Common Household Method of Utensil Sterilization: Boiling. In the modern food processing industry, food can be sterilized using both high and low-temperature methods to ensure consumer safety and health. The scientific team from Tipack Group offers users worldwide a comprehensive fresh food packaging solution that includes Shrink Film, shrink bag, Map Trays, Vsp Trays, Thermoforming Film, and more. Their core technology is the multi-layer co-extrusion high-barrier technology, providing top-notch freshness packaging solutions in one place.
Heat Sterilization Technology
Heat sterilization involves heating food to a specific high temperature and maintaining it for a certain period of time to kill harmful microorganisms, thereby extending the shelf life of the food. Heat sterilization can be categorized into three types based on the temperature used for treating the food: low-temperature sterilization (temperature ≤ 100°C), high-temperature sterilization (temperature > 100°C), and ultra-high-temperature sterilization (temperature > 130°C).
1. Low-Temperature Sterilization
Common low-temperature sterilization techniques used in food processing include Pasteurization and Boiling Water Bath Sterilization.
(1) Pasteurization: Pasteurization involves heating food to 62°C for 30 minutes to eliminate heat-sensitive microorganisms. It is commonly used to sterilize milk and raw materials for brewing. Pasteurization is widely applied, with stable technology, simplicity, safety, and low cost. It preserves the original nutritional content and inherent flavor of the food to a great extent. However, foods sterilized through pasteurization may have a relatively short shelf life due to the presence of residual microorganisms.
(2) Boiling Water Bath Sterilization: Boiling water bath sterilization uses a higher temperature than Pasteurization and ensures even heat distribution, reducing the amount of basic microorganisms in the product. Foods subjected to boiling water bath sterilization experience moderate protein denaturation, retaining nutritional components and maintaining higher sensory quality. Nevertheless, this method does not completely eradicate bacterial spores, fungal spores, and heat-resistant bacteria in the food. Under favorable conditions, these surviving microorganisms can grow and reproduce, leading to food spoilage.
(3) Double Sterilization Method and Two-Step Three-Times Sterilization Method: In the double sterilization method, the food is boiled in water for 30 minutes, rapidly cooled, and then cultured at 37°C for 24 hours to allow certain surviving spores to germinate. Afterward, the food is boiled again for 30 minutes to kill these microorganisms.
For the two-step three-times sterilization method, food is subjected to boiling water sterilization for 30 minutes, and any remaining spores that haven't germinated are cultured at 37°C for 24 hours. Subsequently, the food is heated to 90-100°C for the third round of sterilization. By using this method under normal pressure, including two-step sterilization and three rounds of temperature variation, it is possible to effectively sterilize all microorganisms, including spores, in the food, achieving a near-sterile state. Generally, this method can preserve meat products at room temperature (25°C or below) for six months without spoilage when the external packaging is intact. If stored at low temperatures, the shelf life of the food can be even longer. This method is commonly used for sterilizing pre-prepared dishes, such as braised beef and diced black pepper beef.
2. High-Temperature Sterilization
High-temperature sterilization refers to heating food to at least 115°C for a minimum of 20 minutes. This method can effectively kill the vast majority of microorganisms and significantly extend the product's shelf life. However, the higher sterilization temperature can result in the softening of product texture and loss of nutrients, significantly impacting its taste and quality. Moreover, high temperatures can cause the decomposition of heat-sensitive flavor compounds in the food, leading to undesirable flavors, often referred to as "cooked" taste, especially in meat products like sausages. High-temperature processing can also cause protein denaturation and accelerate fat oxidation, resulting in a decline in the visual appeal of the food.
Due to these potential drawbacks, high-temperature sterilization is generally used for ready-to-eat packaged foods such as dried tofu and vegetarian sausages. It is not suitable for fresh meat and its products.
3. Ultra-High Temperature (UHT) Instant Sterilization Technology
Ultra-high temperature (UHT) instant sterilization technology involves heating food at temperatures ranging from 135°C to 150°C for several seconds or tens of seconds. This method achieves excellent sterilization results, approaching or meeting the requirements of complete sterilization, while causing minimal damage to the nutritional content of the food – typically preserving over 95% of the nutrients. UHT sterilization equipment is often used in conjunction with aseptic packaging techniques and is commonly applied in the production of beverages, soy milk, fruit juices, and alcoholic beverages, among other liquid foods.
Cold Sterilization Technology
With the advancement of technology, people's demands for food quality have been increasing. They desire food to retain its freshness, sensory appeal, and nutritional quality. As a result, cold sterilization technology has emerged.
1. Low-Temperature Plasma Technology
Cold sterilization is in contrast to high-temperature sterilization. Compared to traditional heat treatment methods, low-temperature plasma technology offers several advantages, including lower processing temperatures, minimal nutrient damage, maximum preservation of product quality, no toxic by-products, and rapid effectiveness.
Plasma is an ionized gas containing various active substances, such as electrons, free radicals, and ions. When these substances act alone or in combination on microorganisms, they can achieve sterilization. This method is commonly used for the sterilization of heat-sensitive foods like apple juice and carrot juice.
2. High-Pressure Processing (HPP) Technology
High-pressure processing (HPP) technology targets non-covalent bonds like hydrogen bonds, ionic bonds, and hydrophobic interactions in large biomolecules, leaving small molecular compounds such as vitamins, pigments, and flavor substances unaffected. This helps preserve the original nutrients, color, and flavor of the food. HPP is effective in killing yeast, molds, viruses, and bacteria in their vegetative forms and is widely used in the preservation of products like jam and seafood.
3. Microwave Sterilization Technology
Microwave sterilization is a new type of sterilization method known for its rapid, efficient, safe, and preserving advantages. The principle of microwave sterilization is that under a certain intensity of microwave field, the spatial structure of proteins in food is damaged or altered, leading to protein denaturation and loss of biological activity. Additionally, when microwaves penetrate the food, water molecules in the food continuously change their polarity, causing a rapid increase in the food's temperature, which effectively kills bacteria. Microwave sterilization is commonly used for sterilizing pickled vegetables, fruit wines, and other food products.
4. Ultraviolet (UV) Sterilization Technology
Ultraviolet light is an invisible light wave beyond the violet end of the spectrum, hence called ultraviolet. Its principle is that when microorganisms absorb ultraviolet energy, it causes the breaking of chains between DNA (deoxyribonucleic acid) and nucleoproteins, leading to cross-linking destruction of nucleic acids and proteins, resulting in bacterial death. UV sterilization can effectively suppress the number of microorganisms in the product while preserving the freshness and nutritional content of the food to the maximum extent. Products like shredded meat and fruit/vegetable juices often use this technology for sterilization.
In the modern food processing industry, suitable sterilization techniques, preservation methods, and anti-corrosion measures are chosen based on the characteristics of different foods, building a "barrier" to prevent food spoilage and deterioration. These measures act as barriers against microorganisms, extending the shelf life of food and reducing food safety risks.
