Barley Grain Constituents, Starch Composition, and Structure Affect Starch in Vitro Enzymatic Hydrolysis

Abstract

The relationship between starch physical properties and enzymatic hydrolysis was determined using ten different hulless barley genotypes with variable carbohydrate composition. The ten barley genotypes included one normal starch (CDC McGwire), three increased amylose starches (SH99250, SH99073, and SB94893), and six waxy starches (CDC Alamo, CDC Fibar, CDC Candle, Waxy Betzes, CDC Rattan, and SB94912). Total starch concentration positively influenced thousand grain weight (TGW) (r(2) = 0.70, p < 0.05). Increase in grain protein concentration was not only related to total starch concentration (r(2) = -0.80, p < 0.01) but also affected enzymatic hydrolysis of pure starch (r(2) = -0.67, p < 0.01). However, an increase in amylopectin unit chain length between DP 12-18 (F-II) was detrimental to starch concentration (r(2) = 0.46, p < 0.01). Amylose concentration influenced granule size distribution with increased amylose genotypes showing highly reduced volume percentage of very small C-granules (<5 μm diameter) and significantly increased (r(2) = 0.83, p < 0.01) medium sized B granules (5-15 μm diameter). Amylose affected smaller (F-I) and larger (F-III) amylopectin chains in opposite ways. Increased amylose concentration positively influenced the F-III (DP 19-36) fraction of longer DP amylopectin chains (DP 19-36) which was associated with resistant starch (RS) in meal and pure starch samples. The rate of starch hydrolysis was high in pure starch samples as compared to meal samples. Enzymatic hydrolysis rate both in meal and pure starch samples followed the order waxy > normal > increased amylose. Rapidly digestible starch (RDS) increased with a decrease in amylose concentration. Atomic force microscopy (AFM) analysis revealed a higher polydispersity index of amylose in CDC McGwire and increased amylose genotypes which could contribute to their reduced enzymatic hydrolysis, compared to waxy starch genotypes. Increased β-glucan and dietary fiber concentration also reduced the enzymatic hydrolysis of meal samples. An average linkage cluster analysis dendrogram revealed that variation in amylose concentration significantly (p < 0.01) influenced resistant starch concentration in meal and pure starch samples. RS is also associated with B-type granules (5-15 μm) and the amylopectin F-III (19-36 DP) fraction. In conclusion, the results suggest that barley genotype SH99250 with less decrease in grain weight in comparison to that of other increased amylose genotypes (SH99073 and SH94893) could be a promising genotype to develop cultivars with increased amylose grain starch without compromising grain weight and yield.

Genome-wide Association Study of Resistant Starch (RS) Phenotypes in a Barley Variety Collection

“…40 Whereas the ability of β-glucan to lower the GI was dependent on barley starch type, the GI-increasing effect by waxy starch could counteract the GI-reducing action by β-glucan. 41 The β-glucan content was higher in waxy-and increased-amylose genotypes and positively affected the slowly digested starch, 5 whereas Huang et al 11 and Lee et al 42 found that there were negative correlations between amylose and β-glucan content. More precisely, they actually claimed a negative correlation between RS 3 and β-glucan, and in the present study RS 2 (and not RS 3 ) was measured, thus leading to a different but not necessarily conflicting conclusion.…”

Wheat Belly—An Analysis of Selected Statements and Basic Theses from the Book

“…Root starches such as cooked potato and taro are also readily converted to blood glucose. Furthermore, some cereals bred to have higher amounts of amylose, such as high-amylose wheat or maize, are digested slowly (20) and may actually not be digested at all, becoming resistant starch instead.…”

Prowashonupana barley dietary fibre reduces body fat and increases insulin sensitivity in Caenorhabditis elegans model

“…Barley is the fourth most important cultivated foodstuff, and contains 62–77% starch (w/w) which is composed of 25–35% atypical amylose starch with 3–5% RS type 3 (RS 3 ) and β-glucan (Asare et al, 2011; Vasanthan & Bhatty, 1998), a mixture that provides a distinctive amylose-amylopectin interaction (Behall, Scholfield, & Hallfrisch, 2005; Dongowski, Huth, Gebhardt, & Flamme, 2002; Lifschitz, Grusak, & Butte, 2002; Rendell et al, 2005; Tang, Ando, Watanabe, Takeda, & Mitsunaga, 2001). Barley also contains high levels of functional lipids, such as, total phytosterols (1.2–9.6% of barley oil) and total tocotrienols (0.3–0.6% of barley oil) which are 6–12 fold higher than in palm oil (0.05%) and 4–8 fold higher than in rice bran oil (0.08%) (Moreau, Flores, & Hicks, 2007).…”