量损失率和感官品质的降低,降低果实的腐烂率,1.5%壳聚糖涂膜处理保鲜效果最好,可有效地延长沂州木瓜的保鲜期。