Evaluation of edible film and modified atmosphere packaging on the improvement of quality and shelf life of bell pepper

Introduction: Bell peppers belong to vegetables group and contain nutrients effective in preventing and treating many diseases. However, due to shrinkage and water content loss in these products followed by a decrease in vitamins, there are some problems with their color in the interval between harvest and consumption which can be improved using packaging techniques. Bell Pepper (Capsicum annuum L.) belongs to the Solanaceae family and is one of the most popular agricultural products in various countries, especially in the Middle East. The importance of this product is not only due to its economic importance, but mainly due to the fact that it is a very good source of ascorbic acid. This type of pepper has significant amounts of insoluble fiber that can play an important role in the prevention and treatment of gastrointestinal diseases such as constipation (Park et al. 1998). Pepper is also a rich source of vitamins C, A and lycopene antioxidants, which can be effective in preventing many cancers. Despite the nutritional benefits, some of the properties of bell peppers can limit the producers of this product. For example, wrinkles and dehydration, and consequently a decrease in vitamins in pepper, are among the things that take time to supply to the consumer, reducing their appearance and nutritional value. Solutions to this problem include the use of improved packing methods, optimal storage conditions, and treatment with preservatives (Guerra et al., 2011). Packaging is a simple and effective way to protect vegetables and fruits that protects against the influence of external factors as well as preserves physical and chemical properties (stove and colleagues 2010). Today, packaging with a modified atmosphere has been widely used to increase the shelf life of fresh fruits and vegetables. Other ways to improve the shelf life of fresh vegetables include the use of edible coatings that have antibacterial properties, prevent the migration of moisture and gas, among which, chitosan due to its properties such as non-toxic, biodegradable Vulnerability and biocompatibility have been widely used in peppermint. Polymer food films are made in a thin layer that is placed on food or between food components. Oral films increase product shelf life and meet consumer demand even more than natural materials, and are less polluting to the environment. Edible coatings are usually composed of polysaccharides, proteins, lipids, or mixtures thereof (Park et al., 1994). In addition, adding essential oils to the food cover as a natural preservative can increase the antibacterial properties of the coating. Chitosan is a polymer that has many applications in the food industry and is the second most abundant natural polymer after cellulose. This polysaccharide has functional properties such as antimicrobial, antifungal and antioxidant properties, and also has properties such as environmental compatibility, informality and various physico-chemical properties. Despite extensive research on improving the quality and increasing the shelf life of bell peppers abroad, unfortunately, in our country, there has not been much research on increasing the shelf life of this product using packaging and food coatings. The aim of this study was to investigate the effect of packaging with modified atmosphere and edible chitosan coating in combination with different temperatures and times in order to maintain qualitative characteristics and increase the shelf life of bell peppers.
Material and methods: In this study, response surface methodology and central composite design were used in order to investigate the effect of Chitosan coating (0-1%), oxygen gas concentration in packaging (3-21%), storage temperature (5-20°C), and storage time duration (5-45 days) on parameters of decrease percentage in weight, Hardness, vitamin C, and color properties (L*, a*, b* components). The ripe peppers were harvested from the greenhouse and after being disinfected with Sodium hydrochloride solution (100 ppm) were floated in chitosan solution0%, 5/0% and 1% and packaged under three different concentrations of oxygen ( 5,10 and 0%) and the samples were kept at different temperatures for 45 days. In sensory evaluation, 5-point hydraulic scale method was used and sensory properties including texture, taste, flavor, aroma, product freshness and overall product acceptance were examined (Sedaghat et al., 2010).
Results and discussion: The results showed that chitosan polysaccharide concentration had no significant effect on changes in weight and tissue firmness of green bell peppers. However, increasing this concentration caused an increase in vitamin C conservation in bell peppers samples. In addition, it was revealed that increasing the concentration of this covering substance up to 0.5% causes an increase in L* component. By increasing oxygen gas concentration in packaging environment, there was a decreasing trend in tissue firmness and vitamin C content of samples. The results from variance analysis also showed that changes in oxygen gas concentration had no significant effect on changes in the samples’ weights as well as on brightness (L* components) of their colors. By increasing the concentration of oxygen in the packaging in the a* values had a decreasing trend and the effect of Polysaccharide chitosan was insignificant (P<0.05). By increasing the concentration of oxygen in the packaging the b* component was increased and made the b*reduced by increasing concentrations of chitosan coating. The reception of the samples in terms of tissue, aroma, freshness and taste was lower under the conditions with higher oxygen which was also true about the general reception. And the concentration of Polysaccharide chitosan had the lowest effect on the organoleptic changes of the packaged product under various conditions. Based on the results polysaccharide chitosan had a significant impact on the taste of the final product.
Conclusion: Based on the results the optimal concentration of chitosan coating, the concentration of oxygen, temperature and time are 6/0%, 12%, 8/21-to- 11 ° C, respectively.