Preparation of fibroin/chitosan based preservatives for longan postharvest preservation

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Abstract During the last decades, the clean food regulation in the E.U. and the U.S.A., concerning the contents of toxic pesticides and preservatives in fruits has become increasingly strict, therefore, an organic preservation method is needed. Fibroin/chitosan based composite preservatives (FCCPs) for longan postharvest preservation were prepared from silk fibroin. The tensile stress at break and water uptake, which govern the efficiency of FCCPs, were adjusted by controlling the amount of polyvinyl alcohol (PVA) and beeswax additives. To preserve longans, thin films of FCCPs were coated on the fruit peels. The results showed that fibroin/chitosan films extended shelf life by about 30 days, reduced browning index and spoilage rate percentage, retarded weight loss and respiratory rate, inhibited the decrease of vitamin C, total acid and total sugar content of fresh longan fruit. The lowest loss weigh and spoilage rate were observed in the longan sample coated with composite (Fib–Chi–PVA–BW) coating. Its loss weight and spoilage rate after 20 days were 3.63% and 1.71%; after 20 days were 5.82% and 7.26%, respectively whereas, loss weight and spoilage rate of control sample after 20 days were 11.48% and 23.29%. The presence of PVA (high biocompatibility, low tendency for protein adhesion, and low toxicity) and beeswax (a natural wax produced by honey bees) was found to increase the preservation potential of FCCPs. It is proposed that PVA increases the tightness and durability of the film while beeswax increases the hydrophobicity of FCCPs and reduces moisture loss of fruits. The results also showed that FCCPs can extend the shelf‐life of longan fruits up to 30 days of storage at 5 °C and relative humidity of 90–95%, indicating their potential as an attractive alternative to improve the quality of fresh fruits during storage.