Integrated Total Dietary Fiber Assay Kit

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00:00  Principle of the Assay
02:12    Kit Contents
02:40   Reagent Preparation
07:05    Weighing of Samples, Addition of Buffer plus Amylase & AMG
09:03   Addition of Tris Base and Inactivation of Amylase & AMG
10:12     Incubation with Protease
11:12      A. Determination of HMWDF & LMWSDF
11:16          (i): pH Adjustment & Addition of D-Sorbitol & Ethanol
13:20       (ii): Filtration & Recovery of HMWDF & LMWSDF
17:56       (iii): Ash Determination
18:13       (iv): Protein Determination
19:12        (v): Evaporation of Aqueous Ethanol & Recovery of LMWSDF
21:49      (vi): Desalting of Samples with Ion Exchange Resin
21:16      (vii): Liquid Chromatography of Desalted Samples
27:09    B. Determination of IDF, HMWDF & LMWSDF
29:07        (i): pH Adjustment of the Incubation Mixture and Addition of D-Sorbitol
31:10        (ii): Filtration and Recovery of IDF, HMWDF & LMWSDF
36:02    Calculation of Dietary Fiber Content

Integrated Total Dietary Fiber Assay Kit K-INTDF Scheme
   
Reference code: K-INTDF
SKU: 700004305

100 assays per kit

Content: 100 assays per kit
Shipping Temperature: Ambient
Storage Temperature: Short term stability: 2-8oC,
Long term stability: See individual component labels
Stability: > 2 years under recommended storage conditions
Analyte: Dietary Fiber
Assay Format: Enzymatic
Detection Method: Gravimetric/HPLC
Signal Response: Increase
Limit of Detection: 0.5 g/100 g
Total Assay Time: ~ 3 h work (over 2 days)
Application examples: Food ingredients, food products and other materials.
Method recognition: AACC Method 32-45.01, AACC Method 32-50.01, AOAC Method 2009.01 and AOAC Method 2011.25

The Integrated Total Dietary Fiber test kit is suitable for the measurement and analysis of Integrated Total Dietary Fiber.

Updated to include resistant, branched maltodextrins as a component in dietary fiber.

K-INTDF - An Integrated Procedure (AOAC Method 2009.01 & 2011.25) for the measurement of Total Dietary Fiber (including resistant starch and non-digestible oligosaccharides). This method combines the key attributes of AOAC Official Methods of Analysis 2002.02, 985.29, 991.43, 2001.03.

Specific dietary fiber fractions are measured as follows:

1. Insoluble dietary fiber (IDF), Higher Molecular Weight Soluble Dietary Fiber (SDFP) and Lower Molecular Weight Soluble Dietary Fiber (SDFS) determination (AOAC Method 2011.25)

2. Total High Molecular Weight Dietary Fiber (HMWDF) and SDFS determination (AOAC Method 2009.01)

The enzymes used in these methods are of very high purity; they are effectively devoid of contaminating enzymes active on β-glucan, pectin and arabinoxylan. 

Data calculators are located in the Documents tab.

See our full range of dietary fiber and starch products.

Scheme-K-INTDF INTDF Megazyme

 

Validation of Methods
Advantages
  • The only method that is consistent with the CODEX Alimentarius definition of dietary fiber
  • High purity / standardised enzymes employed 
  • All reagents stable for > 2 years 
  • Mega-Calc™ software tool is available from our website for hassle-free raw data processing
  • Very competitive price (cost per test)
Publications
Megazyme publication

Definition and Analysis of Dietary Fiber in Grain Products.

McCleary, B. V., Cox, J, Ivory, R. & Delaney, E. (2019). “Cereal Grain-based Functional Foods", (Trust Beta and Mary Ellen Camire), CPI Group (UK) Ltd, pp. 103-126.

This chapter discusses the evolution of the definition of dietary fiber and the methodology to service this definition. Cereals are an important source of fiber in the human diet and therefore accurate analyses of the compounds that make up this dietary component are needed. The need to quantify the amount of carbohydrate that affects blood glucose levels led to methods to measure “available” carbohydrates and the recognition of the presence of “unavailable” carbohydrates, although no physiological role was assigned for this latter material. The term dietary fiber was introduced in 1953 and a physiological definition was introduced in 1976. A concerted effort was made to develop a method to service this definition through research. The outcome was the Prosky method (AOAC Method 985.29), which was accepted in 1985 as the gold standard method for the measurement of dietary fiber. As our understanding of the physiological importance of dietary fiber has advanced, it was realized that carbohydrates other than those measured by AOAC Method 985.29, namely resistant starch and non-digestible oligosaccharides, should also be included in the definition and measured and a new definition for dietary fiber was released by Codex Alimentarius. This definition includes resistant starch and the option to include non-digestible oligosaccharides. An integrated total dietary fiber (INTDF) method was developed in 2007 (AOAC Methods 2009.01 and 2011.25) and in 2015 was updated as a rapid integrated total dietary fiber method.

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Megazyme publication

Evolution of a Definition for Dietary Fiber and Methodology to Service this Definition.

McCleary, B. V. & Cox, J. (2017). Luminacoids Research, 21(2), 9-21.

The definition of dietary fiber has been evolving over the past 70 years. The changing definitions reflect our better understanding of the types and physiological functions of dietary fiber. Initial definitions focused on “the remnants of the plant cell walls which are not hydrolyzed by the digestive enzymes of man” and appropriate analytical methods were developed and implemented. More recently, the role of resistant starch and non-digestible oligosaccharides (NDO) as dietary fiber components has been recognized. Incorporation of these has required the development of a host of other methodologies to measure specific dietary fiber components such as fructo-oligosaccharides, galacto-oligosaccharides, resistant maltodextrins, resistant starch and others. Having these specific methods is useful for product manufacturers, but not necessarily for regulators because some of the specific component may also be partially measured by the “gold standard” fiber method, the Prosky method (AOAC Method 985.29). It is thus not possible to simply sum the various specific components with the value obtained with AOAC Method 985.29, as this will lead to “double counting” and thus overestimation of fiber content. To resolve this problem, and allow measurement of all dietary fiber components, an integrated method for measurement of total dietary fiber (AOAC Method 2009.01/AACCI method 32-45.01) was developed and adopted. Evaluation of this method over the past 8 years identified some aspects of the method that could be improved. Modifications have been made and incorporated into a Rapid Integrated Total Dietary Fiber (RINTDF) method, and this method has been subjected to interlaboratory evaluation under the auspices of ICC International and AACC International.

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Megazyme publication
Determination of total dietary fibre and available carbohydrates: A rapid integrated procedure that simulates in vivo digestion.

McCleary, B. V., Sloane, N. & Draga, A. (2015). Starch/Stärke, 67(9-10), 860–883.

The new definition of dietary fibre introduced by Codex Alimentarius in 2008 includes resistant starch and the option to include non-digestible oligosaccharides. Implementation of this definition required new methodology. An integrated total dietary fibre method was evaluated and accepted by AOAC International and AACC International (AOAC Methods 2009.01 and 2011.25; AACC Method 32–45.01 and 32–50.01, and recently adopted by Codex Alimentarius as a Type I Method. However, in application of the method to a diverse range of food samples and particularly food ingredients, some limitations have been identified. One of the ongoing criticisms of this method was that the time of incubation with pancreatic α-amylase/amyloglucosidase mixture was 16 h, whereas the time for food to transit through the human small intestine was likely to be approximately 4 h. In the current work, we use an incubation time of 4 h, and have evaluated incubation conditions that yield resistant starch and dietary values in line with ileostomy results within this time frame. Problems associated with production, hydrolysis and chromatography of various oligosaccharides have been addressed resulting in a more rapid procedure that is directly applicable to all foods and food ingredients currently available.

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Megazyme publication

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.

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Megazyme publication

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.

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Megazyme publication

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.

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Megazyme publication

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.

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Megazyme publication
Development and evaluation of an integrated method for the measurement of total dietary fibre.

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.

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Megazyme publication

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.

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Megazyme publication

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.

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Megazyme publication

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.

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Megazyme publication
Dietary fibre analysis.

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.

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Megazyme publication

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).

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Megazyme publication

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.

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Megazyme publication

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.

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Megazyme publication

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.

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Megazyme publication

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.

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Image mapping of biological changes and structure-function relationship during rice grain development via Synchrotron FTIR spectroscopy.

Ranathunga, A., Thumanu, K., Kiatponglarp, W., Siriwong, S., Wansuksri, R. & Suwannaporn, P. (2023). Food Chemistry Advances, 2, 100290.

The spatial distribution of compositional elements in milky, dough, and mature rice, together with the structure-function relationship was studied using synchrotron-FTIR. The dough stage aleurone and endosperm had high lipid, protein (amide I and II), and hemicellulose. The amylopectin chain length distribution of starch exhibited small differences among developmental stages. Dough starch featured a greater portion of A and B1 chains, implying a more crystalline and high in resistant starch. The protein in milky-to-dough stage aleurone and endosperm had higher contents of α-helixes than β-sheets, resulting in higher protein digestibility and availability. There were high intensities of the glycosidic peaks of hemicellulose and cellulose, pectin, carbohydrates, and β 1–6 glucans in milky-to-dough stages. They corresponded to higher total, insoluble, and soluble dietary fiber contents in milky-to-dough stage than in mature stage. Young-stage rice was found to be more nutritious and could thus be a functional food source.

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Ultrasound-assisted modification of enzyme and antioxidant activities, functional and rheological properties of oat and barley bran.

Grgić, T., Pavišić, Z., Strmečki, N. M., Voučko, B., Mustač, N. Č., Ćurić, D., Le-Bail, A. & Novotni, D. (2023). Research Square, In Press

Oat and barley bran are high in dietary fiber (β-glucans), minerals, and antioxidants, have high activity of enzymes, but possess also antinutrients. This study aimed to investigate the influence of high-intensity ultrasound on enzyme and antioxidant activities, phytic acid content, as well as functional and rheological properties of oat and barley bran. Ultrasonic treatment was performed at 24 kHz on a 15% bran water suspension, at three specific energies (87, 217.5, and 348 kJ/kg), with or without pulsation (5 sec every 10 sec). Bran was assessed for β-glucanase and phytase activity, phytic acid and total phenolic content, antioxidant activity, hydration, and rheological properties. β-glucanase from oat bran was inactivated up to 82% and from barley bran up to 55%, in dependence of ultrasound specific energy and pulsation. In both bran types, phytase activity increased by 40-44% after treatments with 87 kJ/kg but decreased by 89-94% at 348 kJ/kg. Phytic acid was reduced on average in oat bran by 17% and in barley bran by 39%. Depending on the energy and pulsation, the ultrasonication of both bran types reduced total phenolic content (27-55%), antioxidant activity (by 28-48%), complex viscosity (62-71%) and maximum stress tolerated by the sample (46-68%). In contrast, water swelling (42-48%) and water retention capacity (44–59%) increased for both bran types. Hence, high-intensity ultrasound is a useful technique in reducing antinutrients, while altering the enzyme activity and functional properties of the bran. These results could help wider application of bran in food production.

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Characterization of Durum-Wheat Pasta Containing Resistant Starch from Debranched Waxy Rice Starch.

Cervini, M., Gabrielli, M., Spigno, G. & Giuberti, G. (2023). Foods, 12(2), 327.

Durum wheat spaghetti samples prepared with increasing levels of resistant starch (RS) from debranched waxy rice starch (DWRS; i.e., 0, 5, 10, 15 g/100 g w/w) were analyzed for chemical composition, quality and sensory parameters and in vitro starch digestion. All the DWRS-containing spaghetti was “high in fibre”, the dietary fiber content being > 6 g/100 g. In addition, spaghetti with the highest level of DWRS showed the highest RS content (p < 0.05), being 11.4 g/100 g dry matter. The starch hydrolysis index decreased (p < 0.05) as the level of DWRS increased, with a reduction of >20% comparing the 15-DWRS pasta to the control. DWRS had a negative impact on quality parameters, especially at higher DWRS levels. The use of DWRS shortened the optimal cooking time and impacted the samples’ cooking loss, firmness, and stickiness. In addition, sensory analysis revealed differences among samples. However, irrespective of the level of DWRS in the recipe, the score for all attributes was > 5, which is considered the limit of acceptability. Substituting part of the semolina flour with DWRS increased the level of RS and the overall nutritional profile and affected the quality of semolina pasta, mainly at higher levels in the recipe.

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