Effect of non-thermal methods on the safety of strawberries (Fragaria anannassa) and watercress (Nasturtium officinale)

Innovative non-thermal technologies have been studied as an attempt to substitute thermal methods on fruits and vegetables processing. The objective was to study the effect of methods, such as ultrasonication, and its combination with a milder heat treatment (thermosonication), and UV-C irradiation on safety of strawberries and watercress. Thermosonication studies were carried out at 50ºC, 55ºC, 65ºC and room temperature. Control water washings, at the same temperatures, were also performed. Safety was assessed in terms of total mesophyles and total coliforms, respectively on strawberries and watercress samples. For total mesophyles, results showed that thermosonication carried out at 65ºC and water washing at 50ºC were the most efficient treatments in microbial reduction. Results from UV-C treatments were not conclusive. For total coliforms, the most efficient processes were thermosonication and water-washing at 55 ºC. Results from UV-C treatments were identical to the ones obtained by ultrasonication and water washing at room temperature