High pressure pasteurization of apple pieces in syrup: Microbiological shelf-life and quality evolution during refrigerated storage

The inactivation of Candida lipolytica LMM02.68 and Escherichia coli LMM1010 on 1-cm apple cubes in acidified glucose solution (12.5 or 25.0% d-glucose) by high pressure treatment at 200–650 MPa for 10 min at 25 or 40 °C was investigated. At 25 °C and in all solutions, a 6-log reduction of C. lipolytica and E. coli was achieved at 400 and 600 MPa, respectively. Subsequently the shelf-life of HP-treated packaged apple pieces in 25.0% acidified glucose solution was studied during refrigerated storage (7 °C) in a pilot-scale study with 306 packages containing 200 g of product. The microbiological shelf-life of the product, defined as the time when the aerobic mesophilic plate count or mold and yeast count first exceeded 7 log CFU/g, was extended from 15 days at 7 °C for the untreated product to at least 90 days after treatment at 450 MPa at 10 °C for 10 min. HP treatment had no measurable effect on the hardness of the apple pieces, but to prevent browning during the entire storage period, addition of sodium metabisulfite was necessary. This work demonstrates that HP treatment is well suited to preserve fruit pieces in syrup for extended periods with maximal quality retention.Industrial relevanceHP-treated products are increasingly finding their way to the market. There is however a need of integrated studies that translate fundamental scientific findings from laboratory-scale model systems to the complexity and scale of real food production. In this study, the processing conditions required for the inactivation of relevant spoilage and pathogenic organisms by HP on apple pieces in glucose solution were defined. Subsequently, the shelf‐life was determined in a large scale pilot experiment comprising 306 packages each containing 200 g of apple pieces in glucose solution, by evaluating both the microbiological quality and safety and color and texture during refrigerated storage after HP treatment.

► Apple pieces in syrup have been treated with high pressure at up to 600 MPa.
► Spoilage yeast Candida lipolytica inactivated by 6 log at 400 MPa, 25 °C.
► Surrogate pathogen Escherichia coli inactivated by 6 log at 600 MPa, 25 °C.
► Microbiological shelf-life extended from 15 to 90 days at 450 MPa, 10 °C.
► Hardness was not affected but metabisulfite was necessary to prevent browning.