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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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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 fermentation3
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 milling5
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 milling6
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 milling7
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 cultures9
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 cultures10
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

fermentation

Weigh and mix

ingredients

Fermented

dough

dough

fermentation

Portioned

and

shaped

bake

Cool

slice

pack

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
ingredients13
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
fermentation16
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

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

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 bread21
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