干燥方式和温度对草莓果粉性质及多酚含量的影响

本文主要研究了冷冻干燥、热风干燥、真空干燥方式及干燥温度对草莓果粉性质及多酚含量的影响。用50%甲醇和70%丙酮两步法提取可萃取多酚（EPP）;甲醇/H2SO4水解残渣获得不可萃取多酚（NEPP）。Folin-phenol试剂法测定多酚的含量;用色差计测定草莓果粉的L*、a*、b*值;在665 nm处测定其上清液的透光率。结果表明冷冻干燥草莓果粉的EPP和原花青素含量最高,随着干燥温度的升高,草莓果粉中EPP的含量降低,而干燥温度对NEPP的含量影响与EPP相反,各处理中TPP的含量变化不显著。干燥方式和温度对草莓果粉的溶解指数影响不明显。干燥温度升高,果粉上清液的透光率以及草莓果粉的L*、a*和b*值明显降低。总之,冷冻干燥方式可很好地保留草莓中EPP和原花青素含量以及原料本身的色泽。 

Effect of drying method and temperature on powder characteristics and polyphenol content of Strawberries

The effect of the freeze- drying,blast- drying,vacuum- drying and drying temperature on powder characteristics and polyphenol content of strawberries was studied in this paper. Extractable polyphenols( EPP)were obtained with 50% methanol and 70% acetone,and non- extractable polyphenols( NEPP) were hydrolyzed by methanol / H2SO4.Polyphenol content was determined by the Folin- phenol reagent method. The values of L*,a*,b*of the strawberry powder were measured by using a color meter.And the transmittance of the supernatant was observed at 665 nm.The results showed that the highest yields of EPP and proanthocyanins were obtained in the freeze- dired strawberry,and EPP in the strawberry powder was significantly decreased with the increasing of drying temperature and the NEPP showed the opposite trend. But there was no significant effect of the drying treatment on the TPP yield.There was no obvious change of index of the strawberry powder among different drying method and temperature. But the transmittance of the supernatant,the values of L*,a*and b*of strawberry powder decreased with the increasing of the drying temperature.In all,freeze- dried retained the EPP and original color in strawberries.