|GREWAL, NAVNEET - Kansas State University|
|FAUBION, JON - Kansas State University|
|FENG, GUOHUA - Kansas State University|
|SHI, YONG-CHENG - Kansas State University|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2015
Publication Date: 4/25/2015
Citation: Grewal, N., Faubion, J., Feng, G., Kaufman, R.C., Wilson, J.D., Shi, Y. 2015. Structure of waxy maize starch hydrolyzed by maltogenic alpha-amylase in relation to its retrogradation. Journal of Agricultural and Food Chemistry. DOI: 10.1021/jf506215s.
Interpretive Summary: Bread staling is one of biggest challenges faced by the baking industry because it leads to substantial economic losses. Starch undergoes structural changes both during and after the baking process that greatly determine the quality of the final product. During cooling and storage of baked products, starch retrogrades, resulting in an increase in crumb firmness and decreased crumb resilience. In this study, to understand how maltogenic alpha-amylase affects the retrogradation of amylopectin (AP), we subjected cooked waxy maize starch (WMS) which contained only AP, to different degrees of hydrolysis (DH) by maltogenic alpha-amylase and examined the structure and retrogradation properties of the resulting hydrolysates. Our objective was to study the action of maltogenic alpha-amylase on AP, relate the structure of the hydrolysates to their retrogradation properties, and determine how much hydrolysis was needed to prevent AP from retrogradation. Our results showed a higher proportion of short outer AP chains that cannot participate in formation of double helices support the decrease in and eventual inhibition of retrogradation observed with increase in % DH. These results indicate that the maltogenic amylase plays a powerful role in inhibiting the staling of baked products even with limited starch hydrolysis.
Technical Abstract: Maltogenic a-amylase is widely used as an antistaling agent in bakery foods. The objective of this study was to determine the degree of hydrolysis (DH) and starch structure after maltogenic amylase treatments in relation to its retrogradation. Waxy maize starch was cooked and hydrolyzed to different degrees by a maltogenic amylase. High-performance anion-exchange chromatography and size exclusion chromatography were used to determine saccharides formed and the molecular weight (Mw) distributions of the residual starch structure, respectively. Chain length (CL) distributions of debranched starch samples were further related to amylopectin (AP) retrogradation. Differential scanning calorimetry (DSC) results showed the complete inhibition of retrogradation when starches were hydrolysed to = 20% DH. Mw and CL distributions of residual AP structure indicated that with an increase in % DH, a higher proportion of unit chains with degree of polymerization (DP) = 9 and a lower proportion of unit chains with DP = 17 were formed. A higher proportion of short outer AP chains that cannot participate in formation of double helices support the decrease in and eventual inhibition of retrogradation observed with increase in % DH. These results indicate that the maltogenic amylase plays a powerful role in inhibiting the staling of baked products even at limited starch hydrolysis.