الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Proteins have played a fundamental role in the structure and function of cells. Protein in the human diet is derived from two main
sources, namely animal proteins (e.g. egg-milk and fish) and plant
proteins (e.g. cereals, nuts beans, soy products. Novel sources of
food protein, such as from plants, algae and insects. Plant proteins
are good substitutes for meats or animal proteins. Although proteins
from legumes are not equal in quality with animal proteins, non
etheless. They can be an adequate substitute if they are eaten in
combination with other food.
The study was carried out in three parts:
Part (1): Study the chemical composition and functional properties
of algal protein isolates extract from brown algae.
Part (2): Effect of substitution non-fat dry milk (NFDM) with algal
protein isolates on ice milk quality.
Part (3): Effect of substitution of non-fat dry milk (NFDM) with algal
protein isolates on yoghurt quality made from cows milk.
Part (1): Study the chemical composition and functional
properties of algal protein isolate extracted
from brown algal:
The main objective of the present part was to determine the
chemical composition, of brown algae and algal protein isolates
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extracted from brown algae and to investigate the functional
properties of algal protein isolates extract from brown algal.
The obtained results could be summarized as follows:
1. Chemical composition of brown algae and algae protein isolate:
Moisture content of fresh samples were 87.7 and moisture
content of dried Taonia atomaria (brown algae) was 12.6 in
addition, crud protein, crude fiber, lipid, ash and total carbohydrates
contents were 16.0, 14.4, 2.1, 18.0 and 37.9%, respectively.
Meanwhile, the moisture content of algae protein isolates was
5.10%. moreover, the protein, crude fiber, lipids, ash and total
carbohydrates were 64.00, 1.26, 0.90 and 19.54%, respectively.
The mineral content of crude dried brown algae were 469.50,
187.54, 302.12, 397.81, 55.10, 469.52 and 111.52 for calcium,
potassium, magnesium, sodium, zinc, iron and manganese while there
values for algal protein isolates were 82.23, 58.47, 45.05, 102.79, 33.21,
376.33 and 53.25 mg / 100 gm, respectively.
It could be concluded that iron is major element in algae
protein isolates followed by sodium, calcium, potassium, manganese,
magnesium and zinc.
Amino acid composition of algal protein isolates revealed that
total essential amino acids was 16.61 g / 100 g algae protein isolate.
Among essential amino acids were leucine had the highest value,
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5.50 g / 100 g phenylalanine (4.13 g / 100 g), lysine (2.93 g / 100 g),
threonine (1.60 g / 100 g) and valine (1.62 g / 100 g) while isoleucin
had the lowest value (0.83 g / 100 g)
The total non essential amino acids content of algal protein
isolates was 27.09 g / 100 g. The amino acids were glutamic acid had
the highest value (8.93 g / 100 g) flowed by prolein (5.91), tyrosin
(3.44), aspartic acid (3.20), histidine (2.17) and the lowest value
arginine (0.44 g / 100 g).
Functional properties of algal protein isolate are very
important for process and production of most commercial food
products. These properties are those physico-chemical characteristics
which affect their behavior in food during preparation, processing,
storage and consumption. The present investigation was carried out
to study some important functional properties of algal protein
isolates including, foaming, emulsifying, water absorption capacity
and oil absorption capacity. The effect of some factors was studied
also such as heat treatment (72°C for 30 sec, 90°C for 15 sec and at
room temperature) and pH values.
1. Foaming capacity:
Foaming capacity of algal protein isolates preparations was the
lowest at pH 5.0 which is the nearest value to isoelectric point (IP)
of algal proteins. Also high heat treatment at 90°C for 15 sec. had
poor foaming properties of algae protein isolates.
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2. Foam volume satiability:
The higher heat treatment of algal protein isolates exhibited
the lowest value of foam volume stability than raw algae protein
isolate. At the alkaline side of pH (9, 11) foaming capacity stability
of algal protein isolate was the highest. While the lowest values were
observed at acidic side of pH (3 and 5).
Also the F.V.S of all treatments gradually decreased with
increasing the time of stability test. The lowest value of F.V.S of all
tested sample were recorded at 60 min. of the experiment.
Emulsifying properties:
The emulsion activity index (EAI) showed the lowest values at
pH 5.0 for all treatments while increasing of pH caused an increase
in EAI. Generally the EAI was higher in the case of high heat treated
and the lower in raw algal protein isolates. All values of EAI
gradually decreased after one day during storage (5 days).
Water and oil absorption capacities:
1. Water absorption capacity:
Water absorption capacity of algae protein isolates preparations
was obviously affected by heat treatment applied obtained results
indicated that high heat preparation (90°C / 15 sec.) exhibited the
highest values, while raw samples were the lowest.
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Water absorption capacity (WAC) increased when pH was
shifted towards alkaline side (pH 9, 11).
2. Oil absorption capacity:
The oil absorption capacity of algae protein isolate heated to
90°C for 15 sec. was higher than those of raw algal protein isolates
and algal protein isolates heated to 72°C for 30 sec.
Part (2): Effect of substitution non-fat dry milk (NFDM)
with algal protein isolate on ice milk quality:
Ice milk production has increased rapidly in the recent years in
many countries of the world. It is a delicious, wholesome, nutritious
frozen dairy food. The wide variation in the composition of ice milk
and related products makes it practically impossible to provied
nutritional date that will apply to all products.
Considering the short supply and high cost of milk solids used
for such product. Also the demand for functional foods is growing
rapidly all over the world due to the increased awareness of the
consumers on the impact of food on health (Stoon, 2002). The new
standard will allow formulaters to produce ice milk products with
excellent nutritional value and exceptional organoleptic properties at
lower cost. The study aimed to investigate the effect of partial
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replacement of non-fat dry milk with algal protein isolates on ice
milk quality.
The control formula contained 4% fat, 13% milk solids non fat,
17% sucrose, 0.7% stabilizer and 3% cocoa flavour. Three treatments
of mixes T1, T2 and T3 were prepared by substituting 10, 20 and 30%
of non-fat dry milk with algal protein isolates, respectively. The
prepared mixes were examined for chemical composition, acidity and
pH values, specific gravity and weight per gallon, viscosity, freezing
point and flow time. Resultant ice milk was tested for specific gravity,
weight per gallon, overrun, melting resistance and sensory evaluation.
All samples were stored for 10 weeks the experiment was triplicated.
The obtained results could be summarized as follows:
1. Replacement of non-fat dry milk with algal protein isolates in
making ice milk caused a significant increase in sp.gr and weight
per gallon, viscosity, flow time and freezing point.
2. Increasing the added algal protein isolates had no significant
differences in acidity and pH values.
3. The specific gravity and weight per gallon of ice milk increased
with proportional increase of algal protein isolates level in the mix
up to 30%.
4. The overrun decreased significantly when algal protein isolates
increased up to 30%.5. Replacing of non-fat dry milk with algal protein isolates caused
significant decrease in the rate melting.
6. Total solids, fat and ash content of ice milk was not affected by
replacing non-fat dry milk with algal protein isolates and did not
change during storage period.
7. Replacement of non-fat dry milk with algal protein isolates caused a
significant increase in total protein content. This increase was
proportional to the rate of replacement. The total protein content of
all ice milk simples did not change significantly as storage proceeded.
8. Titratable acidity of ice milk samples were not significantly
different from each other which means that replacement of non-fat
dry milk with algal protein isolates did not have a significant
effect on the acidity of ice milk. Titratable acidity of all ice milk
samples did not change significantly as storage period proceeded
up to the fourth weeks of storage period, then titratable acidity
increased slightly up the end of storage period.
9. pH values did not affect either by replacing non-fat dry milk with
algal protein isolates or as storage period advanced.
10. Ice milk containing 10% algal protein isolates contained the
higher content of both total and non-essential amino acids and
total essential amino acids.
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Summary
11. Replacing non-fat dry milk with 10% algae protein isolates
increases the crud fiber and mineral contents (magnesium,
sodium, potassium, manganese, iron, calcium and zinc).
12. Ice milk made by replacing 10% of non-fat dry milk with algal
protein isolates gained the highest score and was not significantly
different from control ice milk. While increasing the rate of
replacement above 10% decreased the scores of flavor of ice
milk. Control ice milk and treatment (T1) were not significantly
different from each other and they obtained high flavor score than
those of other treatment. It might be due to the trace of pleasant
seafood aroma.
Flavor of ice milk treatment improved over the six weeks of
storage and then after up to the end of storage period and gained
higher score.
Ice milk treatments made with algal protein isolates were
darker colour than the control. Therefore, it has been recommended
to decrease the amount of coca from 3 to 2%.
It could make a coca ice milk by replacing 10% of non-fat dry
milk that used in manufacture of ice milk by algal protein isolates
without detrimental effect of ice milk properties.
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Part (3): Effect of substitution non-fat dry milk (NFDM)
with algal protein isolates on yoghurt quality
made from cows milk:
Fermented milks are the oldest dairy products and yoghurt is
the most popular of these products in Egypt and worldwide. The
value of yoghurt in human diet is not only determined by the
nutritive value of milk from which is made, but also increased
digestibility, prophylactic and healing effects. Moreover, many
health benefits have been attributed to yoghurt such as improved
lactose tolerance, protection against gastrointestinal infections, effect
treatment of specific types of diarrhea, relief constipation, improved
immunity, cholesterol reduction and protection against cancer. The
consumption of yoghurt has been increased recently because of the
new technology that was able to produce a new variety of yoghurt
with different flavor and health benefits.
Seaweed has been used since ancient times as food, fodder and
fertilizer and as sources of medicinal drugs. Today seaweeds are the
raw material for industrial production of agar, carrageenan and
alginates (Barbara and Cremedes, 1993). They are nutritionally
valuable as fresh or dried vegetables, or as ingredients in a wide
variety of prepared foods (Robledo and Pelegrin, 1997).
Non-fat dry milk is used usually to overcome the week body &
texture and whey syneresis. Because of increasing the price of non-fat
dry milk and its availability at any time and some places many efforts
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have been to find other ingredients to replace non-fat dry milk partially
or completely. Therefore the objectives of this part of study were to
investigate the possibility of replacing non-fat dry milk with algal
protein isolate, effect of adding different fruit pulp, study the effect of
these ingredients on yoghurt quality and to monitor changes of yoghurt
quality during refrigerated storage period. Therefore, 13 batches of
yoghurt were made. Two control flavoured yoghurt like product
treatment (CF, CG) was made from cows milk that was fortified with
3.0% non-fat dry milk and 10% strawberry pulp and 10% guava
pulp. Another 4 batches were made from the same cows milk
except 10, 20, 30 and 40% of non-fat dry milk was replaced with
algal protein isolates and 10% strawberry pulp, respectively.
Another 4 batches were made as explained 10, 20, 30 and 40% of
non-fat dry milk was replaced with algae protein isolate and 10%
guava pulp. All treatments were stored in the refrigerator and were
sampled at 0, 3, 6, 9 and 12 days for chemical, rheological and
sensory evaluation.
The obtained results can be summarized as follows:
1. Replacement of non-fat dry milk with algal protein isolates caused
a significant increase in titratable acidity. Acidity of all yoghurt
treatments increased as the storage period progressed. Also
yoghurt treatment those made with strawberry pulp were not
significantly different from those made with guava pulp.
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2. pH value of yoghurt treatment decreased gradually as storage
progressed. Yoghurt treatments made with replacement of algal
protein isolates caused a significant decrease in pH values of
yoghurt treatments those made with strawberry pulp were not
significantly different from those made with guava pulp.
3. Total solids, fat and ash contents of all yoghurt treatments
followed similar trends. All yoghurt treatment were not
significantly from each other. On the other hand, total solids, fat
and ash contents of all yoghurt treatment did not change
significantly during storage period. Also total solids, fat and ash of
yoghurt treatments those made with strawberry pulp were not
significantly different from those made with guava.
4. Replacement of non-fat dry milk with algal protein isolates caused
a significant increase in total protein content. This increase was
proportional to the rate of replacement. The total protein content
of all yoghurt treatments did not change significantly as storage
proceeded. Yoghurt treatment those made with strawberry pulp
were not significantly different from those made with guava pulp.
5. Total volatile fatty acids (TVFA) of all yoghurt treatment increased
up to the end of storage period. Replacement of non-fat dry milk
with algal protein isolates and type of flavour did not have
significant effect on TVFA content of the resultant yoghurt
treatments.
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Summary
6. Replacement of non-fat dry milk with algal protein isolates caused
a significant decreased in acetaldehyde content. During cold
storage, acetaldehyde content decreased significantly in all
yoghurt treatment. Also yoghurt treatment those made by adding
strawberry pulp contained higher acetaldehyde than those
flavoured by adding guava pulp.
7. Replacement of non-fat dry milk with algal protein isolates caused
a significant increase in curd tension. On the other hand, yoghurt
treatment those made by adding strawberry pulp caused a higher
curd tension than flavoured made by adding guava pulp.
8. Whey syneresis of all yoghurt treatments decreased as storage
period proceeded up to sixth days of storage period, then increased
up to the end of storage period. Replacement of non-fat dry milk
algal protein isolates caused a significant reduction of whey
syneresis from yoghurt treatments. Yoghurt treatments those made
by adding strawberry pulp exhibited higher whey syneresis than
those flavoured by adding guava pulp.
9. Apparent viscosity of all treatments increased significantly as the
percentage of algal protein isolates increased. Yoghurt treatment
those made by adding guava pulp had a higher viscosity than those
made with strawberry pulp.
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10. Yoghurt treatment made by adding 10% algal protein isolates had
higher content of both total and non-essential amino acids and
total essential amino acids except leucine and threonine were
increased.
11. Replacing non-fat dry milk with 10% algal protein isolates
increased in crude fibers and minerals (magnesium, sodium,
potassium, manganese, iron, calcium and zinc).
12. Scores of organoleptic properties (flavour, body and texture,
appearance, acidity) followed almost similar trends. Score of
organoleptic properties did not change significantly during the
first three days of storage period, then decreased up to the end of
storage period.
It could be concluded that control yoghurt CF, CG were not
significantly different from treatment F, G, in all organoleptic
properties. Therefore, it could be made flavour yoghurt like product
by replacing 10% non-fat dry milk with algal protein isolates that
used in the manufacture of flavour yoghurt like product without
detrimental effect on yoghurt quality.