Historically there had been little
concern about the safety of apple cider. The high acidity, typically
around pH of 4, acts as a natural barrier against most microorganisms.
However, due to multiple outbreaks of E coli O157:H7, along with Salmonella
and Cryptosporidia in the last 15 years, there has been an increased concern
about the safety of all fruit and vegetable juice products. There has been an
estimated 16,000 to 48,000 juice-related illnesses each year (NFPA 1999). The
outbreaks have exhibited the ability of E. coli O157:H7 to be sustained at low
pH and refrigerated temperatures.
This spawned somewhat of a scramble to develop better pasteurization methods and equipment in order to save the juice and cider industry. 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 is an attempt to give a brief overview of the current pasteurization methods and technology.
LTLT has been traditionally pasteurized by batch
heating at 145 F for ½ hour to 1 hour. One could see these units at small
dairies in the old days. Milk for cheese production is still done this way in
small cheese plants. This method has been replaced by high temperature short
time treatment due to the undesirable quality changes during the process.
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HTST could minimize those undesirable quality changes inherent in the LTLT method due to the much shorter processing time. Currently, HTST is the most common method for heat treatment of fruit juice, and the method underlying most pasteurizers made my Goodnature Products. In these units apple juice, for instance, is quickly heated from cold to hot (160F), held for just 15 seconds, and then rapidly cooled until cold again. The entire process can take place in less than a minute.
HPP was actually developed more than 20 years ago, originally as a method of treating seafood and meat, which cannot be thermally pasteurized. Through the use of extremely high pressures (60,000 psi) for usually about 5 minutes, the microbes are “crushed” to death.
UV Processing was originally developed in conjuction with Cornell University as a cheaper method than thermal for seasonal apple cider producers, many of whom could simply not afford a thermal pasteruizer.
PEF uses lower than thermal pasteurization temperatures, and a pulsed high voltage (25,000 Volts) across a gap through which the juice flows. This allows for lower temperatures than thermal pasteurization. As many as 2,000 pulses per second are administered. Much of the earlier development work was done at Ohio State University in the late 1980's and 1990's.
Power Ultrasound has proven to kill microbes by the application of high energy sound waves (usually 20,000 cycles per second, which is just above the normal hearing capacity of the human). The principle of ultrasound is the formation of small bubbles that, when they collapse, produce very high pressure and temperatures which can destroy microbes in the immediate vacinity of the bubble.
Hydrodynamic cavitation (HC) processing is an interesting technique wherein the juice is forced through orifices under high pressure, causing the same type of small vapor bubbles as in power ultrasound, but in this case the energy is coming from a pump rather than a sound generator.
HPH pasteurization is a promising non-thermal technology for fruit
juices. It uses high pressure pumps and high turbulence, common in traditional
homogenizers, to shear, break, and otherwise disrupt the cell walls. It is
still under development at this time
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filtration, both ultrafiltration (UF) and microfiltration (MF) are the commonly
used membrane filtration techniques for fruit juice processing. 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
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Although not considered a pasteurization method, some chemical preservatives
are widely used for the shelf-life extension of fruit juices and beverages.
Potassium sorbate and sodium benzoate are the standard preservatives. The market is trending
away from preservatives in favor of pasteurization.
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In summary, there are many new and interesting pasteurization techniques under development but as of now the only choices for a commercial juice producer are HTST, HPP, and PEF, with the majority of producers using HTST, but considerable interest in the other two.
Goodnature products manufactures and sells custom models of both HTST and PEF pasteurizers. For more information on pasteurization equipment, please send an email to firstname.lastname@example.org , call us at 1-800-875-3381, or request a quote.