Evaluation of thermal and high hydrostatic pressure processed apple purees enriched with prebiotic inclusions

The effects of high hydrostatic pressure (500 MPa/1.5 min/20 degrees C) and mild conventional pasteurization (P-90> 10 min) processing on the fructan content, polyphenolic stability and physico-chemical characteristics of apple purees enriched with two commercial prebiotics [Beneo GR (R) (inulin) and HSI (R) (fructooligosaccharides-FOS)] over 30 days at 4 degrees C were evaluated. Fructan analysis showed that the prebiotics were stable throughout 30 days and were present in sufficient quantities to deliver a prebiotic effect. Fluctuations in physico-chemical characteristics were more evident in purees containing inulin than FOS. Sensory acceptability of purees was deemed acceptable (>3) by panellists and showed no preference for either processing type. Minor deterioration in acceptability was observed in thermal processed samples containing inulin inclusions during storage (p<0.05). Processing reduced (p<0.05) the levels of some polyphenolic compounds in all samples compared to unprocessed controls, in particular chlorogenic acid and phloridzin, which were largely responsible for overall decreases in total phenolic index (TPI). Industrial relevance: Studies have shown that high hydrostatic pressure processing (HHP) can better retain inherent functional components i.e. antioxidant compounds, compared to mild pasteurization. However, processors need to be assured that further additions of functionally beneficial components, such as prebiotics, are similarly protected. This study focussed primarily on assessing the effect of thermal and HHP on the stability of two prebiotics over storage (30 days at 4 degrees C). Results indicate that both prebiotics were stable and present in sufficient quantities to deliver a prebiotic effect for both processing types after storage. In some cases, less hydrolysis of the prebiotic occurred in HHP purees. These outcomes could help the food industry identify the optimal processing type to maximise retention of added and inherent functional properties. (C) 2011 Elsevier Ltd. All rights reserved.