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Plastic food grade storage box

I have recently purchased a 10 litre semi-opaque (grey) plastic container which appears to be ideal for sous vide cooking. It was sold as food grade, freezer & microwave safe, and has all the relevant marks on the bottom to confirm this rating. It is manufactured from polypropylene and is (PP5) graded.

Looking online, all the other sous vide baths I see are manufactured out of much more expensive polycarbonate, and this container was a fraction of that cost. I assume here that polycarbonate has been chosen because it is more rigid than polypropylene.

I have tested this up to 85 Centigrade and the walls of the container flex and bow only slightly more than they do when cold. I doubt if I will sous vide beyond 75 Centigrade, am I taking a risk using this product here?

Greybeard
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Polypropylene is fine for use up to (or even past) boiling temperatures. I scald milk for yogurt by steaming it in used PP5 yogurt containers.

Indeed, this list rates PC as 10°C lower service (90-125°C) than PP (100-130°C), or basically equivalent for "high heat" PC at 100-140°C).

Ecnerwal
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If you intend on using it as a container for your bath water, then the concern is mainly for long-term durability compared to polycarbonate. Often part of the added cost for 'nicer' polycarbonate containers is NSF/other certifying body testing and validation for commercial use, including durablity and ease of cleaning - liability control in industry, more peace-of-mind for home cooks..
If the flexing is acceptable to you within the temperature ranges you cook at then there shouldn't be a problem for flexibility.

Polypropylene has a melting point above 100C/212F and can be used above this temperature[1,2]. Microwave heating is very uneven and it's typical to develop boiling or even superheated hot spots along edges and corners - you may see some small melted rough patches on old microwaved Ziploc etc. food containers. In contrast, normal sous vide temperatures are very evenly below boiling, let alone polypropylene melting temperature. The risk of plasticizer/additive leaching from container > water > bag membrane > food is even lower.

borkymcfood
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I would perform a test of the container to ensure it can handle the stress. Another consideration is purchasing 2 containers and nest them. You then have a backup wall for a leak plus you create an insulated zone to aid in heat retention.

Robert Fedoruk
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