EFFECTS OF CHITOSAN/PROCYANIDIN BASED COATINGS ON QUALITY OF FRESH BLUEBERRIES DURING STORAGE

Introduction. Blueberries are known to be rich in bioactive compounds, including flavonoids, anthocyanins and phenolic acids. Neverthless fresh berry fruit deteriorates rapidly due to water loss, mold growth (?) and ripe decay (1). Edible coatings were used as an alternative way of preservation because of their ability to reduce moisture loss, solute migration, respiration and transpiration rate, to maintain firmness and generally delay senescence (2). Many studies have investigated the effects of chitosan coatings on the quality, safety and antioxidant activity of fruits. .The aim of this work was to evaluate the efficacy of an innovative edible coating, based on chitosan from mushrooms and procyanidins exract from grape seeds, on fresh blueberry quality maintenance. Materials and Methods. Two different coating solutions were prepared, each of them contained 1.5 % (w/w) of glycerol, 0.20% (w/w) of Tween® 20 and 1% (w/w) of lactic acid, solved in distilled water. In the first solution, chitosan from mushroom was added in a quantity of 1% (w/w); the second coating solution was prepared by combining chitosan from mushroom (1% w/w) and procyanidins extract from grape seeds (0.8% w/w). Whole blueberry fruit were dipped in the coating solutions, in two steps, blueberries dipped in distilled water with the same procedure were used as control. After a dehydration period of 90 min at 25° C coated berry samples were placed in plastic trays (PET) closed in micro- perforated bags (PLA) and stored at 4°C for 14 days. On coated blueberry fruits some chemico-phisical characteristics (weight loss, pH, dry matter, colour and firmness), antioxidant activity (ABTS method) and microbial growth were evaluated at 0, 2, 4, 6, 10, 14 days of storage. Results. For weight loss, pH and dry matter no differences were detected, among the control and the differently coated berry samples at each considered storage time. Both coating types induced a general lower lightness and a more blue colour in blueberry samples as compared with control one. Chitosan and chitosan + procyanidins coatings better maintained berry fruits firmness as compared to control ones until 14 days of storage. As expected the use of coating caused a slight increase in the antiradical activity that was the highest in blueberries coated with chitosan + procyanidins. Microbiological analysis results indicate that all the considered samples resulted below the spoilage threshold for total mesophilic bacteria, yeasts, molds, lactic acid bacteria and total coliforms, during the whole period of storage. Conclusions. The used innovative coatings showed a positive effect mainly on maintaining the firmness and increasing the antioxidant activity of blueberry samples. Results from this study demostrated the efficacy of new type of coating ingredients (chitosan and natural procyanidins) to maintain the overall quality of fresh blueberries during storage.