in 2007, mattes co-authored a study which found that people who consumed caloric beverages did not compensate for the calories in them as much as people who consumed solid food. in 2015, he published a study reporting that the taste of fat deserved to be considered another basic taste, alongside sweet, sour, salty, bitter and umami. mattes and his co-authors coined the term "oleogustus" to describe this taste. as of 2013, mattes was also working on researching the health effects of nuts, with the aim of determining whether they can remain appealing as a substitute for other snacks.