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.
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).
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.
Enzyme purity and activity in fibre determinations.
McCleary, B. V. (1999). Cereal Foods World, 44, 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.
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.
Two issues in dietary fiber measurement.
McCleary, B. V. (2001). Cereal Foods World, 46(4), 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.
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.
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.
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.
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.
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.
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.
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, L., 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.
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.
The influence of germination conditions on beta-glucan, dietary fibre and phytate during the germination of oats and barley.
Hübner, F., O’Neil, T., Cashman, K. D. & Arendt, E. K. (2010). European Food Research and Technology, 231(1), 27-35.
This study aimed to quantify the changes caused by varying germination conditions on the contents of some bioactive compounds in barley and oats. Samples of the two grains were germinated at temperatures between 10 and 20°C for a period of 2–6 days, using a two-dimensional central composite design. The germination temperature had only minor effect in comparison with the germination time. Slight changes in the mineral content of the malts were observed, mainly caused by steeping. Phytate has been seen as an anti-nutritional compound, as it complexes minerals and lowers their bioavailability. The phytate content in barley malts was considerably lower than in the native kernels. Variations in the germination conditions did not have a significant effect on phytate content. In oats, degradation of phytate was significantly enhanced by prolonging the germination period. It was possible to retain the amounts of soluble dietary fibre, when short germination periods were applied. However, long germination periods caused an extensive breakdown of soluble dietary fibre, especially beta-glucan. The content of insoluble fibre, however, was increased by applying long germination periods for oat malts.
The Choice of Nutritionally Lucrative Flour Streams from Barley Milling Flow.
Velebna, N., Slukova, M., Honcu, I. & Prihoda, J. (2012). Procedia Engineering, 42, 1855-1862.
The scheme of flour milling in mill can be expressed in diagram as a milling flow. There can be described a weight part or percentage of flour from every stage of breaking, scratch and reduction. The similar flow diagram can be drawn expressing the ash content in every of flour streams of a whole milling flow. A milling flow of barley is considerably different from that of wheat and to some part also from rye mill flow. Currently, high-yielding naked barley cultivars are preferred in the Western world, and they can be used in products where outstanding starch or non-starch polysaccharide properties are required. The aim of this work was to assess the milling results with regard to the yield of single streams in connection with their chemical composition, especially β-glucans (fiber) content. Barley sample was naked barley of Czech origin of crop 2010. The balance tables showing the yield of β-glucans and ash in single streams were compiled. Resulting data were judged in comparison to the milling flow with the purpose to recommend the parameters and best streams of milling flow as a source of special nutritionally lucrative products.
Mushrooms of genus Pleurotus as a source of dietary fibres and glucans for food supplements.
Synytsya, A., Míčková, K., Jablonský, I., Sluková, M. & Čopíková, J. (2008). Czech Journal of Food Sciences, 26(6), 441-446.
Fruit bodies (separately pilei and stems) of mushrooms Pleurotus ostreatus (four strains) and Pleurotus eryngii were characterised as a source of polysaccharides. The contents of glucans and dietary fibres were determined with using the respective Megazyme enzymatic kits. Enzymatic analysis of the fruit bodies confirmed significant differences in the contents of these components among the species and strains. The stems contained more insoluble dietary fibres than the pilei in all the cases and more β-glucans in most cases. However, relatively high contents of β-glucan (20–50% of dry matter) could be a result of incomplete enzymatic hydrolysis of insoluble α-1,3-glucans. Nevertheless, low food quality stems of mushrooms Pleurotus sp. could be a valuable source of cell wall glucans for the preparation of food supplements.
Insoluble fiber-rich fractions derived from Averrhoa carambola: hypoglycemic effects determined by in vitro methods.
Chau, C. F., Chen, C. H. & Lin, C. Y. (2004). LWT-Food Science and Technology, 37(3), 331-335.
The hypoglycemic effects of several insoluble fiber-rich fractions (FRFs) including insoluble dietary fiber, alcohol-insoluble solid, and water-insoluble solid isolated from the pomace of Averrhoa carambola were investigated by some in vitro methods. This study evidenced that these three insoluble FRFs could effectively adsorb glucose, retard glucose diffusion, postpone the release of glucose from starch, and inhibit the activity of α-amylase to different extents. All of these mechanisms might create a concerted function in lowering the rate of glucose absorption and as a result decrease the postprandial serum glucose concentration. Our results revealed that the hypoglycemic effects of these insoluble FRFs were significantly (P<0.05) stronger than that of cellulose. Therefore, it was suggested that they could be incorporated as low-calorie bulk ingredients in high-fiber foods to reduce calorie level and help control blood glucose concentration.
Effects of process variables and addition of polydextrose and whey protein isolate on the properties of barley extrudates.
Kirjoranta, S., Solala, K., Suuronen, J. P., Penttilä, P., Peura, M., Serimaa, R., Tenkanen M. & Jouppila, K. (2012). International Journal of Food Science & Technology, 47(6), 1165-1175.
Extrusion cooking is commonly used in the production of snacks. In the present study, extrudates were prepared using barley flour alone and with the addition of either polydextrose (PD) or whey protein isolate (WPI) and both PD and WPI. Independent process variables were water content of the mass (17%, 20% and 23%), screw speed (200, 350 and 500 rpm) and temperature of section 6 and die (110, 130 and 150°C). Expansion, hardness, water content, porosity and chemical composition of the extrudates were analysed. Highly porous and expanded snack products with high dietary fibre and protein contents were obtained from barley flour and WPI when water content of mass was 17%, screw speed 500 rpm and temperature of section 6 and die 130°C. Barley flour alone or with PD resulted in hard and non-expanded extrudates. Expansion of extrudates was statistically significantly increased with decreasing water content of the mass and increasing screw speed in all trials.
Elimination of resistant starch type II within the framework of total starch and dietary fibre analysis by microwave irradiation.
Themeier, H., Hollmann, J., Neese, U. & Lindhauer, M. G. (2010). Quality Assurance and Safety of Crops & Foods, 2(1), 46-51.
Introduction The presence of resistant starch in samples containing non-starch polysaccharides has always been a challenge to enzymatic total starch and total fibre analysis. Objective and methods Based on microwave-induced pressure disintegration technique the Association of Official Analytical Chemists methods for the determination of total starch (AOAC 996.11) and total dietary fibre (AOAC 991.43) have been modified to completely eliminate undesirable resistant starch fractions with respect to digestion procedures using thermostable α-amylase and amyloglucosidase. Results Microwave treatment of high-amylose starch samples resulted in excellent total starch recovery in the Association of Official Analytical Chemists standard method no. 996.11. After integration of microwave disintegration technique into the total dietary fibre method AOAC 911.43 irradiation experiments with different model mixtures consisting of non-starch polysaccharides components and high-amylose starch fractions resulted in the complete elimination of undesirable resistant starch fractions. Conclusion Therefore the microwave technique can be a very efficient means for the elimination of resistant starch and provides more realistic values in analytical total dietary fibre procedures with respect to samples containing critical enzyme resistant starches.
Hypocholesterolemic activity of buckwheat flour is mediated by increasing sterol excretion and down-regulation of intestinal NPC1L1 and ACAT2.
Yang, N., Li, Y. M., Zhang, K., Jiao, R., Ma, K. Y., Zhang, R., Ren G. & Chen, Z. Y. (2014). Journal of Functional Foods, 6, 311-318.
Interest in Tartary buckwheat as a cholesterol-lowering functional food is increasing. The present study was to (i) investigate the relative hypocholesterolemic activity of Tartary buckwheat flour compared with that of wheat and rice flour; and (ii) study the interaction of these three flours with gene expression of sterol transporters and proteins involved in cholesterol absorption. Thirty-six male hamsters were divided into four groups fed either the control or one of three experimental diets containing 24% respective flour, for a period of 6 weeks. Results showed that Tartary buckwheat flour but no wheat and rice flours reduced plasma total cholesterol (TC) and non-high-density lipoprotein cholesterol (non-HDL) as well as hepatic cholesterol concentrations. Compared with that of wheat and rice flours, supplementation of Tartary buckwheat flour into diet led to greater neutral sterol excretion and lesser mRNA of intestinal Niemann-Pick C1 Like 1 (NPC1L1) and acyl-CoA: cholesterol acyltransferase 2 (ACAT2). It was therefore concluded that Tartary buckwheat flour was hypocholesterolemic via inhibition of cholesterol absorption, most likely mediated by down-regulation of intestinal NPC1L1 and ACAT2.
Dietary fibre fractions in cereal foods measured by a new integrated AOAC method.
Hollmann, J., Themeier, H., Neese, U. & Lindhauer, M. G. (2013). Food Chemistry, 140(3), 586-589.
The reliable determination of soluble, insoluble and total dietary fibre in baked goods and cereal flours is an important issue for research, nutritional labelling and marketing. We compared total dietary fibre (TDF) contents of selected cereal based foods determined by AOAC Method 991.43 and the new AOAC Method 2009.01. Fifteen bread and bakery products were included in the study. Our results showed that TDF values of cereal products determined by AOAC Method 2009.01 were always significantly higher than those determined by AOAC Method 991.43. This was explained by the inclusion of low molecular weight soluble fibre fractions and resistant starch fractions in the TDF measurement by AOAC 2009.01. This documents that nutritional labelling of cereal products poses the challenge how to update TDF data in nutrient databases in a reasonable time with an acceptable expenditure.
Wheat bread biofortification with rootlets, a malting by‐product.
Waters, D. M., Kingston, W., Jacob, F., Titze, J., Arendt, E. K. & Zannini, E. (2013). Journal of the Science of Food and Agriculture, 93(10), 2372-2383.
BACKGROUND: Barley rootlets, a malting by-product, are currently discarded or used as fodder. In this study, milled rootlets and Lactobacillus plantarum FST 1.7-fermented rootlets were incorporated into wheat bread. The objective was to formulate a high-nutrition alternative to wholemeal breads with improved technological attributes. RESULTS: Chemical analyses showed that rootlets contribute nutrients and bioactive compounds, including proteins, amino acids, fatty acids, carbohydrates, dietary fibre, polyphenols and minerals. Rootlets are particularly rich in essential amino acids, especially lysine, the typically limiting essential amino acid of cereals. Additionally, rootlets offer potential dietary fibre health benefits such as protection against cardiovascular disease, cancers and digestive disorders. CONCLUSION: Breads prepared with a (fermented) rootlet inclusion level of up to 10% compared favourably with wholemeal breads from nutritive, technological and textural perspectives. Furthermore, they were well accepted by sensory panellists. Using rootlets as a food ingredient would have the added benefit of increasing this malting by-product's market value.
The effect of hazelnut roasted skin from different cultivars on the quality attributes, polyphenol content and texture of fresh egg pasta.
Zeppa, G., Belviso, S., Bertolino, M., Cavallero, M. C., Bello, B. D., Ghirardello, D., Giorgis, M., Grosso, A., Rolle, L., & Gerbi, V. (2015). Journal of the Science of Food and Agriculture, 95(8), 1678-1688.
BACKGROUND: Hazelnut skin is the perisperm of the hazelnut kernel. It is separated from the kernel during the roasting process and is normally discarded. Recent studies have reported that hazelnut skin is a rich source of dietary fibre as well as of natural antioxidants owing to the presence of phenolic compounds. The aim of this study was to assess the use of hazelnut skins obtained from different cultivars for enhancing the nutritional value of fresh egg pasta. RESULTS: Skins obtained from roasted hazelnuts of four different varieties were used at three concentrations as a flour replacement in fresh egg pasta. Hazelnut skin concentration significantly influenced all evaluated physicochemical parameters as well as consumers' appreciation for the pasta, but significant differences were also observed between the four varieties. Although pasta produced with 10 and 15% hazelnut skin displayed the highest content of polyphenolic compounds and antioxidant activity in vitro, pasta containing 5% Tombul hazelnut skin showed maximum consumer preference. CONCLUSION: The results obtained in the present study highlighted that it is possible to use hazelnut skin in fresh pasta production to obtain a fortified food with high fibre content and antioxidant activity. The characteristics of the resulting pasta were strictly correlated with the hazelnut variety used for skin production and, of course, with the percentage of skin that was added.
Assessment of Nutritional Quality of Developed Faba Bean (Vicia faba L.) Lines.
Singh, A. K., Bhardwaj, R. & Singh, I. S. (2014). Journal of AgriSearch, 1(2), 96-101.
Five promising lines of faba bean, which includes two line i.e. 2011215 and 2011410 for grain purpose with yield potential of >5.0t/ha and three promising lines viz., VFBP201302, VFBP201304 and VFBP201306 were identified for vegetable purposes with green pod yield potential of 21.51 to 23.54 t/ha, suitable for Eastern Parts of India.These developed lines were evaluated along with national check varieties viz., Vikrant and Pusa Sumeet for its nutritional and antinutritional quality. Developed lines contain more dietary fiber, total soluble sugar, total starch, phosphorus, iron manganese and zinc. Less phytate was found in the developed lines as compare to checks varieties. Maximum (1.56%) fat was reported in VFBP 201304 (IC No IC No. 0595988), Maximum dietary fiber (13.49%) was obtained in the 2011410 line (IC No.0595986), however, minimum dietary fiber was found in check variety Vikrant (11.94). Similarly, minimum (0.10%) phytate was noticed in the line 2011215 (IC No. 0595985).
Characteristics of destarched corn fiber extrudates for ethanol production.
Myat, L. & Ryu, G. H. (2014). Journal of Cereal Science, 60(2), 289-296.
The effect of extrusion on characteristics of destarched corn fiber was investigated. Extrusion was conducted at a screw speed of 300 rpm, feed rate of 100 g/min, feed moisture content of 30%, melt temperature of 140°C and die diameter of 3 mm. After extrusion, characteristics of raw and extruded destarched corn fiber were compared. Raw and extruded destarched corn fibers were enzymatically saccharified and fermented using Saccharomyces cerevisiae (ATCC 24858). Extrusion pretreatment resulted in low crystallinity index, significant decrease in degree of polymerization and microstructure disruption of destarched corn fiber for enzymatic saccharification. This provides a significant increase in xylose yield for fermentation. Significant increase in protein digestibility and free amino nitrogen were additional benefits of extrusion for yeast nutrient in fermentation. Therefore, extruded destarched corn fiber significantly increased (p < 0.05) ethanol yield (29.08 g/L) and higher conversion (88.79%) by improving the physiochemical and functional properties for saccharification and fermentation.
The effects of bread‐making process factors on Australian sweet lupin‐wheat bread quality characteristics.
Villarino, C. B., Jayasena, V., Coorey, R., Chakrabarti‐Bell, S. & Johnson, S. (2014). International Journal of Food Science & Technology, 49(11), 2373-2381.
Factorial experimental design was used to investigate the effects of: sponge proofing time (min), sponge and dough mixing time (min), final proofing time (min), final proofing temperature (°C) and baking time (min) on Australian sweet lupin-wheat bread physical attributes. Factorial models show that bread specific volume was positively associated with sponge and dough mixing time (P = 0.01) and baking time (P = 0.02). Crumb area was positively associated (P = 0.01) with sponge and dough mixing time. Final proofing time positively influenced cell wall thickness (P < 0.01) and cell diameter (P < 0.01) but negatively affected number of cells (P < 0.01). Cell diameter was positively associated with baking time (P = 0.04), whilst number of cells was negatively influenced by sponge and dough mixing time (P = 0.01). Instrumental springiness was positively associated with sponge and dough mixing time (P = 0.02). Sponge and dough mixing and baking times were the two most significant process parameters affecting the bread physical quality and hence should be optimised.
Effects of fermented and extruded wheat bran on total tract apparent digestibility of nutrients, minerals and energy in growing pigs.
Kraler, M., Schedle, K., Domig, K. J., Heine, D., Michlmayr, H. & Kneifel, W. (2014). Animal Feed Science and Technology, 197, 121-129.
A pig digestibility trial was conducted to investigate the effects of fermentation or extrusion of wheat bran included in a basal diet on coefficients of total tract apparent digestibility (CTTAD) regarding dry matter (DM), organic matter (OM), crude protein (CP), crude fiber (CF), ether extract (EE), starch, energy (GE), phosphorus (P) and calcium (Ca). In the experiment, 9 growing pigs were allocated to a 3 × 3 Latin square design to measure the CTTAD of the basal diet containing different modified wheat bran variants, and therefore to demonstrate relative differences in the CTTAD among the diets as a result of wheat bran modification. The wheat bran was used in native form (NWB), as fermented bran ensiled with Lactobacillus paracasei and Lactobacillus plantarum (FWB) and as extruded wheat bran (EWB). Wheat bran variants were included at 200 g kg-1 in a phosphorus deficient basal diet. The obtained results show that the CTTAD of DM was increased when feeding the diet with FWB (+2%, P<0.05) instead of NWB (0.87). Likewise the CTTAD of OM was also increased with FWB (+2%, P<0.05), compared to NWB (0.88). Also the CTTAD of CF was improved with FWB and EWB (+9%, P<0.05), related to NWB (0.58). The CTTAD of ash was improved with FWB (+14%, P<0.05) compared to NWB (0.60). Correspondingly, the CTTAD values of P and Ca were also elevated when feeding the FWB diet. P-digestibility was increased in the FWB feeding group compared to those groups fed with NWB (+35%, P<0.05) and EWB (+53%, P<0.05). Regarding the Ca digestibility, similar results were obtained (P<0.05). While the CTTAD of energy was increased in the FWB (+3%, P<0.05) and EWB (+2%, P<0.05) feeding groups compared to that of NWB (0.85), the N-balance and the CTTAD of starch were not affected by the treatments. Nevertheless, the CTTAD of EE was enhanced in the FWB treatment group (+40%, P<0.05), and was also improved by extrusion (+30%, P<0.05) compared to the NWB (0.50) treatment. In conclusion, fermented and extruded wheat bran exert some significant influence on the apparent total tact digestibility of several essential nutrients, minerals and energy when included in a basal diet, whereby fermentation seems to be the more potent strategy, as positive effects on the CTTAD of P and Ca could only be observed in the feeding group with FWB.