Thermal Inactivation Kinetics and Radio Frequency Control of Aspergillus in Almond Kernels

Abstract

Mold infections in almonds are a safety issue during post-harvest, storage and consumption, leading to health problems for consumers and causing economic losses. The aim of this study was to isolate mold from infected almond kernels and identify it by whole genome sequence (WGS). Then, the more heat resistant mold was selected and the thermal inactivation kinetics of this mold influenced by temperature and water activity (aw) was developed. Hot air-assisted radio frequency (RF) heating was used to validate pasteurization efficacy based on the thermal inactivation kinetics of this target mold. The results showed that the two types of molds were Penicillium and Aspergillus identified by WGS. The selected Aspergillus had higher heat resistance than the Penicillium in the almond kernels. Inactivation data for the target Aspergillus fitted the Weibull model better than the first-order kinetic model. The population changes of the target Aspergillus under the given conditions could be predicted from Mafart’s modified Bigelow model. The RF treatment was effectively used for inactivating Aspergillus in almond kernels based on Mafart’s modified Bigelow model and the cumulative lethal time model.

Applications of Radio Frequency Heating in Food Processing

“…RF drying has been widely used to replace conventional dehydration methods for improving product quality and storage stability [ 4 , 5 , 6 ]. Based on thermal inactivation kinetics, RF energy has been applied to control pests and pathogens [ 7 , 8 , 9 ] in foods and agricultural products, shortening treatment time but maintaining product quality [ 10 ]. RF heating could also be used in the food industry to roast nuts since RF-roasted almonds were found to have a better flavor, texture, and overall preferability compared to commercial almonds [ 11 ].…”