What flour do you have in your cupboard right now? I’m guessing you have regular wheatflour and perhaps some cornflour for thickening. You’ve probably noticed the flour category in the supermarket has grown and even more so in healthy food stores. And did you know you can make your own oat flour by pulverizing rolled oats in a food processor? Enjoying a wider variety of grain flours and switching to wholegrain versions is a healthy way to go. Like many people during these COVID-19-troubled times, my mum started a sourdough bread making habit. But her husband was recently diagnosed with pre-diabetes, so she asked me how to make the bread better for him. Bread is a significant contributor to the overall glycemic load of the diet so the challenge was set: how do we lower the glycemic impact of sourdough? Sourdough bread already has a lower GI than conventionally baked bread because of the acids produced during fermentation (the ‘sour’ in sourdough), however the obvious question was, how low can you go? I used several principles to lower the glycemic impact of the bread:
- Change the type of starch (flour);
- Reduce the amount of starch by adding fats and protein;
- Adding fibre.
Lowering the GI of the flour mix is not easy because the GI rating of flours are not available. This is because GI testing involves feeding real people 50g of available carbohydrate in the food and then measuring their blood glucose over a couple of hours; Half a cup of flour paste eaten with a spoon anyone? Nah, me neither! I had to take an educated guess on the effect of using different flours based on the GI of the original grain. For example, oats, lentils and chickpeas are low GI. But you must factor in the change of physical form that a grain or legume undergoes to turn it into flour. The body has easier access to the starch, and it is more quickly digested and absorbed so this increases the GI. It’s still worth it though, because you are adding nutrients and variety to the diet rather than getting stuck in a wheat rut. Then came the challenge of creating a pleasant texture. Baking is an art and a science. For example, oat and legume flours have no gluten that gives structure to bread, so you get a denser, less springy loaf. Even though the sourdough culture helps add carbon dioxide gas bubbles, you need enough gluten within which to trap the gas, which adds volume and lightness. To do this you can buy pure wheat gluten to add to the mix for a lighter result. This also increases the protein content of the loaf, which can also reduce the GI; a win-win! Here are the tweaks we made to achieve a delicious lower GI sourdough loaf:
- We combined 75% wholewheat flour base with 25% ‘other’ flour, such as oat, rye, soy, sorghum, chickpea or lentil. Any more than 25% and we found it too dense, but you can experiment with up to 50% ‘other’ flours.
- We added wheat gluten to the mix to boost volume and springiness (follow pack instructions, but usually 1 tablespoon gluten to 2 cups flour).
- We added seeds such as pepitas (pumpkin seeds), linseeds (flaxseed) and sunflower seeds to increase fibre, nutrients (and fats and fibre that lower the GI). You could also add whole cooked soybeans or nuts. Enjoy being creative with flavours and textures.
- The bread is denser and heavier than supermarket bread so make slices smaller so as not to go overboard on the total carbs and energy.
When the going gets tough making your own bread can be a wonderfully comforting activity. Throwing some new and varied ingredients into the mix can make a wholesome food even better.
|Wholegrain mixed flour sourdough bread|
|Health Star Rating = 4 Stars|
|Glycemic index 48-57|
|Serving size – 2 slices (70 g or 2.5oz)|
|Fats (g) – total||1.7|
– Saturated fat (g)
|– Unsaturated fat (g)||2.2|
|Saturated : unsaturated fat ratio||0.2|
|Carbohydrates (g)– Total||30|
|–Natural sugars (g)||0.9|
|–Natural starches (g)||25.1|
|–Added sugars (g)||0|
|–Added starches (g)||0|
|–Dietary fibre (g)||4|
|Ingredients: based on 75% wheatflour and
25% mixture of oat, rye and rye, with added
seeds. Adding less salt will reduce sodium
content of the bread.
GI of sourdough breads
|Bread type||Glycemic index|
|Sourdough wheat bread||54|
|Sourdough rye bread||48 – 57|
|85% barley flour sourdough bread||53|
|Mixed white and wholemeal sourdough
with oat fibre
Source: www.glycemicindex.com, 2021
Nicole Senior is an Accredited Practising Dietitian, author, consultant, cook and food enthusiast who strives to make sense of nutrition science and delights in making healthy food delicious.