Did a Dutch press turn chocolate from a drink into a food?

Yes, in large part, though the credit has been handed to the wrong Van Houten. In 1828, Casparus van Houten Sr. patented a hydraulic press that squeezed the fat out of roasted cocoa beans. His son, Coenraad Johannes van Houten, is usually given the credit, even though the press was in fact his father's invention.

Before the press, cocoa beans were ground into a fine mass that could be mixed with milk to make a drink, or with sugar, cinnamon and vanilla to make cookies. The centre of the bean, the nib, contains on average 54 percent cocoa butter, so the drink was very fatty. People often stirred in starches such as arrowroot to soak up the extra fat. The press reduced the cocoa butter in cocoa liquor by nearly half. On one side it left a cake that could be pulverized into cocoa powder, and on the other side it gave pure cocoa butter. The powder made a less fatty drinking chocolate, and the butter made for better eating chocolate. Together they became the base of the modern chocolate industry.

Coenraad's own invention came next. He treated the powder with alkaline salts so that it would mix more easily with water. This process, still called Dutching, gives a darker colour and a mild taste, and the product is still called Dutch process chocolate. Dutching reduces the cocoa's natural acidity, and it leaves lower amounts of flavonols, though the effect on nutrition is disputed.

The press spread slowly: John Cadbury bought one in 1866 but did not use it until 1875. By the 1870s eating chocolate sales soared, creating a demand for cocoa butter that came to be traded internationally. Some call the result the democratization of chocolate.