Essential differences in sterilization principles
Traditional pasteurization mainly achieves sterilization through high temperature. Taking milk as an example, the common pasteurization process is to heat milk to 63℃ for 30 minutes (low temperature long time method) or 72℃ for 15 seconds (high temperature short time method). High temperature will destroy the protein structure of microorganisms and make them inactive. However, this method has limited inactivation effect on high temperature resistant spore bacteria (such as Clostridium botulinum), so it needs to be combined with refrigerated storage to extend the shelf life.
However, ultra-high pressure sterilization technology (HPP) uses a completely different principle. Ultra-high pressure sterilization equipment places food in a high pressure environment of 100-600MPa for several minutes through water or oil medium. High pressure destroys the cell membrane and genetic material of microorganisms and inhibits enzyme activity. Since it does not rely on high temperature, HPP can retain the nutrients and natural flavor of food to the maximum extent while killing microorganisms. For example, the vitamin C content of Pretreated juice after sterilization can be more than 30% higher than that of pasteurized juice.
Scientific comparison of microbial inactivation efficiency
Difference in logarithmic reduction value
The sterilization effect is usually expressed in logarithmic reduction value (Log Reduction), which is the power of 10 in the reduction of the number of microorganisms. Studies have shown that ultra-high pressure sterilization can achieve a Log Reduction of 6-7 for Escherichia coli, while traditional pasteurization can only achieve 3-4. For the more stubborn Listeria, HPP can achieve a killing effect of more than 5Log at 400MPa for 5 minutes, while pasteurization requires the temperature to be raised to above 75℃ to achieve a similar level.
Spore inactivation ability
Spores are the dormant state of microorganisms, and traditional pasteurization is difficult to completely inactivate. For example, it takes 12 minutes at 121°C to kill Clostridium botulinum spores, while UHP sterilization can achieve the same effect in 3 minutes at 600MPa. This allows the shelf life of HIP-sterilized foods to be extended to 30–90 days at room temperature, while pasteurized products usually require refrigeration and have a shorter shelf life.
Impact of technical characteristics on efficiency
Differences in temperature sensitivity
The high temperatures of traditional pasteurization can cause heat-sensitive ingredients (such as enzymes and vitamins) to be inactivated. For example, in tomato juice, pasteurization causes a loss of about 25% of lycopene, while UHP sterilization only loses 5%. This difference is more obvious in dairy products, where Pretreated yogurt can retain more probiotic activity, while the probiotic survival rate of pasteurized yogurt is less than 50%.
Treatment uniformity
The pressure transmission of UHP sterilization technology is isotropic and can act evenly on every corner of the food. In contrast, traditional pasteurization relies on heat conduction, which may lead to insufficient local temperature. For example, when processing block foods, HPP ensures that the center and the surface are sterilized simultaneously, while pasteurization may require extended processing time, affecting product quality.
Comparison of actual application scenarios
Advantages of ultra-high pressure sterilization
Ultra-high pressure sterilization equipment is widely used in products such as juice, jam, and ready-to-eat meat. HPP sterilized ready-to-eat chicken breast can be stored for 60 days at room temperature, and the taste is not significantly different from fresh meat.
Applicable scenarios for traditional pasteurization
Pasteurization is more suitable for liquid foods, especially products that need to maintain a specific texture. Although pasteurized milk has a shorter shelf life, it can retain more cream aroma. In large-scale production, traditional pasteurization equipment has a lower cost and can process tens of thousands of liters per hour, which makes it still dominate the dairy industry.
By comparison, it can be seen that ultra-high pressure sterilization technology has significant advantages in microbial inactivation efficiency and nutrient retention, but the equipment cost is relatively high. Although traditional pasteurization has limitations, it still has its value in terms of cost and applicability. When choosing sterilization technology, it is necessary to comprehensively consider product characteristics, cost budget and market demand to achieve the best sterilization effect and economic benefits.