Why should you chill lunchboxes to freeze them?

In yet another test carried out in the very high technology laboratory – in other words, my house – we arrived at a somewhat expected result. Yes, once again, we identify that water is the enemy of the perfection of our lunch boxes. But what was the test this time, Rui?!

One thing that is basic to food safety in food production and gastronomy as a whole is the correct storage of ready-made preparations. In the literature, there is a “risk zone” between 4ºC and 57ºC, where the proliferation of bacteria is most active. The recommendation is that the temperature of your food remains (and drops) between 57ºC and 21ºC in less than 2 hours, and from 21ºC to 4ºC in up to 4 hours. In other words, you need the post-preparation temperature to reach less than 4ºC within a maximum of 4 hours (this also counts if you eventually heat and cool your food again – the famous “restôdontê”).

This cooling is essential so that bacteria do not reproduce and cause food poisoning in us humans. However, it should not be taken literally when we talk about cooling for storage in lunchboxes. Don’t worry, I’m not saying you should disregard these rules. I explain!!

In the test carried out, the objective was to show the impact of steam condensation from still hot food when covered by the lid of the lunchbox. You may have already noticed that, with any food that is still hot, when you cover it, water droplets form on the lid, right? (If not, try covering the still hot rice cooker with a glass lid and wait a few minutes.). In the A/B test, we put the same amount of rice in two lunch boxes and, in the first, we closed the lid, while in the second we waited 10 minutes before closing.

Here comes the food safety point: these 10 minutes are not unsafe when it comes to bacteria! Consider them the same amount of time your food sits on the table during a meal! I say this to avoid any confusion in the test and the possibility of unwanted illnesses and illnesses, ok?

Well, having said all that, let’s get to the test?

Test: amount of steam (water) covering the hot or cold lunchbox

Using two lunch boxes of exactly the same weight, I put the same amount of freshly cooked rice in both. In the lunchbox (1), we cover it straight away. Once in the lunchbox (2), we wait 10 minutes and then cover it. It is noticeable after 10 minutes that the lunch box (1) already had a large amount of water condensed on its lid, resulting from the steam from the still hot food. The results found were:

Conclusion: In just 10 minutes, 2% of the original weight of the prepared food was eliminated in vapor form.

1. Hot closed
   1. Starting weight: 150g
   1. Final weight: 150g
   1. Equal weight from start to finish, due to the “trapping” of vapor and its subsequent condensation
2. Closed “Cold” (10min later)
   1. Starting weight: 150g
   1. Final weight: 147g
   1. Reduction of 2% of its total weight (loss of water in the form of vapor)

These 10 minutes, again, do not represent a risk for bacterial contamination in food, and have a great advantage in preventing water retention in lunch boxes. These 2% (3g) of water condensed on the lid, when frozen and thawed, precipitate and fall back onto the food, making it more humid. The number obtained – 2% – may seem small, but it is worth remembering that the test was carried out with rice, a cereal. If we think about vegetables, especially, the rate of water evaporation is much higher, as they naturally contain a greater amount of water.

In other words, the next time you prepare your practical meals for the week, use this tip – in addition to last week’s (click to learn about vegetable preparations) – to get a tastier and fresher lunch when it defrosts!!

I hope I helped, and see you in the next text!

Link to this practical video: Rui Morschel (@ruimorschel) • Photos and videos from Instagram