The aim of this study is to determine the effects of plasticizer hydrogen bonding capability and chain length on the molecular structure of sodium caseinate (NaCAS), in NaCAS/glycerol and NaCAS/polyethylene glycol 400 (PEG) systems. Both solution and film phases were investigated. Glycerol and PEG reduced the viscosity of aqueous NaCAS, with the latter having a greater effect. This was explained in terms of protein/plasticizer aggregate size and changes to the conformation of the caseinate chain. In the film phase, glycerol caused more pronounced changes to the film tensile strength compared with PEG. However, the effect of glycerol on film water vapor permeability was smaller. These observations are attributed to the differences in plasticizer size and hydrogen bonding strength that controls the protein-plasticizer and protein-protein interactions in the films. Glass transition calculations from the tensile strength data indicate that the distribution of bonding interactions is more homogeneous in NaCAS/PEG films than in NaCAS/glycerol films.

The effects of ferric and ferrous ions, pH, and temperature on the stability and antioxidant activity of black currant anthocyanins (BCA) were studied, and the recovery of BCA from glucan gel [mixed linked (1-->3,1-->4)-beta-D-glucan] after using different encapsulating procedures was determined. The degradation of individual anthocyanins follows first-order kinetics and shows Arrhenius temperature dependence. The activation energies of individual anthocyanins, evaluated over the temperature range 60-100 degrees C, decrease with an increase in pH. While the antioxidant activity of BCA, measured by the ferric reducing antioxidant power assay, decreased with the degradation of anthocyanins, the completely degraded products still exhibited approximately 30% of the initial antioxidant activity. Ferric ions have a detrimental effect on the stability of BCA, especially for delphinidins. Freeze drying of encapsulated BCA gives approximately 20% higher recovery of individual anthocyanins than infrared drying.

No abstract

Raman spectroscopy of water was used to assess the metabolic state of fresh corneae and those which had been stored under long‐term organ culture conditions. Both human and porcine tissue were employed. The data showed a semi‐quantitative relationship between corneal hydration (determined using wet and dry weights of the tissue) and the integrated intensity of the water to collagen bands in the spectral region 2700—4000 cm−1. Variables included duration of storage, composition of culture medium and, for the human specimens, the age of the cornea. Raman assessment of hydration may provide a better measure of the functional state of the stored cornea that the density of live endothelial cells, which is a commonly used criterion. The spectra showed that the healthy cornea of low water content contained more weakly hydrogen‐bonded water than either bulk water or a swollen cornea. This is to be expected as groups on proteins and proteoglycans in the cornea form weak bonds with water. These weakly bonded surface groups are diluted when water is imbibed, hence resulting in the spectrum becoming more like that of bulk water in swollen tissue. Addition to the culture medium of dextran, which osmotically thins the cornea, converted its water spectrum back towards that of a healthy cornea.

Raman difference spectroscopy has been employed to elucidate the effect of the alkali-metal (Li', Na+, K + , Rb+ and Cs') and alkaline-earth-metal cations (Mg2+, Ca2+, Sr2+ and Ba") on the polyether chain conformations of alkylphenoxypolyoxyethylene-type surfactants, C,H, ,Ph(CH,CH,O),OHwhere n" = 9.5, in aqueous media. A band appeared at ca. 868 cm-' in the spectrum of the surfactant upon the addition of some cations: this feature is assigned to a surfactant-cation complex incorporating a polyether chain exhibiting a TTGTTG (T, trans; G ; gauche ; G, gauche minus) or similar conformation sequence. The surfactant complexed preferentially to Ba2+ and K + , with :he effect being greater for the former ion. A Ba2+ concentration-dependence study suggested that 1 : 2 and 1 1 3 surfactant-cation complexes are formed in the surfactant-water-salt system. The 1 : 3 coordinate complex appeared to be dominant. Models are proposed for the structure of these complexes.