ABSTRACT
Effect of calcium ions (Ca2+) on characteristics of zein-propylene glycol alginate (PGA) binary complex was studied in this work. Ca2+ induced the formation of zein aggregates with decreased fluorescence intensity and a significant α-helix loss of zein. Zein-PGA binary complex with Ca2+ showed the decreased dimension and the minimum size was observed at 50.0mM Ca2+. Ca2+ resulted in the formation of strong hydrogen bonds between zein and PGA, strengthened their hydrophobic interactions, and induced a new peak at the diffraction angle of 30° in the pattern of Zein-PGA binary complex. PGA fortified with Ca2+ exhibited an overall plane-like structure, also an interwoven flat profile appeared in Zein-PGA binary complex with Ca2+. Three potential mechanisms were proposed to explain the morphological changes of samples after Ca2+ addition: (i) particle-particle collision and aggregation of particles; (ii) chain-chain association and further cross-linking of associated chains; (iii) simultaneous cross-linking coupled with aggregation.
Subject(s)
Alginates/chemistry , Alginates/ultrastructure , Calcium/metabolism , Ions/metabolism , Zein/chemistry , Zein/ultrastructure , Calcium/pharmacology , Fluorescence , Hydrogen Bonding , Hydrophobic and Hydrophilic Interactions , Ions/pharmacology , Particle Size , Protein Binding , Protein Conformation , Protein Conformation, alpha-Helical , Zein/drug effectsABSTRACT
The effect of octyl gallate and propyl gallate on the molecular mobility, oxygen permeability, and microstructure of zein/glycerol films was studied. Films were cast from 70% ethanol/water containing 20% (w/w) glycerol and different amounts of the antioxidants propyl gallate or octyl gallate. The oxygen permeability and local mobility of these films were measured using phosphorescence from the dispersed triplet probe erythrosin B. Although both antioxidants increased the local mobility of the zein matrix to about the same extent, octyl gallate and to a lesser extent propyl gallate dramatically increased the permeability of the film to oxygen. Atomic force microscopy imaging indicated that propyl gallate induced aggregation of zein complexes, which could lead to a more condensed film. These results indicate that the addition of specific functional ingredients, such as antioxidants, to edible films may significantly affect the physical properties and structure and, thus, functional properties in ways that influence their eventual use.
Subject(s)
Antioxidants/pharmacology , Food Packaging/instrumentation , Oxygen/chemistry , Zein/chemistry , Chemical Phenomena , Diffusion , Gallic Acid/analogs & derivatives , Gallic Acid/pharmacology , Microscopy, Atomic Force , Permeability , Propyl Gallate/pharmacology , Spectrometry, Fluorescence , Zein/drug effectsABSTRACT
Skin compatibility of anionic surfactants may often but not always be predicted by in vitro tests. For instance, the correlation between in vivo and in vitro data is classically hampered in the presence of magnesium. This ion is known to interfere with in vitro skin irritation predictive tests based on protein denaturation. This study was conducted to compare a recently introduced assay, corneosurfametry, with other in vitro tests including the pH-rise of bovine serum albumin, collagen swelling, and zein solubilization tests. Corneosurfametry entails collection of cyanoacrylate skin surface strippings and short contact time with surfactants, followed by staining samples with toluidine blue and basic fuchsin dyes. Measurements are made by reflectance colorimetry. Data show that irritation potentials predicted by corneosurfametry agree with those obtained by established in vivo and in vitro irritation tests. Moreover, corneosurfametry data are not artificially lowered by addition of magnesium in surfactant solutions. In conclusion, corneosurfametry should be viewed as one of the realistic predictive tests for surfactant irritancy.
