A Comparative Study of the Quality of Strawberry Purée Preserved by Continuous Microwave Heating and Conventional Thermal Pasteurization During Long-Term Cold Storage
This study was aimed at monitoring changes in the quality of strawberry purée 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 purée. The recommended cold shelf-life for the MV-preserved purée was estimated at 100 days, during which time it was of a superior quality compared with CTP-preserved purée.
KeywordsStrawberry purée Continuous microwave heating Conventional thermal pasteurization Cold storage Polyphenols Antioxidant capacity
The project was financed by the National Research Center (grant NO. NN 312 252540) and cofinanced from the funds of the European Union within the European Social Fund (contract No. 78/ES/ZS-II/W2151.1/11). The authors would like to thank Enbio Technology Co. for access to the EnbioJet ® continuous flow microwave heating system.
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