Application of PEF and freeze concentration processing technology on litchi juice.

摘要

Pulsed electric field (PEF) is a technology that can effectively kill microorganism at ambient temperature, but it fails to inactivate enzymes that are responsible for the deterioration of quality. The present research treatment of PEF was attempted to utilize combination with freeze concentration to alleviate enzymatic degradation. Litchi juice was firstly treated by PEF at field strength of 20 kV/cm for 6.8 ms to eliminate food borne pathogens and other background flora, and then treated by freeze concentration so as to remove excess water. Under the condition of -1.5-4.7 degrees C, litchi juice was concentrated from 14 to 40 degrees Brix and stored at -18 degrees C. The low temperature significantly reduced the enzymatic activities, and extended the shelf-life. After stored for 6 months, the concentrated juice was reconstituted with distilled water for sensory evaluation by the triangle method. The results showed that there were no significant differences between the freshly prepared juice (p<0.01) and the one treated by PEF and reconstituted.