UV as an alternative to pasteurization: disinfection of low-light-transmittance liquids
Pasteurization has been widely used in liquid foods such as dairy products and juice.
As a heat treatment technology, pasteurization has increasingly limited inherent limitations, such as the potential damage to heat-sensitive nutrients and flavors, as well as relatively high energy consumption. These limitations have prompted the industry to seek better alternatives or supplementary solutions.
Ultraviolet (UV) disinfection, as a highly effective and environmentally friendly non-thermal sterilization technology, has garnered increasing attention.
UV disinfection physically destroys microbial genetic material, achieving sterilization and preserving the inherent sensory properties and nutritional value of foods that are considered natural, healthy, and minimally processed.
The core principle of pasteurization is to exploit the fact that pathogenic microorganisms (such as bacteria and viruses) are generally heat-sensitive. By heating food at a specific temperature below 100°C (typically 60-85°C) for a set period of time, the process kills most pathogenic and spoilage bacteria, thereby extending the shelf life and improving food safety.
Pasteurization is not complete sterilization. It aims to reduce the microbial population to a safe level and inactivate some enzymes. However, some heat-resistant microorganisms (such as certain bacterial spores) and non-pathogenic bacteria may remain.
There are two main types of pasteurization processes:
· Low-Temperature Long-Time (LTLT): For example, milk is heated to 62-65°C for 30 minutes.
· High-Temperature Short-Time (HTST): For example, milk is heated to 72-75°C for 15-20 seconds, or even shorter times at higher temperatures (such as 80-85°C).
Ultraviolet Disinfection as an Alternative to Pasteurization
Ultraviolet disinfection has been widely used in the treatment of drinking water and water used in food and beverage production, serving as an effective alternative or important supplement.
For heat-sensitive products such as juice, tea, and plant-based protein beverages, UV disinfection, as a non-thermal sterilization technology, has the potential to preserve the product's original flavor, color, and nutritional content.
Traditional pasteurization can lead to the loss of heat-sensitive nutrients such as vitamin C and alter the flavor of juice, but UV treatment has the potential to avoid these problems.
Low-transmittance liquid disinfection solutions: Juice clarity, color, pulp content, suspended particulate matter, and sugar and acid concentrations all affect the penetration depth and effective dose of UV light.
For example, darker juices or those containing higher amounts of suspended matter absorb and scatter UV light more strongly, resulting in reduced sterilization effectiveness.
Therefore, specialized UV reactor designs (such as thin-film flow, turbulent flow technology, or optimized lamp layout) are often required to ensure uniform UV dose distribution throughout the entire liquid flow and achieve the required sterilization threshold.
In addition, the optimal UV treatment parameters (dosage, flow rate, etc.) for different types of juice require extensive experimental verification.
Killing Efficiency Against Common Pathogens and Spoilage Organisms:
Assuming sufficient UV dose, UV disinfection has a good killing effect on a wide range of microorganisms, including bacteria, viruses, yeasts, and fungi. Its effectiveness depends on UV intensity, exposure time, UV transmittance of the liquid, and the sensitivity of the microorganisms themselves. UV disinfection can be highly effective for clear liquids.
Killing Efficiency Against Heat-Resistant Bacteria and Spores:
Bacterial spores are much more resistant to UV than their vegetative cells. Conventional UV doses have limited killing effect on spores. Effective inactivation of spores typically requires significantly higher UV doses or the use of enhanced technologies such as medium-pressure UV light.
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