I purchased at the same time as my Anova some plastic bags complete with a didy pump to extract the air and proceeded to use a standard recipe that included a few sprigs of rosemary etc etc. Followed all the instructions but after sucking out the air the sirloin steak within began to take on the apearance of an odd shaped pancake ie really quite thin. After the session in the bath the said sirloin pancake retained its shape and after a quick hot griddle experience tasted more leathery than pancaky. Having traced the procedure I have put it down to the thickness of the plastic. It took quite a time to extract the air using this powerful plastic little pump that came with the bags but I am thinking this is the culprit as it has forced the food into this shape. Does this sound plausible and should I either stop body building with the pump or buy some sensitive light weight versions that won’t flatten everything
For steaks and other foods that will only cook for one to three hours, just use the water immersion technique with freezer-grade zipper bags or resealable silicon bags.
To avoid “pancaked” meats, freeze before sealing unless the vacuum system has a moisture sensor.
Freezing fresh meat to cook it is a bit silly, detrimental to the steak and wasteful of resources. There is a very old fashioned, low tech solution that was invented centuries ago. It’s called string.
Don’t freeze it. Truss it. Wrap a piece of string around the circumference of the steak and tie it tight. Two laps if its a good thick piece. It will help it hold a nice shape.
Thank you and as well as using this string technique I think I will also invest in some lightweight bags
@Glassblower1, I have to ask about your alias. What type of glassblower? Flame worker? Instrument glass? Or the whole shebang with glass furnace, blowpipes and punties?
Hey Glass, i have difficulty understanding how you achieved a leathery taste and attribute that to bag thickness. It does not sound plausible. A texture problem maybe, if sirloin was over cooked.
If you care to share all the details of the sirloin and standard recipe employed without the etc etc items, we might be able to provide you with some corrective measures for the future. Competent SV cooks think in terms of technique rather than recipe.
Meanwhile, don’t take “vacuum” too literally with that pump. You only need to remove the air from the bags that would insulated the meat from the water’s heat, no need to crush the meat. You don’t have to eliminate every minute air pocket.
I was a UK studio glass blower way back in the past but costs of fuel gas etc stopped that one, so yes furnace, lehr, blowpipes and the rest lol
I will try again and be a little more precise with my info when I post. thank you
Cool. I had to ask as I did a few years of hot glass training when I was a uni. One of my lecturers had spent some time at Isle of White glass.
Glass, cooking is a lot like creating glass art.
You start with a plan and think about your expected outcome. Then all the details fill in the middle of your cooking plan.
We have an entire museum devoted to glass art and glass blowing where I live, a little more than a mile down the waterfront from my house.
Unfortunately I think when comparing my cooking capabilities to glass blowing I’m roughly at the “can create a water glass that does not dribble…too much” level. But when it comes to eating…Dale Chihuly move over, I’m the competition! 
I remember dale and Jamie carpenter when they visited the RCA in early 70’s and Jamie was a really good maker
I don’t understand how even perfect vacuum at sea level could result in flattening a steak, no matter what the thickness of the plastic bag was. Bear in mind that your steak was already subjected to the outside air pressure before the bagging and that this pressure was not increased as a result of removing the air from the bag. Why did it flatten? My guess is that your cut was very thin to start with (or perhaps tenderized?). In this case, just the searing would more than cook it through and result in an overcooked, leathery steak. SV is good only if the cut is thick enough to ensure that the inside of the meat remains at or about the temperature of the bath when you sear it.
That’s a common misconception. Before bagging, the pressure inside the steak is the same as the pressure outside. Remove the pressure inside the bag by evacuating most of the air, and the pressure outside the bag is now very much larger than the pressure inside. At sea level, for a vacuum on the inside, that is 14.7 pounds per square inch. In other words, a lot.
Not surprising that soft foods flatten when you have a go at them with a vacuum sealer. Would you expect the average steak to flatten if you put a hundred-pound weight on it? I would.
I beg to disagree entirely, michihenning. The pressure at sea level, as you correctly state, is 14.7 pounds per sq. inch. This is true for any object at sea level, and in this case, a steak, whether it is bagged or not. The fact that you withdraw the air from the bag does not change anything, and in particular does not create a pressure differential between the outside and the inside of the bag, since the bag is supple. The pressure on the steak does not increase or decrease: the atmospheric pressure is exerted through the bag, as opposed to directly on the steak. Therefore, the steak will only get flatter if it contains air (or any gas) that is withdrawn from the bag, like a sponge. So yes if you vacuum bag biscuits, they will be crushed by the air pressure exerted through the bag, but if you bag a steak, which is essentially incompressible at atmospheric pressure, it wont get flatter unless it was — bizarrely —hollow.
Hmmm… This strikes my as entirely incorrect. As a scuba diver, I do know a little bit about pressure differences. Of course, I’ll be happy to learn about the error or my ways.
No, steaks aren’t hollow. Nor are they made entirely of incompressible liquid. Last time I vacuum-bagged a steak, it turned very much flatter than it was before I evacuated the air. I’ve since learned to not do that because it doesn’t work all that well.
Your mileage may vary.
OK. Whatever. I am afraid you are wrong. I am a scuba diver too, but also an aerospace engineer.
Think: steak is made of water (45-75%), proteins, carbohydrates and minerals. None of these are noticeably compressible under 1 atmosphere (and you agree with this). Why should a steak be flattened (i.e. be compressed = decrease in volume) when vacuum bagged? The only explanation is if there are fluids (gases or liquids) trapped in the steak that are expelled and sucked by the pump (or transfer to the bag, outside the steak) when vacuum is applied. The displacement of these fluids results in the steak changing shape. There is no other way, at normal pressure.
And one last thing: everything at sea level is subject to 1 atmosphere of pressure. The bag, the steak, the steak in the bag, whether or not the same is sealed or vacuumed. You can pump the bag all you want, you will not decrease the pressure in the bag below 1 atmosphere because the bag is flexible. If this were a rigid airtight container, yes, then pressure would drop, potentially to zero if you had a perfect vacuum pump.
Simple solution @chiara, put a boneless steak in a vac bag, suck the air out and observe it yourself.
Done many times. Bags molds around steak. Steak stay put, does not change shape.
You are both right, sort of. Vaccum bagging is extensively used in
industry (and by enterprising hobbyists) for molding and clamping. It
can generate massive force. However the force generated depends on the
force of the vaccum applied. If you barely remove the air then stop
there will be no squashing of the steak (the ziplock technique.) If
you use a powerful enough pump the steak will become liquid and be
squashed into a sphere. In the middle pressure ranges it will merely
flatten. Taking ALL the air out to get the full theoretical 14 lbs per
square inch difference between the pressure in the bag and out is
actually impossible. It requires creating a perfect vaccum which like
absolute zero temperature can be approached as close as you want to
work at it but is never attained. Even getting close is quite
difficult. Your average inexpensive vaccum sealer does not pull a very
powerful vaccum. It doesn’t need to. Squashing all your food into
spheres would be annoying.
Summary: Whether a steak flattens or not in a vaccum bag depends on
how strong a vaccum pump you use.