The yogurt adventures

What’s up folks? It’s being a while since the last post. Too much if you ask me. So, let’s not loose time and dive right to it. Yogurt. That’s the topic for this post. That and random experiments (cool photos down below, just saying).

Do you remember that in the last post we talked a little about the basics of fermentation? Now it’s time to apply what we have learned. Time to put random jars filled with milk in your cooler.

How to make Yogurt

Making yogurt is so simple. All you need is bacteria and milk. Ta-da! Yeah, very clever but where do I get the bacteria? Because not every bacteria makes yogurt. There are at least three ways that I know.

One: buy yogurt with active microorganism at your store/supermarket. Any regular yogurt would do. But you should avoid the dairy products that aren’t explicitly labeled as yogurt.

Two: buy yogurt starter sacs. These contain freeze dried bacteria ready for use. You can find them at some local stores, and of course, around the web. Here for example.

Three: Colonize the milk with wild-around you bacteria. I have not tried this one, but for sure that it can be done. I mean, think about the first time that somebody made yogurt. I have not tried this one . I consider this one the more unstable, the one you have less control of, and also the one with the significantly higher failing rate. But I will.

Me, playing with food

Remember the saying “Don’t play with the food”? Well, I have failed, sorry. Again and again. And after playing a while I have found several things you may find interesting.

First fact. If you want yogurt, give it some love as heat.

Briefly. You need at least two bacterial species if you want to call “yogurt” your fermented product. Streptococcus thermophilus and Lactobacillus bulgaricus, a subspecies of Lactobacillus delbrueckii. The hint is hidden here in these word: thermophilus. This stands for temperature (thermo) and lover of, attracted by (philo).

So, what happens when you place a film-covered glass of milk with a spoon of yogurt as bacterial starter in your cooler? That’s what I did. And if you manage not to get intimidated by the sour stares of the person that lives with you after a week with that glass in your fridge, you end up with, well…nothing edible or pleasing to eat. But there was something that get my attention. A mossy and tinny red spot just above the milk surface. And, ‘cos I am a freak… And, because it happened that I was with a good friend that is at least as freak as me who loves biology… We decided to dust off my old optic microscope and take a look at the little red thing. And this is what we found.

Before complaining about the quality of the pictures, consider that they were taken with a mobile phone thought the lenses of a 25 years old optical microscope.

And while I didn’t see anything beyond the obvious presence of what definitely looks like mold (fungus), my friend remarked a good point. As you can see in the inner lighter circle at the second picture, it looks like the small filamentous structures called hyphae (singular hypha, from greek “web”) are cut at a cellular level, forming a chain of individual cells.

This fissures are called septa and denote that, what we have here is a septate fungus. Each block is a single cell with its cellular wall and nucleus. The walls are made mostly of chitin, a biopolymer. You can read about biopolymers and chitin in this previous entry.

Until today, I had have no problem with any other fungal contamination in none of the batches I have done under warm conditions (around 40ºC). Yogurts seem to came perfectly one after another just keeping a minimum of hygiene for the small jars. Dishwasher is key here.

PS: I had another fungal invasion in my regular batch line very lately. But after around 15 or 20 batching-rounds, I will call it a win. Blackish mold this time though.

Second fact. If kefir is done at room temperature, do it at room temperature.

If you are not familiar with kefir, this dairy product is very similar to the regular yogurt, but implies several different bacterial species in the equation, and yeast. Since yeasts used in this dense beverage (bread yeast Saccharomyces cerevisiae for example) carry out an alcoholic fermentation, you can find small quantities of this in kefir. Remember the fermentation basics and that there are different kinds of fermentation.

For a stronger flavor in your yogurt: try using goat milk, or even other kinds. The milk is the limit

But I’m sidestepping from the main point. I bought a sac of kefir ferments and followed the instructions detailed on the label of the sac. Briefly: mix with milk and let the thing 24h at room temperature. The result was good enough and really tasted like kefir, but not as strong flavored as I expected it to be. Maybe because of two factors. First, I usually take goat milk kefir, which is obviously more intense. And second, I don’t remember reading yeast as an ingredient in this mix, and this could very well be a very determining factor if true. I feel deceived.

Anyway, I thought that giving some warm to the next batch would maybe increase the fermentation rate and, therefore, the sourness and acidic features of the product.

Not at all. And now what I have is a very good yogurt tasting culture. Nothing like kefir. Nonetheless, I am very happy with the development of the experiment. And now I can leave my mind wondering about this result. And what I am guessing (and it fits a good explanation to me) is that, whit that increment in temperature, the bacteria present in the mix that are typical of yogurt products have outcompeted the kefir typical ones. Monopolizing after that all the resources and food, and effectively starving them.

That should explain why kefir is prepared under room temperatures, and yogurt cultures benefit from higher temperatures.

And that is all for the time being folks. I hope you enjoyed reading and maybe learned something. Keep trying new things in your kitchen and out of it and, as always, have fun. Cheers!



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