I have been wondering about the difference between red wines and white wines. To me, they taste quite different. Red wines are heavier and more complex than white wine, and often tend to be less sweet. Why is this? Actually red and white wines are made quite differently. The differences between red and white wines include the kinds of grapes used, the fermentation and aging process, and the character and flavor of the wine.

White wines are almost always made from white grapes, although they can be made from black grapes, since the juice in most black grapes is clear. When white wine is made, the skins of the grapes are separated from the juice when they are put into a crushing machine. Then yeast is added to the juice for fermentation, until the juice becomes white wine. After filtering etc, the wine is aged by storing it in stainless steel or occasionally oak containers and bottled after a few months. White wines, then, are made without skins or seeds and are essentially fermented grape juice. They have a light character and have crisp fruit flavors and aromas. They can be sweet or dry or somewhere in between. Chardonnay, Pinot Grigio/ Pinot Gris, Riesling, and Sauvignon Blanc are all white wines.

Red wine is usually made from red or black grapes, although all the kinds of grapes usually have a clear juice. The process of making red wine is different from the one of making white wine. After the grapes have been in the crushing machine, the red grapes with their skins and everything sit in a fermentation vat for a period of time, typically about one to two weeks. . The skins tend to rise to the surface of the mixture and form a layer on top. The winemaker frequently mixes this layer back into the fermenting juice (which is called must). After fermentation is over, the new wine is taken from the vat. A little “free run” juice is allowed to pour and the rest of the must is squeezed into “press wine”. The wine is clarified and then is stored, usually in oak containers, for several months until it is ready to be bottled. The oak containers add additional wood tannins and flavors to the wine which help to intensify it and add richness to it. The result of this process is that red wines exhibit a set of rich flavors with spicy, herby, and even meaty characteristics. Beaujolais, Cabernet Sauvignon, Chianti, Merlot, Pinot Noir and Zinfandel are all red wines.

The main difference between red and white wines is the amount of tannins they have. Since tannins largely come from the grape skins, red wines have more of them than white wines. Red wine acquires it’s tannins in the process of maceration (leaving juice to mix together with the skin, seeds and woody bits). It is the tannins and skins of the red grapes which are released into the wine that contribute to the deep color and flavor of red wine. Tannins have a slightly bitter taste and create a dry puckery sensation in the mouth and in the back of the throat; and often lend a wonderful complexity to red wine. They also help preserve the wine. This is why red wines are usually aged longer than white wines.

There are as many different flavor profiles among red wines as there are among white ones. Some red wines are sweet and fruity, while some whites ( such as Chardonnay) have tannins from being stored in oak containers. Some German white wines have lasted for centuries, while some red wines are made for immeadiate consumption. For wines meant for consumption right away the winemaker takes out the bitter tannins, creating a fruity, fresh, and approachable wine. So, apart from the color, there are no hard and fast rules about the differences between red and white wine.

Is it true that red wine is better for you? The research of Dr Frankel has shown that red wine contains more antioxidants than white wine, although the total amount varies according to the variety of grape, region it was grown, the climate and soil it was grown in, and whether it was stored in oak (since wines stored in oak have more antioxidants) and the filtration techniques used. However the antioxidants in white wine are apparently more effective. The research of Dr Troup shows that the antioxidant molecules in white wine are smaller and thus more effective because they can be more easily absorbed. It seems that white wine is just as healthy as red wine.

In summary, the primary difference between red and white wine is the amount of tannins they contain, although there are no hard and fast rules about the differences between them outside of the color of the wine. Usually red wines are more complex, richer, and heavier, with spicy, herby, and even meaty characteristics. White wines are usually sweeter, and lighter, and have crisp fruit flavors and aromas. Neither is significantly better for you. Which wine is best for you to drink is simply a matter of taste.

The short answer is that light can definitely affect wine, but we need to take a closer look at the physics and chemistry of it all to understand why and how in what is called light-strike reactions, which can impart off-odors to wine, what the French call goût de lumière.

Wine is sensitive to the damaging rays of light, particularly ultraviolet (UV) rays from sunlight and fluorescent lighting; that’s why wine (and beer) is packaged in dark bottles-the best example is Port in those familiar, dark, opaque bottles. Wines packaged in clear glass bottles are meant for quick consumption and should be stored in carton boxes until such a time.

All forms of radiation, including visible light ultraviolet (UV) rays and X-rays, have energy that is directly proportional to their frequencies or inversely proportional to their wavelengths-that is, high-frequency waves have short wavelengths, and vice versa. And the greater the energy, the greater the catalytic effect of chemical reactions in wine.

Of concern in wine are visible light and the sun’s UVA rays-yes, UVA rays because research has proven that even a short exposure of wine to sun (UVB and UVC are absorbed by the atmosphere), in the order of hours, can have detrimental effects. That’s because UVA rays lie in the 315-400 nanometer (nm) range of the electromagnetic spectrum and therefore has more energy than visible light, which lies in the 400-700 nm range.

Glass acts as a filter, but clear glass offers no protection against UVA and visible light. Green glass offers some protection, but only half as good as amber; dark-amber glass offers almost complete protection. So why is so much wine, particularly many of the ultra-premium wines of the world, packaged in green glass? This is likely for historical reasons when making green-colored glass was easiest and the effect of radiation on wine was unknown.

But glass is only half the story. We must now consider the optical properties of wine to then determine how radiation effects any chemical reaction.

Research has shown that wavelengths in the 375-440 nm range-that is, the high end of the UVA range and the blue (low) end of the visible light range-are most damaging to wine. The amount of radiation absorbed by wine in this range is directly proportional to opacity; therefore, red wine absorbs the most, and is most affected, while white wine absorbs the least-rosé wine is in the middle. As such, for marketing purpose where displaying color is important, white wine can be stored in clear glass, although not for extended periods of time; that’s why premium whites, such as age-worthy Chablis wines come in dead-leaf-colored glass, a golden-yellow color that provides better protection than green.

Opaque, deeply colored, rich reds absorb almost all radiation; however, these have the highest concentration of effect-inhibiting tannins, which provide protection. But if the concentration is low or the extent of exposure is long, unpleasant and off-putting aromas and flavors can develop. Specifically, red wine has sulfur-containing amino acids, namely, containing methionine and cysteine, which have a thiol (sulfur-hydrogen) side chain in their structures. These then react with naturally occurring vitamins, such as riboflavin (vitamin B2) and pantothenic acid (vitamin B5)-water-soluble vitamins that are easily destroyed by heat, oxygen and, that’s right, UV light. The products of this reaction are sulfur compounds such as hydrogen sulfide, dimethyl sulfide (DMS), and dimethyl disulfide (DMDS), responsible for imparting a range of foul smells from rotten eggs to cabbage and wet dog.

Interesting science.
And now I’m left to wonder if my precious magnum of 1991 Château d’Yquem, in a clear-glass bottle, which I bought for my son born that same year, was affected by X-rays on its travel from the U.S. It was pre-9/11, however, the unyielding airport security guard simply couldn’t be convinced not to X-ray my precious bottle. I guess he was not a fine-wine aficionado.