Comparison of high pressure treatment and thermal pasteurization effects on the quality and shelf life of guava puree

The effects of high pressures and thermal pasteurization on the survival of microorganisms, enzyme inactivation and quality changes of guava puree during storage at 4 degrees C were investigated and compared with untreated samples. After treatment at a pressure of 600 MPa and 25 degrees C for 15 min, the microorganisms in guava puree were inactivated to less than 10 cfu mL(-1) and the product exhibited no change in colour, pectin, cloud and ascorbic acid content as compared with fresh samples. The inactivation of enzymes in guava puree by thermal pasteurization was greater than by high pressures. The microbial count in guava puree reduced to 200 cfu mL(-1) and the product showed marked changes in viscosity, turbidity and colour when heated at 88-90 degrees C for 24 s. The content of pectin, cloud and ascorbic acid as well as colour in untreated and high pressurized (400 MPa) guava puree gradually decreased, whereas these changes were not observed in pasteurized (88-90 degrees C) and high pressurized (6000 MPa) puree during storage at 4 degrees C for 60 days. The guava puree treated at 600 MPa and 25 degrees C for 15 min retained good quality similar to the freshly extracted puree after storage at 4 degrees C for 40 days.