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When placing food items in my sous vide bath, often the pouches will rest on the bottom of the bath or against the sides of the container.

I've also seen dedicated sous vide magnets used for attaching items to the side of the bath that prevent the bags from floating. This will press the bag even closer to the sides of the bath.

I would assume that even worse case, conduction through the food itself would bring the item up to temperature. On that basis I generally leave food in at least 30-60 minutes over time to compensate for this when a bag is very close to the side or resting on the bottom.

Is it essential then that any food cooked sous vide is totally surrounded by water? If so, by how much? 1mm? 1cm? 10cm?

2 Answers 2

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Remember, if the food is touching the bottom, or other food, you are, essentially increasing the thickness of the item. That means the time to heat/cook will increase...and dramatically, it is not linear (thickness and heat transfer), it is logarithmic. So, it could take much longer...to the point of being unsafe. So, food should be completely submerged, and there should be enough space completely around the food for water to circulate. Using a trivet, as @borkymcfood suggests is great for keeping it off the bottom, but also pay attention to the space between. You simply should not over crowd...it is better to just get a larger container.

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  • That seems to preclude the use of sous vide magnets that attach pouches to the side then. My bath is quite large (10 litre) so I'll look into getting a suitable rack or trivet.
    – Greybeard
    Oct 1, 2022 at 12:49
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    @Greybeard I don't use them, but I could see attaching, say the two top or bottom corners., if that sort of allows the bag to swing from the side...as long as there is circulation, you will be ok. For me, if if have floating issues (especially with, say carrots), I use a trivet on bottom and a set of tongs or something like keeping the item submerged from the top.
    – moscafj
    Oct 1, 2022 at 13:30
  • If the magnets are strong enough you could just use one at the top and insert an additional magnet between the side and the pouch (using 3 in total), which would allow the bottom to move freely. Depending on the design of the magnet, that would also give you 10mm space at the top for circulation.
    – Greybeard
    Oct 1, 2022 at 16:28
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You're correct that the food will reach full temperature equilibrium at a slower rate through internal conduction; an added concern though would be heat loss through conduction to the container walls, especially if using a poorly insulated container like a metal pot. The extended time for equilibrium may also be a concern for pathogen growth and toxin production for thicker non-intact meats or potentially contaminated cores, such as roulades.

It's ideal to have foods fully surrounded by water to minimize internal temperature come-up times, especially if following <5-log lethality recipes - the minimum distance just needs to be enough to ensure there are no flow dead spots with lower temperatures, which you can quickly check with a probe thermometer.

For my setup I usually use the round stainless steel trivet/rack that came with my Instant Pot. Most cookware stores will stock similar items.

instant pot rack

Instant Pot trivet on Amazon.

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  • Excellent idea, @borkymcfood. I've got an Instant Pot and a trivet but I have just discovered that the polypropylene container (which is square at the top) narrows considerably towards the bottom. From memory, I doubt if it will fit such a small footprint. Serves me right for being a cheapskate and not buying a proper (very expensive) container.
    – Greybeard
    Oct 1, 2022 at 16:41
  • @Greybeard Places that sell round trivets may have them as small as 4-inch diameter. I have a set with varying sizes, and a very awkwardly tall and narrow aparagus/spaghetti pot I sometimes cook with too. Oct 2, 2022 at 3:56
  • @Greybeard an option for your container setup would be sealing a pocket of air at the top, and if needed, a weight like a small spoon at the bottom in separate sections. More length of bag used, though you'd have positioning by buoyancy without extra equipment. Oct 2, 2022 at 4:01

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