相较于传统烘烤方式,热风辅助射频(hot air-assisted radio frequency, HA-RF)技术用于坚果烘烤展现出巨大的优势。为探究HA-RF烘烤处理对扁桃仁抗氧化性以及微生物安全性的影响,该研究使用3种烘烤强度处理扁桃仁:HA-RF1(目标温度130 ℃,加热时间11 min,保持时间4 min)、HA-RF2(目标温度155 ℃,加热时间15 min)和HA-RF3(目标温度155 ℃,加热时间15 min,保持时间19 min),测定处理前后的色度和抗氧化性,并检测粪肠球菌(沙门氏菌替代菌)数量。结果表明,HA-RF烘烤后,扁桃仁的ABTS阳离子自由基清除能力提高,Fe3+还原能力增强,整体抗氧化性得到提升。扁桃仁初始水分活度(aw)为0.65时,传统热风烘烤(155 ℃,20 min)仅能将粪肠球菌减少2 lg CFU/g左右,而HA-RF1可减少4 lg CFU/g以上,HA-RF3对粪肠球菌杀灭效果最好,可以降低7 lg CFU/g左右。综合分析可知,HA-RF烘烤可以提升扁桃仁的抗氧化性,有效减少粪肠球菌的数量,达到巴氏杀菌效果,比传统HA烘烤更能保证扁桃仁的微生物安全,研究结果可为HA-RF在扁桃仁中的应用提供指导。
Hot air-assisted radio frequency (HA-RF) has great advantages in roasting of nuts compared to traditional roasting methods.To investigate the changes in antioxidant properties and pathogenic microorganisms of almond kernels during HA-RF roasting, almond kernels were roasted by three intensities, including HA-RF1 (target temperature 130 ℃, heating time 11 min, holding time 4 min), HA-RF2 (target temperature 155 ℃, heating time 15 min), and HA-RF3 (target temperature 155 ℃, heating time 15 min, holding time 19 min).Color, antioxidant properties, and the population of Enterococcus faecalis were determined before and after HA-RF treatments, where E.faecalis was used as a surrogate for Salmonella.After HA-RF roasting, ABTS cationic radical scavenging capacity and Fe3+ reduction capacity of almond kernels were increased, and overall antioxidant properties were improved.When the initial water activity (aw) of almond kernels was 0.65, hot air (HA) roasting (155 ℃, 20 min) only reduced E.faecalis by about 2 lg CFU/g.In contrast, HA-RF1 reduced E.faecalis by more than 4 lg CFU/g, and HA-RF3 exhibited the most effective killing effect, reducing it by 7 lg CFU/g.HA-RF roasting enhanced antioxidant properties of almond kernels and effectively pasteurized pathogens, which ensured superior microbiological safety compared to traditional HA roasting.This study provided basis for application of HA-RF in almond kernels.
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