Effects of 1‐methylcyclopropene on oxidative damage,phospholipases and chilling injury in loquat fruit

BACKGROUND: Low‐temperature storage is commonly used for loquat (Eriobotrya japonica Lindl.) fruit to inhibit decay and extend postharvest life, but it also increases the severity of chilling injury (CI) in red‐fleshed fruit. 1‐Methylcyclopropene (1‐MCP) has been used to reduce the development of CI in cold‐stored loquat. However, the effects of 1‐MCP on changes in antioxidant system and phospholipase activity and their relation to CI have not been investigated. The objective of this study was to determine whether the 1‐MCP‐induced modification in antioxidant system and phospholipase activity is linked to the reduced CI in cold‐stored loquat fruit. RESULTS: 1‐MCP treatment significantly alleviated CI in ‘Fuyang’ loquat fruit. The treatment markedly inhibited the accumulation of malondialdehyde, superoxide radicals and hydrogen peroxide and the increase in electrolyte leakage. In addition, 1‐MCP‐treated fruit exhibited significantly higher catalase activity and lower lipoxygenase (LOX) and phospholipase C (PLC) activities than control fruit during storage. CONCLUSION: These results suggest that LOX and PLC are associated with the induction of CI in loquat fruit. 1‐MCP might reduce CI by inhibiting LOX and PLC activities and alleviating oxidative damage. Copyright © 2009 Society of Chemical Industry     

Fatty acid composition and antioxidant system in relation to susceptibility of loquat fruit to chilling injury

Two cultivars of loquat fruit with contrasting chilling resistance were stored at 1 °C for 35 days to investigate the relationship between chilling injury and fatty acid composition and its antioxidant system. No symptoms of chilling injury occurred in the fruit of ‘Qingzhong’ cultivar during the whole storage, whereas in ‘Fuyang’ fruit, chilling injury increased sharply after 21 days of storage at 1 °C. ‘Qingzhong’ fruit had lower levels of superoxide radical and H₂O₂, in addition to lower lipoxygenase activity, but higher membrane lipid unsaturation and higher activities of superoxide dismutase and catalase than ‘Fuyang’. Furthermore, the chilling resistant ‘Qingzhong’ fruit also showed higher activities of antioxidant enzymes involved in ascorbate–glutathione cycle and higher levels of ascorbate acid and reduced glutathione. These results suggest that the higher membrane lipid unsaturation and the more efficient antioxidant system were both beneficial in enhancing resistance of loquat fruit to chilling injury.     

Nonenzymatic browning of selected fruit juices affected by D-galacturonic acid

This work studies the effect of d ‐galacturonic acid (AGA) on the non‐enzymatic browning of three types of clarified concentrated fruit juices (apple, pear and peach). It was observed that the presence of AGA increases the browning of juices. This was evaluated by the evolution of the absorbance at 420 nm (A₄₂₀) with the treatment time that these juices show. The evolution at A₄₂₀ over time was fitted to first‐order kinetics and it was observed that the kinetic constant values increased with both the increase in the AGA content and the rise in the treatment. The effect of the temperature treatment on the non‐enzymatic browning of these juices was quantified by fitting the variation of the kinetic constants with the Arrehnius equation, thus obtaining the corresponding activation energies. In the case of apple juice, it was observed that for the increase in AGA content the activation energy increases considerably, while for the pear and peach juices, a slight increase of the activation energy was observed with the increase in AGA.     

Effects of short‐term N2 treatment on quality and antioxidant ability of loquat fruit during cold storage

BACKGROUND: Loquat fruit is susceptible to microbial decay and quality deterioration during postharvest distribution. In this study, in a search for effective alternatives to methods currently used for quality maintenance, the effects of short‐term pre‐storage N₂ treatment on the quality and antioxidant ability of loquat fruit were investigated. RESULTS: Loquat fruits were exposed to 100% N₂ for 6 h at 20 °C and then stored at 5 °C for 35 days. Short‐term N₂ treatment significantly delayed the increase in fruit decay rate and decreases in total soluble solid and titratable acidity contents, thereby maintaining better eating quality and extending the storage life of fruits. It also markedly delayed increases in membrane permeability, malondialdehyde content and superoxide anion production rate. In addition, N₂‐treated fruits exhibited significantly higher superoxide dismutase and catalase activities and lower lipoxygenase activity than control fruits. CONCLUSION: Short‐term pre‐storage N₂ treatment effectively reduced fruit decay and maintained quality in loquat fruits during cold storage. The reduction in fruit decay and quality deterioration by the treatment was correlated with enhanced antioxidant ability and reduced lipid peroxidation. Copyright © 2009 Society of Chemical Industry     

Sugar metabolism in relation to chilling tolerance of loquat fruit

The relationship between chilling injury and sugar metabolism was investigated in loquat fruit stored at 1 °C for 35 days. No symptoms of chilling injury occurred in the fruit, of ‘Ninghaibai’ cultivar, during the whole storage whereas, in ‘Dahongpao’ fruit, severe chilling symptoms were observed after 20 days of storage at 1 °C. ‘Ninghaibai’ fruit had higher levels of glucose and fructose and higher activities of sucrose hydrolyzing enzymes, such as sucrose synthase-cleavage and invertase, than had ‘Dahongpao’. Furthermore, the chilling resistant ‘Ninghaibai’ fruit also showed higher activities of hexokinase and fructokinase, involved in hexose phoshorylation and sugar signal generation. These results suggest that the higher content of hexoses and activities of hexose sensors were likely part of the mechanism for chilling tolerance of loquat fruit.     

短时升温在果实贮藏上的应用

温度是影响果实代谢过程、品质与贮藏寿命的重要因子,应用短时升温处理技术延缓果实衰老和控制采后病害是近年来果实保鲜领域的研究热点。本文归纳了短时升温在果实贮藏上的应用,热处理方法及常见果品短时升温最佳处理温度、时间。     

低温胁迫下铜对烤烟幼苗生长及抗冷性的影响

摘要:采用溶液培养法研究不同浓度铜对烤烟幼苗生长和POD、PPO活性及MDA、Pro、Chl含量的影响。结果表明: 低温胁迫下CuSO4低于0.08 g/L时,CuSO4施用量增加能促进烟草生长;而高于0.08 g/L时,其生长受到抑制,尤其是根系生长,其抑制程度随CuSO4浓度的增加而加剧。低温胁迫下,POD和PPO活性随CuSO4浓度增加而上升,低浓度时上升较小;MDA含量随CuSO4浓度增加先微下降后递增;Pro则与MDA变化趋势相反;Chl a、Chl b以及Chl总量随CuSO4浓度增加先微增加后递减。      

热处理减轻黄瓜冷害作用机理的研究

以黄瓜(锦丰2号)为试材,研究热处理(37℃)对低温贮藏过程中黄瓜冷害发生、贮藏品质、生理生化变化等的影响,探讨热处理抑制黄瓜冷害发生的作用机理。研究表明,在0℃下,黄瓜贮藏3d后即出现冷害症状,9d后冷害发生严重,膜透性迅速上升,活性氧清除酶活性降低。热处理可以减轻黄瓜低温贮藏过程中的冷害指数,减缓叶绿素降解;热处理可以显著抑制黄瓜膜渗透率的升高,减少丙二醛的积累;提高自由基清除酶(SOD、POD、CAT)的活性。研究表明,热处理诱导活性氧清除酶活性,抑制膜脂过氧化作用,提高细胞内膜系统的稳定性,提高黄瓜对低温的适应和抵抗能力。      

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.     

甜菜碱结合热处理降低采后香蕉果实冷害的研究

以海南产巴西种香蕉果实为试材,通过甜菜碱与热水结合处理,使用响应面法优化处理条件,测定处理后香蕉果实的冷害发生率与冷害指数,确定出能显著降低香蕉果实冷害的最优处理条件。最优处理条件为:甜菜碱浓度13mmol/L,热水温度51℃,浸泡时间4min。经过(4±1)℃贮藏6d后,混合处理组果实的冷害发生率为10.56%,比对照组降低了65%,并且感官品质优于其他处理组。      

Genetic effects of heat stress on milk fatty acids in Brazilian Holstein cattle

The present study aimed to estimate covariance components of milk fatty acids (FA) and to compare the genomic estimated breeding values under general and heat-stress effects. Data consisted of 38,762 test-day records from 6,344 Holstein cows obtained from May 2012 through January 2018 on 4 dairy herds from Brazil. Single-trait repeatability test-day models with random regressions as a function of temperature-humidity index values were used for genetic analyses. The models included contemporary groups, parity order (1–6), and days in milk classes as fixed effects, and general and thermotolerance additive genetic and permanent environmental as random effects. Notably, differences in heritability estimates between environments (general and heat stress) increased (0.03 to 0.06) for unsaturated FA traits, such as unsaturated, monounsaturated, and polyunsaturated, at higher heat-stress levels. In contrast, heritability estimated between environments for saturated FA traits, including saturated FA, palmitic acid (C16:0), and stearic acid (C18:0) did not observe significant differences between environments. In addition, our study revealed negative genetic correlations between general and heat-stress additive genetic effects (antagonistic effect) for the saturated FA, C16:0, C18:0, and C18:1, which ranged from ?0.007 to ?0.32. Spearman's ranking correlation between genomic estimated breeding values ranged from ?0.27 to 0.99. Results indicated a moderate to strong interaction of genotype by the environment for most FA traits comparing a heat-stress environment with thermoneutral conditions. Our findings point out novel opportunities to explore the use of FA milk profile and heat-stress models.     

富集沙棘果油中棕榈油酸的工艺优化及脂肪酸分析

以青海沙棘果油为原料,利用化学酯交换法对沙棘果油中棕榈油酸进行富集,以棕桐油酸乙酯转化率为指标,分别研究了醇油体积比、反应温度、反应时间及KOH质量分数对沙棘果油中棕榈油酸富集的影响.再采用尿素包合法对棕榈油酸乙酯进行富集,并通过气相色谱串联质谱法对棕榈油酸富集物的组成进行分析.结果 表明:化学酯交换法的最佳工艺参数为...     

The effect of delay between heat treatment and cold storage on alleviation of chilling injury in banana fruit

BACKGROUND: To understand the mechanisms leading to the enhanced chilling resistance of banana by hot‐water dipping (HWD, 52 °C for 3 min), we investigated the effect of a 0.5–24 h delay between HWD and cold storage on chilling resistance and the change related to the metabolism of reactive oxygen species (ROS). RESULTS: The HWD‐treated fruit with a delay of less than 6 h exhibited markedly less chilling injury than the non‐heated control fruit, while a delay more than 6 h resulted in significant loss in chilling resistance. Increased hydrogen peroxide content and rate of superoxide radical production were detected in the fruit at 0.5–1.5 h after HWD treatment, and the levels declined with a longer delay, which may be correlated with the enhanced gene expression levels of the gene coding for a ROS‐generating related enzyme, NADPH oxidase (MaNOX). Enhanced activities and gene expression of an ascorbate peroxidase (MaAPX) were recorded in the fruit at 1.5–6 h after the treatment, and after 6 h the ascorbate peroxidase levels decayed to the levels as the control fruit. The higher APX gene expression was maintained in the treated fruit with a 3 h delay during the subsequent cold storage at 7 °C, correlating with the enhanced chilling resistance. CONCLUSION: The HWD‐treated fruit left at ambient temperature up to 6 h prior to cold storage maintained the effect of heat treatment and transiently increased ROS content, and the ascorbate peroxidase activity that occurred 0.5–6 h after the treatment may be correlated with the elevated chilling resistance induced by HWD treatment. Copyright © 2012 Society of Chemical Industry     

Control of anthracnose rot and quality deterioration in loquat fruit with methyl jasmonate

BACKGROUND: Loquat (Eriobotrya japonica Lindl.) fruit has a short shelf‐life, mainly due to fungal decay. Current control of postharvest disease of the fruit is mainly dependent on fungicides. However, because of the increasing consumer concern over food safety, there is an urgent need to search for effective alternatives to control disease. The objective of this work was to determine the efficacy of methyl jasmonate (MeJA) in controlling anthracnose rot caused by Colletotrichum acutatum and maintaining quality of loquat fruit. RESULTS: Loquat fruit were treated with 10 µmol L^?1 MeJA and wound inoculated with C. acutatum spore suspension of 1.0 × 10⁵ spores mL^?1 24 h after treatment, and then stored at 20 °C for 6 days. The percentage of infected wounds showing decay symptom was reduced from 54.4% to 16.7% and the lesion diameter was reduced from 7.26 mm to 4.00 mm by MeJA treatment on the 4th day after inoculation. MeJA treatment induced higher activities of two defense‐related enzymes—chitinase and β‐1,3‐glucanase—during 6 days storage. Meanwhile, the treatment inhibited increases in fruit firmness and internal browning index, and maintained higher extractable juice rate and total soluble solids and titratable acidity contents, thereby delaying the development of flesh leatheriness. CONCLUSION: MeJA treatment effectively inhibited anthracnose rot and maintained quality in loquat fruit. Inhibition of the disease was mainly because of resistance induced in loquat fruit by MeJA. A postharvest application of MeJA could be an alternative to chemical fungicides for control of postharvest disease in loquat fruit. Copyright © 2008 Society of Chemical Industry     

不同品种枇杷果实采后低温贮藏品质研究

目的 明确不同品种枇杷果实采后低温贮藏期间腐烂和品质变化的差异, 为枇杷果实贮运技术的开发提供理论依据。方法 研究了“洛阳青”、“宁海白”和“大红袍”3个品种枇杷果实5 ℃贮藏35 d期间失重率、腐烂指数、果皮和果肉颜色变化、可溶性固形物、维生素C、类胡萝卜素和总酚含量的变化。结果 “洛阳青”和“大红袍”枇杷果实采后可溶性固形物、维生素C含量和L值下降, 失重率和腐烂指数上升, 果实贮藏品质发生劣变。枇杷果实贮藏前期果皮和果肉b值升高, 类胡萝卜素和总酚含量增加。但随着贮藏时间的延长, 果实中类胡萝卜素和总酚含量逐渐下降。结论 与“宁海白”枇杷果实相比, “洛阳青”和“大红袍”枇杷果实采后5 ℃贮藏期间易发生腐烂, 品质劣变严重, 耐贮性低。     

热加工过程中棕榈油理化特性、脂肪酸与自由基的变化研究

以棕榈油（24℃）为原料,采用国标法测定棕榈油在不同温度（160、180、200℃）下常规理化指标（酸价、过氧化值、丙二醛值、p-茴香胺值和总氧化值）随时间的变化,在此基础之上,分别采用GC-MS法与电子自旋共振（ESR）法对180℃下棕榈油脂肪酸组成和自由基含量变化进行测定。结果表明,加热温度越高和加热时间越长棕榈油理化指标值越大,其中过氧化值呈现先上升后下降趋势。脂肪酸组成结果表明,棕榈油中饱和脂肪酸与不饱和脂肪酸比例约为1∶1,且随着加热时间延长,比例基本不变。ESR实验表明,加热时间越长,2-苯叔丁基硝酮（PBN）捕获的自由基量越多,棕榈油氧化程度越深。      

Effect of methyl jasmonate on quality and antioxidant activity of postharvest loquat fruit

BACKGOUND: Loquat fruit is rich in natural antioxidants and has shown a remarkably high antioxidant activity. To search for an effective method for maintaining or even improving antioxidant activity during postharvest storage, we investigated the effect of 10 µmol L^?1 methyl jasmonate (MeJA) treatment on levels of major individual sugars and organic acids, total phenolics, total carotenoids, total flavonoids and antioxidant activity in loquat fruit during storage at 1 °C for 35 days. RESULTS: The MeJA‐treated fruit exhibited significantly lower levels of respiration rate, ethylene production, phenylalanine ammonia‐lyase and polyphenol oxidase activities, and higher levels of sugars, organic acids, total phenolics and total flavonoids than control fruit. Meanwhile, the treatment also maintained significantly higher antioxidant activity as measured by the scavenging capacity against 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), superoxide and hydroxyl radicals, and by the reducing power test compared to the control. There was a significant positive linear relationship between total phenolic content and DPPH radical scavenging activity. CONCLUSION: MeJA treatment can improve the quality and functional properties of harvested loquat fruit by maintaining a higher level of antioxidants and enhancing antioxidant activity. Copyright © 2009 Society of Chemical Industry     

低温贮藏引起果蔬冷害的研究进展

果蔬在不适低温下贮藏易发生冷害,冷害可造成果蔬的贮运损失,使其食用品质下降。综述了果蔬在低温下贮藏时冷害发生的症状、机理,并重点介绍了抑制果蔬冷害的几种措施,其中包括温度调节、气调贮藏、化学物质处理等,最后提出减缓和控制低温冷害进一步研究的方向。