Near-infrared analysis of soluble and insoluble dietary fiber fractions of cereal food products

The use of near-infrared (NIR) reflectance spectroscopy for the rapid and accurate measurement of soluble and insoluble dietary fiber was explored in a diverse group of cereal products. Ground samples were analyzed for soluble and insoluble dietary fiber (AOAC Method 991.43) and scanned (NIRSystems 6500 monochromator) to obtain NIR spectra. Modified PLS models were developed to predict insoluble and soluble dietary fiber using data sets expanded to include products with high fat and high sugar contents. The models predicted insoluble dietary fiber accurately with an SECV of 1.54% and an R(2) of 0.98 (AOAC determined range of 0-48.77%) and soluble dietary fiber less accurately with an SECV of 1.15% and an R(2) of 0.82 (AOAC determined range of 0-13.84%). Prediction of independent validation samples by the soluble fiber model resulted in a bias that may be related to the way the reference method treats samples with different soluble fiber constituents. The insoluble fiber model can be used to rapidly monitor insoluble dietary fiber in cereal products for nutrition labeling.     

Fagopyritols, D-chiro-inositol, and other soluble carbohydrates in buckwheat seed milling fractions

Fagopyritols are mono-, di-, and trigalactosyl derivatives of D-chiro-inositol that accumulate in seeds of common buckwheat (Fagopyrum esculentum Moench) and may be important for seed maturation and as a dietary supplement. Fagopyritols and other soluble carbohydrates were assayed in mature groats and 11 milling fractions of common buckwheat seed. Because fagopyritols are in embryo and aleurone tissues, differences in fagopyritol concentrations reflect varying proportions of these tissues in each milling fraction. Bran milling fractions contained 6.4 g of total soluble carbohydrates per 100 g of dry weight, 55% of which was sucrose and 40% fagopyritols. Flour milling fractions had reduced fagopyritol concentration [0.7 g/100 g of dry weight total fagopyritols in the dark (Supreme) flour and 0.3 g/100 g in the light (Fancy) flours]. Fagopyritol B1 was 70% of total fagopyritols in all milling fractions. Fagopyritols were 40% of total soluble carbohydrates in groats of two cultivars of common buckwheat but 21% in groats of tartary buckwheat [Fagopyrum tataricum (L.) Gaertn.], probably a reflection of environment and genetics. A rhamnoglucoside present in tartary buckwheat was not detected in common buckwheat.     

Effect of fermentation and autoclaving on dietary fiber fractions and antinutritional factors of beans (Phaseolus vulgaris L.)

The effect of fermentation on antinutritional factors and also on total dietary fiber (TDF), insoluble (IDF) and soluble (SDF) dietary fiber fractions was studied in beans (Phaseolus vulgaris L.). The processes studied were two types of fermentation (lactic acid and natural), and a portion of the obtained flours were processed by autoclaving. The dietary fiber (DF) content and its components were determined using the enzymatic-gravimetric and enzymatic-chemical methods. The TDF content ranged from 24.5% dry matter (DM) in the raw to 25.2% DM in the processed beans. All the processing treatments significantly decreased the SDF content, and irrelevant changes were noticed in the IDF content of processed beans. Cellulose content of all samples was reduced by the processing treatments. Correspondingly, higher amounts of resistant starch was observed in the processed beans, except in the lactic acid fermented ones. However, the levels of pectic polysaccharides and Klason lignin were higher in the samples fermented by Lactobacillus plantarum. The action of microorganisms was determinant for the different degradation of the bean cell wall, disrupting the protein-carbohydrate integration, thus reducing the solubility of DF.     

提高大豆渣膳食纤维中可溶性成分的方法研究

以大豆渣为原料,采用微生物发酵、微射流均质机高压均质处理和高温蒸煮的方法来提高大豆膳食纤维中可溶性成分含量,研究不同发酵时间、不同处理压力和蒸煮温度以及蒸煮时间对提高豆渣可溶性膳食纤维（SDF）含量的影响。结果表明：利用发酵法可提高可溶性膳食纤维的含量达15%之多,并且在发酵的前6天,SDF含量增长很快,6 d后SDF的含量变化较少;而高压均质处理法提高可溶性膳食纤维含量的幅度在10%～28%之间,并随着处理压力的升高而增大;高温蒸煮法能提高可溶性膳食纤维的含量20%,121℃,20 min为较理想的蒸煮条件。     

Effect of industrial processing on the distribution of aflatoxins and zearalenone in corn-milling fractions

The aim of this study was to investigate the distribution of aflatoxins and zearalenone levels in various corn-milling fractions. Corn kernels and six derived milling fractions (germ, bran, large and small grits, flour, and animal feed flour) were sampled in an industrial plant; both conventional and organic corns were sampled. To evaluate the effect of cooking, samples of polenta were prepared starting from naturally contaminated flour. Conventional and organic lots showed mycotoxin contamination. For both lots, germ, bran, and animal feed flour showed a marked concentration factor from 239 to 911% accounting for both the low yields of the derived products and the distribution of aflatoxins and zearalenone contamination in the outer parts of the kernels. Conversely, a reduction factor of at least four times from raw material to finished products was observed. Polenta samples were unaffected by the cooking process, with levels of contamination similar to those of starting flour.     

挤压豆渣中可溶性膳食纤维制备工艺的优化

为了获得碱法制备挤压豆渣中可溶性膳食纤维的最适工艺参数,以液固比、温度、时间和碱浓度为试验因子,以可溶性膳食纤维产率为响应值,采用中心旋转组合试验设计进行试验。结果表明：4个因素对可溶性膳食纤维产率的影响大小依次为碱浓度＞液固比＞温度＞时间。通过典型性分析得出可溶性膳食纤维最适制备条件为：液固比26∶1、温度89℃、时间68 min、碱浓度1.12%。在此条件下,可溶性膳食纤维产率的预测值为33.96%,验证试验所得可溶性膳食纤维产率为34.12%。回归方程的预测值和试验值差异不显著,所得回归模型拟合情况良好,达到设计要求。在本试验优化的条件下,以经挤压豆渣为原料制备的可溶性膳食纤维产率（34.12%）显著高于以未经挤压豆渣为原料的产率（13.51%）。     

超滤膜分离纯化花生壳中水溶性膳食纤维

为探索花生壳中水溶性膳食纤维(SDF)的有效分离纯化方法和效果,选择适宜的膜组件,采用不同截留分子量的超滤膜以及优化膜分离过程的操作条件,对SDF提取液进行超滤分离,试验结果表明:选用PS-30聚砜膜,在压力为0.08MPa、料液比为1:75g/mL、温度为30℃时,分离纯化效果最为显著。其中,膜通量达到127.2L/(m2·h)、SDF的得率达到67.56%,非淀粉多糖(NSP)的质量分数由49.85%提高到92.36%,蛋白质量分数从5.53%降到0.92%。与传统的提取法比较,超滤膜分离纯化花生壳水溶性膳食纤维具有生产周期短,成本低,产品纯度高等优点。     

Determination of insoluble, soluble, and total dietary fiber in foods and food products: interlaboratory study

A collaborative study was conducted to determine the insoluble dietary fiber (IDF), soluble dietary fiber (SDF), and total dietary fiber (TDF) content of food and food products by using a combination of enzymatic and gravimetric procedures. The method was basically the same as that developed for TDF only, which was adopted official final action by AOAC, except for changing the concentration of buffer and base and substituting hydrochloric acid for phosphoric acid. These changes were made to improve the robustness of the method. Duplicate blind samples of soy isolate, white wheat flour, rye bread, potatoes, rice, corn bran, oats, Fabulous Fiber, wheat bran, and a high fiber cereal were analyzed by 13 collaborators. Dietary fiber values (IDF, SDF, and TDF) were calculated as the weight of residue minus the weight of protein and ash. The coefficients of variation (CVs) of both the independent TDF determination and the sum of IDF and SDF were better than 15 and 18%, respectively, with the exception of rice and soy isolate. These 2 foods, however, contained only about 1% TDF. The CVs of the IDF were equally good, except for Fabulous Fiber, for which filtration problems occurred. The CVs for the SDF were somewhat high, but these products had very low SDF content. There was excellent agreement between the TDF determined independently and the TDF determined by summing the IDF and SDF. The method for separate determination of IDF and SDF requires further study. The modifications (changes in concentration of buffer and base and the use of hydrochloric acid instead of phosphoric acid) to the official final action method for TDF have been adopted.     

Effects of heat treatment and dehydration on properties of cauliflower fiber

The effects of heat treatment and dehydration on fiber structure and hydration properties, using cauliflower floret/curd and stem tissues, have been investigated. No major changes in fiber composition resulted from sample treatments, but the degree of esterification of pectic polysaccharides, approximately 60% in fresh cauliflower, decreased by approximately 12% in samples heated at temperatures >40 degrees C. Enzymic activity was considered to be responsible, through pectin methyl esterase activity. De-esterification was temperature and moisture sensitive. Hydration properties were also affected by processing conditions. The solubility of nonstarch polysaccharides in fresh, freeze-dried, and 40 degrees C dried samples was approximately 6% but increased to 12% in boiled samples and decreased in samples dried at 75 degrees C. Similar behavior occurred for swelling and water retention capacity (WRC), with swelling and WRC highest for boiled samples and lowest for samples dried at 75 degrees C. Hence, a decrease in de-esterification was not directly responsible for changes in hydration properties. The results demonstrate the importance of processing history on functional properties and on the preparation of fiber-rich ingredients for successful incorporation into foods.     

亚临界水提法提高甘薯皮可溶性膳食纤维得率

为了提高甘薯加工副产物的利用率,以浙薯13品种甘薯皮为原料,采用亚临界水提取甘薯皮可溶性膳食纤维。在单因素试验的基础上选取料液比、提取温度、提取时间3个因素,应用正交试验对甘薯皮可溶性膳食纤维提取工艺条件进行优化,考察可溶性膳食纤维的物化性质,并以葡萄糖吸附能力、羟基自由基清除能力、DPPH自由基清除能力为指标,评价甘薯皮可溶性膳食纤维功能特性。结果表明,亚临界水提取甘薯皮可溶性膳食纤维得率为10.43%,比无辅助热水、超声和微波辅助提取法分别提高769.17%、27.04%和34.75%。亚临界水提取法中可溶性膳食纤维占总膳食纤维的比例最高（42.26%）,比无辅助热水、超声和微波提取条件下分别提高665.58%、14.43%和19.24%。亚临界水法提取所得可溶性膳食纤维的葡萄糖吸附能力（4.79 mmol/g）、羟基自由基清除能力（54.28%）和DPPH自由基清除能力（69.28%）均高于无辅助热水、超声和微波辅助提取法所得可溶性膳食纤维,总膳食纤维的吸水膨胀性（7.89 mL/g）、持油性（4.74 g/g）和峰值黏度（27.18 mPa/s）显著高于其他方法所提取的总膳食纤维。     

Effect of heat treatment of dietary fiber: interlaboratory study

The effects of thermal treatments on the dietary fiber composition of cereal and potato samples were studied at 8 laboratories using different analytical methods. Thermal treatments included extrusion cooking for cereals, and boiling and frying for potatoes. No changes in the amounts of dietary fiber or starch were observed in the extruded samples. Heat-treated potato samples contained significantly more water-insoluble dietary fiber (cellulose) and less starch than did raw potato. However, this may be due, at least in part, to the sample preparation procedure rather than the heat treatment alone. The study indicates that gravimetric and sequential hydrolysis methods give similar results, but the variation in most cases is still wide. Further standardization of methods is evidently needed, especially if legislative measures for setting limits on the fiber content of foods are to be introduced. Standardization of starch analysis should also be of primary importance in future work on carbohydrate methodology. This can be concluded from the variation in results concerning this extremely important food constituent. It should be noted that the sample matrix in the present study was simpler than that of complex meals or diets.     

Treatment of cereal products with a tailored preparation of trichoderma enzymes increases the amount of soluble dietary fiber

Nutritionists recommend increasing the intake of soluble dietary fiber (SDF), which is very low in most cereal-based products. Conversion of insoluble DF (IDF) into SDF can be achieved by chemical treatments, but this affects the sensorial properties of the products. In this study, the possibility of getting a substantial increase of SDF from cereal products using a tailored preparation of Trichoderma enzymes is reported. Enzymes were produced cultivating Trichoderma using durum wheat fiber (DWF) and barley spent grain (BSG) as unique carbon sources. Many Trichoderma strains were screened, and the hydrolysis conditions able to increase by enzymatic treatment the amount of SDF in DWF and BSG were determined. Results demonstrate in both products that it is possible to triple the amount of SDF without a marked decrease of total DF. The enzymatic treatment also causes the release of hydroxycinnamic acids, mainly ferulic acid, that are linked to the polysaccharides chains. This increases the free phenolic concentration, the water-soluble antioxidant activity, and, in turn, the phenol compounds bioavailability.     

Effect of germination on the carbohydrate composition of the dietary fiber of peas (Pisum sativum L.)

The effect of different conditions of pea germination on dietary fiber (DF) composition was studied. Insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) were subjected to acid hydrolysis, and the resultant neutral sugars, uronic acids, and Klason lignin were quantified. Germinated peas exhibited significantly higher contents of total dietary fiber (TDF) than the raw sample, due to the increases of both DF fractions. Under darkness conditions, germination exhibited the highest contents of IDF and SDF. Decreasing IDF/SDF ratios showed that the carbohydrate changes did not take place to the same extent during germination, the SDF fraction being the most affected. The detailed chemical composition of fiber fractions reveals increases of cellulose in the IDF of germinated samples, whereas SDF exhibits a decrease of pectic polysaccharides and also increases of polysaccharides rich in glucose and mannose. The DF results were corroborated by a comparative examination of the cell wall carbohydrate composition.     

HPLC detection of soluble carbohydrates involved in mannitol and trehalose metabolism in the edible mushroom Agaricus bisporus

A convenient and sensitive method was developed to separate and detect various types of carbohydrates (polyols, mono- and disaccharides, and phosphorylated sugars) simultaneously using high-performance liquid chromatography (HPLC). The method consists of a chromatographic separation on a CarboPac PA1 anion-exchange analytical column followed by pulsed amperometric detection. In a single run (43 min) 13 carbohydrates were readily resolved. Calibration plots were linear over the ranges of 5-25 microM to 1. 0-1.5 mM. The reliable and fast analysis technique, avoiding derivatization steps and long run times, was used to determine the levels of carbohydrates involved in mannitol and trehalose metabolism in the edible mushroom Agaricus bisporus. Moreover, the method was used to study the trehalose phosphorylase reaction.     

Effect of seasonal changes on content and profile of soluble carbohydrates in tubers of different varieties of Jerusalem artichoke (Helianthus tuberosus L.)

A high content (60-65% of dry mass DM) of water soluble carbohydrates was found in early harvested varieties (Bella and Bianka) and middle early varieties (Topstar and Gigant) harvested 22-25 weeks after plantation. In late varieties (Waldspindel, Violet de Rennes, Rote Zonenkugel) a similar amount was obtained (55-60% of DM) when harvested 29-33 weeks after planting. There was a distinctive impact on maturing process as well as frost period alterations which resulted in conversion of high polymer inulin to low polymer inulin as well as to sucrose. In early/middle early varieties a correlation between sucrose and inulin level (r = - 0.952**) with a linear regression of y = - 1.35x + 62.32 was observed, whereas the dpn of inulin decreased from 12-14 to 6-8. In late cultivars this correlation was not as exact (r = - 0.502**); dpn of inulin decreased from 12-16 to 7-10. This knowledge about carbohydrate profiles for different varieties of Jerusalem artichoke offers the possibility of selecting suitable cultivars and deciding the appropriate harvest time for an optimum processing of tubers for their application as prebiotic and novel food component.     

Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions

Purpose

The study aimed to describe the carbohydrates and amino compounds content in soil, the light fraction (LF), the >53 μm particulate organic matter (POM), and the mobile humic acid (MHA) fraction and to find out whether the carbohydrates and amino compounds can be used to explain the origin of SOM fractions.

Materials and methods

Soil samples were collected from two agricultural fields managed under organic farming in southern Italy. The LF, the POM, and the MHA were sequentially extracted from each soil sample then characterized. Seven neutral sugars and 19 amino compounds (amino acids and amino sugars) were determined in each soil sample and its correspondent fractions.

Results and discussion

The MHA contained less carbohydrate than the LF or the POM but its carbohydrates, although dominated by arabinose, were relatively with larger microbial contribution as revealed by the mannose/xylose ratio. The amino compounds were generally less in the LF or the POM than in the MHA, while the fungal (aspartic and serine) and bacterial (alanine and glycine) amino acids were larger in the MHA than in the LF or the POM, underlining the microbial contribution to the MHA. Results from both sites indicated that total carbohydrates content decreased moving from the LF (younger fraction) to the MHA (older fraction), which seems to follow a decomposition continuum of organic matter in the soil-plant system.

Conclusions

The study showed that the MHA is a labile humified fraction of soil C due to its content of carbohydrates and concluded that the content of carbohydrates and amino compounds in the LF, the POM and the MHA can depict the nature of these fractions and their cycling pattern and response to land management.

     

日粮纤维对生长猪生长性能和胴体组成的影响

选取60头"杜长大"三元杂交生长猪作为试验动物,研究提高日粮纤维含量对生长猪生产性能和胴体组成的影响。结果表明,使用甜菜渣和苜蓿草粉作为主要纤维源,将生长猪日粮中粗纤维含量由3%提高到6%,对生长猪的日增重和日采食量没有产生显著的影响(P>0.05);但显著降低了料重比(P<0.05)。而将生长猪日粮中粗纤维含量由3%提高到8%,日增重和日采食量出现下降的趋势,料重比有所升高,与对照组相比,差异不显著(P>0.05)。提高日粮中的纤维含量,对屠宰率没有显著影响(P>0.05),平均背膘厚、腹脂率、脂肪率随纤维含量的提高呈现下降趋势,而瘦肉率较对照组有所提高,但差异不显著(P>0.05)。将生长猪日粮中粗纤维含量由3%提高到8%,显著降低了背最长肌中粗脂肪的含量(P<0.05),对粗蛋白的含量没有显著影响(P>0.05)。