Growth Behavior of Off-Flavor-Forming Microorganisms in Apple Juice

Abstract

Alicyclobacillus acidoterrestris and Streptomyces griseus griseus are two bacteria species that are frequently found in apple juice as spoilage bacteria. They both show thermoacidophilic behavior, adapting to the low pH of the juices and being able to survive high temperatures. They are able to regerminate in the shelf-stable product and spoil the juice by the formation of off-flavor compounds (i.e., guaiacol and 2,6-dibromophenol as metabolites of A. acidoterrestris and 2-isopropyl-3-methoxypyrazine, 2-methylisoborneol, 2-isobutyl-3-methoxypyrazine, and geosmin as important metabolites of S. griseus). In this study the growth behavior of the strains and the impact on apple juice were investigated under different conditions (i.e., temperature, oxygen supply, and mutual influence of the strains). The off-flavor formation was monitored by GC-MS after headspace SPME and subsequent calculation of the odor activity values. The results showed that S. griseus grows and consequently spoils the product even at 4 degrees C, whereas A. acidoterrestris needs at least room temperature to show significant growth. Limited oxygen supply did not significantly reduce off-flavor formation for any of the strains. The simultaneous presence of the strains in the juice reduced the growth of both species; nevertheless, off-flavor was detected.

Defining the stability interfaces of apple juice: Implications on the optimisation and design of High Hydrostatic Pressure treatment

“…For example, headspace volatile measurements (Boff et al, 2003), monitoring off-flavor formation (Siegmund & Pollinger-Zierler, 2007) and differentiating between microbial metabolites by Fourier transform infrared spectroscopy (Walker & Phillips, 2008) could be implemented. Additionally, sensorial analysis studies will be of importance as they are directly related to the consumer's acceptance.…”

Modeling the effects of temperature and pH on the resistance of Alicyclobacillus acidoterrestris in conventional heat-treated fruit beverages through a meta-analysis approach

“…Presently, more than 20 species have been reported to belong to Alicyclobacillus genus (Smit et al, 2011;Glaeser et al, 2013), while spoilage potential of fruit juices has been restricted to few species such as Alicyclobacillus acidoterrestris, Alicyclobacillus acidiphillus, Alicyclobacillus pomorum, Alicyclobacillus herbarius, Alicyclobacillus hesperidum, Alicyclobacillus acidocaldarius and Alicyclobacillus cycloheptanicus (Cerny et al, 1984;Matsubara et al, 2002;Goto et al, 2003;AIJN, 2007;Smit et al, 2011). The spoilage potential of Alicyclobacillus species relies on their ability to produce off-flavor compounds such as 2-methoxyphenol (guaiacol), 2,6-dibromophenol, 2,6-dichlorophenol and 2-methyltetrahydrothiophene-3-one (Siegmund and P€ ollinger-Zierler, 2006;Lottici et al, 2006;Siegmund and P€ ollinger-Zierler, 2007;Concina et al, 2010).…”

Immunomagnetic Separation Combined with Polymerase Chain Reaction for the Detection of Alicyclobacillus acidoterrestris in Apple Juice

“…Alicyclobacillus acidoterrestris ( A. acidoterrestris ), which contains ω-fatty acids as the major membrane fatty acid component, is a thermophilic, aciduric, gram-positive, rod-shaped, spore-forming and nonpathogenic bacterium [1–3]. As it can survive in highly acidic environments of pH 2.5-6.0 at temperatures of 25-60 °C, and its spore can germinate and proliferate in acidic fruit juices or beverages, A. acidoterrestris is extremely difficult to be inactivated completely by conventional pasteurization [4,5].…”