Determination Of Total Dietary Fiber Research Articles

Differences in the dietary fiber content of fruits and their by-products quantified by conventional and integrated AOAC official methodologies

Accurate determination of total dietary fiber (DF) and its soluble (SDF) and insoluble (IDF) fractions is relevant for food analysis research and nutritional labelling. AOAC integrated DF methodology (AOAC 2011.25, IM) has procedure differences compared to the traditionally used AOAC method (991.43, TM), resulting in different DF quantification. However, IM has been mostly performed for cereal-based products and its application in sources such as fruit products needs to be studied. The aim of this study was to compare the DF content obtained by TM with that achieved using IM in pulps and peels of banana (Musa paradisiaca), mamey sapote (Pouteria sapota), mango (Mangifera indica), Meyer lemon (Citrus meyeri), orange (Citrus sinensis), prickly pear (Opuntia ficus-indica), tamarind (Tamarindus indica), and watermelon (Citrullus lanatus). Samples containing high starch (banana and its peel, mamey sapote and mango pulp) showed higher IDF values when IM was used. Differences were observed when pectinaceous fruits (orange, Meyer lemon, mango and prickly pear) were assayed, since soluble and insoluble pectins are underestimated by TM. Fruits with a high content of non-digestible oligosaccharides showed higher SDF values when assayed by IM. The use of IM in fruits and their by-products provides relevant information about DF fractions and reduces DF underestimations typically observed when assayed by TM.

AACC International Approved Methods Technical Committee Report: Collaborative Study on Determination of Total Dietary Fiber (Digestion-Resistant Carbohydrates per Codex Definition) by a Rapid Enzymatic-Gravimetric Method and Liquid Chromatography

AuthorsBarry V. McCleary, Jodi Cox, and Vincent A. McKie AffiliationsMegazyme, Bray, County Wicklow, Ireland

Rapid Determination of Total Dietary Fiber and Minerals in Coix Seed by Near-Infrared Spectroscopy Technology Based on Variable Selection Methods

The feasibility of near-infrared (NIR) spectroscopy for determining total dietary fiber (TDF) and mineral elements (mainly K, Mg, P, and S) in Coix seed was investigated. Partial least squares regression (PLSR) was applied to establish quantitative models. Norris derivative smoothing (NDS) was used as pretreatment method. A comparison of three variable selection methods, namely competitive adaptive reweighted sampling (CARS), genetic algorithms (GA), and random frog (RF), showed that CARS obtained the best performances of PLSR models with the effective wavelengths mainly concentrated on around 12,000–11,000 cm−1 and 6500–3600 cm−1. For the quantitative determination models of TDF, K, Mg, P, and S, the optimal root mean square error of prediction (RMSEP) values were 0.0923, 182.7224, 75.4987, 162.6993, and 36.6278; the r values were 0.95, 0.88, 0.80, 0.96, and 0.96; the residual predictive deviation (RPD) values were 2.68, 2.05, 1.70, 3.24, and 3.04, respectively. It is concluded that the NIR spectral technique has a potential to determine TDF, K, Mg, P, and S in Coix seed.

Determination of fortified resistant maltodextrin in juices by High performance liquid chromatography

The importance of food fibers has led to the development of a large and potential market for fiber-rich products and ingredients and in recent years. There is a trend to find new sources of dietary fiber that can be used in the food industry. Resistant maltodextrin is a water soluble fiber and short chain polymer of glucose that are resistant to digestion in the human digestive system. As per the AOAC method for determination of total dietary fiber the estimation of low molecular weight resistant maltodextrin involves many tedious steps which make it lengthy & time consuming. Being colorless, tasteless and of low calorific value, resistant maltodextrin qualifies to be a perfect material to used for dietary fiber fortification purposes. Keeping in view the time of analysis, possibility of analytical errors in multiple processing steps & cost of analysis, a simple procedure for determination of resistant maltodextrin has been developed and validate using High performance liquid chromatograph with refractive index detector (HPLC-RID) in fortified fruit juices in 0range citrus Punch. For the confirmation of newly developed analytical method several samples of juices were also analyzed. The method given specifically measures resistant maltodextrin.

The non–starch polysaccharides quantity changes in pastry products where Jerusalem artichoke (Helianthus tuberosus L.) added

Non-starch polysaccharides (NSP) constitute the main part of dietary fiber (DF). There are two kinds of NSP - insoluble and soluble. Most plant foods contain both types although proportions vary. A good source of NSP/fiber is Jerusalem artichoke (Helianthus tuberosus L.), vegetable - rich in fiber, vitamins and minerals. Jerusalem artichoke (JA) is used for managing cholesterol, lipids in the blood, can also help with weight control, not through better metabolism of fats but through better management of sugars. The addition of Jerusalem artichoke powder (JAP) increases the fiber content of the pastry products, making it a healthier food. Several methods are available for the determination of total dietary fiber in products. The Uppsala method is the most appropriate when information of the DF components is required. Since different DF components have a range of beneficial effects on human health this approach of analyzing DF should become more widely used when characterizing foods. The aim of the study was to determine quantity changes in individual NSP of DF in raw material JAP and such pastry products as cakes, butter biscuits and honey biscuits where JAP was added. The study identified quantity and types of NSP in JAP and pastry products with JAP in concentration 30% and 50% of total amount of flour, but as control are samples without JAP. Results showed that the major NSP monomers of all pastry kinds are, in decreasing manner, glucose, galactose, mannose, arabinose, xylose, rhamnose, and fucose. Additionally, NSP content increases substantially with increasing concentration of JAP in cakes, honey biscuits and butter biscuits.

Determination of Total Dietary Fiber (CODEX Definition) by Enzymatic-Gravimetric Method and Liquid Chromatography: Collaborative Study

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 Methods 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 degrees 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 > or =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 (S(R)) 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 Total Dietary Fiber in Selected Foods Containing Resistant Maltodextrin by a Simplified Enzymatic-Gravimetric Method and Liquid Chromatography: Interlaboratory Study in China

An interlaboratory study was conducted in China to validate the modified AOAC Official Method 2001.03 for the determination of total dietary fiber (TDF) in foods containing resistant maltodextrin (RMD), which will be adopted as the National Standard Method of China. The kind of buffer solution, the volume of filtrate evaporation, the volume of eluent for desalting and residual solution after evaporation, etc. were modified, which had been proved to have acceptable accuracy and precision in the routine assay. TDF contents in 3 representative foods and 2 kinds of RMD ingredient (i.e., NUTRIOSE 06 and NUTRIOSE 10) were measured using the modified method in 6 eligible laboratories representing commercial, industrial, and governmental laboratories in China. The results of the interlaboratory study indicated that the intralaboratory repeatability, interlaboratory reproducibility, and precision of the modified method are adequate for reliable analysis of TDF in food containing RMD, as well as resistant dextrin. Compared to AOAC Official Method 2001.03, the modified method is time- and cost-saving.

A Simplified Modification of the AOAC Official Method for Determination of Total Dietary Fiber Using Newly Developed Enzymes

Since 1985, AOAC Method 985.29 has been globally adopted as a standard method for determination of total dietary fiber in foods. Nevertheless, an aspect of AOAC Method 985.29 that needs to be improved is the laborious process to treat 3 enzymes separately at their individual proper pH, which is quite time-consuming. Several examinations have been carried out to resolve this problem. The characteristics of newly developed thermostable alpha-amylase, neutral protease, and amyloglucosidase were evaluated based on the pH-activity profile and the property of starch hydrolysis in comparison with those of the conventional enzyme reagents. These 3 developed enzymes were found to work under the same pH condition and to accomplish sufficient digestion for the typical 3 starches: soluble starch, corn starch, and wheat starch. The experimental results revealed that the dietary fiber determination in foods could be performed without pH adjustment in the enzymatic digestion process. The modified method will be greatly helpful in determining the total dietary fiber contents in food materials with less laborious work and with an accuracy equivalent to that of AOAC Method 985.29.

A Simplified Modification of the AOAC Official Method for Determination of Total Dietary Fiber Using Newly Developed Enzymes: Preliminary Interlaboratory Study

A preliminary interlaboratory study was conducted to evaluate the validity of the modified AOAC method for determination of total dietary fiber by Tada and Innami, in which the 3-step enzymatic digestion process in AOAC Method 991.43 is modified to a 2-step process without pH adjustment. Total dietary fiber contents in 8 representative foodstuffs were measured using both the original AOAC Method 991.43 and the modified method in 6 research facilities in Japan. Repeatability relative standard deviations, reproducibility relative standard deviations, and Horwitz ratio values from the modified method were equivalent to those from AOAC Method 991.43, except in the rice sample. However, this exceptional case shown in the modified method was entirely dissolved by the addition of alpha-amylase stabilizing agents. The modified method, which shortens the process of enzymatic digestion from 3 to 2 steps and in which only reaction temperature is adjusted under the same pH, was found not only to give accurate values comparable to the original method, but also to substantially reduce the labor required by the laboratory staff in the process of routine analysis. This study revealed that the validity of the modified method was further ensured by adding alpha-amylase stabilizing agents to the reaction system.

Determination of Total Dietary Fiber in Selected Foods Containing Resistant Maltodextrin by Enzymatic-Gravimetric Method and Liquid Chromatography: Collaborative Study

A method was developed for determination of total dietary fiber (TDF) in foods containing resistant maltodextrin (RMD) which includes nondigestible carbohydrates that are not fully recovered as dietary fiber by conventional TDF methods such as AOAC 985.29 or 991.43. Because the average molecular weight (MW) of RMD is 2000 daltons, lower MW soluble dietary fiber components do not precipitate in 78% ethanol; therefore, RMD is not completely quantitated as dietary fiber by current AOAC methods. The accuracy and precision of the method was evaluated through an AOAC collaborative study. Ten laboratories participated and assayed 12 test portions (6 blind duplicates) containing RMD. The 6 test pairs ranged from 1.5 to 100% RMD. The method consisted of the following steps: (1) The insoluble dietary fiber (IDF) and high MW soluble dietary fiber (HMWSDF) were determined by AOAC 985.29. (2) Ion exchange resins were used to remove salts and proteins contained in the AOAC 985.29 filtrates (including ethanol and acetone). (3) The amount of low MWRMD (LMWRMD) in the filtrates were determined by liquid chromatography. (4) The TDF was calculated by summation of the IDF, HMWSDF, and LMWRMD fractions having nondigestible carbohydrates with a degree of polymerization of 3 and higher. Repeatability standard deviations (RSDr) were 1.33-7.46%, calculated by including outliers, and 1.33-6.10%, calculated by not including outliers. Reproducibility standard deviations (RSDR) were 2.48-9.39%, calculated by including outliers, and 1.79-9.39%, calculated by not including outliers. This method is recommended for adoption as Official First Action.

Determination of total dietary fiber of intact cereal food products by near-infrared reflectance.

Near-infrared reflectance spectra of cereal food products were acquired with a commercial dual-diode-array (Si, InGaAs) spectrometer customized to allow rapid acquisition of scans of intact breakfast cereals, snack foods, whole grains, and milled products. Substantial gains in the performance of multivariate calibration models generated from these data were obtained by a computational strategy that systematically analyzed the performance of various spectral windows. The calibration model based on 137 cereal food products determined the total dietary fiber (TDF) content of a test set of 45 intact diverse cereal food products with root-mean-squared error of cross-validation of between 1.8 and 2.0% TDF, relative to the laborious enzymatic-gravimetric reference method. The calibration performance is adequate to estimate TDF over the range of values found in diverse types of cereal food products (0.7-50.1%). The method requires no sample preparation and is relatively unaffected by specimen moisture content.

Variability for Starch Digestibility in Dry Bean (Phaseolus vulgaris L.)

Undigested starch is a major contributor to gastrointestinal discomfort experienced from eating cooked dry beans (Phaseolus vulgaris L.). Plant breeders are interested in identifying genetic stocks of beans with highly digestible starch to use in food quality improvement programs. Before a selection program for starch digestibility can be initiated, genetic variability must be ascertained. Breeding lines and cultivars from several dry bean market classes were evaluated for their starch digestibility using a laboratory procedure involving the determination of total dietary fiber with 3-enzymes. Grinding raw and cooked beans using a mill with the same-size screen (either 40 or 60 mesh) resulted in larger particles in the raw than in the cooked bean sample and inflated the amount of indigestible starch in the raw bean samples. In an experiment in which cooked and raw beans were ground with different size sieves, we found that in order to obtain cooked and raw beans with comparable particle sizes (thus providing accuracy and reliability to indigestible starch determinations), the cooked beans should be ground and sieved through a 40-mesh screen, and raw beans through a 60-mesh screen. Navy bean was the market class with the most digestible starch (≈10%). Black beans and kidney bean had the least digestible—starch >15%. Manteca, a Latin American market class with a pale yellow seed coat, was similar in digestibility to navy beans. Although the evidence is anecdotal, Manteca beans are favored for their qualities of taste, texture, and good digestibility. The current research on indigestible starch appears to confirm the high digestibility, low-flatulence attributes of Manteca bean.

Prediction of Total Dietary Fiber by Near-Infrared Reflectance Spectroscopy in High-Fat- and High-Sugar-Containing Cereal Products

The near-infrared (NIR) spectral properties of cereal products containing high fat or high sugar can differ substantially from the spectral properties of other cereal products. An existing NIR model, using preprocessed reflectance spectra and partial least-squares analysis, for the prediction of total dietary fiber in cereal products was expanded to two new models called (1) the “fat-expanded” model and (2) the “fat- and sugar-expanded” model. The fat-expanded model enlarges the existing model with high-fat-content products as calibration samples, and the “fat- and sugar- expanded” model also includes products with high sugar and high crystalline sugar content. The dry milled cereal and grain products were analyzed in the laboratory according to AOAC method 991.43 for the determination of total dietary fiber, and NIR reflectance spectra were collected with a scanning monochromator. Data analysis and selection of representative high-fat and high-sugar samples were performed with a commercial analysis program. The two expanded models had standard errors of cross-validation and R2 similar to those of the existing model, with acceptable standard error of performance and r2 when tested with independent validation samples. The existing model was, thus, expanded to include high-fat, high-sugar, and high crystalline sugar cereal products while maintaining prediction accuracy. Keywords: Dietary fiber; near-infrared; chemometrics; cereal

Raman and NIR Spectroscopic Methods for Determination of Total Dietary Fiber in Cereal Foods: A Comparative Study

Partial least-squares regression (PLSR) was used to generate three Raman and three near-infrared reflectance (NIRR) models for the spectroscopic determination of total dietary fiber (TDF) of a wide variety of cereal foods. To allow comparison of the spectral techniques, both analyses used the same sets of samples ( ncal = 63, nval = 63). Six models were optimized by full leave-one-out cross-validation (CV), including a smoothed, a first-, and a second-derivative model for each spectral technique. Both kinds of raw spectral data required correction of interfering baseline and amplitude variations. Derivative preprocessing generally reduced the number of latent variables (LVs) for both spectral types and significantly reduced the CV error of the Raman models. The derivative treatments enhanced the influence of select vibrational-bandwidth-sized features in the Raman data (64–84 cm−1). The Savitzky–Golay derivative calculation method was better for the NIRR data, while the gap-difference method was better for the Raman data, which had a higher level of baseline noise. Raman models required 6 to 9 latent variables while NIRR models required 10 to 14 LVs. The root-mean-squared CV model errors were 2–2.3% TDF for all six models, and the three Raman models had root-mean-squared prediction errors (RMSEPs) in the range 2.8–3.2% TDF, with the best model being generated from second-derivative data. First-derivative data provided the best NIRR model, and for all three NIRR models the RMSEP spanned 2.4–2.9%. For some types of samples, it is suggested that the Raman method is limited by its sampling technique and could be improved with more densely packed, larger-area specimens. The regression vectors of the Raman models seem more easily interpretable than NIRR models. Either spectral method appears capable of acheiving an acceptable level of error; TDF reference method precision was 0.68% TDF, while the product label information had an error of 2.8% TDF relative to the reference.

Raman and NIR Spectroscopic Methods for Determination of Total Dietary Fiber in Cereal Foods: Utilizing Model Differences

This work evaluates the complementarity in the predictive ability of three Raman and three near-infrared reflectance (NIRR) partial least-squares regression (PLSR) models for total dietary fiber (TDF) determinations of a diverse set of ground cereal food products. For each spectral type (R or N), models had previously been developed from smoothed (D0), first-derivative (D1), or second-derivative (D2) spectral data. The NIRR and Raman models tend to have very different sets of outliers and uncorrelated errors in TDF determination. For a single spectral type, the prediction errors of various preprocessing methods are partially complementary. The samples are very diverse in terms of composition, but the main problem groups were narrowed to high-fat, high-bran, and high-germ samples, as well as and those containing synthetic fiber additives. Raman models perform better on the high-fat samples, while NIRR models perform better with high-bran and high-synthetic samples. Raman models were better able to accommodate a wheat germ sample, even though this sample type was poorly represented by the calibration set. Two methods are presented for utilizing the complementarity of the spectral and processing techniques: one involves simple averaging of predictions and the other involves avoidance of outliers by using statistics generated from the sample spectrum to choose the best model(s) for determination of the TDF value. The single best model (N-D1) has a root-mean-squared prediction error of 2.4% TDF. The best model of prediction averages yields an error of 1.9% (combining N-D0, N-D1, N-D2, R-D0, and R-D1). An error of 1.9% was also obtained by choosing a single prediction from the six models by using statistics to avoid outliers. With the selection of the best three models and averaging their predictions, an error of 1.5% was achieved.

Determination of Total Dietary Fiber in Foods and Food Products by Using a Single-Enzyme, Enzymatic-Gravimetric Method: Interlaboratory Study

A simplified enzymatic-gravimetric method for total dietary fiber (TDF) determination has been published and used in the Food Composition Laboratory of the U.S. Department of Agriculture since 1988. THis method gives comparable results to AOAC Official Methods 985.29 and 991.43 but the AOAC methods use 100 degrees C (water bath) to gelatinize the sample and a combination of alpha-amylase and an amyloglucosidase to hydrolyze starches, whereas the simplified method incorporates an autoclaving step (121 degrees C) for gelatinization followed by incubation with only amyloglucosidase. The simplified method omits protease hydrolysis and does not require any pH adjustment. Overall, the simplified method cuts cost and is less labor intensive. An interlaboratory study was conducted to validate this method. Blind duplicates of six sample (baked beans, corn bran, roasted peanuts, cooked potatoes, white bread with reduced calories, and cooked white rice) were sent to 11 laboratories. The reproducibility relative standard deviations of the TDF values (without outliers) ranged from 3.46 to 27.6%. The repeatability standard deviations ranged from 0.91 to 14.6%.

Total Dietary Fiber Determined as Neutral Sugar Residues, Uronic Acid Residues, and Klason Lignin (The Uppsala Method): Collaborative Study

A joint AOAC/American Association of Cereal Chemists (AACC) collaborative study was conducted to determine by the Uppsala method the dietary fiber content and its composition in various foods. The method includes preparation of a residue by treatment with thermostable alpha-amylase and amyloglucosidase and then ethanol precipitation of solubilized dietary fiber components while leaving low-molecular weight carbohydrates in solution. After acid hydrolysis of residue, neutral polysaccharide residues are determined as alditol acetates by gas-liquid chromatography, uronic acid residues are determined by colorimetry, and ash-free acid-insoluble residue (Klason lignin) is determined gravimetrically. Total dietary fiber, including enzyme-resistant starch, is calculated as the sum of nonstarch polysaccharide residues and Klason lignin. Nine laboratories completed the study, analyzing in duplicate 8 unknown dried products that included 4 cereal products, green peas, potato fiber, carrots, and apples. Total dietary fiber contents of products tested ranged from 4.6 to 84.3%, with an average RSDR value of 8.4% (range, 4.8-11.1%). Total neutral polysaccharide residues ranged from 3.8 to 64.1%, with an average RSDR value of 7.5% (range, 5.4-10.5%). Individual neutral sugars (rhamnose, arabinose, xylose, mannose, galactose, and glucose) and uronic acid residues present at more than 1% generally had good RSDR values (3.3-22.8%), whereas, as expected for Klason lignin, only the wheat bran sample with a high content (16%) had an excellent RSDR value (5.0%). The gas chromatographic-colorimetric-gravimetric method (Uppsala method) for determination of total dietary fiber (as neutral sugar residues, uronic acid residues, and Klason lignin) has been adopted first action by AOAC INTERNATIONAL.

Determination of Total Dietary Fiber in Foods and Products with Little or No Starch, Nonenzymatic-Gravimetric Method: Collaborative Study

A collaborative study was conducted to validate a nonenzymatic-gravimetric method for the determination of total dietary fiber (TDF) of samples containing little or no starch such as most fruits, and vegetables and many purified polysaccharides. This simple procedure involves suspension of freeze-dried, ground samples in deionized water and incubation at 37 degrees C for 90 min, followed by precipitation with 4 volumes of 95% ethanol. The weight of the dilute alcohol-insoluble residues after correcting for crude protein and ash corresponds to the TDF content of the sample. Six samples in blind duplicate (apples, apricots, cabbage, carrots, onions, and soy fiber) were sent with Celite to 10 laboratories. The reproducibility relative standard deviation (RSDR) of the TDF values for 9 laboratories ranged from 2.92 to 6.25%. The repeatability standard deviation (RSDr) for the 9 laboratories ranged from 1.50 to 2.70%. The method has been adopted first action by AOAC INTERNATIONAL.

Enzymatic-Gravimetric Determination in Foods of Dietary Fiber as Sum of Insoluble and Soluble Fiber Fractions: Summary of Collaborative Study

A collaborative study was conducted on an enzymatic-gravimetric method for determination of total dietary fiber in foods, in which soluble fiber and insoluble fiber are determined separately. Ten collaborators analyzed blind duplicate test samples from 5 food products: turnip, wheat bran, beans canned with tomato sauce, rice, and whole wheat bread. Repeatability and reproducibility relative standard deviations ranged from 1.48 to 14.73% and from 4.13 to 17.94%, respectively. The method was adopted first action by AOAC International.

Nonenzymatic-Gravimetric Determination of Total Dietary Fiber in Fruits and Vegetables

Abstract Most gravimetric methods for total dietary fiber (TDF) determination require the complete removal of starch and the partial removal of protein with various combination of enzymes In buffers at different pH values and at temperatures much above ambient condition. A hydrolysis step Is crucial In dietary fiber analysis of samples, such as cereals and legumes, which contain appreciable amounts of starch. However, many vegetables and most fruits contain very little or no starch, and they are often eaten uncooked. It would be unnecessary to use high temperatures and enzymes on these types of samples. Initially, we found that hexane and dilute alcohol extractions of a few selected fruits and vegetables gave residue weights comparable to those after enzymatic treatments. We were able to show later that simply suspending the samples in delonized water for 90 mln at 37°C and then adding 95% ethanol also yields TDF values similar to those obtained from other published methods. Comparison data obtained by using variations of the AOAC/TDF method are presented for 10 fruits and vegetables.