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 mold, bacteria, spores and viruses. The present study was designed to investigate the effect of cold atmospheric plasma on myofibrillar proteins extracted from beef. For this purpose, myofibrillar proteins were extracted from Longissimus dorsi muscle and then 30 ml of 3% myofibrillar proteins treated with Atmospheric cold plasma (ACP) for 0, 5, 10, 15, 20 minutes in two duty cycle (D) of 5 and 10% and 7KHz frequency. Maximum power, voltage and amperage was 30W, 12Kv and 1 mA. Then, pH, foaming capacity and stability, emulsion capacity and stability, color, free sulfhydryl and carbonyl, water holding capacity (WHC), water binding capacity (WBC), SDS-PAGE, FTIR and DSC were evaluated on treated samples. The results indicated that time and D of ACP didn’t have significant effect on pH value but simultaneous effect of them had significant effect on pH. ACP didn’t have significant effect on L*, a* and b* value of myofibrillar proteins. Time and D of exposure to ACP significantly changed foaming capacity so that the maximum foaming capacity observed after 10 minutes exposure time and minimum one observed in control sample. Foam stability measured after 10, 30, 60 min. The foam stability was slightly decreased after 10 min; however, it was increased after 20 min exposure to plasma. Emulsion capacity was also influenced by independent variables. It increased after 10 min exposure to ACP and then decreased. The simultaneous effect of time and D on the emulsion stability was also significant. The WHC and WBC were changed considerably by increase of plasma radiation time so that WBC and WHC were increased and decreased, respectively. With enhancement of exposure time to ACP, free sulfhydryl increased until 10 min exposure and then decreased. However, free carbonyl of myofibrillar protein with rise of exposure time significantly increased. FTIR and DSC indicated proteins denaturation and unfolding of ?-helix structure of proteins until 10 min exposure and then aggregation of myofibrillar proteins. Electrophoresis pattern confirmed the aggregation of proteins. Finally, application of 10 min ACP for meat is proposed because of proper effects on meat physicochemical characteristics such as emulsion capacity as well as slight adverse effects on meat properties. Keywords: Cold atmospheric plasma, Myofibrillar proteins, Oxidation, Red meat
