Researchers in Brazil have estimated the growth timeline of a bacterium that causes orange juice spoilage during shelf life (approximately 6 months) and developed a safe and inexpensive filling, cooling, and storage protocol that inhibits bacterial growth and offers an alternative to other proposed treatments.
They report their findings in the December 2009 issue of the journal Applied and Environmental Microbiology.
Alicyclobacillus sp. was first attributed to spoiled apple juice, or "off" flavors, in 1982 and Alicyclobacillus acidoterrestris is recognized as the most significant spoilage species within the family. Its ability to grow in a broad temperature range under acidic conditions and withstand heat allows for both survival during pasteurization and growth during juice storage and creates a continuous challenge for fruit juice and beverage industries worldwide.
Pasteurization followed by hot-fill or cold-fill processes are the two main methods used by the fruit juice industry to eradicate bacterial presence. Hot-filling, described as heating the product to approximately 200˚ Fahrenheit and holding for 15 to 20 seconds then filling into the package and cooling at room temperature, has been used extensively to process fruit drinks. However, the extended time that the product is maintained at room temperature allows for growth of bacteria such as A. acidoterrestris that can thrive in a wide temperature range. In the study researchers estimated and compared growth timelines of A. acidoterrestris in hot-filled orange juice following pasteurization that was cooled and stored in various conditions ranging from 68˚ to 95˚ Fahrenheit and inoculated with two different amounts of the bacterium. Only one treatment involving storage at 68˚ completely inhibited A. acidoterrestris growth for the full 6-month shelf life.
"In conclusion, treatment 5 (storage at 20˚ C) was more efficient than any of the others since in this case the A. acidoterrestris population remained inhibited for the entire shelf-life of the orange juice," say the researchers. "This measure can be considered a safe, easy, and inexpensive alternative procedure to avoid A. acidoterrestris growth during the orange juice shelf-life."
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