液氮冻结对冻藏雷竹笋品质的影响

目的 研究液氮的3种冻结温度和冻结至3种中心温度对冻藏雷竹笋品质的影响。方法 测定不同液氮冻结温度和中心温度的冻藏雷竹笋的汁液流失率、可溶性固形物和粗纤维含量、硬度、色差、挥发性风味物质和感官评分。结果 液氮冻结温度组中，-60℃组冻结雷竹笋的感官评分、硬度显著低于-90、-120℃组（p<0.05），而汁液流失率、粗纤维含量、a*值显著高于-90、-120℃组（p<0.05）；雷竹笋原有挥发性风味物质的信号强度为：-120℃>-90℃>-60℃，冻藏过程中产生的挥发性风味物质的信号强度为：-120℃<-90℃<-60℃。中心温度组中，-6℃组冻结雷竹笋的感官评分、硬度显著低于-12、-18℃组（p<0.05），而汁液流失率、粗纤维含量、a*值、b*值显著高于-12、-18℃组（p<0.05）；雷竹笋原有挥发性风味物质的信号强度为：-18℃>-12℃>-6℃，冻藏过程中产生的挥发性风味物质的信号强度为：-18℃<-12℃<-6℃。-12℃和-18℃组冻藏雷竹笋品质差异不显著。结论 降低液氮冻结温度加快了冻结速率，维持了冻藏雷竹笋较好的感官品质；冻结至中心温度-12℃时，雷竹笋内部大部分水分已完成冻结，此时转移至-18℃冰柜中对雷竹笋组织内部影响不显著（p>0.05）。

Effects of liquid nitrogen frozen on the quality attributes of Phyllostachys praecox shoots during freezing storage

Objective To investigate the effects of three frozen temperatures and three central temperatures with liquid nitrogen on the quality attributes of Phyllostachys praecox shoots. Methods The effects of liquid nitrogen frozen and central temperatures on the weight loss, soluble solids and crude fiber contents, hardness, color, volatile flavor substances, and organoleptic score of Phyllostachys praecox shoots were measured. Results For the liquid nitrogen frozen temperature group, the sensory score and hardness of the frozen Phyllostachys praecox shoots with the -60°C group were significantly lower than those with the -90 and -120°C groups (p<0.05), while the weight loss, crude fiber content and a* value were significantly higher than those with the -90 and -120°C groups (p<0.05), and the signal intensity of the original volatile flavor substances of Phyllostachys praecox shoots was: -120°C>-90°C>-60°C, while the signal intensity of volatile flavor substances produced during freezing was: -120°C<-90°C<-60°C. For the central temperature group, the sensory score and hardness of frozen Phyllostachys praecox shoots with the -6 °C group were significantly lower than those with the -12 and -18 °C groups (p<0.05), while the weight loss, crude fiber content, a* and b* values were significantly higher than those with the -12 and -18 °C groups (p<0.05); the signal intensity of the original volatile flavor substances of the thunder Phyllostachys praecox shoots was: -18°C>-12°C>-6°C, while the signal intensity of volatile flavor substances produced during freezing was: -18°C<-12°C<-6°C. There was no significant difference in quality attributes of Phyllostachys praecox shoots between the -12°C and -18°C groups. Conclusion The lowering frozen temperature with liquid nitrogen accelerate the frozen rate and maintain the good sensory quality of frozen Phyllostachys praecox shoots. When a central temperature of -12°C was employed, most of the moisture inside Phyllostachys praecox shoots has been frozen. Therefore, there were no significant effect on the tissue of Phyllostachys praecox shoots with freezing storage in the freezer at -18°C (p>0.05).