Function of oxygen in dough

There is a misconception that yeast needs oxygen to work well producing gas  to raise the dough. Actually it does not need oxygen present, since yeast is capable of feeding on sugars either aerobically (with oxygen) or non-aerobically (absence of oxygen). It is true that the yeast likes to feed for the early stages when there is oxygen present, when it adopts a feeding position called respiration. The oxygen is plentiful at the start of bulk fermentation because the process of kneading will incorporate oxygen in the dough by the thrusting of folding motion. However, within the first hour the respiring yeast will use up that oxygen, and then it adopts the fermentation feeding position, when its enzymes change the starch sugars to glucose, and as it feeds on the glucose it makes more gas and alcohol than it was when it was respiring at the early stage. Actually, yeast is remarkable for its ability to feed in an environment both with and without oxygen. During the early stage of dough life the yeast is keen to gather and store the oxygen since oxygen is essential for it to maintain health and have the ability to both grow and reproduce. That is why in a yeast factory where the object is to make tons of yeast, oxygen is bubbled into the huge fermentation tanks. But in dough, on the other hand, the object is to generate gas for puffing the dough, and fermentation without oxygen will see to that.

Bakers should be warned that long kneading involving the incorporation of much oxygen leads to bleaching of the flour. Craft bakers are not obsessed with whiteness like the industrial bakers have been, and craft bakers need to know that the bleaching effect of the oxygen is damaging the carotene pigment in the flour ( from which it gets its creaminess). Lodged in the carotene is not just colour but also compounds that create some of the attractive flavours of baked wheat, hence it is a real depletion of the bread to destroy the carotene. Further, more oxygen is incorporated into dough at higher temperatures, so this is clearly a call to dough makers to avoid making warm dough. Cooler doughs will not only retain more carotene, but they also have far better structure and gluten.

Another area where the of the presence of oxygen has a  significant effect is the making of gluten. Free and available oxygen is drawn into the emerging gluten matrix as a necessary component, and there must be sufficient quantities of it to make high quality gluten. Although the yeast depletes the oxygen in the early stage of fermentation, the baker’s method of “folding” the dough will continue to incorporate oxygen for the gluten making.

Discussing the oxygenation of dough is not to create confusion with the oxidation of flour, which refers to the satisfactory aging of flour. During the aging of flour the proteins are oxidised and that has the effect of creating better gluten strands, giving better volume to the bread and less stickiness when working the mature dough on the bench. Craft bakers used to ensure that they had proper storage facilities to be able to age the white flour for several months of oxidation since the miller was unable to store it for long. (In times past businesses were happier to keep capital tied up in stock than they are today).

The aging of flour poses a dilemma for bakers who prefer to work with stonegrounf flour – those bakers seeking to offer the more nutritious product, since stoneground flour retains vitamins and minerals from the both the germ oil and the aleurone layer. As the oxidising of the protein occurs during aging, so too will the vitamins be  oxidising, leading to their goodness being leached away. I work often with stoneground flour at Cann Mills, and my compromise is to age it for only 3 – 4 weeks.

 

 

 

Here is an excerpt from my note about poolish that is handed out to PANARY students when they attend a course which has used this type of sponge in one or two of the breads on the programme.

POOLISH

This is the French term for a type of pre-fermentation that forms a portion of the dough into which it is incorporated many hours later or, possibly, the next day. It belongs in the category of the large family of what we call in English “sponges” and “ferments”, and some would call it a “starter ”.

One of its distinctive features is that it is a fairly liquid fermented culture, and in modern baking is usually made with equal amounts of flour and water. It is leavened with factory-made baker’s yeast, and is prepared with part of the main dough’s flour and water. The rest of the dough’s flour, water, salt, and yeast are added at dough-making time. Its flour as a proportion of total flour ranges from 15% – 50%.

In large commercial quantities, in the ambient warmth of a bakery, if the poolish is set to mature slowly over 8-10 hours or more, the amount of yeast added is miniscule, being only 0.1%, which is one gram of yeast to each kilogram of flour. Household bakers could use a little more. When I prepare a tiny poolish at night for a small dough in the morning I describe the amount of fresh yeast used as being the size of a green pea. If conditions were cold, or it was going to sit for less than 8 hours, enlarge the green pea to a marrow-fat pea. With dried yeast, it is only a pinch, denoting an eighth or a tenth of a teaspoon.

As a preliminary fermentation its function in breadmaking is to bestow benefits on the final dough. The benefits are many: flavour, moisture retention, and the creation of the open structure with large and randomly distributed gas bubbles so peculiar to the continental style of breads. Hence it is commonly associated with the baguette. The Parisian baguette was developed as bakers copied the remarkable and innovative pastry and bread methods of Vienna. These innovations occurred in the mid-nineteenth century, probably in the late 1840’s, just before fresh baker’s yeast (saccharomyces cerevisiae) began to be made in factories. At that time, when bread bakers still obtained their yeast from beer brewers (also saccharomyces cerevisiae) a shortage of yeast occurred when many brewers were changing from top-fermenting tanks to bottom-fermenting. Collection of yeast froth is easy from top-fermenters, but difficult from the bottom fermenting types of beer.

The sponge method certainly makes a small amount of initial yeast go further. For a short period the style and skills of Polish bakers must have influenced the Austrians. We assume the Poles’ technique became known as the poolish. Its sparse use of yeast would have continued to be attractive to the bakers of the 1850’s when compressed yeast remained scarce and expensive, being a new product.

A poolish must be set to work at room temperature for at least 3 – 8 hours before it is added to a dough, possibly 12 – 15 hours if conditions are cool. On the other hand, if conditions are warm, after 3 – 4 hours it would be wise to put it in a refrigerator. Although it starts with only a small amount of yeast it gets surprisingly active at room temperature because after about 5 hours those yeast cells start to reproduce. They will continue to multiply while they have food. (In any type of dough or sponge yeast will begin to reproduce after some 4 to 6 hours). After its long fermentation period the poolish will be classed as mature and ready for use because by then the feeding yeast will have created acids and by-products from their fermentation activity, and these will greatly enhance the dough that receives the poolish. More yeast has to be used if it is expected to reach maturity in a shorter time, such as 4 – 5 hours. There will be more flavour in the final bread, the crumb will be porous and open while giving a satisfactory chewiness, and the bread will retain its moisture for longer – meaning it is slower to stale.

The appearance of it when ripe reveals many bubbles on its surface, with the gas bubbles looking as though they are pushing upwards to burst. It is classed as over-ripe if it has begun to sink or settle down, and is no longer appearing to be moving upward. When over-ripe it may reveal around the sides of its storage vessel a line indicating the “high-tide” level that it had reached before sinking or collapsing.

Suggested poolish:

500 gm breadmaking white flour

500 ml water

½-1 gm fresh yeast ( ⅛-¼ teaspoon dried yeast)

Mix until a loose, batter-like dough is formed, with no dry patches.

Cover the bowl you have mixed it in, and put it aside in a quiet place for it to ferment for 8 to 12 hours.

That’s it. I hope you enjoy working with sponges and tinkering with poolish in particular. Good baking, Paul

Making good buns
Here are some general tips for making memorable buns.

Be generous with all the enriching ingredients: an extra egg; 10-15% more butter than normal; 20% more fruit (currants, sultanas, etc.; a little extra spice. [Remember – adding egg and butter may mean you have to call up a little more flour].

Spices: you are rewarded if you grind them on the baking day, everything is so zingy and flavoursome. In my bakery I would ask all staff to put in an extra hour right before bun season, and out would come the old coffee grinders. There would ensue a frenzy of grinding and sieving, followed by re-grinding of the coarse bits caught in the sieves . Gradually a huge mound of freshly ground spices would rise on a large sheet of brown paper on the work table. About two kilos or more.

Here’s my favourite blend: allspice and cloves are the hotties, and when eating the bun they hit the tongue and the front of the mouth! Be careful not to overdo them…

nutmeg, cinnamon, & cumin are the sweeter and more gentle ones, and they comprise the bulk of the mix

a little more depth and warmth? add ground ginger

Ferment your dough as for normal buns, remembering that with such a rich and spiced dough it is best to watch that the first rise achieves less puffiness than a normal bread dough. For such rich doughs I would always make a ferment (in the English baker’s lexicon a ferment = wet sponge, highly yeasted).

Crossing. See the photo at the top. Keep the piping nozzle well above the buns as you swish along. The buns must be placed on the trays in neat rows to enable accurate piping.

The Piping Mix. It should be runny, like a batter that falls easily from the whisk when it is raised above the mix. Don’t select a wide nozzle, but it should not be too thin. The nozzle I like to use is 4mm. The runny mix and the width of nozzle means that you should only need to squeeze the piping bag gently to have it streaming out. Here’s the mix:

100 gm bread flour

100 gm plain flour

Rub into the flours half a tablespoon of veg oil

450-500 ml water

Beat with a whisk into a smooth batter

Red dyed eggs for Greek Easter plaits (tsoureki)
A rich burgundy red, these dyed eggs are sunk into easily expanded gaps between the strands of the enriched 3-strand plait that is the normal style of this bread.

The photo below shows them ready for final proving, each plait getting one egg, but you can insert two or three into the plait if you like. The dyed eggs have to be inserted fairly deeply to avoid them exploding in the oven.

Here is the recipe for the dye, a simple and natural affair that you would find cloth and wool dyers have used for millenia. In the kitchen save your onion skins for a week or two.

TO MAKE RED EGGS

12 uncooked eggs

skins from 15 Spanish onions (brown)

2 tabspns white vinegar

4½ cups water

Put skins, vinegar and water in a saucepan, bring to boil, simmer for 30 minutes. It will look orange.

Strain into a glass/ceramic bowl (plastic gets stained)

In a stainless steel pan, add cooled, strained dye and the eggs – in one layer totally covered by dye.

Boil over medium heat, cover and simmer 12-15 minutes to redden the eggs. Take out the eggs with a slotted spoon.

When the eggs are dry gently coat them with veg oil. One way to do this would be to rub them with an oil-soaked piece of kitchen paper.