Once a week the kitchens at Campus Valla operate at full pressure. This is the day for cooking 30 litres of food for several thousand, rather picky, dinner guests. LiU Magazine proudly presents its culinary extra.
It’s a small kitchen, cooking for many dinner guests, and the cooking smells are not particularly appetising. Roger Carmesten is wielding the cooking whisk. He is the person who provides food for the fruit flies used in research at the university.
“Every Tuesday, the research groups that use fruit flies send in a list of the food they need, and specify the amounts. I cook the food on Wednesdays, and deliver it on Thursdays.”
Roger Carmesten pours agar, a thickening agent derived from algae purchased from the US, into an 80-litre catering saucepan.
“‘Normal’ cooks also use agar as a thickening agent, in sauces, for example. It doesn’t form lumps, as flour tends to.”
Sugar, yeast and cornmeal are weighed out and poured into the saucepan, while Roger Carmesten keeps whisking the mixture with an enormous balloon whisk. After the brown mixture has boiled sufficiently, he allows it to cool to approximately 80 degrees, and then adds preservative to prevent the growth of bacteria and mould.
The basic recipe is approximately the same for all, but some variants may be needed. It is possible, for example, to swap the sugar for molasses mixed with cornmeal, or to make a more freely flowing mixture.
“The fruit flies are picky, and they can’t eat food that has pesticide residue. This means that all ingredients must be organically grown”, says Roger Carmesten. “It can sometimes be a bit difficult to obtain the raw materials. It is also important that all the flies in an experiment receive the same food, to prevent the effects of diet being a source of error in the research.”
Irritating and invaluable
Photo credit Charlotte PerhammarDrosophila melanogaster is the Latin name for the flies used in research, more commonly known as the irritating fruit fly. These are the ones that suddenly appear at home, hundreds of them hovering over fruit bowls, the waste bin, or your glass of wine. It is, however, invaluable for research, being a model organism whose use in research dates back to the 1920s. Five research groups at Linköping University use these flies, conducting research in fields such as evolution, Alzheimer’s disease and epigenetics.
The flies are cultivated in laboratories at the Division of Biology and at the Department of Clinical and Experimental Medicine. There are also stock centres around the world where it is possible to purchase flies, if a particular strain is needed in the research.
Cooking the food takes an hour. Roger Carmesten uses dispensers to pour the food into test-tubes, with exactly the same amount in each.
“You have to be very careful, nothing can be allowed to end up of the rim, because this causes the flies to prefer to land there, apparently.”
The food is left to solidify in the tubes, which are covered with cheesecloth, the same that is used around some more expensive cheeses, to prevent unwanted insects getting at the food. The tubes are turned upside down, placed into bags, sealed with clamps labelled with the date, and delivered to the research groups, where the flies are placed into the test-tubes, not the other way round.
“Right then, now there’s just the chores to finish off”, says Roger Carmesten, and starts to wash up.
Translation: George Farrants