Non-thermal plasma application for increasing food quality and longer storage
In modern day, at all levels of society, health consciousness has increased and the demand for fresh, nutrient rich food has multiplied exponentially. Many deceases are inflicted upon our society by harmful bacteria, viruses, parasites and dangerous chemicals. Some examples of the deceases are diarrhea and cancer. One way to combat this problem is to use a new technology called non-thermal plasma which has positive effects on food during processing and storage. This technology has created some buzz in the food industry due to its useful effects on processed foods. It is also useful in increasing the storage time for the food that has been treated by this method. This method is highly effective because it can disinfect, decontaminate, increase shelf life, etc. without introducing any toxicity in the food. The technology is quite promising if it can be applied in a large scale in food processing plants. Maintaining plasma consistency throughout the process is crucial when the technology is applied on a big scale food industry. This is a green technology that can be applied to preserve the purity of food products and improve the sensory qualities of food. One can reduce the activities of spore, enzymes and toxins in the food by utilizing this technology. Food-borne illnesses are introduced by micro-organisms that typically appear in high protein food products and can resist a wide range of PH and temperatures. These micro-organisms can eventually cause discoloration, change in texture and odor in the food products.
Figure 1 shows the causes of contamination of food by micro-organisms.
Figure 1: Bacteria, Fungus, molds and yeasts are responsible for foodborne deceases
Government agencies working in the food sector have been under pressure to come up with regulatory standards to ensure microbial free foods. This demand has opened the door for new innovations. Various innovative technologies have been developed to preserve food products safely and efficiently. It is also recommended combining various food preservation technologies to increase the food product safety and increase of their shelf life. Although it is possible to use chemical food preservatives which are anti-bacterial and can increase the shelf life of food products, these chemical agents are not ecologically friendly. They may also be dangerous as far as seed gemination and pesticide free growth are concerned. The increase in the food product shelf life by these agents, comes at a cost. Hence, food sectors are opening their eyes to new innovative technologies which can inactivate microorganism and microbes without having any side effects. Cold Plasma (CP)technology is one such technology which can destroy micro-organisms such as bacteria, viruses, fungi, etc. by using a highly charges mix of gases and matter. This technology which is also called non-thermal plasma technology is very efficient in maintaining the quality and safety of food products and increase the shelf life since it does not employ chemical agents. It is a green technology used to promote consumer health.
What is plasma?
The term plasma was introduced by the America Physicist Irving Langmuir. It is basically a mix of ionized gas which contains negatively charged electrons, positively charged ions, gas atoms, free radicals and molecules in ground or excited states. Plasma can also be further divided into thermal and non-thermal plasma. The latter which is the focus of this article happens when the plasma density is low and there is a big temperature difference between the electrons and heavier particles, the temperature of electrons being much higher than that of heavier particles. Non-thermal plasma which has low temperature and is highly effective in deactivating micro-organisms, is highly suitable to be used in the food industry. Various mechanisms of generating cold plasma are mentioned in this article but only one of them, namely atmospheric pressure Dielectric Barrier Discharge is discussed in detail.
Methods of generating cold plasma
Figure below shows the mechanism of atmospheric pressure dielectric barrier discharge.
Figure 2: Atmospheric pressure dielectric barrier discharge
Dielectric Barrier Discharge (DBD) is produced by maintaining a high voltage between two metals electrodes [Reference 1]. The metal electrodes are quoted by dielectric material such as ceramic and there is big distance between the two of them which can be varied. There are some common parameters of operation such as frequency, current, gas pressure and pulsed direct current which can be controlled by voltage amplitude. This method of plasma generation is very versatile and has many applications due to different electrode designs and choices of dielectric material used [Reference 2].
Other methods of producing CP are Atmospheric Pressure Plasma jet, Corona Discharge, and Microwave Plasma. For further information on these other methods, one can refer to [Reference 1].
Non-thermal plasma in the food industry
Cold plasma technology has been used in several areas in the food industry and the following categories can be mentioned in this article.
- Beverages
- Cereals
- Meat and Poultry
- Spices
Beverages
The following examples can be given for the use of CP in beverage industry.
- Decrease in anti-oxidant activity and microbial content plus increase in free fatty acids in tender coconut water
- Reduction in survival rate of spores in Kiwi fruit juice
Cereals
- Plasma jet was used successfully for microbe detoxification in particulate rice germs.
- Plasma treatment significantly reduced microbe count and yeast population improved in millet grains which helped grain safety and shelf life.
Meat and Poultry
- DBD method was used in chicken fillets. The surface treatment significantly reduced microbial activity and PH values
- Plasma treatment removed bacteria in puffer fish
Spices
- When red pepper powder was treated with CP, it was found that e-coli was eliminated and the dried peppermint quality was also preserved
- CP was used in treatment of spices and aromatic herbs which are difficult to process under high temperatures.
- CP treatment was used to destroy salmonella in black pepper corns
- Microwave generated plasma treatment deactivated molds in spices like black pepper seed and extended its shelf life
Conclusion
CP technology has a huge potential in becoming the most effective method to deactivate micro-organism in food industry and cause an increase in their shelf life. The absence of chemical agent in this treatment is a big advantage that ensures safety and effectiveness of the treatment.
References
- Application of non-thermal plasma technology for enhancing food processing and storage: A Review, U Vaka and MC Ramkumar, Food chemistry advances, 2024.
- Plasma treatment: An alternative and sustainable green approach for decontamination of mycotoxin in dried food products. Ranjan, R., Gupta et al. Journal of Agriculture and Food Research, 14 (2023).