Sous Vide for dummies

*A steak being prepared sous vide*
Erikoinentunnus, CC BY-SA 3.0, via Wikimedia Commons

So what exactly is Sous Vide?

If you have ever been served the most perfectly cooked steak, piece of chicken or fish in an upmarket restaurant, the chances are that it has been cooked sous vide. This technique, which is well known to the professional chef, but is not so accessible to the domestic cook, brings many benefits to the kitchen. Better workflow, less food wastage and almost scientific laboratory levels of temperature control are just some of the key benefits. It is a great method for cooking meat from frozen and allows you to take advantage of those rare discounts in the meat aisle without significant loss of quality at the dining table. It also extremely forgiving from a time perspective, once your dish has reached the desired time/temperature combination, you can leave it in the water bath for many hours afterwards without any loss of quality.

Besides these attributes, this technique is also pretty much foolproof; season and vacuum bag your ingredient, immerse in a water bath at a fixed temperature ensuring that the item doesn’t float and “Boil in the bag” for X number of hours depending on how well done you want your protein. Once cooked, flash fry in a skillet or blast with a blowtorch to add some browning, then serve. Any juices found in the pouch can be used to create a superb jus or thin gravy. Alternatively, rapidly cool the item in an ice bath and refrigerate for up to 14 days. This is the way restaurants will often bulk prepare rare / medium steaks many days in advance, reheating them in a sous vide bath at 55C for 10 minutes, then flash-frying to brown. This way, a medium or rare steak – which would take some experience to cook correctly – can be “Finished off” and served by a less skilled, and considerably cheaper, line cook.

So what exactly is the sous vide cooking method? The French words “Sous Vide” in this context are very misleading, the words themselves mean “Under a vacuum” and refer to the way the meat etc. is packaged prior to being submerged in a heated water bath. You could, of course, cook a solid product without sealing it, but this would cause the juices to leak out and cause contamination of the water and the circulator. This is the reason why a proper waterproof seal on the bag is imperative. Vacuum sealing is only one option of course, glass Mason jars are also frequently used for delicacies such as desserts. What is vital irrespective of how the ingredient is packed, is that all the air is expelled from the packaging so that the water can uniformly heat the contents. Vacuum sealing is the best method for this, but many chefs use thick Ziploc bags, expelling the air manually. It is also important that the item is fully submerged and surrounded by the water. With some meats (especially pork) magnets or a stand are used to secure the packet beneath the water as a lot of juice is released and the bag then floats, posing a food safety hazard.

Food safety and traditional cooking methods

Before we delve into an explanation of how the magic of sous vide works, first we need to have a short discussion on food safety and the more traditional cooking methods. Those of you who have been on a food safety course will know most of this off by heart, but it is surprising how many people don’t, and fall foul of food poisoning as a result. Most perishable foods (with the exception of eggs in the UK and cheese) need to be handled, transported and stored within the “Temperature safe zone” which is between 0 °C and 5 °C. When cooked, raw produce should come up to an internal temperature of 74 °C. Once cooked, food may be kept in “Hot holding” (64 °C) for up to 2 hours, in which case it must be reheated again until steaming hot (74 °C). This process may be repeated multiple times, but invariably leads to a loss of quality of the dish (as does any extended time spent in a freezer). Any food stored in the “Danger zone” (8 °C – 60 °C) must be discarded after 2 hours, 1 hour if it has reached 32°C.

Now the accomplished chef will look at these guidelines with a somewhat jaundiced eye, especially when it comes to beef, chicken or fish. Fish is considered safe to eat at 63 °C, steak anywhere between 49 °C and 68 °C and chicken – the culprit most often associated with food poisoning – 74 °C. The difficulty with these food safety temperature guidelines is that while they are great rule of thumb for the general public, they are overtly conservative (to account for idiots) and will, inevitably, lead to “Cafeteria grade” food. Anyone who has roasted a whole chicken in the traditional method can attest to this. By the time the drumsticks are cooked, the breast will have dried out. This can be negated by stuffing with fruit (e.g. lemons), basting or spatchcocking, but the problem still remains. The traditional oven method uses a high heat over a short period of time to kill bacteria, and by the time the inside and the legs of the bird come up to temperature, the breast will be overcooked. This works in our favour to a degree, as the roasting of the fat layer leads to the sugars being browned and the corresponding Maillard reaction which adds that addictive, roasted flavour. Despite being cooked, anything prepared sous vide will look grey and unappetising hence the optional step of browning.

The magic of Sous Vide

Now we have established that the high-heat short-period cook will make food safe to eat, what if we invert this process and go for a low-heat, long-period cook? Provided we stay within prescribed temperature limits, we can kill those pesky bacteria at a much lower temperature if we expose them to a much longer cooking time than used with traditional methods. This is the basis of pasteurisation, and is one of the greatest benefits of sous vide if you want to serve raw eggs to the elderly, infirm or pregnant. The key benefit is the chef will have complete control over the texture and colour of the dish. The choice is entirely yours, that wonderful piece of steak or chicken can be served from “Disintegrated and falling apart” to “Replacement rubber soles” and everything in-between.

The only down side in providing all of this flexibility is that the temperature must be controlled precisely and it has to be consistent throughout the water bath. A pot sitting on the stove or a slow cooker just won’t cut it, and if you get the temperature wrong, you will be entering botulism territory, which is why any product cooked sous vide must be chilled rapidly in an ice bath and quickly refrigerated if it is not to be consumed immediately. This is also the reason that many sous vide circulators have a fixed lower temperature range to prevent accidental food poisoning.

With a modern water circulator, the temperature of the water can be controlled within 0.5 °C over a wide temperature range, which opens previously unknown vistas to the chef. As sous vide cooking is a function of low temperature over a long time, you can pasteurise eggs for use in mayonnaise or cake batters etc. without significantly altering the raw structure of the whites or yolk. Perfect crème brûlée or zabaglione is possible with minimal effort, and the tenderest, moistest beef, chicken or pork is at your fingertips. Worried about that traditional spaghetti carbonara turning into scrambled egg? Sous vide is your friend. Love perfectly cooked, flaky, fish? Again, sous vide comes to the rescue. As the cooking process is strictly controlled, you will achieve consistent results even with the toughest cuts of meat as the collagen and fat breaks down. Friends and family love to eat at Chez Rookwood, and everyone without exception has been blown away at the quality of the results emerging from my water bath be it beef, chicken or pork ^*.

What you will need

Naturally, there is a downside to all of this excellence. Sous vide kit isn’t cheap, and you can easily spend upwards of £250 on a water bath, circulator and vacuum sealer combination, along with all of the additional accessories etc. Anything with “Sous vide” in the title will attract premium prices on Amazon, Ebay etc. Surprisingly, I have found Nisbets to be a great source for high quality supplies, and they are very good value and quality. You can of course, compromise, and pick up an immersion circulator (which heats and circulates the water) for under £100 and just use Ziploc bags and a large stockpot. You could even just use a clean bucket. The problem here is matching the power capacity and size of the circulator with the capacity of your chosen vessel, the cheaper devices will struggle keeping an even temperature with larger water baths and a smaller bath will severely limit what you can cook. Size is important here, and if you have a large family to feed, a bigger bath will be required for larger meat joints etc. It is absolutely critical that the correct temperature is maintained otherwise there is serious risk of food poisoning, so it is essential whatever setup you use accurately maintains the temperature consistently throughout the bath.

1. The vacuum sealer and bags

As previously mentioned, a proper vacuum sealer is not critical if you are just dabbling your toes in the water, so to speak. A good range of different size, thick, high quality Ziploc bags are available fairly cheaply online or at local supermarkets. Those with a double seal or a proper “Zip” are preferable, but any food-safe sealable plastic bag should be OK. Just ensure all the air is expelled from the bag before sealing, there are lots of videos on YouTube demonstrating this technique using the water displacement method. You can also purchase reusable sous vide bags on Amazon, although I’m not convinced that these are hygienic, as they are quite stiff and cannot be turned inside out easily for cleaning.

My preferred method is to use a relatively cheap vacuum sealer (£25-£50) with BPA free bags which are sold separately (£10 for 100, 10 pence each). The device performs two functions, it sucks all the air out of the bag and then seals it shut by melting a thin strip of the plastic at the top of the bag. The only issue with this method is that it is difficult to vacuum seal meat along with a marinade. While most devices have a moisture trap, inevitably the liquid is drawn up through the bag and can interfere with the seal. There are various “Hacks” to get around this, including adding a folded sheet of paper towel, but I prefer to sous vide my items “Dry”. I’m not convinced that adding oil, marinade or liquid brings much improvement in taste or texture. Depending on the cook time, a certain amount of liquid will escape from the meat anyway, and this can be used the basis for an excellent jus. It is an urban myth that meat vacuum sealed with a marinade will get better penetration and flavour, the only guaranteed way to achieve this is by using a Jacquard to pierce holes in the meat to allow the marinade in.

The final vacuum option is a professional flat-bed chamber vacuum sealer. These are designed to effortlessly vacuum seal produce in a catering environment. The cheapest is around £500 ex VAT and goes up to over £7,500 for a floor standing model. The devices at the lower end of the price range would be useful if you were cooking sous vide a lot in a commercial environment, as the cheaper vacuum sealers don’t last forever. While you pay a premium for the device initially, there is a good chance you will be able to acquire spares for them in a few years time unlike the cheaper consumer grade items.

2. The water bath

This can be as simple or as complex as you want. The major consideration here is matching the power output of your circulator with the volume of water you want to heat and the quantity of food you intend to cook. I use a 200mm ½ Gastronorm polycarbonate container, which costs £17 ex VAT and holds 11 litres maximum. Don’t forget you will need to accommodate your circulator and the food you want to cook, so the maximum effective water capacity is 10 litres for my setup, which should work with most circulators. I can easily cook a family sized joint in that (split in two to fit in the pouches), or four large chicken breasts or steaks. With a sous vide rack, you could probably get 6-8 portions in with a bit of juggling.

Other water bath alternatives include stock pots, buckets, insulated beer coolers etc. The same rules apply, too large a container will cause undesired fluctuation in temperature, even with a lid fitted. On the subject of lids (which are useful to prevent water evaporation over long cook periods), don’t waste your money on a custom lid to match your water bath / circulator. If the latter breaks, sods law says the replacement device won’t fit. You are far better off either using cling film or hollow plastic spheres which can accommodate any model of circulator.

Irrespective of the type of circulator you purchase, you will also need to check that the reach of the device will match the depth of your container. Some circulators have adjustable clamps to accommodate this. Some devices are better suited to round, shallow pots, as they have a very short “Throat”, but ultimately be guided by the desired water capacity etc. Ideally, you will want the water level to rise up approximately half-way on the body of the circulator between “Min” and “Max” levels before you add any food, but the dimensions of the bath will dictate how far the water will rise up the circulator in practice. You will not want that to rise above the “Max” level with a large joint displacing a lot of volume etc.

Of course there is also the professional option, a dedicated heated water bath that negates the requirement for a circulator and a bath. These can be purchased starting at £190 ex VAT for a 12 litre model.

3. The immersion circulator

This is the “Business end” of sous vide, the device that actually heats the water and circulates it at the same time ensuring that the temperature is consistent throughout. These vary in price and quality, but regardless of the make, unless you invest in a ruggedised, professional model you may be disappointed with the longevity of consumer grade units. I have had a quite a few fail on me and it seems to be design flaw of many models that condensation rises up and penetrates the electronics and causes the device to fail. After my last circulator gave up the ghost, I invested in a Buffalo DM868 from Nisbets at £150 ex VAT. This comes with a two year warranty, and like the professional vacuum sealers, spares are readily available. The Joule sous vide circular has built in bluetooth and is controlled via your mobile phone or tablet, but that is over £270. Personally, if I had that available budget I would invest in a water bath as they will last much longer than a portable device.

Professional water baths start at £213 ex VAT and can go up to over £1,400.

4. Essential and non-essential accessories

A probe type food thermometer is an absolute essential as you will need to initially test the water temperature and food temperature as you get used to the tolerance and setup of your kit. Once you get a bit of practice with timings and portion sizes etc. you probably won’t need this, but in the beginning it is extremely useful. I discovered that my Buffalo is 0.5 °C – 1 °C under temperature, but at least I know the water bath is heated consistently throughout, even if it is a little bit out.

Forget a dedicated sous vide bath lid. A better approach is sous vide cooking balls which float on top of the water and help retain the heat and prevent evaporation. Not essential, if you will not be experimenting with long sous vide cooking times (24 hour beef joints for instance), you will not generally need them unless you intend to use the bath in a very cold place such as a garage.

Sous vide magnets and a metal or plastic rack, while not essential, are useful accessories to stop bags moving about and floating in the water. Just keep an eye out on cost, anything “Dedicated” to sous vide seems to be silly money, even a stainless steel rack that would be cheaper for other purposes.

Some final advice

Only use a reputable source for portion size, timings and temperatures etc. If in doubt, always go over time, rather than under. Most recipes can easily handle an extra hour or two without degradation. Different shapes and thickness of meat will take different times to cook. Cooking from frozen will take up to 1.5 times chilled produce times. While getting used to this cooking method, check the internal temperature of the dish at the thickest point.
Different shapes of meat take different times to cook. Always go by “Worse case” scenario, i.e. the thickest and most difficult shape if unsure. It is almost impossible to overcook, but easy to undercook, especially with awkward shapes or meat with bones in.
Do not overcrowd the water bath or pouch. Items need to be 100% surrounded by water. A trivet can be used to prevent items sinking to the bottom of the bath.
Ensure all the air is removed from the vacuum bag as any pockets will act as insulators and the product will not be sufficiently cooked.
Always fold over the top of vacuum bags before filling. Any meat or juices could compromise the seal and cause the non-sterile water in the bath to enter the pouch. While the risk to the individual is very small, the final dish will be compromised and the contaminated water could seriously damage the circulator.
Double bag boned meat. The sharp bones can puncture the bags under vacuum and lead to leaks.
When cooking in Mason jars do not submerge cold ingredients into a hot bath as the glass may shatter. Add the jars when the water is cool, or bring the ingredients up to temperature before adding to the pre-warmed jars. Ensure the lids and seals are clean and dry before tightening finger tight.
If you are in a hard water area, descale your circulator regularly. Failure to do so will cause temperature and control problems.
Only use BPA free bags which do not leech chemicals when heated. These are freely available. While in theory you could sous vide in the vacuum packaging many beef and porks joints are sold in, as the plastic is of unknown origin it may not be BPA free.
Certain joints and types of meat such as pork will release a lot of liquid when cooking. This will cause the item to float if it not secured by magnets, in a rack or weighed down. Any floating items will not be cooked properly as they need to be 100% surrounded by the hot water.
If you are not going to serve your sous vide dish immediately, chill in an ice bath to rapidly reduce the temperature and once cool, refrigerate. Ice or ice packs can be used for this, and a good technique is to empty the water bath of hot water, remove the circulator, add cold water and add ice etc. and submerge the pouches. The water temperature can be monitored with a probe thermometer and fresh cold water added as required. Some people move their water bath into the sink for this purpose.

A very basic sous vide recipe

Chicken with cream and garlic tarragon sauce (Serves 4)

Ingredients

4 boneless skinless chicken breasts
300ml double cream
1 bulb of garlic, crushed
2 tbsp dried tarragon
1 cold cup of chicken stock or white wine (optional, for adjusting sauce consistency)
50g butter
50g flour
Garlic powder, salt and ground black pepper
Olive oil for frying

Method

Fill sous vide batch with cold water, affix circulator and set temperature to 65 °C. The bath will take between 20-30 minutes to come up to temperature depending on bath volume, ambient temperature etc.

Remove chicken breasts from pack and pat dry with a kitchen towel. Lightly season with salt, garlic powder and ground black pepper on both sides.

Using two vacuum pouches, fold the tops over by 2-3 cm and place two breasts a good few centimetres apart in the bag. Roll the top back, and expel as much air as possible by hand, and if possible, continue to do so while vacuuming and sealing. There should be no air gaps around the breast and the plastic should crinkle up around the meat. A few cm gap should be present between the breasts.

Add to the bath and secure with magnets, affix in a rack or weigh down with a small waterproof object. Set your timer for 90 minutes, 120 minutes if using frozen chicken.

If using a chicken stock cube, add to a mug of boiling water and leave to cool.

Once cooked, open a corner of each bag and decant the liquid into a bowl to cool.

Pat dry the breasts with some kitchen towel, and heat 2 tbsp oil in a heavy based frying pan over a moderate heat. Add the chicken breasts and brown on both sides, about 2-3 minutes in total. Remove from pan and set aside.

Over a low heat, melt the butter in the frying pan, fry the garlic for 30 seconds then add the flour and stir to make a paste. Fry gently for 2-3 minutes until the raw flour is cooked out. Add the cold cream, tarragon, a dash of salt and pepper and the liquid from the vacuum bags, stirring continuously. Bring to a simmer, the sauce should be slightly thick, enough to cling to a spoon. If too thick, add some water, wine or chicken stock to thin it out. Conversely, if too thin, reduce until the desired consistency.

Serve with steamed green beans and pan fried potatoes.