Regarding illicit manipulations, see under wine adulteration.
Wine adulteration (colloquially known as "pantschen") is the deliberate manipulation of the wine making process in violation of wine law, which is carried out with deceptive or fraudulent intent. In doing so, the aim is to "improve" the taste or texture by means of prohibited additives, thus falsely pretending to have a certain or better quality, to increase the quantities of high-quality wines by mixing them with simple, cheaply produced bulk wine or simply by diluting them with water, and to market wines under prestigious names or vintages by means of false labelling using real labels and/or bottles.
Throughout history, there have always been different and often changing views on what exactly constitutes adulteration of wine. What today is considered as panchetta was perhaps a widely practiced practice just a few decades ago. Even today some techniques are regulated differently from country to country and especially in Europe compared to the New World. Three significant examples are the regulations concerning enrichment, acidification and sweetening. The introduction of strict wine laws in many wine-growing countries starting at the end of the 19th century had a positive effect. For some wine-growing regions they already existed before that. However, it was of course not possible to prevent manipulations completely.
Especially the 18th is considered the "century of wine scandals". The enormous demand in England for port wine led to bottlenecks from 1730 onwards. Therefore, simpler wines were mixed with alcohol, elderberry juice, ginger, pepper, cinnamon and sugar on the Douro. The positive effect was that in 1756 the port wine area was declared one of the first protected areas of origin and strict laws were passed. In Bordeaux, it was common practice on a large scale to blend the wines for the English market with strong, simple wines from other areas (Rhône, Spain). When there was a great shortage of wine in France due to phylloxera and mildew, raisin wine was produced in large quantities from 1880 onwards. In the 19th century there were masses of forgeries of Hungarian Tokaj in many countries, and books even contained detailed recipes for it.