Effects of various oil extraction methods on the gelatinization and retrogradation properties of starches isolated from tigernut (Cyperus esculentus) tuber meals.

Gelatinization and retrogradation characteristics of starches from tigernut (Cyperus esculentus) tuber before and after various oil extraction processes were studied in this investigation. The results indicated that starches isolated from tigernut tuber after the various oil extraction processes varied significantly in gelatinization and retrogradation properties. The starches isolated from the cakes of tigernut tuber after hot press extraction exhibited higher retrogradation tendency and relatively less shear-thinning than other starch samples. The results of FT-IR, XRD, and NMR analysis indicated that oil extraction had an unfavorable influence on starch retrogradation, which may be due to structural changes caused by oil extraction processes. In particular, oil extraction led to more efficient packing of double helices in the crystalline lamella of the starches during storage. Retrogradation of the starch gels also reduced the water holding capacities of the starches. The starch sample isolated from the cake after cold press extraction exhibited the highest water absorption capacity among the five samples for all storage times. This investigation provides valuable novel information for the industrial utilization of tigernut tuber starches isolated from meals and cakes after oil extraction.