Structural Changes of High-Amylose Rice Starch Residues following in Vitro and in Vivo Digestion

Abstract

High-amylose cereal starch has a great benefit on human health through its resistant starch content. In this paper, starches were isolated from mature grains of high-amylose transgenic rice line (TRS) and its wild-type rice cultivar Te-qing (TQ) and digested in vitro and in vivo. The structural changes of digestive starch residues were characterized using DSC, XRD, (13)C CP/MAS NMR, and ATR-FTIR. TQ starch was very susceptible to digestion; its residues following in vitro and in vivo digestion showed similar structural characteristics with TQ control starch, which suggested that both amorphous and crystalline structures were simultaneously digested. Both amorphous and the long-range order structures were also simultaneously hydrolyzed in TRS starch, but the short-range order (double helix) structure in the external region of TRS starch granule increased with increasing digestion time. The A-type polymorph of TRS C-type starch was hydrolyzed more rapidly than the B-type polymorph. These results suggested that B-type crystallinity and short-range order structure in the external region of starch granule made TRS starch resistant to digestion.

In vitro digestion properties of heterogeneous starch granules from high-amylose rice

“…4B). The similar crystalline type and peak intensity during digestion of the polygonal starch was consistent with the report of side-by-side digestion of crystalline and amorphous regions in normal rice and maize starches (Man et al, 2012;Zhang et al, 2006), which also indicated that the polygonal starch was similar to TQ starch in crystalline structure variation during digestion. The aggregate starch residues at 20 min of digestion had similar C-type crystallinity to native starch, but the shoulder peak at 18 2q vanished at 8 h of digestion (Fig.…”

“…The distribution of amylose was significantly different in these heterogeneous starch granules (Cai et al, 2014a). In our previous report, the amylose content of rice TQ starch did not significantly change during digestion (Man et al, 2012). Zhang, Ao, and Hamaker (2006) also reported the side-by-side digestion of amylose and amylopectin in normal maize granules.…”

“…Along with the prolongation of digestion time, the decrease of digestion rate arose from two main causes: Firstly, the concentration of available starch substrate decreased with time as starch was converted to products (Butterworth, Warren, Grassby, Patel, & Ellis, 2012). Secondly, the undigested starch residues with structure change from C-to B-type crystallinity and increasing short-range order structure increased the resistance to enzyme hydrolysis in highamylose rice starch (Man et al, 2012). The different variation patterns of digestion rates of TRS total and heterogeneous starch granules during digestion indicated that these starches had different digestion properties.…”

“…Resistant starch enriched food can lower the glycemic and insulin responses and reduce the risk for developing type II diabetes, obesity, and cardiovascular disease (Nugent, 2005). In general, starches with high amylose content have high resistance to digestion, and are of interest because of their health benefits for humans (Carciofi et al, 2012;Man et al, 2012;Regina et al, 2006;Slade et al, 2012;Zhu et al, 2012). Many high-amylose cereal varieties have been developed via mutation or transgenic breeding approaches (Carciofi et al, 2012;Regina et al, 2006;Slade et al, 2012;Zhu et al, 2012).…”

Digestibility and changes to structural characteristics of green banana starch during in vitro digestion

“…The crystalline degree of WS increased at initial digestion and 263 decreased rapidly. The similar phenomenon of WBS and WS could be attributed to 264 initial hydrolysis of the amorphous region, which results in a relatively high content 265 of crystalline region, or to reordering of the chain segments deriving from cleavage of 266 amorphous starch chains (Man, et al, 2012). 267…”