Food grade nanoemulsion development to control food spoilage microorganisms on bread surface.

In this study, the effect of emulsifier mixture and their concentrations on the development of nanoemulsion was studied. The impact of sonication and microfluidization processing conditions on the physicochemical properties and in vitro antimicrobial activity was also evaluated. The optimal nanoemulsion formulation was then evaluated on bread surface against B. subtilis. Results showed that a hydrophilic-lipophilic balance HLB = 12 and emulsifier: oil ratio of 1:1 allowed the formation of stable nanoemulsion. Also, both microfluidization and sonication allowed the formation of nanoscale-emulsion. Sonication treatment for 10 min allowed a maintain the total flavonoid content and a slight reduction of total phenol content. Furthermore, employing sonication resulted to the lowest polydispersity index suggesting more stable nanoemulsion. Nanoscale-emulsion showed a good in vitro antimicrobial activity against L. monocytogenes and E. coli. The application of nanoemulsion on bread surface inoculated with B. subtilis showed a delay of the decay. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05660-5.

Antimicrobial Properties of Encapsulated Antimicrobial Natural Plant Products for Ready-to-Eat Carrots.

The antimicrobial activity of natural antimicrobials (fruit extracts, essential oils and derivates), was assessed against six bacteria species (E. coli O157:H7, L. monocytogenes, S. Typhimurium, B. subtilis, E. faecium and S. aureus), two molds (A. flavus and P. chrysogenum) and a yeast (C. albicans) using disk diffusion method. Then, the antimicrobial compounds having high inhibitory capacity were evaluated for the determination of their minimum inhibitory, bactericidal and fungicidal concentration (MIC, MBC and MFC respectively). Total phenols and flavonoids content, radical scavenging activity and ferric reducing antioxidant power of selected compounds were also evaluated. Based on in vitro assays, five antimicrobial compounds were selected for their lowest effective concentration. Results showed that, most of these antimicrobial compounds had a high concentration of total phenols and flavonoids and a good anti-oxidant and anti-radical activity. In situ study showed that natural antimicrobials mix, applied on the carrot surface, reduced significantly the count of the initial mesophilic total flora (TMF), molds and yeasts and allowed an extension of the shelf-life of carrots by two days as compared to the control. However, the chemical treatment (mix of peroxyacetic acid and hydrogen peroxide) showed antifungal activity and a slight reduction of TMF.