Food safety is no more important in SV than it is in any other manner of food handling, and it is no more difficult, either. The difference between SV and other methods of food handling is that SV wasn’t discovered as a process of trial and error, like most other forms. Knowledge of boiling, roasting, curing, etc. have all been handed down from generation to generation, so their safety is taken for granted. In ancient times, methods of food preparation that were not safe died out—or, their practitioners did.
Knowledge of food safety was not handed down by the gods, although some religions do attempt to identify and address it. But food safety has to be the MOST important aspect of cooking, even for restaurants. This idea riles a lot of chefs, but, consider this:
No matter how tasty, how beautiful, how wonderfully served, no business can operate for long if the food isn’t safe. And food safety doesn’t happen by itself. It’s a consequence of correct procedure, conscious or otherwise. That’s why we have refrigerators, and sealed containers, and so on. Right now, we’re going to go over just how LITTLE food science one needs to know in order to process SV safely: the principles we discuss will help people understand why other methods of cooking are safe, as well.
Actually, in food handling, the greatest dangers exist BEFORE and AFTER the actual cooking: contamination of products before and after the preparation, and improper cooling methods are the most common culprits. Here’s a surprising little detail.
The temperatures between 70F and 90F are the MOST dangerous.
As it turns out, bacteria have a lot in common with other living things, including humans. Between 70F and 90F, we are very active, we eat, we reproduce, all that life stuff. If your raw products, for example, spend more than 2 hours between those two temps, you are really rolling the dice, because pathogens can become very active. And, even WITHOUT the actual presence of bacteria, long periods of time in that range causes degradation of cells, with collateral creation of toxic substances (Autolysis).
Most of us don’t realize how fortunate we are that this is true. Uncooked food, ALL uncooked food, has bacteria on it. They eat the same things we do. Most of the bacteria are harmless, or, even, beneficial. Bacteria that pose a risk are called pathogens. Viruses, fungi, and parasites can also be pathogenic, but are by far the easiest to destroy. Salmonella, E. Coli, etc., all pathogens. For the purposes of food safety, Salmonella are considered the hardiest, so they are used in the “kill models” that scientists create. If the Salmonella are dead, so are all the others. Salmonella stop growing by 122°F (50°C), and, with a formula that includes time in the protocol, they will die, and your food will be pasteurized. The lower the temperature, the longer it takes to pasteurize, and SV recipes and formulas typically reflect that. To allow for error, most SV recipes use temps no lower than 129F.
Pathogens are Colorless, Odorless and Tasteless
They should not be confused with autolysis, which is the natural decomposition of organic matter. Autolysis causes the release of gases by products, and can sometimes be detected by smell, taste, and appearance. This is generically referred to as the rotting or spoiling of food. No bacteria are necessary for this process, even though they are frequently present. The food sealed in a SV bag CAN autolyze, if it is not handled properly, even without bacteria.
When your project is done, you may not necessarily want to finish and eat it right away. This is a growing trend; I “cold shock” almost all of my projects, and then “retherm” them. This can be done without negating the many benefits of SV processing, and gives you a lot of freedom as to how to serve your products later.
For example, you can process a number of chicken breasts in individual packages, serve one when they are done, and refrigerate the rest. Since they are pasteurized and sealed, they will keep under refrigeration much longer than they would raw, OR unsealed. You may remember my mention of hard boiled eggs being an inadvertent example of SV processing, because they are cooked sealed in their shells. You may also remember my observation that it is what happens to the eggs AFTER they are cooked that creates potential risk. This is true of all SV projects. It is not enough to pull your package(s) out of the tank and then just put them in the refrigerator. Your refrigerator is not designed to handle such a heavy load, and the temperature inside will increase dramatically, affecting other food in the refrigerator as well.
Shocking is an Important Step
Foods that have been processed SV should be chilled in iced water (“shocked”) until they are cold enough to be put in the refrigerator without affecting its temperature. Be sure to spread them out. Put them close to the compressor. This is also extremely important with foods that were prepared by traditional methods, but nobody really talks about it. If you roasted a whole turkey for a party, and then the party was cancelled, and you put that whole hot turkey in the refrigerator, would you expect it to be good the next day? The custom of leaving the Thanksgiving Turkey out after service, so that guests can “pick at it” at their leisure, makes Health Inspectors cringe, and for good reason. There are still many people who don’t see the risk involved in letting that pizza that they had for dinner sit out on the table overnight, to be enjoyed as focaccia the next morning. And these same people worry about the inherent danger of Sous Vide!