Effect of citric acid and high pressure thermal processing on enzyme activity and related quality attributes of pear puree

Abstract

Abstract Pear puree was acidified with citric acid and was subjected to thermal (TP) and high pressure-thermal processing (HPTP). Citric acid inhibited peroxidase (POD) and polyphenol oxidase (PPO) and preserved the color of pear puree. The addition of citric acid (2%, w/w) increased total phenolic content (TPC) and oxygen radical absorbance capacity (ORAC) of pear puree by ~ 50%. POD was more sensitive than PPO to thermal and HPT inactivation. Citric acid enhanced thermal and HPT inactivation and complete inactivation of POD was observed after TP (90 °C, 7 min) and HPTP (600 MPa, 90 °C, 5 min) in acidified samples, while a maximum 60% inactivation of PPO was observed under these conditions. TP resulted in a slightly better color retention of acidified samples than HPTP under conditions of equivalent enzyme inactivation, whereas TPC and ORAC remained stable irrespective of the process. Industrial relevance This study investigated the effect of thermal and high pressure thermal processing with and without citric acid on the activity of oxidative enzymes and related quality attributes of pear puree. Citric acid inhibited enzymatic browning, protected polyphenolic antioxidants against oxidative degradation and resulted in 50% increase in antioxidant capacity when it was added at 2% (w/w). Acidified pear puree can possibly be used as an ingredient in products such as yoghurts, jams and baby food after either thermal or high pressure thermal processing due to its reduced oxidative enzyme activity, low pH, high antioxidant capacity and excellent color retention.