Last Updated: May 13, 2021

Sous vide is the cooking procedure we’ve all grown to love thanks to the juicy, tender, and flavorful results we consistently get from the method regardless of how many times we go about it.

But just as with other cooking method out there, sous vide isn’t without its own grey areas too, and the main problem here is the plastic containers used for wrapping up the food item prior to submerging inside a pot of boiling water, just as you might have correctly guessed.

According to reliable health authorities, some plastic containers are fond of leaching hormone disrupting chemicals into food, which when ingested, are capable of interfering with the body’s hormone functioning and subsequently posing a serious threat to people.

These plastic containers include polyethylene terephthalate, polycarbonate, and polyvinyl chloride to mention but a few, and the culprit chemicals they leach are BPA’s and phthalates.

With that being said, not all plastic containers are created equally, as many health authorities and plastic manufacturers are sharp to point out in defense of their stance for plastics “as not necessarily bad components” of our daily household episodes, and also the safety of their products, respectively.

According to them, some plastic containers are simply terrible at preventing chemical migration into food during high heat cooking, all thanks to their poor quality, ingredient composition, or both, while others are extremely good at doing so.

The critical factors here, which dictate the plastics that leach and those that don’t are the brand quality and the ingredients used in the manufacturing process.

Ziploc, being one of many plastic bag manufactures out there have also claimed on their website that their products are made out of polyethylene plastic without any additives added to improve their integrity. This would naturally imply that their bags are perfectly safe for sous vide cooking.

For the definitive answer:

Ziploc bags, if manufactured as advertised, should be safe for sous vide cooking since the bags wouldn’t leach any endocrine disrupting chemical due to the stability of the polyethylene components of the bag and also the lack of additives present in them.

The impressive stability of Ziploc bags is expected to be the result of a diligent manufacturing process that employs the use of polyethylene polymer which is normally tagged as a safe ingredient for plastic manufacturing, and also the abandoning of additives like fillers and plasticizers during manufacturing which are known to leach hormone disrupting chemicals into food during cooking.

In my humble opinion: Ziploc bags are still only safe on paper

With everything been said about Ziploc bags and their stability, they still should only be referenced to as “safe on paper” since no tom, dick or harry knows for sure what ingredients are incorporated (and may be hidden) during the  manufacturing process. We can only have faith with the claims of the manufacturer and hope that everything is just as stated.

One sentence that might perhaps ignite light of hope for you right now is this:

Polyethylene is less likely to contain fillers, plasticizers and additives than any other type of plastic out there because of its more superior nature – [1]. So, maybe, just maybe, Ziploc is actually telling us the truth!

The limit for Ziploc bag

When it comes to sous videing, I always recommend sticking with the Ziploc Brand freezer Bags with easy open tabs, and to use a second for double wrapping when cooking for long and at temperatures higher than 158 F, because the heat from the water can cause the bag to open at the seam which will expose the food to the water. Make sure to avoid the special bags and the sandwich bags like the plague.

How to seal a Ziploc bag for sous vide

Sous videing is using done at air tight conditions and the manual pressing out of air using hands usually isn’t an efficient process.

With Ziploc bags, things are much easier. First, press out as much air as you can from the bag, then seal with a little room at the top. Next, gently lower the bag into a pot of water (cold) until exactly the point of seal, then immediately seal shut and you voila, you have a vacuum sealed Ziploc.

Buts what’s actually happening? It’s a simply process, the pressure of the water forces the lingering air outside of the bag by pushing on the bag on both sides.

Frequently Asked Questions

Are Ziploc bags BPA free?

According to the manufacture, Ziploc bags are BPA free since they employ polyethylene for the manufacturing process without any additives. One primary plastic culprit that releases BPA during heat application is polycarbonate which is made from it. The heat breaks down the plastic during the prolonged cooking time of sous videing which then allows leaching to occur.

Sous Vide plastic Alternatives

Silicone bags

Silicone bags aren’t the best replacement for plastic bags when it comes to results, but put your health into the equation and you definitely wouldn’t be thinking twice when you have them around. They’re easy to use, reusable, easy to wash although they are much stiffer than plastics.

Mason jars

This wouldn’t work for all recipes, but they represent a decent replacement for plastic bags in areas where both can be exchanged without any sacrifice in the final quality of food. These are usually liquid foods of those that are submerged in liquids and then cooked.

Final Verdict

As stated above, Ziploc bags should be safe to use for sous vide cooking but only when the claims of using polyethylene materials and having end products free from harmful additives by the manufacture are true.

That’s because polyethylene polymer doesn’t leach harmful chemicals into food during low cooking such as the one experience with sous videing, and the lack of additives means that the product is even safer from such leaching.

One reliable publication made mention that polyethylene is less likely to have additives that other plastics during manufacturer. If you didn’t get that, it means that polyethylene is much more superior in quality which means that it can actually be manufactured without additives that would improve some basic qualities.

Still, deep down, within me, i feel something is not yet clear, and that’s the question: Are Ziploc bags really safe for cooking?

Reference:

1. John N. Hahladakis, Costas A. Velis, Roland Weber, Eleni Iacovidou, Phil Purnell.  An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling.  Journal of Hazardous Materials. 2018; volume 344; pages 179-199.  License.