Alicyclobacillus spp. Detection - GENE-UP® PRO ACB

March 01, 2022

Beverage producers live tenuously by the strings of their flavor. Brands grow or wither based on their signature aromas, tastes and aftertastes; one skunky sip diminishes customers, reputation and profits. 

A 2017 survey published in the International Journal of Systematic and Evolutionary Microbiology revealed that over 90% of juice manufacturers surveyed indicated that better control over microbial spoilage would have moderately to greatly increased profits and reduced waste.

The culprit of a flavor imbalance can oftentimes be tied to the presence of Alicyclobacillus (ACB) and its byproduct, guaiacol. ACB thrives in juice and can survive pasteurization. Although not pathogenic, the guaiacol enzyme does alter a beverage’s flavor profile.

One challenge juice manufacturers face is the time it takes to test for Alicyclobacillus (ACB) and guaiacol. Traditionally, two tests at release time yield at least a 48-hour wait time. That’s two days' worth of sitting inventory — a woe for any production leader.

“Better understanding the structure of the Alicyclobacillus genus and the spoilage potential of individual species drives improvement in quality management decisions that reduce waste and improve customer satisfaction,” says Abigail Snyder, assistant professor of microbial food safety at the Cornell College of Agriculture and Life Sciences and senior author of that 2017 survey.

However, there is good news for today’s quality controllers. You can now test for ACB and guaiacol in a single test with next-dayresults, a first-of-its-kind in beverage industry protocol.

WHY TEST FOR ALICYCLOBACILLUS?

Alicyclobacillus (ACB) is an acidophilic and spore-forming organism that thrives in juice. Alicyclobacillus spp. possess several distinct characteristics, but the major one is their ability to survive commercial pasteurization processes and produce off-flavors in fruit juices. The fruit juice industry has acknowledged Alicyclobacillus spp. as a major quality control target microorganism¹.

ACB contamination is fairly common due to its impermeability to pasteurization, and a positive ACB test does not always imply spoilage. Instead, organoleptic spoiling — impacting odor and taste — occurs due to a metabolite called guaiacol, an unpleasant odorous compound in fruit juices produced from ACB.

THE CHALLENGE OF TRADITIONAL ACB TESTING

ACB is a tricky organism. Pasteurization doesn’t always kill it, ACB doesn’t always produce guaiacol, and traditional ACB screening doesn’t always identify spoilage. “Not all ACB cause product spoilage. It is off-aroma produced by ACB that is the real culprit in product spoilage, not simply the presence of ACB itself,” Snyder adds. To detect the flavor-altering guaiacol, a second enzymatic test must be performed.

Common spoilage testing requires a two-step system: an ACB screen, plus an enzyme screen. Not only do two tests increase the risk of human error, results return in 48 hours while the product sits idle — using valuable refrigeration and storage space.

“When companies monitor just for the presence of ACB, they may make product disposition decisions that do not reflect the spoilage potential of that material. Better diagnostic tools that predict spoilage, not just ACB presence, could help address that challenge.”

THE ADVANTAGES OF ONE-STEP ACB TESTING

With so many what-ifs in ACB testing, the most efficient and accurate method is one test that provides next-day Alicyclobacillus and guaiacol results. One-and-done ACB and guaiacol detection — like the bioMérieux’s new GENE-UP^® PRO ACB — eases workflow, minimizes human error and avoids false positives.

By incorporating two tests into one, bioMérieux’s GENE-UP^® PRO ACB packages their time-tested microbiological PCR detection into a standard workflow. This new single assay specific to juice production identifies the gene that is 100% correlated to guaiacol production. ACB testing is complete within 27 hours, instead of the conventional 48 hours, so inventory can be moved quickly and profits can be saved.

“The Gene-Up Pro ACB assay is unique because it predicts the function of guaiacol production rather than simply relying on species identification and associating species with guaiacol production,” Snyder says. “That type of information can serve as a decision support tool for the industry to improve their quality management decisions that reduce waste and improve customer satisfaction. Anecdotally, it is also comparatively a much shorter time to result and requires only basic lab skills to use.”

REFERENCES

¹ Chang SS, Kang DH. Alicyclobacillus spp. in the fruit juice industry: history, characteristics, and current isolation/detection procedures.Crit Rev Microbiol. 2004;30(2):55-74. doi: 10.1080/10408410490435089. PMID: 15239380.