Basic techniques-Kitchen vacuum
To cook in a vacuum is to place a food inside a container (bag or tray) that is watertight and heat-resistant, extract the air inside, seal it tightly and subject it to the action of a heat source, to which the constant temperature and the time necessary for get to cook the food.
The interest in sous vide cooking comes from a "more" taste and a practical side of delayed restoration. The cooking It is performed at a temperature below 100 degrees in a humid environment, and will necessarily be followed by a rapid drop in temperature in the cooling cell.
The storage time in the refrigerator at +3 degrees is limited, between 6 and 21 days, depending on the type of product and the preparation conditions. But the taste-level effects differ, so the kitchen vacuum should be considered not only as a facility, but also as a new technique independent culinary.
It consists of cooking the packaged food at low temperature and for a period of time longer than that used in traditional cooking. The action of heat is exerted on the entire surface of the food at the same time, it penetrates inwards uniformly, maintaining the texture and concentrating its aromas.
This procedure has the following advantages:
- It better preserves the dietary, hygienic and organoleptic qualities by preserving all the volatile and water-soluble substances in the food, especially the aromatic components.
- Reduces weight loss by avoiding evaporation and drying. It prolongs the conservation time (from 6 to 21 days).
- Simplify and streamline the service, you just need to heat the portion, heat the plate and serve.
- Streamlines work planning.
- Preparation and cooking outside the service period, anticipation of the preparation of banquets, improves the use of quiet moments, etc.
The cooking technique
It is done at temperatures that range between +65 and +100 degrees, depending on the products, although most of them are usually cooked between +65 and +85 degrees. A water bath with a thermostat or a so-called “low pressure or wet steam” steam oven can be used for this.
The second system is revealed to be more effective due to its greater reliability in terms of temperature regulation. Low-temperature cooking dissolves collagen (the intercellular substance of the connective tissue of animal meat) and the relationship between the temperature and the time used for cooking the collagen are directly involved in the hard or tender texture of the meat.
When heated in the presence of salt, the collagen dissolves, promoting a softening of the meats. Towards +54 degrees collagen contracts due to the effects of heat, which leads to a hardening of the meat. Towards + 80 / + 85 degrees, in a humid environment, the collagen softens again and allows the formation of gelatin. Towards +100 degrees, and at higher temperatures, the turbulence of the boil causes the collagen to evaporate and the meats become dry and spicy.
Another characteristic of vacuum cooking concerns the necesidad from a humid environment, either internal, because water is part of the product in considerable quantities (for example, legumes and young vegetables), or external, that is, adding water in minimal amounts in the bag before welding them for cooking ( dry legumes will have to be soaked for hours to be cooked, instead a single tablespoon of water is enough for 1 kg of potatoes or carrots)
To keep in mind:
- The temperature must not vary in parameters higher than +1 degree during the entire cooking.
- The temperature must be identical and not vary more or less than +1 degree at all points of the cooking chamber.
- The temperature drop must be made immediately after cooking, for this it is best to use a rapid cooling cell. Indispensable tool to achieve a good guarantee of conservation. Whether operating with mechanical, cryogenic or immersion cold, the cooling cells must be able to ensure the drop in temperature in the center of all products to less than +10 degrees and in less than 2 hours.
- The recovery of the service temperature will be done with the same bag using the systems indicated for the precooked ones, but always above +65 degrees and in less than 1 hour.
- Once the product has been reheated, if it is not served, re-cooling for later use is strictly prohibited.
Particular attention should be paid to the following points:
- The products that will serve to prepare the dishes must be kept at the appropriate temperatures.
- The products, once made, must be cooked immediately after vacuum packing.
- Cooking must be followed by rapid and immediate cooling.
Products cooked before vacuuming.
Some culinary preparations (stews, civets, sauces, soups. Etc.). they require to be cooked before packaging. In this case, the cooking will be carried out using the traditional system required and will be packed before reaching the critical temperature of +65 degrees. They will immediately be placed in the cooling cell, to provide a rapid and complete temperature drop.
Products that require “prior marking”.
Products that, for culinary or presentation reasons, must be "sautéed or browned", that is, colored by the caramelization action when passed through a hot fat, will be packed immediately after this operation has been completed and then cooked under vacuum. The greatest advantage this procedure offers is undoubtedly weight reduction.
Indeed, if for example we prepare a round of veal by the traditional roasting or braising method, we must calculate that it will have very high weight losses, around 45%. On the other hand, if we simply color it and then package it and cook it under vacuum, these losses become approximately 10%. Interesting, right.
Vacuum cooking times according to the products
- Double the normal time
Veal and Beef, Fillets, Sirloin, Roastbeef, Lamb, Gigot, Shoulder, Carré, Game, Pigeon, Partridge, Deer, Wild boar.
- Half more than normal time
White meats, Veal, Ossobuco, Sauteed pork, Poultry, Chickens, Poulardas, Quails, Rabbit.
- A quarter more than normal time
Steamed fish, Kettles and fish stews, Stuffed fish, Molluscs, Crustaceans without their shells, Fish pates.
- The normal time required in the traditional cooking system
Vegetables, Vegetables, Natural fruits, Fruits in syrup, Dried legumes (after soaking).
This table is indicative, the exact time for each product will obviously depend on the size and thickness of the portions.
Vacuum cooking temperatures
Vegetables, Fruits, Vegetables (100 ° C)
· Fish, Seafood, Patés. (90 ° C)
· White meat, Poultry, Fish. (80 ° C)
· Red meats, Roasts, Sauteed. (70 ° C)
Microbial development risk areas
· + 120 ° C. STERILIZATION Death of all microbes.
· + 100 ° C. PASTEURIZATION Death of some pathogenic microbes.
· + 65 ° C. ZONE OF MAXIMUM RISK.
· + 15 ° C. RISK AREA TO BE TAKEN INTO ACCOUNT.
· 0 ° C. SLOWLY MULTIPLICATION OF GERMS.
·.-18 ° C. FREEZING LYOPHILIZATION.
· -30 ° C. DEEP FREEZING. Stop all microbial multiplication.
Preservation and labeling of packaged products
To avoid surprises when consuming the product, it is essential to label the bags with: the type of product packed, the date of packaging and expiration, "consume before ..." Stick to the sealed envelope. Never use a marker directly on the bag. Once the product is cooked, vacuum packed, rapidly cooled and labeled, it is ready to be stored in the refrigerator at + 2- + 3 degrees until it is used. Or frozen to keep it much longer.
Storage and freeze expiration time.
· From 6 to 21 days: + 2 ° C - compensated normal vacuum.
· Up to 12 months: - 18 ° C - vacuum + freezing.
Service temperature recovery methods
To return the food to service temperature it must be done instantly when taking it out of the refrigerator and taking care that the operation does not last more than 1 hour.
The methods to be used are the following:
· Water bath
· Convention oven
· Steam cooker
· Immersion in hot water
· Traditional methods (frying pan, casserole, deep fryer, etc.)
The advantages of freezing vacuum-packed products
Food freezing techniques with the traditional systems normally available preserve the product, but not the quality that it had at the time of its freezing. Using vacuum packaging protects foods, which retain their initial quality.
- · Burned exterior. Freeze Normal YES Vacuum Freeze NO
- Fat oxidation. Freeze Normal YES Vacuum Freeze NO
- Weightloss. Freeze Normal YES Vacuum Freeze NO
- Adapt odors from other products stored on the same site. Freeze Normal YES Vacuum Freeze NO
- It crystallizes. Freeze Normal YES Vacuum Freeze NO
- It loses aroma and flavor. Freeze Normal YES Vacuum Freeze NO
As we can see the advantages are considerable.
- For immediate consumption:
- By immersion in hot water without opening the bag.
- Putting the bag in the convention oven.
- Putting the bag in a steam cooker.
- With the help of a microwave oven. This procedure is not the most appropriate, since it is necessary to puncture the bag several times with a needle, otherwise the bag would explode inside the oven. Vacuum food frozen at -18 ° C can also be thawed slowly in a normal refrigerator, keeping its quality for three days.
- Cutting surfaces that are typically dried, packaged stay cool.
- Frozen foods lose 6 to 8% weight by drying, vacuum packed does not dry out.
- Possibility of preparing portions in greater quantity, therefore greater productivity.
- Possibility of taking advantage of all the cuts for sauces, pâtés, funds, etc. which can also be packed and frozen.
To be successful in the process, it is essential to observe hygiene standards during all handling:
Cooking a vacuum-packed product is theoretically equivalent to pasteurization. This will be more or less efficient depending on the cooking program of each product, that is, cooking temperature per time spent.
In pasteurization, a large number of germs are destroyed, but not all; If, for example, there is a germ content of 100.000 / gram (current ratio) in the initial raw product, after cooking the content drops to 100 / gram. Although it may seem an astronomical decline, there are still germs that can reproduce with amazing speed if the product is not kept at the right temperature, and obviously the number of germs / gram increases proportionally as the level of freshness and quality of the initial product decreases.
The only way to eliminate all germs is sterilization, which is achieved from +121 degrees, which is impossible with the normal means of a kitchen (The espresso pot, despite its appearance, cannot exceed +107 degrees), therefore, to sterilize high pressure steam is essential, that is, an autoclave. Taking into account that the cooking takes place in a closed space under vacuum, the concentration of flavors is much higher, so the use of spices must be very measured.
Dear friends, we leave it for today, we can add some recipes to start, small things but with an excellent result, anyway I keep asking for information, since I know there are super prepared colleagues on the subject, frankly I can contribute little more, and well I'm sorry.
Article published by:Fernando F. Hotel Calypso.