lec 6 bread and baking technology Flashcards

Question

what do the Wheat cell wall polysaccharides contain?

Answer 1

Pentosans (e.g. arabinoxylan), β-glucan (low solubility in wheat) etc

Answer 2

after oxidation.

Answer 3

Amylose and Amylopectin

Answer 4

mainly linear

Answer 5

branched polysaccharide

Answer 6

Gelatinization is the swelling and bursting of starch granules when they are heated in the presence of water.

Answer 7

they Leach from granules

Answer 8

Limited leaching – remain in granule remnants

Answer 9

Retrogradation refers to the process in which the gelatinized starch molecules, which have been dispersed in a solution during heating, reassociate and rearrange themselves into a more ordered structure upon cooling. It is essentially the opposite of gelatinization. Reassociation of starch molecules: As the gelatinized starch solution cools, the amylose and amylopectin molecules begin to realign and reassociate with each other. This reassociation results in the formation of a more ordered and crystalline structure. Water expulsion: As the starch molecules reassociate, they expel water molecules from the gel network. This leads to the formation of tighter bonds between starch molecules and contributes to the thickening and firming of the gel. Texture changes: The retrogradation process leads to changes in the texture of starch-containing foods. For example, retrogradation contributes to the firming of cooked pasta and the staling of bread. In desserts and other products thickened with gelatinized starch, retrogradation can lead to the formation of a firmer and sometimes gritty texture over time.

Answer 10

Syneresis is the process in which a gel or gel-like substance expels liquid, usually water, and contracts or shrinks. This expulsion of liquid occurs after gel formation, typically during storage or when the gel is subjected to mechanical stress

Answer 11

– Starts within minutes after baking – completed within 48h – Gives syneresis

Answer 12

– Starts several hours after baking – completed within 2 weeks – Contributes to bread staling

Answer 13

Gelatinization occurs upon heating in the presence of water

Answer 14

– Granule swelling starts at approx. 45 °C – Amylose leaches from granules

Answer 15

at approx. 62-64 °C

Answer 16

polymers align (may gel upon cooling)

Answer 17

Gelatinization is followed by retrogradation (i.e. recrystallization) of starch polymers

Answer 18

dextrins and sugars

Answer 19

– Decrease in viscosity – ‘Falling number’: α-amylase activity in a flour – Blending of flours --> gives constant ‘Falling number’ The falling number test measures the time it takes for a plunger to fall through a heated and stirred flour-water slurry. This time is inversely related to the α-amylase activity in the flour. Higher α-amylase activity results in faster starch degradation and a lower falling number, while lower α-amylase activity leads to slower starch degradation and a higher falling number. The falling number is an important parameter for assessing flour quality and predicting its performance in baking processes.

Answer 20

Damaged starch Starch Protein Pentosans/Cell wall PS

Answer 21

Development in dough rheology during hydration and mixing * Gluten – Physical ‘cross-linking’ * Hydrophobicity and H-bonding – S-S cross-linking – Interaction with water and other dough components Dough Rheology: Dough should become smoother and cohesive during mixing, with even water distribution and changes in elasticity and viscosity indicating gluten development. Gluten Formation: Proper mixing aligns and bonds gluten proteins, creating a continuous network crucial for texture and volume in baked goods. Hydrophobicity and H-Bonding: Hydrophobic interactions and hydrogen bonding between gluten proteins, along with S-S cross-linking, strengthen the gluten network during mixing. Interaction with Water: Water hydrates flour, initiating gluten formation, and interacts with other dough components to ensure uniform hydration and proper gluten development

Answer 22

by decrease in surface tension – Proteins and polar lipids – Bubbles initially covered by proteins – forms stiff surface layer – Upon expansion lipids play an increasingly important role – Viscosity of continuous phase important * Starch gelatinization * Pentosans/cell wall polysaccharides

Answer 23

* Yeast (Saccharomyces cerevisiae) – Uses approx. 3% of flour  CO2 and EtOH – Creates volume, porosity and aroma * Sour dough – Lactobacilli produce lactic and acetic acid

Answer 24

* Fermentation bubbles are retained as foam during proofing & baking * Bubble surface layer hardens * limits excessive growth of bubbles  even crumb structure * Baking heats and ́sets ́ the structure as a sponge by gelatinizing the starch * The crust forms on drying the starch gel below the glass transition temperature to form a solid, brittle layer

Answer 25

* Complex phenomenon of physico-chemical changes * Increased softness of crust * Increased firmness of crumb * Increased crumbliness * Increased whiteness * Loss of aroma and taste, development of ”stale” taste * Crumb softness recovered (to some extent) when bread is reheated

Answer 26

* Water migration from crumb to crust and between components in the bread * Changes in gluten * Starch retrogradation (Amylopectin, slow)

Answer 27

* Storage temperature – maximum staling at approx. 4-6°C * Control water content and distribution * Enzymes * Emulsifiers * Starch source and treatment * Starch composition * Starch-lipid complex formation

Answer 28

* Some polar lipids form inclusion complexes with amylose and longer amylopectin chains (monoglycerides, lyso-lecithin, fatty acids etc.) * Hydrophobic tail of emulsifier enters the apolar cavity of the amylose or amylopectin helices * Disturbs the recrystallization (retrogradation) of starch