Evaluation of Mechanical and Chemical Parameters of Okra with Chitosan Coating in Nano Packaging Films and Atmospheric Modified Conditions

The quick deterioration of fruit and vegetables has led researchers to find a solution to increase the shelf life. Foodstuff packaging is a vital technology to maintain freshness, prevent deterioration, and physiological and mechanical damages, and increase the shelf life of fresh products. Employing various post-harvest technologies prevent light, heat, and humidity transmission and control the microorganism activity, thereby reducing the cost and maintaining the quality of fresh and processed products during storage. Fresh okra has a shelf life of 10 days and is stored at 1-10°C due to high respiration rate and moisture loss. Today, the use of nanotechnology in the packaging industry is developed and expanded. The aim of the packaging is to increase the shelf life and prevent bacterial and shipping damages, as well as control the humidity and gases transmission, thereby reducing food spoilage. Modified atmospheric packaging (MAP) is one of the famous methods for increasing the shelf life of fresh products in which the aging process is reduced by increasing CO2 and decreasing. Decreasing the respiration rate, producing ethylene, and metabolic reactions in the modified atmosphere lead to a reduction in product deterioration. The use of coatings and edible films is being increased in order to maintain sensitive features like flavors, fragrances, and the appearance of different products and increase the shelf time of fruits and vegetables. Chitosan edible coating is a non-fragrance and non-flavor polysaccharide with a high molecular weight that is widely used because of its antifungal, biological, and biochemical properties. Chitosan is a natural polymer obtained from chitin, which is abundantly found in crustacean shells. The aim of the present study is to evaluate the effect of packaging films and chitosan coating under the modified atmosphere storage condition on qualitative and quantitative parameters of okra during storage.

The process of present research was performed in the Laboratory of Mechanical Properties and Rheology of the Biosystem Engineering Department, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, in 2016. Okra cv. Kano Dwarf was selected due to its short post-harvest life and provided by farms in Kermanshah Province. Okras were handpicked and they were free of any spots, contamination, or decay, with the almost same size and shape, without any mechanical and microbial damage. The treatments of the present study were chitosan covering, modified atmosphere by a gas mixture of 5% O2 + 10 CO2 + 85% N2, three types of packaging films including silicone nano-emulsion (Nano Bespar Aytak Co.), nano-polyethylene, and light polyethylene (LFO200), as well as two temperature levels of 1 ± 4°C (refrigerator) and 1 ± 25°C (room temperature). The influence of modified atmospheric treatments, chitosan coatings, and packaging films at two storage temperatures on chemical factors (pH and TSS) and mechanical properties including shear stress (TB), shear force (FB), shear modulus (GK) were evaluated at the end of 12 days of storage in a completely randomized design with a factorial experiment in three replications on Okra.

Among the films used, silicon nano emulsion film and chitosan coating were more able to maintain TSS. The pH value decreased due to the control of respiratory rate and corruption under modified atmospheric conditions. The mechanical properties of the samples showed that the shear stress changes of the coated sample were significantly less than the untreated ones compared to the beginning of the maintenance period. The sample stored at 4°C had less shear force during the storage period than similar specimens at 25°C. The modified atmosphere caused the shear modulus to decrease with increasing storage time compared to the beginning of the storage period.

The results of the present research revealed that silicon nano-emulsion film has a higher capability in preserving the qualitative and quantitative properties of okra compared to other studied films. Between the two studied temperatures, 4°C storage temperature had better performance in preserving qualitative and quantitative properties of the okra compared to 25°C. The controlled atmosphere increases okra's shelf life due to reduced respiration rate. In general, maintenance of the products in a modified atmosphere package preserves the quality of the products and extends their shelf life.