Influence of Ultra High Pressure treatment on the quality of Lychee juice

In order to study the effect of ultra high pressure(UHP) treatment on the quality of lychee juice, the prepared lychee(Lychee chinensis Sonn. cv. Huaizhi) juice was subjected to UHP treatment(100～500 MPa for 30 min at 10℃). Total number of bacteria, peroxidase(POD) activity and nutritional ingredients(including reducing sugar, protein, amino acid and Vitamin C) content were detected. Results show that total number of bacteria declines with pressure increase and arrived commercial asepsis at 400MPa, increasing pressure results in a higher level of POD inactivation with 55% decline at 500 MPa, reduced sugar content have no obvious change from 100 MPa to 500 MPa, the content of protein and amino acid declined a little with pressure increase, Vitamin C content appeares a decreasing trend over 400 MPa with 20% loss at 500 MPa. These results indicate that UHP treatment on lychee juice has a good bactericidal effect, certain passivation effect on food-quality enzyme and a good retention of nutritional ingredients, so UHP treatment is a potential cold-working technique for lychee processing.