Critical Process Filtration Blog

Assuring Bacteria-Free Juice Products

Posted by Critical Process Filtration Marketing on Oct 31, 2017 8:24:32 AM



The microorganisms that cause fruit degradation occur naturally and are present in every juice processing operation. Some juice products are pasteurized to kill these organisms and help prevent spoilage. However, the heat used may adversely affect the flavor and overall quality of other juices. Also, not all spoilage organisms are killed by the pasteurization process, so additional methods need to be considered for removing spoilage organisms from juice products.

There are many sources of spoilage microorganisms. The raw juice often carries environmental bacteria, the most common of which are those that cause the fruit to decay in nature. Other bacteria could be carried by sweeteners, flavor enhancers and even by water used as an ingredient or for container washing.

Organisms of Concern

Heat-resistant organisms can enter the process system with outside ingredients. Sugar, for example, can be a carrier of the spores of Bacillus and other species. Molds and yeasts are found almost everywhere in the environment and can be carried in by ingredients or enter the process somewhere in the plant.

Alicyclobacillus species are the organisms most mentioned as resistant to pasteurization, though other Bacillus species may also cause spoilage issues and resist heat inactivation. These “thermo-acidophilic bacteria,” or TAB, are the subjects of many articles in the industry press. Two articles describing these heat-resistant organisms can be found in the References at the end of this summary.

Heat resistant molds, including Byssochlamys, Paecilomyces, Eupenicillium, Talaromyces and Eurotium have also been found in juices after heat treatment. The schematic below shows a simplified fruit juice process with multiple potential sources of organisms and locations for filters to help control or remove them.

Juice Filtration Schematic2.jpg

Choosing the Right Filter

The most critical filter in the schematic is the final, “Sterilizing” filter (housing 4) - the one that removes the target organisms. Molds are larger than 1 micron and can be removed by most membrane based filters. Either 0.45 micron or 0.22 micron membranes will capture all Alicyclobacillus spores, which are the form of the bacteria found in acidic fruit juices. Processors may choose the smaller pore size to assure capture of all bacteria, including the vegetative forms of some species, but there is a risk that some flavor or aesthetic elements of the fruit juice will also be captured by membranes with 0.22 micron pores. For that reason, 0.45 micron membranes are used by most juice processors.

Read more about bacteria removal in juice production in the Application Summary - "Removing Heat Resistant Molds and Bacteria During Juice Production". Additional reading can be found in the references at the end of the summary.

Topics: Final Filtration, Bacteria Reduction/Removal, Sterilizing Filtration, Juice Processing, Beverage Processing, How-To, Problem Solving

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