What is the difference between partial cooking, blanching and slacking foods? Are these all the same term for partial cooking (where you fully cook the foods on another day)?
– David Steck, Food Safety Trainer/Owner, Serve It Up Safe, Tampa, FL
These are three different things, two similar and one totally different.
Let’s start with slacking. The FDA Food Code defines slacking as, “the process of moderating the temperature of a FOOD such as allowing a food to gradually increase from a temperature of -23°C (-10°F) to -4°C (25°F) in preparation for deep-fat frying or to facilitate even heat penetration during the cooking of previously block-frozen food such as spinach.” In short, it means a gradual warming from deep frozen to slightly frozen. The main food safety implication with slacking is to keep the item under refrigeration and let it slack gradually rather than exposing the surface of the food in the danger zone for an extended period of time.
Partial cooking is—as it sounds—cooking the food partway and then continuing later. For example, potatoes for homefries are sometimes cooked in advance and browned on a griddle or steaks for a banquet seared hours before the banquet and then brought to temperature in an oven. With potentially hazardous items like proteins and grains, it is very important to properly control time and temperature for partially cooked items—or avoid partial cooking entirely. A good fact sheet on the topic here.
Blanching is used primarily for vegetables and involves quick cooking in boiling water or hot fat. Those foods may be immediately ready to serve, as in the case of something quick cooking, like blanched spinach used as a garnish in a soup, or may be held safely for further cooking such as blanched French fries cooked in lower-temperature oil and then quickly fried in hotter oil for service.
Complicating all of this, of course, is that people use these terms incorrectly, causing confusion. The best solution is to look at the process in place from a food safety perspective rather than worrying too much about whether the practice is technically partial cooking, blanching or slacking.