Enzyme digestibility and acid/shear stability of heat–moisture treated canna starch

Abstract

The stability of heat–moisture treated (HMT) canna starches (starches with moisture contents of 15, 18, 20, 22, and 25%, treated at 100°C for 16 h) against acid, high shearing forces, and enzyme digestion was investigated. Micrographs of starch gels taken from a Rapid Visco Analyzer showed that granules of untreated native starch subjected to pH values of 7.2 and 4.6 were highly swelled, whereas granules exposed to higher acidic pH (3.0) values fragmented into small pieces. Yet, less swelling was found for the HTN15%, HMT18%, and HMT20% samples. Even at pH 3.0, HMT22% and HMT25% granules were still in an intact granular form. Similar findings were observed when native and HMT canna starches were agitated at various rates (160, 240, 320, and 480 rpm). Starch samples treated under higher moisture levels exhibited a higher tolerance to shearing forces acting on them. Comparative investigation of HMT and chemically crosslinked starches showed that pasting properties of HMT22% and HMT25% were equivalent to those of canna starches crosslinked by sodium trimetaphosphate at 0.2 and 0.5% (dwb), respectively. In regards to the enzyme digestibility of treated canna starches, there was no recognizable trend. The extent of starch hydrolysis (at 24 h) as a function of moisture level during HMT conformed to the following order: HMT25% > HTN15% > HMT18% ≈ native > HMT20% > HMT22%.

Physical Modification of Food Starch Functionalities

“…With regard to pasting properties, HMT starches almost always exhibit an increased pasting temperature or time, along with decreased peak and trough viscosities and breakdown, compared to native starches (Hoover et al 1993;Hoover & Vasanthan 1994;Eerlingen et al 1997;Kurakake et al 1997;Adebowale & Lawal 2003;Singh et al 2005Singh et al , 2009Stevenson et al 2005;Luo et al 2006;Adebowale et al 2009;Chung et al 2009a;Watcharatewinkul et al 2009Watcharatewinkul et al , 2010Jyothi et al 2010;Olu-Owolabi et al 2011;Pinto et al 2012;Zavareze et al 2012b;Kim & Huber 2013;Yadav et al 2013;Andrade et al 2014;Balasubramanian et al 2014;Sankhon et al 2014;Sun et al 2014a,b). HMT effects on setback and final viscosities vary among literature reports.…”

“…Findings regarding the retrogradation stability of starch pastes or gels are mixed for HMT starches (Takaya et al 2000, Gunaratne & Hoover 2002, Miyoshi 2002, Lawal & Adebowale 2005, Adebowale et al 2009, Olu-Owolabi et al 2011, Singh et al 2011, Tattiyakul et al 2012, Ovando-Martínez et al 2013, differing according to starch botanical source and HMT conditions (Hoover 2010). In short, although HMT starches generally possess both improved heat and shear stabilities relative to native starches, even akin to those of chemically cross-linked starches, the improved stability comes at the cost of reduced swelling, which could require higher quantities of starch to achieve needed viscosity development for intended applications (Watcharatewinkul et al 2010). …”

Microstructural and physicochemical properties of heat-moisture treated waxy and normal starches

“…As mentioned by Watcharatewinkul et al (2010), the digestion of starch granules is a complex process that involves the accessibility (diffusion and adsorption) and hydrolytic activity of the enzyme towards the substrate. The accessibility of a-amylase is determined principally by the physical appearance (i.e., smoothness of granule surface, peripheral pores and channels inside the granule, and specific surface area) of starch granules, whereas the hydrolytic activity depends mainly on the supramolecular arrangement of starch molecules in granules.…”

Recent trend in the physical and chemical modification of starches from different botanical sources: A review

“…Additionally, most starch granules are inert, insoluble at ambient temperature, highly resistant to enzymatic hydrolysis and therefore lack specific functional properties. Native starches are often modified to develop specific properties such as solubility, texture, adhesion, and heat tolerance, so as to be suitable for industrial applications . There are many different methods of modifying starch biopolymers .…”