不同温度差压预冷及其对西葫芦冷藏效果的影响

摘要

为了延长西葫芦的采后保鲜期和减少营养物质的损耗,本文以西葫芦(Cucurbita pepo.L)为试材,比较了不同预冷温度对西葫芦预冷后的冷藏效果,分别置于-3、0、3和6℃差压冷库中,预冷到10℃,然后在10℃条件下冷藏.期间每4 d取一次样,测定其各项指标.结果表明:6℃预冷速度最慢,0和3℃快于6℃,-3℃预冷速度最快.与冷藏前相比,冷藏结束(16 d)时,0和3℃预冷组的丙二醛含量分别上升了66.76、71.63％,显著(P<0.05)低于其他2个处理;4个组(分别为-3,0,3和6℃预冷组)的硬度分别下降了9.89％、7.46％、7.89％和11.19％;CAT活性分别为16.25、19.79、17.58和16.63 U/min?g;各组的维生素C含量分别下降了32.61％、20.65％、26.09％和30.87％;香气成分中醛类相对含量分别为69.94％、76.33％、71.47％和70.97％.与-3和6℃预冷相比,0和3℃预冷处理能够显著的延缓硬度的下降,降低呼吸速率和乙烯的释放量,因此能延缓西葫芦的采后衰老和延长货架期;并抑制了丙二醛的积累,减少组织损伤且抗坏血酸过氧化物酶活性和过氧化物酶的活性也受到抑制,提高了过氧化氢酶活性,因而可以降低活性氧伤害;并保持了较高的香气成分含量,而-3和6℃预冷的西葫在冷藏后期的呼吸强度及抗坏血酸过氧化物酶活性迅速升高,且-3℃的预冷处理使得西葫芦在之后的冷藏过程中出现了明显的冷害现象,即表皮长斑.因此0和3℃差压预冷对西葫芦的冷藏效果较好,研究结果为西葫芦采后冷链技术的发展提供了参考.%In order to extend the freshness period of post-harvestCucurbita pepo and lessen the consumption of nutrient substance, this study aims to determine the cold preservation effects of forced-air pre-cooling at different temperatures on post-harvestCucurbita pepo. In the experiments, the pre-cooling temperatures were set at-3, 0, 3 and 6℃, while the target cold preservation temperature was 10℃. The sample was examined every 4 days to determine a variety of indices. The results indicate that the pre-cooling rate at 6℃ is the slowest and that at-3℃the fastest. At the end of cold preservation period (on the 16th day), the ascent percentages of malondialdehyde (MDA) at 0 and 3 °C pre-cooling treatment are 66.76％ and 71.63％ respectively, when compared to the content before the cold preservation period, which are significantly lower than that of the other 2 treatments; the descent levels of firmness in the 4 groups (-3, 0, 3 and 6℃) are 9.89％, 7.46％, 7.89％ and 11.19％ individually; catalase (CAT) activity of 4 groups on the 16th day is 16.25, 19.79, 17.58 and 16.63U/(min?g), respectively; at the same time, the falling ranges of vitamin C content are 32.61％, 20.65％, 26.09％ and 30.87％ and the relative contents of aldehydes at the end of period are69.94％,76.33％,71.47％ and70.97％ respectively. When compared to-3 and 6℃ pre-cooling groups, temperatures between 0 and 3℃ were seen to provide the optimal cold preservation effects onCucurbita pepo, as the respiration and ethylene production rates are lower at these temperatures, which is helpful in decreasing the senescence rate and prolonging the shelf life of these vegetables, and this temperature range effectively delays the decline rate of firmness. Moreover, the accumulation of MDA and the extent of tissue damage are both inhibited at a pre-cooling temperature from 0 to 3℃. Additionally, the pre-cooling treatment at 0 and 3℃ is also shown to inhibit peroxidase (POD) enzyme activity and maintain a higher level of CAT activity, which assists in reducing reactive metabolism damage by removing reactive oxygen and free radicals. In contrast, pre-cooling temperatures of-3 and 6℃ demonstrate higher respiration rates and ascorbate peroxidase (APX) enzyme activity rises rapidly in the second half of the cold preservation period, during which APX activity at 0 and 3℃ pre-cooling remains markedly more stable. And the chilling injury appears when the pre-cooling temperature is-3℃, and there are lots of stains on the surface ofCucurbita pepo in-3℃ treatment. In conclusion, this study finds that the most suitable pre-cooling temperature range forCucurbita pepo is from 0 to 3℃ and therefore this research can provide technological and theoretical support for the development of cold-chain technology ofCucurbita pepo.