the Yerba Mate Tea Gourd

...If you fill the gourd from the cow and the cow slips...
or if you leave the mate full of milk, forget you had it full of milk for several weeks, have a very bad cold (your nose is stuffed-up) and you don't smell it
...and it has gone "off" so badly that the bacteria per square inch sets off a government anti-terrorist warning sensor and your house is suddenly blown to little bits by heat-seeking missiles aimed at your hot water thermos moments before you could draw the curdled mass through your bombilla anyway.

The "milk" method is not a method we follow ourselves just because of these terrible fears. We stay at home and do what the government tells us.

However, like many things (including--but not limited to--meatloaf, plum pudding, fruit cake, haggis, mondongo, menudo, and black and white sausage) this method is traditional in many parts.

The reason for this method of curing your mate--in which you fill the gourd with milk and yerba--is twofold. Primarily the milk acts to leach out the bitterness remaining in the gourd and neutralize the pH. The other nominal effect is that of conditioning the wood or gourd with its slight fat content.