Table 1.

Ripening agents and their features.

Ripening Agent	Features
Ethylene	Treatment is accomplished either at the packing house or at the distribution place [32]. Climacteric fruits become ripened successfully with less than 1 ppm ethylene gas by volume with an exposure of 12 h or more [28,33]. The time as well as the required concentration for ripening may vary from 0.1 to 1 ppm depending on the commodity [34].
Ethanol [31]	Exogenously applied to inhibit ethylene biosynthesis for ripening purposes. A 35–50% ethanol treatment is effective against microbial and fungal attack, improves sensorial quality, and prevents table grape decay.
Ethylene Glycol [25]	Cheaper than ethylene gas. Usable by dilution with water. Addition of water may fasten the ripening process of various fruits in colder climactic conditions. Alkyl alcohol consisting of 6 and 14 carbon atoms can artificially ripe bananas. Lauryl alcohol can develop to a completely yellow color without affecting palatability within 48 h during treatment with 0.01% by weight of bananas.
Calcium Carbide [34,35]	Often used traditionally in granular or powder form. The high cost and scarcity of ethylene availability, faster ripening capability due to break down of glucose. and being comparatively cheaper than other chemicals are the root causes behind its vast usage. Sometimes, industrial grade calcium carbide shows impurities, such as Ca3P2, CaS, Ca3N2, SiC2, AsS3, and PH3. Acetylene is produced from the reaction of calcium carbide with moisture initiates ripening in mangoes at 1 mL/L and in bananas at 2.8 mL/L or 1 mL/L.
Ethephon [25]	Above pH 5, it decomposes into ethylene gas, bi-phosphate ion, and chloride ion. Provides better color profile than naturally ripened fruits and also improves the peel color of mangoes. Increases skin color, skin carotinoids, total suspended sloid, vitamin C, and fruit juice. Fruits treated with ethephon possess longer shelf life than fruits treated with calcium carbide, and it causes faster ripening. Some studies showed that pineapples, bananas, and tomatoes treated with 1000 ppm ethephon took less time for ripening than with other reagents.
Methyl Jasmonate [31]	Improves firmness, increases resistance to mechanical damage, and reduces microbial attack and post-harvest decay. Resists postharvest diseases, increases polyamine content, and elongates shelf life. Application of 0.1–10 mM jasmonate causes chlorophyll degradation, enhances carotene accumulation, and, thus, changes the color of apples and mangoes. A combined treatment of 0.1 mM methyl jasmonate and ethanol on strawberry shows higher antioxidant capacity, total phenolics, and anthocyanins than treatment with ethanol only.