Abstract
Food colorants processed via agro-industrial wastes are in demand as food waste management becomes vital not only for its health benefits but also for cost reduction through waste valorization. Huge efforts have been made to recover valuable components from food wastes and applied in various fields to prove their versatility rather than for feed ruminant usage only. Betalains and phenolics, antioxidant-rich compounds responsible for host color and so commonly used as natural colorants in food and cosmetic industries, are copiously present in several kinds of fruits and vegetables as well as their wastes. Technological innovation has brought extensive convenient ways of bioactive compounds extraction with many advantages like less use of solvents and energy in a short period of processing time in comparison with the classical solid–liquid extraction methods. Emerging technologies, particularly microwave irradiation, have been amenable to electromagnetic technology for decades. Practically, they have been deployed for functional and supplement food production. In this review, the feasibility of dielectric heating (microwave irradiation) in the extraction of betalain and phenolic compounds mostly from fruit and vegetable wastes was discussed.
Highlights
Global interest for natural food colors is on the rise, especially in Asian countries
Their exhibition of antioxidant activity is mainly based on their functional structure, for example, betalamic acid possesses conjugated double bonds that serve as reducing agents via electrons sharing [4]
Biosynthesis reaction of compounds present in the matrix can be by ascorbic acid, which interferes with oxidative activity of polyphenol oxidases or ß-gluconolactone handled by acidifying the extraction medium; for example, enzymatic decolorization of betalain can and inhibits ß-glucosidase [33]
Summary
Global interest for natural food colors is on the rise, especially in Asian countries. Over 10,000 phenolic compounds exist in several kinds of fruits and vegetables, cereals, tea leaves, coffee beans, and their accumulation in the whole parts of the plant including root, stem, bark, flower, and leaf have been noticed [17]. Their extraction from various sources has been boosted by emerging technologies these days, microwave radiation. The aim of this review was to point out the versatility of microwave irradiation in the recovery of bioactive compounds focusing on phenolics and betalains from various kinds of fruits and vegetables for their improved practical application in food and beverages, pharmaceuticals, cosmetics, and other related sectors
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