Grape pomace, and insoluble and soluble dietary fiber (DF) fractions, obtained by enzymatic-gravimetric methods, were analyzed for neutral sugars, uranic acids, Klason lignin and amino acids. DF constituted 80% of dry matter, IDF was the major fraction. The main neutral sugar constituent of IDF was glucose. The major part was cellulose and the remainder, along with xylose, was a xyloglucan, which also contained fucose. Uranic acids accounted for 64% of SDF and a high amount of arabinose, galactose and mamtose were also included in that fraction. Proteins were not well solubilized by the assay enzymes. During the isolation of DF fractions a considerable solubilization of polyphenols was observed. These compounds were associated with Klason lignin in the starting material. Composition of DF fractions enables grape pomace to be considered a useful fiber-rich food ingredient.
Cocoa hull dietary fibre (DF) was evaluated by an enzymic-gravimetric method. Insoluble dietary fibre (IDF) and soluble dietary fibre (SDF) were subjected to acid hydrolysis and the resultant neutral sugars, uronic acids, and Klason lignin were quantified. Cocoa hull exhibited a high content of total dietary fibre (TDF), 504 g kg-' on a dry weight (DW) basis, IDF being the main fraction found. Glucose was the major sugar constituent of the IDF fraction whereas the uronic acids were equally distributed in the IDF and SDF fractions. The chemical composition reveals that pectic polysaccharides and cellulose contributed in similar amounts to TDF (107 g kg-' and 92 g kg-' DW, respectively). Non-starch polysaccharides accounted for 222 g kg-' DW, while the content of Klason lignin was lower (161 g kg-' DW). The main pectic substances in the insoluble fibre were low methoxyl pectins whilst those of the soluble fibre were high methoxyl pectins. Cocoa hull appears to be a good source of DF that might be used to supplement other sources of fibre or food products.
Cadmium binding capacity of cocoa and isolated total dietary fibre (TDF) was investigated in vitro under simulated physiological pH conditions. The effect of Cd2+ retention on the bioavailability of essential endogenous minerals was also studied. The sample was mixed with buffered Cd2+ solution and, after equilibration, the residue was separated for quantitative measurement of soluble Cd2+ in the supernatant. Cocoa exhibited a high affinity for Cd2+ in solution. The amount of bound Cd2+ rose with increasing metal concentration and pH. TDF was the major fraction responsible for binding of Cd2+ by cocoa. Phytate was probably another important cause of the decrease of Cd2+ solubility. The addition of various concentrations of Cd2+ to cocoa and TDF was shown to affect the solubility of endogenous minerals. When Cd2+ was bound by TDF there was a marked increase in the availability of endogenous Fe, Zn, Ca and Mg, specially at duodenal pH conditions.
The purpose of the present work was to study the dietary fibre (DF) fraction of olive cake and modify the fibre structure through enzymatic treatments in order to improve the sensory quality of this by-product for its incorporation into a baked product. Two different commercial enzyme preparations were used for enzymatic modifications: Viscozyme L, a hemecellulase/cellulase multienzyme complex, and Olivex which contains different pectolitic main activities as well as various side activities, hemicellulases and cellulases. D F consists of 800 g total dietary fibre per kg dry matter. More than 91% of the DF are insoluble and the monosaccharide composition of this fraction indicates the presence of mainly cellulose and xyloglucans or xylans. Approximately 75% of the uronic acids found in olive cake are associated to the insoluble D F (IDF). Arabinans and uronic acids polysaccharides are the major fibre components in the soluble D F (SDF) fraction. Enzymatic treatments with commercial preparations caused changes in the DF content and in the 1DF:SDF ratio depending on enzyme concentrations and incubation time. Baking experiments showed that a substitution of 10% of wheat flour by enzymatically modified olive cake led to an improved texture compared to products containing untreated cake.
The effect of roasting on dietary fiber fractions of cocoa beans was determined by gravimetric and fractionation procedures after enzymatic treatment. Roasting had no notable effect on total dietary fiber content (TDF). Components of insoluble dietary fiber (IDF) became redistributed after roasting. One of the largest changes was a sharp increase of Klason lignin. The noted decrease in sugar content without a change in IDF suggested that neutral sugars and uranic acids may be involved in Maillard polymer formation. Soluble dietary fiber (SDF) did not show large variations. Undigestible protein in IDF increased after roasting.
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