The best part of the annual AAAS meeting (which I am attending in Boston for the first time) is also the worst part of the meeting– there are SO many awesome, fascinating sessions to pick from, but you can’t attend them all, you have to pick. Selecting this session, however, was easy– I knew I would love “Fixing the Broken Tomato: What We Like and Why We Like It.” The session was led by researchers from the Institute for Plant Innovation at the University of Florida who are studying what makes a tomato delicious. Harry Klee started off explaining the fundamentals of flavor.
Why does he study flavor? Klee believes that if we make healthy food tast better, people will eat more healthy food. Instead, commercial growers have bred for higher yield and perfect appearance and in the process, our tomatoes have lost nutritional quality and taste, which fortunately for us eaters, are correlated. But it is much harder to select for flavor when breeding plants- flavor is complicated. To make matters worse, in general, growers are not paid for tasty tomatoes, they are paid for lots of sturdy tomatoes. Klee says that “the post-harvest system is set up to ruin flavor.”
The food distribution system often requires harvesting tomatoes before they are really ripe. Then they have to be sturdy enough to survive transport. Then, they are refrigerated in stores while they wait for you to eat them. But Klee says that putting tomatoes in the refrigerator ruins the taste of tomatoes. It’s a phenomenon I’ve known about and sought to avoid for years, but now I’m happy to now know WHY refrigeration ruins tomatoes. According to Klee, refrigeration destroys the important volatile compounds. We inhale the volatile compounds, creating our sense of smell and taste. These chemicals give flavors their complexity- and a tomato without them is disappointing.
To solve the flavor riddle, Klee and his colleagues started with the basic tomato chemistry: sugars, acids, and volatiles chemicals, of which the tomato has more than 400. To figure out which of these 400 play the key roles in tomato tastiness they employed an army of tomato tasters. I wish I could have participated in that project! So step 1, find the chemicals that contribute to tastiness. Then, find the genes responsible, and lastly, figure out how to mark those genes for knockouts and other experiments. They study the genome of delicious heritage tomatoes and then try to figure out how to breed some of the tastiness back into the hardy, modern varieties.
They discovered that what we like, in tomatoes and many other foods, is primarily based on perceived sweetness. This makes sense to me, I’ve always considered perfect summer cherry tomatoes to be like candy! But the tomatoes sweetness is not just from sugars. The volatile compounds play a role in how sweet we perceive the tomato to be. The pigment compounds, the caroteniods, break down into volatiles that are strongly correlated to consumers’s favor, because they enhance perceived flavor. Perhaps why orange grocery store tomatoes taste like cardboard?
Linda Bartoshuk, a taste researcher at the University of Florida found that out of 61 dominant tomato volatiles they studied, six enhance sweetness and two suppress sweetness. After lots of these studies, plotting the preferences of their tomato tasters, they have statisical models of what flavors we like. They know the recipe for the perfect tomato, they have a statistical model. The closer real tomatoes are to their model, the more they are liked, on average, by the tasters.
Using this understanding of the key flavors leds to improved breeding decisions. Hybrids between great tasting heirlooms and modern commercial lines are making progress. Klee is optimistic that grocery store tomatoes will taste better soon, especially if consumers demand better taste.
To demonstrate how crucial volatile compounds are to flavor, Bartoshuk runs the room full of scientists through an experiment: holding your nose and taste a gummy candy. You only taste the sweet. Then, with some gummy still on your tongue- open your nose and the flavor rushes in. More surprising, the perceived sweetness increases as well. The sugar, sensed by our tongues, remained constant, but the volatiles, sensed in our nasal passageway when air flow resumed, provided the extra sense of sweet. Just like in the tastiest tomatoes. The diagram of how sweet tomatoes seemed and how much participants liked tomatoes are strikingly similar.
The next speakers asked a bigger question – how could tastier tomatoes benefit society? Guidelines suggest that adults should get 2 to 3 cups of vegetables a day, but only 13% of adults and 6% of children meet daily recommendations. In 2010, the Healthy Hunger Free Kids Act increased vegetable requirements for school lunches. But just because you give kids vegetables doesn’t mean they will eat them. How do you convince kids that vegetables taste good?
Valerie Duffy studies how preschoolers perceive vegetables. Children with taste and smell sensitivity present a special challenge – supertasters with higher density of tastebuds find vegetables too bitter, not sweet enough, and the flavors too strong. Dislike of one vegetable can lead to generalized dislike of the category “vegetables.” Middle ear infections can also change how children experience flavors- pushing them further from vegetables. Experiments with sweetening vegetables increase children’s intake. Long term, the idea is that sugar can be used for exposure or conditioning, and eventually the children learn to like that vegetable, without the extra sweetness. Improving vegetable consumption is complicated, including nutrition education, increasing access to vegetables and accommodating for taste and preference.
The basic biological preferences that we are born with mean that children love sugar and avoid bitter. I’ve written about this inherent sugar preference before, but these researchers brought data. Julie Mennella showed a video of a baby’s first tast of a green vegetable, and the resulting unhappy face illustrates the challenges of convincing children that vegetables taste good. Exposing babies to a variety of vegetables, they become more accepting of new vegetables, the same with fruit. Mennella points out that early-life programming is key to future food choices.
I’ve often thought, when friends tell me that they don’t like tomatoes, that the problem is really that they’ve never had a delicious tomato, just off the vine from my mother’s garden or the farmer’s market in August. Grocery store tomatoes, in February, stiff orange slices decorating a salad, are not appealing. I hope the Klee’s research can succeed in figure out how to bring tastiness back to mass produced tomatoes, for society’s sake, but for me, I’m happy to wait until the late summer bonanza of perfect garden tomatoes, when I eat several a day and pack the freezer with a winter supply of tomato sauce. But I never put them in the refrigerator!