Initiating a new starter with fruit and veg
I hadn't really considered this, but I have been fascinated by the question of where all the microbes in a starter come from, particularly in the light of the paper by Landis et al The diversity and function of sourdough starter microbiomes , which has of course been discussed here.
The question of why these starters are different is not really addressed by the research, but in an interview with The Bread Code Landis herself suggested that if someone's starter wasn't doing well, they should buy/borrow one and keep that as she had found that starters were quite persistent, ie a mix of microbes that works will survive in a range of environments.
Landis also wrote a nice summary of the types of yeast typically present in sourdough on microbialfoods.org. This particularly interested me, as she says that Kazachstania servazzii is responsible for high CO2 production, yet her final research indicated that this is not present in many souordough cultures, in fact in many the predominant yeasts are types of Saccharomyces Cervisiae, ordinary bread yeast. Which (S. Cerevisiae) doesn't like acid conditions so much and would not be optimal (according to established lore and probably research also).
Doing some further research I found an article by Ripari, Ganzle and Berardi, Evolution of sourdough microbiota in spontaneous sourdoughs started with different plant materials. My take-home from this was that, so far as the lactic acid producing bacteria are concerned, some important ones, including L. Sanfranciscensis, are not ubiquitous and so may not arise in a from-scratch starter - but once introduced, such bacteria will establish themselves. It also mentions using plant and flower material in the initiation stages of the starter to provide a source for the full range of bacteria. This reminded me of my grandfather feeding his yeast potato peelings.
Putting all this together, it appears to be a reasonable hypothesis that some yeasts also might fall into the category of microbes that might, but might not, find their way into a from-scratch starter. Probably the ubiquitous S. Cerevisiae will, not necessarily the others. Or more generally, lack of availability of microbes in the environment in which a starter is initiated can limit those that are found in the final, stable culture.
This struck a chord with me as my starter, though it makes tasty bread that is not too dense, is not a massive riser. If I wait until my bulk dough has expanded 50% by volume, it will be way overproofed. 20% or less works for me, though clearly others have different experiences. Maybe mine is one of those without the gassy sourdough-specific yeasts in it.
So I have decided to kick off another starter using Debra Wink's pineapple juice method, but adding blossom/flowers and skins of fruit (nowhere near ripe pears and plums) from the garden, and also peelings and trimmings from some carrots and a cabbage from our local organic supplier (muck brushed off, but not washed). For the flour I am using a bit of everything in the cupboard, all in the cause of biodiversity.
So far, it has behaved a little differently, after a couple of days I was getting behaviour quite similar to a mature starter - rising well in the same sort of times. It is now at 4 days, I am not able to judge the aroma yet as it is just coming off the pineaple juice and has some vegetably smells as well. Once it has been going for a week or so and I have stopped feeding it fruit and veg I will try a side-by-side feeding cycle with my existing starter to see if there is any difference and report back. And if it works, then a loaf test...
(I am posting this now to make sure that I do report back and carry on with the experiment!)