Everybody values delicious, beautiful, perfectly cooked food. But even for restaurants, flavor and appearance of quality are not the most important criteria for products for sale. FOOD SAFETY is, and must be the very first consideration. It’s “shocking” to some but no matter how popular your restaurant is, no matter how high the profit margin, no matter how much your family loves you, if your food does not meet food safety requirements, you will not be popular for long.
Unlike familiar and traditional forms of cooking, sous vide processing has been specifically engineered to offer safe, scientifically confirmed, pasteurized food. One of the primary components of the safe cooking of food is avoiding what is referred to as “the temperature danger zone.” Briefly explained, pathogenic bacteria (the little critters that make us sick, e.coli, Salmonella, etc.) have a number of things in common with humans and all other animals.
They like temperatures between 70F and 90F for one thing. That’s when they are most active–like people. They can survive temperatures between 40F and 120F, below which they become inactive, and above which they start dying off–like people. Spoilage mechanisms (autolysis) in meat also operate at their fastest rate between these temps–even though there may not be any bacteria present, meat can still spoil. Since Pasteurization does not actually sterilize, there may be a FEW target bacteria left in your SV item after processing–just not enough to gain a foothold in your digestive tract. However, exposing them to beneficial temperatures can encourage them to multiply, so it’s not really about SV so much, as it is about ALL cooked food. That pizza that you left out on the table the night before, the turkey that remains on the counter all afternoon after your Thanksgiving meal, these things are invitations to pathogenic cross contamination and autolysis. Steps must be taken to avoid spending extended periods of time in those temperature danger zones, both on the way up, and on the way down.
Shocking Pittsburgh Blue
Tender steaks prepared sous vide have captured the imagination of enthusiasts. They come out perfect medium rare all the way through. So why would you shock a steak that you plan to eat right away, and medium rare, for that matter? As it turns out, there are different degrees of shocking.
Now that you have removed your Choice Rib Eye steak from the bath, do you need to shock it? Well, no and yes. Simply put, you don’t need to shock it down to 70F if you plan to eat it within the next half hour or so. And if you DO shock it all the way, there’s a good chance it will not be medium rare when you rekindle it. BUT, if you shock it down 10 or 15 degrees, the time it spends over the coals in your bbq will not further increase the internal temperature that you were so careful to achieve.
This means you remove the bag from the bath and relax. It’s sealed. It can sit on the counter for a few minutes. Good Lord, if we were as nervous about the other foods that we mistreat as we are about these few moments, what kind of anxiety medications would we need? I hope that clarifies this middle ground issue!
Okay, where was I? Oh, right! Shocking refers to taking steps to quickly reduce the temperature of SV items after they have been processed. Unknown to most, Pasteur realized the importance of this; quick chilling was as much a part of his methodology as the pasteurization itself. If you pasteurize proteins and then just let them cool at room temperature, they will probably not become toxic as a result of pathogenic contamination. But they will still spoil.
So, cold shocking is a safety measure with aesthetic benefits. We’re not talking about minutes here. We are talking about hours. Although there is some latitude in interpretation, the legal standards that are generally enforced forbid food from spending more than four hours in the temp danger zone–again, on the way up, and on the way down, combined.
Like I said, if you plan on serving your Sous Vide item immediately, there is no food safety reason for shocking it–but there is an aesthetic one. If you plan to remove your project from the sous vide bath and save it for later (the most commonly applied practice with the exception of items served Rare or Medium Rare), you should temperature shock that food all the way. Here’s how you do it:
I know it’s Shocking – But Many People Skip the Last Paragraph of an Article
After your project has spent its appointed time in the bath it should be cooled to no hotter than 70F as quickly as possible. Putting it in the refrigerator or freezer will NOT accomplish this because air is a notoriously bad conductor of thermal energy. In fact, putting food that is warmer than 70F in the refrigerator puts the OTHER food in there in jeopardy because of exposure to unsafe temperature. The best way to achieve 70F right out of the bath is to plunge your product in at least twice its volume of cold water, preferably with ice. Hence the term “Shocking.” Do not pack it in ice alone–again, this will cool the food too slowly. The bag needs to be in direct contact with water to chill, just as it needed to be in direct contact with water to cook.
But Wait! There’s still MORE!
In conclusion, food safety always comes first. Period. But, like I said, there are aesthetic reasons to shocking sous vide processed items. Once chilled to basic refrigerator temperatures like 40F, most foods can then be treated “as raw” to achieve the desired appearance without sacrificing the benefits of SV. This means you can roast, grill, saute, bbq, whatever, just as if the product was fresh out of the bag until you get the desired appearance you are accustomed to, without worrying about whether or not that chicken is still pink on the bone, etc. You’re guests will be amazed at your deft and prompt delivery of perfectly cooked ribs and steaks, wondering how on earth you did that!
A Note on Retherming.
If you treat your food lovingly on the way up and then on the way down again, you want to make sure you use safe practice when you decide to retherm. I have observed people advocating retherming via sous vide to a lower target temperature than the original target, and this is really not a good idea. The same safety guidelines exist regardless of whether or not the food has been pasteurized if only to avoid autolysis. Sous vide is not necessarily the best application for retherming because time spent in the danger zone is cumulative. Most traditional methods spend LESS time in that danger zone than sous vide does.
So, for me, once I’ve taken that chicken or pork or whatever up the ladder and then gently lowered it down again, I leave it sealed in the bag until the day of service. I crack the bag, and saute, roast, bbq, grill, baste, deep fry, boil, whatever (did I forget any?) just like it was never processed in the first place. Just like sous vide never existed.
Some people want to argue that if you’re going to do that, why would you sous vide in the first place? I have engaged in these debates, but, ultimately, I rely on that old truism:
The Proof is in the Pudding
Here is another reinforcing link http://www.hi-tm.com/Documents/Chillfd.html