Secondary growth is a common post-harvest problem when pre-infected crops are attacked by filamentous fungi during storage or processing. Several antifungal approaches are thus pursued based on chemical, physical, or bio-control treatments; however, many of these methods are inefficient, affect product quality, or cause severe side effects on the environment. A protein that can potentially overcome these limitations is the antifungal protein AFP, an abundantly secreted peptide of the filamentous fungus Aspergillus giganteus. This protein specifically and at low concentrations disturbs the integrity of fungal cell walls and plasma membranes but does not interfere with the viability of other pro- and eukaryotic systems. We thus studied in this work the applicability of AFP to efficiently prevent secondary growth of filamentous fungi on food stuff and chose, as a case study, the malting process where naturally infested raw barley is often to be used as starting material. Malting was performed under lab scale conditions as well as in a pilot plant, and AFP was applied at different steps during the process. AFP appeared to be very efficient against the main fungal contaminants, mainly belonging to the genus Fusarium. Fungal growth was completely blocked after the addition of AFP, a result that was not observed for traditional disinfectants such as ozone, hydrogen peroxide, and chlorine dioxide. We furthermore detected reduced levels of the mycotoxin deoxynivalenol after AFP treatment, further supporting the fungicidal activity of the protein. As AFP treatments did not compromise any properties and qualities of the final products malt and wort, we consider the protein as an excellent biological alternative to combat secondary growth of filamentous fungi on food stuff.
Strawberry fruits have a very short shelf‐life owing to their high degree of perishability. This study aimed to determine the efficacy of chitosan (CH) incorporated with olive oil residues (OOR) coatings on overall quality of cold‐stored strawberry fruits compared to watery wax incorporated with thiabendazole. Strawberries were sprayed after infected with Rhizopus stolonifer with six different coating formulas and uncoated fruits. Indeed, all freshness and microbiological parameters were significantly increased in uncoated fruits compared to coated fruits. Amazingly, the coated strawberry using CH‐OOR 2% was reduced significantly the gradual decline in their contents of total phenolics, flavonoids and their antioxidants. Likewise, it was the lowest fruits in decayed area, fungal count and malondialdehyde development. Then, fruits were coated with CH‐OOR showed uniform coating distribution, since it was impossible to see any pores. Therefore, coating treatments with CH‐OOR was improved the membrane integrity and increased the keeping quality.
Practical Applications
Edible coatings could be an effective way for delaying the ripening process and extending the shelf‐life stability of strawberry during postharvest. The effectiveness of chitosan (CH)‐olive oil residue (OOR) as a novel edible coating, in comparison with watery wax‐thiabendazole was approved. The applicability of those films to maintain microbiological and freshness quality in strawberry during postharvest was succeed. Incorporation of OOR into CH increased its antifungal property against R. stolonifer in vivo and in vitro. Coating by CH‐OOR reduced phenolics, flavonoids and antioxidants decomposition in coated fruits compared to uncoated. CH‐OOR was able to slow down the gas exchange by reducing the CO2 of coated strawberry, which reduced their malondialdehyde development. Commercially, CH‐OOR could be explored as a novel and potential natural coating to substitute the synthetic agents in fruit packaging industries. The coating cost could increase the total cost about 6–8% where shelf‐life and keeping quality was improved.
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