Alright, enough said. Flour, water and salt; it doesn't get simpler than that. Or does it? Bread is actually fascinating, and it's one of the most well-documented types of fermentation due to its popularity. There are SO many kinds out there, from the sourdough pictures above that I made to rustic rye bread in Iceland that's baked under geothermal vents. Most bread is leavened, i.e there is an agent that allows it to rise and traps gas within the dough, making the texture lighter. However, I am focusing specifically on naturally leavened bread, made with a starter. The fermentation of bread was originally a chance contamination of aerial yeasts, and the first documented leavening agent was in Egypt, where beer froth was used. However, for most breads after this period, the leavening agent was a piece of leftover dough with yeast already growing within, hence the term "backslapping". Bread represents the culinary domestication of grain, according to Harold McGee, as humans figured out how to make the humble grain more nutritious: release certain vitamins and minerals through the fermentation process, and cook the grains so that we can digest them through baking. According to a NCBI article, sourdough bread increases the presence of 118 bioavailable compounds, including BCAAs, phenolic acids and certain phytonutrients, and is thought to have a lower insulin response due to the digestion of certain sugar-conjugated acids and other macromolecules. Bread contains both alcoholic and lactic acid fermentation, but the yeasts, namely Saccharomyces Exiguus (not Cerevisiae surprisingly) is responsible for the majority of metabolic activity within the dough. The “starter” is a mix of flour and water which is left to ferment at room temperature, and which ambient yeasts feed off of. It is hard to keep different starters from “deteriorating” when bringing them into a new environment, as the changing microbial content affects the microflora. This is thought to be the reason why you can't bring San Fran starter culture to Chicago, as the environment is simply different. The best bread relies on slow fermentation, as yeast metabolization creates carbon dioxide gas, which becomes trapped in the matrix of gluten proteins that coagulate. It also unlocks flavor compounds and starts the saccharification process (starch is broken down into its constituents), where the bread tastes sweeter. If the yeast activity is prolonged at colder temperatures, the theory goes that it has more time to digest the starches in the flour and increase the presence of lactic acid within the dough. It is thought that starters that have been maintained for decades are resistant to contamination, as they are believed to have some antibiotic properties, like penicillium. Since the community of micro-organisms has been established for a long time, another plausible explanation is that the niche is more stable in its relationship with the yeasts and bacteria. C6H12O6 → 2C2H5OH + 2CO2. That's it effectively: glucose is broken down into carbon dioxide and alcohol. The yeast Cerevisiae has a preferential metabolism: single unit glucose and fructose monomers are the first to be consumed, via the flour, and then it switches to the disaccharide maltose, which is derived from the starch granules’ saccharification process through enzymes. Interestingly enough, Exiguus, the yeast in sourdough is unable to break down maltose, and it thrives in very acidic environments as opposed to Cerevisiae. The sour taste in bread is about 75% lactic acid, and 25% acetic acid, the majority of which is produced by the yeast, but some strains of bacteria are involved. They are all closely related, but not to any other known species; thus, they are called Lactobacillus sanfrancisco, and they function best at a temperature of 85˚F and a pH between 3.8 and 4.5. Yeast performs best at 95F, and it has a requirement of warm water (105˚ to 110˚F) for rehydration, as lower temperatures result in a loss of its fermentation power. Its behavior isn’t completely understood; it is thought that residual carbohydrates in the dry yeast cells must be reconstituted through cell membranes rapidly enough so that crucial cell contents are not lost to the solution. Added sugar also affects the yeast metabolism rate, increasing the rate of activity until it has an osmotic effect on the cells, releasing water and then retarding yeast concentrations. Thus, extra yeast is required in sweetened breads, because metabolic activity declines sharply due to osmosis, which is the same with added salt. Fermentation plays a crucial role in the strength of the dough, other than gas production: the acids are important for strengthening the gluten network, as they encourage coagulation so that the expansion of gas pockets within the dough during fermentation is retained. The gluten proteins stretch and become elastic through chemical interactions, and through the breakdown of proteins into amino acids, cross-linking gets promoted by the starter culture. The optimum rising temperature for bread during its bulk fermentation is only 80˚F: yeast multiply more rapidly at 95˚F, but they secrete by-products that deteriorate the quality of the bread. Yeast cells will die when the internal temperature reaches 140˚F, a crucial part of baking the bread because the yeast activity needs to be hyper stimulated during the initial baking time. When in a moist environment (i.e a steam oven), the yeast produces a ton of carbon dioxide, which causes the dough to inflate rapidly, per the term oven spring. If the bread over proofs or does not have enough tensile strength, the gas escapes and you end up with flat bread. If I included every single kind of bread in this blog, I'd be here forever. I'm not going to even attempt to make a general list, because each culture that predominantly grows grain or wheat for its staple crop has its own way of making grains more bioavailable. However, this is the first post in which I am including my recipe for what you can do with fermented foods! Obviously you can eat bread hot out of the oven, and it's delicious, but I wanted to make a tartine, a savory toast that relies on day-old bread. I topped it with roasted leeks and king oyster mushrooms, crispy fried Jerusalem Artichoke chips, and a yogurt espuma with harissa and preserved lemon (another fermented product I will make a post on later) that I produced using an iSi whip carbonator. Tartine of Roasted Leeks and King Oyster Mushroom, Crispy Jerusalem Artichoke, Harrissa + Preserved Lemon Yogurt EspumaIngredients:
Roasted Leeks and King Oyster Mushrooms: - 1 tbsp olive oil - smoked salt + black pepper, freshly ground - 4 leeks, washed and scrubbed, white parts only cut in half lengthwise - 3 king oyster mushrooms, halved and scored on the cut face Harissa and Preserved Lemon Yogurt Foam (Espuma): - 1 cup full fat plain yogurt - 2 tbsp homemade harissa paste - 1 tsp yuzu juice - 1-2 egg yolks, depending on how thick you want the emulsion - 1/2 tsp baharat spice mix - 1 tbsp lemon juice - 1 tsp preserved lemon brine - 1/2 tbsp pomegranate molasses - a few cracks of timut pepper Jerusalem Artichoke Chips: - 1 lb. Jerusalem artichokes, rinsed + mandolined, then soaked in cold salted water - 1 cup frying/vegetable oil - Chicken boullion powder - Smoked salt - Shichimi Togarashi For plating: - 2 slices sourdough or whatever kind of good fermented bread, toasted - Micro arugula Method: 1. For the espuma: combine all of the ingredients, and pour into the iSi whip. Charge with 1 canister, and place in the fridge to firm up for at least 30 min. 2. Meanwhile, preheat oven to 400˚F roast setting, and set up your frying station. Baste leeks and king oyster mushrooms with the oil, then place on a lined baking sheet and season with salt and pepper. 3. Roast for 15 minutes, then turn down the oven temperature to 350 and roast for another 15 minutes. 4. Meanwhile, pat dry the Jerusalem artichoke slices, and preheat your oil to 350˚F(a convenient way of telling if your oil is ready without the use of a thermometer is to start the oil cold with a scallion white; when the white is golden brown and the oil bubbles vigorously around it, you are ready to fry). Fry for about 7-8 minutes, or until golden brown and crispy. Remove from the oil and immediately season with the boullion, shichimi and salt. 5. To assemble: place a layer of the leeks roasted side up on the bread, then arrange the mushrooms on top depending on their size. Use the iSi whip to pipe a few mounds of espuma on top, then layer some of the chips on top. Decorate with the micro arugula and serve.
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