Cereal processing Flashcards
What is the chemical change in bread?
Foam to sponge
What does flour contain?
Protein, undamaged and damaged starch
What is the importance of damaged starch and amylase activity?
Support yeast activity
Why is high alpha amylase content bad?
Converted to dextrin-like substances causes low WHC and weak and sticky crumb
What is the main yeast used in bread?
Saccharomyces cerevisiae
What is the role of water?
Dispersion, hydration, gluten formation and gelatinisation
What is water taken up by?
Protein
Starch (damaged takes up more)
Fibrous components
What is the role of salt in bread?
Flavour
Preservation
Fermentation control
Gluten interactions
How does salt effect gluten?
Less salt makes gluten harder to process
What is the role of sugar in bread?
Yeast fermentation
Crust colour
What is the role of oxidising agents (ascorbic acid) in bread manufacture?
Increase protein cross-links, shorten mixing time and improves gas retention
What is the role of reducing agents (cysteine) in bread manufacture?
Break disulphide bonds and weaken structure
What is the role of surfactants in bread manufacture?
Improve dough stability
Role of fat in bread manufacture?
Improves volume, texture and slicing
Why is soya sometimes used in bread making?
Enzyme active with oxidising effect
Which process is fat used in?
Chorleywood process
What occurs during mixing of bread?
Glutenin and gliadin proteins hydrate to form gluten and gas cells
What does kneading do in bread manufacture?
Unfolding and cross-linking of proteins
How does bread dough resemble a foam?
Bubbles become trapped in a gluten network
What occurs during proving?
Glucose and fructose are fermented to CO2 and alcohol to inflate gas cells
What occurs during bread baking?
Increase gas production
Gluten is denatured and coagulated
Transition to sponge (92-96C)
How does bread become a sponge?
Cells interconnect and liquid moves through matrix
What are the 2 types of bread manufacture?
Bulk fermentation process (fermentation)
Chorley bread process (no fermentation)
Why is Chorley bread process the preferred method?
No resting and no emulsifier needed
What is the chemical structure of cake?
o/w emulsion with air bubbles in fat phase
What is the role of flour in cake batter?
Prevent fat or air cell coalescence
What occurs to flour during baking?
Starch granules imbibe, swell and gelatinise
What are the leavening agents used in baking?
Alkali
Acid
What does egg do in cake batter?
Yolk stabilises o/w emulsion and white stabilises air cells
What causes foam to sponge transition?
Egg protein gelation and denaturation of protein network
What is the role of fat in cake batter?
Air cell stabilisation
What occurs to fat as cake is baked?
Disperses through aqueous phase and can prevent moisture loss
What is the role of sugar in cakes?
Breaks down fat crystals causing air stabilisation
Delays gelatinisation (allows time for aeration)
How does sugar prevent gluten formation in cakes?
Competes for water and enhances protein denaturation
How does rising occur in puff pastry?
Layers trapping water vapour
What occurs during baking of puff pastry?
Water converted to steam
Fat behaves as barrier to prevent escape
Steam causes layers to separate and lift
Melted fat gives soft texture
What are the processes in biscuit manufacture?
Ferment
Laminate
Sheet and cut
Moulded
Extruded
What are the types of biscuit?
Hard developed
Short doughs
Characteristics of hard developed doughs
High water (loss)
Less enriched
Gluten
Dissolved sugar
Shrink
Characteristics of short doughs
Low water
Enriched
Not dissolved sugar
No gluten
Thick matrix
