Effects of sequential treatments using radio frequency energy and ultraviolet light on inactivation of Bacillus cereus spores and quality attributes of buckwheat

Abstract

Buckwheat kernels were susceptible to be contaminated by heat-resistant spores. This study aimed to investigate effects of radio frequency (RF) heating, ultraviolet (UV) light and their combination treatment on the inactivation of B. cereus spores and quality attributes of buckwheat kernels. Results showed that Weibull model well fitted the inactivation curves of B. cereus spores under RF heating or UV light, and both of the two techniques had a tailing phenomenon (n < 1) in the decontamination process. But the inactivation levels of spores significantly increased by the combined treatments of RF and UV, regardless of the treatment sequence. Treatment by individual RF heating at 105 °C for 30 min or UV exposure at 5.00 mW/cm² for 60 min resulted in >2.0 log CFU/g reduction of B. cereus spores. The similar inactivation effect could be achieved with shorter processing times by combined treatments (RF temperature-holding time + UV intensity-irradiation time: 85-10 + 3.50-10, 90-0 + 2.25-10, and 95-5 + 1.00-10). Besides, the colors, antioxidant compounds and antioxidant activities of buckwheat were not significantly deteriorated after these combined treatments, but the enzymatic activities were reduced, which was beneficial for long-term storage. Therefore, the proposed sequential treatment of RF heating and UV light in this study holds great potential to assure the food safety of grains.

Keywords: Buckwheat kernels; Decontamination efficiency; Food quality; Radio frequency heating; Ultraviolet light.