Pasteurization treatments for tomato puree using conventional or microwave processes

A pasteurization process for tomato puree using microwaves (2450 MHz) was applied and compared with the conventional heat treatment proposed by FAO. Batches of 400 g of tomato puree (pH = 4.1 and 10°Brix) were treated in a microwave oven (950 W). The same quantity was used for conventional treatment (glass bottles immersed in water at 93.3 °C). Treatments effectiveness was calculated throughout F93.38.9 value calculations. A control puree (without thermal treatment) and both treated purees were cooled and stored during 31 days at 4 °C. There were not significant (p >0.05) changes in pH and °Brix during storage in the evaluated samples. Lower colour changes were observed for tomato puree treated using microwaves. Moulds and yeasts counts remained about 103 CFU/g in the microwave-pasteurized puree after 21 days of storage. The sensory evaluations of both pasteurized purees showed no significant difference (p > 0.05) in colour, flavour and overall acceptability tests. Additionally, a population of Escherichia coli, intentionally inoculated in tomato puree, was reduced 5 log-cycles using the proposed microwave treatment, validating the efficacy of the proposed pasteurization process.