effects of ascorbic acid on flour proteins / enzyme activity in bread dough
TRANSCRIPT
Effects of Ascorbic Acid on Flour Proteins /
Enzyme Activity in Bread Dough
Date: 15th April 2014
Presented by:
Ritesh Bhagea, Rouksaar Buctowar, Keshavi Ghoorbin,
Christabelle Cécile, Huda Nazeer
Overview
● Aims and Objectives
● Introduction
● Materials used
● Methodology
● Observation
● Results
● Discussion
● Problems
● Improvements
● Conclusion
● References
Aims and Objectives
1. To measure the height of dough every 10 minutes
over a period of one hour.
2. To discuss on the difference in dough height using
two different flours.
3. To compare the treatment ascorbic acid and the
control on the effect of yeast on dough
development.
Introduction
Bread and Bread-Making:
● Made by mixing water, flour, salt and yeast
● Basic food worldwide
● E.g: Wholemeal bread =
o Fat, vegetable protein
o Carbohydrate
o Rich in fibre, minerals, iron
o Vitamin E, B and B3
o Source of energy for growth
Importance of Yeast
● It provides the CO2 needed in order for the dough to
expand
● It strengthens bread dough
● During fermentation, yeast provides the metabolites
necessary for the characteristic flavour of bread
Bread = Flour
● Flour may come from:
o wheat flour
o spelt flour
o oatmeal
● Flour proteins: albumins,
globulins, gliadins and
glutenins
● Different types of bread
o Anadama bread
o Baguette
o Brioche
o Brown bread
Harder wheat -> high gluten -> High protein -> Hard & Strong flour
Flour Treatment Agents
● Additives that help improve baking by:
o increasing rate of dough rising
o improve strength and workability of dough
● Types:
o bleaching agents - make flour whiter, help gluten
development
o oxidizing agents - help gluten development
o reducing agents - help weaken flour
o enzymes - additional enzymes produce faster & more
complete reaction, eg: amylases, proteases
o emulsifiers - enhanced volume, softer crumb structure and
longer shelf-life
Enzyme Activity
● Long ago, potassium bromate was used - (side effects)
● Now, for decades enzymes are being used in bread-
making
● Flour consists of
o gluten, starch, non-starch polysaccharides, lipids, trace
amounts of minerals
● Production of dough = start of fermentation
● Enzymes act on gluten, starch and polysaccharides
● Enzymes process sugars and components
Enzyme Activity
Distilled water Measuring cylinder Yeast
Blédor flour Ascorbic Acid Moulin de la
Concorde flour
Materials
Methodology
● Measured:
- 1 g of yeast + 1 g of ascorbic
acid + 75 g Blédor flour
- 1 g of yeast + 1 g of ascorbic
acid + 75 g Moulin de la
Concorde flour
- 50ml of water (twice) in
measuring cylinder
Methodology
For both flour brands:
● 50 ml of water was poured
in a beaker
● Followed by yeast - mixed
with a rod
● Flour was added to the
ascorbic acid
● Then added to the beaker
containing water + yeast
Addition of
yeast to water
Addition of
flour to
ascorbic acid
Methodology
● Mixed well
● The dough was rolled into a
sausage shape
● Placed in a 250 ml measuring
cylinder
● Height recorded every 10
mins over a 1hr period
Dough was well mixed -
some flour was
sprinkled on the palms
of the hands to avoid
sticking
Observation
t = 0 min t = 60 mins
Observation
Carbon dioxide
formation
Results for Ascorbic Acid Treatment
Height of dough for each flour / cm
Time after:
(minutes)
Moulin de la
ConcordeBledor
0 10.3 10
10 10.4 10.3
20 12.0 11.1
30 14.0 13.5
40 16.0 15.5
50 18.3 17.2
60 19.2 18.3
Table 2: Height of dough for the flours under ascorbic acid
treatment during a 1 hour period
Results for Control
Height of dough for each flour / cm
Time after:
(minutes)
Moulin de la
ConcordeBledor
0 12.8 13.2
10 14.0 13.8
20 18.2 16.6
30 22.0 22.6
40 24.6 24.0
50 25.6 25.0
60 26.4 25.5
Table 3: Height of dough for the flours under no treatment
during a 1 hour period
Results
Figure 1: Graph showing rate of
dough rise for ascorbic acid
treatment v/s time
Figure 2: Graph showing rate of
dough rise for control v/s time
Results
Figure 3: Graph of rate of dough
rise in Moulin flour for ascorbic
acid treatment & control v/s time
Figure 4: Graph of rate of dough
rise in Bledor flour for ascorbic acid
treatment & control v/s time
Results
● Comparing flours for ascorbic acid treatment:
Percentage increase:
Moulin: (19.2 - 10.3) /10.3 * 100 = 86.4 %
Bledor: (18.3 - 10.0) /10.0 * 100 = 83.0 %
● Comparing flours for control:
Percentage increase:
Moulin: (26.4 - 12.8) / 12.8 * 100 = 106.3 %
Bledor: (25.5 - 13.2) / 13.2 * 100 = 93.2 %
Percentage Increase =
(Final reading - Initial reading) /
Initial reading * 100
Comments & Discussion
From our experiment and Table 4, we observed that:
● LMLC flour = better choice compared to Blédor flour - better rise.
● Ascorbic acid treatment did not help in dough development.
● In fact, it hindered dough development - control doubled in volume.
● While, ascorbic acid should have helped in rising of dough to give a
higher percentage increase.
● This probably happened due to experimental errors.
Percentage Increase (%)
Flour Brand Ascorbic Acid Control
Moulin 86.4 106.3
Blédor 83.0 93.2
Table 4: Percentage increase of dough for different flours and treatments
Ascorbic Acid
● Aka E300 or vitamin C
● A flour ‘improver’ or dough conditioner
● In presence of oxygen, acts as an oxidising agent:
o Strengthened gluten
o Greater loaf volume
o Finer crumb (more even cells/bubbles)
o Increased tenderness of the crumb
o Reduced crust thickness
o Faster rising
● Overall, improves gas retaining to give an impression of
freshness to consumers
How Ascorbic Acid Works
● Ascorbic acid (AA) is a reducing agent
● In flour, enzyme ascorbic acid oxidase present which
o catalyses the conversion of AA into dehydroascorbic acid
(DHAA) - oxidised form
● DHAA converts glutathione (GSH), a tripeptide found in
flour
o into its dimer, GSSG
o GSH can form disulfide bonds unlike GSSG
● Normally disulfide bridges form between gluten proteins
o GSH removed to keep bonds safe from disruption
● Disulfide bonds formed in the gluten structure enables the
dough to retain carbon dioxide produced by the yeast
Problems With the Experiment
● Level of dough was not uniform, hence took time to
‘stabilize’ the corners, then rise uniformly
● The AC being on, affected the results,
due to low temperature which decreases
enzyme activity
● Dough might not have been well mixed &
sticked to hands while mixing
● Did not roll both doughs simultaneously
● Parallax error while taking the height of dough
Improving the Experiment
● “Tap” doughs well to ensure uniformity throughout cylinders
● Turn off AC before experiment is started = room temperature
● Mix well and use more flour to avoid sticking to hands
● Take readings from three different ‘places’ and calculate mean to
reduce parallax error
● Same group of people doing both treatment and control - avoid
human errors
● Replication of experiment
● Start simultaneously and observe for a longer period of time
Conclusion
● Flour, salt, water, sugar and yeast are the basic
ingredients for bread production,
● Normally, ascorbic acid helps in the fabrication of
bread or rising of dough,
● However, in this experiment, it had the opposite
effect.
● Temperature and time lapse were the factors that
caused this effect and therefore need to be taken in
consideration.
References
1. http://static.guim.co.uk/sys-
images/Guardian/Pix/pictures/2008/02/12/wheat10a.jpg
2. http://www.valorsoja.com/wp-content/uploads/HarinaTrigoEspiga.jpg
3. http://www.baking-at-home.com/wp-content/uploads/2013/04/yeast-
540x262.jpg
4. http://photos1.blogger.com/blogger/4356/576/1600/pears5.jpg
5. http://slice.seriouseats.com/images/20110617-no-knead-bread-10.jpg
6. http://www.biokemi.org/biozoom/issues/516/articles/2309
7. http://www.finecooking.com/articles/yeast-role-bread-baking.aspx
8. http://en.wikipedia.org/wiki/Flour_treatment_agent
9. http://www.sustainweb.org/realbread/ascorbic_acid/
Thank You
For Your
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