India is the second-largest producer of contemporary fruits and vegetables. This leads to generation of a large amount of waste, both solid and liquid. This waste is incautiously or carelessly being thrown without any treatment promoting environmental deterioration. The chapter deals with how these fruit wastes, especially pineapple and papaya peels, which are usually discarded during the processing or consumption of the fruit, are useful in preparation of vinegar, which is termed as a useful product from waste. It also discussed the general characteristics of Acetic acid bacteria, importance of the bacteria, and how it can be isolated by natural sources, which is cost effective. So, the waste peels generated after consuming the fruits and vegetables need not be discarded as waste; instead, it can be used in so many ways to produce useful products.
TopBackground
Vinegar was known as a seasoning or food preserving agent. Vinegar is defined as “a liquid fit for human consumption, produced from suitable raw material of agricultural origin, containing starch and sugars by the process of double fermentation, alcoholic and acetous, and contains specific amount of acetic acid. Vinegar is an important preservative and condiment and it is being produced since centuries. It is produced through the action of acetic acid bacteria on dilute solution of ethyl alcohol derived from yeast fermentation. Vinegar plays an important role in salad dressings, pickling of fruits and vegetables, ketchup, hot sauce and other sauces. To overcome the demand industrial fermentation systems should be capable of producing a large amount of vinegar. Many techniques have been developed to improve industrial production of vinegar. Today, the most common technology for the vinegar industry is based on the submerged culture with diverse technical modifications which try to improve the general fermentation conditions (aeration, stirring, heating, etc.,) (Tan, 2005). Pineapple (Ananas comosus) by-products are not exceptions. Indeed, several efforts have been made in order to utilize pineapple wastes, which have already been used as the substrate for the production of bromelain and organic acids (Dacera et al., 2009). Pineapple peels as agricultural wastes represent around 35% of the whole fruit mass. If these wastes are discharged to the environment untreated, they could cause a serious problem. So, it is necessary to have recycled waste raw material into useful product of higher value-added products or even as a raw material for other industries or feed after biological treatment. Papaya (Carica papaya) is an oblong tropical fruit, often seen in orange red, yellow green and yellow orange hues with a rich orange pulp. Papaya has high content of vitamin A, B and C, proteolytic enzymes like papain and chymopapain which have antiviral, antifungal and antibacterial properties.
Most nations, whether economically advanced or at different stages of development are faced with the issue of disposal and treatment of wastes (Itelima et al., 2013). Agro-industrial wastes are generated in large amounts every year and their reuse in processes is of particular interest due to their availability, low cost, and characteristics that allow at obtaining different value-added compounds (De Freitas Borghi et al., 2009). Tropical and subtropical fruits processing have considerably higher ratios of by-products than the temperate fruits (Schieber et al., 2001) [Figure 1].
TopGeneral Properties Of Vinegar
Vinegar is a dilute solution of acetic acid; it has same chemical formula as acetic acid. The table below showed general properties of vinegar [Table 1].
Table 1. General properties of Vinegar
| Parameter | Value |
| Density and phase | 1.01gcm-3, liquid; 1.266gcm-3, solid |
| Solubility in water | fully miscible |
| In toluene, hexane | fully miscible |
| In ethanol, acetone | fully miscible |
| Freezing point | -20C (28 O F) |
| Acidity (pKa) | 4.76 at 25oC |
| pH | 2.4 |
| Viscosity | 0.92 cp at 27oC |
| Dipole moment | Dipole moment |
| Refractive index | 1.370 |