Correct vacuuming.

Basic tips regarding vacuuming can be found in the section “The basics” under “Vacuuming”. Here we talk about selection of the right vacuum device, list the advantages and disadvantages of each and explain what needs to be considered when it comes to vacuuming.

External vacuum sealer or chamber vacuum sealer?

External vacuum sealers are the more compact and lightweight options when it comes to vacuum units. They are available in various versions and sizes. Entry-level units for household and occasional use can generally seal bags up to a maximum width of 30 cm with a single seam. Larger and more convenient devices offer sealing widths of around 40 cm and seal the vacuum bag with a double seam, which is particularly advantageous for food with a higher liquid content.

An adjustable vacuum intensity is recommended so that soft and more sensitive food is not compressed too strongly. Some devices also offer the option of using special vacuum containers with the connection of external hoses. Using the marinate function, meat or fish can be marinated in a relatively short period of time using this type of container. In this case, vacuuming is automatically timed so that the marinade can be absorbed more quickly due to the pressure differences created.

If you regularly vacuum pack food of different sizes, then a built-in roll holder for film rolls can be practical. Preferably in combination with an integrated cutter to cut the film tube to the right length.

A fundamental advantage of external vacuum sealing is that the length of the vacuum bag is in principle not limited because it remains outside the device instead of being placed inside. Theoretically it would be possible, for example, to vacuum seal a two meter long fish, though in this case you would also need a Sous Vide bath tank of at least the same length as well as a suitable pan if roast aromas are needed at the end.

However, external vacuum sealers are problematic when it comes to vacuuming liquid foods or foods with a high moisture content. In addition to the air in the vacuum bag, they also suck in fluids, which is naturally not at all desirable. Unfortunately, there is no good solution for this problem; the more moisture a food contains, the more problems there are when vacuum sealing it. If sauces, soups, dressings or other fluids should be vacuum sealed then this is incredibly difficult and problematic with an external vacuum sealer. The emergency solution to use external vacuum containers for this - as sometimes advertised - is not practical, because these are of course not suitable for cooking sous vide.

Summary: External vacuum sealers work well if primarily low moisture food is to be vacuum sealed. They are relatively economical and compact, but do not achieve the high vacuuming performance of chamber vacuum sealers. Many devices require a cool-down break between sealing processes, which can quickly become a test of patience when preparing large quantities of food. Low weight and relatively minimal space requirements mean that they are best for mobile catering or private household use. In addition to this, they can only be used with embossed vacuum bags, which can be expensive in the long term.

Chamber vacuum sealers are the universal specialists when it comes to easily vacuuming moist and liquid foods. Their high-performance, oil-lubricated pump units are designed for continuous operation and a high cycle sequence, with adjustable vacuum intensity making the vacuuming of extremely pressure-sensitive food possible.

The technical functionality of chamber vacuum sealers, also known as vacuum packaging machines, is fundamentally different to external vacuum sealers. In a chamber vacuum sealer, the entire vacuum bag is positioned in the vacuum chamber of the device and placed with the open side up on the opened sealing bar. After the lid is closed, air is sucked out of the vacuum chamber, though at this point the bag does not yet cling to the food inside it; there is therefore no leakage or pushing out of fluids.

Only once the desired vacuum intensity has been achieved does the sealing unit and sealing process start to hermetically seal the bag or bags (some units have more than one sealing bar). Finally, the vacuum chamber is ventilated again and the ambient atmospheric pressure presses the film of the vacuum bag seamlessly onto the food inside it.

Because the vacuuming process takes place with an open bag, chamber vacuum sealers are able to use economical sealing edge film bags but external vacuum sealers require special, internally structured film bags.

When selecting the right chamber vacuum sealer it must be ensured that the vacuum chamber is sufficiently large, as only things that fit in the chamber can be vacuum sealed. If in doubt it is therefore generally better to err on the side of purchasing a larger unit as insert plates can be used to reduce the effective chamber size when vacuuming smaller quantities of food so that the vacuum is created more quickly and economically.

Another practical aspect is digital control with memory locations for frequently used programs, which can store optimal parameters for the vacuuming and sealing process once these have been established, and then recall them at any time. This saves time and ensures perfectly reproducible results for the respective food.

There are also trolleys available for many table-top models, so that the vacuum unit doesn’t take up any space on the work surface and can also be flexibly positioned within the kitchen.

For simple and hygienic cleaning, the sealing bar should be able to be taken out as easily as possible, and the vacuum chamber itself should be made of stainless steel. A smooth design with a stainless steel chamber, without difficult to reach corners or areas, ensures long-term hygiene.

The vacuuming process causes the chamber pressure to drop below the normal ambient air pressure and fluids start to boil even at room temperature while cold products are cooked. A so-called steam sensor is recommended here. The sensor function immediately and reliably recognizes steam escaping from the liquid product. If the sensor signals that the boiling point has been reached, the machine stops extracting the air and starts sealing the bag. This stops the vaporized fluid from entering the pump or the oil and causing long-term damage.

Summary: Chamber vacuum sealers are the more technically sophisticated solution, especially if moist or liquid food needs to be vacuum packed. They achieve a better vacuum than external vacuum sealers, which also increases product shelf life and therefore enables longer storage periods. Use of economically priced sealing edge or tubular bags (PA/PE) offer a cost benefit, short cycle times and are suitable for continuous operation without the need for breaks. Program memory and automated processes leave hardly any room for user error, which guarantees high product safety.

External vacuum sealers & chamber vacuum sealers – the pros and cons:

External vacuum sealer

Relatively inexpensive entry-level models available
Compact and lightweight – well suited to mobile use
In principle there is no limit to the vacuum bag length (though the vacuum pump has its limits…)
Well suited to firm and dry food

Has problems with moist food; not suitable for fluids
Limited vacuum performance compared to chamber vacuum devices
Only more expensive devices are suitable for continuous use
No option for storing individual processes
The device can be damaged by the extraction of meat juice or other fluids
Special vacuum bags with internal embossing required
Pump often generates loud noise during operation
Embossed vacuum bags are relatively expensive

Chamber vacuum sealer

Excellent vacuum performance
Also vacuum packs fluids and moist food without problems
Suitable for continuous operation
Use of economical sealing edge or tubular bags possible
Low cycle times, high working speed
Wide and strong sealing seams
Low pump operation noise
No danger of fluid being sucked out
Adjustable vacuum for pressure-sensitive food
Program memory for perfectly reproducible results and product safety
Long life-time thanks to oil-lubricated pump unit
With appropriate equipment it is also possible to use inert gases

Generally a higher acquisition cost than external vacuum sealers
Size of the vacuum chamber limits the maximum piece size of food
Depending on the size they can be more or less suitable for mobile use

Tips for vacuuming:

The right vacuum bags

An external vacuum sealer requires special film bags that have an internal structure to make vacuum generation possible as the sealing unit presses the film sides together to seal them. Chamber vacuum sealers, on the other hand, can also use smooth vacuum bags.

Vacuum bags are available in various sizes and also as rolls of various widths. If cooking is to be done at relatively high temperatures, it is essential to ensure that the bags are declared as “boil-proof.” There are also various foil thicknesses available, generally between 80 and 160 µm. Standard foil thicknesses are sufficient if the food to be vacuum packed is soft and has no sharp edges. Using thicker vacuum bags is recommended, for example, for vacuuming meat with pieces of bone or food with hard edges and corners, as these bags have a much higher mechanical strength and puncture resistance. High quality vacuum bags are made from two layers: PA (polyamide) and PE (polyethylene), and are certified in accordance with “BRC Global Standard” for hygienic use with food.

Auxiliary devices for vacuuming

Even extra-strong film bags can be damaged if food with particularly sharp edges or pointy bones is vacuum sealed. This can be prevented by using boards that cover these “problem zones” and thus protect the foil bags. The same purpose is served by bone protection linen, a food-safe coated fabric that is placed on the bone or sharp edge to pad it. A so-called “soft air function” slowly and gently returns air into the chamber. This step-by-step process is based on the preset time. The vacuum bag suctions onto the product in a controlled manner. For optimal protection of the product and the vacuum bag.

Especially in the area of desserts, preserving jars are very popular and also have a positive environmental impact. The preserving jars are vacuum sealed at the touch of a button with a special ACS program. With this program, each jar is sealed with a maximum end vacuum of 99.8% in a shortened cycle, as the phases for heating the sealing bar and soft air are not required.

As already mentioned, vacuum sealing of fluid-containing food with an external vacuum sealer is always problematic because fluid is automatically sucked into the area of the sealing unit as air is sucked out of the bag. If fluid enters the area in which the film should subsequently be sealed, this regularly leads to seams that are not perfectly sealed because fluid impairs the sealing process. To reduce this issue there are special, absorbent inserts available on the market that are placed, in the appropriate width, just below the sealing zone inside the bag. During the vacuuming procedure, they absorb fluid and thereby prevent it from entering the sealing zone and the vacuum pump.

How to vacuum seal correctly?

The most important thing first: The area in which the sealing seam will be created should be clean and dry so that there are no leaks. Therefore, when filling food into the vacuum bag always fold the open edge of the vacuum bag over by around 20 mm. This ensures that the inside of the bag remains clean and dry in the sealing area. The bag must be unfolded and flattened before the vacuuming procedure. For multi-layered vacuum bags, the sealing time needs to be appropriately increased.

Care must be taken when vacuum sealing foods that have a soft consistency. If the vacuum is set too high then these foods can be squashed and become unusable. With external vacuum sealers this can be observed in real time and, insofar as there is a controller for vacuum strength, the process can be started with a partial vacuum. With chamber vacuum sealers the right partial vacuum needs to be set in advance, so a little advance testing can be helpful. Once the correct vacuum value has been found for various foods, it can be easily entered into a table for future use or, on the more advanced devices with memory options, it can be stored in one of the memory locations.

Alternatively, very soft or sensitive foods can also, insofar as this is possible, be frozen in advance to make vacuum sealing easier. Although somewhat cumbersome, this can be an option for the occasional processing of soups or sauces with an external vacuum sealer. To ensure that the cell structure of food is not negatively affected with regards to quality, all food should generally be vacuum sealed after being cooled to around +2 °C.