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{"activity_order":null,"activity_type":["Technique","Science"],"assignment_recipes":null,"author_notes":null,"cooked_this":0,"created_at":"2013-03-01T01:48:24Z","creator":null,"currently_editing_user":null,"description":"Although chamber-style vacuum sealers are large and relatively expensive, they do an excellent job of quickly sealing food in airtight plastic packaging. Their powerful vacuum pump and large chamber gives them the ability to quickly seal multiple bags of food at the same time, which are important benefits in a restaurant. Moreover, unlike edge-style sealers, the pressure in the chamber and inside the bag are nearly always the same, so the sous vide bag never collapses. This approach has the advantage that liquids tend to stay put rather than being sucked out the open edge of the bag. Finally, chamber-style vacuum sealers enable various novel culinary techniques like <a href=\"http://www.chefsteps.com/courses/accelerated-sous-vide-cooking-course/vacuum-compression-of-plant-foods\" target=blank>vacuum-compression</a> or vacuum-infusion.","difficulty":"","featured_image_id":"{\"url\":\"https://www.filepicker.io/api/file/jcsW1pbZTXCJsxwrXi9C\",\"filename\":\"Chamber_Sealer_1.jpg\",\"mimetype\":\"image/jpeg\",\"size\":260333,\"key\":\"BiTDSa0nQOjcyKzCrX6w_Chamber_Sealer_1.jpg\",\"isWriteable\":true}","forks":[],"id":186,"image_id":"","include_in_gallery":true,"last_edited_by_id":null,"likes_count":3,"published":true,"published_at":"2013-03-01T01:48:24Z","show_only_in_course":false,"slug":"how-chamber-style-vacuum-sealers-work","source_activity_id":null,"source_type":0,"summary_tweet":null,"timing":"","title":"How Chamber-Style Vacuum Sealers Work","transcript":"Chamber-style vacuum sealers have become an essential kitchen tool in restaurants that have embraced sous vide cooking. These large appliances are relatively expensive, but they do an excellent job of quickly sealing food in airtight plastic packaging.\r\n\r\nUsing this kind of sealer is easy; simply lay a sous vide bag filled with food into the chamber, place the open end of the bag over the sealing bar, and then tuck the end of the bag back down into the chamber. Close the lid to engage a powerful vacuum pump that evacuates air from inside the chamber.\r\n\r\nAs the pressure inside the chamber falls, the outside pressure actually holds the lid shut. Eventually, the chamber pressure drops to a preset level, or reaches a point where the pump cannot draw down the pressure further, and this triggers the sealing bar to heat up and fuse the plastic bag closed. The machine is then vented to restore the pressure inside the chamber to atmospheric pressure. At this point, the package of food is no longer under a vacuum. The food inside the flexible bag experiences the same pressure it did before being vacuum packed. And with the air pressure inside and outside the chamber the same, the lid swings open. \r\n\r\nUnlike edge-style sealers, or improvised techniques like water displacement packing, the bag doesn\u2019t collapse and shrink against the food until the sealing cycle is complete. This approach has the advantage that liquids inside a bag tend to stay put rather than being sucked out the open end of the bag. \r\n\r\nA second advantage of chamber sealers is their high-throughput. With a powerful vacuum pump and a chamber large enough to seal multiple bags of food at the same time, a single machine can seal hundreds of bags of food in a day\u2014an important capability in a busy restaurant.\r\n\r\nBut even if production capacity isn\u2019t an essential need, the ability of chamber sealers to lower the pressure surrounding food to nearly one one-thousandth of normal pressure enables novel culinary techniques like vacuum-compression and vacuum-infusion. These culinary techniques are only possible with this modern kitchen tool.","updated_at":"2013-06-07T11:02:34Z","upload_count":0,"used_in":[],"yield":"","youtube_id":"0IRO9C4m5yI","tags":[{"id":33,"name":"sous vide"},{"id":149,"name":"vacuum sealing"},{"id":150,"name":"chamber sealers"},{"id":151,"name":"multivac"}],"equipment":[],"ingredients":[],"steps":[{"activity_id":186,"audio_clip":"","audio_title":"","created_at":"2013-03-01T01:48:24Z","directions":"* Start by placing the food into a sous vide bag. A good technique is to fold back the top of the bag. Doing this helps keeps the top of the bag clean where it will be sealed. Food debris where the bag is sealed can weaken the bond and cause the bag to leak during cooking. Folding back the opening of the bag also makes it easier to get food inside the bag, without also getting ingredients on the outside of the bag. \r\n\r\n* It is sometimes said that folding back the bag damages the plastic in a way that makes it slightly more permeable to air over very long periods of time. But in a restaurant or home kitchen, this isn\u2019t a practical concern.","hide_number":null,"id":607,"image_description":"","image_id":"","is_aside":null,"presentation_hints":{},"step_order":8388602,"subrecipe_title":null,"title":"Packaging the Food","transcript":null,"updated_at":"2013-04-05T22:47:41Z","youtube_id":"","ingredients":[]},{"activity_id":186,"audio_clip":"","audio_title":"","created_at":"2013-03-01T01:48:25Z","directions":"* Once the food is packaged, it\u2019s placed into the chamber-sealer. The open end of all the bags should go over the sealing bar, and then be tucked back down into the chamber. Double-check that the edge of the bag does NOT protrude from the chamber, and then close the lid firmly to engage the vacuum pump and start the sealing cycle.\r\n\r\n* If the bag sticks out of the chamber during the sealing cycle, there is no way for air inside the bag to escape as the surrounding pressure is lowered. As a result, the bag will appear to swell as the pressure inside the bag becomes much greater than within the chamber. If this difference becomes large enough the bag will burst, which can be messy.","hide_number":null,"id":610,"image_description":"","image_id":"","is_aside":null,"presentation_hints":{},"step_order":8388603,"subrecipe_title":null,"title":"Loading the Chamber Sealer","transcript":null,"updated_at":"2013-04-05T22:47:41Z","youtube_id":"","ingredients":[]},{"activity_id":186,"audio_clip":"","audio_title":"","created_at":"2013-03-01T01:48:24Z","directions":"* Once the food is placed into the chamber and the lid is closed, the vacuum-sealing cycle begins. For most solid foods, reducing the pressure to 5\u201350 mbar and then sealing the bag will produce a tightly sealed package. At 50 millibars, about 95% of the atmosphere has been removed; at 5 millibars about 99.5% of the air inside the chamber and packing is gone. Although this is a very small difference, it does affect how snugly the bag will tighten around the food. At 50 millibars, there is just enough air left inside the packaging that it cushions the bag slightly when atmospheric pressure is restored to the chamber. At 5 millibars the bag will shrink very tightly around the food. Exactly how far you should lower the pressure, and thus how tightly you should seal the package, depends on what you are sealing. \r\n\r\n* Fragile foods that can be damaged by the contracting bag can be sealed for storage at 200\u2013500 mbar.","hide_number":null,"id":608,"image_description":"","image_id":"","is_aside":null,"presentation_hints":{},"step_order":8388604,"subrecipe_title":null,"title":"The Vacuum Sealing Cycle","transcript":null,"updated_at":"2013-04-05T22:47:41Z","youtube_id":"","ingredients":[]},{"activity_id":186,"audio_clip":"","audio_title":"","created_at":"2013-03-01T01:48:25Z","directions":"* Because air rushes out of the chamber more quickly than it escapes the bag, the pressure will at first be slightly higher in the bag than the surrounding chamber, which will cause it to puff up inside the chamber. Although the bags puffing up is normal, this effect can cause the ends of the bag to slide off the sealing bars, which will prevent the package from being sealed at the end of the cycle.","hide_number":null,"id":611,"image_description":"","image_id":"","is_aside":null,"presentation_hints":{},"step_order":8388605,"subrecipe_title":null,"title":"Why the Bags Puff","transcript":null,"updated_at":"2013-04-05T22:47:41Z","youtube_id":"","ingredients":[]},{"activity_id":186,"audio_clip":"","audio_title":"","created_at":"2013-03-01T01:48:25Z","directions":"* The bag needs to be sealed closed at the end of the vacuum-sealing cycle so that air cannot rush back into the bag. This is done with heat-sealing bars. The longer these sealing bars stay hot, the more plastic will be melted. For standard sous vide bags, a sealing time of two to three seconds is adequate to fuse the bag closed. You may need to adjust this for bags made from thicker or thinner plastic.","hide_number":null,"id":609,"image_description":"","image_id":"","is_aside":null,"presentation_hints":{},"step_order":8388606,"subrecipe_title":null,"title":"The Heat Sealing Step","transcript":null,"updated_at":"2013-04-05T22:47:41Z","youtube_id":"","ingredients":[]},{"activity_id":186,"audio_clip":"","audio_title":"","created_at":"2013-03-01T01:48:25Z","directions":"* Once the sealing bars have done their job, a valve opens and the chamber refills with air. Because the bag is now sealed shut, air cannot get inside it, and so atmospheric pressure forces the plastic bag to collapse snugly around the food, completing the sealing cycle.\r\n","hide_number":null,"id":614,"image_description":"","image_id":"","is_aside":null,"presentation_hints":{},"step_order":8388607,"subrecipe_title":null,"title":"The End of the Vacuum Sealing Cycle","transcript":null,"updated_at":"2013-04-05T22:47:41Z","youtube_id":"","ingredients":[]}]}