So excited to read the interview! I remember mentioning Ian and his work to you last January, when you emailed me about sucrose in sweet sourdough fermentation.
I am so happy the two of you were able to connect!
The interview is so detailed and technical that it takes some time to digest. Thanks for sharing.
Ian, could you elaborate more on this fragment: "Yeast, on the other hand, have the opposite experience. The short refreshments leaves a higher percentage of mother cells with thickened membrane structures in the yeast population,".
Why is the opposite in Yeasts? Is this a "kind" of training for osmotic stress?
Without getting too technical, ascomycetous yeast, during vegetative growth (like occurs in sourdoughs), reproduce by budding. It literally looks like the paddles of a prickly-pear cactus, with new, smaller paddles branching off (and eventually detaching from) the larger "mother" paddle. Similarly, in yeast, mother cells are substantially larger than daughter cells, with thickened cell walls. This is due to the fact that chitin, a tough, elastic material, localises at budding scars, which "older" mother cells possess in higher number. (Each new daughter cell produces a fresh budding site. Once there are no more sites left, game over. Death.)
Replicative ageing in unicellular microbes occurs because of asymmetrical reproduction. In yeast, older mother cells physiologically inherit the "older" cellular parts, including cell-wall structures with more budding scars. For the record, the "lifespan" of a typical yeast is estimated between 15 to 30 budding cycles.
Due to their thickened cell walls and larger size, mother cells (of a certain replicative age) have higher rates of survival relative to daughter cells during sudden shifts in osmolarity. In case it's not obvious re: volume, the Laplace and osmotic pressure experienced by spherical objects increases as object volume decreases, increasing by orders of magnitude due to the exponential nature of the scaling relationship.
> mother cells are substantially larger ... with thickened cell walls ... this due to the fact that chitin ... localises at budding scars, which "older" mother cells possess in higher number
> older mother cells physiologically inherit the "older" cellular parts, including cell-wall structures with more budding scars.
So short refreshments with high inoculation preserves more older cells and creates less newer cells, which is why you get better tolerance, or am I way off base? Because based on your post I think you are saying "older" = "tougher", but this is my attempt to dramatically simplify your post.
Richard - I think the idea is short, high ratio refreshments encourage yeast budding and retain a large percentage of the previous refreshment(s) in the mixture, which means there will be more mother cells than there would otherwise be. So it doesn't really create fewer daughter cells, it just increases the *ratio* of mother to daughter cells in the mixture. (But the effect is the same.)
Mother cells of a (certain) replicative age have a larger volume, more chitin in their cell wall, and a thickened membrane structure. All the above lead to cells that respond better to osmotic stress.
Awesome reading... Thank you Andrew and Ian!! Now to think, formulate and experiment. My heart is with using this technique for more whole grain products... Ian- how about use of salt as an inhibitor for bacterial activity at the sweet (and/or salty) starter stage?
Hazim - So glad you found the interview enlightening! I had a thought: maybe the best way to get Ian to see and answer follow-up questions is to cross-post them as comments on my Instagram announcement here: https://www.instagram.com/p/C3nGyM8M3uo/. I'll try to copy over the best ones here, so they'll all be in one place.
Here are two things to think about. First, salt alters osmolarity and ionic strength. As such, it has much greater consequences for the growth rate of both yeast and bacteria. Second, the amount salt you'd need is well over 4% to total flour weight in, both, the starter and in final-dough conditions. Would you find that palatable? (For the record, I've done experiments with salt, all the way put to 8%, working in increments, as I do. Sugar's better in every way.)
Thanks for sharing that Ian. Definitely 4% would not be to my taste, and I suspect anybody's. I was hoping one could get by with a higher salt% in the starter stage without overdosing the final stage.
Wow! Just Wow! I've been reading this post over a few times to try to understand and digest it. I took the plunge and made a brioche coffeecake using James MacGuire's brioche recipe. He uses a sweet preferment and I substituted the sweet starter for the preferment (because I didn't want to math). I am blown away by it! It behaved exactly as you described and the taste had no perceptible acidity or funkiness. I just made it this morning so can't speak to keeping quality, but am in the process of going through it again to bake more using it. Thanks to you and Ian for the great explanation and sharing of knowledge!
This is such a fascinating read! I am glad that I came across this article, but I think I need to read it a few more times to digest it. However, I do have a question, Ian mentioned that he didn’t have a proofer when he first started his one-man bakery, hence came up with this stiff starter, how did he control temperature? I don’t have a proofer but extremely interested to try it out. Hope you can point me to the right direction. Thank you!
Anazing, thanks Andrew and Ian!
So excited to read the interview! I remember mentioning Ian and his work to you last January, when you emailed me about sucrose in sweet sourdough fermentation.
I am so happy the two of you were able to connect!
I remember! And I am too!
My head just exploded 🤯 thank you for sharing
join the club, Carla
Let me know if you try it! Dayna is already all in on SS breads
The interview is so detailed and technical that it takes some time to digest. Thanks for sharing.
Ian, could you elaborate more on this fragment: "Yeast, on the other hand, have the opposite experience. The short refreshments leaves a higher percentage of mother cells with thickened membrane structures in the yeast population,".
Why is the opposite in Yeasts? Is this a "kind" of training for osmotic stress?
Without getting too technical, ascomycetous yeast, during vegetative growth (like occurs in sourdoughs), reproduce by budding. It literally looks like the paddles of a prickly-pear cactus, with new, smaller paddles branching off (and eventually detaching from) the larger "mother" paddle. Similarly, in yeast, mother cells are substantially larger than daughter cells, with thickened cell walls. This is due to the fact that chitin, a tough, elastic material, localises at budding scars, which "older" mother cells possess in higher number. (Each new daughter cell produces a fresh budding site. Once there are no more sites left, game over. Death.)
Replicative ageing in unicellular microbes occurs because of asymmetrical reproduction. In yeast, older mother cells physiologically inherit the "older" cellular parts, including cell-wall structures with more budding scars. For the record, the "lifespan" of a typical yeast is estimated between 15 to 30 budding cycles.
Due to their thickened cell walls and larger size, mother cells (of a certain replicative age) have higher rates of survival relative to daughter cells during sudden shifts in osmolarity. In case it's not obvious re: volume, the Laplace and osmotic pressure experienced by spherical objects increases as object volume decreases, increasing by orders of magnitude due to the exponential nature of the scaling relationship.
> mother cells are substantially larger ... with thickened cell walls ... this due to the fact that chitin ... localises at budding scars, which "older" mother cells possess in higher number
> older mother cells physiologically inherit the "older" cellular parts, including cell-wall structures with more budding scars.
So short refreshments with high inoculation preserves more older cells and creates less newer cells, which is why you get better tolerance, or am I way off base? Because based on your post I think you are saying "older" = "tougher", but this is my attempt to dramatically simplify your post.
Richard - I think the idea is short, high ratio refreshments encourage yeast budding and retain a large percentage of the previous refreshment(s) in the mixture, which means there will be more mother cells than there would otherwise be. So it doesn't really create fewer daughter cells, it just increases the *ratio* of mother to daughter cells in the mixture. (But the effect is the same.)
Mother cells of a (certain) replicative age have a larger volume, more chitin in their cell wall, and a thickened membrane structure. All the above lead to cells that respond better to osmotic stress.
What did one microbe say to the other? I'm still digesting this.
This is so wildly cool to read!!!
Awesome reading... Thank you Andrew and Ian!! Now to think, formulate and experiment. My heart is with using this technique for more whole grain products... Ian- how about use of salt as an inhibitor for bacterial activity at the sweet (and/or salty) starter stage?
Hazim - So glad you found the interview enlightening! I had a thought: maybe the best way to get Ian to see and answer follow-up questions is to cross-post them as comments on my Instagram announcement here: https://www.instagram.com/p/C3nGyM8M3uo/. I'll try to copy over the best ones here, so they'll all be in one place.
Here are two things to think about. First, salt alters osmolarity and ionic strength. As such, it has much greater consequences for the growth rate of both yeast and bacteria. Second, the amount salt you'd need is well over 4% to total flour weight in, both, the starter and in final-dough conditions. Would you find that palatable? (For the record, I've done experiments with salt, all the way put to 8%, working in increments, as I do. Sugar's better in every way.)
Thanks for sharing that Ian. Definitely 4% would not be to my taste, and I suspect anybody's. I was hoping one could get by with a higher salt% in the starter stage without overdosing the final stage.
Wow! Just Wow! I've been reading this post over a few times to try to understand and digest it. I took the plunge and made a brioche coffeecake using James MacGuire's brioche recipe. He uses a sweet preferment and I substituted the sweet starter for the preferment (because I didn't want to math). I am blown away by it! It behaved exactly as you described and the taste had no perceptible acidity or funkiness. I just made it this morning so can't speak to keeping quality, but am in the process of going through it again to bake more using it. Thanks to you and Ian for the great explanation and sharing of knowledge!
So glad to hear that, Karen! It's magical.
Glad to see Ian on Wordloaf. I've learned a lot reading his Instagram grams over the last few years.
This is such a fascinating read! I am glad that I came across this article, but I think I need to read it a few more times to digest it. However, I do have a question, Ian mentioned that he didn’t have a proofer when he first started his one-man bakery, hence came up with this stiff starter, how did he control temperature? I don’t have a proofer but extremely interested to try it out. Hope you can point me to the right direction. Thank you!
So very interesting! Thank you for sharing.