Falmouth Academy science fair demonstrates the properties of salt, cheese and mayo with three experiments that help cooks.
Cooking is an art and a science. The art comes from imagining the meeting of different ingredients, but the science is all about how much of each will make a perfect match. Science is why we turn to cookbooks, because it's easier to depend on tested recipes than to whip up our own.
Ingredients are expensive and time is too precious for most people to conduct experiments in their kitchens.
Then there are those who love to play with food, like these three Falmouth Academy students who chose to conduct food experiments at their annual science fair last Thursday.
The fair is an annual schoolwide event for students in grades 7 through 11, and is optional for seniors. Julia Signell won a second-place prize in the upper school, Abby Hollander won an honorable mention in the upper school, and Cassidy Reves-Sohn won an honorable mention in the middle school. All three live in Falmouth.
All three discovered that even though experiments don't always turn out the way you expect them to, you can learn a lot along the way. And their work yielded conclusions that could go straight from lab to kitchen.
Here is a peek at their experiments and findings :
Researcher: Cassidy Reves-Sohn
Motivation: Cassidy chose to test and compare the bacteria counts in homemade potato salad versus store-bought because she is interested in food hygiene and wanted to know more about what she was eating.
Hypothesis: Cassidy thought the commercial potato salad would have more bacteria than the potato salad she made in the science lab at school because, she theorized, the materials used in mass production wouldn't be as sterile as those she had control over.
Experiment: In addition to home (lab) made potato salad and commercially made potato salad, Cassidy also tested the bacterial counts in plain potatoes and plain celery. First she washed and boiled the potatoes and then blended them with sterile water to make a dilution series to test. She also prepared a dilution series for the celery, the commercial potato salad and her lab-made potato salad.
Cassidy diluted the materials to a proportion of 1 to 100. She then took that solution and further diluted it to 1 to 1,000, so she could actually count the bacteria. She added some nutrient agar (a growth medium used to cultivate bacteria) to each sample in a Petri dish and after two days counted the bacterial colonies in each dish.
Results: The plain potatoes had the highest bacteria count with the celery coming in a close second. The lab made potato salad had a significantly lower bacteria count, but the winner was the store bought commercial potato salad. Cassidy did not make any adjustments for possible preservatives in the commercial potato salad.
Conclusion: "I always thought that potato salad would have a lot of bacteria because it has a lot of mayonnaise, but mayonnaise was actually good," Cassidy says. "Mayonnaise was actually the reason that the lab-made and the commercial had so much less bacteria than potato and celery, because it has preservative qualities."
Researcher: Abby Hollander
Motivation: Abby was inspired to do an experiment with brining chicken after reading Harold McGee's "Curious Cook" column in The New York Times.
"I read it and thought, wow, that would be something interesting to experiment with because it was right around Thanksgiving time and my brother was brining his turkey and we weren't," she says. She measured the weight changes of chicken when exposed to different salinities.
The Hypothesis: Abby thought chicken that was brined in the saltiest solution (10 cups) would gain the most weight.
The Experiment: Abby cut each chicken breast into four equal-size pieces and weighed each piece before submerging it in a solution: a gallon of water and no salt (the control), 1 cup of salt, 3 cups of salt, 5 cups of salt and 10 cups of salt. She weighed the chicken again at four-, eight-, 12- and 24-hour intervals. She then baked the chicken pieces at 350 degrees for 45 minutes and weighed them one final time after they cooled for a half-our.
The Results: "My results were not entirely conclusive due to some overlapping error bars, meaning the stuff that differs away from the actual average that I had calculated," she says. "However, the one cup salinity did show the most significant weight gain at a very constant rate, which was surprising. It did not go along with my hypothesis."
Conclusion: More is not better when it comes to salt in brining. Brining works through osmosis, but the saturation level in the chicken levels out early, so brining for hours on end doesn't change the finished product.
Researcher: Julia Signell
Motivation: Julia wanted to test whether changing the amount of rennet (the enzyme that separates milk into curds and whey) and lipase powder (a flavor additive) would affect the firmness of mozzarella cheese. "I like doing experiments with food because you can eat them, and my dad makes cheese so I thought I'd try it out," she says.
Hypothesis: As the amount of rennet was increased, the firmness of the cheese would increase, and as the amount of lipase powder was increased, the firmness of the cheese would decrease.
Experiment: Julia made five variations of cheese. In the first, she used 1/4 teaspoon of rennet and no lipase powder. In the second, she added 1/4 teaspoon rennet and 1/4 teaspoon lipase powder. Other amounts tested include 1/8 teaspoon of rennet and no lipase, 1/8 teaspoon of rennet and 1/8 teaspoon of lipase powder and, finally, 1/8 teaspoon of rennet and 1/4 teaspoon lipase powder.
Results: "I found that with the rennet there was a correlation. The cheeses that were made with a fourth of a teaspoon of rennet were considerably firmer than the other cheeses," she says. "But with the lipase powder I didn't really find any statistically significant difference. It was kind of disappointing, but also interesting, because the recipe that I used said that the lipase would make the cheese softer, but I didn't see that at all."
Conclusion: "The lipase powder is used for flavoring, so the recipe suggested that if you wanted to put lipase powder in (it was optional), you should increase the amount of rennet to make it firmer so it would have a normal consistency, but I didn't find that it changed the consistency, so you wouldn't need to change the amount of rennet," Julia says.