|Content:||10 mL or 40 mL or 100 mL or 100 mL (ANKOM)|
|Formulation:||In 50% (v/v) glycerol|
|Stability:||> 1 year under recommended storage conditions|
|Synonyms:||glucan 1,4-alpha-glucosidase; 4-alpha-D-glucan glucohydrolase; glucoamylase|
|Expression:||From Aspergillus niger|
|Specificity:||Hydrolysis of terminal α-1,4 and α-1,6 D-glucose residues successively from non-reducing ends of maltodextrins.|
|Specific Activity:|| ~ 3,260 U/mL (40oC, pH 4.5 on soluble starch) |
~ 200 U/mL (40oC, pH 4.5 on p-nitrophenyl β-maltoside)
|Unit Definition:||One Unit of amyloglucosidase activity is defined as the amount of enzyme required to release one µmole of D-glucose reducing-sugar equivalents per minute from soluble starch at pH 4.5 and 40oC.|
|Application examples:||Applications for the measurement of starch and dietary fiber in the food and feeds industry.|
|Method recognition:||AOAC Method 2000.11 and GB Standard 5009.245-2016|
The E-AMGDF-10ML pack size has been discontinued (read more).
High purity Amyloglucosidase (Aspergillus niger) for use in research, biochemical enzyme assays and in vitro diagnostic analysis.
For use in Megazyme Dietary Fiber methods. Amyloglucosidase, Fructanase (E-FRMXPD) and Isoamylase (E-ISAMY) are used in the enzyme hydrolysis step of two validated methods for the determination of polydextrose (a low molar mass dietary fiber) in foods: AOAC method 2000.11 and Chinese GB Standard 5009.245-2016.
E-AMGDF-A-100ML specifically to be used with ANKOMTDF Dietary Fiber Analyzer.
Data booklets for each pack size are located in the Documents tab.
We offer a wide array of Carbohydrate Active enZYme products for various uses.
Validation of Methods
Diastatic power and maltose value: a method for the measurement of amylolytic enzymes in malt.
Charmier, L. M., McLoughlin, C. & McCleary, B. V. (2021). Journal of the Institute of Brewing, In Press.
A simple method for measurement of the amylolytic activity of malt has been developed and fully evaluated. The method, termed the Maltose Value (MV) is an extension of previously reported work. Here, the MV method has been studied in detail and all aspects of the assay (sample grinding and extraction, starch hydrolysis, maltose hydrolysis and determination as glucose) have been optimised. The method is highly correlated with other dextrinising power methods. The MV method involves extraction of malt in 0.5% sodium chloride at 30°C for 20 minutes followed by filtration; incubation of an aliquot of the undiluted filtrate with starch solution (pH 4.6) at 30°C for 15 min; termination of reaction with sodium hydroxide solution; dilution of sample in an appropriate buffer; hydrolysis of maltose with a specific α-glucosidase; glucose determination and activity calculation. Unlike all subsequent reducing sugar methods, the maltose value method measures a defined reaction product, maltose, with no requirement to use equations to relate analytical values back to Lintner units. The maltose value method is the first viable method in 130 years that could effectively replace the 1886 Lintner method.Hide Abstract
Measurement of available carbohydrates, digestible, and resistant starch in food ingredients and products.
McCleary, B. V., McLoughlin, C., Charmier, L. M. J. & McGeough, P. (2019). Cereal Chemistry, 97(1), 114-137.
Background and objectives: The importance of selectively measuring available and unavailable carbohydrates in the human diet has been recognized for over 100 years. The levels of available carbohydrates in diets can be directly linked to major diseases of the Western world, namely Type II diabetes and obesity. Methodology for measurement of total carbohydrates by difference was introduced in the 1880s, and this forms the basis of carbohydrate determination in the United States. In the United Kingdom, a method to directly measure available carbohydrates was introduced in the 1920s to assist diabetic patients with food selection. The aim of the current work was to develop simple, specific, and reliable methods for available carbohydrates and digestible starch (and resistant starch). The major component of available carbohydrates in most foods is digestible starch. Findings: Simple methods for the measurement of rapidly digested starch, slowly digested starch, total digestible starch, resistant starch, and available carbohydrates have been developed, and the digestibility of phosphate cross‐linked starch has been studied in detail. The resistant starch procedure developed is an update of current procedures and incorporates incubation conditions with pancreatic α‐amylase (PAA) and amyloglucosidase (AMG) that parallel those used AOAC Method 2017.16 for total dietary fiber. Available carbohydrates are measured as glucose, fructose, and galactose, following complete and selective hydrolysis of digestible starch, maltodextrins, maltose, sucrose, and lactose to glucose, fructose, and galactose. Sucrose is hydrolyzed with a specific sucrase enzyme that has no action on fructo‐oligosaccharides (FOS). Conclusions: The currently described “available carbohydrates” method together with the total dietary fiber method (AOAC Method 2017.16) allows the measurement of all carbohydrates in food products, including digestible starch. Significance and novelty: This paper describes a simple and specific method for measurement of available carbohydrates in cereal, food, and feed products. This is the first method that provides the correct measurement of digestible starch and sucrose in the presence of FOS. Such methodology is essential for accurate labeling of food products, allowing consumers to make informed decisions in food selection.Hide Abstract
Measurement of Starch: Critical evaluation of current methodology.
McCleary, B. V., Charmier, L. M. J. & McKie, V. A. (2018). Starch‐Stärke, 71(1-2), 1800146.
Most commonly used methods for the measurement of starch in food, feeds and ingredients employ the combined action of α‐amylase and amyloglucosidase to hydrolyse the starch to glucose, followed by glucose determination with a glucose oxidase/peroxidase reagent. Recently, a number of questions have been raised concerning possible complications in starch analytical methods. In this paper, each of these concerns, including starch hydrolysis, isomerisation of maltose to maltulose, effective hydrolysis of maltodextrins by amyloglucosidase, enzyme purity and hydrolysis of sucrose and β‐glucans have been studied in detailed. Results obtained for a range of starch containing samples using AOAC Methods 996.11 and 2014 .10 are compared and a new simpler format for starch measurement is introduced. With this method that employs a thermostable α-amylase (as distinct from a heat stable α-amylase) which is both stable and active at 100°C and pH 5.0, 10 samples can be analysed within 2 h, as compared to the 6 h required with AOAC Method 2014.10.Hide Abstract
Modification to AOAC Official Methods 2009.01 and 2011.25 to allow for minor overestimation of low molecular weight soluble dietary fiber in samples containing starch.
McCleary, B. V. (2014). Journal of AOAC International, 97(3), 896-901.
AOAC Official Methods 2009.01 and 2011.25 have been modified to allow removal of resistant maltodextrins produced on hydrolysis of various starches by the combination of pancreatic α-amylase and amyloglucosidase (AMG) used in these assay procedures. The major resistant maltodextrin, 63,65-di-α-D-glucosyl maltopentaose, is highly resistant to hydrolysis by microbial α-glucosidases, isoamylase, pullulanase, pancreatic, bacterial and fungal α-amylase and AMG. However, this oligosaccharide is hydrolyzed by the mucosal α-glucosidase complex of the pig small intestine (which is similar to the human small intestine), and thus must be removed in the analytical procedure. Hydrolysis of these oligosaccharides has been by incubation with a high concentration of a purified AMG at 60°C. This incubation results in no hydrolysis or loss of other resistant oligosaccharides such as FOS, GOS, XOS, resistant maltodextrins (e.g., Fibersol 2) or polydextrose. The effect of this additional incubation with AMG on the measured level of low molecular weight soluble dietary fiber (SDFS) and of total dietary fiber in a broad range of samples is reported. Results from this study demonstrate that the proposed modification can be used with confidence in the measurement of dietary fiber.Hide Abstract
Measurement of total dietary fiber using AOAC method 2009.01 (AACC International approved method 32-45.01): Evaluation and updates.
McCleary, B. V., Sloane, N., Draga, A. & Lazewska, I. (2013). Cereal Chemistry, 90(4), 396-414.
The Codex Committee on Methods of Analysis and Sampling recently recommended 14 methods for measurement of dietary fiber, eight of these being type I methods. Of these type I methods, AACC International Approved Method 32-45.01 (AOAC method 2009.01) is the only procedure that measures all of the dietary fiber components as defined by Codex Alimentarius. Other methods such as the Prosky method (AACCI Approved Method 32-05.01) give similar analytical data for the high-molecular-weight dietary fiber contents of food and vegetable products low in resistant starch. In the current work, AACCI Approved Method 32-45.01 has been modified to allow accurate measurement of samples high in particular fructooligosaccharides: for example, fructotriose, which, in the HPLC system used, chromatographs at the same point as disaccharides, meaning that it is currently not included in the measurement. Incubation of the resistant oligosaccharides fraction with sucrase/β-galactosidase removes disaccharides that interfere with the quantitation of this fraction. The dietary fiber value for resistant starch type 4 (RS4), varies significantly with different analytical methods, with much lower values being obtained with AACCI Approved Method 32-45.01 than with 32-05.01. This difference results from the greater susceptibility of RS4 to hydrolysis by pancreatic α-amylase than by bacterial α-amylase, and also a greater susceptibility to hydrolysis at lower temperatures. On hydrolysis of samples high in starch in the assay format of AACCI Approved Method 32-45.01 (AOAC method 2009.01), resistant maltodextrins are produced. The major component is a heptasaccharide that is highly resistant to hydrolysis by most of the starch-degrading enzymes studied. However, it is hydrolyzed by the maltase/amyloglucosidase/isomaltase enzyme complex present in the brush border lining of the small intestine. As a consequence, AOAC methods 2009.01 and 2011.25 (AACCI Approved Methods 32-45.01 and 32-50.01, respectively) must be updated to include an additional incubation with amyloglucosidase to remove these oligosaccharides.Hide Abstract
Determination of insoluble, soluble, and total dietary fiber (codex definition) by enzymatic-gravimetric method and liquid chromatography: Collaborative Study.
McCleary, B. V., DeVries, J. W., Rader, J. I., Cohen, G., Prosky, P., Mugford, D. C., Champ, M. & Okuma, K. (2012). Journal of AOAC International, 95(3), 824-844.
A method for the determination of insoluble (IDF), soluble (SDF), and total dietary fiber (TDF), as defined by the CODEX Alimentarius, was validated in foods. Based upon the principles of AOAC Official MethodsSM 985.29, 991.43, 2001.03, and 2002.02, the method quantitates water-insoluble and water-soluble dietary fiber. This method extends the capabilities of the previously adopted AOAC Official Method 2009.01, Total Dietary Fiber in Foods, Enzymatic-Gravimetric-Liquid Chromatographic Method, applicable to plant material, foods, and food ingredients consistent with CODEX Definition 2009, including naturally occurring, isolated, modified, and synthetic polymers meeting that definition. The method was evaluated through an AOAC/AACC collaborative study. Twenty-two laboratories participated, with 19 laboratories returning valid assay data for 16 test portions (eight blind duplicates) consisting of samples with a range of traditional dietary fiber, resistant starch, and nondigestible oligosaccharides. The dietary fiber content of the eight test pairs ranged from 10.45 to 29.90%. Digestion of samples under the conditions of AOAC 2002.02 followed by the isolation, fractionation, and gravimetric procedures of AOAC 985.29 (and its extensions 991.42 and 993.19) and 991.43 results in quantitation of IDF and soluble dietary fiber that precipitates (SDFP). The filtrate from the quantitation of water-alcohol-insoluble dietary fiber is concentrated, deionized, concentrated again, and analyzed by LC to determine the SDF that remains soluble (SDFS), i.e., all dietary fiber polymers of degree of polymerization = 3 and higher, consisting primarily, but not exclusively, of oligosaccharides. SDF is calculated as the sum of SDFP and SDFS. TDF is calculated as the sum of IDF and SDF. The within-laboratory variability, repeatability SD (Sr), for IDF ranged from 0.13 to 0.71, and the between-laboratory variability, reproducibility SD (sR), for IDF ranged from 0.42 to 2.24. The within-laboratory variability sr for SDF ranged from 0.28 to 1.03, and the between-laboratory variability sR for SDF ranged from 0.85 to 1.66. The within-laboratory variability sr for TDF ranged from 0.47 to 1.41, and the between-laboratory variability sR for TDF ranged from 0.95 to 3.14. This is comparable to other official and approved dietary fiber methods, and the method is recommended for adoption as Official First Action.Hide Abstract
Determination of total dietary fiber (CODEX definition) by enzymatic-gravimetric method and liquid chromatography: collaborative study.
McCleary, B. V., DeVries, J. W., Rader, J. I., Cohen, G., Prosky, L., Mugford, D. C., Champ, M. & Okuma, K. (2010). Journal of AOAC International, 93(1), 221-233.
A method for the determination of total dietary fiber (TDF), as defined by the CODEX Alimentarius, was validated in foods. Based upon the principles of AOAC Official MethodsSM 985.29, 991.43, 2001.03, and 2002.02, the method quantitates high- and low-molecular-weight dietary fiber (HMWDF and LMWDF, respectively). In 2007, McCleary described a method of extended enzymatic digestion at 37°C to simulate human intestinal digestion followed by gravimetric isolation and quantitation of HMWDF and the use of LC to quantitate low-molecular-weight soluble dietary fiber (LMWSDF). The method thus quantitates the complete range of dietary fiber components from resistant starch (by utilizing the digestion conditions of AOAC Method 2002.02) to digestion resistant oligosaccharides (by incorporating the deionization and LC procedures of AOAC Method 2001.03). The method was evaluated through an AOAC collaborative study. Eighteen laboratories participated with 16 laboratories returning valid assay data for 16 test portions (eight blind duplicates) consisting of samples with a range of traditional dietary fiber, resistant starch, and nondigestible oligosaccharides. The dietary fiber content of the eight test pairs ranged from 11.57 to 47.83. Digestion of samples under the conditions of AOAC Method 2002.02 followed by the isolation and gravimetric procedures of AOAC Methods 985.29 and 991.43 results in quantitation of HMWDF. The filtrate from the quantitation of HMWDF is concentrated, deionized, concentrated again, and analyzed by LC to determine the LMWSDF, i.e., all nondigestible oligosaccharides of degree of polymerization 3. TDF is calculated as the sum of HMWDF and LMWSDF. Repeatability standard deviations (Sr) ranged from 0.41 to 1.43, and reproducibility standard deviations (SR) ranged from 1.18 to 5.44. These results are comparable to other official dietary fiber methods, and the method is recommended for adoption as Official First Action.Hide Abstract
McCleary, B. V., Mills, C. & Draga, A. (2009). Quality Assurance and Safety of Crops & Foods, 1(4), 213–224.
An integrated total dietary fibre (TDF) method, consistent with the recently accepted CODEX definition of dietary fibre, has been developed. The CODEX Committee on Nutrition and Foods for Special Dietary Uses (CCNFSDU) has been deliberating for the past 8 years on a definition for dietary fibre that correctly reflects the current consensus thinking on what should be included in this definition. As this definition was evolving, it became evident to us that neither of the currently available methods for TDF (AOAC Official Methods 985.29 and 991.43), nor a combination of these and other methods, could meet these requirements. Consequently, we developed an integrated TDF procedure, based on the principals of AOAC Official Methods 2002.02, 991.43 and 2001.03, that is compliant with the new CODEX definition. This procedure quantitates high- and low-molecular weight dietary fibres as defined, giving an accurate estimate of resistant starch and non-digestible oligosaccharides also referred to as low-molecular weight soluble dietary fibre. In this paper, the method is discussed, modifications to the method to improve simplicity and reproducibility are described, and the results of the first rounds of interlaboratory evaluation are reported.Hide Abstract
An integrated procedure for the measurement of total dietary fibre (including resistant starch), non-digestible oligosaccharides and available carbohydrates.
McCleary, B. V. (2007). Analytical and Bioanalytical Chemistry, 389(1), 291-308.
A method is described for the measurement of dietary fibre, including resistant starch (RS), non-digestible oligosaccharides (NDO) and available carbohydrates. Basically, the sample is incubated with pancreatic α-amylase and amyloglucosidase under conditions very similar to those described in AOAC Official Method 2002.02 (RS). Reaction is terminated and high molecular weight resistant polysaccharides are precipitated from solution with alcohol and recovered by filtration. Recovery of RS (for most RS sources) is in line with published data from ileostomy studies. The aqueous ethanol extract is concentrated, desalted and analysed for NDO by high-performance liquid chromatography by a method similar to that described by Okuma (AOAC Method 2001.03), except that for logistical reasons, D-sorbitol is used as the internal standard in place of glycerol. Available carbohydrates, defined as D-glucose, D-fructose, sucrose, the D-glucose component of lactose, maltodextrins and non-resistant starch, are measured as D-glucose plus D-fructose in the sample after hydrolysis of oligosaccharides with a mixture of sucrase/maltase plus β-galactosidase.Hide Abstract
Dietary fiber and available carbohydrates.
McCleary, B. V. & Rossiter, P. C. (2007). “Dietary Fiber: An International Perspective for Harmonization of Health Benefits and Energy Values”, (Dennis T. Gordon and Toshinao Goda, Eds.), AACC International, Inc., pp. 31-59.
Debate continues on the definition of dietary fiber (DF), methods for measurement of DF, and methods for measurement of the carbohydrates that are readily hydrolyzed and absorbed in the human small intestine. Henneberg and Stahmann developed the 'Wende' proximate system for analysis of foods in 1860, and a set of values obtained using this method were published by Atwater and Bryant in 1900. This method is still in use in the USA for the measurement of total carbohydrate. In this procedure, total carbohydrate is measured by difference after deducting the moisture, protein, fat and ash from the total weight. Carbohydrate calculated in this way contains not only sugar and starch, but also the 'unavailable carbohydrate' of DF. However, there are a number of problems with this approach, as the 'by difference' figure includes a number of non-carbohydrate components such as lignin, organic acids, tannins, waxes and some Maillard products. In addition to this error, it combines all of the analytical errors from the other analyses (FAO 1997). A need for information on the carbohydrate composition of foods for diabetics prompted McCance and Lawrence (1929) to attempt to measure carbohydrate composition to gain results that would be of biological significance. They divided the carbohydrates in foods into two broad groups, 'available' and 'unavailable'. The available carbohydrates, that is, sugar plus starch, were defined as those that are digested and absorbed by man and are glucogenic. The unavailable carbohydrates were defined as those that are not digested by the endogenous secretions of the human digestive tract. In the mid 1920s, McCance obtained a grant of £30 per year from the Medical Research Council to analyse raw and cooked fruits and vegetables for total "available carbohydrate"; values needed for calculating diabetic diets.Hide Abstract
Measurement of novel dietary fibres.
McCleary, B. V. & Rossiter, P. (2004). Journal of AOAC International, 87(3), 707-717.
With the recognition that resistant starch (RS) and nondigestible oligosaccharides (NDO) act physiologically as dietary fiber (DF), a need has developed for specific and reliable assay procedures for these components. The ability of AOAC DF methods to accurately measure RS is dependent on the nature of the RS being analyzed. In general, NDO are not measured at all by AOAC DF Methods 985.29 or 991.43, the one exception being the high molecular weight fraction of fructo-oligosaccharides. Values obtained for RS, in general, are not in good agreement with values obtained by in vitro procedures that more closely imitate the in vivo situation in the human digestive tract. Consequently, specific methods for the accurate measurement of RS and NDO have been developed and validated through interlaboratory studies. In this paper, modifications to AOAC fructan Method 999.03 to allow accurate measurement of enzymically produced fructo-oligosaccharides are described. Suggested modifications to AOAC DF methods to ensure complete removal of fructan and RS, and to simplify pH adjustment before amyloglucosidase addition, are also described.Hide Abstract
McCleary, B. V. (2003). Proceedings of the Nutrition Society, 62, 3-9.
The 'gold standard' method for the measurement of total dietary fibre is that of the Association of Official Analytical Chemists (2000; method 985.29). This procedure has been modified to allow measurement of soluble and insoluble dietary fibre, and buffers employed have been improved. However, the recognition of the fact that non-digestible oligosaccharides and resistant starch also behave physiologically as dietary fibre has necessitated a re-examination of the definition of dietary fibre, and in turn, a re-evaluation of the dietary fibre methods of the Association of Official Analytical Chemists. With this realisation, the American Association of Cereal Chemists appointed a scientific review committee and charged it with the task of reviewing and, if necessary, updating the definition of dietary fibre. It organised various workshops and accepted comments from interested parties worldwide through an interactive website. More recently, the (US) Food and Nutrition Board of the Institute of Health, National Academy of Sciences, under the oversight of the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, assembled a panel to develop a proposed definition(s) of dietary fibre. Various elements of these definitions were in agreement, but not all. What was clear from both reviews is that there is an immediate need to re-evaluate the methods that are used for dietary fibre measurement and to make appropriate changes where required, and to find new methods to fill gaps. In this presentation, the 'state of the art' in measurement of total dietary fibre and dietary fibre components will be described and discussed, together with suggestions for future research.Hide Abstract
Two issues in dietary fiber measurement.
McCleary, B. V. (2001). Cereal Foods World, 46, 164-165.
Enzyme activity and purity of these topics, the easiest to deal with is the importance of enzyme purity and activity. As a scientist actively involved in polysaccharide research over the past 25 years, I have come to appreciate the importance of enzyme purity and specificity in polysaccharide modification and measurement (7). These factors translate directly to dietary fiber (DF) methodology, because the major components of DF are carbohydrate polymers and oligomers. The committee report published in the March issue of Cereal FOODS WORLD refers only to the methodology for measuring enzyme purity and activity (8) that led up the AOAC method 985.29 (2). In this work enzyme purity was gauged by the lack of hydrolysis (i.e., complete recovery) of a particular DF component (e.g. β-glucan, larch galactan or citrus pectin). Enzyme activity was measured by the ability to completely hydrolyze representative starch and protein (namely wheat starch and casein). These requirements and restrictions on enzyme purity and activity were adequate at the time the method was initially developed and served as a useful working guide. However, it was recognized that there was a need for more stringent quality definitions and assay procedures for enzymes used in DF measurements.Hide Abstract
Measurement of dietary fibre components: the importance of enzyme purity, activity and specificity.
McCleary, B. V. (2001), “Advanced Dietary Fibre Technology”, (B. V. McCleary and L. Prosky, Eds.), Blackwell Science, Oxford, U.K., pp. 89-105.
Interest in dietary fibre is undergoing a dramatic revival, thanks in part to the introduction of new carbohydrates as dietary fibre components. Much emphasis is being placed on determining how much fibre is present in a food. Linking a particular amount of fibre to a specific health benefit is now an important area of research. The term 'dietary fibre' first appeared in 1953, and referred to hemicelluloses, celluloses and lignin (Theandere/tf/.1995). Trowell (1974) recommended this term as a replacement for the no longer acceptable term 'crude fibre'. Burkitt (1995) has likened the interest in dietary fibre to the growth of a river from its first trickle to a mighty torrent He observes that dietary fibre 'was first viewed as merely the less digestible constituent of food which exerts a laxative action by irritating the gut', thus acquiring the designation 'roughage' - a term later replaced by 'crude fibre' and ultimately by 'dietary fibre'. Various definitions of dietary fibre have appeared over the years, partly due to the various concepts used in deriving the term (i.e. origin of material, resistance to digestion, fermentation in the colon, etc.), and partly to the difficulties associated with its measurement and labelling (Mongeau et al. 1999). The principal components of dietary fibre, as traditionally understood, are non-starch polysaccharides (which in plant fibre are principally hemicelluloses and celluloses), and the non-carbohydrate phenolic components, cutin, suberin and waxes, with which they are associated in nature. In 1976, the definition of dietary fibre was modified to include gums and some pectic substances, based on the resistance to digestion of these components in the upper intestinal tract. For the purposes of labelling, Englyst et al. (1987) proposed that dietary fibre be defined as 'non-starch polysaccharides (NSP) in the diet that are not digested by the endogenous secretions of the human digestive tract'. Methods were concurrently developed to specifically measure NSP (Englyst et al. 1994).Hide Abstract
Importance of enzyme purity and activity in the measurement of total dietary fibre and dietary fibre components.
McCleary, B. V. (2000). Journal of AOAC International, 83(4), 997-1005.
A study was made of the effect of the activity and purity of enzymes in the assay of total dietary fiber (AOAC Method 985.29) and specific dietary fiber components: resistant starch, fructan, and β-glucan. In the measurement of total dietary fiber content of resistant starch samples, the concentration of α-amylase is critical; however, variations in the level of amyloglucosidase have little effect. Contamination of amyloglucosidase preparations with cellulase can result in significant underestimation of dietary fiber values for samples containing β-glucan. Pure β-glucan and cellulase purified from Aspergillus niger amyloglucosidase preparations were used to determine acceptable critical levels of contamination. Sucrose, which interferes with the measurement of inulin and fructooligosaccharides in plant materials and food products, must be removed by hydrolysis of the sucrose to glucose and fructose with a specific enzyme (sucrase) followed by borohydride reduction of the free sugars. Unlike invertase, sucrase has no action on low degree of polymerization (DP) fructooligosaccharides, such as kestose or kestotetraose. Fructan is hydrolyzed to fructose and glucose by the combined action of highly purified exo- and endo-inulinases, and these sugars are measured by the p-hydroxybenzoic acid hydrazide reducing sugar method. Specific measurement of β-glucan in cereal flour and food extracts requires the use of highly purified endo-1,3:1,4 β-glucanase and A. niger β-glucosidase. β-glucosidase from almonds does not completely hydrolyze mixed linkage β-glucooligosaccharides from barley or oat β-glucan. Contamination of these enzymes with starch, maltosaccharide, or sucrose-hydrolyzing enzymes results in production of free glucose from a source other than β-glucan, and thus an overestimation of β-glucan content. The glucose oxidase and peroxidase used in the glucose determination reagent must be essentially devoid of catalase and α- and β-glucosidase.Hide Abstract
Measuring dietary fibre.
McCleary, B. V. (1999). The World of Ingredients, 50-53.
Interest in dietary fibre is undergoing a dramatic revival thanks in part to the introduction of new carbohydrates as dietary fibre components. Much emphasis is being placed on determining how much fibre is present in a food. Linking a particular amount of fibre to a specific health benefit is now an important area of research. Total Dietary Fibre. The term “dietary fibre” first appeared in 1953 and referred to hemicelluloses, celluloses and lignin (1). In 1974, Trowell (2) recommended this term as a replacement for the no longer acceptable term “crude fibre” Burkitt (3) has likened the interest in dietary fibre to the growth of a river from its first trickle to a mighty torrent. He observes that dietary fibre “was viewed as merely the less digestible constituent of food which exerts a laxative action by irritating the gut “thus acquiring the designation “roughage” a term which was later replaced by “crude fibre” and ultimately by “dietary fibre” Various definitions of dietary fibre have appeared over the years, partly due the various concepts used in deriving the term (i.e. origin of material, resistance to digestion, fermentation in the colon etc.), and partly to the difficulties associated with its measurement and labelling (4). The principle components of dietary fibre, as traditionally understood, are non-starch polysaccharides, which in plant fibre are principally hemicelluloses and celluloses, and the non-carbohydrate phenolic components, cutin, suberin and waxes with which they are associated in Nature.Hide Abstract
Enzyme purity and activity in fibre determinations.
McCleary, B. V. (1999). Cereal Foods World, 44(8), 590-596.
Dietary fiber is mainly composed of plant cell wall polysaccharides such as cellulose, hemicellulose, and pectic substances, but it also includes lignin and other minor components (1). Basically, it covers the polysaccharides that are not hydrolyzed by the endogenous secretions of the human digestive tract (2,3). This definition has served as the target for those developing analytical procedures for the measurement of dietary fiber for quality control and regulatory considerations (4). Most procedures for the measurement of total dietary fiber (TDF), or specific polysaccharide components, either involve some enzyme treatment steps or are mainly enzyme-based. In the development of TDF procedures such as the Prosky method (AOAC International 985.29, AACC 32—05) (5), the Uppsala method (AACC32-25) (6), and the Englyst method (7), the aim was to remove starch and protein through enzyme treatment, and to measure the residue as dietary fiber (after allowing for residual, undigested protein and ash). Dietary fiber was measured either gravimetrically or by chemical or instrumental procedures. Many of the enzyme treatment steps in each of the methods, particularly the prosky (5) and the Uppsala (6) methods are very similar. As a new range of carbohydrates is being introduced as potential dietary fiber components, the original assay procedures will need to be reexamined, and in some cases slightly modified, to ensure accurate and quantitative measurement of these components and of TDF. These “new” dietary fiber components include resistant nondigestible oligosaccharides; native and chemically modified polysaccharides of plant and algal origin (galactomannan, chemically modified celluloses, and agars and carrageenans); and resistant starch. To measure these components accurately, the purity, activity, and specificity of the enzymes employed will become much more important. A particular example of this is the mesurement of fructan. This carbohydrate consists of a fraction with a high degree of polymerization (DP) that is precipitated in the standard Prosky method (5,8) and a low DP fraction consequently is not measured (9). Resistant starch poses a particular problem. This component is only partially resistant to degradation by α-amylase, so the level of enzyme used and the incubation conditions (time and temperature) are critical.Hide Abstract
McCleary, B. V., Bouhet, F. & Driguez, H. (1991). Biotechnology Techniques, 5(4), 255-258.
An enzyme-linked assay for the measurement of amyloglucosidase in commercial enzyme mixtures and crude culture filtrates is described. A method for the synthesis of the substrate employed, p-nitrophenyl β-D-maltoside, is also described. The substrate is used in the presence of saturating levels of β-glucosidase. With a range of Aspergillus sp. culture filtrates, an excellent correlation was found for values obtained with this assay and a conventional assay employing maltose as substrate with measurement of released glucose.Hide Abstract
McCleary, B. V. & Anderson, M. A. (1980). Carbohydrate Research, 86(1), 77-96.
Culture filtrates of Cladosporium resinae ATCC 20495 contain a mixture of enzymes able to convert starch and pullulan efficiently into D-glucose. Culture conditions for optimal production of the pullulan-degrading activity have been established. The amylolytic enzyme preparation was fractionated by ion-exchange and molecular-sieve chromatography, and shown to contain α-D-glucosidase, α-amylase, and two glucoamylases. The glucoamylases have been purified to homogeneity and their substrate specificities investigated. One of the glucoamylases (termed P) readily hydrolyses the (1→6)-α-D linkages in pullulan, amylopectin, isomaltose, panose, and 63-α-D-glucosylmaltotriose. Each of the glucoamylases cleaves the (1→6)-α-D linkage in panose much more readily than that in isomaltose.Hide Abstract
The Roles of a Native Starch and a Resistant Dextrin in Texture Improvement and Low Glycemic Index of Biscuits.
Yu, S., Dong, K., Pora, B. L. & Hasjim, J. (2022). Processes, 10(11), 2404.
Low-GI biscuits are commonly produced using whole-grain flour, bran, or soluble dietary fibers, giving an undesirable texture. New low-GI biscuits containing dietary fibers and with improved palatability were formulated by substituting 60% of wheat flour (WF) with a native starch (ST) and 15% of WF with a resistant dextrin (RD), a source of dietary fibers. The botanical source of ST was common buckwheat (Fagopyrum esculentum Moench). Biscuits were also made with a single substitution by ST or by RD at the same level for comparison. The firmness of the biscuits was increased with the single substitution by RD due to its small average molecular size and high hygroscopicity, while it was decreased with the single substitution by ST. The double substitution by ST and RD not only produced the texture with the lowest firmness and brittleness, but also led to the lowest in vitro starch digestion rate and total starch digestibility. The human trial confirmed that the biscuits with the double substitution had a low GI of 47. The results indicated the additive or synergistic effects of ST and RD on the properties of the biscuits, demonstrating that low-GI biscuits can be produced with a substantial dietary fiber content without jeopardizing their palatability.Hide Abstract
Genetic analysis of seed traits in Sorghum bicolor that affect the human gut microbiome.
Yang, Q., Van Haute, M., Korth, N., Sattler, S. E., Toy, J., Rose, D. J., Schnable, J. C. & Benson, A. K. (2022). Nature communications, 13(1), 1-15.
Prebiotic fibers, polyphenols and other molecular components of food crops significantly affect the composition and function of the human gut microbiome and human health. The abundance of these, frequently uncharacterized, microbiome-active components vary within individual crop species. Here, we employ high throughput in vitro fermentations of pre-digested grain using a human microbiome to identify segregating genetic loci in a food crop, sorghum, that alter the composition and function of human gut microbes. Evaluating grain produced by 294 sorghum recombinant inbreds identifies 10 loci in the sorghum genome associated with variation in the abundance of microbial taxa and/or microbial metabolites. Two loci co-localize with sorghum genes regulating the biosynthesis of condensed tannins. We validate that condensed tannins stimulate the growth of microbes associated with these two loci. Our work illustrates the potential for genetic analysis to systematically discover and characterize molecular components of food crops that influence the human gut microbiome.Hide Abstract
Nitrogen fertilization of rice plants before flowering affects sake fermentation and quality.
Miyamoto, T., Nishida, I., Ohtake, N. & Hirata, D. (2022). Cereal Chemistry, In Press.
Background and Objective: Nitrogen fertilizer applied as top-dressing to rice plants before flowering affects the yield and quality of rice grains. However, little is known about the effects of varying dosages of nitrogen at this stage on the brewing properties of sake using the rice grains. To explore this topic, we cultivated the sake rice cultivar “Koshitanrei” with low and high levels of nitrogen (equivalent to 10 kg and 30 kg N per hectare, respectively) applied 1 week before flowering and then conducted a small-scale sake brewing test using the harvested rice. Findings: Sake made from rice from the low-N treatment was fermented more efficiently. This yielded a higher volume of sake with a higher alcohol concentration and decreased amino acid concentrations. Conclusions: The use of rice from the low-N treatment enhanced alcohol fermentation, resulting in increased alcohol yield and decreased concentrations of amino acids and related compounds.Hide Abstract
Application of a Rapid In‐Vitro Method Based on Glucometer for Determination of Starch Digestibility and Estimated Glycaemic Index in Rice.
Srikaeo, K. Starch‐Stärke, 2200174.
Measuring the glycemic index (GI) of rice in vivo is time consuming and costly. A simple, reliable, and cost-effective in vitro digestion assay suitable for use during rice breeding and rice product development is required. The purpose of this study is to propose the use of an in vitro enzymatic starch digestion assay based on a glucometer to determine the estimated GI (eGI) of rice in both raw and cooked forms. Four rice cultivars differing in amylose contents are examined. The known GI rice cultivar, Doongara, is used as the reference. The assay includes the digestion of ground rice using all of the enzymes require to simulate the human digestive tract. The glucose released during digestion is determined using a portable hand-held glucometer over a 120-min period. The obtained starch digestograms are modeled using a first-order kinetic model, and eGI values are calculated. The assay is applicable to both raw and cooked rice samples. It can be used to classify rice according to its eGI as affected by cultivars and cooking methods. The protocol is robust, high-throughput, and adaptable to non-laboratory settings. It can benefit rice breeders, farmers, and manufacturers of rice products.Hide Abstract
Physiological responses to low CO2 over prolonged drought as primers for forest-grassland transitions.
Bellasio, C., Quirk, J., Ubierna, N. & Beerling, D. J. (2022). Nature Plants, 8(9), 1014-1023.
Savannahs dominated by grasses with scattered C3 trees expanded between 24 and 9 million years ago in low latitudes at the expense of forests. Fire, herbivory, drought and the susceptibility of trees to declining atmospheric CO2 concentrations ([CO2]a) are proposed as key drivers of this transition. The role of disturbance is well studied, but physiological arguments are mostly derived from models and palaeorecords, without direct experimental evidence. In replicated comparative experimental trials, we examined the physiological effects of [CO2]a and prolonged drought in a broadleaf forest tree, a savannah tree and a savannah C4 grass. We show that the forest tree was more disadvantaged than either the savannah tree or the C4 grass by the low [CO2]a and increasing aridity. Our experiments provide insights into the role of the intrinsic physiological susceptibility of trees in priming the disturbance-driven transition from forest to savannah in the conditions of the early Miocene.Hide Abstract
Four stages of multi-scale structural changes in rice starch during the entire high hydrostatic pressure treatment.
Zhang, X., Wang, C., Liu, Z., Xue, Y., Zhao, Q. & Shen, Q. (2023). Food Hydrocolloids, 134, 108012.
The degree of gelatinization (DG) was used as the variable to describe changes in the multi-scale structure of rice starch during the entire high hydrostatic pressure treatment (HHP-treatment), and four stages were identified. (1) Energy accumulation (100-400 MPa, DG<10%): water molecules were pressed into the amorphous lamellae and starch continued to receive energy with the increasing pressure, which resulted in the loosening of hierarchical structures. (2) Disruption of low-level structures (400-600 MPa, 10% < DG<30%): more water molecules entered the crystalline lamellae, leading to the disruption of the molecular and helical structures. The lowest Mw, Mn and Rz and the highest ρ values were observed and the content of helical structure decreased significantly. (3) Destruction of high-level structures (400-600 MPa, 30% < DG<50%): both the entry of water molecules and the alteration of low-level structures reduced the amount of short-ordered structure and crystalline structure, as well as the thickness of lamellar structure. The starch granules were deformed, and the particle size increased significantly. (4) Disintegration of all hierarchical structures (400-600 MPa, 50% < DG<100%): all hierarchical starch structures were progressively destroyed and the “broken gel fragments” were formed. This study reveals four stages of structural changes in the HHP-treated rice starch, which provides theoretical guidance for obtaining modified starch with different properties under the HHP-treatment.Hide Abstract