Shelf life and sensory evaluation of orange juice after exposure to thermosonication and pulsed electric fields

Thermosonication (TS) and pulsed electric fields (PEF) represent emerging technologies for liquid food preservation. In the present study shelf life and sensory attributes of orange juice were evaluated following treatment with a combination of these technologies (TS/PEF). The juice was exposed to batch TS at 55 degrees C for 10 min followed by continuous PEF at a field strength of 40 kV/cm for 150 mu s. High-temperature short-time (HTST) pasteurisation (94 degrees C for 26 s) was used as a control. Sensory attributes (i.e. colour, odour, sweetness, acidity, flavour and overall acceptability) of different orange juices processed with TS/PEF or exposed to HTST pasteurisation were evaluated by 37 panellists using a hedonic scale (1-9 points). All sensory attributes were rated equivalent for TS/PEF- and HTST-treated juice (P >= 0.05). During the shelf life study the effect of TS/PEF on selected physical properties (pH, degrees Brix and conductivity), microbiological activity and colour stability was monitored directly after processing and following 25 degrees C storage up to 168 days. No significant change in the physical properties was detected after TS/PEF or HTST treatment during 168 days of shelf life (P >= 0.05). Although the counts for both treatments were consistently within safe levels (<1000 CFU/ml) during the 168 days of storage, overall microbial counts in TS/PEF-treated juice were higher than in thermally pasteurised juice (P < 0.05). Colour attributes showed significant differences between TS/PEF- and HTST-pasteurised juice throughout the shelf life study (P < 0.05). Although promising results have been obtained further optimisation is required in order to maximise the quality of the resulting product. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V All rights reserved.