Taste and appearance have a high impact on the commercial value of food products. Increasing the shelf life of food items gives financial benefits. Artificial ripening and sweetening are used to increase food palatability. Similarly, artificial colorants are applied to improve the appearance of food. Preservatives are added to store food in a fresh condition for a long time. The following sections briefly describe different means of adulteration to improve physical and sensory properties.
To avoid the economic loss incurred by the spoilage of climacteric fruits during the harvest, processing, and transportation process, the fruit sellers pluck the fruits much before they attain proper maturity and use chemicals to ripen them artificially just before retailing. The necessity for artificial ripening also arises if the fruit sellers wish to sell fruits before their due season to make additional profit. Ethylene, ethanol, methanol, propylene, methyl jasmonate, ethylene glycol, ethephon, and calcium carbide are used to ripen fruits and vegetables artificially.
Sweetness of food is an important criterion in terms of demand and marketability. So, there is always a tendency by the traders to increase the sweetness of selected food items by artificial means. Mainly, fruits and vegetables, beverages, sweeteners, and confectionary products fall into sweet food category.
Artificial sweeteners are injected by injector pumps on one side of fruit to alter the natural sweetness. To ensure uniform distribution, sellers inject sweeteners from several points in the fruit. Saccharine mixture was found to be injected into melons and watermelons to enhance sweetness artificially. The addition of external sugar or sugar solution is a common form of adulteration of fruit juice. In the case of export purpose, the concentrated fruit juice is shipped; later, external water and sugar are added to the concentrated fruit juice to give natural properties similar to that of natural juice. In addition, high-fructose corn syrup, partially hydrolyzed cane syrup, and beet medium invert sugar are also added to increase the Brix value and to improve composition quite similar to authentic juice. The direct addition of sucrose, glucose, fructose, maltose, beet sugar, corn sugar, and cane sugar in honey is widely practiced. Adulteration of honey and confectionary products with fructose or glucose changes the fructose-to-glucose ratio. Feeding honeybees with syrups and industrial sugars after the broods have been naturally available is known as an indirect form of adulteration which is very difficult to detect. Feeding low quality honey to honeybees is also reported. Different confectionary and bakery products are sweetened with Acesulfame-K and Aspartame. Sugar, coloring agents, synthetic red dyes, aromatizing agents, and sweeter foreign wines are often added into wine for quality enhancement purpose. Glycerol reduces the acidity and bitter taste, increases the sweetness, and stops fermentation, while diethylene glycol imparts relish to wines. The addition of root or cane sugar to tequila and the addition of cane or beet ethanol to whiskey have also been noted.
Color, texture, and appearance of food products are important criteria in the selection of desired food items by consumers. Foods with attractive color increase marketability and profit. Thus, following this trend, various natural as well as synthetic dyes are applied to different food items. Most of the colorful food items are at risk of such malpractice. Among those, fruits and vegetables, egg and egg-derived food, spices, sweeteners, and confectionary products are prime choices. Coloring agents are also added in processed meat and fish. Paprika oleoresin is commonly used as a natural coloring agent in meat-based food products.
Natural colors, such as chlorophyll, annatto, and caramel, have been reported several times in fruits and vegetables. Synthetic dyes are more popular among the sellers, as those exceed natural ones in many aspects. These are chemically synthesized, more stable, shiny, and highly efficient. Their cheapness and easy availability are also considerable factors. Rhodamine B, auramine, Metanil yellow, Congo red, Orange II, malachite green, and other permitted and non-permitted colors are used in cut fruits and vegetables. Red dye is injected into watermelons to enhance the acceptability of the consumers. Malachite green is widely used to make green vegetables, such as green chili, green peas, bitter gourds, lady finger, and pointed gourdd, look greener, fresh, bright, and glowing. Another reagent frequently reported for bitter gourd and lady finger to be dipped into is copper sulfate solution, which is bright blue in hydrous form and pale green in anhydrous form. Mobile oil for coloring and carbofuran for a fresh purple appearance are injected into brinjals, tomatoes, cauliflowers, and cabbages. Phosphomidone, methyl parathion, monocrotophos, and formaldehyde are also injected for a fresh white appearance.
Eggs are dyed artificially by azo dyes. The addition of illegal synthetic dyes is inspiring among the traders, as eggs’ nutritional value and freshness are predicted by judging the egg yolk color. Sudan dyes are a type of synthetic azo dye that is used in industry or printing. Another azo dye, Para red, is chemically similar to Sudan dye I and is used for printing purposes. The yellow-orange-hue-colored eggs are preferable by consumers. So, the sellers often feed hens food mixed with dyes to enhance the color of egg yolk.
Sudan I, Sudan Ⅳ, Metanil Yellow, Sudan III, Oil Orange SS, Rhodamine B, Auramine O, coal tar red, Para Red, etc., are applied in red pepper chili powder. Sudan I, Sudan Ⅳ, Acid Black I, Annatto, etc., are mixed with paprika powder. Sudan I, Metanil Yellow, Lead Chromate, etc., are added with turmeric powder. Amaranth Red and Basic Red 46 are added into sumac. Auramine O and Chrysoidin are mixed with curry powder. Acid Orange II, Metanil Yellow, Ponceau 4R, Gardenia Yellow, dye extracted from the flowers of Buddleja officinalis Maxim, etc., are added with saffron flower. Crystal Violet is mixed into cayenne pepper. In addition to synthetic dyes, colored paper and wood are also used.
Dark honey or “forest honey” is richer in minerals and nutritional value than light honey and possesses a higher commercial value. That is why light honey is often tainted with sulfite ammonia caramel and presented as dark honey.
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