The fruit and vegetable industry generates large volumes of solid waste. Organic materials are the main solid wastes, including discarded fruits and vegetables. Now a day, many industries simply dispose off the byproducts produced during the production processes, this is neither good for the environment, nor is it a sustainable behavior if we are to preserve the earth for the future generations.
Why Waste the Waste
1. Dr. Shahzad Hussain, Assistant Professor, Department of Food Science and Nutrition, King Saud University, Riyadh, Saudu Arabia.
Email: [email protected]
2. Mr. Muhammad Nadeem, Ph. D Scholar, National Institute of Food Science and Technology, University of Agriculture, Faisalabad, Pakistan
The fruit and vegetable industry generates large volumes of solid waste. Organic materials are the main solid wastes, including discarded fruits and vegetables. Now a day, many industries simply dispose off the byproducts produced during the production processes, this is neither good for the environment, nor is it a sustainable behavior if we are to preserve the earth for the future generations. Serious environmental problems causes by solid agri-food waste materials, such as water pollution, unpleasant odors, explosions and combustion, asphyxiation, vegetation damage and greenhouse gas emissions. Consequently, now the main emphasis is on the recovery, recycling and upgrading of agricultural wastes as a low cost source of antioxidants. A lot of research on the reuse of agricultural wastes has been aimed at conversion of the waste materials into food ingredients, bio-fuels, and other value-added applications. Some agricultural wastes e.g. grape seed and olive waste extracts are isolated from vegetable and their products. A reasonable absorption of natural antioxidants could protect oxidative damage in cells. Many diseases such as autoimmune diseases, inflammation, cardiovascular-neurological diseases, cancer and aging are caused by this oxidative stress. The term antioxidant refers to compounds which can scavenge free radical, inhibit lipid per-oxidation and to chelating agent. This definition is overcome by Phenolic compounds as they possess a wide spectrum of biological effects such as antioxidant and free radical scavenging. Favorable raw materials are solid wastes, produced from the processing of fruits and vegetables, for obtaining extracts rich in phenolic compounds with good antioxidant properties because of their low cost and the possibility of reducing environmental problems caused by waste disposal. In addition, the external parts of vegetables (such as skins, peels, hulls, or seeds) are generally disposed, although phenolic compounds are found in large amounts in them potentially useful as antioxidants, than have their corresponding inner fractions.
Fruit juices and derived products such as nectars and drinks have experienced growing popularity within the last years. From tropical and subtropical fruit processing higher ratios of by-products are produced. Due to the large amounts being processed into juice, a considerable by-product industry has evolved to utilize the residual peels, membranes, seeds, and other compounds from citrus fruits. Dried pulp and molasses, fiber-pectin, cold-pressed oils, essences, d-limonene, juice pulps and pulp wash, ethanol, seed oil, pectin, limonoids and flavonoids are produced from residues of citrus juice. High antioxidant activity is present in citrus seeds and peels. Both in vitro and in vivo studies have recently demonstrated health protecting effects of certain citrus flavonoids. Peels and stones are major waste of mango processing, amounting to 35-60% of the total fruit weight. Mango seed kernel fat is the source of edible oil and has attracted attention since its fatty acid and triglyceride profile is similar to that of cocoa butter. The principle antioxidants were characterized as phenolic compounds and phospholipids. The phenolics were assumed to be mainly gallic and ellagic acids, and gallates. Dietary fiber obtained from Mango peels were reported to be a good source of high amounts of extractable polyphenolics. The most reasonable way of utilizing apple pomace is the production of pectin both from an economical and from an ecological point of view. Apple pomace has been shown to be a good source of polyphenols which are predominantly localized in the peels and are extracted into the juice to a minor extent. In wine making about 80% of the total grapes produced are used and pomace represents approximately 20% of the weight of grapes processed. Many products such as ethanol, tartrates, citric acid, grape seed oil, hydrocolloids and dietary fiber are recovered from grape pomace. The principal phenolic constituents of grape pomace are anthocyanins, catechins, flavonol glycosides, phenolic acids, alcohols and stilbenes. The antioxidant activity of grape pomace has led to the development of a new concept of antioxidant dietary fiber.
Attempts are made for the biotechnological production of protein, ethanol, a-amylase, hemicellulases, and cellulases from banana waste. Guava seeds contain about 5-13% oil rich in essential fatty acids, usually discarded during processing of juice and pulp. Peel and pulp of guava is source of antioxidant dietary fiber. Papain that is recovered from the latex of papaya fruit, is a proteolytic enzyme used as a meat tenderizer and as a stabilizing agent in the brewing industry. Furthermore papaya fruits can also be used for the production of pectin. Some wastes are also produced from vegetable processing into juices. During tomato juice pressing about 3-7% of the raw material is lost as waste material. Tomato pomace consists of the dried and crushed skins and seeds of the fruit. The seeds are a source of protein (35%) and fat (25%) and account for approximately 10% of the fruit and 60% of the total waste, respectively. Skin extracts are especially rich in lycopene. Despite considerable improvements in processing techniques including the use of depolymerizing enzymes, mash heating and decanter technology, a major part of valuable compounds such as carotenes, uronic acids and neutral sugars are still retained in the carrot pomace which is usually disposed. The major byproducts resulting from industrial peeling of onion bulbs are brown skin, the outer two fleshy leaves and the top and bottom bulbs. They are a source of flavor components and fiber compounds and particularly rich in quartering glycosides. Tomato seed oil, which is rich in unsaturated fatty acids, especially in linoleic acid has attracted interest.
The use of by-products of fruit and vegetable processing industry as basis of functional compounds and their function in food shows potential which requires interdisciplinary research of food technologists, food chemists, nutritionists and toxicologists. Food processing technology should be optimized in order to minimize the amounts of waste production. On a large scale and at affordable levels, methods for complete utilization of by-products resulting from food processing should be developed. Active participation of the food and allied industries with respect to sustainable production and waste management is required. Plant breeding may also be used in minimization of potentially hazardous constituents, e.g. solanin, amygdalin, and optimization of valuable compounds such as carotenoids and betalains. The bioactivity, bioavailability and toxicology of phytochemicals need to be carefully assessed by in vitro and in vivo studies. Furthermore, investigations on stability and interactions of phytochemicals with other food ingredients during processing and storage need to be initiated. In any case, consumer protection must have priority over economic interests and health claims need to be substantiated by standardized, scientifically sound and reliable studies.