Effect of Starch on the Inactivation of Amylase in Starch-Containing Foods

Abstract

The quality of starch-containing foods is significantly impaired by contamination with small amounts of α-amylase, which hydrolyzes the starch and causes viscosity loss. We examined the effect of different temperatures and times on inactivation of α-amylase in starch-containing foods. Model foods containing a known amount of human salivary α-amylase (HSA) were incubated at temperatures from 60 to 80℃ for 30 min. In the case of a 3% starch suspension incubated at 70℃, it took 10 min before the viscosity loss ceased, by which time the viscosity was halved. In 0.1 − 3% starch suspensions at pH 5.5, the inactivation of HSA could be described by a first order kinetic model. The presence of starch decreased the inactivation rate constant by decreasing the Arrhenius frequency factor. To prevent viscosity loss by α-amylase contamination in starch-containing foods, the inactivation time and temperature should be increased with increasing concentration of starch.Keywords: α-amylase, inactivation, thermostability, starch-containing food, viscosity *To whom correspondence should be addressed. E-mail: k-koyama@housefoods.co.jp IntroductionEffective use of starch in the food industry requires a thorough understanding of the enzymatic properties of amylase and the degradation behavior of starch. The increase in viscosity of starch-containing foods is largely due to the gelatinization of starch during heating. Viscosity is an important quality factor for thickened foods, such as soups, stews and curries that contain 5% or less starch. If a trace amount of amylase contaminates starch-containing foods, it can hydrolyze the starch and cause viscosity loss. Possible sources of amylase contamination include honey, spices, grains, fermented food, human saliva left on a tasting spoon and enzyme-containing dishwashing detergent.To prevent viscosity loss by non-thermophilic amylase contamination, starch-containing foods need to be heated to inactivate the amylase. However, using more heat than is necessary will reduce the freshness of the food. Food manufacturers have empirically found that heating at approx. 80℃ results in amylase inactivation.The thermostability of amylase increases in the pres-

A Novel Digestive α-Amylase from Blue Crab (Portunus segnis) Viscera: Purification, Biochemical Characterization and Application for the Improvement of Antioxidant Potential of Oat Flour

“…Thermostability enhancement of purified α-amylases in the presence of its substrate was supported by the results of Maalej et al [ 42 ]. Furthermore, Koyama et al [ 43 ] reported that low concentrations of starch enhanced thermostability of the human salivary α-amylase (HSA) which binds starch, forming an enzyme–substrate complex that stabilizes the enzyme.…”

Importance of Inactivation Methodology in Enzymatic Processing of Raw Potato Starch: NaOCl as Efficient α-Amylase Inactivation Agent

“…It is suspected that the high pH stability exhibited by the α-amylases in this study is due to the presence of starch, which might prevent irreversible denaturation at extreme pH values by maintaining the structural integrity of the enzyme. The starch may create a microenvironment that allows the α-amylases to retain or re-adopt a native functional conformation, first of all, by shielding the catalytic carboxylic acid residues in the active site from being ionized, and secondly, by promoting non-covalent interactions, such as aromatic pi-stacking and hydrogen bonding, between residues on the surface of the α-amylases and the glucose rings of the substrate [ 14 , 15 , 32 ]. Because of this, temporarily lowering or increasing the pH, even to extreme values, is not a recommended inactivation method when assessing controlled modification of raw starch using α-amylases.…”

“…Contamination with even small amounts of α-amylase can have many adverse effects on the quality and storage stability of starch-containing food. However, the efficient inactivation of α-amylases can be a challenge in starch systems as the presence of the substrate may enhance the structural stability of the enzyme [ 14 , 15 ]. Moreover, the inactivation method has to be chosen with special caution when assessing controlled enzymatic depolymerization of raw starch, as extreme pH or temperature may cause unspecific hydrolysis and/or gelatinization of the starch.…”

Study of starch hydrolysis by α–amylasefrom porcine pancreas with deactivation of enzyme

“…Starch hydrolysis kinetics can be described by Michaelis-Menten kinetic model (Rodríguez et al, 2006;Gopal and Muralikrishna, 2009;Koyama et al, 2013). The Michaelis-Menten constant Km assumed was much less than the concentration of starch (Km<<S) thus, the change of starch concentrations S in time t an isothermal of in starch hydrolysis by α-amylase can be described by the following equation…”

“…It should be noted that the researchers, taking into account the kinetics of starch hydrolysis, did not present the effect of α-amylase deactivation affecting the starch hydrolysis. In most cases, deactivation of α-amylase has been presented as a temperature effect without starch hydrolysis (Apar and Özbek, 2004) or enzyme concentration on starch hydrolysis Özbek, 2004a, 2005;Koyama et al, 2013;Rodríguez et al, 2006;Presečki et al, 2013). The results of studies on starch hydrolysis with α-amylase deactivation, according to the first order deactivation of α-amylase model were presented by Özbek (2004a, 2005), where α-amylase was derived from Bacillus spp.…”