Effects of different isolation methods on the structure and functional properties of starch from tiger nut (Cyperus esculentus L.) meal

Tiger nut (Cyperus esculentus L.) tuber meal as the major by-product of tiger nut oil production is a promising starch source. Starches obtained from tiger nut meal using different isolation methods were compared: distilled water (DWS), citric acid (CAS), enzyme (ESS), 0.5 g/L NaOH (LNS-0.5), 2 g/L NaOH (MNS-2), and 5 g/L NaOH (HNS-5). The highest yield (36.2% of tiger nut meal) was observed in HNS-5. Moreover, HNS-5 demonstrated the smallest particle size (7.69 μm), the highest amylose ratio (13.7%), and strongest freeze-thaw stability. ESS showed the highest relative crystallinity (20.0%), pasting temperature (79.1 °C), and its gel demonstrated higher hardness and adhesiveness compared to others. The average chain length of amylopectin (degrees of polymerization: 20.0−20.6), and the proportion of the amorphous phase (7.67%–8.66%) in starches were slightly affected by different isolation methods. Nevertheless, the crystalline pattern (C-type) of all starches was not changed, and all starch gels exhibited a similar single rate constant (0.037 min−1) during the simulated digestion process. Therefore, different isolation methods could be used to achieve different processing objectives, such as high yield or obtaining starch with enhanced properties.