Resistance of vegetative spoilage microorganisms to pulsed electric field (PEF) decontamination in almond-based milk alternatives

Through performance comparison of two different treatment chamber designs, this work evaluated pulsed electric field (PEF) for the decontamination of almond-based milk alternatives. Initially, microbial contaminants of almond beverages were isolated and identified through MALDI-TOF MS and/or 16S rRNA gene sequencing. Separate challenge tests were then performed in colinear and parallel chambers using Lactiplantibacillus plantarum WCFS1 serving as indicator spoiler and Pediococcus pentosaceus, one of the most frequently identified potential spoilers. A Weibull-type model was used to describe the microbial inactivation kinetics while a non-linear approach based on the F-value was used to differentiate the non-thermal from thermal effects. P. pentosaceus was found to be more resistant against PEF and thermal inactivation. Specifically, greater than 6.2 log of L. plantarum and 6.0 log CFU/mL of P. pentosaceus reductions were achieved after applying 24 kV/cm, 130 kJ/L, and 119 μs in the colinear chamber. In the parallel chamber, > 6.2 and 5.2 log CFU/mL reductions could be reached for L. plantarum and P. pentosaceus, respectively. The parallel design showed lower thermal effects and was more effective at inactivating P. pentosaceus, as indicated by the significantly lower estimates for the scale parameter, δ (P < 0.05). The findings contribute towards an improved understanding of the microbial contamination hazards in milk alternatives and PEF is proven to be an effective strategy for the elimination of spoilage microorganisms therein. Electro-technologies such as PEF could serve as a sustainable alternative for food preservation, addressing the current and future demands for high quality plant-based foods.