Odor Thresholds of Microbially Induced Off-Flavor Compounds in Apple Juice

Abstract

Microbially derived off-flavor is a major problem in apple juice production as it diminishes the sensory quality of the juice significantly. Fifteen relevant off-flavor compounds that are formed in apple juice, for example, by the strains Alicyclobacillus acidoterrestris and Actinomycetes (Streptomyces ssp.) were investigated with respect to their sensory relevance. The odor threshold values (i.e., detection and recognition values) were determined for all compounds in the matrix apple juice. Odor threshold values for fenchyl alcohol are reported here for the first time. The obtained values were set in relation to the limits of detection and quantification of a previously published GC-MS method. Eight tainted apple juice samples were analyzed for the presence of the 2 strains and the 15 off-flavor compounds. Both strains could be found in the samples; the presence of Streptomyces ssp. as spoilage bacteria of apple juice is reported for the first time. In samples with distinct off-flavor, 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 1-octen-3-ol, fenchyl alcohol, geosmin, and guaiacol as well as 2,6-dibromophenol were determined in concentrations higher than the detection threshold.

Lactic acid bacteria isolated from apples are able to catabolise arginine

“…It is well known the beneficial role of LAB in the manufacture of apple cider since they are responsible to carry out MLF (Siegmund and Pollinger-Zierler 2006). However, few data on apple lactic acid microflora and their potentialities to use arginine are found, yet.…”

How big is the gap between olfactory detection and recognition of aliphatic aldehydes?

“…Their criterion for recognition was based on cued labeling-that is, on choosing a verbal label among four options. Siegmund and Pöllinger-Zierler (2006) compared detection and recognition thresholds for 6 off-flavor compounds in apple juice and reported that the difference between the two measures ranged from a should be possible at lower concentrations, relative to detection threshold when more receptor types are available. The finding that mice are not necessarily more sensitive to monomolecular odorants in terms of detection thresholds (Laska, Persson, & Hernandez Salazar, 2009) but are clearly better at discriminating between structurally related odorants, such as enantiomers or members of homologous series of odorants (Laska, Rosandher, & Hommen, 2008), as compared with species such as honeybees (Laska , Galizia, et al, 1999), squirrel monkeys (Laska, Trolp, & Teubner, 1999), or humans, all of which have a lower number of olfactory receptor types than the mouse, is consistent with this idea.…”

“…Whereas the determination of olfactory detection thresholds is usually performance based-that is, subjects have to meet a criterion of detection according to signal detection theory-the determination of olfactory recognition thresholds is usually based on verbal reports, often using arguable criteria, such as cued labeling, or even the simple statement that an odor quality has been perceived (Lee, Paterson, & Piggott, 2000;Siegmund & Pöllinger-Zierler, 2006;Toyota, Kitamura, & Takagi, 1978). In the present study, we used a performance-based measure of odor recognition that is based on the ability to discriminate the target stimulus from another stimulus of approximately equal intensity.…”

Analysis of Volatile Phenolic Compounds Responsible for 4-vinylguaiacol-like Odor Characteristics of Sake

“…bacterial spoilage in apple juice. The bacteria produce guaiacol through oxidative degradation of ferulic acid via 4-VG (Siegmund and Pollinger-Zierler, 2006, Goto et al, 2008, Smit et al, 2011. In the case of wine production, guaiacol, 4-methylguaiacol, and syringol were detected in barrelaged wine (Prida and Chatonnet, 2010) as well as in wine made from bushfire smoke-affected grapes in Australia (Mayer et al, 2014).…”