In the present study sweet potato starch was treated with hydrochloric acid or citric acid at 1 or 5 % concentration and its properties were investigated. Citric acid treatment resulted higher starch yield. Water holding capacity and water absorption index was increased with increased acid concentration. Emulsion properties improved at 5 % acid concentration. The DE value of acid-thinned sweet potato starches was ranged between 1.93 and 3.76 %. Hydrochloric acid treated starches displayed a higher fraction of amylose. X-ray diffraction (XRD) study revealed that all the starches displayed C-type crystalline pattern with varied crystallinity. FT-IR spectra perceived a slight change in percentage intensity of C-H stretch of citric acid modified starches. Starch granules tended to appear less smooth than the native starch granules after acid treatment in Scanning Electron Micrographs (SEM) with granule size ranging between 8.00 and 8.90 μm. A drastic decrease in the pasting profile was noticed in hydrochloric acid (5 %) treated starch. While 5 % citric acid treated starch exhibited higher pasting profile. Differential Scanning Calorimeter (DSC) showed that peak and conclusion gelatinisation temperatures increased with increase in hydrochloric acid or citric acid concentration. Hence citric acid was found to mimic the hydrochloric acid with some variation which suggests that it may have promising scope in acid modification.

Chickpea starch was subjected to triple retrogradation cycle with time intervals of 24, 48 and 72 h. The impact on in vitro digestibility, functional, pasting and structural characteristics was investigated. Compared to native chickpea starch, the resistant starch (RS) content of triple retrograded starch was significantly increased with increased retrogradation time whereas slowly digestible starch content was decreased. Water binding capacity and solubility of triple retrograded starch were significantly increased whereas swelling power and pasting properties were decreased. Triple retrograded starches showed B type and B ? V type crystalline structure. After triple retrogradation, the organised granular structure was disrupted, irregularly shaped particles were formed showing porous, coarse, filamentous network structure. FT-IR spectra perceived a slight change in percentage intensity of C-H stretch of triple retrograded starches (TRSs). Triple retrogradation was observed to be a promising methods for RS product.

Fat mimicking properties of citric acid treated sweet potato starch were investigated in this present study. Citric acid treated sweet potato starch was prepared by treating the native sweet potato starch with 3% citric acid for 6 h at a temperature of 45°C. Dextrose equivalent value of citric acid treated sweet potato starch was 2.05%. A significant increase in amylose content was noticed in citric acid treated sweet potato starch possibly due to the lyses of amylopectin fractions. The melting temperature of citric acid treated sweet potato starch was 51.44°C, which was close to the melting point of fat. Citric acid treated sweet potato starch exhibited superior water holding capacity and in vitro digestibility. Gel strength and enthalpy (ΔH) of citric acid treated sweet potato starch were comparatively lower than native sweet potato starch; correspondingly, citric acid treated sweet potato starch confirmed a low pasting profile. Native sweet potato starch and citric acid treated sweet potato starch exhibited a shearthinning behavior. Acid treatment did not alter the granule size of native sweet potato starch (≈8 µm). Hence, this study concluded that citric acid treated sweet potato starch would be used as a potential fat replacer in food preparations due to its fat mimicking properties.