Comparative Study on the Effects of Citric Acid Modification and Hydroxypropylation on the Physiochemical and Digestibility Characteristics of Acid‐Hydrolyzed Corn and Sorghum Starches
2021
Shaikh, Faiza | Ali, Tahira Mohsin | Mustafa, Ghulam | Hasnain, Abid
Sorghum (Sorghum bicolor L.) crop is of great importance as it can be grown in drought‐hit areas. The starch extracted from sorghum has properties similar to corn (Zea mays L.) starch and is therefore considered as a productive future alternative. Starch has many technological constraints and the modifications help in improving the properties. Corn and sorghum starches are acid‐thinned prior to citric acid modification and hydroxypropylation. The acid‐hydrolyzed citrate and hydroxypropylated starches are characterized for their functional and digestibility characteristics. The modifications help in maintaining the resistant starch fraction of acid‐thinned starches. The resistant starch fraction ranges between 59–64% and 53–68% for corn and sorghum starch, respectively. The Fourier Transform Infrared spectroscopy results show decrease in crystalline to amorphous ratio (R = 1047 cm⁻¹/1022 cm⁻¹) for sorghum starch citrates. The X‐ray diffraction pattern exhibits a decrease the proportion of crystallinity of acid‐hydrolyzed esterified starches. Differential scanning calorimetry curves exhibit decreased gelatinization enthalpy for both modifications. A significant decrease (p ≤ 0.05) in peak viscosity is also observed for hydroxypropylated starches. The modifications increase the slowly digestible fraction of corn and sorghum starches from 12.7% to 24.4% and from 16.7% to 28.9%, respectively.
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