A fast and simple methodology for determination of yttrium as an inert marker in digestibility studies

The need to develop a fast, simple and low cost methodology for the determination of yttrium in fish diets and faeces using a microwave digestion system and atomic absorption spectrometry with flame atomization analysis was the main aim of this study. The final methodology consisted in the digestion of approximately 300 mg of dry fish diet or 100 mg of dry fish faeces in teflon vessels using Parr reactor bombs, at high pressure, in a domestic microwave system with nitric acid solution. After digestion, 330 μl of a 120 mg potassium nitrate/ml solution was added to each solution. Yttrium was determined using a calibration with aqueous standards. Analytical difficulties and problems encountered during the optimizations were overcome and the application of the final methodology to the fish diets and faeces samples was carried out with suitable results.     

Nutritional value of cowpea (Vigna unguiculata L. Walp) meals as ingredients in diets for Pacific white shrimp (Litopenaeus vannamei Boone)

The nutritional value of cowpea (Vigna unguiculata L. Walp) meals, as ingredients in diets for Litopenaeus vannamei, was evaluated. Five experimental meals were prepared in the laboratory: whole raw cowpea (WRC), dehulled (DC), cooked (CC), germinated (GC) and extruded (EXC). The crude protein content of WRC (26.1%) increased after germination (29.5%). Carbohydrates ranged from 69.4% to 85.9%. The trypsin inhibitor activity of WRC meal was low (7.52 U/mg dry matter), and was reduced or eliminated by cooking and extrusion. Apparent digestibility of dry matter, protein and carbohydrate of the diet containing whole raw cowpea meal (71.1%, 85.9% and 76.7%, respectively) was similar to the control diet. Cooking and extruding of cowpea significantly increased dry matter, protein and carbohydrate digestibility in the diets. The results suggest that cowpea meals are good sources of nutrients and can be used as ingredients in diets for L. vannamei.     

Genetic variation in degradability of wheat straw and potential for improvement through plant breeding

The degradability of cereal straw is of importance when it is used for animal feed, biological means of bioenergy production such as bioethanol production and when it is incorporated in soil. We examined wheat straw from 106 different winter wheat cultivars representing the northwest European contemporary gene pool. The cultivars were grown at two different locations to assess the potential for breeding for improved degradability. The straws exhibited much variation in degradability ranging from 258 g kg⁻¹ to 407 g kg⁻¹ of dry matter. The heritability for degradability was estimated to 29% indicating a reasonable potential for response to selection. Inclusion of height as a regression-term, indicated that only a minor part of genetic differences are directly related to plant height and that improvements in degradability may be achieved without unacceptable changes in straw length. Finally, a lack of correlation between degradability and grain yield indicated that straw degradability may be improved through breeding without serious negative effect on grain yield.     

Physicochemical properties and in vitro digestibility of resistant starch from mung bean (Phaseolus radiatus) starch

RS from mung bean starch was prepared by autoclaving, pullulanase debranching, and retrogradation. Physicochemical properties, crystalline structure, and in vitro digestibility of selected RS samples with different RS content were investigated. Compared to native starch, AAM content of RS increased but MW decreased greatly. SEM clearly showed RS samples exhibited irregular shaped fragments with compact structure. XRD pattern indicated that RS samples had typical B‐type pattern with sharp peaks at 17.0°, 22.2°, and 23.9° 2θ. The relative crystallinity, gelatinization temperatures, and enthalpy increased with increasing RS content. The α‐amylase digestibility of RS was lower than that of native starch. The results suggested that the decrease in enzymatic digestion of RS might due to compact and ordered crystalline structures after debranching and recrystallization.     

In vitro digestibility of bacillus fermented soya bean

Bacillus fermented legume products include among others dawadawa and soumbala made from African locust bean, and natto and kinema made from soya bean. Bacillus subtilis is the dominant species involved in the fermentation. During Bacillus fermentation for 48 h of autoclaved soya bean the quantity of soluble and dialyzable matter increased from 22% and 6% up to 65% and 40%, respectively. Protein and carbohydrate degradation during fermentation of soya bean with several Bacillus spp. was investigated and appeared to be substantial during the first 18 h of fermentation resulting in the release of high levels of peptides and oligosaccharides. In vitro digestibility was increased from 29% up to 33–43% after Bacillus fermentation for 48 h. It was shown that Bacillus spp. were able to degrade soya bean macromolecules to a large extent resulting in water-soluble low molecular weight compounds. In vitro digestion of Bacillus fermented soya bean using gastrointestinal enzymes only slightly increased the amount of dialyzable matter, which clearly demonstrated the beneficial effect of Bacillus fermentation on food nutrient availability.     

Digestibility of fatty acid monomers,dimers and polymers in the rat

This study was designed to determine digestibilities of fatty acid monomers, dimers and polymers as components of diets containing thermally oxidized oils. Male Wistar rats were fed semipurified diets supplemented with unheated, heated and a 1:1 mixture of unheated/heated olive oils at 6, 12 and 20% w/w of diet. In a 14-d experimental period, fecal lipids were extracted and analyzed by a combination of adsorption and high-performance size-exclusion chromatographies. Thus, it was possible to separate and quantitate five groups of fatty acids—nonpolar monomers, oxidized monomers, nonpolar dimers, oxidized dimers and polymers. Nonpolar fatty acid monomers showed high digestibilities, although significantly influenced by the alteration level of the dietary oil. The apparent absorption of oxidized fatty acid monomers averaged 76.6%. Among polymeric fatty acids, the lowest digestibilities were found for nonpolar dimers (10.9% on average), whereas oxidized dimers and polymers possessed higher apparent absorbability than expected, ranging from 22.7% to 49.6%. Chemical modifications prior to absorption, leading to less complex products, may have contributed to enhanced digestibility of polymers.     

Anti-Diabetic Potential of Phenolic Compounds: A Review

Starch is the main carbohydrate in human nutrition. Starch digestibility can vary from a rapid digestion to indigestibility. Therefore, postprandial glycaemic control in type 2 diabetics is of great interest in the context of worldwide health concerns. Although powerful synthetic inhibitors of starch digestive enzymes, such as acarbose, are available to control postprandial hyperglycemia, plant-based enzyme inhibitors are potentially safer. Natural enzyme inhibitors, such as wheat albumin, the Phaseolus vulgaris α-amylase inhibitor, and several phenolic compounds, have the potential to serve as a remedy against hyperglycemia-induced chronic diseases. The inhibition of α-amylase and α-glucosidase is mediated by different phenolics found in varieties of raspberry. Maltase inhibitory activities of chebulagic acid and chebulinic acid from fruit of Terminalia chebula are comparable to that of acarbose. The Nepalese herb Pakhanbhed (Bergenia ciliata) phenolics, (-)-3-O-galloylepicatechin and (-)-3-O-galloylcatechin, showed effective inhibition against starch digesting enzymes. In separate studies, oral administration of starch and maltose with persimmon (Diospyros kaki) leaf tea proanthocyanidins [containing (-)-epigallocatechin-3-O-gallate] and black/bitter cumin (Centratherum anthelminticum) seed phenolics, respectively, resulted in a significant and dose-dependent decrease in the blood glucose level in Wistar rats. Co-application of phenolics with synthetic enzyme inhibitors may reduce the effective dose of synthetic inhibitors required in the regulation of starch digestion. Several phenolic compounds might be useful functional food components and could contribute to manage both hyperglycemia and proper cellular redox status. Human dose-selecting studies and well-controlled long-term human studies would help to optimize the beneficial effects of phenolic compounds.     

Effect of animal (lamb) diet and meat storage on myofibrillar protein oxidation and in vitro digestibility

Effect of pasture- or concentrate-diet on myofibrillar protein oxidation and in vitro digestibility was measured in lamb meat (M. longissimus dorsi) during a refrigerated storage of 7days under gas permeable film. Protein oxidation was measured by the carbonyl content determined chemically using 2,4-dinitrophenylhydrazine (DNPH) and specific targets of oxidation were identified by immunoblotting. Carbonyl content significantly increased during storage and diet affected protein oxidation where animals fed concentrate showed higher carbonyl group levels than animals fed pasture. To evaluate effect of diet and storage time on protein digestibility, myofibrillar proteins were exposed to proteases of the digestive tract (pepsin, and a mixture of trypsin and α-chymotrypsin) in conditions of pH and temperature which mimic digestive process. The myofibrillar protein digestibility was not influenced by the diet. Storage time had no significant effect on myofibrillar protein susceptibility to pepsin while an important increase in digestibility by trypsin and α-chymotrypsin was detected during storage.     

In vitro digestibility of flaxseed (Linum usitatissimum L.) protein: effect of seed mucilage,oil and thermal processing

Flaxseed (Linum usitatissimum L.) protein is reported to release physiologically important amino acids and bioactive peptides during gastrointestinal (GI) digestion. The effect of seed mucilage and oil and thermal processing on the in vitro protein digestibility (IPD) of flaxseed protein was assessed under simulated GI digestion. Protein in ground whole flaxseed that contained both mucilage and oil had the lowest digestibility (12.61%). Baking and boiling before size reduction significantly (P < 0.05) improved the IPD (31.77% and 28.04%, respectively). Further increase in IPD occurred when mucilage (51.00%) and both mucilage and oil (66.79%) were removed. Isolated flax protein had a similar IPD value (68.00%) as the mucilage and oil–removed flaxseed. The polypeptide of approximately 13 kDa showed resistance to GI digestion compared with other polypeptides of all these treated seeds. Removal of oil and mucilage as well as thermal treatment enhanced protein digestibility of flaxseed.     

挤压膨化及添加魔芋粉对燕麦-玉米混粉糊化特性及体外消化率的影响

本研究制备了燕麦-玉米挤压膨化粉并探究添加魔芋粉共挤压对混粉理化性质的影响,实验主要测定其基本营养成分、糊化特性和体外消化特性。结果表明,挤压膨化处理后,原料中脂肪含量和快消化淀粉含量显著降低（P＜0.05）,其中脂肪含量由9.38%降至3.06%,但对抗性淀粉含量无影响（P＞0.05）,原料粉与挤压膨化粉eGI值分别为66.03和67.34,均属于中GI物料。添加魔芋粉与燕麦玉米混粉共挤压后,不同添加量魔芋粉均能显著降低混粉中快消化淀粉含量（P＜0.05）,提高慢消化淀粉和抗性淀粉含量, 添加5%、10%、15%魔芋粉后eGI值显著降低（P＜0.05）,分别为48.06、48.51和49.11,均属于低GI物料,可作为代餐产品原料使用。