The effect of salt reduction on the growth of food spoilage bacteria in model broth systems and salt-adjusted ready meals

The effect of reducing salt levels on the growth of food spoilage bacteria was investigated. In broth, no significant differences in growth of all strains were apparent at the lower salt concentrations (0-1.5% salt), while at 3.0% salt (w/v), final populations of Escherichia coli, Pseudomonas fluorescens and Lactobacillus plantarum were reduced. In three experimental ready meals, the effect of varying the salt levels over the range of 3.0-0.2% (w/w) was investigated for the growth of E. coli and Staphylococcus aureus. Generally, little inhibition of growth of either strain was noted, except for E. coli where populations were ∼1 log₁₀ cycle lower only in the low salt chicken curry meal at highest added salt content. Overall, decreasing salt levels from ∼3% downward did not markedly affect the growth of any of the bacterial strains studied in either broth or ready meals. Practical Applications: This study may have significance in the manufacture of reduced salt foods where concerns regarding the impact of salt reduction on microbial quality may preclude a meaningful lowering of added salt levels. While growth models exist for cultures in broths with varying added salt levels, no such data exists for food matrices such as complex ready meals where growth may differ from broth models. Overall, this study of ready meals with altered salt contents suggests that significant salt reduction is achievable without compromising product safety for the microbial strains tested. Data suggest that a large-scale salt reduction program is technically feasible for these particular products, although a case by case investigation is required to ensure all low salt foods are comparable, in terms of microbial safety with commercially available regular salt counterparts. Therefore, these scientific findings have direct practical industrial applications for ready meal manufacturers.