Polyphenols are the most important phytochemicals in our diets and have received great attention due to their broad benefits for human health by suppressing oxidative stress and playing a protective role in preventing different pathologies such as cardiovascular disease, cancer, diabetes, and obesity. The stability of polyphenols depends on their environments of processing and storage, such as pH and temperature. A wide range of technologies has been developed to stabilize polyphenols during processing. This review will provide an overview of the stability of polyphenols in relation to their structure, the factors impacting the stability of polyphenols, the new products deriving from unstable polyphenols, and the effect of a series of technologies for the stabilization of polyphenols, such as chemical modification, nanotechnology, lyophilization, encapsulation, cold plasma treatment, polyphenol–protein interaction, and emulsion as a means of improving stability. Finally, the effects of cooking and storage on the stability of polyphenols were discussed.
Drying is a significant step in the production of carrageenan. However, current drying process still deals with too long drying time and carrageenan quality degradation. The foam mat drying is an option to speed up drying process as well as retaining carrageenan quality. In this case, the carrageenan was mixed with egg white (albumin) as foaming agent and methyl cellulose for foam stabilizer. The foam will break the carrageenan gels and creates the porous structure resulting higher surface area for water transfer. This research studied the effect of egg white and methyl cellulose on carrageenan drying at various air temperature, and thickness. As a response, the water content versus time was observed and the drying rate was estimated. Meanwhile, the carrageenan texture was verified by X-RD (X-Ray Diffraction) and TEM (Transmission Electron Microscopy). Results showed that the presence of egg white stablized by methyl cellulose can speed up drying rate as well as retaining the crystalline structure of carrageenan. The higher albumin content, the faster drying rate. However, the addition of albumin and methyl cellulose restricted not more than 30 % in the mixture for keeping carrageenan quality and purity. By adding egg white 20 % and methyl cellulose 10 %, the water diffusion and drying rate can be two fold compared with carrageenan drying without foam. The improvement can be higher at the higher temperature and thinner carrageenan sheets.
a b s t r a c tThe objective of this study was to investigate the drying kinetics of chempedak (Artocarpus integer) at different drying temperatures (50°C, 60°C, 70°C) and slab dimensions. The drying data were fitted to the different semi-theoretical models based on moisture ratio (MR) to predict the drying kinetics. A logarithmic model was found to be the best fit in this study for all the drying temperatures tested. Effective diffusivities were estimated from Fick's 2nd law and the Arrhenius equation was used to determine the diffusivity constant (D o ) and activation energy (E a ). The texture and color of dried product were altered significantly during drying. The total color change (DE), hardness and chewiness were found to be increased with elevated temperature; meanwhile, springiness and cohesiveness of dried chempedak were relatively constant.
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