I spend the majority of my waking hours either consumed by science or consuming food. I used to be able to do both at the same time, but the National Institute of Health says that’s not safe anymore. To be wholly accurate, I also devote about 1.3% of my time to general housekeeping tasks like Personal Hygiene and Maintenance of Healthy Interpersonal Relationships. In a special twist of events, for one post only, the pie chart distribution of things in my life become one, and I get to eat the whole thing… Today, we’re talking about the microbiology of food!
This post was initially inspired by the Spilled Milk Podcast. In one episode, hosts Molly and Matthew perform an exhaustive analysis of commercially available yogurt. Listening in on their taste testing adventure involved lots of “yogurt mouth noises” and hilarious dairy horror stories. It made me think… Yogurt is a pretty simple food, so what makes one yogurt brand more delicious than another? Because I am a microbiologist, and I was physically in the lab doing microbiology while listening to the podcast, I wondered if I could take a closer—and by closer I mean precisely 1000 times closer—look at these dairy treats to see if there was any science behind why some brands are tastier than others.
Ultimately, the results were inconclusive…but, for lack of a more scientific term: freaking awesome. While I still can’t say why I prefer Straus yogurt over Nancy’s brand, my yogurt study spawned an examination of a cornucopia of foods and the microscopic critters we often take for granted. Prepare yourselves to take a peek at a part of the cooking process that few get to see. This is…the INVISIBLE KITCHEN!!
Figure 1. Nancy vs. Straus
Here’s a is a primer on what bacteria look like under the microscope. This is a zoomed in view of a micrograph I took of European Style Plain Straus yogurt. I pointed out the two different morphologies of bacteria present in yogurt: cocci, and rods or bacilli. The hazy, splotchy bits around the bacteria is the yogurty milieu (that’s not an official science term, but I think it sounds cool).
Panel b is a snapshot of Nancy’s yogurt, and Panel c is Straus, more zoomed out than in a. I noted more rod shaped bacteria on the Nancy slide. Could this make scientific sense?! On the back of the Nancy’s carton they list 5 different rod-shaped bacteria in their starter culture (4 Lactobacillus species and Bifidobacterium), while Straus has only 2 Lactobacillus species as well as Bifidobacterium. Another thing to note are those clear shapes within the Straus yogurty milieu (Panel c) but not in Nancy’s. I think these are salt crystals. Salt enhances flavor, so perhaps that’s another factor that explains why I like Straus better than Nancy’s. Obviously, more experimentation is necessary. If you know anyone who wants to give me a research grant, forward them a link to this blog!
Figure 2. Kraut Faceoff
Remember that time we made sauerkraut a few weeks ago? I thought it would be fun to compare our kraut to some that I bought at the grocery store. This brand is the hippiest pickle product I have ever seen. It claimed to be RAW, NATURAL, SUPER PROBIOTIC, ORGANIC! I always wonder about foods touted as probiotic. How do the microbes handle being commercially packaged, transported and displayed on shelves? I examined the probiotic potential of these krauts by attempting to grow the bacteria in petri dishes with media (aka bacteria food) and by looking at the kraut brine under the microscope. Figure 2 a and b show the bacteria that grew after about 4 days at room temperature (each of those little white dots is a colony of bacteria). Figure 2 c and d show micrographs of the bacteria present in the kraut brine. You probably don’t need a degree in microbiology to note whose kraut bacteria were happier. (But…just to drive the point home: OURS GREW LIKE GANGBUSTERS! And theirs…well, theirs didn’t.)
While I can’t make claims about the rawness, naturalness or organicness of this commercially available kraut, I can say this: KRAUT SMACKDOWN! WE WIN. Our kraut completely decimates the competition in the probiotic category. I can also scientifically say that ours tastes 265.7% better than theirs. In conclusion, if you’re interested in reaping the probiotic benefits of sauerkraut, or just eating sauerkraut that tastes good, I suggest you make your own!
Figure 3. The Battle of the Bread
And now, the part of this post about which I am most excited. This section was created with the help of Sue, one of my colleagues in the lab. She is responsible for the really stunning micrographs below and for turning me on to the Tartine Method for baking wild yeast sourdough bread at home.
Tartine is a bakery in San Francisco, known for having the best sourdough bread on the planet (I am pretty sure that’s an accurate/scientifically proven statement). I once waited in line at Tartine for 2 hours just to get a croissant and a loaf of walnut bread. I had every intention to save the croissant until the next morning, but I might have accidentally sampled the tiniest pointy croissant corner on my way out… 5 minutes later I woke up crouched in an alley half a block from the bakery, completely covered in croissant flakes. All I remember is that it was the most transcendent pastry I have ever consumed. AND! It’s all thanks to their sourdough starter. Few people are aware of the differences between regular yeasted breads and sourdough. Allow me to show you!
Figure 3 a shows yeast from a store-bought packet. Those blue ovals are yeast cells, stained with a compound that makes DNA glow blue. Figure 3 b shows Sue’s Tartine-method starter culture. It’s basically all bacteria! While regular bread relies solely on yeast to give the rise and impart the yeasted flavor we expect, the rising and quintessential flavor of sourdough bread is due to the fermentation byproducts of bacteria. In fact, yeast make up only about 1-5% of sourdough starters.
So, next time y’all are enjoying a breakfast of yogurt and granola, some kraut on your weenie, or hogging an entire loaf of sourdough bread to yourself, take a moment and thank the microbes!