Blueberry honeycomb a la sodium bicarbonate!

January 5th, 2012 | Posted by greg in Daily life... | Recipes

Egyptians probably never imagined what they discovered when they started using the ancestor of baking soda to clean their floor!

Nefertari used baking soda too! :) (Picture:

Baking Soda

Sodium bicarbonate is indeed widely used in today’s baking, be it in quick breads, cookies, muffins, cakes or confectioneries. Unlike other leavening methods such as the biological natural yeast or by the physical induction of air in batter (i.e. whipped egg whites for meringue), sodium bicarbonate, otherwise known as baking soda, works on a chemical reaction.

Quite simply, baking soda reacts once it is mixed in an acidic aqueous base. The level of expansion, very much like any other recipe, depends on the hydration of the recipe and the level of starch used in the recipe. For example when baking soda bread, the texture will depend on your liquid content vs. your dry matters and although the volume would also be affected by the addition of eggs for example, the texture will remain fairly dense, as expected in a quick bread. On the other hand, when preparing honeycomb caramel, it is a quasi pure liquid sugar base, where all the water has evaporated and in which baking soda is dropped in at very high temperature. The baking soda then reacts to the acids present in sugar (yes!) and to the high temperature, creating a very light foam resembling shaving foam because of the lack of starch, the texture expands in a very free aerated way. The highly humidity-sensitive candy then sets with the cooling of the cooked sugar, unlike starch based goods which sets because of the coagulation of starch cells.

Baking soda reaction starts immediately after mixing it with a liquid base. The carbon dioxide (CO2) however, is released at 80 degrees Celsius and will cause the baked goods to rise. Therefore, it is important to bake sodium bicarbonate based products soon after the mixing as the effect of the sodium bicarbonate will decrease with time. It can also work in cold process, for example when it is mixed in a purely acidic environment, like on my son’s volcano experiment he received for his birthday, where he pours white vinegar on a spoonful of baking soda and it foams out of the ‘volcano’. (…and where I got to clean the table flooded with bubbly vinegar!)

That's exactly what my son got! ... I can't show you the actual volcano as it experienced technical difficulties after the test. Volcano can fly, did you know that? lol :)

What’s with single and double effect baking powder? And is there a life after mixing?

Baking powder is nothing less than baking soda mixed with one or more acidic elements and a kind of starch serving as anti-caking agent and to give more volume to the powder. Put bluntly, baking soda reacts differently to different acids. Some acids such as mono-calcium phosphate have low-temperature reaction and other acids such as sodium aluminum sulphate/phosphate are high-temperature reacting acids.

The single acting baking powder would contain only one acid reacting at low-temperature (most likely mono-calcium phosphate), meaning that you would need to bake your goods right away as the effect of the baking powder will decrease rapidly over time.

On the other hand, the double acting baking powder, where more than one acid is used, reacts at low temperature with the first acid, but also has a second reaction when temperature passes over 80 degrees Celsius from the second acid, making your baked goods rise even after a trip to the fridge, just like with our scones. This type of baking powder is what is mostly used today.

To the popular question on how long can a dough be kept in the fridge before the effect of baking powder dies out, I’ll have to answer out of my 20 years of baking experience. Our scones are baked 2 to 3 days after the dough is mixed. Our financier cakes and madeleines are baked up to 4 days after the mixing time with a consistent development and so are our chocolate chips cookies and our corn flakes cookies! Out of practicality, you might want to keep batters and dough up to 4 days, but further than that, I wouldn’t see the use of keeping it longer, but I assume it could be kept for a week. Our scones are actually kept for a few days in the fridge to allow the dough to settle and rest in order to obtain the best shape possible. (overachievers: follow me!)

Fresh blueberries and freeze-dried blueberries

Practical: Dry Blueberry Honeycomb covered in chocolate

To put into practice the effect of baking soda, try this recipe at home, but be careful, the foam is massive and so is the heat! I am using freeze-dried blueberries because its water level is equal to none. It could be done with spices, other dried fruits or any other dry food. (ah! I just thought about seaweed/black pepper! wondering how it would work…)


  • 320 gm white sugar
  • 80 ml water
  • 35 ml golden syrup
  • 2/3 tablespoon baking soda
  • 30 gm freeze-dried blueberries

The finished blueberry honeycomb covered in chocolate


  1. Prepare the sifted baking soda, ready to be poured in the hot caramel.
  2. Similarly, prepare the crumbled dried blueberries.
  3. Boil all the ingredients until the very beginning of the coloration.  (the sugar will continue to darken as you pour it on the tray)
  4. Drop in the baking soda and whisk a little – be careful, it will triple in volume and produce a large amount of foam.
  5. Add quickly the dried blueberries and pour the mixture on a slightly oiled baking tray. (don’t over mix or it will collapse)
  6. Leave it to cool down for several hours.
  7. Bread into pieces and cover in dark chocolate.

By the way, those delicious pastries are on our afternoon tea selection at the moment! :)

Readers who viewed this post also viewed:

You can follow any responses to this entry through the RSS 2.0 You can leave a response, or trackback.

14 Responses

  • This reminds me Gregoire I should play around with honeycomb more for allergy kid…another treat should could have. thanks x

  • Swee San says:

    Well I do hope Malaysia and hong kong are closer, cause there are so many yummy patisserie n dessert place in hong kong! Looking forward to my trip in July. Hope to be able to meet you in person, chef!

  • Sarah says:

    Thanks for all this useful chemistry information. (I love geeky, serious baking stuff.) I never thought about keeping quick bread or scone batter in the fridge; I usually just bake it straight away. But now I can see the benefits of keeping the batter for a later time. I appreciate when you share your knowledge!

  • Renee says:

    Love the kitchen experimenting Gregoire! This looks like it would be so much fun to do with my little niece sometime. ; )

  • Colette says:

    Excellent, very enlightening post on baking powders! I reflected on this precisely a few months back, I wondered why so many recipes with chemical rising agents suggest to rest batters in the fridge, like Heston Blumenthal’s siphon orly batter (other than to hydrate the flours), when I thought the effect of the rising agent was slowly lost. I wish I’d read your post then!I would have saved some researching to get to that conclusion :) Still, I didn’t know they could be kept refrigerated that long! It’s great to know for a fact!Thank you

    About the honeycomb, I discovered it years back in a trip to Australia, as I felt in love with violet crumble! Tried recipe after recipe (with honey, just sugars, with glucose, with golden syrup) amazed each time by the chemical reaction, but though I managed to get it to look as I wanted, got the texture right…I never got it to taste just right. I always got a bit of an off soapy flavour from the bicarbonate. And when I lowered the amount  to not feel it, it didn’t react enough to get the right texture! So, I’ll definately be trying your recipe!!!!Happy new year, by the way!

    • Wow! Thanks Colette, and yes, happy belated new year to you too! :)
      It makes me very happy to know my post could help you a little with chemical rising agents. That’s the best satisfaction I get out of blogging!

      We’ve been trying numerous recipes for honeycomb too. Ultimately, there is always an underlying baking soda flavor, but we’ve found this recipe to be a bit better, especially after adding dried blueberries and covering it in chocolate – it all balances much better, leveling off the sweetness and the soda taste. I hope this recipe will work out fine for you! :) 

  • Kiranglobalchem says:

    Sodium bi Carbonate India

    Di Sodium Carbonate,Detergents Raw Materials,Water Purification,Exporters Of Sodium Silicate,Glass Manufacturers In India,High Iron Liquid. Di Sodium Carbonate,Detergents Raw Materials,Water Purification,Exporters Of Sodium Silicate,Glass Manufacturers In India,High Iron Liquid.

Leave a Reply

Your email address will not be published. Required fields are marked *

All right reserved