Wetting raw almonds to enhance pulse light inactivation of Salmonella and preserve quality

Abstract

The overall goal was to explore 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 effects of PL intensity, treatment time, almond sample size, and times of almond dipping in water on Salmonella inactivation were 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 other hand, 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 followed by a PL treatment of 500 g of almonds at an intensity of 0.75 W/cm2 for 18 min could achieve at least 5 log reduction of Salmonella. Hence, this treatment was 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 both immediate after processing and after storage at 39 °C for 11 days. No significant difference in the appearance and color of almond between the untreated control and the PL-treated almonds was observed visually. Therefore, this PL treatment in combination with prior water dipping could be a potential pasteurization method for raw almonds.