Ozone Treatment as a Food Preservation Technique

What is Ozone Treatment?

• Ozone treatment is a process used in food preservation to extend the shelf life of food while maintaining its natural quality. It offers a viable alternative to traditional preservation methods by harnessing the quick decomposition properties of ozone, with minimal residual effects.
• Ozone, often referred to as triatomic oxygen (O3), is a highly reactive form of oxygen. It possesses strong oxidizing power and is capable of effectively inactivating microorganisms. Due to its natural disinfectant properties, ozone has gained recognition as a valuable tool in food technology.
• The United States Food and Drug Administration (FDA) accepted ozone as a Generally Recognized as Safe (GRAS) substance for water treatment in 1982, and later for use in food in 1997. This acknowledgment further reinforced ozone’s credibility as a safe and reliable method for various applications.
• In water treatment, ozone has emerged as a superior alternative to conventional chemical treatments such as chlorination. Ozone generators are employed to produce ozone at controlled and safe concentrations. The most common method for commercial ozone production is through corona discharge, where oxygen (O2) is broken down into highly reactive singlet oxygen. This singlet oxygen then reacts with additional oxygen molecules (O2), resulting in the formation of ozone (O3).
• By utilizing ozone treatment in food preservation, the aim is to inhibit the growth of microorganisms that can cause spoilage, thereby extending the product’s shelf life. Ozone’s strong oxidizing properties effectively target and neutralize bacteria, viruses, molds, and yeasts, which are common culprits in food deterioration.
• One of the key advantages of ozone treatment is its ability to achieve microbial inactivation without leaving significant chemical residues. Unlike some chemical treatments, ozone decomposes rapidly, leaving no harmful or undesirable by-products. This characteristic is particularly desirable in food preservation, as it ensures that the treated food retains its natural qualities and flavors.
• Overall, ozone treatment offers a promising solution for extending the shelf life of food while preserving its natural integrity. By harnessing ozone’s powerful oxidizing properties, food producers can reduce reliance on traditional preservation methods that may introduce unwanted chemicals or alter the food’s quality. With proper implementation and adherence to safety guidelines, ozone treatment holds great potential in the field of food technology.

Properties of ozone

Ozone, with the chemical formula O3, is a molecule consisting of three oxygen atoms bonded together. It possesses several unique properties that contribute to its wide range of applications and effects:

1. Strong oxidizing agent: Ozone is a powerful oxidant, meaning it readily reacts with other substances by transferring oxygen atoms. It has a high oxidation potential, making it effective at breaking down organic and inorganic compounds. This property makes ozone useful for disinfection, odor control, and chemical degradation.
2. Unstable: Ozone is a relatively unstable molecule and readily decomposes back into oxygen. This decomposition occurs naturally over time or can be accelerated by factors such as heat, ultraviolet light, or the presence of certain contaminants. The instability of ozone limits its long-term storage and requires on-site generation when needed.
3. Highly reactive: Ozone reacts rapidly with a wide range of substances. It can react with organic materials, such as bacteria, viruses, and odor-causing compounds, as well as inorganic substances like metals and certain gases. This reactivity allows ozone to effectively destroy pathogens and remove unwanted contaminants.
4. Selective reactivity: While ozone is a potent oxidizing agent, it exhibits selective reactivity, meaning it targets specific compounds while sparing others. For example, ozone is more reactive towards unsaturated carbon-carbon double bonds and certain functional groups, making it effective in breaking down organic pollutants. This selectivity contributes to the versatility of ozone in various applications.
5. Effective disinfectant: Ozone is a broad-spectrum antimicrobial agent that can kill bacteria, viruses, fungi, and other microorganisms. It attacks the cell walls and membranes of microorganisms, leading to their destruction. Ozone’s disinfection capabilities make it valuable in water treatment, air purification, and surface sanitation.
6. Strong odor: Ozone has a distinctive, pungent odor that is often described as “fresh” or “clean.” This odor is noticeable even at low concentrations, and its detection threshold is lower than the recommended safety limits for human exposure. Therefore, ozone’s odor serves as a warning sign and indicates the presence of ozone-generating equipment or ozone-rich environments.
7. Environmental effects: Ozone plays a crucial role in Earth’s atmosphere. In the stratosphere, the ozone layer absorbs a significant portion of the sun’s ultraviolet (UV) radiation, protecting life on Earth from harmful UV rays. However, at ground level, ozone is a pollutant and a component of smog. High concentrations of ground-level ozone can have detrimental effects on human health and ecosystems.

These properties make ozone a valuable tool in various industries, including water treatment, air purification, food preservation, and industrial processes. However, caution must be exercised when handling and working with ozone due to its reactivity and potential health risks at high concentrations.

Different Forms of Ozone

Ozone, a powerful oxidizing agent, exists in various forms depending on its physical state and how it is utilized. The two main forms of ozone commonly encountered are gaseous ozone and aqueous ozone.

1. Gaseous ozone: Gaseous ozone refers to ozone in its gaseous state. It is produced by exposing oxygen molecules (O2) to an electric discharge or ultraviolet radiation, causing the oxygen molecules to break apart and form ozone molecules (O3). Gaseous ozone finds application in various industries, particularly in storage treatment. One example of its use is in the decontamination of eggshells. Gaseous ozone is employed to reduce the risk of spoilage of eggs by eliminating potential pathogens on the shell’s surface. Additionally, it is used to preserve spices, grains, beans, and other food items by inhibiting microbial growth and extending their shelf life.
2. Aqueous ozone: On the other hand, aqueous ozone refers to ozone that is dissolved in water, creating a solution containing ozone bubbles. The production of aqueous ozone involves passing ozone gas through water, allowing it to dissolve and form a solution. Aqueous ozone is primarily utilized as a surface disinfectant due to its strong antimicrobial properties. For instance, in the food industry, it is employed to reduce the microbial load on fish fillets. By treating the fillets with aqueous ozone, the number of harmful microorganisms present on the surface can be significantly reduced, ensuring a safer and longer-lasting product.

Both gaseous ozone and aqueous ozone have unique properties that make them valuable in different applications. Gaseous ozone’s ability to penetrate various materials and its effectiveness in inhibiting microbial growth make it suitable for storage treatment. Aqueous ozone, on the other hand, is advantageous for surface disinfection due to its ability to directly come into contact with the target area and effectively eliminate pathogens.

In summary, gaseous ozone and aqueous ozone represent two distinct forms of ozone that find practical use in different contexts. Gaseous ozone is utilized for storage treatment purposes, such as decontaminating eggshells and preserving food items. Aqueous ozone, on the other hand, is employed as a surface disinfectant, exemplified by its application in reducing the microbial load on fish fillets. These different forms of ozone contribute to various industries by offering efficient and environmentally friendly solutions for decontamination and preservation.

Process of Formation of Ozone

Ozone, with its chemical formula O3, is formed through a series of reactions involving oxygen molecules. The process can be summarized as follows:

1. Addition of a free radical of oxygen to molecular oxygen: The formation of ozone begins with the presence of a free radical of oxygen (O) in the atmosphere. This free radical can be generated through various natural processes such as exposure to ultraviolet (UV) radiation or electrical discharges during thunderstorms.
2. High voltage alternating current splits oxygen molecules into atoms: In the presence of a high voltage alternating current, molecular oxygen (O2) can be split into individual oxygen atoms. This process is known as electrical discharge or corona discharge. The high voltage provides the energy needed to break the stable O2 bonds, resulting in the formation of highly reactive oxygen atoms.
3. Atoms of oxygen combine with other oxygen molecules and form ozone (O3): The highly reactive oxygen atoms generated in the previous step quickly react with nearby oxygen molecules (O2). This reaction leads to the combination of one oxygen atom with one oxygen molecule, resulting in the formation of ozone (O3). The reaction can be represented as follows:O + O2 -> O3The newly formed ozone molecules are stable and can exist as a gas in the Earth’s atmosphere.

It’s important to note that the formation of ozone is a dynamic process that occurs continuously in the Earth’s atmosphere. Natural processes, such as UV radiation from the Sun and electrical discharges in thunderstorms, contribute to the production of ozone. Additionally, human activities, such as industrial processes and the burning of fossil fuels, can also release pollutants that can lead to the formation of ozone, particularly in the lower atmosphere, where it can contribute to the formation of smog.

Overall, the formation of ozone involves the addition of a free oxygen radical to molecular oxygen, followed by the combination of oxygen atoms with other oxygen molecules to create ozone. This process plays a vital role in maintaining the ozone layer in the stratosphere, where it acts as a protective shield against harmful UV radiation, while also having implications for air quality and pollution in the lower atmosphere.

Mode of action of Ozone in food treatment

Ozone, with its strong oxidizing properties, is widely used in food treatment processes due to its ability to effectively destroy microorganisms and improve food safety. The mode of action of ozone in food treatment involves several key mechanisms:

1. Destructive oxidative reactions: Ozone acts as a powerful oxidant, leading to destructive oxidative reactions in microorganisms and food components. It reacts with lipids, proteins, nucleic acids, and other cellular components, causing chemical changes and disrupting their structure and functionality. The oxidative reactions initiated by ozone can break down complex molecules, including lipids and proteins, and alter the genetic material within microorganisms, rendering them unable to survive or reproduce.
2. Protein degradation and modification of cellular structures: Ozone targets proteins, which are essential building blocks of microorganisms and play a crucial role in their structure and function. Ozone treatment leads to protein degradation, breaking down the peptide bonds that hold proteins together. This degradation disrupts microbial metabolism, impairs enzymatic activity, and interferes with essential cellular processes. Additionally, ozone can modify the structure of cellular components, such as enzymes and receptors, which further compromises the functionality and viability of microorganisms.
3. Damage to spore inner membrane due to oxidization: Ozone treatment can also damage the inner membrane of microbial spores. Spores are dormant and highly resistant structures produced by certain microorganisms, capable of withstanding harsh conditions. Ozone, being a strong oxidant, can penetrate the spore structure and oxidize the inner membrane. By damaging the membrane, ozone prevents the spores from germinating and becoming active, thus inhibiting their ability to cause contamination or spoilage.

The mode of action of ozone in food treatment is particularly advantageous due to its selective reactivity. Ozone is highly reactive towards unsaturated carbon-carbon double bonds and certain functional groups present in microorganisms, making it effective in targeting and destroying these contaminants while sparing other components of the food matrix.

It’s important to note that the effectiveness of ozone treatment depends on various factors, including concentration, contact time, and environmental conditions. Optimal ozone concentration and exposure time need to be carefully determined to ensure efficient microbial inactivation while minimizing potential negative effects on food quality.

In summary, ozone’s mode of action in food treatment involves destructive oxidative reactions, protein degradation, modification of cellular structures, and damage to spore inner membranes. These mechanisms collectively contribute to the decontamination and preservation of food products, enhancing their safety and extending their shelf life. Ozone treatment provides a valuable tool in the food industry

Application of Ozone Treatment

Ozone treatment has a wide range of applications in various industries, particularly in the field of disinfection and preservation. Here are some key applications of ozone treatment:

1. Disinfection of production areas, plant equipment, and surfaces: Ozone is highly effective in disinfecting production areas, plant equipment, and surfaces from microorganisms. It can destroy bacteria, viruses, fungi, and other pathogens that may be present on surfaces, reducing the risk of contamination and ensuring a safe working environment.
2. Killing spores of Bacillus and Clostridium species: Ozone treatment has shown efficacy in killing spores of Bacillus and Clostridium species, which are known to be highly resistant to many disinfectants and traditional sterilization methods. Ozone’s strong oxidizing properties can penetrate and damage the spore structure, preventing germination and subsequent growth.
3. Inhibition of fungal growth in fruits and vegetables: Ozone treatment is effective in inhibiting fungal growth in fruits and vegetables. Fungi can cause spoilage and reduce the shelf life of fresh produce. Ozone treatment helps to control fungal growth by inhibiting spore germination and destroying existing fungal cells, thereby extending the freshness and quality of the treated fruits and vegetables.
4. Decontamination of eggshells: Gaseous ozone is employed to decontaminate eggshells, reducing the risk of microbial contamination and spoilage. Ozone can penetrate the porous surface of the eggshell, effectively destroying bacteria and other microorganisms present on the shell. This treatment helps in improving the safety and shelf life of eggs.
5. Reduction of natural microbiota in fish products: Ozone treatment is used to reduce the level of natural microbiota in fish products. By applying ozone to fish surfaces or using ozone-treated water during processing, the microbial load on the fish can be significantly reduced, ensuring improved food safety and extended shelf life.
6. Reduction of microbial load in spices, grains, beans, etc.: Ozone treatment is effective in reducing the microbial load in various food commodities such as spices, grains, beans, and other dry goods. Ozone can inhibit the growth of bacteria, molds, and yeasts, thereby preserving the quality and freshness of these products for longer periods.

These applications demonstrate the versatility and effectiveness of ozone treatment in the food industry. Ozone’s powerful disinfection properties, broad-spectrum antimicrobial activity, and selective reactivity make it a valuable tool for ensuring food safety, extending shelf life, and maintaining the quality of various food products.

Advantages of Ozone Treatment

Ozone treatment offers several advantages in various applications, including disinfection, preservation, and odor control. Here are the key advantages of ozone treatment:

1. High antimicrobial activity: Ozone exhibits high antimicrobial activity, being approximately 3000 times faster than chlorine at killing microorganisms. It is a potent oxidizing agent that can effectively destroy bacteria, viruses, fungi, and other pathogens. This high antimicrobial activity makes ozone treatment highly effective in decontamination and ensuring food safety.
2. Fast decomposition to simple oxygen: Ozone rapidly decomposes into oxygen after its intended application, leaving no residual traces or harmful by-products. Unlike other chemical disinfectants, ozone does not leave behind chemical residues or require additional steps for removal. Once ozone has performed its antimicrobial function, it breaks down into simple oxygen molecules, reducing any potential environmental impact.
3. No waste generation: Ozone treatment does not generate any waste products that require special disposal measures. Since ozone decomposes back into oxygen, there is no accumulation of waste or harmful by-products from the treatment process. This makes ozone treatment environmentally friendly and reduces the burden on waste management systems.
4. Lower energy input compared to other techniques: Ozone treatment generally requires lower energy input compared to other thermal and non-thermal techniques used for disinfection and preservation. While thermal methods such as pasteurization or sterilization often require higher energy consumption, ozone treatment can achieve comparable or superior results with less energy expenditure. This energy efficiency makes ozone treatment a cost-effective option for various industries.
5. Eco-friendly and economically feasible: Ozone is considered environmentally friendly as it does not contribute to the depletion of the ozone layer when used responsibly. It is produced on-site using oxygen, eliminating the need for transportation or storage of hazardous chemicals. Additionally, ozone treatment is economically feasible due to its efficiency, lower energy requirements, and the absence of waste generation, resulting in potential cost savings for businesses.

Disadvantages of Ozone Treatment

While ozone treatment offers numerous advantages, there are some potential disadvantages and limitations that need to be considered. Here are the key disadvantages of ozone treatment:

1. Hazardous at high concentrations: Ozone is a powerful oxidizing agent, and at high concentrations, it can be hazardous to human health. Direct inhalation of high levels of ozone can irritate and damage the respiratory system, leading to throat and nasal problems. Therefore, it is crucial to ensure proper ventilation and appropriate ozone concentration levels to prevent potential health risks.
2. Decomposes quickly and cannot be stored: Ozone is an unstable molecule that decomposes rapidly. It has a relatively short half-life, meaning it breaks down into oxygen molecules within a short period. This property makes it unsuitable for long-term storage or transportation. Ozone must be generated on-site using specialized equipment, limiting its availability to specific locations and requiring continuous production when needed.
3. Reaction with proteins and fats: Ozone can react with proteins and fats present in food or carcass surfaces before inactivating microorganisms. This can lead to the formation of potentially harmful by-products. It is essential to carefully control the ozone concentration and exposure time to minimize adverse reactions and ensure food safety.
4. Limited penetration and contact time: Ozone has limitations in terms of its penetration into certain materials or surfaces. Its effectiveness is influenced by factors such as the surface texture, organic matter present, and the presence of biofilms. In some cases, limited penetration and contact time may result in incomplete microbial inactivation or reduced effectiveness against certain microorganisms.
5. Equipment complexity and maintenance: Ozone treatment systems require specialized equipment for its generation and application. These systems can be complex and require regular maintenance and calibration to ensure optimal performance. Adequate training and expertise are necessary for the safe and effective operation of ozone treatment equipment.

FAQ

References

1. R. Pandiselvam, S. Subhashini, E.P. Banuu Priya, Anjineyulu Kothakota, S.V. Ramesh & S. Shahir (2019) Ozone based food preservation: a promising green technology for enhanced food safety, Ozone: Science & Engineering, 41:1, 17-34, DOI: 10.1080/01919512.2018.1490636.
2. Potter NP (1987), Food Science, CBS Pub, India.
3. Rahman MS (1999), Handbook of Food Preservation, Marcel Dekker, Inc, NY.
4. Desrosier EN (1963), The Technology of Food Preservation, AVI Publishing Company, New York.
5. Sarron E, Gadonna-Widehem P, Aussenac T. Ozone Treatments for Preserving Fresh Vegetables Quality: A Critical Review. Foods. 2021 Mar 12;10(3):605. doi: 10.3390/foods10030605. PMID: 33809297; PMCID: PMC8000956.

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