Application of High Pressure Processing for Obtaining Fresh-Like Fruit Smoothies

Three high pressure processing (HPP) treatments (350 and 450 MPa for 5 min and 600 MPa for 3 min) at cold temperature (10 A degrees C) were assessed as an alternative to thermal pasteurization (85 A degrees C for 7 min) to obtain multi-fruit smoothies with fresh-like properties destined for retailing lines. The effects of the treatments on various sensory, enzymatic, physical-chemical and nutritional properties were determined 48 h post-processing, and microbial quality (total viable and psychrophilic bacteria, coliforms, Escherichia coli, Salmonella spp., Listeria monocytogenes, moulds and yeasts) was checked after 30 days of refrigerated storage. Compared with HPP, the thermal treatment only provided benefits with respect to the inactivation of oxidase and pectic enzymes but had clear disadvantages concerning the development of a cooked-fruit flavour and the loss of vitamin C. The application of 350 MPa did not alter fruit properties and ensured the microbiological quality of smoothies, while using higher pressures involved a higher risk of flavour alteration without providing other benefits. Both HPP treatments retained vitamin C, total phenols and flavonoids but also resulted in a sucrose hydrolysis. However, the antioxidant capacity and the values of lightness, turbidity, transmittance and viscosity indicated that the pressurized smoothies had a higher tendency for clarification and oxidation than the thermally pasteurized smoothies. Thus, the resistance of spoiling enzymes to high pressure is probably the main handicap when pressurizing fruit smoothies, since these enzymes remained active in the HPP-treated smoothies and the potential sensory and nutritional benefits of using HPP could be lost during storage.