Non-thermal pasteurization of apples in syrup with dense phase carbon dioxide
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The study investigated dense phase carbon dioxide (DPCD) applicability to a solid-liquid product consisted of apples in syrup as an alternative to the conventional thermal pasteurization. The effect of pressure (8,10, and 12 MPa) and temperature (35, 45, and 55 degrees C) at 15 min was investigated to determine the inactivation of the natural microbiota (mesophilic microorganisms, total coliforms, yeasts and molds) and polyphenol oxidase enzyme. The optimal process conditions (12 MPa, 55 degrees C, 15 min) were determined. A storage study at 25 degrees C for 60 days was also performed to monitor the microbial, enzymatic and quality (pH, color, ascorbic acid content and total acidity) stability of the product. DPCD induced inactivation to undetectable levels of mesophilic microorganisms, total coliforms, yeasts and molds. At the same conditions, polyphenol oxidase was totally inactivated while pH, color, and total acidity were slightly affected. The shelf life study of DPCD treated products revealed their microbial, enzymatic and quality stability.