The physicochemical and nutritional properties of heat‐moisture treated (HMT) maize starch and maize meal with stearic acid (SA) are studied. The addition of SA followed by HMT produces nongelling starch and maize meal porridge with reduced pasting viscosity. Heat‐moisture treatment significantly (P ≤ 0.05) decreases the starch hydrolysis, increases resistant starch, and lowers estimated glycaemic index of both maize meal and maize starch with SA. These changes are due to a more organized crystalline structure between starch polymers and well as the formation of amylose–lipid complexes as shown by differential scanning calorimeter and X‐ray diffraction. There seems to be a synergistic effect between HMT and stearic addition as HMT promotes more starch polymer interaction compared to amylose–lipid formation for stearic acid addition. These results suggest that HMT combined with SA can be used to manufacture starch‐based functional ingredients and foods with reduced glycaemic index.
This paper reviews the various technologies employed to lower the glycemic index of foods and provides a future outlook for starchy foods. The glycemic index of foods can be reduced by increasing resistant starch or slowly digestible starch. However, information concerning the parameters/settings and mechanisms by which several technologies can be used are limited. Technologies such as microwave, infrared, ultrasonic, autoclaving, and high hydrostatic pressure can facilitate more interactions between food components, thereby resulting in the formation of various types of resistant starch or slowly digestible starch. Based on the findings of this paper, the use of microwave technology to produce resistant starch has been sufficiently reported in comparison to the other technologies. Given the research done in the last two decades regarding other technologies, there is a need for more research work on optimizing the parameters or processing conditions for thermal and non‐thermal technologies in order to produce low GI starch and starchy foods. There is limited work done on combination treatments that can effectively develop low GI foods. The data provided for glycemic index and starch digestibility kinetics is mostly from in vitro studies.
Xylooligosaccharides (XOS) are non-digestible oligosaccharides with a significant role as functional food ingredients in the food industry. The present research is undertaken to evaluate water soluble xylan (WSX) extraction from eight different sources using water at ambient temperature (25 ± 2 °C) and structural characterization (FTIR, NMR, XRD, and TGA). Enzymatic production of XOS from extracted substrates and its characterization using HPLC-RID and FTIR is determined. WSX from orange fleshed sweet potato peel shows highest yield (9%), while the least (2.48%) is from Teff seed coat. FTIR structural identification of xylan confirms the presence of 𝜷-glycosidic linkages and acetyl groups; whereas 1 H NMR validates the occurrence of 𝜷-D-1,4-xylopyranose backbone with 𝜶-L-arabinofuranose and 4-O-methylglucuronic acid substituents. XRD and TGA characteristics of the extracts indicate similarities in the eight sources in comparison with standard beech wood xylan. WSX is hydrolyzed with endoxylanase to obtain XOS (highest yield of 57.16 ± 1.01% in Cassava cake; lowest yield of 21.72 ± 0.72% in Bambara groundnut). HPLC-RID reveals xylobiose as the main monomeric sugar component (DP 2) and 𝜷-linkages are identified by FTIR in all the sources. The study suggests the potential commercial production of XOS from the analyzed agricultural by-products.
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