Abstract
The aim of this study was to characterize the influence of Konjac glucomannan (KGM) on the functional and structural properties of wheat starch. Results showed that KGM significantly decreased the starch hydrolysis rate, with a lower level of rapidly digestible starch (RDS), and a higher content of slowly digestible starch (SDS). Besides, KGM decreased the content of leached amylose, while enhanced the swelling power, water‐holding capacity, freeze‐thaw stability, and paste clarity of wheat starch, which indicated a good improvement on the functional properties. Differential scanning calorimetry (DSC) and X‐ray diffraction patterns (XRD) manifested that the addition of KGM disrupted the original crystalline structures of wheat starch, which may result in the increased hydrolysis rate of starch. Interestingly, this did not consist with the decreased starch hydrolysis rate showed in the study. Moreover, FTIR results showed the existence of the interaction between KGM and starch. The morphological characterization demonstrated that the addition of KGM contributed to a more compact structure of freeze‐dried wheat starch. And KGM inhibited the expansion of starch granules and formed a barrier around the gelatinized starch. Therefore, the barrier around the starch granules and the interaction between KGM and starch were considered to be the important reasons that affected the starch digestibility.
Highlights
Starch is the main nutrition components in the human diet, which widely exist in seed endosperm (Cornell & Eliasson, 2004)
The leached amylose would interact with Konjac glucomannan (KGM) that led to the formation of KGM–amylose complex, which might generate more slowly digestible starch (SDS) (Nawab et al, 2014)
The lower level of leached amylose suggested that the KGM may have formed a barrier around the starch, which prevented the diffusion of amylose during the gelatinization
Summary
Starch is the main nutrition components in the human diet, which widely exist in seed endosperm (Cornell & Eliasson, 2004). Various food additives (dietary fiber, polyphenol, enzymes, etc.) are used to improve the functional properties of starch (Han, Cheng, & Qiu, 2013; Matuda, Chevallier, de Alcântara Pessôa Filho, LeBail, & Tadini, 2008; Sun & Miao, 2019). Among these additives, dietary fiber can be used to modify the structural properties of starch, which intimately associated with the gelling and texture properties of starchy foods (Shevkani, Singh, Bajaj, & Kaur, 2017; Wüstenberg, 2015). Adding dietary fiber to starchy food is a good choice for the functional food market.
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