Issue link: https://digital.copcomm.com/i/688647
{ SOMMjournal.com } 67 the perception and intensity of bitterness and, as such, wines imbalanced to alcohol can and often do smell and taste bitter. There's a two-fold connection between the higher alcohols, isoamyl and isobutyl, and bitterness. Isoamyl has a burnt, bitter smell, and because they're larger molecules than ethanol, in greater amounts they both con - tribute to bitter flavors. Terpenes, the powerfully fragrant molecules that occur in small concentrations in Muscats, Gewürztraminer, Riesling and Torrontés grapes, are often cited as a source of bitterness, but research shows these acid- and enzyme- activated molecules don't contribute to the problem. As a rule, acidity doesn't enhance the perception of bitterness. Grape seeds are the source of the tannin epicatechin, which is significantly bitter and has a long duration of bit - terness on the palate. Winemakers take measures to avoid breaking seeds during vinification and typically keep press wine separate to control for bitterness, among other things. Material other than grapes (MOG), including leaves, stems and insects, that finds its way into the crusher can also result in bitterness, with the biggest culprit being the multicolored Asian lady beetle (lady bug). Lady bug taint is a fault caused by methoxypyrazine, specifically 3-isobutyl- 2-methoxypyrazine (IBMP), which we can detect at 10 to 15 parts per trillion. Lady bugs contain enough IBMP that one beetle per vine can taint a tank. Amertume, the French word for bitterness, is a less com - mon wine flaw or fault that can occur in wines with high levels of anthocy anins. It results from the combination of lactic acid bacteria like Oenococcus oeni, Lactobacillus and Pediococcus, which are responsible for malolactic fermentation and the breakdown of glycerol as it reacts with anthocyanins and other phenols during aging. A wine that tasted sound when bottled could evolve towards bitterness in the bottle, but modern winemaking practices make this fault a rarity. In the glass, bitterness is often confused with astringency, and differentiating the two takes practice. It's useful to know that we use two different sensory systems to per - ceive them. But, when it comes to bitterness, we're not all wired the same way. Geneticists have determined that there's an inherited aspect that influences how we taste for bitterness. Depending upon the shape of our taste receptors, dif - ferent people tasting the same wine could experience it as intensely bitter, somewhat bitter or without a bitter taste at all. More than 550 bitter-tasting compounds have been identified, of which about 100 have been matched to one or more specific taste receptors. On average, about 75 percent of people can register bitterness and 25 percent are non-tasters who are not able to detect bitterness. In a scenario like a wine competition, a panel would be hard pressed to generously award a wine if several tasters found it flawed or faulted with bitterness, as three-quarters of all consumers would do the same. Odorless and nearly flavorless, anthocyanins, the water-soluble pigments that color wine red, blue or pur - ple depending upon their pH, impar t a mild astringency in wine, while tannins are a source of both astringency and, to a lesser degree, bitterness. Wine can contain two kinds of tannins: condensed tannins, a mixture of long-chain (polymerized) phenols called cat - echins found in the skins and stems which are astringent and the bitter grape seed tannin epicatechin; and wood tannins, water-soluble, non-flavonoid ellagitannins from oak which are more bitter than astringent. Astringency is a tactile, dry - ing sensation that we feel when grape tannins and wood tannins interact with the glycoprotein in saliva. When wine hits the mechanoreceptors of the trigeminal nerves that detect che - mosensory irritation in the mouth and throat signals are sent to the somatosensory cortex. We feel astringency in the tannins found in wine and tea, tobacco and cruciferous vegetables. We also process the feel of viscosity from alcohol and glycerol in the same way. PHOTO: VALENGILDA VIA THINKSTOCK Lady bugs contain enough IBMP that one beetle per vine can taint a tank.