BREAD

BREAD

Cereals provide Bread Cereals are the World’s staple Provide the majority of carbohydrates as

starch for the world’s population Members of the grass family

Wheat Rice Maize Oat, Rye Barley, Sorghum

How are they used? Direct consumption

Rice, Maize, Oats

Milled for flour Wheat, Rice, Maize, Rye

Milled for starch Maize, wheat, rice

Fermentation substrate Barley, Wheat, Rye, Rice, Maize

Milling

Grains crushed by a series of rollers Remove hull and bran Remove germ (embryo) Pulverise endosperm

Wholemeal flour Contains bran & embryo Higher lipid content, rancidity problem

Mills 8,000 BC first grain crops, hand crushing 1,500 BC Millstones 1,000 BC animal powered mills 400 BC watermills 1,000 windmills 1780 steam power 1870 use of steel rollers

Flour Carbohydrate

Bulk of endosperm, in intact starch granules Protein

Endosperm storage proteins Wheat 13% protein Glutenin & Gliadin

Lipid Mostly removed with embryo

Types of Flour Strong flour

From hard wheat High protein content For bread

Soft flour From soft wheats Lower protein content For cakes & biscuits

Bread Dough formation

Mixture of flour & water Water uptake depends on protein content

Kneading Developing gluten

Leavening Generation of gas to expand dough

Baking

Straight Dough Flour & water mixture

Yeast, leavening agent Sugar for yeast growth Salt for yeast metabolism Fat to soften texture, reduce staling.

• Saturated fats better• 5% in bread 30-50% in cakes

Milk to improve crumb texture Kneading to mix thoroughly Develop elastic gluten network

Proofing Incubate 30°C 1 to 2h

Yeast fermentation Production of ethanol & CO2

Gas expands dough Elastic dough will stretch

Punching, allows some CO2 to escape

Moulding & shaping

Cake All-purpose Strong bread

Alternative leavening agents Baking powder

Acid + alkali mix Cream of tartar & baking soda Produces CO2 when heated

Mechanical Beating or creaming to whip in air Steam generation Whipped egg white

Baking 250 – 300°C, 30 – 60 min

Further gas generation Dough rises to final shape Yeast killed off Starch gelatinises Gluten coagulates Bread becomes hard Crust develops and browns

Sponge Dough

Moderately stiff dough Only 50 % of the flour + yeast & sugar Fermented 3 –4 hours Remaining flour, fats & water added Finer texture, smaller gas holes

Batter whipped process

Chorleywood Process Continuous production

Liquid fermentation with little flour Remaining flour added Agitated to incorporate air Extruded into baking pans Fine uniform texture

Starch Starch, main polysaccharide in flour Present in starch granules Contains 2 polysaccarides

Amylose & amylopectin As heat increases

Starch granules absorb water & swell Release amylose from granule

On cooling Amylose molecules combine to form gel

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Maize starch

Starch Retrogradation

Realignment of amylose chains Stick to each other more strongly Forms more rigid crystalline structure Slow process so takes time Inhibited by fats that can interact with amylose Starch becomes harder

Staling

Stale bread = old bread Harder texture Crumb more brittle Dryer, poor release of flavour Promoted by low temperature

Regeneration possible by wet heat

Bread deterioration

Prone to fungal contamination Fungal growth normally prevented in foods by

low humidity and temperature Dry storage at low temp. promotes staling Added mould inhibitors common Eg. Calcium propionate