pectins and thiobarbituric-acid

Filled hydrogel particles can be fabricated by incorporating an oil-in-water emulsion into portions of separated incompatible lower and upper phases together and remixing with later acidification to pH 5.0. The purpose of present study was to investigate the influence of different heat-denatured whey protein concentrates (HWPC)/high methoxy pectin (HMP) mass ratios (1:1, 2:1, 3:1, 4:1, and 5:1) of phase separated systems on the physical characteristics and stabilities of filled hydrogel particles. The results showed that the particle size of filled hydrogel particles significantly decreased with increasing HWPC/HMP mass ratios (P < 0.05), which was verified by reduced interfacial layer thickness. Moreover, decreased particle size also induced consistent reduction of the apparent viscosity and slightly increased the lightness. In particular, when the HWPC/HMP mass ratio was 3:1, the filled hydrogel particles exhibited the lowest amount of conjugated dienes and thiobarbituric acid-reactive substances after 10 days of storage (P < 0.05), which was mainly due to the highest amount of biopolymers distributed at the interfacial membrances (P < 0.05). Our results indicate that the phase separation system formed by HWPC/HMP mass ratio of 3:1 could be used to fabricate filled hydrogel particles with amplified stabilities at acidic pH for novel delivery systems.

Topics: Emulsions; Hydrogels; Hydrogen-Ion Concentration; Particle Size; Pectins; Phase Transition; Surface Properties; Thiobarbiturates; Transition Temperature; Viscosity; Whey Proteins

Several methods have been described for the detection and quantification of polygalacturonase (PG) and pectin lyase (PL) activities. The most frequently used tests are the Nelson method using copper(II) and an arsenomolybdate reagent to detect PG activity, and the colorimetric method using thiobarbituric acid (TBA) to detect PL activity. We observed that none of these methods are suitable to differentiate between these two enzymatic activities. Therefore, we optimized the test conditions of the TBA method. As a result, the detection of the enzymatic beta-elimination (PL activity) became sensitive and selective. A basic pretreatment at 80 degrees C for 5 min of the solution which contains the pectin fragments of the PL activity furnished aldehydes which were condensed with TBA or its derivatives. After acidification of the medium, a pink fluorescent dye was detected spectrophotochemically (lambda = 550 nm). The interference of galacturonic acid or oligomers resulting from PG activity was completely eliminated. The most sensitive reagent was N-(pyridin-2-yl)-thiobarbituric acid. The application of this method with the new reagent was extended to the screening of microorganisms possessing the PL activity. The obtained results confirm that Aspergillus niger strain and a Saccharomyces cerevisiae SCPP strain possess this activity.

Topics: Aspergillus niger; Colorimetry; Fluorescent Dyes; Pectins; Polygalacturonase; Polysaccharide-Lyases; Saccharomyces cerevisiae; Sensitivity and Specificity; Thiobarbiturates; Time Factors