<p>I strongly suspect physics at play: Many (most) modern coffee packages contain a one-way valve, which is there to let excess gas escape that can develop when the coffee is packaged shortly after roasting (and which some shoppers mistake as a “sniff here” service when buying coffee at the supermarket - not wrong, but not the primary reason).</p>
<p>If such a package travels on a plane, the reduced environmental pressure and thus relative high pressure in the pack expels air from the pack, equalising the pressure level. (The same reason that can cause a shampoo bottle to pop open mid-flight.) Back on the ground, where pressure is normal high again, the coffee pack is now at low pressure, causing the pack to contract and feel firm, because while the valve allows air to get <em>out</em>, it doesn’t allow it back <em>in</em>. The coffee shouldn’t be affected from that at all. When you open the pack, you may hear a sound when air rushes in, and the beans or ground coffee should again be as loose as before.</p>

CC BY-SA 4.0
2024-12-29T11:10:48.323Z
2024-12-29T11:10:48.323Z
Stephie
<p>I bought two coffee pouches from supermarket to be given as a gift to someone. One pouch was Starbucks 160 gm pouch and other was another brand. Before taking flight, both were packed in checked luggage on top without placing anything over them. When I reached home after 10 hours flight and took out the luggage, the Starbucks pouch was as hard as a brick while the other one was normal. I would appreciate if someone could explain the reasons of one coffee pouch getting hard. Secondly, is there any method to  bring the hardened Starbucks coffee pouch back to normal as it was supposed to be given as gift?</p>

CC BY-SA 4.0
2024-12-28T22:48:13.110Z
Does the Starbucks pouch contain instant coffee, sweetened coffee, or just roasted whole bean or ground coffee?
R Mac
<starbucks>
Coffee pouch got hardened after air travel
Guest
# Coffee pouch got hardened after air travel

(Asked by: username_0 on 2024-12-28)

I bought two coffee pouches from supermarket to be given as a gift to someone. One pouch was Starbucks 160 gm pouch and other was another brand. Before taking flight, both were packed in checked luggage on top without placing anything over them. When I reached home after 10 hours flight and took out the luggage, the Starbucks pouch was as hard as a brick while the other one was normal. I would appreciate if someone could explain the reasons of one coffee pouch getting hard. Secondly, is there any method to bring the hardened Starbucks coffee pouch back to normal as it was supposed to be given as gift?

**Tags:** starbucks

> **Comments:**
> **username_1**: Does the Starbucks pouch contain instant coffee, sweetened coffee, or just roasted whole bean or ground coffee?  

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## 1 answers

### Answer by username_2 on 2024-12-29. Score: 2

I strongly suspect physics at play: Many (most) modern coffee packages contain a one-way valve, which is there to let excess gas escape that can develop when the coffee is packaged shortly after roasting (and which some shoppers mistake as a “sniff here” service when buying coffee at the supermarket - not wrong, but not the primary reason).

If such a package travels on a plane, the reduced environmental pressure and thus relative high pressure in the pack expels air from the pack, equalising the pressure level. (The same reason that can cause a shampoo bottle to pop open mid-flight.) Back on the ground, where pressure is normal high again, the coffee pack is now at low pressure, causing the pack to contract and feel firm, because while the valve allows air to get *out*, it doesn’t allow it back *in*. The coffee shouldn’t be affected from that at all. When you open the pack, you may hear a sound when air rushes in, and the beans or ground coffee should again be as loose as before.


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