Suitability of Aloe vera and gum tragacanth as edible coatings for extending the shelf life of button mushroom.

Authors Mohebbi, M., Ansarifar, E., Hasanpour, N., & Amiryousefi, M. R.

Button mushroom have a short postharvest shelf life compared to most vegetables, due to a very high metabolic activity and high-water content. This makes them prone to microbial spoilage and to exhibit enzymatic browning. During cold storage, the uncoated mushrooms showed rapid weight loss, color changes, and accelerated softening white mushroom s treated with aloe vera gel, gum tragacanth, and the combination of both significantly delayed these phenomena. Among different coatings, the combination of aloe vera and gum tragacanth was more effective. The button mushroom (Agaricus bisporus) is the most widely grown and consumed mushroom in the world, and it includes about 40% of the total world production of mushroom (Giri and Prasad 2005). Mushrooms are the excellent source of some essential amino acids, vitamins (B2, niacin, and folates), and minerals (potassium, phosphorus, zinc, and copper) (Tao et al. 2006). Moreover, mushrooms contain various polyphenolics and flavonoids which are recognized as excellent antioxidants (Singla et al.2010). On the other hand, button mushrooms have a short postharvest shelf life of less than 3 days at ambient temperature (Kim et al. 2006). So, mushrooms require special attention to preserve their freshness. There are various methods to extend the shelf life of mushrooms including modified atmosphere packaging, controlled atmosphere storage , vacuum cooling technology (McDonald and Sun2000), coating, and refrigeration. Among these, coating is the most likely method of vegetable and fruit preservation. Edible coatings are customarily used for better food appearance and protection. They could help to decrease moisture loss and slow respiration by reducing oxygen uptake from the environment. Modification of fruits tissue metabolism by affecting respiration rate, extension of storage life, firmness retention, transportation of antimicrobials, antioxidants, and other preservatives and microbial growth control are the main functional advantages attributed to the use of edible films and coatings. In addition to prolonging shelf life and delaying senescence, coatings add sheen and luster to products and make them more attractive and appealing to consumers. Fruits or vegetables are usually coated by dipping in or spraying with a range of edible materials. Therefor e, a semipermeable membrane is formed on the surface for suppressing respiration, controlling moisture loss, and providing other functions. he gel works as a barrier to O2and CO2and acts as moisture barrier , and thus reduces weight loss, browning, softening, and growth of yeast and molds. The material contains antimicrobial compounds and thus prevents decay. Aloe vera contains malic acid-acetylated carbohydrates (including?-1, 4-g1ucomannans) with anti-inflammatory activity. The sensory examinations of sweet cherry coated with aloe vera gel showed useful effects in terms of delaying stem browning and dehydration and maintenance of fruit visual characteristic without any damaging effect on taste, aroma, or flavors. Gum tragacanth (GT) is a dried exudate which is obtained from slashing the stems of Asiatic species of Astragalus (Leguminosae). GT includes water soluble (30–40% of GT) and non-water-soluble (60–70% of GT) fractions, which are called tragacanthin and bassorin. Gum tragacanth is widely used as a natural emulsifier and thickener in the food, drug, and allied industries. Its wide use is due to its stability in a wide range of temperature and pH and its effectiveness as an emulsifying agent with extremely long shelf life. As GT is a natural polymer, it is nontoxic and biocompatible. Development of natural preservative coatings to reduce respiration rate and inhibit enzymatic browning with antimicrobial agents is expanding due to the riskiness aspects of chemical preservatives. The main procedures which lead to loss in quality after harvest are (a) discoloration, (b) browning, (c) loss of closeness, (d) weight loss, and (e) texture changes. The color and the shape of the cap are the main parts of fresh mushrooms because these are the first characteristics which attract consumers. This study aimed to assess the suitability of aloe vera, gum tragacanth, and combination of both as edible coatings for mushrooms and to determine the influence of the coating on the mushroom’s physicochemical changes during storage.