tl;dr - "The new findings suggest used coffee or tea could be a natural and sustainable way to improve the shelf life of baked goods, while at the same time infusing the products with added nutrients."
Pretty sure the caffeine extraction from most brewing processes is pretty complete, wouldn't doubt for a second that chocolate has significantly more than used coffee grounds.
Pretty interesting article, but would’ve been pretty funny if the results were “it just tastes bad”. Negative or failed results can be both funny and informative
Yes, did you also notice how the word "taste" doesn't appear in the article? It's all about recycling and nutritional value... which is even more wasteful and pointless if it won't be eaten.
Coffee and tea both have a history of being used in desserts solely for their flavor, and using the tea leaves or coffee grounds once for tea/coffee probably doesn't remove so much flavor from it that it renders it inedible. If you drink coffee or tea it's an easy enough experiment to perform yourself at home the next time you bake something. Even if the end result is "adds no flavor enhancement at all" it might still be worth doing just for the added shelf life, the same way that preparing bread with the tangzhong technique (pre-cooking some of the flour with water on the stove before incorporating it into the rest of the dough) doesn't alter the flavor but enhances the texture and shelf life of the bread.
In the actual study (linked to in the article) they mentioned testing this out with the coffee or tea powder substituting 1, 2 or 3% of the flour in the recipe. Also note that the used coffee grounds and tea leaves were repeatedly rinsed with distilled water, then dried and made into a powder. So, different than just used grounds or leaves that you would have handy.
Still, this might inspire me to find some existing recipes that call for coffee grounds and tea leaves.
I've made tea cakes before and generally enjoy them. I wonder how much flavor you get from used tea bags... I might try throwing some into the next bread I bake.
We just got some loose leaf tea as a gift, I might save some after steeping and see how it tastes in a quick bread. I bet it would be good in banana bread.