草莓液氮速冻特性及营养品质的研究

Quick-frozen Characteristics and Nutritional Quality of Strawberries in LN2-spraying Freezer

目的探究草莓的液氮速冻工艺特性。方法利用自行研制的液氮喷雾式速冻装置,温度设置在-40～-70℃之间,以5℃为间距进行草莓液氮速冻实验,并检测、分析不同冻结温度条件下的草莓冻结速率、失水率、色差、Vc含量和花青素含量等指标。结果随着冻结温度的降低,草莓冻结时间缩短,冻结速率由9.75cm/h提高到20.00cm/h,但当冻结温度低于-55℃时,继续降低冻结温度,其冻结速率增幅减小。随着冻结温度的降低,液氮速冻后草莓的失水率、Vc含量、花青素含量和总酚含量呈现增大趋势,但增幅逐渐变小。结论液氮速冻草莓采用-55℃冻结温度进行速冻时,既可保证草莓快速冻结,又可最大程度地保留草莓的营养品质。

The work aims to explore the characteristics of strawberries＇ liquid nitrogen （LN2） quick freezing process. The LN2 quick-frozen strawberries experiment was conducted at the temperatures ranging from ？40 ℃ to ？70 ℃ with 5 ℃ interval by means of a self-made LN2-spraying quick freezing device. The indexes of strawberries including freez-ing rate, water loss rate, chromatic aberration, contents of vitamin C and anthocyanin, etc. under different freezing tem-peratures were tested and analyzed. The freezing time was shortened and the freezing rate was increased from 9.75 cm/h to 20.00 cm/h with the reduction of freezing temperature. When the freezing temperature was lower than ？55 ℃, the in-crease of freezing rate decreased as the temperature continued to reduce. Water loss rate, Vc, anthocyanin and total phe-nolics of LN2 quick-frozen strawberries showed an increasing tendency with the reduction of freezing temperature, but the rate of increase was gradually decreased. The LN2 quick-frozen process of strawberries at ？55 ℃ can ensure the rapid freezing and maximally retain nutritional quality of the strawberries.