Taste-Active Maillard Reaction Products in Roasted Garlic (Allium sativum)
journal contributionposted on 05.07.2016 by Junichiro Wakamatsu, Timo D. Stark, Thomas Hofmann
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In order to gain first insight into candidate Maillard reaction products formed upon thermal processing of garlic, mixtures of glucose and S-allyl-l-cysteine, the major sulfur-containing amino acid in garlic, were low-moisture heated, and nine major reaction products were isolated. LC-TOF-MS, 1D/2D NMR, and CD spectroscopy led to their identification as acortatarin A (1), pollenopyrroside A (2), epi-acortatarin A (3), xylapyrroside A (4), 5-hydroxymethyl-1-[(5-hydroxymethyl-2-furanyl)methyl]-1H-pyrrole-2-carbalde-hyde (5), 3-(allylthio)-2-(2-formyl-5-hydroxymethyl-1H-pyrrol-1-yl)propanoic acid (6), (4S)-4-(allylthiomethyl)-3,4-dihydro-3-oxo-1H-pyrrolo[2,1-c][1,4]oxazine-6-carbaldehyde (7), (2R)-3-(allylthio)-2-[(4R)-4-(allylthiomethyl)-6-formyl-3-oxo-3,4-dihydropyrrolo-[1,2-a]pyrazin-2(1H)-yl]propanoic acid (8), and (2R)-3-(allylthio)-2-((4S)-4-(allylthiomethyl)-6-formyl-3-oxo-3,4-dihydropyrrolo-[1,2-a]pyrazin-2(1H)-yl)propanoic acid (9). Among the Maillard reaction products identified, compounds 5–9 have not previously been published. The thermal generation of the literature known spiroalkaloids 1–4 is reported for the first time. Sensory analysis revealed a bitter taste with thresholds between 0.5 and 785 μmol/kg for 1–5 and 7–9. Compound 6 did not show any intrinsic taste (water) but exhibited a strong mouthfullness (kokumi) enhancing activity above 186 μmol/kg. LC-MS/MS analysis showed 1–9 to be generated upon pan-frying of garlic with the highest concentration of 793.7 μmol/kg found for 6, thus exceeding its kokumi threshold by a factor of 4 and giving evidence for its potential taste modulation activity in processed garlic preparations.