Upcycling lemon by-products for the development of natural food ingredients and additives for food applications

Over the past decade, the world’s population has grown rapidly, driving the expansion of the food processing industry to meet the growing demand for a variety of food products. Concurrently, food processing generates a significant amount of food by-products. Predictably, these by-products are disposed of as food waste, leading to detrimental environmental and economic impacts. Lemon peel, a primary by-product of lemon processing, represents a significant proportion of this waste. Nevertheless, lemon by-products contain valuable substances with remarkable nutritional and bioactive properties, holding promise for food applications. These by-products are rich in nutrients, especially minerals, vitamin C, pectin, and other dietary fibers, and phytochemical compounds with desirable properties, mainly phenolic compounds and essential oils. In addition, lemon by-products have been shown to have great bioactive properties, including antioxidant and antimicrobial activities. Lemon by-products show great potential for applications in the food industry, including (1) food ingredients/additives offering both nutritional value and extended shelf-life; and (2) film matrices or active constituents for edible food coatings, especially for their antioxidant and antimicrobial properties. This chapter provides a comprehensive summary of the recovery and valorisation of the main functional ingredients and additives from lemon by-products, their nutritional and phytochemical profile, bioactive properties and potential applications in the food industry.