Tiger nut and its by-products valorization: From extraction of oil and valuable compounds to development of new healthy products

Consumer's growing demand for consumption of Horchata de chufa, a Spanish beverage produced from tiger nut tubers, has led to large-scale production of tiger nuts, and its subsequent processing for the food industry. Recent investigations clearly show that tiger nut is a valuable source of stable vegetable oils, rich in mono-unsaturated fatty acids, and phytosterols as well as high-added value compounds (proteins, carbohydrates, vitamins, minerals and bioactive compounds). Several conventional (Soxhlet) and alternative innovative (SC-CO2, enzyme, high pressure, etc.) extraction methods have been developed for the efficient recovery of tiger nut oil and high-added value compounds. Moreover, several authors have shown the potential of tiger nuts by-products in the development of new healthier and functional products such as fiber rich and oxidative stable foods. The present review provides an overview of these investigations and tries to expose potential avenues for future research in commercial exploitation of tiger nuts and its by-products. Industrial relevance: Tiger nuts and their by-products obtained from horchata de chufa manufacturing process have a remarkable content of nutrients, fiber and bioactive compounds (eg. polyphenols). Moreover, they have a high amount of oil, rich in mono-unsaturated fatty acids, tocopherols, and phytosterols, thus being a valuable source to be incorporated into different food matrices in order to modify their technological and functional properties. At this stage of development, tiger nuts by-products are underutilized at an industrial level. For example, the literature about the oil extraction from tiger nuts by-products is scarce and most of the studies have been focused on the use of conventional (Soxhlet) extraction of oil. This review provides an overview of some of the most relevant innovative processing technologies to allow the industrial sustainability and green recovery of oil from tiger nuts and their by-products and, tries to expose potential avenues for future research in commercial exploitation of tiger nuts and its by-products as source of ingredients to be incorporated in new food matrices to improve their technological and functional aspects.