Search

Highlights: [•] Conjugation of durian seed gum (DSG) with whey protein (WPI) promoted its emulsifying activity. [•] Covalent linkage of WPI to DSG facilitated its adsorption into the water/oil interface. [•] WPI–DSG conjugate exhibited better functional properties than DSG alone. [•] Fehling solution induced better functional properties than saturated barium hydroxide for DSG. [Copyright &y& Elsevier]

Natural biopolymers from plant sources contain many impurities (e.g., fat, protein, fiber, natural pigment and endogenous enzymes), therefore, an efficient purification process is recommended to minimize these impurities and consequently improve the functional properties of the biopolymer. The main objective of the present study was to investigate the effect of different purification techniques on the yield, protein content, solubility, water- and oil-holding capacity of a eteropolysaccharide-protein biopolymer obtained from durian seed. Four different purification methods using different chemicals and solvents (i.e., A (isopropanol and ethanol), B (isopropanol and acetone), C (saturated barium hydroxide), and D (Fehling solution)] to liberate the purified biopolymer from its crude form were compared. In most cases, the purification process significantly (p < 0.05) improved the physicochemical properties of heteropolysaccharide-protein biopolymer from durian fruit seed. The present work showed that the precipitation using isopropanol and acetone (Method B) resulted in the highest purification yield among all the tested purification techniques. The precipitation using saturated barium hydroxide (Method C) led to induce the highest solubility and relatively high capacity of water absorption. The current study reveals that the precipitation using Fehling solution (Method D) most efficiently eliminates the protein fraction, thus providing more pure biopolymer suitable for biological applications. [ABSTRACT FROM AUTHOR]

Ready-to-use indicatory forms shaped as tablets, e.g., glucotests, are proposed for the rapid semi-quantitative determination of glucose in foodstuffs. Their function is based on the classical Fehling's reaction with the selection of reagents aimed to eliminate the influence of proteins, reduce sample pretreatment to a minimum, and perform the test within 10 min. The glucotests are economical, simple to manufacture, and have no limits for shelf life and storage conditions. If necessary, the glucotests can be applied for the quantitative determination of glucose as well. To do this, a photometric procedure is proposed based on the quantification of unreacted copper acetate in the composition of the glucotest by its intrinsic absorbance. To analyze colorful products, sample pretreatment using an anion-exchange resin in the acetate form is recommended. [ABSTRACT FROM AUTHOR]

Abstract: A novel and sensitive resonance scattering (RS) spectral immunoassay for the determination of microalbumin (Malb) was developed, based on the catalytic effect of immunonanogold (ING) probe on Fehling reagent–glucose reaction, and resonance scattering effect of Cu2O particles. Nanogold particles in size of 10nm were used to label goat anti-human microalbumin (GMalb) to obtain an ING probe (AuGMalb) for Malb. The probe produced unspecific aggregation in pH 5.0 citric acid–Na2HPO4 buffer solutions. Upon addition of Malb, the dispersed ING complex formed. The ING complex in supernatant was obtained by centrifuging and was used as catalyst for the reaction between Fehling reagent and glucose to form the Cu2O particles to amplify the resonance scattering signal at 610nm. With addition of Malb, the ING complex in the supernatant increased and the RS intensity at 610nm (I 610nm) enhanced linearly. The enhanced intensity ΔI 610nm was proportional to the Malb concentration in the range of 0.014–0.43ngml−1, with a detection limit of 7.2pgml−1. The proposed method was applied to detect Malb in human urine sample with satisfactory results. [Copyright &y& Elsevier]

The Pizzolato test for calcium oxaIate crystals was applied to Dioscorea campestris. A blackening of intraamylar localization was obtained with this technique (silver nitrate and concentrated hydrogen peroxide). Nevertheless, the X-ray diffraction and crystal analysis were both negative for calcium oxalate and calcium respectively. The starch have single or semicompound granules, a great part of them have pores or holes in distal position with respect to the hilar region: sometimes there are 2 pores, with one of them in lateral position. The unmodified granules show the granule surface free from pores or cracks. The hole is supposed to be a conical crater erosion, a feature which is typical of the particular kind of starch granules highly resistant to liquefying α-amylase; the central portion is extensively affected as the erosion is in advance. The blackening produced by the positive Pizzolato test is related to that central portion of the damaged grains Microchemical tests with Fehling solution also revealed high concentrations of reducing sugars at these sites. It is possible that the silver reaction is due to the free reducing groups produced by hydrolysis of the internal central core, giving a false positive test for crystals. The X-ray diffraction powder diagrams obtained, yield data for a crystalline structure of amylose corresponding to the A-type starch. [ABSTRACT FROM AUTHOR]