Acidity

• An acid added to a cream liquor curdles the liquid because the lower pH denatures the protein molecules in the cream and causes them to bunch together into curds. For instance, adding lime or other citrus juice to a cream liquor adds acid and curdles the drink. Other acidic culprits include cola, sour mix, coffee or energy drinks. Any of these mixers potentially create a curdled cocktail when added to creamy liquor.

Poor Timing

• Adding ingredients to a drink in the wrong order causes the cream liquor to curdle. For instance, adding an acidic ingredient immediately to the cream before mixing with ice or other ingredients results in a lumpy mess. On the other hand, mixing the acidic ingredient with neutral ingredients such as ice, water or other liquor before adding the cream liquor helps dilute the effect of the acid by making it a smaller percentage of the overall cocktail when it finally goes in.

Inadequate Blending

• When mixing a cream-based liquor drink, vigorous shaking or blending helps prevent curdling. Curdling becomes more likely in creamy liquor drinks mixed with simply a straw or a quick stir. Adequate blending of a creamy cocktail keeps the cream liquor emulsified and prevents curdling. Don't be afraid of over-blending here. More is better.

Temperature

• Drinks mixed at room temperature curdle more often than those mixed after chilling. Because the chemical reaction that causes the curdling requires some amount of heat to activate, the colder the ingredients are when they go in, the more inert they are and less likely to curdle. Keep cream liquors in the refrigerator and ice down thoroughly before mixing. Chill juices and other ingredients as well.

Alternatives

• After trying several times to mix the perfect beverage only to find it continues to curdle, try making your own cream liquor. Use heavy cream with the highest fat content you can find and mix in liquor and flavorings. The higher fat content in the heavy cream makes its protein molecules less susceptible to denaturing and curdling. Another alternative is to layer the drink instead of mixing it. Add the cream liquor last as a floater and sip. Other drinks, such as an Irish car bomb, just curdle and it's part of the experience. Drink it fast.