Effect of high pressure and thermal processing on shelf life and quality of strawberry purée and juice.

The purpose of the study was to determine the effects of high pressure processing (HPP; 400-600 MPa, 20 °C, 1.5 or 3 min) and heat treatment (HT; 85 °C for 2 min) of strawberry purée and juice made from the same raw material. Microbiological and enzymatic inactivation, Brix, pH, anthocyanins, vitamin C, colour and sensory properties were analysed after processing and cold storage. The microbiological shelf life of the products was at least 49 days when processed at 500 or 600 MPa. Anthocyanins, vitamin C and colour were well preserved after HPP and HT. During storage, anthocyanins, vitamin C and sensory quality were better conserved in HT than in HPP purées, while there were minor differences between HT and HPP juices. This was probably due to higher enzyme activity in HPP purées, and indicates that raw materials with lower initial enzyme activity, like juices, are more suited for HPP than e.g. purées.