Aims:  To determine structure–function relationships of antibacterial phenolic acids and their metabolites produced by lactic acid bacteria (LAB). Methods and Results:  Minimum inhibitory concentrations (MICs) of 6 hydroxybenzoic and 6 hydroxycinnamic acids were determined with Lactobacillus plantarum, Lactobacillus hammesii, Escherichia coli and Bacillus subtilis as indicator strains. The antibacterial activity of phenolic acids increased at lower pH. A decreasing number of hydroxyl groups enhanced the activity of hydroxybenzoic acids, but had minor effects on hydroxycinnamic acids. Substitution of hydroxyl groups with methoxy groups increased the activity of hydroxybenzoic, but not of hydroxycinnamic, acid. Metabolism of chlorogenic, caffeic, p‐coumaric, ferulic, protocatechuic or p‐hydroxybenzoic acids by L.  plantarum, L. hammesii, Lactobacillus fermentum and Lactobacillus reuteri was analysed by LC‐DAD‐MS. Furthermore, MICs of substrates and metabolites were compared. Decarboxylated and/or reduced metabolites of phenolic acids had a lower activity than the substrates. Strain‐specific metabolism of phenolic acids generally corresponded to resistance. Conclusions:  The influence of lipophilicity on the antibacterial activity of hydroxybenzoic acids is stronger than that of hydroxycinnamic acids. Metabolism of phenolic acids by LAB detoxifies phenolic acids. Significance and Impact of the Study:  Results allow the targeted selection of plant extracts for food preservation, and selection of starter cultures for fermented products.

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Low-moisture foods (LMFs) have been defined as those food products with a water activity (a) less than 0.85 and are generally considered less susceptible to microbial spoilage and the growth of foodborne pathogens. However, in recent years, outbreaks linked to LMFs have increased, with Salmonella spp., Bacillus cereus, Cronobacter sakazakii, Clostridium spp., Escherichia coli O157:H7, non-O157 E. coli, and Staphylococcus aureus being the principal pathogens involved. Because of the new concerns raised as a result of recent outbreaks, new approaches need to be developed to control foodborne pathogens in LMFs. This review summarizes the recent research on novel inactivation methods suitable for use on LMFs. Among the methods discussed are the nonthermal inactivation methods as well as other novel methods such as radio-frequency and microwave heating. Additional research is needed to evaluate older technologies and develop new technologies, either alone or in combination, to understand the mechanisms of inactivation.

Results improve the understanding of the antifungal mode of action of potato secondary metabolites, which is essential for their potential utilization as antifungal agents in nonfood systems.

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Raw chia and flax seeds are increasingly associated with Salmonella contamination. However, intervention technologies for these seeds that maintain them in a raw state, without causing clumping because of mucilage production upon moisture exposure, are limited. In this study, a commercial ethanol and paracetic acid sanitizing solution meeting these criteria was evaluated for efficacy against Salmonella and Enterococcus faecium NRRL B-2354, a known Salmonella surrogate for thermal intervention technologies. Samples (100 g each) of chia and flax seeds (n = 5) were inoculated with either a cocktail of Salmonella Newport, Senftenberg, Oranienburg, Saintpaul, Typhimurium DT104, and Cubana or E. faecium NRRL B-2354. After overnight acclimatization, samples were treated with 4 mL of sanitizing solution per sample and then held at ambient temperature (20 to 25°C) for 1 h before bacterial enumeration. Separate 1-kg–treated batches were evaluated for germination ability (4 replicates of 100-g samples), as well as nutrient content and rancidity (n = 3), compared with untreated control. Following the posttreatment holding time, these batches were dried back to original moisture content at 70°C to evaporate residual sanitizing solution, thereby stopping treatment. The sanitizing solution was found to be an effective intervention method for chia and flax seeds, reducing Salmonella to below the level of detection by more than 4 and more than 5 average log CFU/g, respectively. Germination was not significantly affected (P ≥ 0.05) for chia seed. For both seeds, nutrition and rancidity were not significantly affected (P ≥ 0.05). Furthermore, E. faecium NRRL B-2354 was found to be an appropriate Salmonella surrogate for treatment of chia and flax seeds with this sanitizing solution, showing comparable but higher resistance to treatment with the sanitizing solution than the Salmonella cocktail.

The survival and virulence of Listeria monocytogenes was assessed during storage on three low-moisture foods (LMFs), chocolate liquor, corn flakes and shelled, dry-roasted pistachios (a w 0.18, 0.27, 0.20). The LMFs were inoculated with a 4-strain cocktail of L. monocytogenes at 8 log CFU/g, dried, equilibrated and then stored at 4°C, 25–81% relative humidity (RH) and 23°C, 30–35% RH for at least 336 days. At 4°C, L. monocytogenes remained stable on the LMFs for at least 336 days. At 23°C, L. monocytogenes levels declined on the chocolate liquor, corn flakes and pistachios at initial rates of 0.84, 0.88 and 0.32 log CFU/g/month, respectively. After 8 months at 23°C, L. monocytogenes concentrations on the chocolate liquor and corn flakes decreased to below the limit of detection (i.e., 0.48 log CFU/g). Relative populations of each strain were assessed before (i.e., day 0) and after 6 and 12 months of storage at 23°C and 4°C, respectively. Generally, a decline in the relative abundance of the serotype 1/2a strain was observed during storage, coupled with the relative increase of other strains, depending on the LMF and storage temperature. The total viable populations of L. monocytogenes quantified by PMAxx-qPCR after 12-plus months of storage at 4°C were significantly higher than that obtained by plating on TSA-YE by 1.8 to 3.7 logs. Decreases in the culturable population of L. monocytogenes during storage on the LMFs were the result of both cellular inactivation and transition to a viable-but-non-culturable state. The surviving cells, specifically after long-term storage at 4°C on the chocolate liquor and pistachios, remained infectious and capable of intracellular replication in Caco-2 enterocytes. These results have great relevance for predictive modeling used in microbial health risk assessments and support the addition of LMFs to food safety questionnaires conducted during listeriosis outbreaks.