Pre-harvest Application of Chitosan with Carvacrol on Biochemical, Qualitative and Shelf Life Characteristics of Strawberry (Fragaria × ananassa Duch)

The increase in people's awareness of the negative effects of chemical preservatives has led to more research on the antimicrobial effect of plant essential oils and their potential to be used as preservative compounds. Strawberry (Fragaria   ananassa cv. qingxiang) is one of the most popular and widely consumed berries due to its taste, sweetness and healthy function. The taste of strawberry is related to its hardness, viscosity, sugars, protein, total soluble solid, titratable acidity content and minerals like P, K, Ca and Fe. It is a good source of polyphenolic compounds such as flavanols and has antioxidant activity. This, together with higher vitamin C content in strawberries, contributes beneficial effects on the maintenance of consumer health. Strawberry has higher antioxidant activities than orange, grape, banana, apple, etc. Strawberries are among the fruits sensitive to mechanical and physiological damage and have a fast metabolism and deterioration during the storage period. For this reason, it is necessary to use safe methods to control spoilage and maintain the quality of strawberry fruit during storage.

 The experiment was conducted in a completely randomized design, in a 5 x 4 factorial scheme (5 treatments x 4 periods evaluated), with four replications The first variable was the type of material with different concentrations in five levels including 0, 0.3%, 0.6% carvacrol, the combination of chitosan with 0.3% and 0.6% carvacrol, and the second variable was storage time in four periods including 0, 10, 20, 30 days of storage. The harvested fruits were kept at  4°C and with a relative humidity of 90±5% and parameters such as weight loss, pH, firmness of the fruit tissue, acidity (TA), soluble solids (TSS) and taste index, vitamin C, phenol and flavonoid, fruit shelf life (number of days) during the storage period were investigated and studied.

 The ANOVA results showed that the effect of the type of treatment and storage time on all investigated traits except for the firmness of the fruit texture was significant at the probability level of 1%. The fruits treated with the combination of chitosan and carvacrol 0.6% had more texture firmness, vitamin C, total phenol content and the amount of soluble solids and better shelf life than the control. In all four storage times, the highest content of total phenol (2.49 mg of gallic acid per 100 gr FW), total flavonoid (0.435 mg of Quercetin per 100 gr FW) and firmness (3.80 N) was related to the combined treatment of chitosan with carvacrol 0.6% and the lowest amount was related to the control. The firmness of the fruit tissue gradually decreased during storage, but this process was observed at a significantly slower rate in the treated fruits.

Considering the increase of 10 and 12 days of shelf life post- harvest of the combined treatment of chitosan + 0.6% carvacrol compared to other treatments and the control, hence the application of chitosan pre harvest and the use of 0.6% carvacrol edible coatings can be recommended as a safe and low-cost strategy to increase the shelf life post harvesting of 'Parus ' strawberry cultivar.