液浸速冻荔枝裂果控制工艺研究
Technique of cracking control during immersion freezing of litchi fruit
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摘要: 荔枝保鲜期短是荔枝产业健康发展的技术瓶颈,采用新型液浸速冻技术可实现荔枝高品质保藏1 年以上。但在生产实践中发现,该技术导致荔枝裂果现象较多。分析了荔枝在速冻过程中的裂果特点,研究了品种、热水漂烫、真空度及冷冻温度等单因素对荔枝裂果率的影响,并通过正交试验优化了速冻荔枝裂果的控制工艺。结果表明:液浸速冻荔枝缝合线裂果类型占比可达67.67%;速冻妃子笑裂果率仅10.29%,显著低于怀枝和桂味,与该品种缝合线不明显、果皮厚度较大及抗裂性较强呈正相关;热水漂烫5~7 s、包装真空度-0.085~-0.092 MPa、冷冻温度-35℃~-40℃的工艺处理裂果较少;正交实验发现冷冻温度对裂果的影响最大,裂果控制的最佳工艺组合为7 s 沸水漂烫、-0.085 MPa 真空包装、-35℃液浸速冻。进一步完善了荔枝液浸速冻技术,为实现荔枝全年保藏并促进我国荔枝出口创汇提供参考。Abstract: Short shelf-life limits the development of litchi industry. Nowadays litchi fruits can be extended to more than 1 year with high quality preservation by using the new technology of immersion freezing( IF). But high fruit cracking rate was found in application of IF. In this study,based on analysis of the characteristics of cracked litchi fruit in the IF process,effects of the single factor of litchi variety,hot water blanching,vacuum degree or freezing temperature on fruit cracking rate were studied. Fruit cracking control in IF process was optimized by orthogonal experiment as well. Cracked suture was found to be the major type of cracking,constituted up to 67.67% of the cracking. Cracking rate of frozen Feizixiao(cv.) was only 10.29%,significantly lower than that of Huaizhi(cv.)and Guiwei(cv.),which was attributed to the unobvious suture,the thicker pericarp and the greater fracturing resistance of this cultivar. Treatment of hot water blanching for 5 s to 7 s,vacuum packing in - 0.085 MPa to - 0.092 MPa,or freezing at - 35℃ to -40℃ was found to preferably reduce the fruit cracking rate. The optimum technical combination would be hot water blanching for 7 s,vacuum packaging in - 0.085 MPa and IF at -35℃ based on the result of orthogonal experiment and freezing temperature was considered to to be the most significant factor on fruit cracking rate. The study contributed to improve IF technology and achieved a whole year preservation of litchi fruit,and therefore promoted litchi export of China.