Optimization of water curing for the preservation of chestnuts (Castanea sativa Mill.) and evaluation of microbial dynamics during process

• Water curing is still the most commonly used method to inhibit fungi infecting chestnuts.
• Water curing produces a lot of wasted water and its effectiveness has never been fully explained.
• A Lactobacillus pentosus strain was used as adjunct culture during water curing.
• A reduction of the environmental impact of the process was attempted by waters recycling.
• The evolution of total microflora and LAB was followed by means of a polyphasic approach.

Chestnuts are very perishable fruits, whose quality may be compromised during postharvest handling. Damage can be caused both by insects and fungi. Water curing, a commonly used postharvest method, is based on soaking fruits in water typically for about one week. Factors that affect effectiveness of water curing have only been explained partially. A decrease in pH, likely imputable to a light fermentation caused by lactic acid bacteria, may inhibit the growth of moulds. In this study a Lactobacillus pentosus strain was selected for its ability to inhibit fungi, and used as a starter culture during water curing. As second goal, a reduction of the environmental impact of the process was evaluated by using water that had been re-cycled from a previous curing treatment. Experiments were performed on pilot as well as on farm scale. In all trials, microbial dynamics were evaluated by means of a polyphasic approach including conventional and molecular-based analyses. According to results, the employment of an adjunct culture appears as a very promising opportunity. Even if no reduction in the duration of the process was achieved, waters exhibited a minor microbial complexity and fruits did not lose the natural lustre after the process.