Broccoli, cauliflower, Brussels sprouts, savoy cabbage or kohlrabi. Many children – and some adults – automatically grimace at such a list. The form-rich plant genus Brassica, better known as cabbage vegetables, always leads to arguments at the dining table. The Australian food chemist Damian Frank from the University of Sydney carried out a study on why children in particular are reluctant to eat vegetables.
SZ: Mr. Frank, do you dislike cabbage vegetables?
Damian Frank: No, I think it’s great. But it depends on how it is prepared. So if cauliflower or broccoli are just cooked, they can be very boring. But when they are briefly seared in a pan and have a nice sauce on them – have you ever done that? Then cabbage is pretty good.
Not all people see it that way.
If we believe the nutritionists, practically no one or only a very small percentage of the population eats enough vegetables – in Germany as well as in Australia. However, cabbage vegetables in particular have many advantages, as they protect against a whole range of diseases, including cancer. So it’s very good for us.
If only it tasted that good. Why do many people, and especially many children, not like cabbage?
There are bitter compounds of amino acids called glucosinolates in cabbage vegetables. There is much research around the world on the relationship between the amount of glucosinolates and the preference of children and adults for cabbage. In our study, however, we examined a completely different chemical substance that accumulates in Brassica plants for the first time: dimethyl trisulfide.
That sounds complicated.
We have found that bacteria, which are found in the mouth of many, but not all, of people, come into contact with the dimethyl trisulfide very quickly. They break down the substance in the mouth and produce smelly sulfur compounds in the process. If you have a lot of such bacteria, you will not enjoy cauliflower and Co.
And have you tried that on children?
We had 98 parent-child pairs participating in the study. Not all of them made it through to the end.
What exactly did you find out?
The bacteria in saliva are found in both children and adults. But for the adults, that didn’t particularly affect how they perceived the taste and smell of cauliflower.
Why is that?
Children carefully approach food. They like sweet things first, then salty ones too. They definitely don’t like bitterness at first. That’s probably an evolutionary adjustment because some bitter and smelly things are pretty toxic. As you get older and have more experience with food, that can be overcome.
So is it true after all when parents tell their children: you will get used to the taste?
Many children actually do that. Everyone remembers a time when their parents forced them to eat things they didn’t like. Types of cabbage are a classic. For me it was Brussels sprouts. I couldn’t stand fish either. But it is a new finding that bacteria in the mouth can contribute to the sense of taste.
Damian Frank, 54, is a food chemist at the Australian science agency CSIRO. As a child, he fought fights with his parents because they wanted him to taste Brussels sprouts or fish.
(Photo: private)
And can you find out whether you have these bacteria in your mouth?
You can easily copy one of our experiments yourself: put some broccoli in a glass, add some saliva – and do the same with some water from the tap. Let the whole thing stand for a few minutes. If you smell a huge difference, you probably have a high level of bacterial activity.
What does that mean for raising children?
It is helpful for parents to know that the aversion to bacteria can come in the mouth. And then you can only get ahead with patience. With a lot of repetition and good experiences, children may learn to endure the taste. As they get older, they might even like it.
Can the taste-spoiling bacteria be outwitted somehow?
Different cooking methods could minimize the effect of the bacteria: cook the vegetables long enough or pour the right sauce over them. Or put lemon juice on it, which could block the enzymes in the mouth.
What else do you know about the bacteria?
We know that this type of chemical reaction is likely to occur lower down in the gastrointestinal tract in any human being, it could be important for the absorption of nutrients. But we have absolutely no idea why some people have these bacteria in their mouths, or whether it’s a good thing or a bad thing. We are only just beginning to understand that.