A Comparative Study of the Quality of Strawberry Purée Preserved by Continuous Microwave Heating and Conventional Thermal Pasteurization During Long-Term Cold Storage

Abstract

This study was aimed at monitoring changes in the quality of strawberry puree preserved by continuous microwave heating (MV) at 90 and 120 °C for 10 s and conventional thermal pasteurization (CTP) at 90 °C for 15 min during cold storage (6 °C), and determining its shelf-life. The shelf-life of MV and CTP-preserved products established on the basis of microbiological changes was more than 52 weeks (<1 log cfu of yeasts, moulds, and total microbial count per gram). During this time, 43 and 34 % of polyphenols, 89 and 58 % of anthocyanins, as well as 57 and 52 % of antioxidant capacity decrease were noted, for MV and CTP-preserved samples respectively; vitamin C was completely degraded. Color changes were more visible for MV (ΔE = 10.82) compared with the CTP-preserved sample (ΔE = 5.14). The kinetic rate of degradation of nutrients was higher for MV- compared to CTP-preserved puree. The recommended cold shelf-life for the MV-preserved puree was estimated at 100 days, during which time it was of a superior quality compared with CTP-preserved puree.