I have plenty of self-raising flour (which will easily take me until its best before date to use) but am running very low on plain flour which I use predominantly for making a roux and then ultimately a bechamel. Given the current circumstances it seems appropriate to use up things I already have in the cupboard, rather than purchasing more if I don't need to.

Will the added raising agents in self-raising flour (the flour I have is from Sainsbury's and contains Calcium Phosphate and Sodium Hydrogen Carbonate, apparently) affect the production of a roux and then ultimately a bechamel sauce from the roux?

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    I'd say go for it. I recently accidentally made one with cornflour & it came out 'acceptable' if not perfect. See cooking.stackexchange.com/questions/33227/… for more alternatives. – Tetsujin Mar 22 '20 at 10:09
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    I think it'll just end up a little more salty than a usual bechamel. You might get some puffing up when first added, but this should disappear over time I think – bob1 Mar 22 '20 at 10:15
  • I used some gluten-free flour (mainly rice) and it needed a little more than if I'd used plain. The effect of the raising agents may be a little different to the effect of the source of strach though. (@Tetsujin) – Chris H Apr 8 '20 at 11:50
  • @bob1 - I'm just going round the site correcting this - UK self-raising flour does not contain salt. US self-rising flour does. – Tetsujin Apr 20 '20 at 15:10
  • @Tetsujin - the salt taste comes from the sodium in the bicarbonate component in the baking powder. This is irrespective of the source of the flour, though it seems you are correct - the US version does contain extra salt. I'm not from the US (though recently worked there) and wasn't aware of the difference between the US and UK versions. – bob1 Apr 20 '20 at 23:25

Since you will only be using 1.5 tablespoon of flour for more than a cup of milk, it shouldn't impact the flavor. Also as there is no salt in the Sainsbury Self-raising flour, you will not need to adjust for salt. However, the alkalinity from the Sodium Hydrogen Carbonate as it heats and breaks down into Sodium Carbonate might impact the flavor. But, the acidity of the milk and butter should counter that, so it wouldn't be noticeable.

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    The bicarb should react out to form bubbles of CO2, which shouldn't cause a problem – Chris H Apr 8 '20 at 11:51
  • This is the thermal decomposition reaction, 2 NaHCO3 → Na2CO3 + H2O + CO2 @ChrisH That is the absence of an acid, but the lactic acid will cause an acid base reaction and just lead to CO2 like you said. – user29568 Apr 8 '20 at 12:06
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    I'm we;ll aware of the thermal decomposition reaction, having used it myself, but as you correctly state both milk and butter are (slightly) acidic, so we should have an excess of lactic acid, with which the bicarbonate (or carbonate if it thermally decomposes first) will react to form sodium lactate. It's not a matter of the acidity counteracting the flavour of the alkaline raising agent, but causing it to no longer exist – Chris H Apr 8 '20 at 12:17
  • @ChrisH Perfectly said, speaking of flour its so hard to find any in the UK – user29568 Apr 8 '20 at 14:42

In terms of thickening this should work, but keep in mind that you're adding salt* and baking powder which will affect the flavor of the roux. You should do a side-by-side test with AP and self-rising flour and taste both, then finish your béchamel sauce and try both and post your results here.

*Note: salt is included in self-raising flour in the US and Canada but not in the UK.

  • Thanks for taking time to answer, but.... "try it yourself and tell us what the result is" doesn't exactly answer my question; particularly as I'm at pains to point out in the question that this is because I'm low on plain flour and have plenty of self-raising. For info; I haven't seen plain flour in my local supermarket(s) for the best part of two weeks (hurrah for people panic buying!) and I'm loathe to buy what others may need when I may have alternate options. Now is not the time for me to waste by trying =) – Rob Mar 23 '20 at 20:16
  • I believe I did answer the question. It's just flour with baking soda and salt, so you'll need to adjust your recipe to account for this (e.g. reduce the amount of salt in the béchamel). If you make the sauce with your self-rising flour it would be useful to others if you post your results which is why I asked that you do so. – myklbykl Mar 23 '20 at 21:14
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    Where are you that there's salt added to your SR flour? Here it's (fortified like most if not all) flour plus raising agents. Why would anyone want salt added as bought? – Chris H Apr 8 '20 at 11:49
  • @ChrisH — all the SR flour I find on line has salt (e.g. bobsredmill.com/blog/featured-articles/…), and all the recipes I find to make it also have salt (e.g. thekitchn.com/how-to-make-self-rising-flour-232729). Where do you live that they deprive you of salt? I don't use SR flour myself. – myklbykl Apr 8 '20 at 14:51
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    P.S. Spruce Eats says: "Self-raising flour is a common ingredient in recipes from the UK.... It is made with a bit more baking powder and no salt, which differentiates it from the self-rising flour typically found in the United States and Canadian markets." – myklbykl Apr 8 '20 at 15:13

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