An approach to improve the safety and quality of ready‐to‐eat blueberries

Abstract

Bioactive edible coatings were developed and applied to blueberries as a natural treatment. E. coli O157:H7, L. innocua, S. aureus, and P. aeruginosa were subjected to four bioactive compounds and to three film‐forming solutions (FFS). Vanillin and geraniol at low concentrations (1.2–1.8 mg/mL and 0.4–1 μL/mL) demonstrated significant inhibitory effects on all pathogens counts. Chitosan (Ch) showed a high antimicrobial activity (final counts below 2 log CFU/mL). The effectiveness of Ch plus vanillin (Ch‐Va) and geraniol (Ch‐Ge) in improving the safety were tested against pathogens inoculated on blueberries. Ch, Ch‐Va, and Ch‐Ge coatings exerted a bactericidal effect on all pathogens (from 1.24 to more than 2 log reductions). Significant reduction in yeast and mold counts was achieved with Ch (1.09 log) and Ch + Va (1.74 log). Sensory attributes of blueberries remained acceptable. Ch‐Va and Ch‐Ge were an alternative to improve the quality and safety and could be effective in extending the shelf life of ready‐to‐eat blueberries. Practical applications The present study proposes the use of natural coatings enriched with biopreservatives as a technological alternative to enhance the quality and safety of minimally processed fruits. According to the results obtained, the application of chitosan plus vanillin/geraniol coatings on fresh blueberries would allow to offer a safe product and respond the growing demand of consumers for fresh, environmentally friendly and chemical preservatives‐free foods. These findings and those obtained by the sensory evaluation support the practical application of this alternative in the minimally processed fruit industry.

Antimicrobial screening of pecan shell extract and efficacy of pecan shell extract-pullulan coating against Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus on blueberries

“…The disc-diffusion study showed that pullulan coating incorporated with pecan shell extracts were effective against S. aureus and S. enterica ( Table 1 ), but during the in vivo study on blueberry no significant effect of extract was observed. Several studies have observed this phenomenon of decreasing efficacy of bioactive compounds from in vitro to in vivo owing to slow and selective movement of compounds from coating to the fruit surface thus reducing its effectiveness during storage [ 34 , 35 ]. Studies have shown that the antimicrobial efficacy of pecan shell extract are also pathogen and strain specific [ 7 , 11 ] thus, different strains of bacteria used in the antimicrobial coating study which was not used during the disc-diffusion antimicrobial screening study may have been the reason for organism's resistance towards the shell extracts.…”

Microscopic Image Segmentation and Morphological Characterization of Novel Chitosan/Silica Nanoparticle/Nisin Films Using Antimicrobial Technique for Blueberry Preservation

“…The analyses of microbial contamination such as aerobic bacteria, molds, and yeasts counts were evaluated at an interval of three days and carried out up to nine days during storage according to the methodology described by Bambace et al [ 44 ]. Aerobic bacteria, molds, and yeasts were performed using a rose bengal medium (GB4789.15-2016) and (GB4789.2-2016), respectively.…”

Improving ready‐to‐eat apple cubes' safety using chitosan‐based active coatings

“…In order to obtain biopreservatives-enriched chitosan solutions, a portion of 1.5% Ch solution was added with 1.8 mg/ml of vanillin (Sigma-Aldrich, Argentina), obtaining Ch-V treatment (1.5% chitosan coating enriched with 1.8 mg/ml vanillin), meanwhile another portion of the base coating was enriched with 1 μl/ml of geraniol (Sigma-Aldrich, Argentina), obtaining Ch-G solution (1.5% chitosan coating enriched with 1 μl/ml geraniol). The concentrations used for the bioactives enrichment correspond to the minimum inhibitory concentration of each compound previously obtained by Bambace, Gerard, and Moreira (2019).…”