壳聚糖涂膜处理对翠冠梨果实常温货架期色泽和贮藏品质的影响

以翠冠梨果实为试验材料,研究1.0%、1.5%和2.0%壳聚糖涂膜处理对翠冠梨果实常温货架期色泽和贮藏品质的影响。试验结果表明:壳聚糖涂膜处理能延缓果实色泽变化,抑制果实果皮色泽向黄褐色转变、延缓果皮叶绿素含量的降低和类胡萝卜素的积累。与对照组(CK)果实相比,壳聚糖涂膜果实腐烂率、失重率、呼吸强度均降低,能够使果实硬度和营养品质维持在较高水平。说明壳聚糖涂膜处理能够作为翠冠梨果实的保鲜技术以提高成熟翠冠梨采后的贮藏品质,其中1.5%壳聚糖涂膜处理对常温货架期翠冠梨果实的保鲜效果最佳。     

壳聚糖水杨酸盐的制备及其对荔枝保鲜的应用

针对荔枝易腐败的特点以及壳聚糖(CTS)和没食子酸(GA)的结构特征,制备了水溶性的壳聚糖水杨酸盐(CTS-SA),通过红外光谱和紫外光谱表征了该产品的结构,以凯氏定氮法测定了壳聚糖与水杨酸的取代度。结果表明,壳聚糖和水杨酸通过壳聚糖上的氨基和羧酸中的羧基发生了成盐反应,取代度为0.699。研究了CTS-SA作为涂膜剂对荔枝常温保鲜的作用,结果表明:CTS-SA可以有效抑制贮藏期荔枝果实的失重和褐变,延缓果皮花色素苷含量、果肉中可溶性固形物与可滴定酸的下降;CTS-SA对荔枝贮藏期果皮细菌的抑制作用显著优于CTS,贮藏72 h后,CTS-SA涂膜组荔枝果皮的细菌总数只有CTS处理组的61.7%。     

低温结合壳聚糖涂膜处理对金桔贮藏品质的影响

以无涂膜果实为对照,对壳聚糖含量占0.5%、1.0%和1.5%在低温条件下(6℃±2℃)涂膜处理对金桔果实,研究对贮藏品质的影响。结果表明:与对照组相比,不同质量分数的壳聚糖涂膜处理均能有效抑制金桔果实腐烂率和失重率的上升,延缓可溶性固形物含量、总酸含量和抗坏血酸含量的下降。其中,在低温条件下,1.5%壳聚糖涂膜处理对保持金桔果实的贮藏品质更显著,说明低温结合1.5%壳聚糖涂膜处理,更适用于金桔果实的贮藏保鲜。     

壳聚糖结合1- 甲基环丙烯处理对李果实货架期品质的影响

为改善贮藏后李果实品质和开发综合贮藏保鲜技术,研究贮藏前壳聚糖涂膜处理及其结合贮藏后1- 甲基环丙烯(1-MCP)熏蒸处理对货架期“牛心”李果实品质的影响。结果表明：贮藏前采用10、15、20g/L 壳聚糖溶液涂膜处理及其结合贮藏后采用1.0μl/L 1-MCP 熏蒸可以有效保持低温贮藏(2℃、4 周)后货架期(23～25℃)李果实的硬度,延缓果实VC 含量的下降和果皮色泽的转红,抑制果实腐烂的发生。壳聚糖和1-MCP 的结合处理比两者各自的处理效果都好,能进一步显著地改善李果实在货架期的品质表现,为李果实综合贮藏保鲜技术开发提供依据。     

黄皮精油-壳聚糖复合涂膜对番木瓜果实常温贮藏品质及生理的影响

以"日升"番木瓜为实验材料,采用黄皮精油-壳聚糖复合涂膜处理果实,通过定期测定常温(25℃)贮藏期间番木瓜果实的外观和营养品质等生理指标,探究黄皮精油-壳聚糖复合涂膜对番木瓜的贮藏品质及生理的影响。结果表明,黄皮精油-壳聚糖复合涂膜处理对番木瓜采后具有明显的保鲜作用,能减少果实失重率和硬度的下降,同时能维持可溶性固形物(TSS)和维生素C(VC)含量,抑制相对电导率和丙二醛(MDA)含量的积累,能显著抑制番木瓜果实病情指数上升,延缓果实腐烂,其中以0.8%壳聚糖+40μL/L黄皮精油复合涂膜的保鲜效果最好。但壳聚糖单一处理的番木瓜果实的保鲜效果不显著,其失重率和相对电导率在贮藏后期均高于对照。因此,0.8%壳聚糖+40μL/L黄皮精油涂膜处理番木瓜能维持果实较好的品质和贮藏性能,延长果实的贮藏时间,可为开发出一种替代化学药剂的安全无毒的生物保鲜方法提供参考。     

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。     

三种涂膜保鲜剂对石榴果实贮期品质的影响

以陕西临潼净皮甜石榴为试材,研究了壳聚糖、海藻酸钠和明胶三种涂膜保鲜剂对石榴果实贮藏期间品质变化的影响.结果表明:在温度为5.0±0.5℃条件下贮藏,采用1%壳聚糖溶液涂膜,能有效保持石榴果粒可溶性固形物含量和可滴定酸含量,减缓果皮相对电导率和褐变指数升高速率,贮藏120d果实外观色泽鲜艳,籽粒感官品质良好,保鲜效果理想;而采用1%明胶和1%海藻酸钠溶液涂膜处理的石榴贮期果粒可溶性固形物含量和可滴定酸含量下降严重,果皮相对电导率和褐变指数上升较快,籽粒风味劣化,感官品质不佳.     

羧甲基壳聚糖包覆薏苡仁油前体脂质体的稳定性研究

为评价羧甲基壳聚糖包覆薏苡仁油前体脂质体(CM-PL)的贮藏稳定性及复水稳定性,本研究以贮藏过程中薏苡仁油(CSO)渗漏率、丙二醛(MDA)生成量为主要指标系统考察了CM-PL在不同贮藏条件下的贮藏稳定性;以CSO渗漏率为指标考察了氯化钠溶液、葡萄糖溶液对CM-PL复水稳定性的影响。结果表明:光照、高温以及空气接触均影响CM-PL的稳定性,其影响顺序为温度空气光照;其中温度升高可提高芯材渗漏量,加速脂质氧化;贮藏初期,光照组及空气接触组与对照组相差不大,可能与羧甲基壳聚糖能在一定程度上延缓体系的光致氧化及自氧化进程有关,但其保护作用有限,因此CM-PL应真空、避光、低温贮藏;复水稳定性结果显示CM-PL对氯化钠的耐受性高于葡萄糖,与二者共存贮藏14 d后CSO渗漏率分别为14.3%,21.1%。     

壳聚糖涂膜处理对沙糖桔采后生理及品质的影响

目的研究壳聚糖涂膜处理对沙糖桔(Shatang mandarin)采后生理及品质的影响。方法常温条件下(20±2)℃采用0.5%、1.0%和1.5%壳聚糖涂膜处理,每4 d取一次样品,分别对沙糖桔果实的腐烂率、呼吸强度、可滴定酸含量、可溶性固形物含量和维生素C含量进行测定。结果与对照组相比,不同质量分数的壳聚糖涂膜处理均能有效抑制沙糖桔果实腐烂率的上升,延缓呼吸强度、可滴定酸、可溶性固形物和维生素C含量的下降。其中,1.5%壳聚糖涂膜处理对维持沙糖桔果实采后生理及品质的效果更显著。结论常温条件下,1.5%壳聚糖涂膜处理适用于沙糖桔果实的贮藏保鲜。     

壳聚糖和噻苯咪唑处理对晋枣鲜果贮藏品质的影响

研究壳聚糖(chitosan,CTS)涂膜处理和噻苯咪唑(thiabendazole,TBZ)熏蒸处理对晋枣鲜果采后贮藏品质的影响。将具有果面3/4红色成熟度的新鲜晋枣分别用质量浓度2. 0 g/L的壳聚糖溶液进行涂膜和含噻苯咪唑4. 5%(质量分数)的烟剂以5 g/m3熏蒸3 h,后置于-1～0℃冷库中贮藏,定期测量相对电导率、果实硬度、丙二醛、叶绿素、可滴定酸、抗坏血酸含量和失重率、好果率,贮后进行感官评价。结果表明,壳聚糖涂膜和噻苯咪唑熏蒸处理均能够降低果实细胞膜相对渗透率,抑制丙二醛的积累,维持较高的果实硬度,保持可滴定酸和抗坏血酸含量,减缓叶绿素含量的下降,减少果实失重和腐烂,壳聚糖涂膜处理保鲜效果优于噻苯咪唑熏蒸处理。贮藏100 d时,壳聚糖涂膜处理好果率为94. 6%,果实色泽鲜艳,口感俱佳。     

Short‐term anoxia treatment maintains tissue energy levels and membrane integrity and inhibits browning of harvested litchi fruit

Pericarp browning is the main limitation to the postharvest storage, handling and marketing life of litchi fruit. Pre‐storage treatment with pure N₂ gas is potentially effective in reducing skin browning and maintaining eating quality of litchis. To better understand inhibition of pericarp browning by a short period of anoxia, adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) levels, adenylate energy charge and membrane permeability were investigated. Litchi fruit were exposed to pure N₂ gas for 6 h and then kept in closed but vented containers for 6 days in the dark at 25 °C and 95–100% relative humidity. Changes in the mentioned fruit physiology and biochemistry parameters and in browning index were measured. ATP concentration and adenylate energy charge decreased rapidly and membrane permeability (relative leakage) increased gradually during storage. Fruit exposed to N₂ gas exhibited higher concentrations of ATP, ADP and AMP and adenylate energy charge levels, and lower levels of browning index and membrane permeability, compared to control (non‐N₂‐treated) fruit. Greater differences in ATP and ADP concentrations and adenylate energy charge levels of pericarp tissues between N₂‐treated and control fruit were more manifest after 4 and 6 days of storage, in association with significant differences at the 5% level in the pericarp browning index. It is suggested that pre‐storage anoxia treatment maintains membrane integrity of pericarp tissues, with high ATP and ADP concentrations and high adenylate energy charge levels. Thus, the loss of cellular compartmentalization (mixing of enzymes and substrates) that leads to enzymatic browning of litchi fruit pericarp is delayed. Copyright © 2007 Society of Chemical Industry     

Role of anthocyanin degradation in litchi pericarp browning

Pericarp browning is the main problem of post-harvest litchi fruit, resulting in an accelerated shelf life and reduced commercial value of the fruit. Underhill and Critchley (1994). Anthocyanin decolorisation and its role in lychee pericarp browning. Australian Journal of Experimental Agriculture, 34, 115-122 found that there was not an obvious change in the content of anthocyanins when the fruit browned. This work was conducted with a view to explaining this unexpected observation. Litchi pericarp browning index increased while the content of anthocyanins decreased with storage time when 0.1 M HCl was used as the extract solution instead of acidic methanol. The visible spectum of the anthocyanin extract, at a range of 400–600 nm and pH values of 1.0, 3.0 and 5.0, were recorded, with an absorbance peak of about 510 nm. The colour of the extract depended on the pH values and the half-degradation constants for anthocyanins at pHs 1.0, 3.0 and 5.0 were, respectively, 29, 15.3 and 10.5 days, as calculated from the kinetics of the degradation. Compared with the anthocyanin extract, anthocyanidin is more vulnerable, with a half-degradation of about 5.3 min at pH 5.0. Furthermore, the product from the anthocyanidin degradation had a similar structure to catechol (a good substrate for polyphenol oxidase), which, in turn, could accelerate enzymatic browning reaction by the enzyme polyphenol oxidase. In addition, an anthocyanase, catalyzing anthocyanin hydrolysis and producing anthocyanidin was extracted from litchi fruit pericarp. High activity of the enzyme was observed in the pericarp. Thus, it is suggested that anthocyanase might contribute to the browning of litchi pericarp involved in the anthocyanase-anthocyanin-PPO reaction.     

Effect of oxalic acid on control of postharvest browning of litchi fruit

Litchi (Litchi chinensis Sonn.) fruit, cv. Huaizhi, was treated with 2 and 4 mM oxalic acid and stored at room temperature to investigate the effect of oxalic acid on pericarp browning. The results showed that the pericarp browning indices of the fruit, treated with both oxalic acid concentrations, were significantly lower than that of the control, due to increase of membrane integrity, inhibition of anthocyanin degradation, decline of oxidation, and maintanance of relatively low peroxidase activity in the fruit during storage. It appears that application of oxalic acid can effectively control the pericarp browning of litchi fruit during postharvest storage.     

采后荔枝果实安全保鲜技术研究进展

荔枝果实在采后贮藏和运输中极易发生病原菌侵染、褐变及腐败而导致品质劣变。目前常用的物理保鲜方法成本高,而人工合成化学杀菌剂处理可能会有一定残留且病原菌容易产生抗药性,故使用无毒害、可生物降解、对环境无污染的新型安全保鲜技术是目前的研究热点。对国内外壳寡糖涂膜保鲜技术、植物提取物保鲜技术和生物拮抗菌保鲜技术等安全保鲜技术在采后荔枝果实保鲜应用的研究进展进行了综述,旨在为维持采后荔枝果实品质,延长荔枝果实贮藏期提供技术参考。     

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.     

Effect of pure oxygen atmosphere on antioxidant enzyme and antioxidant activity of harvested litchi fruit during storage

The effects of pure oxygen on pericarp browning, reactive oxygen species (ROS) metabolism, antioxidant enzyme and antioxidant activity of harvested litchi fruit were investigated. Application of pure oxygen significantly prevented pericarp browning and delayed the increase in membrane permeability of litchi fruit during storage. Litchi fruit exposed to pure oxygen showed a lower level of lipid peroxides, compared to control fruit, with the delay in the increases of both H₂O₂ content and superoxide production rate. Furthermore, it was found that the treatment with pure oxygen induced the activities of superoxide dismutase (SOD), ascorbated peroxidase (APX) and catalase (CAT), which could be beneficial in scavenging of H₂O₂ and superoxide and alleviating lipid peroxidation. In addition, antioxidant ability (reducing power and free-radical scavenging activity against DPPH radical, superoxide anions and hydroxyl radical) of methanol extracts from litchi fruit pericarp declined gradually, with decreasing contents of anthocyanins and phenolic compounds, as storage time of the fruit progressed. There was a linear relationship between the contents of either anthocyanins or phenolic compounds and antioxidant ability or free radical scavenging activity. Treatment with pure oxygen markedly increased antioxidant ability, which was related to higher levels of anthocyanins and phenolic compounds, compared with those of control fruit. It is suggested that enhanced antioxidant activity and antioxidant enzyme induced by pure oxygen may contribute to alleviating lipid peroxidation and maintenance of membrane integrity, which reduced decompartmentation of enzymes and substrates, resulting in enzymatic browning.     

荔枝果皮变色机理的研究

白蜡荔枝研究表明：荔枝果皮花色苷在510nm有最大吸收峰,随着氢离子浓度的降低,花色苷的红色变浅或光谱吸收峰变低,吸收峰消失的临界氢离子浓度为1×10-3．5mol／L。但氢离子浓度在1×10-2～10-3mol／L范围内对多酚化合物的影响不明显。新鲜荔枝在室温放置两天半,果皮外表全部变色。荔枝果皮变色主要由3方面原因引起：1）果皮可滴定酸降低,H＋离子浓度逐渐降低并小于临界值而引起花色苷颜色由深变浅,最终失去红色,它是荔枝初期可逆性变色的重要原因。2）花色苷氧化破坏。3）酶促多酚褐变。     

低温贮藏对"长营"橄榄果实采后生理和品质的影响

研究了"长营"橄榄果实在(15±1)℃和(8±1)℃下贮藏的果实呼吸强度、细胞膜透性和品质的变化.结果表明:在(15±1)℃下贮藏的橄榄果实呼吸强度高,呼吸高峰较旱出现,果实细胞膜透性、失重率和果皮褐变指数增加,果实好果率低.而(8±1)℃低温贮藏可降低橄榄果实呼吸强度,延缓呼吸高峰出现,抑制果实细胞膜透性和果皮褐变指...     

低温贮藏对晚熟龙眼“立冬本”果实采后生理和品质的影响

研究了龙眼"立冬本"果实在采后(25±0.5)℃和(3±0.5)℃温度下的呼吸强度、细胞膜透性和品质的变化。结果表明:龙眼果实属于非呼吸跃变型果实;在(25±0.5)℃下贮藏4天,果实呼吸强度下降,之后明显上升;果实采后果皮细胞膜透性快速增加,果实易失重、衰老、腐烂和果皮褐变,贮藏后期果肉自溶;果肉可滴定酸和维生素C含量快速下降,总糖和蔗糖含量下降,还原糖含量先升后降,可溶性固形物含量在贮藏前期下降而后期上升,可溶性固形物和可滴定酸比值先升后降;贮藏后期果肉可滴定酸含量增加。而(3±0.5)℃低温贮藏可显著降低果实呼吸强度,抑制病原菌生长,延缓果实衰老和果皮细胞膜透性增加,延迟果皮褐变,减少果实失重和果肉营养成分变化,抑制果肉自溶,保持果实较高的品质,延长果实贮藏期。