Effects of Radio Frequency Heat Treatment to Control of <I> Aspergillus flavus Aflatoxin </I>B1 and Quality in Rice var. KDML 105 in Different Bagging Densities

Abstract

The purpose of this study was to determine the effect of radio frequency (RF) heat treatment and bagging densities on controlling Aspergillus flavus,  aflatoxin B1 and changes in cooking quality of bagged rice  var. KDML 105.  The experiment was conducted during May to September 2010 at the Postharvest Research Institute, Chiang Mai University, Thailand.  Rice sample was inoculated with A. flavus at concentration of 1×10⁶ spores per ml at 14% initial moisture content.  The three different loading densities were 85% densities loaded bagging, non vacuum full loaded bagging and vacuum full loaded bagging.  The samples were exposed to RF heat treatments at an operating frequency of 27.12 MHz with temperatures at 80, 85 and 90 °C for 1, and 3 minutes compared to non treatment as control.  The result showed that the moisture content of treated rice did not appear significantly difference between treatments. While infection of A. flavus showed the interaction between bagging densities and temperature. The result showed the infection percentages of A. flavus decreased in all bagging densities while the treatment temperature increased. Furthermore, vacuum full loaded bagging with all temperature was the best at reducing the infection of A. flavus and vacuum full loaded bagging with 90 °C RF for 3 minutes treatment also reduced the infection of aflatoxin B1.  For the cooking qualities, it was found that amylose content and the elongation radio of kernel rice increased with vacuum full loaded bagging and the increasing of RF temperature.  The texture of cooked rice was increased in hardness and cohesiveness but decreased in adhesiveness while the RF temperature increased.  Thus, vacuum packing could control A. flavus and aflatoxin B1 and with 90 °C RF heat treatment for 3 minutes and modify and resulted positively change in cooking qualities.