The physicochemical properties of starches isolated from defatted tigernut meals: Effect of extrusion pretreatment

If the tigernut meal left after oil extraction is used as a material for starch resources instead of being wasted, the industrial value of tigernut would be improved. Thus, we investigated the effect of extrusion before oil extraction on the yield, structure and function of starches within tigernut meals (TMS). Compared with the yield of native starch, the yield of TMS-130-11 (barrel temperature: 130 °C; feed moisture: 11 %) was increased by 1.97 %, and that of TMS-140-11 (barrel temperature: 140 °C; feed moisture: 11 %) was decreased by 7.82 %. The starches cannot be obtained when the barrel temperature is above 140 °C with 11 % feed moisture. Extrusion slightly decreased the relative crystallinity and increased the ratio of B2-chains in amylopectin. These changes resulted in reductions in peak viscosity while improving the elastic properties of the starch gel. These results will provide useful information regarding the use of starch isolated from tigernut meal.