Plasma is the forth state of matter or more correctly, the discharged gas. It is a mixture of partially ionized gas that contains reactive species, such as electrons, positive and negative charge ions, free radicals, gaseous atoms and photons. Plasma treatment can effectively inactivate a wide range of microorganisms including molds, bacteria, spores and viruses. The present study was designed to investigate the effect of atmospheric cold plasma (ACP) on production of soy protein isolate (SPI)-carboxy methyl cellulose (CMC) conjugate. In order to understand the mechanism of the ACP technology in production of protein-polysaccharide conjugate, changes in physicochemical properties of SPI was also evaluated. For this purpose, SPI powder treated with ACP for 0, 5, 10, 15 min in 16, 18, 20 Kv. Then, pH, solubility, water hold capacity (WHC), emulsion activity and stability, foaming capacity and stability, total and reactive sulfhydryl, free carbonyl, SDS-PAGE, FTIR, circular dichroism (CD), and FE-SEM were evaluated on the treated samples. The result indicated that time, voltage and simultaneous effect of them didn’t had significant effect on pH (p 0.05). This is while emulsifying properties, solubility, WHC, and foaming activity of SPI was improved after treatment with ACP (p 0.05). With enhancement of exposure time to ACP, free and reactive sulfhydryl and free carbonyl increased until 20 Kv exposure and then decreased (p 0.05). The results of FTIR and CD indicated protein partial denaturation, and unfolding of ?-helix structure of proteins until 10 min exposure and then production of protein aggregates can be the reasons of physicochemical and functional changes in SPI. These results were confirmed with the FE-SEM images. After that, SPI and CMC mixed with ratio of 1:1 and treated with ACP as mentioned before. Then solubility, emulsion activity and stability, emulsion droplet size, free amine, SDS-PAGE and FTIR were evaluated on treated samples. The result of free amine, SDS-PAGE and FTIR approved conjugate formation after plasma treatment. However, the formation of conjugate was influenced by voltage and time of ACP exposure. The emulsifying properties and solubility of conjugates were significantly higher than the mixture of SPI-CMC (p 0.05). Samples were treated at 18kV for 5 min had the lower droplet size after emulsion formation and the produced emulsion indicated the highest stability during 14 days storage. Finally, it was found that ACP treatment can generate SPI-CMC conjugate in very short time, with ideal emulsifying properties. Keywords : Atmospheric cold plasma; soy protein isolate, conjugate, carboxy methyl cellulos
