Nanotechnology is a rapidly growing field with profound applications in different domains, particularly in food science and technology. Nanoparticles (NPs) synthesis, an integral part of nanotechnology-based applications, is broadly classified into chemical, physical and biosynthesis methods. Chemically sensitive and energy-intensive procedures employed for NPs synthesis are some of the limits of traditional chemical approaches. Recent research has focused on developing easy, nontoxic, cost-effective, and environment-friendly NPs synthesis during the last decade. Biosynthesis approaches have been developed to achieve this goal as it is a viable alternative to existing chemical techniques for the synthesis of metallic nanomaterials. Fruit peels contain abundant bioactive compounds including phenols, flavonoids, tannins, triterpenoids, steroids, glycosides, carotenoids, anthocyanins, ellagitannins, vitamin C, and essential oils with substantial health benefits, anti-bacterial and antioxidant properties, generally discarded as byproduct or waste by the fruit processing industry. NPs synthesized using bioactive compounds from fruit peel has futuristic applications for an unrealized market potential for nutraceutical and pharmaceutical delivery. Numerous studies have been conducted for the biosynthesis of metallic NPs such as silver (AgNPs), gold (AuNPs), zinc oxide, iron, copper, palladium and titanium using fruit peel extract, and their synthesis mechanism have been reported in the present review. Additionally, NPs synthesis methods and applications of fruit peel NPs have been discussed. Graphical Abstract

Most of the bioactive compounds are hydrophobic, ineffectively dissolvable, and unstable in harsh storage conditions. Such limitations decrease the stability and bioaccessibility of these compounds as principal challenges for their utilization in the food industries. Nanoencapsulation is one of the most favorable technologies that inhibit the degradation of bioactive compounds from the various phases of food processing, intestinal digestion, and absorption. It empowers the retention of bioactive compounds and their discharge in a well-ordered way, which improves the bio-distribution of bioactive compounds at the target site of the organ. Nanotechnology improves a few characteristics, such as solubility, stability (prevent interaction of encapsulated material with matrix), and bioavailability of bioactive compounds. This review summarized the different carriers for the conveyance of bioactive compounds and their preparation methods. The different nanocarriers for bioactive compounds are association colloids, nanoemulsions, nano-liposomes, solid-lipid nanoparticles, nanostructured lipid carriers, bio-polymeric nanoparticles, and nanofiber. The high and low-energy approaches, electrospinning, and electro-spraying technology are used to prepare nanocarriers. The potential application of nanotechnology has also been discussed in delivering bioactive compounds. Apart from this, the characterization of nanoparticles for human safety and the bioavailability of bioactive compounds after consumption has been discussed.

Dragon fruit (DF) or Pitaya (Hylocereus spp.) a member of Cactaceae family is gaining popularity in the market for consumption of fresh fruit due to its highly attractive fruit color with nutritional and immense bioactive potential that reduces blood sugar level, cholesterol, prevention of liver injuries, cancer, and so forth. In commercial market valorized products of DFs are available. The processing of edible and nonedible parts of DF is of immense significance to prepare nutritionally rich value‐added products and concurrently reducing the challenges occurring due to waste generation and spoilage. This review paper provides detailed insights of DF processing into different value‐added products, its medicinal benefits, bioactive potential, and the physico‐chemical changes occurring in DF during processing such as drying, fermentation, extraction, and so forth.