Nutrition, phytochemical profile, bioactivities and applications in food industry of pitaya (Hylocereus spp.) peels: A comprehensive review

In the last decade, the sharply increasing population has fueled the development of food industry to fulfill the demand of daily consumption. The processing of food products inevitably brings about some by-products, which tend to weigh the burden of environment. Pitaya (Hylocereus spp.) is consumed in most regions of the world due to good taste and health-promoting effects. Peels, accounting for approximately one third of whole fruits, are the main by-products generated by pitaya processing. However, pitaya peels promise to be recycled as great reservoirs of nutritional and bioactive compounds. This review summarizes the nutritional and phytochemical profiles of pitaya (Hylocereus spp.) peels in detail. Further, the bioactive activities of pitaya peels based on the findings of in vitro and in vivo studies are deeply reviewed. Besides, the research progress with regard to the reutilization of pitaya peels by food industry is comprehensively discussed. Pitaya peels are a rich source of nutrition, especially pectin and dietary fiber, and bioactive phytochemicals such as betacyanins. Recent literatures have demonstrated the potent health-promoting effects of pitaya peels or their extracts, suggesting the application in the development of innovative food products. Moreover, pitaya peels demonstrate great potentials to be applied in food industry, including: 1) applications in food products; 2) applications in recovery of high added-value materials (amylase, pectinase, pectin and betacyanins); 3) applications in food packaging and edible coatings. The reutilization of pitaya peels would assist in increasing overall added value and alleviating the environmental burden.