Incorporation of Dragon Fruit Peel and Lemon Zest in Fruit Spread: A Critical Review of Bioactive Composition, Extraction Technologies, Processing Stability, and Functional Food Applications

Abstract

The growing production of food processing waste brings an environmental challenge and a need for sustainable food innovation. Fruit peels, which are thrown away as agro–industrial waste, are full of bioactive substances that have useful bioactive compounds. This article explores the use of dragon fruit ( Selenicereus spp., formerly Hylocereus spp. ) peel and lemon (Citrus limon) zest in fruit–based spreads to enhance nutritional, functional, and sensory properties. The peel of the dragon fruit, generally regarded as waste, contains a high amount of betalains (betacyanins: 32–80 mg/100 g fresh weight; betaxanthins: 12–40 mg/100 g fresh weight), dietary fibre (up to 46.5%), pectin (yield: 9.4–20.5% by ultrasound– and microwave-assisted extraction, respectively) and phenolic compounds (total phenolics: 2.8–8.9 mg GAE/g dry weight). Similarly, lemon zest is a rich source of fiavonoids (primarily hesperidin and eriocitrin), and D–limonene (59–74% of essential oil) responsible for flavour enhancement and preservation. The combined use of these by–products in fruit spread improves antioxidant potential, fibre content, texture, and sensory characteristics. Therefore, the use of dragon fruit peel and lemon zest added to fruit–based spreads can be considered an effective approach to the green economy, converting agro–industrial waste into value–added functional foods.