Plasma is the fourth state of matter and it contains high-energy particles. Plasma is highly explored in different fields like medicine, food, etc. In the food sector, it is used as a processing tool in various foods such as milk, beverages, fruits, vegetables, etc. Cold Plasma Processing is a non-thermal method and hence its use helps prevent the adverse effects caused by thermal treatment in food processing. This article contains a brief note on the recent progress made in the application of cold plasma in food processing.
The term “plasma” was first introduced by Irving Langmuir in 1923. Plasma is an ionized gas and is known as the fourth state of matter and it is composed of electrons, atoms and molecules with a net neutral charge. In general, plasma is synthesized by applying electrical energy to gas or gas flowing between two charged electrodes. These potential differences between two electrodes results in ionization, as a result of the collision between free electron with gas molecules. The ionized gas formed is referred to as cold plasma (Laroque et al., 2022). It exhibits excellent physical and chemical properties. The high energetic electron present in plasma is capable of breaking chemical molecules like O2 and N2, etc. (Katsigiannis et al., 2022). Cold plasma is a non-thermal method of processing and is widely explored in various manufacturing industries like medical devices, textiles, automotive, aerospace, electronics, packaging materials and food industry. In the food sector, it gains much attention, owing to some of its potential advantages being low processing time, low energy utilization and operation at room temperature, which facilitates the processing of heat-sensitive products (Nikmaram & Keener, 2022).
The surface exposure of cold plasma may result in cleaning, cross-linking, polymerization, degradation and surface oxidation (Muhammad Rashidi Wahab, 2013). In the past decades, a large number of studies have been conducted on the application of cold plasma in food processing. This article focuses on the recent progress made in the application of cold plasma in food processing.
Cold Plasma in Milk Processing
Milk is traditionally processed by using the thermal method and it ensures the safety of the product. However, it may adversely affect the quality of the product. Cold Plasma Processing is a highly efficient method that can be used for milk and milk-based products. Many researchers observed a significant reduction in microbial load and enzymatic activity in cold plasma processed milk. Wang et al. (2022) studied the effect of Cold Plasma Processing of sheep milk on microbial quality and protein structure and reported a 94.2% reduction in the bacterial count by the exposure of 300 s. In addition, the extended processing time resulted in a decrease in moisture content of freeze-dried milk, pH, a* value and an increase in casein micelle size.
Plasma processing of milk increases the consistency of milk and hence lowers the viscosity. Nikmaram and Keener (2022) stated that the optimal use of cold plasma could reduce the microbial count significantly without affecting the quality of milk and milk products. However, non-optimized exposure may lead to lipid oxidation and the development of off-flavour, etc.
Cold Plasma in Beverage Processing
In addition to microbial reduction, cold plasma has a potential capacity in the inactivation of endogenous enzymes without affecting the physico-chemical properties of fruit-based beverages. Cold Plasma Processing has a beneficial impact on the phenolic compounds in fruit beverages and it enhances the functionality and retention capacity. This also stabilizes the antioxidants present in fruit beverages (Waghmare, 2021). Ribeiro et al. (2021) studied the impact of cold plasma on the techno-functional properties of the dairy beverages. They reported that Cold Plasma Treatment is suitable for retaining bioactive compounds and has better sensory acceptance and functionality over pasteurized samples. Similarly, the cold plasma processed red wine exhibited a 3.1% high content of phenolic compound than the chemically preserved one and the cold plasma treatment also reduced the biogenic amine content (Niedzwiedz et al., 2022).
Cold Plasma in Fruit and Vegetable Preservation
Cold Plasma Treatment is widely utilized for the decontamination of fresh-cut fruits and vegetables and this will also improve the shelf life of the products. Rana et al. (2020) studied the impact of cold plasma on the shelf life of packaged strawberry fruits and observed that the treatment enhanced the product’s shelf life. In addition, it also enhanced the content of chlorogenic acid, hyprin, phloretin, vanillin, gallic acid, 4-hydroxybenzaldehyde and rutin during the storage period. Cold plasma exposure of tomato pomace decreased the water contact of tomato peels and accelerated the drying of tomato fruit. This also caused a 10% increase in the extraction of phenolic compounds and also enhanced the antioxidant activity (Bao et al., 2020). Similarly, cold plasma significantly decreased the microbial load in dried peppermint. However, it increased the phenolic content and antioxidant activity (Kashfi et al., 2020). Plasma treatment can be used as the strongest antioxidant in vegetable oil preservation. Na, Mok and Lee (2020) studied the impact of cold plasma in oxidative stability of vegetable oil and reported that Hydrogen-donating compounds such as α-tocopherol and sesamol considerably decrease the degree of lipid oxidation in plasma-treated bulk oils.
Cold Plasma processing is gaining much attention in food processing, owing to its specific physical and chemical characteristics. The use of cold plasma in milk processing at optimum conditions will result in a great extent of reduction in microbial load. Further, it helps in the preservation of phenolic compound and antioxidant activity of food maybe adversely affected during heat processing.
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About the Authors:
1) Muhammed Navaf
Department of Food Science and Technology,
Pondicherry University, Puducherry 605014, India.
2) Kappat Valiyapeediyekkal Sunooj
Department of Food Science and Technology,
Pondicherry University, Puducherry 605014, India.
Email ID: firstname.lastname@example.org
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