Effect of dry-salt processing on the textural properties and cell wall polysaccharides of cv. Thasos black olives

BACKGROUND: Thasos is an olive variety cultivated mainly in Greece used to produce ‘naturally black dry-salted olives’. This process consists in placing the olives in disposed layers with coarse sodium chloride. The loss of water and other solutes gradually debitters and wrinkles the fruits. In this study, the effect of dry-salt processing on the texture and cell wall polysaccharide composition was investigated. RESULTS: This type of processing affected primarily the mechanical properties of the olive flesh. In processed olives, this tissue was approximately 4.5 times stronger and also more deformable up to failure and stiffer than that from the raw olives. The dry-salt processing had its strongest effect on pectic polysaccharides. This included the increment of solubilization of arabinose-rich polymers in aqueous solutions, and thus their partial loss to the soak medium during dry-salting. Contrarily, galacturonic acid-rich polymers were further retained in the processed olives, probably by their stabilization within the cell walls by reduction of the electrostatic repulsion between the acidic groups of these polysaccharides due to sodium ions. CONCLUSION: The texture improvement of olive flesh by dry-salt processing seems to be correlated with the reorganization of the galacturonic acid-rich pectic polysaccharides into the cell wall of the fruit

Effects of Temperature and Water Content on the Secondary Structure of Wheat Gluten Studied by FTIR Spectroscopy

The effect of temperature on gluten conditioned at the following water contents, 0%, 13%, and 47% (wet weight basis), was studied by FTIR spectroscopy over the temperature range of 25-85 °C. A detailed discussion of the assignment of the amide I band is given. At 0% hydration no changes in the secondary structure with temperature could be detected; spectra were consistent with a tight disordered structure with many protein-protein interactions. At 13% hydration, distinctive changes occurred in the low-frequency region of the amide I band (1630-1613 cm-1). This was attributed to changes in the ß-sheet structure. On cooling to 25 °C, these changes were mainly reversed. It was noted that most of the changes observed occurred above the glass transition temperature. At 47% hydration, more complex changes took place: as the temperature was raised distinct bands at 1630 and 1613 cm-1 merged. However, this process was partially reversed, with recovery of both bands, on cooling. The significance of these results in relation to other changes in gluten proteins in flour and dough with temperature and water content is discussed

Physical properties of zein films containing salicylic acid and acetyl salicylic acid

Zein films containing salicylic acid (SA) and acetyl salicylic acid (ASA) between 2 and 10% (initial zein weight basis) with or without glycerol were evaluated for structure, mechanical and dissolution properties. The random coils, a helices and ß sheets mainly governed the secondary structure of zein, depending on glycerol and level of model molecules. Adding ASA resulted in an increase in a helices whereas ß sheets increased at the expense of a helices when SA was used. Including SA or ASA decreased the tensile strength and the stiffness of films containing glycerol indicating the synergistic effect of SA and ASA. The strain at failure decreased with increasing content of SA but increased with increasing level of ASA. The dissolution properties were glycerol and drug dependent. ASA release in comparison to SA was quite low. The release was only observed above 10% ASA whereas it was detected in all films containing SA. The possible interactions between active components and proteins are discussed together with their implications on the physical properties of zein films

Study of the physical properties of kafirin during the fabrication of tablets for pharmaceutical applications

Kafirin and protein bodies were extracted from a condensed tannin-free white Sudanese cultivar of sorghum (Dabar). The extracted materials were characterized by SDS-PAGE. The potential of kafirin as a tablet matrix for pharmaceutical applications was studied. Tablets composed of kafirin, calcium hydrogen orthophosphate, caffeine and magnesium stearate were prepared by direct compression. The tablets showed appropriate levels of hardness and friability. Drug release studies showed that caffeine dissolution was greater in 0.1 M HCl than in either phosphate buffer (pH = 6.8) or distilled water. Deamidation of the protein in acid conditions might explain this observation. FTIR analysis showed that the secondary structure of kafirin was found to be mainly governed by a helices with some ß sheets. Upon tabletting, there was a change in protein conformation, which was recovered upon dissolution irrespective of the dissolution media. This might be explained by the loss of protein coil to coil interaction during tabletting (possibly due to the diluting effect of calcium hydrogen orthophosphate). This was later recovered when tablets were dissolved due to the hydrophobic interactions between the kafirin proteins. In summary, this work has shown that kafirin has a potential for use as a tablet for drug delivery

Traditional and industrial oven-dry processing of olive fruits: influence on textural properties, cell wall polysaccharide composition, and enzymatic activity

The preparation of table olives according to the Italian traditional “Ferrandina” method (Fer) includes an initial blanching step of black Cassanese olives, followed by salting and oven-drying. Its industrial implementation, also called the “Sybaris” method (Syb), replaces the blanching procedure by cutting the olives followed by immersion in water. The measurement of tensile properties showed that the Fer processing increased the weakness, softness, and deformability of the skin and the flesh of olive fruits, while the flesh of the Syb fruits became stronger and stiffer. These differences are probably correlated to the degradation and/or reorganisation of cell wall polysaccharides in the fruits. The degradation of pectic and hemicellulosic polysaccharides in the Fer olives was inferred by their increased solubility in aqueous solutions. Contrarily, retention of pectic polysaccharides was observed in Syb olives. As no correlation was found between cell wall degrading enzymatic activities and cell wall polysaccharides extractability, it is probable that these modifications were driven by heat