And why the latest non-thermal techniques are the most interesting
Multiple outbreaks of E coli and Salmonella the last 15 years raised concerns about the safety of fresh fruit and vegetable juices and the latest generation of cold pressed juices. This created the urge to develop better pasteurization methods and equipment in order to save the juice industry and particular consumers. In the beginning there was simply thermal/heat pasteurization, but within the last decade there has been a vast number of pasteurization methods developed. Every new method is an attempt to find a better way of pasteurizing. Better, in terms of pasteurization, usually means to further extend shelf life and preserve taste, look, and other sensory aspects, while effectively killing harmful bacteria and pathogens. This article gives a brief overview of the current pasteurization methods and technologies.
|Method||Thermal / non-thermal||Time||Notes|
|Low Temperature Long Time Pasteurization (LTLT)||Thermal: 60°C – 70°C||30 – 60 minutes||Classic method with a lot of undesirable quality changes during the process.|
|High Temperature Short Time (HTST)||Thermal: 70°C – 90°C||1 minute||Widely used nowadays, but due to heating nutritional value, taste and color breaks down.|
|High Pressure Processing (HPP)||Non-thermal||Ca. 2-5 minutes||Through the use of extremely high pressures (500-600 MPa) for usually about 2-5 minutes, the microbes are “crushed” to death.|
|Pulsed Electric Field (PEF)||Non-thermal||< 5 seconds||PEF uses lower temperatures than thermal pasteurization, in combination with a pulsed high voltage (25,000 Volts) across a gap through which the juice flows. This allows for lower temperatures than thermal pasteurization. PEF 2.0 is even a non-thermal treatment.|
|PurePulse (PEF 2.0)||Non-thermal||< 2 seconds||Laminar flow treatment resulting in a much lower peak temperature treatment compared to a normal PEF treatment.|
|Ultraviolet Light (UV)||Non-thermal||< 5 seconds||A cheaper method than thermal for producers, whom could simply not afford a thermal pasteurizer. UV is a method for the lab, and not for industrial processes. UV inactivates vitamins and not sufficient microbial inactivation is obtained.|
|Membrane Filtration (Ultrafiltration and Microfiltration)||Non-thermal||< 5 seconds||Traditionally these methods are used for filtration, and are able to actually filter out microbes as well. The effectiveness depends on many factors and is generally more applicable for more processed juices that are filtered anyway, like clear apple juice, hard cider, or beer. Since these methods cause color changes and some flavor changes, they are not widely used for natural juices that contain a cloud.|
As you can see, there are many non-thermal pasteurization techniques that can be an alternative for the classic thermal pasteurization methods. The most serious alternatives for commercial juices and smoothies producers are HPP and Pure Pulse (PEF 2.0). The advantages of no loss of nutritional value, taste and flavor are nowadays for consumers of big importance. More information about these techniques you can find on the TOPwiki, which is developed by partner TOP.