Shelf-stable juices, juice beverages, and certain other beverages and concentrates are susceptible to spoilage by Alicyclobacillus (ACB), a nonpathogenic, aerobic, spore-forming, thermoaciduric bacterium typically found in soil and on harvested fruit. The spoilage occurs only in shelf-stable products because the spores do not germinate and grow in chilled and frozen juices and concentrates. It does not pose a public health risk but can cause economic damage to the juice products industry.
Unlike other spoilage microbes, the heat- and acid-loving bacterium doesn’t produce visible signs of spoilage, such as gas, turbidity, or sediment. Rather, it produces off-flavors from compounds formed during growth, primarily guaiacol, which is a chemical with an unpleasant smoky and medicinal odor or taste that is detectable by humans at leves as low as 1 ppb.
Because of ACB’s heat-resistant nature, the typical process temperatures used during pasteurization of juice products increases the likelihood of its survival in the finished product. Of several ACB species, Alicyclobacillus acidoterrestris is most closely associated with sporadic spoilage of shelf-stable juice products.
Handling the Problem
Sean Leighton, Director of Quality & Food Safety, Contract Manufacturing at The Coca-Cola Company (the no. 1 global buyer of fruit for juice consumption), said that the rate and extent of product spoilage depend on a number of factors such as product storage temperature, package type, characteristics of the growth matrix (product or ingredient), and the specific microorganism present. He added that multiple overlapping strategies should be used by companies to reduce the impact of these organisms on their business.
ACB, he said, is still a very relevant challenge for the beverage and food manufacturing industry. The primary challenge, he said, is that ACB produces heat-resistant spores that can survive pasteurization and can germinate and grow under acidified or high-acid conditions. It’s a novel challenge for the juice industry. The typical strategy for the juice industry is to provide a kill step with a thermal process because the acidity of the product can guarantee extended shelf life. But ACB and other thermoaciduric bacteria spores survive and grow in an acidified environment, resulting in a greatly reduced shelf life. The saving grace is that it can’t grow under refrigerated conditions. Susceptible products include heat-stable juice products, isotonic sports drinks, and vitamin-enhanced waters.
Randy McNeal, Technical Director at Cott Beverages Inc. (the largest private-label beverage company in the United States), said that spoilage of juice products by ACB is not as serious or widespread a problem as it was five to ten years ago because a lot of work has been done by a lot of people. Juice processors have put a lot of pressure on their ingredient suppliers, and they have responded by making changes in their process. The result is fewer positive samples on incoming ingredients. The incidence of spoilage has gone down over the years but hasn’t gone away.
A challenge now, he said, is to prevent spoilage of newer products that combine fruit juices with vegetable juices. Vegetable root crops such as carrots and beets are naturally contaminated with soil-based ACB spores and are therefore more problematic, but as the industry matures, suppliers will learn how to clean them up. Juices that are clear, such as apple juice, can be filtered to eliminate ACB spores, he said. Ultrafiltration will remove all spores, but then the trick is not to re-contaminate the filtered juice. Juices containing pulp, such as citrus juices, can’t be filtered, so sanitation of the incoming fruit is very important.
--- PAGE BREAK ---
The very slow-growing microorganism needs heat and oxygen for sporulation and growth. It takes about two to four weeks at 100°F before the undesirable flavor develops in apple juice, he said. Packaging is also an important factor. ACB won’t grow in cans because they contain very little air and the air reacts with the lining of the can. It can grow in glass bottles that have a large headspace and in PET bottles, which are not perfect oxygen barriers.
Cott requires its ingredient suppliers to provide a certificate of analysis that includes the results of ACB testing. The company does some spot-checking and sends the samples to third-party laboratories for analysis. The company also conducts taste tests as part of its normal quality control program. The off-flavor is quite difficult to detect in a normal quality control program, McNeal said, since it takes a week or two to develop. Even in inoculated trials with 10–20 bottles, only 20% of the samples may show spoilage after one week. If guaiacol is present at a low level, people are more likely to taste it than smell it. At a relatively high level, people can smell it right away, and if tasted, the flavor may linger and cause sensory fatigue.
ACB was identified as the cause of juice spoilage (initially apple juice) in 1984, and methods for detecting it and preventing it from causing spoilage have been worked on over the years by numerous researchers, companies, and associations. Since a wide variety of methods were being used for detection of ACB in fruit juices, the International Federation of Fruit Juice Producers (IFU) took the initiative to develop an internationally accepted method. The result, IFU Method No. 12 (IFUMB12), “Method on the Detection of Taint Producing Alicyclobacillus in Fruit Juices,” was issued in 2004. Revised in 2007, it provides procedures for testing (1) raw materials such as fruit concentrates, syrups, etc. where ACB is likely to be present as spores; (2) final products such as juices, drinks, sauces, and other ready-to-consume products sampled directly after heat processing; (3) final products taken from the market; and (4) process water.
Various media have been developed for the detection of ACB species. Because conventional culture methods can take up to 12 days to detect ACB and another 24 hr to confirm guaiacol production, a number of rapid methods have been developed. Flow cytometry requires a pre-incubation or enrichment step but cuts the culturing time to about 10 hr. Real-time PCR also requires a pre-incubation or enrichment step but cuts the culturing time to 48 hr. The foodproof ® Alicyclobacillus Detection Kit detects ACB species and A. acidoterrestris in the same reaction; it is available from Merck Millipore (www.merckmillipore.com) and Biotecon Diagnostics (www.bc-diagnostics.com) and will soon be launched in the United States under the EMD Millipore brand (www.emdmillipore.com). Gene probe technology uses a 48-hr pre-incubation without the need for DNA extraction and provides results within 3 hr, and the VITAlicyclobacillus Detection Test using VIT ® gene probe technology is available from Vermicon (www.vermicon.com).
Patricia Faison, Technical Director at the Juice Products Association, said that although work to overcome the economic spoilage risk of ACB in juice products continues to be done, two decades of research has given industry a better understanding of the ecology of this microorganism. Using the knowledge gained, the industry has implemented multiple processes across the supply chain to minimize risk of spoilage from ACB. Among them are use of Good Agricultural Practices during harvesting, Good Hygiene Practices during raw-fruit washing and processing, modified sanitation practices across process steps, supply-chain and distribution improvements, extensive shelf-life testing to minimize potential impacts, and implementation of testing programs. These hurdle approaches have been effective in reducing or limiting the impact of ACB in juice products.
The industry routinely tests for ACB across the supply chain using various methods to validate and verify the efficacy of their programs—such as IFU’s Method No. 12 and “Isolation of Alicyclobacillus from Fruit Juice Concentrates, Fruit Juices and Other Acid Products,” which is published in the American Public Health Association’s Compendium of Methods for the Microbiological Examination of Foods. The industry continues to search for novel risk-mitigation strategies as well as rapid detection techniques for ACB, she added. The Juice Product Association’s Technical Affairs Committee evaluates methods to detect ACB to ensure that the industry is kept abreast of current technology.
--- PAGE BREAK ---
The International Society of Beverage Technologists (ISBT)
(www.bevtech.org) is dedicated to the scientific and technical aspects of the nonalcoholic beverage industry. Its members are engaged in the science, technology, or production of soft drinks or beverages, including suppliers engaged in scientific or technical positions. Its next annual conference, BevTech ® 2013, will be held April 29 – May 1, 2013, in Fort Lauderdale, Fla. In 2008, ISBT’s Alicyclobacillus Subcommittee worked to identify and validate rapid test methods for the detection and enumeration of spoilage-causing ACB species.
The International Federation of Fruit Juice Producers (IFU)
(www.ifu-fruitjuice.com) is an association of fruit juice producers’ organizations in more than 30 countries. It serves as a nongovernmental organization, acts as an information and communication facilitator, harmonizes standards and practices for juice products manufacturers, and coordinates scientific activities to benefit the fruit juice industry. It issued its revision of its IFU Method No. 12, “Method on the Detection of Taint Producing Alicyclobacillus in Fruit Juices,” in 2007.
The Technical Committee for Juice and Juice Products
(www.tcjjp.org) is an international nonprofit organization with members from government, industry, and academia. Among its objectives are to develop and adopt accurate methods for the analysis of juices and juice products; facilitate collaborative testing of new analytical methods; facilitate acceptance of methods as official AOAC International methods; improve communication among government, academic, industrial, and private laboratory scientists working on juice research; recommend and acquire funding for development of new analytical methods; and work with the AOAC to publish a compendium of official juice and juice product analytical methods.
The Juice Products Association (www.juiceproducts.org) is an international trade association of major packers and distributors of fruit and vegetable juices, juice beverages, and other fruit products. Its members include a majority of the juice and juice beverage processors and suppliers. The organization promotes high safety and quality standards and good manufacturing and inspection practices in the production and distribution of juice products; provides input regarding technology, trade, legislative, and regulatory proposals; and sponsors research.
The European Fruit Juice Association (AIJN)
(www.aijn.org) is an organization whose purpose is to work for the best possible political, regulatory, and economic framework at the European Union level to add value and promote the growth of the fruit juice industry. In 2008, AIJN issued its “Alicyclobacillus (ACB) Best Practice Guideline” for the reduction and control of ACB in the production, packing, and distribution of fruit juices, juice concentrates, purees, and nectars. The guideline also references AIJN’s “Guide of Good Hygiene Practice for the Fruit Juice Industry,” which encourages establishment of good manufacturing practice standards. The guideline recommends use of IFU Method No. 12 for juice concentrates and other raw materials, or alternative methods such as Japan Fruit Juice Association’s “Unified Test Method for Thermo-Acidophilic Bacilli.”
Neil H. Mermelstein, a Fellow of IFT, is Editor Emeritus of Food Technology