The impact of high pressure processing (HPP) at 300 or 500 MPa for 1, 5 or 15 min at 0 or 50 °C and thermal processing
(TP) at 90 °C for 15 min on the quality of strawberry purée was studied. TP caused the highest degradation
of polyphenols (14%), anthocyanins (43%), vitamin C (61%) and color (dE N 3) but only this method
effectively decreased the activity of polyphenol oxidase — PPO (97.7%), peroxidase — POD (99.5%) and microorganism
count (b1 log cfu/g). The highest decrease of the mentioned nutrients (4%, 14%, 30%, respectively) in
HPP-treated samples was noticed at 500 MPa/15 min/50 °C, whereas color changes were unnoticeable
(dE b 3) and enzymes were inactivated only in 72% (PPO) and 50% (POD). Counts of yeasts and molds were reduced
to b1 log cfu/g only after TP and HPP at 500 MPa. HPP preservation at 0 °C affects the content of nutrients
and color to the least extent.
Industrial relevance: This study demonstrated that the nutritional and sensory qualities of strawberry purée after
high pressure processing were much better than after thermal pasteurization. Purée treated with HPP at 0 °C did
not show significant difference compared to fresh strawberry purée. Greater inactivation of PPO and POD was observed
after thermal pasteurization, but this treatment caused also slightly more degradation of anthocyanins, vitamin
C and sensory quality. The results showed that HPP might be a useful method for preservation of
strawberry products. However, considering the residual enzyme activity, it will be a very important point to
check the stability of the products during storage