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Bread Fermentation

Bread Fermentation. Introduction. History Bread being one of the earliest “processed” food Manufacturing “industry” from 3,000 B.C.E. in Egypt $16 billion industry in the US Wheat consumption ~100 Kg/person/year a central ago, 50 Kg 1960s, 70 Kg 1980s, 2000 65 Kg

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Bread Fermentation

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  1. Bread Fermentation

  2. Introduction • History • Bread being one of the earliest “processed” food • Manufacturing “industry” from 3,000 B.C.E. in Egypt • $16 billion industry in the US • Wheat consumption ~100 Kg/person/year a central ago, 50 Kg 1960s, 70 Kg 1980s, 2000 65 Kg • European as high as 140 Kg/person/year

  3. Bread Fermentation • The fermentation occurs during bread manufacturing is different from most other food fermentations • Purpose • Fermentation end products

  4. Wheat Chemistry and Milling • Most common starting material • Wheat • Other cereal grains such as rye, barley, oats, corn, etc. • Gluten • Protein complex gives bread structure and elasticity and essential doe the leavening process • Poorly formed or absent in non-wheat flours • Most commercial breads contain some wheat

  5. Wheat Chemistry and Milling • Flour composition critical for the fermentation and physical structure of the dough and finished bread • Refined white flour used mostly in US, from erdosperm portion • Consists mainly protein and starch • Small portion of heicellulose and lipid • Protein • 8%-15% of wheat flour is protein • High protein flours from hard wheat best for bread, >11% • Low-protein flours from soft wheat <9% for cakes, cookies, pastries

  6. Wheat Chemistry and Milling • Protein • Gliadin and glutenin the most important ones, ~85% • When hydrated and mixed, form gluten, key component of bread • Remaining globulins and albumins, - and -amylases

  7. Wheat Chemistry and Milling • Carbohydrate • 75% of the total weight • Largely compose of starch • Native starch granule insoluble • Amylose and amylopectin within sphericcal granules in rigid, semi-crystalline network • Milling can damage a small percentage, increase water absorption and enzyme exposure • Some other carbohydrates • A small amount of simple sugar, cellulose, fiber (~1%)

  8. Yeast Cultures • S. cerevisiae, or bakers’ yeast • Properties and characteristics for bread making • Gassing power • Flavor development • Stable to drying • Stable during storage • Easy to dispense • Ethanol • cryotolerant

  9. Yeast Cultures • Industrial production • Scale up (Fig. 8-4) • Growth medium • Molasses or another inexpensive source of sugar and various ammonium salts • Other yeast nutrients • Ammonium phosphate • Magnesium sulfate • Calcium sulfate, trace minerals (zinc, iron) • Cell mass production required conditions • O2 level • Temp (30C) • pH (4.0-5.0) • continuous

  10. Yeast cultures • Commercially available • Yeast cream • Used directly, highly perishable • Yeast cake • Yeast cream through filtration press or vac. filter • Refrigeration required, shelflife a few week • Metabolically active, quick fermentation • Dry active yeast • Home bread making, small business operation • Last 6 months or longer • Require hydration, not as active

  11. General Manufacturing Principles fermentation Weigh and mix ingredients Fermented dough dough fermentation Portioned and shaped bake Cool slice pack

  12. Ingredients • Key ingredients • Wheat flour 60-70%, protein and carbohydrate • Water 30-40%, solvent to hydrate flour and other indredients • Salt 1-2%, toughens the gluten, controls fermentation, gives flavor • Yeast 1-2%, leavening and flavor formation • Optional ingredients • Sugars 2-3%, fermentable, flavor, color • Enzymes • - and -amylases, supplement the low amount from original flour • Malt powder • Proteolytic enzymes-softer dough, reducing mixing time

  13. Ingredients • Optional ingredients • Fat-shortening • Yeast nutrients • Vitamins-flour enrichment with 4 B vitamins • Gough improvers • reducing agents, as cysterine, speed up mixing, weaken dough • Oxidating agents, as ascorbic acid, improve dough • Biological preservatives • Mold inhibitor: potassium acetate, sodium diacetate, sodium propionate, calcium propionate • Emulsifiers (dough conditioners)-mono- di-glycerides • Gluten • Added in certain cases to improve dough • Crop years with low prot. cont., whole wheat and specialty bread

  14. Fermentation • Lag phase usually • Bakers’ yeast facultative metabolism (Fig. 8-6) • Aerobic (via TCA cycle) • Anaerobic glycolytic fermentation pathway • Glucose inhibit TCA enzymes • CO2

  15. Sugar metabolism by bakers’ yeast • Carbohydrate sources • Starch • Sugars (glucose and maltose) • Transport and utilization • Sequential use • Regulation-glucose represses enzymes involved in maltose transportation • Maltose represses invertase expression • Mutants available • Sugar transport (Fig 8-7) • Glycolysis

  16. Fermentation • End products • CO2 • Other compounds • Various acids and organic compound by yeasts • By LAB • Flavor and rheology of the dough • Factors affecting growth • Temp-hold at 25-28C instead of the optimal growth temp 36-39C to minimize microbail contamination, and maintain yeast activity • Relative humidity 70-80%

  17. Oxaloacetate Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1, 6 phosphate PGAL Glyceraldehyde 3-phosphate DGAP Dihydroxyacetone PEP Phosphenopyruvate Pyruvate CO2 Lactic acid Acetyl CoA TCA Cycle +2 ATP CO2 Respiration Chain Ethanol +2 ATP CO2 +36 ATP

  18. Modern Bread Technology • Straight dough process (Fig 8-9) • Homemade, one-batch-at-a-time, not much by the baking industry • Sponge and dough process • Mostly used, using partially concentrated portion of dough-sponge to ferment, and then mixing with the remaining ingredients • Liquid sponge process • Continuous bread-making, liquid sponge, save labor and time, using thin, quality not as good • Chorleywood Process

  19. Microbiology of breadmaking • Conventional breadmaking • S. cerevisiae • Bacteria • Commercial baker’s yeast about 5% contaminating lactic acid bacteria • If LAB deliberated added, can lower pH to below 4.0 and cause distinctive sour but appealing flavor, better preserved

  20. Sour dough Bread • Sour dough rye bread • Most studied bacterial bread fermentation • Popular in Europe • Micro-organisms isolated from sour rye • Bacteria: Lb. plantarum, Lb. brevis, Lb. casei, Lb. fermenti, Lb. pastorianus, Lb. buchneri, Lb. leichmannii, Lb. acidophilus, Lb. farciminis, Lb. alimentarius, Lb. vrevis var. lindneri, Lb. fermentum, Lb. fructivarans, Pediococcus acidilactici • LAB with very high amino acid requirement dominant • Yeasts: Candida krusei, Saccharomyces cerevisiae, Pichia saitoi, Torulopsis holmii • Candida krusei dominant

  21. Sour Dough Bread • The San Francisco sourdough French bread • Use start culture or “mother-sponge” • Occurred in San Francisco, continuously used for over 140 years • Ecosystem consists of on species of yeast and one species of bacteria • Occurred in a ratio of 1:100 • Yeast- Candida milleri (or Torulopsis holmii) • Bacteria- Lb. sanfrancisco

  22. Formulations for San Francisco Sour Dough French Bread Starter-sponge Bread dough 100 parts of previous sponge 20 parts starter-sponge (40% of final mix) (11% of final mix) 100 parts flour (high-gluten) 100 parts flour (regular patent) 46-52 parts watrer 60 parts water 2 parts salt Starting pH 4.4-4.5 Starting pH 5.2-5.3 Final pH 3.8-3.9 Final pH 3.9-4.0

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