Rancidification – short and sweet

I’m going to make the topic of coffee going rancid short and sweet. If anyone wants a more in depth and even scientific version of this, let me know.

When coffee (or anything with oils) goes rancid, the coffee oils react with either water or oxygen. This is why when storing roasted coffee, you want it in a dry and dark container. Moisture in the air will provide the water that will make the coffee go rancid. Light and oxygen in the air (with the help of enzymes in the coffee beans themselves), will oxidize coffee oils, making it rancid.

So don’t store coffee in the refrigerator. Don’t store coffee in the freezer. The only time storing coffee in the freezer may be ok is if it is vacuum packed and you plan to store it for a period of time. Once you take the bag out of the freezer, let it come to room temperature. Keep it at room temperature. Use it within two weeks.

A tin kept on your kitchen counter or in your pantry is a good place for coffee. The more the roasted coffee is exposed to light, the more chance there is for it to go rancid.

Now let’s talk about the coffee I got from the coffee bins at Giant Eagle: 1) they were not vacuum packed, but were exposed to any moisture in the air, 2) they were not stored in the dark, but were exposed to the fluorescent lighting of the store almost 24 hours a day. No wonder the coffee tasted rancid!

But let’s be fair to Giant Eagle. This past weekend, I bought a bag of Starbucks coffee from them. The bag at least had “Feb” typed on it. So at the very worst it may have been three weeks old, which is better than three months old coffee. I made a cup for myself this morning. I did not get the upset feeling in my stomach. Conclusion: not all coffees sold at a supermarket are rancid. But sales to unload inventory may not be the best way to go – even though the price may be tempting. They may be three months old coffee.

Are all supermarket coffees rancid?

After drinking freshly roasted coffee for about a month, I tried two store-bought coffees: 1) Dunkin’ Donuts and 2) Marketplace Coffee from Giant Eagle.

The Dunkin’ Donuts coffee was on sale for about $5.50 for a 12 oz. bag. After making a mugful in my French press, I took it on the bus on my way to work. I found my stomach was upset. Since it was on sale, I chocked it up to old beans, hence the sale.

This past weekend I got the La Prima’s Coffee Roaster too late on Sunday afternoon to replenish my green bean supply. So I went to Giant Eagle to get some coffee, especially since my father-in-law was coming to work on my basement. I decided that for the price at approximately $6.50 a 1b. I filled up a bag with whole Sumatra beans. It looked dark roasted, with the oils shining on the surface of the beans. I made a pot with my Cuisinart Grind ‘n Brew. It wasn’t bad. The next morning I made a mugful with my French press with the same beans. I took that on the bus on my way to work. Just like the Dunkin Donuts, my stomach was upset.

Hmm. What’s up with these store-bought coffees? In the past I’ve always attributed the upset stomach to the caffeine content. But during the month I drank my fresh roasted coffee, I never had this problem. Actually, I really looked forward to my bus rides with my mug in hand. I found the best cup of coffee was made with beans half from Kenya and the other half from Brazil. The Brazilian beans give the coffee a very sweet taste that becomes more and more chocolaty and nutty as the cup cools. The Kenyan beans makes the cup bright in flavor – tantalizes the taste buds – when first sipping the brew. As the coffee worked its way down to the gut, there was a warm comfortable feeling, especially on cold mornings in the teens and twenties.

So what do I think? I think the upset stomach is from the oils in the roasted coffee beans going rancid. I’m a chemist working in a lab analyzing proteins being studied by biologists and medical doctors. Just by being exposed to air proteins readily oxidize and hydrolyze – both being chemical processes that take place when things decompose.

I’ve heard that the rule of thumb for roasted coffee beans is that they are good for two weeks. Anything longer than that – they are going bad. So how long do beans sit on the shelves or coffee bins at Giant Eagle? It’s hard to believe it would be less than two weeks.

Are all coffees sold at supermarkets rancid or at least starting to go rancid?