Sourdough Starter - a little info

I absolutely adore the smell of freshly baked bread. There is something about the smell that tells me to grab the bread knife & butter and tuck in to a still warm piece of bread. Who would have thought that a fungus could help make something so delicious. I know, I know, black truffles are fungi too, so are mushrooms :) & they can be part of absolutely wonderful dishes but freshly baked bread when the crust is still thick & crusty & warm & the butter melts in to the bread is simply delicious. Freshly baked bread is fantastic simple fare.

The choice is whether to make the bread with a commercial yeast (usually dried) or with 'wild' yeast as part of a sourdough culture. Baking bread with dried yeast is relatively easy (provided the yeast are alive). Baking bread using a sourdough culture can also be easy provided you keep the culture alive. 

Dried yeast = Saccharomyces cerevisiae aka ale yeast, top-fermenting yeast, baker's yeast, budding yeast & possibly many more. Apparently saccharomyces means 'sugar fungus' in Latinized Greek (Latinized Greek!!!!). I guess baker's yeast need a little sugar in their diet. 

A sourdough starter will contain both yeast & Lactobacillus bacteria as part of a symbiotic culture. In sourdough breads the yeast provided the gas for the lift & the Lactobacillus bacteria provided the acid (lactic acid) for the sour. In most wild sourdough cultures Saccharomyces cerevisiae is the dominant fungal species (other fungal species commonly found in wild sourdough cultures include Candida humilis, Candida milleri & Kazachstania exigua). Typical sourdough Lactobacillius species are Lactobacillus fermentum, Lactobacillus paralimentarius, Lactobacillus plantarum and Lactobacillus sanfranciscensis (definitely needed for San Franciscan sourdough!) - I hope your eyes haven't glazed over too much. One of the many wonderful things about sourdough is that there is incredible diversity between cultures (or within cultures fed different things) & this will impact on the flavour of the bread. 

The starter is also known as the  "leaven",  "chief", "chef", "head", "mother" or "sponge". 

So how do you get/make a sourdough starter? Basically there are three options; a) the easiest way is to get a little from a friend (& convert it to gluten free if the starter is fed with wheat/rye), b) buy a commercially available sourdough starter (& convert it to gluten free if the starter is fed with wheat/rye) or c) make your own.   

Options a) & b) will probably require you to convert the starter from being fed with wheat/rye to a gluten free diet. It is possible to make it a gluten free sourdough culture, it will however require you to feed it daily for at least to 2 weeks prior to using it to make bread. I was given 50 g of a rye sourdough culture that has been fed with rye flour for the past 4 years, the sample contained 25 g of rye flour & 25 g water. Following is a table that shows the number of feeds that are required to make it considered gluten free. Remember that whole rye flour was used not actual gluten. It was hard to find the figure for the actual percentage of gluten in rye however the total protein content is ~11% or 11 g/100 g as such the amount of gluten would be less than this. Based on the current gluten detecting kits being able to measure down to 3 ppm (parts per million) of wheat gluten, the current Australian standard for labelling something gluten free is less than 5 ppm, the sourdough culture would be considered gluten free by Day 13. That doesn't mean that you have to use it from Day 13, you could keep the culture going for another 10 days by that time the amount of rye flour present would be ~1 part per trillion.  

Feed Number Amount of starter Add Water Add Sugar Source Amount of Rye flour remaining
1 50 g of Original culture 100 g 50 g sweet potato 25 g
2 50 g of Day 1 culture 100 g 50 g sweet potato  6.25 g
3 50 g of Day 2 culture 100 g 50 g sweet potato  1.56 g

50 g of Day 3 culture

100 g 50 g sweet potato  0.39 g 
50 g of Day 4 culture  100 g 50 g sweet potato  0.098 g 
50 g of Day 5 culture  100 g 50 g sweet potato  0.025 g 
50 g of Day 6 culture  100 g 50 g sweet potato  0.0063 g 
50 g of Day 7 culture  100 g 50 g sweet potato  0.0016 g 
50 g of Day 8 culture  100 g 50 g sweet potato  0.0004 g 
10  50 g of Day 9 culture  100 g 50 g sweet potato  0.0001 g
11  50 g of Day 10 culture  100 g 50 g sweet potato  0.000025 g 
12  50 g of Day 11 culture  100 g 50 g sweet potato  0.0000062 g 
13  50 g of Day 12 culture  100 g 50 g sweet potato  0.0000015 g or 1.5 ppm
14 50 g of Day 13 culture 100 g  50 g sweet potato 0.0000003 g or 0.3 ppm
15 50 g of Day 14 culture 100 g  50 g sweet potato 0.000000075 g or 0.07 ppm

 

I feed my culture (nearly) every day using 50 g of the previous days culture, 50 - 70 g roasted sweet potato, 100 g of water & 50 g Bakers' Magic gluten free flour (I know someone who has kept their culture going for 40 years! - I've got a long way to go). BTW I use a fresh container each day. More on feeding further down the article.   

I have not cultured my own sourdough starter however there are fantastic articles on the web relating to starting a sourdough culture (some wheat/rye based & some gluten free).  In particular How to make Sourdough Bread by Emma Christianson on the Kitchn website, another by Jenny McGruther can be found on the Nourished Kitchen website and I love the use of organic red cabbage leaves to start the culture found on Michael Ruhlman's website. If you want to be sure that you can make a sourdough culture using gluten free flours read Jeanne Sauvage's article on her website Art of Gluten Free Baking.

Feeding your starter/What to feed your starter. In a nutshell you need to feed your yeast sugar. Of course, not just sugar but there needs to be a sugar source for the yeast. Different types of yeast like different types of sugar (sucrose, glucose, fructose) & this will have an impact on the flavour of the bread. When you make a starter using wheat/rye flour you have already got a variety of yeasts & bacteria/bacterial spores present in/on the flour. As such some starter instructions are simply mix flour & water & let it sit at room temperature for a couple of days until it starts bubbling. One of the reasons that that is possible is that both wheat & rye contain a small amount of sugar (approximately 1-2 %) & amylase, an enzyme that breaks starch molecules into sugar. There is a lot of potential sugar in wheat & rye flour as these flours are at least 65% starch.

Is there any or is there a potential sugar source in your gluten free flour that you are going to use? The 0.1 g/100 g of sugar in Bakers' Magic gluten free flour is not sufficient to maintain a sourdough culture. A potential source of sugar is the breakdown of starches by amylase to glucose & other oligosaccharides. Bakers' Magic gluten free flour is ~60% starch however the other flours present in this blend either do not have or the amylase present is not sufficiently active to be able to maintain a sourdough culture. Therefore to keep my sourdough culture alive & well I add in a sugar source (rice bran syrup, roasted pumpkin, roasted sweet potato, table sugar, coconut sugar).   

You may want to make a gluten free sourdough culture out of another gluten free flour or a combination of gluten free flours. Basically you need to ensure that there is a sugar source for your yeast. A good indication is if someone has made an alcholic drink from the grain of the flour.