# Phytochemical and Functional Properties of Fruit and Vegetable Processing By-Products
## 3 Results
### Valorization Approaches for Fruit and Vegetable By-Products  
Fruit and vegetable by-products can be an excellent source of health-promoting bioactive compounds, including proteins, fibers, sugars, minerals, vitamins, essential oils, polyphenols, phenolic acids, flavonoids, pigments, etc., which can be recovered, valorized, and commercialized from a circular and sustainable perspective. The recoverable fractions of these residues represent a huge amount of waste generated during the pro  
Figure 2: Raw FT-MIR spectra ((**A**) apple peel; (**B**) apple pomace; (**C**) orange carrot peel; (**D**) orange carrot pomace; (**E**) black carrot peel; (**F**) cucumber peel; (**G**) kumquat peel and pomace; (**H**) parasip peel; (**I**) mango peel; (**J**) mango pomace; (**K**) peach peel; (**L**) peach pomace; (**M**) black plum peel; (**N**) black plum pomace). cessing stages, and they can vary between 20% and 33% for peels, and 15% and 32% for pomaces, of the initial weight of the fruit or vegetable (data measured from the samples of this study). However, it is important to correctly characterize these wastes from a chemical point of view to identify the best use for their valorization. At the same time, the procedures and technologies for the extraction of these molecules can affect the sustainability of the processes. Traditional extraction methods can be expensive and time-, energy-, and harmful-solvent-consuming. Moreover, bioactive compounds are sensitive to high temperatures and prolonged extraction times. On the contrary, greener and non-conventional methods, such as supercritical fluid extraction, pressurized liquid extraction, microwave-assisted extraction, ultrasound-assisted extraction, pulse electric field extraction, and enzyme-assisted extraction, can be eco- and user-friendly, use few or no solvents, and have short extraction times [47; 52]. Most of the by-products considered in this study can be reintegrated in food and beverage industries or as animal feed to enhance their technological, sensorial, and nutritional properties. For example, apple, carrot, mango, and citrus pomaces and peels or their extracts can be used as ingredients for bakery products (bread, cakes, muffins, biscuits), dairy products (yogurt and ice-cream), meat products (patties and nuggets of chicken, buffalo, mutton); the apple pomace can be used in jams or extruded snacks and beverages; the carrot pomace and mango peel can be used in pasta; the citrus wastes and mango peel can be used in jellies, jams, and probiotic drinks [57; 69; 70; 71]. The introduction of these by-products could be due to the high soluble and insoluble fiber contents (in particular, cellulose, hemicellulose, lignin, pectin, etc. ), which increase the technological properties of products due to their effects on binding flavor components, swelling capacity, water holding capacity, fermentability, gel formation, and increasing viscosity [72]. Dietary fibers, in particular, the soluble fractions, also have positive effects on human health, with benefits for the gastrointestinal system, lipid and glucose metabolism, and reducing the levels of serum triglycerides and hepatic cholesterol [73; 74; 75]. The functional properties of dietary fibers (water permeability, gelling, and network formation) combined with the biological antimicrobial and antioxidative activity of phenols make possible the use of these by-products in the development of food packaging, including edible films [57; 61; 74]. In fact, their incorporation can reduce food oxidation and, therefore, food spoilage, extending food shelf life through protection against biological, physical, and chemical deterioration [57; 75]. Fruit and vegetable by-products also provide a wide range of natural phenols and pigments such as chlorophylls, carotenoids, anthocyanins, betanin, etc.