It’s perhaps the occasionally florid descriptions of wines provided by critics (self included) and merchants that lead some people to question whether or not the makers of certain wines actually add flavouring chemicals to enhance their product. Giving that question a little spice is that we’re presently awaiting the results of an investigation in South Africa to determine whether or not some makers of sauvignon blanc in that country have been adding methoxy pyrazines to their wines to enhance their grassiness and ‘varietal character’. Furthermore, the Austrian wine scandal of the 1980s quickly crossed borders and became a German wine scandal once it was realised that certain German wine producers were including (what was then) cheaper Austrian under German wine labels. However, given the nature of these and other scandals that only emerge with minimal frequency, it is to the credit of the wine industry at large that they are indeed a genuine rarity. Most wine producing countries, and certainly those that regularly export to the EU, are subject to carefully defined lists of permitted additives. Most of these additives are preservatives or fining agents, and as such should leave no discernible impression on flavour. Unless they’re added to excess, as sulphur dioxide can be from time to time, preservatives should not impact taste, while fining agents, which help the clarification and long-term stability of wine, should leave only a negligible residue at absolute worst. In theory and in the overwhelming majority of practice, wine tastes the way it does because of the quality and nature of the fruit from which it was made, the fermentation process which causes considerable modification and enhancement of flavours, and the effects of different winemaking and maturation techniques on texture and flavour. Taste grape juice from a noble wine variety, and you’d hardly believe it to be capable of the complexity of flavour it can alter acquire, even if the wine is simply fermented in and then matured in neutral containers. Riesling, as you mention, provides a remarkable example, and one genuinely able to reflect even minor nuances of terroir (the combined influences of site, aspect and immediate climate). With experience, it’s possible for most people to learn to identify the particular characteristics of each important grape variety, and then even to link in the addition nuances of region and even site. So when wine writers, self included, ramble on about bizarre notions of scent, taste or texture (ie ‘a honeysuckle-scented riesling with a perfume of peach and mango, before a racy long palate of lingering minerality’), it’s even remotely possible they might be isolating something entirely special and unique about an individual wine or vineyard!
