Influence of pulsed electric field and heat treatment on Emblica officinalis juice inoculated with Zygosaccharomyces bailii

Abstract

The effects of pulsed electric field (PEF) applying 26 kV cm(-1) with 1 mu s monopolar pulses (for 500 mu s) on inactivation of Zygosaccharomyces bailii and the stability for the key quality characteristics (vitamin C, phenolic content, antioxidant capacity, nonenzymatic index, 5-hydroxymethyl-2-furfural (HMF), degrees brix, and pH) in Emblica officinalis juice were studied. These results were then compared to those of heat treatment (90 degrees C for 60 s) up to 40 days on storing at 4 C. PEF treatment reduced 5.1 log cycles of Z. bailii with decreases in HMF concentration and browning index relative to heat treated juice. Simultaneously, PEF treated juice retained 63% of vitamin C and 88.9% of antioxidant capacity (p < 0.05). However, heat treated juice lowered 4.9 log cycles of Z. bailii and exhibited significant degradation of vitamin C and antioxidant capacity (p < 0.01). After all, both treatments did not induce any major changes in pH and degrees brix levels of emblica juice. Electron microscopy was used as a tool to find Z. bailii damage induced. Investigation of their morphology showed a leakage of cellular debris owing to the rupture of cell membrane of PEF treated Z. bailii. Thus, PEF treatment on emblica juice may offer an enormous potential for upgrading its quality than the heat processing method. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.