Vacuum coking of fresh meats.



Vacuum cooking is not a new concept by any means but searching online for professional documentation always sent me towards the industrial sector with experimentations on fresh meats or fish. As my primary sector is retail I have tried to adapt the newly discovered techniques to a more artisan fashion.
 Vacuum cooking brings some advantages that would not be possible with other techniques like the possibility to cook contemporaneously different type of foods, we can cook beef meat and fish at the same time with bought any flavour contamination whatsoever.
Vacuum sealing, as we all know, is not a cooking method nor a preservation one. It is a packaging method. With this in mind vacuum packaging is indispensable to the retailer or the hospitality sector operator. For example it increases shelf-life, flavours and colours are preserved and it can even make meats more tender by modifying the glycogen present in them.

Ingredients.

For vacuum cooking a modern retail kitchen should have a steam capable oven , a vacuum sealing machine and a blast chiller wich is mandatory for good results with the vacuum cooking. The nice thing about this cooking technique is that it transforms a simple packaging method in a preservation one but for this we need to follow some basic rules in the production chain. First of all is hygiene as the possible contamination of foods before their sealing will compromise their shelf-life. Another factor to keep in mind is the time that foods will be outside of the fridge before the actual cooking is started and anyway that should occur at a inferior to 10°C room temperature.

Ussage

The correct usage of the oven is the key factor of our success and although it is a complex mater here are some guidelines. Always use preheating with a chamber temperature superior of 30°C over the cooking temperature for products that are usually stored at 3°C or a chamber temperature of “cooking temperature”+50°C for frozen foods. Using a temperature probe during cooking is preferred to the “cooking time” approach. One problem that I encountered with the temperature probe was that the vacuum was lost even though we used some sort of sealing sponge on the packages to be coked. As a backup solution I've used one non sealed meat cut only for temperature probing, so if someone has some better ideas please comment in the section below.
 
The blast chiller needs a pre cooling stage too. Take into account that although we might set a 3°C chamber temperature for the chiller , without a proper pre cooling the temperature drop will last long over 90 minutes and that is not desirable for good conservation.


 

The vacuum bags

That brings us to consumables. There are allot of vacuum bag types but the one appropriate for cooking will be PA/PP material at 80 micron thickness. This material can resist temperatures 100 to 120°C and can guarantee a 30 day shelf-life for refrigerated products.

 Taste and flavour

When we think of cooking we think of flavours, and flavour management with vacuum cooking can be a tricky thing. One thing to consider is that the salt quantity to be used per kilogram of product might vary with the way your clients perceive flavours or by the type of product , vegetable , meat or fish. There are some other problems related to salt and that is it's purity from a microbiological point of view. The marine salt for example can have a bacterial load that combined with the anaerobic way of packaging will create that green liquid inside the bag wich is nothing more than the biproduct of the metabolism of halophilic bacteria. So keep an eye on your salt. Sugar is also used in different percentages mainly because it balances the salt flavour and helps preserving foods by absorbing water. It also helps preserving the colour of fresh foods for a much longer time.
Depending of your needs you can, for vegetables use 60 % salt 40% sugar then dosing that 20g per kg of finished product. For red and white meats 65% salt 35 % sugar with a dosage of 9 grams per kilogram. For fish use 65% salt 35% sugar with a dosage of 10 to 12 grams per kilogram of product.
Also spices along with oils can be used to create marinades with the help of vacuum coking helping in the creation of particular fragrances thus giving a longer shelf life for the newly created aromatic oils. With fresh spices use the vapour oven to cook them for 2 minutes at 100°C then vacuum cook them together with olive oil for 30 minutes at 50°C.
Vacuum cooking , at least for meats brings some hard to get otherwise advantages. One is the fact that flavours will be evenly distributed inside the cooked product thanks to the mechanical effect of the vacuum. Another one is the fact that colours will be preserved much longer. This is particularly convenient for restaurants for example , where large batches of products can be cooked then used only when the client requires them. The long cooking time combined with proper cooking temperatures also provide a efficient way of destruction of any latent bacterial load. Also during storage it will be difficult that any contamination can occur. Vacuum coking will prevent excessive weight loss. My personal experience was that cooking in a traditional way 1 kg of frozen prawn tails will result in a weight loss of 50 to 55%. Vacuum cooking will reduce that to a loss of about 40% always thanks to the mechanical action of the vacuum which will prevent water escaping the product mass. This has also demonstrated to be true for beef and vegetables.
One side effect of the mechanical action of the vacuum is the fact that flavours are more intense than traditional cooking. Just think about of the dilution and lost of juice from a traditionally boiled product compared to the closed ambient of a vacuum bag. So keep in mind this factor when using spices or additives.
Although anyone should get temperatures through experimentation and there are allot of factors that influence cooking like the oven performance , quality of meats, correct reading of product and chamber temperatures etc. below there is a list of vacuum coking temperatures:

  • 50°C oven chamber temp.(C.T.) - avoid this as it is dangerous from a bacterial proliferation point of view
  • 60°C C.T. and 54°C product temp.(P.T.) for roast beef with raw interior
  • 60°C C.T and 58°C P.T. for cooked beef
  • 68°C C.T. and 66°C P.T. for well cooked beef and pork
  • 75°C C.T. and 72°C P.T. for well coked chicken, beef or boned pork
  • 85°C C.T. highest cooking temperature based on the quality of your cooking bags 


Reheating of cooked products.

Reheating of the already cooked products is almost mandatory at least for the hospitality sector operators. It can be done in 2 ways : using the steam oven and keeping the product sealed in his vacuum bag or second alternative , opening the bag and cooking the product in a traditional way with the instruments present in your kitchen. If your meat cuts are big the first way can take a long time and you should keep that in mind.
Products reheated with the first method can also be immersed in hot water at 65°C and kept in stand by until further cooking is required, depending on your client requirements.
Generally there are some rules to be followed when refrigerated products are served with the reheating method and not only. For example foods to be served cold should not stay outside of the 3°C temperature range for more then 30 minutes before they are consumed. The reheating process should occur possibly just before foods are served. If they are not served , the reheated products are to be eliminated and anyway the reheating process should not last longer then 30 to 40 minutes and the stand by temperature should not be lower than 65°C.

I hope that this article gave'd you some nice ideas on how to cook, preserve foods and how to overall maximise gross profit for your business. For further info don't hesitate to contact me.
Enjoy your meal.

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