lecture 18 bread fermentation

Information about lecture 18 bread fermentation

Published on October 4, 2007

Author: Altoro

Source: authorstream.com

Content

Bread Fermentation:  Bread Fermentation Introduction:  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 Bread Fermentation:  Bread Fermentation The fermentation occurs during bread manufacturing is different from most other food fermentations Purpose Fermentation end products Wheat Chemistry and Milling:  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 Wheat Chemistry and Milling:  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 Wheat Chemistry and Milling:  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 Wheat Chemistry and Milling:  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%) Yeast Cultures:  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 Yeast Cultures:  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 Yeast cultures:  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 General Manufacturing Principles:  General Manufacturing Principles Weigh and mix ingredients dough Fermented dough Portioned and shaped bake Cool slice pack fermentation fermentation Ingredients:  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 Ingredients:  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 Fermentation:  Fermentation Lag phase usually Bakers’ yeast facultative metabolism (Fig. 8-6) Aerobic (via TCA cycle) Anaerobic glycolytic fermentation pathway Glucose inhibit TCA enzymes CO2 Sugar metabolism by bakers’ yeast:  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 Fermentation:  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% Slide17:  Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1, 6 phosphate DGAP Dihydroxyacetone PGAL Glyceraldehyde 3-phosphate PEP Phosphenopyruvate Pyruvate Respiration Chain TCA Cycle CO2 CO2 Lactic acid Acetyl CoA +36 ATP Ethanol CO2 +2 ATP +2 ATP Modern Bread Technology:  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 Microbiology of breadmaking:  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 Sour dough Bread:  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 Sour Dough Bread:  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 Formulations for San Francisco Sour Dough French Bread:  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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