Green banana fruit is an important starch resource that consists of flesh and peel. The physicochemical properties of flesh starch have been widely studied; however, those of peel starch have hardly been studied, leading to the waste of peel. In this study, the physicochemical properties of the starches from the flesh and peel of green banana fruit were investigated and compared. The dry flesh and peel had 69.5% and 22.6% starch content, respectively. The starch had oval and irregular granules with eccentric hila. Their starches had similar bimodal size distribution; the volume-weighted mean diameter was approximate 17 μm, and the peel starch had a slightly smaller granule size than the flesh starch. The maximum absorption wavelength was higher in peel starch than in flesh starch. The apparent amylose content of flesh and peel starch was 21.3% and 25.7%, respectively. The flesh and peel starches both exhibited B-type crystalline structures and had similar relative crystallinity, short-range ordered degrees, and lamellar structures. The swelling power was similar between flesh and peel starches, but the water solubility was higher in peel starch than in flesh starch at 95 °C. The peel starch had a higher gelatinization temperature than flesh starch, but their gelatinization temperature range and enthalpy were similar. Both flesh and peel starches showed a diphasic hydrolysis dynamic, but peel starch had higher resistance to porcine pancreatic α-amylase hydrolysis than flesh starch. The contents of rapidly digestible starch, slowly digestible starch, and the resistant starch of flesh and peel were 1.7%, 4.3%, 94.1% and 1.4%, 3.4%, 95.2%, respectively, for native starch, and 73.0%, 5.1%, 21.9%, and 72.3%, 4.5%, 23.2%, respectively, for gelatinized starch.

Different-colored sweet potatoes have different contents of pigments and phenolic compounds in their root tubers, which influence the isolation of starch. It is important to justify the identification of the most suitable isolation medium of starch from different colored root tubers. In this study, starches were isolated from root tubers of purple, yellow and white sweet potatoes using four different extraction media, including H₂O, 0.5% Na₂S₂O₅, 0.2% NaOH, and both 0.5% Na₂S₂O₅ and 0.2% NaOH. Their structural and functional properties were investigated and compared among different extraction media. The results showed that the granule size, apparent amylose content, lamellar peak intensity, thermal properties, and pasting properties were different among different-colored sweet potatoes due to their different genotype backgrounds. The four extraction media had no significant effects on starch structural properties, including apparent amylose content, crystalline structure, ordered degree, and lamellar peak intensity, except that the NaOH and Na₂S₂O₅ treatment were able to increase the whiteness of purple and yellow sweet potato starches. The different extraction media had some effects on starch functional properties, including thermal properties, swelling power, water solubility, and pasting properties. The above results indicated that the H₂O was the most suitable extraction medium to simply and fast isolate starch from root tubers of different-colored sweet potatoes.

The dry root tuber of Apios fortunei contained about 75% starch, indicating that it is an important starch resource. Starch displayed spherical, polygonal, and ellipsoidal granules with central hila. Granule sizes ranged from 3 to 30 μm with a 9.6 μm volume-weighted mean diameter. The starch had 35% apparent amylose content and exhibited C_A-type crystalline structure with 25.9% relative crystallinity. The short-range ordered degree in the granule external region was approximately 0.65, and the lamellar thickness was approximately 9.6 nm. The swelling power and water solubility began to increase from 70 °C and reached 28.7 g/g and 10.8% at 95 °C. Starch had typical bimodal thermal curve in water with gelatinization temperatures from 61.8 to 83.9 °C. The 7% (w/w) starch-water slurry had peak, hot, breakdown, final, and setback viscosities of 1689, 1420, 269, 2103, and 683 mPa s, respectively. Rapidly digestible starch, slowly digestible starch, and resistant starch were 6.04%, 10.96%, and 83.00% in native starch; 83.16%, 15.23%, and 1.61% in gelatinized starch; and 78.13%, 17.88%, and 3.99% in retrograded starch, respectively. The above physicochemical properties of A. fortunei starch were compared with those of maize A-type starch, potato B-type starch, and pea C-type starch. The hierarchical cluster analysis based on starch structural and functional property parameters showed that A. fortunei and pea starches had similar physicochemical properties and were more related to maize starch than potato starch.

Chestnut is a popular food in many countries and is also an important starch source. In previous studies, physicochemical properties of starches have been compared among different Chinese chestnut varieties growing under different conditions. In this study, nine Chinese chestnut varieties from the same farm were investigated for starch physicochemical properties to exclude the effects of growing conditions. The dry kernels had starch contents from 42.7 to 49.3%. Starches from different varieties had similar morphologies and exhibited round, oval, ellipsoidal, and polygonal shapes with a central hilum and smooth surface. Starch had bimodal size distribution and the volume-weighted mean diameter ranged from 7.2 to 8.2 μm among nine varieties. The starches had apparent amylose contents from 23.8 to 27.3% but exhibited the same C-type crystalline structure and similar relative crystallinity, ordered degree, and lamellar structure. The gelatinization onset, peak, and conclusion temperatures ranged from 60.4 to 63.9 °C, from 64.8 to 68.3 °C, and from 70.5 to 74.5 °C, respectively, among nine starches; and the peak, hot, breakdown, final, and setback viscosities ranged from 5524 to 6505 mPa s, from 3042 to 3616 mPa s, from 2205 to 2954 mPa s, from 4378 to 4942 mPa s, and from 1326 to 1788 mPa s, respectively. The rapidly digestible starch, slowly digestible starch, and resistant starch ranged from 2.6 to 3.7%, from 5.7 to 12.7%, and from 84.4 to 90.7%, respectively, for native starch, and from 79.6 to 89.5%, from 1.3 to 3.8%, and from 7.1 to 17.4%, respectively, for gelatinized starch.

Chinese yam is an important edible starch plant and widely cultivated in China. Its rhizome and bulbil are starch storage tissues below and above ground, respectively. In this paper, starches were isolated from the rhizome and bulbil of Chinese yam, and their structural and functional properties were compared. Both starches had an oval shape with an eccentric hilum and a C_A-type crystalline structure. Their short-range ordered structure and lamellar structure had no significant difference. However, the rhizome starch had a significantly bigger granule size and lower amylose content than the bulbil starch. The swelling power and water solubility were significantly lower in the rhizome starch than in the bulbil starch. The onset and peak gelatinization temperatures were significantly higher in the rhizome starch than in the bulbil starch. The rhizome starch had a significantly higher breakdown viscosity and a lower setback viscosity than the bulbil starch. The thermal stability was lower in the rhizome starch than in the bulbil starch. The rhizome starch had a significantly lower resistance to hydrolysis and in vitro digestion than the bulbil starch. The above results provide important information for the utilization of rhizome and bulbil starches of Chinese yam.