We planned for at least 300 people to taste and rate a series of bitter concentrations, as well as stevia and aronia. The experiences of the tasters were recorded in a questionnaire. It was especially important to take natural saliva (or DNA) tests from the participants.

At first glance, it did not seem so difficult. However, some problems were not initially discernable. We needed to make solutions and products for the tests and create a questionnaire of our own. Additionally, we needed a suitable site to administer the tests. It was particularly important to find a way to respect the anonymity of the participants in our study.

While on the search for a suitable site, we came upon the House of Nature Museum in Salzburg. The number of people interested in science there would make it possible for us to inform them in detail about our project, and they could eventually be convinced to give a DNA sample. Yes, the House of Nature seemed ideal for our project!

We knew from the beginning that human DNA is something that has to be dealt with carefully, particularly when applied to strangers. So, we pondered how we could best keep our data anonymous. We finally came upon the concept of using a four-digit code. We generated the codes from the random number function of Microsoft Excel.

We knew that we would have to be well-prepared for our project. To be prepared for all contingencies, we decided to have a test run at the school. At the "big event" we wanted to be in top form

Our laboratory team had meanwhile set up a row of PROP water mixes, in which the bitter substance was in increasingly stronger doses (see Tab. 1). We wanted to differentiate between the super and non-tasters, concerning PROP. It was exciting to find out at the end that each person demonstrated a different taste perception. Some members of the team puckered their faces at the lowest dosage, while others drank the highest dosage as if it was normal water. Both at the test run at the school and also at the House of Nature, the tasters were often astonished. Naturally, this was very interesting to us.

In our school test run, we wanted to find out how our products would be received by another audience. We created products that were sweetened with stevia, for example, puddings, cakes and cookies. (As a side note, my personal favorite was natural yogurt with raspberries and stevia). In addition to the food, we found it naturally necessary to experiment with corresponding stevia-sweetened drinks. In fact, we had already sweetened various teas with stevia, and even invented our own deep-red aronia juice.

In addition, we worked on an (anonymous) questionnaire, in which we recorded data on taste perception, as well as age, sex, smoker or nonsmoker and favorite vegetables. This is also where we applied our four-digit anonymous code. Each test person received a code that was attached to the DNA test and the questionnaire. The same number was also given to the participants on a card with the address of the school's homepage, which allowed them to look at their personal results after the evaluation was complete. It was gratifying to receive so much feedback. Already during the test phase, we recognized the differences between non-tasters and supertasters when tasting stevia.

During the test run at the school, we determined that the questionnaire was not quite perfect. The biggest problem was the definition of the term "bitter", which some people confused with sour. How can the meaning of the word "bitter" be explained to someone? We decided to give the participants more terms, for example, "medicinal" or the well-known phrase "fresh from the dentist". Sometimes, the tasters found their own words that described the taste best for them, for example, "it tastes like Parkemed" (a painkiller). From this test run, we became aware of many mistakes in the questionnaire that would have produced inaccurate results.

After our test run, we felt well-equipped for the House of Nature. The day before the opening of an exhibition, "Mortal Danger? The (In)exhaustable Diversity of Nature", in which we would introduce our project for one week, we continued to work many hours to find the optimal mix of aronia concentrate and water. We experimented with a mix of aronia concentrate in mineral water and also tried to sweeten this rather bitter drink. We tried all possible combinations of stevia, sugar and molasses.

The big day was November 30, 2010, a Tuesday. In the evening, we listened with excitement and also a bit of nervousness to the opening speech, after which we had overcome a few small complications. We had packed up everything at the school and loaded it into the car. Fully packed in front of the House of Nature, we realized that we had left the yogurt at the school. We could not let such trifles stop us. While part of our team set up the stand, others rushed to the nearest supermarket to replace the missing yogurt. Just at the right time, we could sweeten and portion it and the opening could begin.

The whole team dressed up, some filmed interviews, others spoke with people about our project, and the rest helped visitors fill out the questionnaires. The PROP test series gave us some good photos, because many people made funny grimaces during the resulting "taste explosion". In addition, we collected the DNA samples and answered all questions with a smile. On opening day there was a great rush and we were happy about each visitor that participated in our test. Some were quite skeptical at the beginning; others did not want to give out their DNA. Only a few could not be convinced during the course of a discussion, in which we explained that our system was entirely anonymous and we would appreciate their support. For some, their excitement was written all over their face, while others walked around our display uninterested. Luckily, the former was the majority, which was especially motivating for us.

As we took down our stand on the opening evening, cleaned up our products and finally drove home, we were all confident about the coming days at the House of Nature.
On this evening, we collected 36 DNA samples and as many completed questionnaires. From Wednesday to Sunday, in the mornings and afternoons, our team members rotated shifts at our stand in the House of Nature. On some days, we could hardly stop explaining our project to visitors; on other days, we sat for hours at our presentation and wondered when the next visitor would stop by. Visitors from Hungary, Finland, England, the Czech Republic and Italy came by to check out our presentation and hear about our project. This was a great opportunity for us to collect samples from other countries (and also a chance to better our English language skills). We had a special encounter with an Indian visitor, who had a thick accent when speaking both English and German. Finally with hands, feet and humor on both sides, we were able to explain our topic to her. Throughout the day, we never tired of answering questions and we were rewarded handsomely for our endurance.

On Sunday evening, we determined that we had collected 419 DNA saliva samples that were frozen in cold storage at the school. We were all happy that we also had the corresponding fully completed questionnaires. We overcame all of our small complications and exceeded by far our goal of collecting 300 tests.

"That's awful", "Do you want to poison me?", "I don't taste anything", "The cake is delicious", "This yogurt is awesome", "It's absolutely sickening", ...

Nr. 1
Nr. 2
Nr. 3
Nr. 4
Nr. 5
Nr. 6
Tab 1. Used concentrations of PROP (propylthiouracil; 6-propyl-2-thioxo-2,3- dihydropyrimidin-4-on; 170,23 g mol-1)