Mild heating and ambient storage following gaseous chlorine dioxide treatment of chia seeds enhanced inactivation of Salmonella spp.

Abstract

Chlorine dioxide (ClO2) gas is widely recognized as a potent antimicrobial agent effective against various microorganisms. Chia seeds are prone to microbial contamination, and thermal treatments are not feasible due to potential quality issues. The study is aimed at investigating the effectiveness of chlorine dioxide (ClO2) gas followed by mild heat for Salmonella reduction in chia seeds. Chia seeds were inoculated with a five-strain Salmonella cocktail and treated for 2 h at two conditions – 5 mg/L gas concentration at 80% RH and 3 mg/L at 90% RH. The samples subjected to ClO2 were mild heat treated at 40 and 60 °C for either 1 or 2 h, and Salmonella reduction is determined during one month of ambient storage. At 80% RH, ClO2 resulted in a 1.80 log reduction of Salmonella while a significantly (p < 0.05) higher log reduction of 2.82 log CFU/g was achieved at 90% RH. Subsequent mild heat treatment at 60 °C for 2 h resulted in additional log reductions of 1.14 and 1.32 for 80% and 90% RH. During the storage study, it was observed that the Salmonella population continued to decline over time. After 7 days of storage, samples treated with ClO2 at 80% and 90% RH without the application of mild heating, provided a cumulative log reduction of 2.87 and 3.81 after 7 days of storage. ClO2 treatment (3 mg/L at 90% RH) followed by mild heating (60 °C for 2 h) and 7 days of storage achieved close to 5 log reduction. The quality of chia seeds was minimally affected by ClO2 treatment, both alone and in combination with mild heating, as indicated by the insignificant changes in color values, fatty acids, and phenolic content, germination ability, and byproduct residues. This study demonstrates the effectiveness of post ClO2 mild heating and subsequent storage to enhance the microbiological safety of chia seeds.