Abstract
In-shell pecans are susceptible to microbial contamination. This study was performed to investigate feasibility of using hot water treatment as a kill-step for food-borne pathogens during pecan shelling. In-shell pecans were subjected to hot water at 70, 80 or 90 °C for 1, 2, 3, 4 or 5 min. The time-temperature treatments to achieve a 5-log reduction of Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes, and non-pathogenic Enterococcus faecium were determined. Thermal death values were determined for each tested condition. L. monocytogenes was most susceptible to heat treatment and were reduced by 4.6 ± 0.35 log CFU/g at 70 °C for 5 min, while 3–5 min at 80 and 90 °C treatments was required to achieve a similar reduction level for S. enterica, E. coli O157:H7, and E. faecium. S. enterica were most resistant and required 4 min treatment time to achieve a 5-log reduction at 80 and 90 °C. The D-values ranged from 1.15 to 1.72, 0.83 to 1.19, and 0.41–0.92 min at 70, 80 and 90 °C, respectively. E. faecium had the highest D-value (1.72 min at 70 °C), indicating a potential surrogate for process validation for pecan industries. Utilizing proper hot water treatment during pecan shelling could reduce food safety risk.
Highlights
Low-moisture foods such as tree-nuts with water activity lower than 0.7 are presumed to be low-risk food (Blessington, Theofel, & Harris, 2013; Harris, 2012)
The reduction of E. coli O157:H7 when treating pecans with hot water is shown in Fig. 1 (b)
Similar results were reported by Bianchini et al (2014) when balanced carbohydrate-protein meal was subjected to heat treatment. They observed a 5 log reduction of E. faecium and S. enterica at 73.7 and 60.6 °C, respectively, when the extruder was operated for 5 min after reaching desired temperature. These findings and the results from our study indicate that E. faecium is more resistant to heat treatment as compared to bacterial pathogens such as S. enterica, E. coli O157:H7 and L. monocytogenes
Summary
Low-moisture foods such as tree-nuts with water activity lower than 0.7 are presumed to be low-risk food (Blessington, Theofel, & Harris, 2013; Harris, 2012). A quantitative risk assessment study by Farakos et al (2017) shows that there is a possibility of risk of salmonellosis in U.S population on consumption of Salmonella contaminated pecan They reported that the shelling process of pecans during postharvest treatments and acquiring illness at home by consuming uncooked pecans are well correlated. Beuchat and Mann (2011) and Harris, Uesugi, Abd, and McCarthy (2012) demonstrated the efficacy of hot water treatment to reduce S. enterica by 5 log CFU/g from pecans and almonds, respectively. These studies do not evaluate the effect of hot water treatment on inactivation of pathogens like E. coli O157:H7 and Listeria monocytogenes
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