Postharvest quality and safety of fresh-cut melon fruits coated with water soluble chitosan films

The research presents the effect of novel edible coatings based on low molecular weight chitosan on some properties of fresh-cut melon fruits – weight loss, total soluble solids, total acidity, mechanical strength and bacteria growth. Three different compositions were used as coatings – pure chitosan, chitosan and Ca lactate and alginate/chitosan multilayers. It was shown that the additional alginate layer substantially improves the protective properties of pure chitosan coating, resulting in preservation of cell structure. Negligible negative effect on the antibacterial activity of pure chitosan is demonstrated

Adsorption of Protein-Coated, Lipid Droplets to Mixed Biopolymer Hydrogel Surfaces: Role of Biopolyiner Diffusion

The adsorption of charged particles to hydrogel surfaces is important in a number of natural and industrial processes. In this study, the adsorption of cationic lipid droplets to the surfaces of anionic hydrogels was examined. An oil-in-water emulsion containing cationic β-lactoglobulin-coated lipid droplets was prepared (d32 = 0.24 μm, ζ = +74 mV, pH 3.0). An anionic hydrogel containing 0.1 wt % beet pectin and 1.5 wt % agar (pH 3.0) was prepared. Emulsions containing different lipid droplet concentrations (0.3−5 wt %) were brought into contact with the hydrogel surfaces for different times (0−24 h). The adsorption of lipid droplets to the hydrogel surfaces could not be explained by a typical adsorption isotherm. We found that the electrical charge on the nonadsorbed lipid droplets became less positive or even became negative in the presence of the hydrogel and that extensive droplet aggregation occurred, which was attributed to the ability of pectin molecules to diffuse through the hydrogels and interact with the lipid droplets. These results may have important consequences for understanding certain industrial and biological processes, as well as for the design of controlled or triggered release systems

Effect of fining and filtration on the haze formation in bayberry (Myrica rubra Sieb. et Zucc.) juice

Bayberry juice was fined with the methods of xanthan/chitosan (XC) or gelatin/bentonite (GB), and then filtered with diatomaceous earth filtration (DF) or ultrafiltration (UF, MWCO 100 kDa). Their effects on juice haze formation were investigated. The XC fining method was more effective than the GB method in removal of the total monomeric anthocyanin, total phenolics, and protein, with less haze formed in the XC fined juice. The DF reduced 2−5% of the total phenolics and 21−23% of protein, while UF reduced 19−24% of the total phenolics and 34−38% of protein, respectively. The results showed that fining and then UF can reduce but cannot eliminate haze formation in bayberry juice. The storage temperature was a critical factor affecting haze formation, and the juice was more stable when stored at lower temperature (4 °C). Copyright © 2007 American Chemical Society