New developments in the measurement of α-amylase, endo-protease, β-glucanase and β-xylanase.
McCleary, B. V. & Monaghan, D. (2000). “Proceedings of the Second European Symposium on Enzymes in Grain Processing”, (M. Tenkanen, Ed.), VTT Information Service, pp. 31-38.
Over the past 8 years, we have been actively involved in the development of simple and reliable assay procedures, for the measurement of enzymes of interest to the cereals and related industries. In some instances, different procedures have been developed for the measurement of the same enzyme activity (e.g. α-amylase) in a range of different materials (e.g. malt, cereal grains and fungal preparations). The reasons for different procedures may depend on several factors, such as the need for sensitivity, ease of use, robustness of the substrate mixture, or the possibility for automation. In this presentation, we will present information on our most up-to-date procedures for the measurement of α-amylase, endo-protease, β-glucanase and β-xylanase, with special reference to the use of particular assay formats in particular applications.
Measurement of cereal α-Amylase: A new assay procedure.
McCleary, B. V. & Sheehan, H. (1987). Journal of Cereal Science, 6(3), 237-251.
A new procedure for the assay of cereal α-amylase has been developed. The substrate is a defined maltosaccharide with an α-linked nitrophenyl group at the reducing end of the chain, and a chemical blocking group at the non-reducing end. The substrate is completely resistant to attack by β-amylase, glucoamylase and α-glucosidase and thus forms the basis of a highly specific assay for α-amylase. The reaction mixture is composed of the substrate plus excess quantities of α-glucosidase and glucoamylase. Nitrophenyl-maltosaccharides released on action of α-amylase are instantaneously cleaved to glucose plus free p-nitrophenol by the glucoamylase and α-glucosidase, such that the rate of release of p-nitrophenol directly correlates with α-amylase activity. The assay procedure shows an excellent correlation with the Farrand, the Falling Number and the Phadebas α-amylase assay procedures.
A new procedure for the measurement of fungal and bacterial α-amylase.
Sheehan, H. & McCleary, B. V. (1988). Biotechnology Technniques, 2(4), 289-292.
A procedure for the measurement of fungal and bacterial α-amylase in crude culture filtrates and commercial enzyme preparations is described. The procedure employs end-blocked (non-reducing end) p-nitrophenyl maltoheptaoside in the presence of amyloglucosidase and α-glucosidase, and is absolutely specific for α-amylase. The assay procedure is simple, reliable and accurate.
Measurement of β-amylase in cereal flours and commercial enzyme preparations.
McCleary, B. V. & Codd, R. (1989). Journal of Cereal Science, 9(1), 17-33.
A procedure previously developed for the assay of cereal-flour β-amylase has been improved and standardised. The improved procedure uses the substrate p-nitrophenyl maltopentaose (PNPG5) in the presence of near saturating levels of α-glucosidase. PNPG5 is rapidly hydrolysed by β-amylase but less readily by cereal α-amylases. The substrate is hydrolysed by β-amylase to maltose and p-nitrophenyl maltotriose (PNPG3). With the levels of α-glucosidase used in the substrate mixture, PNPG3 is rapidly cleaved to glucose and p-nitrophenol, whereas PNPG5 is resistant to hydrolysis by the α-glucosidase. The assay procedure has been standardised for several β-amylases and the exact degree of interference by cereal α-amylases determined. The procedure can be readily applied to the selective measurement of β-amylase activity in cereal and malted cereal-flours.
Measurement of α-Amylase in Cereal, Food and Fermentation Products.
McCleary, B. V. & Sturgeon, R. (2002). Cereal Foods World, 47, 299-310.
In General, the development of methods for measuring α-amylase is pioneered in the clinical chemistry field and then translated to other industries, such as the cereals and fermentation industries. In many instances, this transfer of technology has been difficult or impossible to achieve due to the presence of interfering enzymes or sugars and to differences in the properties of the enzymes being analysed. This article describes many of the commonly used methods for measuring α-amylase in the cereals, food, and fermentation industries and discusses some of the advantages and limitations of each.
Role of amylolytic activities during pregermination on rice kernel morphology and physicochemical properties of isolated starch.
Kupkanchanakul, W., Thongngam, M., Shi, Y. C. & Naivikul, O. (2018). Cereal Chemistry, 95(4), 543-554.
Background and objectives: The role of amylolytic activities during four stages of pregermination varying on embryonic growth length between 0.5 and 7.0 mm on dynamic changes of rice kernel morphology and chemical composition, crystallinity, and thermal properties of isolated starches from three different Thai rice cultivars-SPT1 (waxy), PTT1 (low amylose), and PNL2 (high amylose)-were investigated. Findings: Amylolytic activities of all rice cultivars significantly increased at each progressive stage, whereas SPT1 showed the highest increase in alpha‐amylase activity as the first stage of pregermination. Scanning electron micrographs showed the radial crack of kernel, appearance of individual and nonuniform starch granules after pregermination, particularly of the SPT1 cultivar. Molecular weight distribution of pregerminated brown‐rice starch (PGBRS) indicated the partial hydrolysis of starch molecules especially amylopectin, resulting in a decrease fraction of high MW molecules after pregermination. All PGBRS had A‐type X‐ray diffraction patterns with higher relative crystallinity than their natives, except that of PNL2 cultivar. Pregermination led to the change onset temperature (To) of starch gelatinization (gel_p1) and retrograded amylopectin melting (ret_p1) of PGBRS for all rice cultivars and peak temperature (Tp) of gel_p1 and ret_p1 of PGBRS for only SPT1 cultivar, whereas SPT1 was found at the lower stage than other cultivars. PGBRS at the second and third stage for SPT1, after the third stage for PTT1, and after the second stage for PNL2 had lower enthalpy (ΔH) of ret_p1 than their natives. Conclusions: Alpha‐amylase activity plays a role in partial hydrolysis of amylopectin at amorphous region during rice pregermination which resulted in significant changes of thermal properties for all rice, especially SPT1 cultivar. Pregermination with 2-3‐mm EGL of all rice could be used as starch bio‐modification to obtain a lower retrograded starch as a functional ingredient of rice‐based products. Significance and novelty: The change in thermal properties of waxy SPT1 rice cultivar, which mostly contained amylopectin and highly increased alpha‐amylase activity after first stage of pregermination, was more pronounced than those of nonwaxy PTT1 and PNL2 rice cultivars.