Yogurt - a question.

[bernardsmith]

Is there a good reason why I should not use a small sample of my last batch as the culture to make a fresh batch? I understand that over time the culture will mutate in ways I have no control and so perhaps produce flavors and aromas that I will not prefer... but how then does that not happen with commercial yogurt makers? What enables them to control the mutations of their master culture?

 

[passedpawn]

Is there a good reason why I should not use a small sample of my last batch as the culture to make a fresh batch? I understand that over time the culture will mutate in ways I have no control and so perhaps produce flavors and aromas that I will not prefer... but how then does that not happen with commercial yogurt makers? What enables them to control the mutations of their master culture?

At the commercial level, I assume they either have their own labs to ensure consistent cultures, or they buy them.

I'd use a couple of spoonfuls of the last one to make the new one. I did that when I was on a greek yogurt kick a few years ago. I don't recall any change in the flavor, but there was only a few generations.
If you do this for a while and arrive at a result (good/bad), make sure to post here again so we have the benefit of your science.

 

[bernardsmith]

Will do. Thanks. My lab assistant is my wife. She does most if not all the tasting of the yogurt. I make it for her. Me? I prefer my cheese hard. I make my hob-nailed. (well, at least, cheddared )

 

[DBhomebrew]

A teaspoon of the last batch is exactly how I inoculated the new when I used to make yogurt. It's also how I inoculate lacto-fermented hot sauce. Sauerkraut. Sourdough starter. Really, it's the classic way to make home-made fermented stuff.

 

[passedpawn]

Will do. Thanks. My lab assistant is my wife. She does most if not all the tasting of the yogurt. I make it for her. Me? I prefer my cheese hard. I make my hob-nailed. (well, at least, cheddared )

Haha, same here. Wife was the consumer. I don't think she eats it much anymore though. I was adding various fruit to mine (pureed strawberries mostly).

 

[Lampy]

I used to regularly make Greek yogurt and got away with making several consecutive batches before starting again with a "fresh" culture.

 

[thefigure5]

Is there a good reason why I should not use a small sample of my last batch as the culture to make a fresh batch? I understand that over time the culture will mutate in ways I have no control and so perhaps produce flavors and aromas that I will not prefer... but how then does that not happen with commercial yogurt makers? What enables them to control the mutations of their master culture?

Some yogurt cultures can be used indefinitely, others cannot, at least not with consistent results. This is according to Cultures for Health, which is mentioned in this NPR article.

An heirloom yogurt can be used as the starter for the next batch, and this can be continued indefinitely. Natural Grocers® did and may still market Cultures for Health yogurt cultures. I have been making yogurt since 2017 and started with a Cultures for Health heirloom culture from Natural Grocers®.

Based on some input, maybe from Cultures for Health, the amount of yogurt to use as starter for the next batch is about 1-2 tablespoons per pint. (Five to nine tablespoons for five pints is what I calculated.) I add 1.6 tablespoons of yogurt per pint of milk, which is 1/2 cup of starter for 2.5 quarts milk.

I had an email conversation back and forth with Cultures for Health, and they suggested that the yogurt being cultured for starter should be allowed to culture for 5-8 hours only. This is for the health of the culture. It might be fine, but if the yogurt for starter is allowed to culture longer, the culture itself could become starved and hence would not be as healthy.

 

[bernardsmith]

I am a wee bit skeptical that the yogurt culture you add is capable of consuming all the lactose (I presume they convert lactose into acids) in 8 hours. I regularly make hard cheese and I add about a quarter cup of kefir as my inoculant to a gallon of milk, and if I age the cheese 1 month there is still some lactose. Three months , and there is still lactose. Longer aged cheeses may be mostly lactose free... but 8 hours seems incredibly fast despite the fact that we are talking about the milk being at 110 F...

 

[d40dave]

I used this:
https://yogourmet.com/en/usa/product-details/original-yogurt-starter/I ran out several years ago and now use two tablespoons of the previous batch to make the next batch. It tastes fine to me and seems the same as when I first made it.

 

[bernardsmith]

I guess the idea that the bacterial strains mutate in ways that will produce flavors we may dislike comes from the idea that when wine makers use a variety of yeasts in the same batch they should not attempt to harvest them for reuse because although they may have decided to use say 1/3 qty of each of 3 yeasts for the total amount of yeast they pitch, different yeasts may dominate and be more powerful at creating the environment they prefer so that after a single use the 1/3 -1/3 - 1/3 may be 1/2 -1/4 - 1/4 or even 3/4- 1/4 -0 and so the subsequent batches may not taste anything like the first batch and the same problem MAY occur with bacteria that constitute the yogurt. I may use three different cultures applied by the yogurt company but I have no idea whether these three cultures grow together or whether they are combined when a new batch is being made, and kept absolutely separate at other times.. If the latter, flavors may indeed change and I have no control over which , if any bacterium dominates..

 

[beermanpete]

I have been repitching a store-bought strain weekly for over a year and it seems fine. I think it improves over. I do use a large (4 oz.) pitch for one quart of milk.

 

[lumbergh]

I use this yogurt culture by a company called CHR Hansen. A friend gave it to me. Not sure where he got it (might have 5 fingered it from work). It's super concentrated. 1/4 tsp per gallon, so I don't re-pitch.

 

[estricklin]

I used to make 1 gallon batches of yogurt on a pretty regular basis, to eat with smoothies. Not sure why I never considered re-pitching. I always bought some unflavored yogurt, off brand, and just pitched about 4oz in 1 gallon.