Pasteurization of raw almonds using pulsed light combined with prior water dipping

Authors: LIU, XUANJING - University Of Delaware; Fan, Xuetong; WANG, WENLI - University Of Delaware; YAO, SHIYUN - University Of Delaware; CHEN, HAIQIANG - University Of Delaware

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2021
Publication Date: 1/27/2021
Citation: Liu, X., Fan, X., Wenli, W., Yao, S, Chen, H. 2021. Pasteurization of raw almonds using pulsed light combined with prior water dipping. International Journal of Food Microbiology. https://doi.org/10.1016/j.foodcont.2021.107946.
DOI: https://doi.org/10.1016/j.foodcont.2021.107946

Interpretive Summary: United States is the largest and dominant supplier of almonds around the world. However, several outbreaks and recalls linked to almonds contaminated with Salmonella in recent years have raised concerns about their safety. Therefore, effective decontamination technologies are needed to meet the requirement of 99.99% reductions of the pathogen by the industry. In this study, we investigated the efficacy of pulsed light treatments in inactivating Salmonella inoculated on raw almonds. Results showed that pulsed light in combination with prior water dipping achieved more than 99.999% reduction of the pathogen without adverse effects on product quality. As a rapid disinfection method with high microbial reduction efficacy for the low-moisture food industry, the wet pulsed light treatment could be potentially used as an alternative to traditional technologies to pasteurize nuts

Technical Abstract: The purpose of this study was to evaluate the potential of using pulsed light (PL) to pasteurize raw almonds. PL treatment of dry almonds was found to be not effective and detrimental to the almond quality due to the excessive heat generated by PL. Dipping almonds in water before PL treatment enhanced the inactivation of Salmonella dipped-inoculated on almonds and better preserved almond quality by slowing down the temperature increase through water evaporation from almonds. The effect of PL intensity, treatment time, almond sample size, and times of almond dipping in water on Salmonella inactivation was determined. All these parameters played an important role in the inactivation of Salmonella. Increasing the PL intensity and extending the PL treatment time resulted in greater Salmonella inactivation. On the contrary, increasing the almond sample size from 50 g to 500 g and number times of water dipping from one to two slowed down Salmonella inactivation. The one-time dipping of almonds in water for 1 min and then a PL treatment of 500 g of almonds at an intensity of 0.75 W/cm2 for 18 min could achieve a > 5 log reduction of Salmonella and resulted in less damage to almond appearance and color. This treatment was therefore chosen to process 500 g of un-inoculated almonds for color and quality analysis. This treatment slightly affected the almond color, but did not significantly increase the lipid oxidation of almonds. No much difference in the appearance and color of almond between the untreated control and the PL-treated almonds was observed visually. Therefore, it was concluded that this PL treatment in combination with prior water dipping could be a potential pasteurization method for raw almonds.