Millet processing by-products: sustainable applications in food and non-food sectors

Typically, millet undergoes a series of processing treatments before being consumed and intended for the development of value-added products. Millet by-products such as husks/hulls/seed coats, bran, and broken grain account for up to 35% of the total weight of millets. Millet byproducts are mainly used as animal feed and are rarely used in product development. However, these millet by-products contain valuable bioactive compounds, polyphenols, flavonoids, xylo-oligosaccharides, bioactive peptides, micronutrients, fiber, and antioxidants. Additionally, the nutritional composition of different millet by-products varies due to differences in milling levels, millet varieties, and weather conditions. These millet by-products can be used in various ways in the food and non-food sectors. Millet husks and bran are used to develop gluten-free baked goods-breads, designer buns, and muffins. Millet by-products can be used in the design of functional foods, dietary supplements, or drugs. In addition, millet byproducts can be used to extract bioactive compounds such as water-soluble xylan, polyphenols, antioxidants, fiber, and essential oils. Peptides made from millet by-products can be employed as an ingredient in food fortification. Millet by-products are used as a source of biofuel production, cementing materials, thermoplastic composites, and in the field of nanotechnology. Despite the many benefits associated with millet by-products, they are still considered waste and an environmental hazard. This review, along the same lines, includes all possible, effective, and economical ways to valorize millet by-products.