When tasting wine, particularly if you are doing so to decide what wines to buy, one should start with light wines and progress to stronger tasting wines, as otherwise you will not be able to properly taste the wines.
If you are tasting for pleasure, feel free to eat at the same time. However, if you are tasting to decide what wine to buy, avoid eating anything at the same time. If necessary, a neutral food such as a dry biscuit can be eaten. There are three problems with eating while tasting:
The food will mask the taste of the wine. If you are eating, it is much more difficult to properly smell and taste the wine. Strong tasting food (e.g. a curry) should be avoided not only during tasting but also in the hours preceding.
The food makes the wine taste better. Some foods, especially cheese, improve the flavour of the wine. This is why many wine merchants offer cheese during wine tasting. Tempting as it may be to have some cheese with your wine, keep in mind that this gives you a false impression of its taste, and encourages you to buy a wine that will later be a disappointment.
The wine merchant won't take you seriously. Nobody who is serious about their wine would eat while tasting (especially, they would not eat fatty or strong tasting foods such as cheese). If you do so, you give the impression that you are neither serious nor knowledgeable about wine, so the wine merchant will feel that he can get away with selling you anything.
If you are tasting multiple wines, feel free to ask for a glass of water. A couple of sips, rolled around the mouth, will help clear the palette between wines.
If the wine merchant has many wines, rather than working your way through the list, it is useful to describe the type of wines you like and ask which wines match that description. It is easier to choose from a small selection than from a long one, especially if you are swallowing the wine. The wine merchant will also appreciate this approach.
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