| 摘要: |
| 本文以火龙果块为原料，研究了﹣40 ℃、﹣60 ℃、﹣80 ℃和﹣100 ℃喷淋式液氮速冻及﹣18 ℃冰箱缓冻处理对火龙果微生物和品质的影响，并筛选了最佳液氮速冻温度。结果表明：样品冻结速率随液氮速冻温度降低而加快，冻结时间由1.25 min降至0.367 min，但﹣100℃出现低温断裂现象；液氮速冻处理对样品的多酚氧化酶有抑制作用，其中，﹣80 ℃液氮速冻处理后样品的多酚氧化酶活性降至47.27%，而缓冻处理后的酶活升高至301.09%；相比于缓冻处理，液氮速冻处理后的样品的质构保持更好，其汁液流失率在8.88%~10.50%之间，而缓冻处理则高达38.29%；随着液氮速冻温度的降低，样品的可滴定酸、可溶性固形物、总酚、花色苷、抗坏血酸等品质保持更好。所以在不同液氮速冻处理中，-80 ℃对样品的品质保持最佳。 |
| 关键词: 液氮速冻 火龙果块 品质 |
| DOI： |
| 投稿时间：2019-05-27 修订日期：2019-08-15
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| 基金项目:北京市科技计划课题（Z171100001317016）资助。 |
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| Effect of Liquid Nitrogen Quick-Freezing on Biochemical activity and Quality of Pitaya Blocks |
| Yang Jinli,Luo Sijia,Ding Haoyue,Wang Yongtao |
| (College of Food Science and Nutritional Engineering, China Agricultural University) |
| Abstract: |
| In this study, the effects of quick-freezing through sprayingof liquid nitrogen (-40, -60, -80, and -100 °C) and slow- freezing (-18 °C) on microorganism biochemical activity and fruit quality were studied with pitaya (Stenocereusgriseus L) blocks as raw materials. The rate of freezing of the sample accelerated with decreasing freezing temperature, and the freezing time was reduced from 1.25 to 0.367 min as freezing temperature declined. However, the sample exhibited low temperature fracturing after quick-freezing at -100°C. The liquid nitrogen quick-freezing treatment inhibited the activity of polyphenol oxidase, and the residual activity of polyphenol oxidase decreased to 47.27%after -80°C freezing, while it increased to 301.09% after the slow-freezing treatment. The texture of the sample after liquid nitrogen quick-freezing was better than that of the slow-freezing treatment and the rate of juice loss was between 8.88% and 10.50%. In contrast, the rate of juice loss was as high as 38.29% after the slow-freezing treatment. The content of titratable acid, soluble solids, total phenol, anthocyanin, and ascorbic acid increased with the decreased freezing temperature of liquid nitrogen. The -80°C liquid nitrogen quick-freezing treatment maintained the best quality of the sample. |
| Key words: liquid nitrogen quick-freezing pitaya blocks quality |
