Tiger nut (Cyperus esculentus) starch: extraction, composition, structure, properties, modification and uses

Although tiger nut, the tuber of Cyperus esculentus L., is regarded as a new source of edible oil, it also constitutes up to 14-37% of starch on a dry basis. Since it is globally popular and widely cultivated in Africa, Asia, Europe and America, tiger nut is a promising and underutilized source of commercially available starch. To date, there is a lack of systematic understanding of tiger nut starch. Herein, we mainly focus on tiger nut starch, including its extraction, chemical composition, structure, properties, modification and application aspects. The chemical composition of tiger nut starch is proven to be markedly affected by its extraction method. The amylose content of tiger nut starch is reported to vary from 9.71% to 27.01%. Tiger nut starch is mostly spherical and oval, and its granule size ranges from 2 to 18.53 mu m with an A-type crystallinity. Compared with common starch (such as wheat, corn, potato, and cassava starch), tiger nut starch shows unique differences in fine molecular structures, swelling power, solubility, thermal properties, pasting properties and in vitro digestibility. In order to improve its properties and potentially widen its uses, tiger nut starch has been modified by physical, chemical, enzymatic and dual methods. Besides, tiger nut starch has great potential for food and non-food uses. This review is worthy for the further development of tiger nut as a sustainable crop as well as for the value-added utilization of tiger nut starch.