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Staphylococcus aureus is a common contaminant in artisanal raw-milk cheeses. Tolerance of S. aureus to biocides is a threat to disinfection in the cheese production environment, while antibiotic resistance and enterotoxin production are additional health concerns. This study aimed to evaluate the tolerance of S. aureus isolated from Minas artisanal cheeses to the biocides benzalkonium chloride, hexadecylpyridinium chloride, cetrimide, triclosan, hexachlorophene, and chlorhexidine, and the simultaneous occurrence of genes coding for antibiotic resistance (mecA, aacA-aphD, and tetK), efflux pumps [qacA/B and smr (qacC/D)], and enterotoxins (sea, seb, sec, sed, see, seg, seh, sei, and sej). Among the tested isolates, 38.2% were resistant to at least one biocide, and 73.1% were positive for one or more antibiotic resistance gene. Most of the biocide-tolerant and antibiotic-resistant isolates harbored efflux pump genes, and were positive for at least one staphylococcal enterotoxin gene. The study highlights the need for correct hygiene monitoring programs to ensure the safety of these products.

Olive paste can be a valuable source of phenolic compounds with antioxidant activity. High hydrostatic pressure (HHP) treatment (600 MPa, 8 min) was tested for the preservation of olive paste obtained from Picual unfermented green olives, a variety known for its high content of phenolic compounds. Microbiological load (total aerobic mesophilic counts, yeasts, and moulds), and antioxidant activity were measured during one-month refrigeration storage. At the end of the storage period, control samples maintained 27% of their initial antioxidant activity, showed browning, and had microbial loads (ca. 105 CFU/g) composed mainly of yeasts and moulds, while samples treated with HHP preserved 79% of their initial antioxidant activity, kept green colour and had no microbial counts. These results showed the potential of HHP treatment at 600 MPa for 8 min for the preservation of olive paste with strong antioxidant activity.

Las bacteriocinas son péptidos sintetizados por bacterias que presentan un amplio potencial como conservador de alimentos. Son una buena alternativa para reemplazar los aditivos químicos y producir alimentos mínimamente procesados. Las bacteriocinas que se han estudiado con mayor interés en la industria alimentaria son las derivadas de bacterias ácido-lácticas (bal) porque tienen el estatus Generally Regarded As Safe (gras). No obstante, se ha determinado que las bacteriocinas tienen ciertas desventajas a la hora de aplicarlas en los alimentos, especialmente en derivados lácteos. Esas desventajas pueden enmendarse al combinar las bacteriocinas con otros tratamientos emergentes en la industria alimentaria. El objetivo de esta revisión fue realizar un análisis sobre las principales bacteriocinas utilizadas y su efecto sinérgico contra bacterias patógenas y/o alteradoras, cuando se aplican de manera combinada con otros tratamientos como sustancias químicas, sistema lactoperoxidasa, altas presiones hidrostáticas, nanopartículas, bacteriófagos y aceites esenciales. Los resultados de esta revisión indican que cuando se aplican las bacteriocinas con otros tratamientos pueden aumentar la actividad antimicrobiana, lo cual mejoraría la seguridad alimentaria. Se concluye que las mejores combinaciones del uso de las bacteriocinas y tecnologías emergentes son bacteriocinas y nanopartículas y bacteriocinas con bacteriófagos, cuyas combinaciones inhiben el crecimiento tanto de bacterias Gram positivas como de Gram negativas, entre las ventajas están, fáciles de aplicar en los alimentos, pueden ser de bajo costo, no cambian las características sensoriales del producto, permiten combatir la resistencia antimicrobiana, y destruyen completamente a los microorganismos sin darles oportunidad de recuperación durante el periodo de maduración o almacenamiento.

High hydrostatic pressure (HP) is a promising method to improve the microbiological quality of sous-vide foods. Monitoring the composition and behavior of the microbial communities in foods is of most importance for the production of high-quality and safe products. High-throughput sequencing (HTS) provides advanced approaches to determine food’s microbial community composition and structure. The aim of the present study was to determine the impact of different HP treatments on the microbial load and bacterial diversity of sous-vide Atlantic cod. Sous-vide cooking at 57.1 °C for 30 min followed by HP treatment at 500 MPa for 8 min reduced viable cell counts (total aerobic mesophiles) in the cod samples below detectable levels for 45 days of storage under refrigeration. In a second trial with cod cooked sous-vide at 52 °C for 20 min followed by HP treatments at 300 or 600 MPa (with HP treatment temperatures of 22 °C or 50 °C for 4 or 8 min, depending on treatment), only the treatments at 600 MPa delayed bacterial growth for at least 30 days under refrigeration. The optimal HP conditions to improve the microbiological quality of sous-vide cod cooked at low temperatures were obtained at 600 MPa for 4 min at a pressurization temperature of 50 °C. Bacterial diversity was studied in cod cooked sous-vide at 52 °C for 20 min by HTS. In the absence of HP treatment, Proteobacteria was the main bacterial group. A succession of Pseudomonadaceae (Pseudomonas) and Enterobacteriaceae was observed during storage. Firmicutes had low relative abundances and were represented mainly by Anoxybacillus (early storage) and Carnobacterium (late storage). The HP-treated sous-vide cod showed the greatest differences from controls during late storage, with Aerococcus and Enterococcus as predominant groups (depending on the HP conditions). The application of HTS provided new insights on the diversity and dynamics of the bacterial communities of sous-vide cod, revealing the presence of bacterial genera not previously described in this food, such as Anoxybacillus. The significance of Anoxybacillus as a contaminant of seafoods should be further investigated.

The effects of high-hydrostatic pressure (HP) treatments (450 and 600 megapascals, MPa, for 5 min at temperatures of 22 °C and 50 °C) on the microbiota of a coriander and parsley dressing was studied via culture-dependent and culture-independent approaches. Samples were refrigerated for 20 days, with periodic counts of the culture media supplemented with, or without, antimicrobials. HP-treated samples showed significantly lower viable cell counts compared to untreated controls. Only the control samples yielded bacterial growth on media with antimicrobials (imipenem, cefotaxime, benzalkonium chloride), including mostly Pseudomonas and Lactobacillus. Bacillus and Paenibacillus were identified from pressurized samples. Few isolates showed higher tolerance to some of the biocides tested. Pseudomonads showed outstanding resistance to meropenem and ceftazidime. According to high-throughput sequencing analysis, the microbiota of the dressing control samples changes during storage, with a reduction in the relative abundance of Proteobacteria and an increase in Firmicutes. The composition of the residual microbiota detected during storage was highly dependent on the pressure applied, and not on the treatment temperature.