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Developing Radio Frequency Treatment Protocol for Controlling Salmonella in In-shell Almonds

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2011 Louisville, Kentucky, August 7-10, 2011  1110487.(doi:10.13031/2013.37204)
Authors:   M Gao, S Wang, J Tang, R Villa-Rojas
Keywords:   Almond, Heating process, Pasteurization, Postharvest quality, RF

Radio frequency (RF) treatment holds potential as a pasteurization method to control Salmonella in almonds without causing a substantial loss of product quality. Thermal resistance of Salmonella can be reduced by increasing water activity, thus a washing process was designed prior to RF treatments. A pilot-scale 27 MHz, 6 kW RF heating system was used to rapidly heat 1.7 kg washed in-shell almonds with hot air heating at 55C. The RF treatment protocol was obtained using an electrode gap of 13 cm for heating, 14 cm for drying, and followed by forced room air cooling of 5-cm thick samples. The results showed that almond temperatures above 75C at 23% moisture contents for 2-4 min RF heating could meet the requirements to achieve 5-log reduction of Salmonella. The RF treatment process for 20 min reduced the moisture content to 5.7% w.b. The RF treated almond quality was acceptable since PV, FA values and kernel colors met good quality standard used by nut industry.

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