tl;dr I used a miniscule amount of starter and made perfectly fine yogurt.

It's often repeated on this sub: do not use too much starter! It will ruin your batch! Cause graininess, curdle your milk, and deliver onto you a lifetime of woe and sorrow. We know by now to err on the side of caution, and that less is more. But how much less? To answer this question, I started a new batch with [just a tiny drop of yogurt](https://i.imgur.com/McnhH7d.jpeg) from my previous batch. Half a gallon of Costco 2% milk, brought to a boil and left to simmer for 5 minutes, then poured into the metal bowl and left to cool to room temperature. Tiny starter stirred in, covered in plastic foil, and fermented in my Instant Pot Pro on the sous vide setting at 110°F for 12 hours.

When I checked on it at the 9 hour mark, [it seemed to have finished setting](https://i.imgur.com/DcdEioU.jpeg). I still let it proceed for the full 12 hours, and left to cool to room temp overnight before refrigerating.

The video shows the final product and consistency after refrigeration and pouring off the excess whey. It passes the Spoon Test™ and tastes identical to my previous batches. This fit my hypothesis, since yogurt bacteria has to proliferate exponentially and on a massive scale for making yogurt, the amount of starting bacteria should not make any difference as long as they are given enough time to multiply at ideal temp.

[Refer to these graphs.](https://www.researchgate.net/figure/Growth-of-a-L-bulgaricus-b-S-thermophilus-and-c-the-mixed-culture-during-lactic_fig1_255755181) Essentially, starting with less starter is just extending the graph leftward, adding some time to the total fermentation to reach the same numbers.

Conclusion: do not worry about using too little starter. As long as it is viable, and the milk is sterile (enough), the quantity is not an issue. If you are using packets of freeze-dried starter, you can probably use a tiny fraction of what the directions say without any problems.

You need far less starter than you think: a brief experiment