Real sourdough bread is incredibly simple and has many unexpected health benefits [Photo courtesy Fourth Estate Publishers]

In praise of sourdough

5 September, 2013

By Andrew Whitley, Bread Matters
Natural Health News

This month has been designated Sourdough September by the UK’s Real Bread Campaign. It’s also Organic September. Uniting those two themes, Andrew Whitley founder of Bread Matters and a trustee of the Soil Association, explains what sourdough is, why it is so important for health and how to recognise the real thing.

Sourdough bread, that emblem of artisan baking, is going mainstream. Good news – or is it? When a previously niche product starts appearing in supermarket in-store bakeries, it’s natural to wonder whether it’s the real thing. But big companies’ propensity to cut corners and homogenise quality is made easier by the absence of any legal definition of sourdough, despite calls by the Real Bread Campaign.

Sourdough is a culture of yeasts and beneficial bacteria that occur naturally in bread flour and dough. The yeasts are more varied and less concentrated than baker’s yeast, so they raise the dough more slowly. The lactic acid bacteria (LAB) also require many hours of fermentation to work their wonders.

Real sourdough is incredibly simple, as befits a method that’s thousands of years old. You take some starter, refresh it with several times its own weight of fresh flour and water and let this ferment for some hours until the yeast population has grown. You use most of this dough to make bread by adding more flour, water and salt, and keep a little bit back as your starter for the next batch of bread.

(Don’t be put off by recipes that tell you to fuss over and ‘feed’ your starter regularly: we’re talking fermentation here, not pet-care. Established starters will keep undisturbed in the fridge for days, weeks or months between bakes.)

Time is crucial. If the sourdough is allowed to ferment slowly over several hours, it is able to transform the main ingredient – flour – in ways that together justify sourdough bread’s claim to be the best. Research done in the past fifteen years has revealed the multiple benefits of sourdough (1).

Here’s a summary:

Sourdough LAB can modify the bits of gliadin and glutenin protein in wheat flour that are toxic to people with coeliac disease (CD) and non-coeliac gluten sensitivity (2-6). This doesn’t mean CD sufferers can eat all (or even any) sourdough bread. It does mean that there is a time-honoured method for making wheat flour more digestible and that we urgently need to know which types of bread on sale in the shops deploy this to real effect.

LAB (including those commonly found in sourdough bread) produce beneficial compounds: antioxidants (7), the cancer-preventive peptide lunasin (8), and anti-allergenic substances, some of which may help in the treatment of auto-immune diseases (9). Interestingly, these by-products seem able to survive heating, suggesting that baked sourdough bread may have ‘probiotic’ potential (10) by stimulating immune responses in the gut (11).

Bread, especially if made with unrefined flour, is a significant source of dietary minerals such as iron, calcium, magnesium and zinc. But a slice of fast-made wholemeal may be nutritious only in theory if its contents pass straight through the body without being absorbed. The main culprit here is phytic acid, present in the bran layers of cereals, which ‘locks up’ the important minerals. Several hours of fermentation with sourdough is sufficient to neutralise phytic acid and make the minerals more bioavailable (12-13).

Problematic protein fragments are not the only thing in bread that we might want to reduce to a minimum. Acrylamide, a suspected carcinogen, can be found in bread crusts. Long fermentation, typical of sourdough systems, can reduce levels of the amino-acid asparagine that is a precursor of acrylamide formation (14).

Bread is often avoided by those affected by weight-gain and metabolic syndrome – rightly, perhaps, in the case of industrial white loaves with a high glycaemic index (GI). But sourdough LAB produce organic acids that, under the heat of baking, cause interactions that reduce starch availability. The lowest GI breads are whole-grain sourdoughs with a compact texture (15).

The list of benefits from sourdough seems pretty compelling even if we ignore the fact that bread-related metabolic complaints have proliferated just as the time taken to ferment most commercial bread has reduced. It’s this interplay of time and commercial advantage that should make us ask searching questions of some of the ‘sourdough’ breads now on offer.

Since there is no legal definition of sourdough, it is quite possible to give this name to a bread made with a dried sourdough powder or ‘pre-mix’ and raised quickly with baker’s yeast. Such bread may be shaped in a winsome ‘boule’. It may even have a hint of flavour. But it’s unlikely to deliver on any of the benefits listed above unless lactic acid bacteria have fermented the dough for several hours. It’s even possible that ‘sourdough’ is being used as an opportunistic descriptor of ordinary bread in the hope of selling more, rather as the label ‘organic’ would be used by unscrupulous greengrocers in the days before that trade was properly regulated.

Signs that your sourdough is real:

the bakery keeps its own sourdough starter (if not, it must be using dried sourdough powder)
the bread is made from scratch on the premises (i.e. is not ‘half-baked’ or re-heated)
the baker knows what sourdough is and is happy to discuss the process and the time it takes
the bread has no added baker’s yeast – or any additives, though this is hard to establish since the most problematic enzyme additives are classed as ‘processing aids’ and don’t have to be declared on the label
it tastes good and is easy on the digestion.

But the best way knowing that your sourdough is genuine is to make it yourself. And the really good news is that it’s easy to fit it into busy lives.

Here’s a BreadMatters recipe for Sourdough Country Bread to get you started.

On September 2^nd Andrew Whitley launched the UK’s first organic sourdough starter and a new community called the Fungal Network, a place to meet and share sourdough, stories and baking skills.
Andrew founded the Village Bakery in Cumbria in the 1970s and co-founded the Real Bread Campaign in 2008. In 2003 he started Bread Matters to raise awareness of how good bread can be if we get it right. His book Bread Matters and his famous courses have helped spark the new home-made bread revolution and ensured that sourdough is at its heart.
The next Bread Matters Sourdough Special course is on September 21-22, 2013.

References

1. Katina, K et al, Potential of sourdough for healthier cereal products, Trend Food Sci Technol, 2005; 16: 104–112.

2. Gänzle, MG et al, Proteolysis in sourdough fermentations: mechanisms and potential for improved bread quality, Trend Food Sci Technol, 2008; 19: 513-52.

3. Di Cagno, R et al, Sourdough bread made from wheat and non-toxic flours and started with selected lactobacilli is tolerated in coeliac sprue patients, Appl Environ Microbiol, 2004; 70(2): 1088-96.

4. Rizzello, CG et al, Highly efficient gluten degradation by lactobacilli and fungal proteases during food processing: new perspectives for celiac disease, Appl Environ Microbiol, 2007; 73(14): 4499-507.

5. Di Cagno, R et al, Use of selected sourdough strains of Lactobacillus for removing gluten and enhancing the nutritional properties of gluten-free bread, J Food Prot, 2008; 71(7): 1491-5.

6. Di Cagno, R et al, Proteolysis by sourdough lactic acid bacteria: effects on wheat flour protein fractions and gliadin peptides involved in human cereal intolerance, Appl Environ Microbiol, 2002; 68(2): 623-33.

7. Coda,R et al, Selected Lactic Acid Bacteria Synthesize Antioxidant Peptides during Sourdough Fermentation of Cereal Flours, App Environ Microbiol, 2012; 78(4): 1087–1096.

8. Rizzello, CG et al, Synthesis of the Cancer Preventive Peptide Lunasin by Lactic Acid Bacteria During Sourdough Fermentation, Nutri Cancer, 2012; 64: 1, 111-120

9. Nonaka, Y et al, Antiallergic effects of Lactobacillus pentosus strain S-PT84 mediated by modulation of Th1/Th2 immunobalance and induction of IL-10 production, Int Arch Allergy Immunol, 2008; 145(3): 249-57.

10. Poutanen K et al, Sourdough and cereal fermentation in a nutritional perspective, Food Microbiol, 2009; 26: 693–699.

11. Van Baarlen, P et al, Differential NF-kB pathways induction by Lactobacillus plantarum in the duodenum of healthy humans correlating with immune tolerance, Proc Natl Assoc Sci, 2009; 106: 2371–2376.