A low‐pressure plasma system was used to study the continuous decontamination of milk flowing at atmospheric pressure in a quartz tube. The plasma discharge generated at 2 kV, 1.5 cm electrode gap was characterized by optical emission spectroscopy, and evaluated for microbial reduction at a flow rate of 6 and 3 ml/min. It accounted for a maximum of ~95% microbial (coliforms) reduction at 3 ml/min (5 min exposure time). No detrimental effects were detected during plasma interaction on physicochemical properties such as pH, conductivity, acidity and nutrient contents namely protein, calcium, and lactose. The findings from this study reveal that the low‐pressure plasma system could be used for bulk processing of milk while reducing the microbial load without compromising the milk quality. This work on continuous plasma processing is an initiative for bulk processing of liquids, which could have a potential impact on industrial applications. Practical application The role of nonthermal plasma in food processing includes sterilization, decontamination, disinfestation, enzyme inactivation, allergen reduction, and property modification. The main application of this work is to provide an insight on alternative to batch‐type plasma processing of liquid foods. A continuous‐type plasma system for liquids was developed with an aim to increase the quantity of liquid foods used for decontamination. Maintenance of hygienic environment during processing in this plasma processing system is an added advantage which can be equivalent to hygiene maintenance on thermal in‐line pasteurization units.

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This work characterizes the oxidative changes that different plasma processing imparts on milk through volatile components analysis. Cow milk was subjected separately to two plasma treatments (plasma bubbling and low‐pressure plasma) and in combination. Plasma altered the milk's volatile nature in both treatments; the combination amplified the volatiles produced. The maximum of 1.23 log10 microbial reduction was obtained when plasma treatments were combined together; however, the microbial count had less impact on volatile changes in the milk. Whereas, an increase in carbonyl (2.42 to 8.18 n mol/ml) and malondialdehyde (0.337 to 0.562 mg MDA/l) contents were highly correlated with the volatile changes in the milk. Overall, the type of plasma application into milk was observed to be an important parameter for increasing the efficiency of the processing; combining two plasma treatments produced a positive synergistic effect in microbial reduction; however, it increased the oxidation of milk. Novelty impact statement This study focuses on the investigation of the impact of different cold plasma application and its combination on milk. Though, there are many studies on combination of plasma with other treatments, to the best of our knowledge this is the first study to combine two plasma processing methods (plasma bubbling and low‐pressure plasma). It helps in understanding which plasma application has more impact and also their synergistic effect on milk with the aid of volatile compound, microbial, and oxidative analysis.

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