What does happen to the dough during baking?

Hi

I can offer the following information concerning baking a loaf of bread.

The up side is that it is based on information recorded during the baking cycle for a particular style of bread, at specific temperature settings.

The down side is that it will only relate to that type of loaf, and any other variety will require a different profile.

We did this as an exercise in College when I studied for my bakery qualifications, and we undertook a detailed examination of the bake profile for a small white tinned loaf [400g finished weight]

The final dough was proved at 35*C, 80%rH, and placed in the oven at 235*C, with top heat set at 6 and bottom heat at 8 in a deck oven [conduction].   Steam setting of 3 was used.   This would equate to standard commercial settings, although I accept it may mean little to some homebakers...apologies for that.

More meaningful information: it takes a full 10 minutes for the dough centre to reach 53*C, checked using a probe thermometer.   This is the point at which all yeast activity will cease, so is the end point for any "oven spring".   The idea of using steam is to form a moist coating on the surface of the tinned loaf, thereby preventing crust formation, and maximising the oven spring, and, subsequent volume to the finished loaf.

More significant reactions take place around the 15-18 minute mark.   As the core baking temperature reaches the high 60s*C the proteins will start to set, and into the 70s the starches will gelatinise and also start to set.   Nearly at 80 and the Maillard reactions will kick in.   By this stage the loaf has been in the oven for almost 20 minutes.

As the colour forms, the baker will look to reduce the heat to c.220*C and open the damper to release any steam and, thus, pressure beyond this 20 minute mark.

Anticipated baking time is 25 minutes, and a probe thermometer reading of 95*C was taken as standard for a fully baked loaf.

The trouble with par baking is that you have to have both the starch and proteins set, without colouring the loaf.   This means the baking temperature has to be reduced;   inevitably, this necessitates longer baking times, meaning greater moisture loss.   Further heat treatment confers freshness on the baked item, but it does mean further drying out.   This inevitably leads to faster staling as the product cools.

Please note that the information above is as recorded on the day, but it does relate to a specific product-type.   Different loaves need different heat treatment, and will react differently to the product discussed here.

Still, this is a useful illustration of the reactions taking place during the baking cycle, and I hope it gives you greater understanding as to how bread bakes in an oven.

Best wishes

Andy 

Hi Barmaley

Obviously thrse are long and complex answers to your questions, but I'll try give quick and clear points instead, if that's ok?

a) Heating proteins causes them to de nature, and set [eg. egg sets when heated].   Starches swell on heating and thicken by taking up moisture ie. gelatinisation [eg making a roux-based sauce]   I understand these to be the critical aspects of baking, and they happen as the dough passes through temperatures in 60s *C minimum.

b) Secondary baking involves adding colour only, in terms of baking.   This is achieved through Maillard reactions caramelising residual sugars turning the loaf brown.   However re-heating the bread also means the starches are returned to gel state, thereby conferring a refreshed quality in the bread.   This is a feature common in cookery, and I could post an example such as warming through a baguette-style garlic bread wrapped in aluminium foil.   The bread is already baked, but warming it through makes it seem fresh again.   Obviously this is only short term, as the effect of re-heating is to dry the bread out more, which makes it seem staler, quicker, once it cools back down.

c) Baking rye is quite a complex issue, as rye is not dependent on a network of protein chains for its structure.   Instead fibrous matter known as pentosans knit together the starches to give the bread a working structure in which to house the gas from fermentation.   As the rye dough starts to tire, near proof end, and in the early baking cycle, these pentosans tend to become very delicate indeed.   This is one reason why sourdough is so popular with rye, as the acid helps give greater stability to the structure at this late stage.

d) There are loads of posts all over this site about this, and Debra Wink has posted much on sourdough which ranks with any research found elsewhere.   Basically, bakers' yeast is derived from a single yeast source, namely Saccharomyces cerevisiae.   This is used as it ferments the sugars in flour quickly and produces the most carbon dioxide in this rapid time.   Time being money to the large bread operators; this is key.   And adding more and more bakers yeast speeds up the process still further.   Sourdough yeast cultures are created by allowing a mix of flour and water to start fermenting naturally, as there are natural yeasts present in flour.   Rye flour is a particularly fine source of microflora, wholegrain flours are better than white, organic better than conventional, that is in terms of anticipated natural yeasts found.   Once these wild yeasts begin to work, they multiply through a feeding regime aloowing the culture to become strong.   Long and complex feremtation sees the developments of both lactic and acetic bacteria in the magic mix of the sour dough.   Creating a balance of these acids and wild yeast is the key to successful sourdough baking.   Saccharomyces cerevisiae is generally not an important yeast in the sourdough mix, as it does not like the higher acidity created in the sourdough, necessary for the bacterial fermentation.   Successful raising of bread using natural leaven is a time consuming and rewarding task for those of us seeking to produce this type of bread.   As I say it is quite complex, and there are academic papers in abundance on the subject if you want to do any research.

e)   Adding more water is probably essential to the type of bread you are calling par-baked.   I've already indicated that the method has to drive more water from the baking bread than conventional baking.   It is baked at lower temperature first time round, so the oven is cooler, so the bread is in the oven longer than is absolutely necessary.   Then the second bake, and the bread has to be returned to high temperatures in order to complete the caramelisation.   Again, the bread will dry out further as it passes to the higher temperature.

I hope these go some way to answering your questions

Best wishes

Andy 

Since small consumption of bread in my family I would like to bake once avery two weeks and freeze par-bread for later re-heating. Thank you in advance

I'm not sure that's such a good idea, Barmaley, unless you have equipment which will flash-freeze the parbaked bread.  

Why not just bake, then immediately freeze the baked bread once it has cooled?  Wrapping it in food-film, then placing it in a freezer bag works very well.

Allow it to thaw naturally (avoid using a microwave to thaw it), then unwrap and enjoy.

Freezing is more cost effective as well,  since you only need to preheat your oven once: the day you bake.