Bread Fermentation

8/9/2019 Bread Fermentation

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Bread Fermentation


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Introduction

History

Bread being one of the earliest processedfood

Manufacturing industry from 3,000 B.C.E. inEgypt

$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


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Bread Fermentation

The fermentation occurs during bread

manufacturing is different from most other

food fermentations Purpose

Fermentation end products


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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 andelasticity and essential doe the leavening

process Poorly formed or absent in non-wheat flours

Most commercial breads contain some wheat


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Protein

Gliadin and glutenin the most important ones,~85%

When hydrated and mixed, form gluten, keycomponent of bread

Remaining globulins and albumins, E- and F-amylases


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Carbohydrate

75% of the total weight

Largely compose of starch

Native starch granule insoluble

Amylose and amylopectin within sphericcal granulesin rigid, semi-crystalline network

Milling can damage a small percentage, increasewater absorption and enzyme exposure

Some other carbohydrates

A small amount of simple sugar, cellulose,fiber (~1%)


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Yeast Cultures

S. cerevisiae, or bakers yeast

Properties and characteristics for breadmaking

Gassing power

Flavor development

Stable to drying

Stable during storage

Easy to dispense

Ethanol

cryotolerant


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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


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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


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General Manufacturing Principles

Weigh and mixingredients

dough Fermenteddough

Portionedand

shapedbake Cool

slice pack

fermentation

fermentation


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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


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Fermentation

Lag phase usually

Bakers yeast facultative metabolism (Fig.8-6)

Aerobic (via TCA cycle)

Anaerobic glycolytic fermentation pathway

Glucose inhibit TCA enzymes

CO2


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Sugar metabolism by bakers yeast

Carbohydrate sources Starch

Sugars (glucose and maltose)

Transport and utilization Sequential use

Regulation-glucose represses enzymes involved inmaltose transportation

Maltose represses invertase expression

Mutants available

Sugar transport (Fig 8-7)

Glycolysis


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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 microbailcontamination, and maintain yeast activity

Relative humidity 70-80%


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Glucose

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1, 6 phosphate

DGAPDihydroxyacetone

PGALGlyceraldehyde

3-phosphate

PEPPhosphenopyruvate

Pyruvate

Oxaloacetate

Respiration Chain

TCA Cycle

CO2

CO2Lactic acid Acetyl CoA

+36 ATP

Ethanol

CO2+2 ATP

+2 ATP


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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 thenmixing with the remaining ingredients

Liquid sponge process Continuous bread-making, liquid sponge, save

labor and time, using thin, quality not as good

Chorleywood Process


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Microbiology of breadmaking

Conventional breadmaking

S. cerevisiae

Bacteria

Commercial bakers yeast about 5% contaminating

lactic acid bacteria

If LAB deliberated added, can lower pH tobelow 4.0 and cause distinctive sour but

appealing flavor, better preserved


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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 kruseidominant


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Sour Dough Bread

The San Francisco sourdough Frenchbread

Use start culture or mother-sponge

Occurred in San Francisco, continuously usedfor over 140 years

Ecosystem consists of on species of yeast andone species of bacteria

Occurred in a ratio of 1:100 Yeast- Candida milleri(or Torulopsis holmii)

Bacteria- Lb. sanfrancisco


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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 water 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

Documents

Bread Fermentation