Doctor Krystian Marszałek, Ph.D., manages the technical lab within the Department of Fruit and Vegetable Product Technology at the Waclaw Dabrowski Institute of Agricultural and Food Biotechnology in Warsaw, Poland. His research team’s study, “High pressure processing and thermal pasteurization of strawberry purée: quality parameters and shelf life evaluation during cold storage” was published in the March 2017 edition of the Journal of Food Science and Technology and can purchased here.
Q: What visible effects (color, texture, etc.) did you notice in your puréed strawberry samples when they were subjected to high pressures at varying lengths?
A: In the case of strawberry purée, we could see that after HPP the color was more intense in comparison to the control sample. The differences in texture were insignificant. We preserved the purée for 12 weeks afterwards, and unfortunately, over time during storage both the texture and color decreased.
The most likely factors that influenced these changes are native tissue enzymes. Enzymes from oxidoreductase and hydrolase groups are responsible for intense degradation of polyphenols like anthocyanins (responsible for color) and pectins (responsible for texture) during long-term storage.
Q: What effect did HPP have when it came to inactivating various spoilage organisms? Did you evaluate the samples for shelf-life extension?
A: We found that HPP with pressure up to 600 MPa and temperature up to 50°C inactivated yeasts and molds and significantly decreased the total microbial count. Consequently, the shelf-life of fruit products can be extended at least up to one month with refrigerated storage.
Q: What are some of your thoughts on how can we waste less and be more resourceful with fruit-based food and beverage products?
A: Prolonging shelf life of fresh juices, which is usually 1-2 days in the Polish market, up to at least one week, obviously would result in less waste. In my opinion, we should eat as little processed food products as possible. In the case of juices, it’s better to consume cloudy not-from-concentrate juice than clear juice from concentrate. Similarly, fruit purée or whole pieces of fruit and vegetables are preferable to juices.