温度对菠萝汁流变学特性及维生素C的影响

Effects of temperature on rheological properties and vitamin C of pineapple juice

探讨了不同温度条件对菠萝汁流变学特性及不同杀菌方式对菠萝汁维生素C含量等特性的影响。研究结果表明,菠萝汁的粘度随着温度的升高而降低,浓度越高,其粘度随着温度升高而降低的趋势越明显。随着菠萝汁浓度的升高,其流动活化能(Ea)增加,频率因子(η0)值随浓度的增加而减少。对于35°Brix以上的菠萝汁,温度的提高能够明显降低其粘度。因此,提高温度可降低粘度来达到热能的有效利用,菠萝汁应浓缩到35°Brix或以上时较为理想。三种杀菌方式,尤其是UHT处理的菠萝汁VC保留率都较高。巴氏杀菌和HTST处理的菠萝汁VC含量无明显差别,分别为223μg/mL和224μg/mL,VC保留率为80%左右;而UHT处理后,菠萝汁中残留的VC含量为257μg/mL,保留率达到94%左右,同时,采用UHT杀菌方式时,菠萝汁的色泽比其他两种杀菌方式更加接近于原汁。

Pineapple juices of different concentrations were heat-treated at various temperatures and the viscosity and vitamin C changes were detected to study the thermal effects on rheological properties and nutrients of pineapple juice. With the temperature increasing, the viscosity of pineapple juices increased, and the more concentrations of the juices,the trend was more obvious.The Arrhenius model η =η0 exp（Ea/RT） was found well reflecting the influence of temperature and concentrations on the viscosity.At above 35°Brix, reducing viscosity of pineapple juice by heat treatment was more significant than under 35°Brix.UHT was found preferential to HTST and pasteurization for retaining vitamin C.Content of vitamin C retained by HTST and pasteurization was almost no distinction,they were 223μg/mL and 224μg/mL, respectively.Their retention rate was 80%.Content of vitamin C retained by UHT was 25μg/mL, its retention rate was 94%.The color of pineapple juice by UHT was similar to natural juice.