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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. • Weibull model fitted inactivation curves of spores under RF heating or UV light. • Combined treatment sequence of RF and UV did not affect the bactericidal effect. • Combined treatment can shorten the time to achieve the required spore reductions. • Insignificant quality deterioration of combination treated buckwheat was observed. [ABSTRACT FROM AUTHOR]

Alfalfa sprouts have high nutritional values when consumed raw, but are easily contaminated by food pathogens. This study aimed to evaluate effects of essential oil (EO) vapors, RF heating and their combinations on microbial inactivation, germination rate and generated sprouts' quality of alfalfa seeds at moisture contents of 7.52%, 9.53% and 11.45% wet basis (w.b.). Results showed that cinnamon oil and oregano oil vapors both had antimicrobial effects against Salmonella on alfalfa seeds and cinnamon oil vapor had a little better activity. Weibull model well fitted the Salmonella inactivation curves under RF heating. The rate of Salmonella inactivation increased but germination rate decreased with increasing temperature and moisture content of seeds. The intermittent RF treatments improved the heating uniformity and germination rate of the whole batch of seeds as compared to the continuous RF heating. The combination of intermittent RF heating and cinnamon oil vapor exhibited additive antimicrobial effects, up to 3.99–4.12 log CFU/g Salmonella reductions, and maintained the germination rate above 90%. However, for natural microbial decontamination, combined treatments only caused 0.56–0.82 log CFU/g reductions of total bacterial counts. The fresh weight, length, flavor, the content of phenolics and ascorbic acid, and antioxidant capacity of generated sprouts were not significantly impacted. The study provided an effective method for microbial control on sprouting seeds. • Salmonella inactivation rate on alfalfa seeds increased with increasing temperature and moisture under RF heating • Germination rate decreased as increasing temperature and moisture • Intermittent RF heating improved seed germination rate compared to continuous heating • RF combined with cinnamon oil effectively inactivated Salmonella on seeds and guaranteed seeds' quality [ABSTRACT FROM AUTHOR]

Microbial contamination is a persistent problem for grain industry. Many studies have shown that radio frequency (RF) heating can effectively reduce pathogens populations in low moisture foods, but there is a lack on the efficacy to decontaminate natural microbiome. The main objectives of this study were to investigate the effects of different RF heating conditions on natural microbial populations and physicochemical properties of buckwheat. In this study, 30 buckwheat samples collected from 10 different Provinces in China were analyzed for their microbial loads, and the samples with the highest microbial populations were used for further study to select the suitable RF heating conditions. The results showed that microbial loads in tested buckwheat kernels were in the range of 3.4–6.2 log CFU/g. Samples from Shanxi (SX-3) had significantly higher microbial counts than other samples. The selected four temperature-time combinations: 75 °C-20 min, 80 °C-10 min, 85 °C-5 min, and 90 °C-0 min of RF heating could reduce microbial counts to <3.0 log CFU/g in buckwheat kernels at 16.5% w.b. moisture content. Furthermore, the reduction populations of the inoculated pathogens (Salmonella Typhimurium , Escherichia coli , Cronobacter sakazakii, and Bacillus cereus) reached 4.0 log CFU/g under the above conditions, and almost 5.0 log CFU/g especially at high temperature-short holding time combinations (85 °C-5 min and 90 °C-0 min). Besides, physicochemical properties evaluation also showed the insignificant color changes and nutrients loss after RF treatment at 90 °C-0 min. Therefore, the RF heating at 90 °C-0 min holds greater potential than the other lower temperature-longer holding time combinations for applications in buckwheat pasteurization. • Effects of RF heating on microbial populations and physicochemical properties of buckwheat were determined. • Samples from Shanxi had significantly higher microbial counts than others. • Selected four temperature-time combinations resulted in required microbial reductions. • Insignificant color changes and nutrient losses in RF treated buckwheat were observed. [ABSTRACT FROM AUTHOR]