The production of volatile compounds during cereal fermentation, such as organic acids (butyric, succinic, formic, valeric, caproic, lactic, acetic, etc.), alcohols (ethanol, n-propanol, isobutanol, isoamyl alcohol, etc.), aldehydes and ketones (acetaldehyde, formaldehyde, isovaleraldehyde
, n-valeraldehyde, 2-methyl butanol, etc.), and carbonyls compounds (furfural, methional, glyoxal, etc.), contributes to a complex blend of flavors in fermented cereals and makes them more appetizing .
As shown in entry 9, isovaleraldehyde
also led to the relatively high enantio- and diastereoselectivities (syn/anti = 86/14, 68% ee) though the yield was low (12%).
The enzyme showed no activity towards 4-aminobutyraldehyde, betainealdehyde, acetaldehyde, propionaldehyde, butyraldehyde, isovaleraldehyde
acetaldehyde, benzaldehyde, butyraldehyde, formaldehyde, isovaleraldehyde, n-hexaldehyde, propionaldehyde, valeraldehyde
Aldehyde Air Sampling Results Aldehyde CAS# Plenum Concentration Result MRL ([mu]g/[m.sup.3]) ([mu]g/[m.sup.3]) acetaldehyde 75-07-0 18.0 1.7 formaldehyde 50-00-0 28.0 1.4 n-hexaldehyde 66-25-1 15.0 7.7 benzaldehyde + 100-52-7 - - butyraldehyde + 123-72-8 - - Isovaleraldehyde + 590-86-3 - - Propionaldehyde + 123-38-6 - - valeraldehyde + 110-62-3 - - Aldehyde CAS# Result MRL (ppbv) (PPbv) acetaldehyde 75-07-0 9.8 0.9 formaldehyde 50-00-0 23.0 1.1 n-hexaldehyde 66-25-1 3.6 1.9 benzaldehyde + 100-52-7 - - butyraldehyde + 123-72-8 - - Isovaleraldehyde + 590-86-3 - - Propionaldehyde + 123-38-6 - - valeraldehyde + 110-62-3 - - + These aldehydes were monitored approximately one month before at the same sampling location and found to be below the method reporting limit.
The catalyst loading has a profound effect on hydrogenation of isovaleraldehyde
. It is seen that % conversion of iso-valeraldehyde increases with an increase in catalyst concentration as expected.
In addition, a number of aldehyde species well known for offensive odorants such as acetaldehyde, valeraldehyde, and isovaleraldehyde
were seen at the range over two orders of magnitude with mean concentrations of 99.3, 12.2, and 3.96 ppb, respectively.
To this end, a series of calibration experiments were conducted by both systems using identical standards containing 5 CCs (acetaldehyde (AA), propionaldehyde (PA), butyraldehyde (BA), isovaleraldehyde
(IV), and valeraldehyde (VA)) prepared in both gas and liquid phases.
A total of 19 VOCs were initially selected as the reference analytes for this study: (1) five aldehydes: acetaldehyde (AA), propionaldehyde (PA),butyraldehyde (BA), isovaleraldehyde
(IA), and n-valeraldehyde (VA); (2) six aromatics: benzene (B), toluene (T), styrene (S), p-xylene (p-X), m-xylene (m-X), and o-xylene (o-X); (3) four carboxylic: propionic acid (PPA), butyric acid (BTA), isovaleric acid (IVA), and n-valeric acid (VLA); (4) two ketones: methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK); (5) one alcohol: isobutyl alcohol (i-BuAl); and (6) one ester: n-butyl acetate (BuAc) (Table 2).