Plate-and-frame (PF) and spiral-wound (SW) membrane configurations were used to study influence of reverse osmosis (RO) on flavor compounds in apple juice permeate and retentate. Low temperature (20°C) and high pressure (50 bar) were most effective operating parameters for flavor recovery. Non-volatile flavor component RO losses were due to permeation. However, loss of volatile compounds through permeation was minor compared with equipment processing losses. Flavor compounds showed more rejection by polyamide than polyether-urea thin-film composite membranes. The SW configuration demonstrated greater flavor losses than did PF. Chemical structure of aldehydes and esters appeared to affect flavor compound retention. Volatile losses modified the flavor profile of RO concentrated apple juice.
α-Dicarbonyls (α-DCs)
are key reactive Maillard intermediates
with structural diversity and are widely found in foods and in vivo,
but little is known regarding the complete molecular profiles of these
potentially harmful electrophiles. Herein, we reported a novel isotope-coding
derivatization (ICD) strategy for the broad-spectrum, quantitative
profiling of (non)target α-DC species in natural foodstuffs.
It utilized differential isotope labeling (DIOL) with a reagent pair o-phenylenediamine (OPD)/OPD-d
4 (deuterated) to form stable quinoxalines for class-specific fragmentation-dependent
acquisition using liquid chromatography–hybrid quadrupole linear
ion trap mass spectrometry (LC-QqLIT). A combination of facile one-pot
quantitative labeling and convenient cleanup protocol afforded satisfactory
sensitivity, linearity, accuracy (81–116%), and process recovery
(86–109% with RSDs < 10%) by matrix-matched ICD-internal
standard calibration, without significant matrix interference (−9
to 5%), isotopic effect (<0.5%), and cocktail effect. A more generic
DIOL-based LC-QqLIT algorithm integrated double precursor ion and
neutral loss scan to trigger enhanced product ions with the unique
isobaric doublet tags (4 Da shift), enabling simultaneous screening
and relative quantitation of nontarget α-DC analogues in a single
analysis. This study has widened the vision on complex α-DC
profiles in traditional botanicals, which revealed a wide occurrence
of α-DCs in such processed sugar-rich products, yet their abundance
varied greatly among different samples.
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