Acid-extracted crystalline protein isolates and alkali-extracted amorphous proteins from four Phaseolus beans were investigated for thermal and surface properties. Differential scanning calorimetry (DSC) analysis of crystalline isolates gave denaturation enthalpy (AH) values ranging from 12.4 to 31.0 J/g; for amorphous isolates of the same beans AH ranged from 10.3 to 11.9 J/g, suggesting that the crystalline proteins were less denatured than the corresponding amorphous isolates. Differences in protein content, nitrogen solubility index (NSI), surface hydrophobicity (So), and foam expansion were observed between the alkaliand acid-extracted isolates. The alkali-extracted isolates showed protein contents ranging from 69.62 to 81.61%, NSI of 24.23-66.75%, So of 2128-17 000 FI%_1, and foam expansions of 30.0-49.0%. The acid-extracted isolates showed higher protein contents (75.84-96.09%) and NSI (52.19-92.37%) but much lower So (1966-7479 FI%_1) and low foam expansion (3.0-26.0%). Surface tension of crystalline and amorphous proteins solutions ranged from 54.8 to 58.5 and from 54.2 to 56.3 mN/m, respectively. However, the rate of decay of tension in the crystalline isolates was lower than that of the corresponding amorphous isolates. Regression analysis revealed that protein surface activity was dependent on protein content and surface hydrophobicity.gel electrophoresis (Alii and Baker, 1983), size exclusion chromatography (Musakhanian and Alii, 1987), and ionexchange chromatography (Alii et al., 1990) as well as differences in sugar composition of the carbohydrate * Author to whom correspondence should be addressed.
Sugar alcohols and parabens are commonly used ingredients in oral suspension formulations. However, their possible incompatibility because of transesterification reaction is a concern during formulation development. In order to gain more knowledge about the reaction, a high-performance liquid chromatographic (HPLC) method is developed to separate the transesterification reaction products of methylparaben preservative with twelve 3- to 6-carbon sugar alcohols and propylene glycol. It is found that the number of peaks separated or partially separated correlate well with the number of distinct hydroxyl groups present in the sugar alcohol molecules. This means that all the hydroxyl groups in a sugar alcohol molecule can react with methylparaben to form transesterification reaction products. These products are positional isomers that have identical UV spectra with a maximum at 255 nm and the same m/z ratio for molecular ions by liquid chromatography-mass spectrometry. When isolated individually, they can isomerize (interconvert) under suitable conditions to form other positional isomers by intramolecular acyl migration. The acyl migration pathway for each of the isolated positional isomers from the transesterification reaction of methylparaben with sorbitol, ribitol, and xylitol is followed by HPLC. Based on the information, a tentative assignment of the six isomer peaks generated from the transesterification reaction between methylparaben and sorbitol is proposed.
A method has been developed for the measurement of diastatic activity of forage additive products which contain malt flour as active ingredient. The procedure Involves extraction of the enzyme activity with calcium chloride solution, Incubation of the extract with excess soluble starch, and measurement of the unhydrolyzed starch by the starch-iodine reaction. The conditions established for optimum enzyme activity were 1 % calcium chloride solution for enzyme extraction, and enzyme-starch reaction pH and temperature of pH 5.5 and 40 °C, respectively. With the combination of these experimental conditions, the diastatic activity, expressed as g starch hydrolyzed per g material per h (SKB) (a) of malt diastase was 75.9 SKB units, (b) of malt flour was 32.8 SKB units, and (c) of 2 forage additive products were 0.205 SKB unit and 0.044 SKB unit.
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