COLLEGE OF NATURAL SCIENCES DEPARTMENT OF CHEMISTRY FIELD ATTACHMENT REPORT AT UGANDA INDUSTRIAL RESEARCH INSTITUTE (UIRI) BY NIWEMUHWEZI ANSELM 12/U/946 UNIVERSITY SUPERVISOR: Assoc. Prof. Dr. STEVEN NYANZI ORGANISATION SUPERVISOR: Mrs. NABAGGALA RITAH A training report in partial fulfillment of the requirements for the award of the degree of Bachelor of Science in Industrial Chemistry of Makerere University August 2014
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COLLEGE OF NATURAL SCIENCES
DEPARTMENT OF CHEMISTRY
FIELD ATTACHMENT REPORT
AT
UGANDA INDUSTRIAL RESEARCH INSTITUTE (UIRI)
BY
NIWEMUHWEZI ANSELM
12/U/946
UNIVERSITY SUPERVISOR: Assoc. Prof. Dr. STEVEN NYANZI
ORGANISATION SUPERVISOR: Mrs. NABAGGALA RITAH
A training report in partial fulfillment of the requirements for the award of the
degree of Bachelor of Science in Industrial Chemistry of Makerere University
August 2014
i
DECLARATION
I NIWEMUHWEZI ANSELM declare that the work produced in this report is from my research
and the information given by the instructors during practical sessions.
………………………………….
Signature
……………………………………
Date
ii
APPROVAL
This is to certify that this report contains a true record of what was done by NIWEMUHWEZI
ANSELM during the eight weeks of training at UIRI from 09th/06to 1st/08/2014.
Signature…………………………..
Date ……………………………….
Organization Supervisor: Mrs. Nabaggala Ritah
Signature…………………………..
Date ……………………………….
University Supervisor: Assoc. Prof. Dr. Steven Nyanzi
iii
ACKNOWLEDGEMENT
Thanks go to the almighty GOD for the gift of knowledge which has enabled me to accomplish
all these activities.
Am pleased with UIRI administration for granting me this opportunity to train from here it was a
very good experience and I managed to learn a lot of things as pertains my career.
Am so grateful and humbled by my Organization supervisor Mrs. NABAGGALA RITAH and
the staff in the chemistry laboratory for the information and knowledge they provided and other
individuals who shared their knowledge with me during this training period.
It would not be appropriate to forget my university supervisor Assoc. Prof. Dr. Steven Nyanzi for
sacrificing his time to come and supervise me and the knowledge which he shared with me
especially in report writing and project.
And finally to those who have in any way helped me either financially, academically or
otherwise to make this publication a success.
iv
PREFACE
This report covers the work which was done in industrial training from 09 th/06/2014 to
08th/08/2014 (9 weeks). It includes various food analysis tests, fruit juice tests, water analysis
tests and soap analysis tests. All the experiments were carried out using standard operating
procedures (SOPs). All the results were treated to obtain the parameter being analyzed and
recommendations given appropriately. It further includes general recommendations to the
The combined experience in Training, Research, Business Analysis, and Engineering
Operations is in excess of 145 years, ranging from a low of 2 to a high of 29 years, and
averaging around 12 years.
A significant number of the management team has handled several projects of small, medium
to large, both in size and complexity.
1. Food Science and Technology
Undertakes research in industrial processes and technology for adding value to food products
The division is responsible for running pilot plants for processing dairy, meat, bakery, fruits
and vegetable products. Although the products from the pilot plants are available for sale to
the public, the cardinal role of the pilot plants is to train entrepreneurs and others from
tertiary and university institutions.
2. Ceramics
Responsible for research, design and production of high quality ceramics products
Department maintains a showcase at the Institute and some of their products are available for
sale to the public.
3. Training
Coordinates a spectrum of training programs from basic to advanced skill levels, and from
the starting to the fully formed entrepreneur Most training is conducted in-house and
programs are run by the staff of the institute.
4. Analytical Laboratories
Support internal research and offer services to the public in such areas as product analysis -
content and context, physical and chemical properties, or any analytical service that the client
might desire. Laboratories are divided into Analytical Chemistry, Microbiology and Mineral
laboratory.
5. Engineering and Manufacturing
This runs a maintenance engineering workshop as well as a carpentry shop, Provides all
engineering and technical maintenance services to the entire Institute, and coordinates any
engineering/technical services that may be contracted from outside.
Operations and Functions
In fulfillment of its mandates, UIRI performs the following functions:
1. Identify and develop appropriate technologies and processes for the exploitation of our
nation's natural resources.
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2. Upgrade and strengthen the existing indigenous technologies through basic and applied
research.
3. Set-up pilot plants to demonstrate the operation and benefits of new technologies, and
otherwise perform the role of an incubator for new industrial enterprises.
4. Design, develop and adapt machinery, tools, equipment and instruments suitable for small-
scale enterprises, especially in rural areas.
5. Maintain a comprehensive data bank on industrial research, technologies, materials and
products.
6. Facilitate the provision of technical advice and other assistance to existing enterprises in
order to improve their competences and their operational efficiencies.
7. Provide research findings to entrepreneurs to assist them in setting up new projects.
8. Collaborate with other organizations, both nationally and internationally, to create
synergies to improve knowledge, networking and capacity building for the benefit of our
client base and for rapid industrialization through technology transfer.
9. Serve as a production technology reference center.
1.2.THE CHEMISITRY LABORATORY
EQUIPMENT SAFETY GUIDELINES
Do not operate any equipment without permission
Carefully follow operating instructions when handling a given equipment
Switch off equipment after use
Report equipment malfunction immediately
Do not operate faulty equipment
HOUSE KEEPING
Before starting any task, the following are put into consideration;
All necessary things (reagents, equipment) should be returned to their places and only
required things are brought.
The work place should be cleaned
After doing any task, the following are considered;
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Collecting and cleaning the apparatus
All apparatus should be returned to storage
Cleaning the work place
At the end of the day, all apparatus should be returned to the place of storage and
work place cleaned and organized.
LABORATORY SAFETY GUIDELINES
Always wear gloves when handling corrosive substances
Keep your place and your place of work tidy
Clean up any spillages, acid or alkaline spillages should be neutralized first before
cleaning them up
Label reagents, samples, drawers clearly
Always use the fume hood when handling highly toxic substances
Always screw reagent bottle caps and chemical bottle tops tightly
Keep chemicals, apparatus and equipment in such a way that they will not fall down
Do not eat, drink or smoke in the laboratory
Do not pour corrosive substances into the sink but pour in glass dispersal bottles or
discard bottles
Do not add water to acid but acid to water
Do not pipette poisonous or hazardous solutions using your mouth, always use pipette
fillers
Do not handle reagent bottles by their necks
Report any accident that occurs immediately
Never leave potentially hazardous work unattended to
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CHAPTER TWO: INSTRUMENTATION
2.0. SOXTEC SYSTEM
This was used to analyze fat and oils in the samples. The Soxtec system provides a means of
safe and fast solvent extraction of foods, feeds and many more matrices. Extraction is used to
isolate soluble matter such as crude fat, additives, pesticides and minor constituents from
complex materials.
Extraction analysis is traditionally based on the Soxhlet principle because of its worldwide
accuracy and reproducibility. However convectional Soxhlet analysis involves tedious and
time consuming manual work and explosion risks. The patented design of Soxtec system HT
2 makes it possible to perform extractions using a wide range of solvents in a quicker, safer
and more economical way compared to the Soxhlet extractions. The combination of the
Soxtec extraction technique and wide range of solvent use makes the HT 2 Soxtec system a
flexible and powerful tool in the analysis of soluble compounds from materials such as; food,
feed, chemical technical products and pharmaceuticals.
Figure 2: A representation of Soxtec System
2.1. pH METER
A pH meter is an electronic device used for determining the acidity or alkalinity of a solution
(though special probes are sometimes used to measure the pH of semi-solid substances). A
pH meter consists of a special measuring probe (a glass electrode) connected to an electronic
meter that measures and displays the pH reading. At the bottom of the probe there is a bulb
which is the sensitive part of the probe as it contains a sensor. For every precise work, the pH
meter should be calibrated before each measurement. For normal use, verification should be
done at the beginning of each day using standard buffers of known pH. This is so because the
glass electrode does not give a reproducible electromotive force over long periods of time.
Verification should be done with at least two standard buffer solutions that span the range of
values to be measured.
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Operation
The solution whose pH is to be measured is put into a container and the probe is dipped into
it. When the values on the meter screen have stabilized, a button with the label “READ” is
pressed, the pH and the temperature are recorded.
After each single measurement, the probe is rinsed with distilled water or deionized water to
remove any traces of the solution, cleaned with tissue to absorb any remaining water that
could dilute the sample and hence alter the reading, and then quickly immersed in another
solution.
Note: The probes should be ocassionary cleaned (at least once a month) and this can be done
using pH electrode cleaning solution; generally a 0.1 M solution of hydrochloric acid is used
(having a pH of one). Alternatively, a dilute solution of ammonium fluoride (NH4F) can be
used.
Figure 3: A representation of pH meter
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2.2. MUFFLE FURNACE
A muffle furnace is used for providing extremely high temperature for example in
determination of ash content in a given sample.
PROCEDURE FOR OPERATION OF MUFFLE FURNACE
1. Plug equipment into power supply
2. Turn on the ‘on/off’ button on the front panel of the equipment.
3. Press ‘T’ on the front panel
4. Move cursor (in form of a dot) using the arrows on the front panel while adjusting
temperature by changing the number using the up ↑ and down ↓ arrows.
5. After setting the temperature move cursor at end of set temperature then press ‘start’.
Figure 4: A representation of Muffle furnace
2.3. ATOMIC ABSORPTION SPECTROMETER (AAS)
The A Analyst 400 Atomic Absorption Spectrum is a double –beam atomic absorption
spectrometer for flame or manual mercury hydride determinations. It is a sophisticated
analytical system capable of performing automated single element determinations.
OPERATING PROCEDURE
1. Read the safety information before you operate the system.
2. Turn on the Acetylene gas and adjust the outlet gauge pressure to the recommended
value of 14 Psig. NEVER allow the outlet gauge pressure to exceed 103kPa (1.03 bar,
15 Psig); acetylene can explode spontaneously above this pressure.
3. Turn on the Air compressor and adjust the outlet gauge pressure to the recommended
range of 70 to 80 Psig.
4. Open the lamp door and install the required lamp for the analyte element. Please note
the position for mercury, its either position 1 or 2.
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5. Switch on the spectrometer using the operational on/off switch. Close the lamp door
and wait for the spectrometer to complete initialization for about 5 minutes.
6. Activate the WinLab32 for AA software on the computer. Leave it to complete
initialization for about 2 minutes.
7. In WinLab32 for AA software select the Method icon and define the element of
interest. The wavelength and slit fields will automatically have the correct values.
8. Still under the Method icon, click “setting” and enter the current which is set to
10Afor all other elements except for Mercury which is 15A. Click “calibration” and
then select standard calibration, enter name of the Blank, standards and their
respective concentrations. Go to the “FILE icon” then select method, name the
method and save it.
9. In WinLab32 for AA software select the Sample info icon and then enter the sample
ID. Go to the “FILE icon” then select sample info, name the file and save it.
10. In the Flame Control window, select the on side of the flame On/Off switch to light
the flame and leave to initialize for 2 minutes.
11. Select “Manual window” and enter the name of the result file where you want to
save your results. OR you can create new folder for the results and save it. Select save
data and print log in the Manual window.
12. Load the Blank sample first onto the equipment, wait for 30 seconds and then select
“Analyze Blank” on the Manual window. This will activate analysis of the Blank.
Do not remove the Blank until “idle” is indicated on the window.
13. Load the standard samples onto the equipment and follow the order as entered in the
method icon (Standard concentration), wait for 30 seconds and then select “Analyze
Standard” on the manual window. This will activate analysis of the standard. Follow
the procedure for all the standards but first rinsing with blank before each analysis.
14. After analyzing the standards, Load the test sample on the equipment and follow the
order as entered in the sample info window, wait for 30 seconds and then select
“Analyze sample” on the manual window. Follow the same procedure for all
samples but first rinsing with blank before each analysis.
15. You can select the Results icon to view the results.
16. After analysis of the samples, select the Flame Control window select the off side of
the Flame On/Off switch to turn off the flame.
17. Turn off the acetylene gas by closing the valve. Wait for 2 minutes and then select the
‘Bleed gases” on the Flame Control window. Do it at least 2 times.
18. Turn off the WinLab32 for AA software and then switch off the spectrometer by
using the operational on/off switch. Switch off any other accessories.
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NOTE
Make sure that the sample loop is always immersed in de-ionized water.
Dispose of hazardous or corrosive solutions properly and refer to your local safety
regulations for proper disposal procedures
Figure 5: A representation of Atomic Absorption Spectrum (AAS)
2.4. UV/VIS SPECTROPHOTOMETER
For a beam of light incident on the sample part of the light is absorbed and the other emitted
using the principle of beer’s law samples can be analyzed.
Procedure for operation of UV/VIS spectrophotometer
Switch on power supply, switch on power stabilizer, turn on the UV/VIS
spectrophotometer using the green button on the top of the equipment and finally
switch on the computer.
Wait for equipment to initialize until it shows previously used method /wavelength.
On the computer programs is UV-win lab under which you should click Lambda Bio
20. The method window will open up.
Select method to be used for example scan, or Time drive.
Under the selected method set the required parameters like wavelength, number of
references, or number of samples.
Fill blank sample in one of the two marching Cuvettes (cells) and insert it in one of
the porches inside the spectrometer where light beams pass.
Click start. The equipment will ask for next sample blank so insert next sample blank
in remaining porch where light beam passes
11
Taking an example of the concentration method the equipment will then ask for
consecutive references /standards.
Figure 6: A representation of UV/VIS spectrophotometer
2.5. OVEN
Connect the power cable of the oven to the power outlet.
Ensure that the temperature setting potentiometer is set to a minimum.
Switch the On/Off key to the ‘ON’ position.
Adjust the temperature setting potentiometer to set the desired temperature.
Wait until the orange indicator lamp starts flashing continuously and the thermometer
is indicating the desired temperature, to insert items into the oven.
Close oven door and leave items inside for the desired period of time.
Remove the items from the oven, once the desired period of time has elapsed.
Set the temperature setting potentiometer to a minimum.
Switch the On/Off Key to the ‘OFF’ position.
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Figure 7: A representation of an Oven
2.6. WATER BATH
On heating, water increases in temperature and on reaching 100oC it boils hence heating up
whatsoever is in its contact
Procedure for operation of water bath
Check that the level of water is above the tray inside the water bath.
Plug equipment onto power supply
Press red button on front panel to switch on power in the equipment.
Set required temperature by pressing the “+” or “-” buttons corresponding to the
position of number. The green light will be lit up to show that equipment is gaining
the set temperature.
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Figure 8: A representation of a water bath
2.7. MAJI-METER
The Maji-Meter is capable of measuring up to 11 parameters in the field simply by
submerging the probe into a water course and using the control unit to run the test and view
results. It was used to determine pH, Turbidity, electrolytic conductivity (EC), dissolved
oxygen (DO), total dissolved solids (TDS), altitude, latitude and longitude of water samples
in the field. An integrated GPS system allows users to identify exactly where results were
taken and record other location information, providing more informative analyses. The Maji-
Meter can be used to analyze both surface and ground water in a variety of settings such as
rivers, lakes, industrial systems, wells and bore-holes.
Figure 9: A representation of Maji-Meter
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2.8. ANALYTICAL BALANCE
Procedure for daily use
i. Press ON/OFF button once to turn on the instrument
ii. Place a weigh boat on the balance pan. iii. Press the Tare control to zero the balance.
iv. Wait a few seconds until the reading has stabilized until the small box goes away v. Add the substance or chemical to be weighed. vi. Wait until the reading stabilizes and the small box goes away.
vii. Record the results.
Maintenance
i. The balance is calibrated annually with a standard set of weights by UNBS
ii. At the first time of weighing every day, a standard mass (5g) is used for verification. This helps to tell the need and agency for calibration. This acts as a quality control
(QC)measure Figure 10: A representation of an Analytical balance
15
2.9. KJELTEC SYSTEM
The Kjeltec Distillation Unit provides a simple and reliable solution for safe and semi-
automatic distillation. The procedure for its use is elaborated in the experiment for protein
digestion.
Figure 11: A representation of a Kjeltec system
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CHAPTER THREE: ANALYSIS
3.1. FOOD ANALYSIS
EXP 1: DETERMINATION OF ASH CONTENT
Ash content is a measure of minerals in the food. Ash refers to the inorganic components
remaining after either ignition or complete oxidation of organic matter in a foodstuff. The
importance of Ash in Food analysis is to proximate the nutritional evaluation and it is the
first step in the preparation of food sample for specific elemental analysis.
Mineral content is a measure of the amount of specific inorganic components present within
a food, such as Ca, Na, K and Cl. Determination of the ash and mineral content of foods is
important for the following reasons:
Nutritional labeling: The concentration and type of minerals present must often be
stipulated on the label of a food.
Quality: The quality of many foods depends on the concentration and type of
minerals they contain, including their taste, appearance, texture and stability.
Microbiological stability: High mineral contents are sometimes used to retard the
growth of certain microorganisms.
Nutrition: Some minerals are essential to a healthy diet (e.g. Calcium, phosphorous,
potassium and sodium) whereas others can be toxic for example lead.
There are two types of ashing used that is;
1) Dry Ashing: it refers to the use of a muffle furnace that is capable to maintain
temperatures of 500-600°C. Water and volatiles are vaporized and organic substances
are burned in the presence of oxygen in air to CO2, and oxides of N2. Most minerals
are converted to oxides, sulfates, phosphates, chlorides, and silicates.
2) Wet Ashing; this is a procedure for oxidizing organic substances by using acids and
oxidizing agents or their combinations. Minerals are solubilized without
volatilization. Wet ashing is often preferable than dry ashing as a preparation for
specific elemental analysis.
PROCEDURE
The weight of the crucible was first determined and recorded. 5g sample were weighed into a
tarred crucible and then heated first to evaporate the volatile matter. The crucibles were
placed in muffle furnace. Their order of arrangement in the furnace was recorded. The
furnace was ignited for 6 hours at 550oC.The muffle furnace was turned off and later opened
when the temperature had dropped to 250oC. The sample in crucible should be completely
white with no black spots. Using safety tongs, the crucibles were removed, re-labeled using
17
the recorded arrangement and transferred to a desiccator and allowed to cool prior to
weighing. After cooling the sample was weighed and results recorded in the work book.
NOTE
1) If carbon is still present following initial incineration, add several drops of water or
nitric acid; the sample should be re ashed. If the carbon persists, such as with high
sugar samples follow this procedure;
Suspend the ash in water and filter through ash less filter paper because this residue tends
to form a glaze. Dry the filtrate Place paper and dried filtrate in muffle furnace and re dry
2) Warm crucibles will heat air in the desiccator. With hot samples, a cover may bump
to allow air to escape. A vacuum may form on cooling. At the end of the cooling
period, the desiccator cover should be removed gradually by sliding to one side to
prevent a sudden in rush of air. Covers with ground glass sleeve or fitted for a rubber
stopper allow for slow release of vacuum.
TABLE OF RESULTS
Sample ID: 166/2014
Replicate 1 Replicate 2 Replicate 3
Weight of crucible (g) 61.9818 67.8837 67.1456
Weight of sample (g) 5.0021 5.0057 5.0021
Weight of sample + crucible (g) 62.2274 68.1269 67.3158
TREATMENT OF RESULTS
Weight of Ash = (Weight of Ash + crucible) - weight of crucible
Percentage of Ash = weight of Ash
weight of sample x 100%
Replicate 1
Weight of Ash = (62.2274 – 61.9818)
= 0.2456g
Percentage of Ash = 0.2456g
5.0021g x 100%
= 4.91%
18
Replicate 2
Weight of Ash = (68.1269– 67.8837)
= 0.2432g
Percentage of Ash = 0.2432g
5.0057g x 100%
= 4.86%
Replicate 3
Weight of Ash = (67.3158– 67.1456)
= 0.1702g
Percentage of Ash = 0.1702g
5.0021g x 100%
= 3.40%
Calculation of mean percentage
Mean =∑𝒙
𝒏 =
(𝟒.𝟗𝟏+ 𝟒.𝟖𝟔+𝟑.𝟒𝟎)
𝟑= 𝟒. 𝟑𝟗%
Calculation of standard deviation
Percentage X Deviation (X— X ) Square deviation (X— X )2
4.91 0.52 0.2704
4.86 0.47 0.2209
3.40 -0.99 0.9801
∑ (X— X )2 = 1.4714
Standard deviation = √(∑(X— X )2)
𝒏−𝟏
=√(1.4714)
𝟐= 𝟎. 𝟖𝟓𝟕𝟕%
19
Calculation of Relative standard deviation (RSD)
RSD = 𝑺𝒕𝒂𝒏𝒅𝒂𝒓𝒅 𝒅𝒆𝒗𝒊𝒂𝒕𝒊𝒐𝒏
𝒎𝒆𝒂𝒏 =
(0.8577)
4.39 x 100%
RSD = 19.54%
RECOMMENDATION
The experiment should be repeated because the relative standard deviation is greater than 5%
(RSD > 5%)
EXP 2: DETERMINATION OF FAT CONTENT USING SOXHLET METHOD
Total Fat refers to the sum of triglycerides, phospholipids, wax ester, sterols and minor
amount of non-fatty materials
Apparatus
Extraction unit 1043 Soxtec System HT6 - service unit 1046, Soxtec System HT6
Extraction cups
Cup holder
Tongs for extraction cups
Thimbles and adapters
Reagents - petroleum ether
PROCEDURE
PREPARATION OF ALUMINIUM CUP
The aluminium cup was first washed with acetone and rinsed with distilled water
The aluminium cup was dried in an oven for 5 hours.
The dried aluminium cups were kept in a desiccator ready for use.
PREPARATION OF SAMPLE
2g of dried sample were weighed out accurately into a cellulose thimble of already
determined dry weight. Care was taken not to spill sample powder outside thimble. A
thimble was then placed in an aluminium cup.
SETTING UP THE EXPERIMENT
A thin layer of cotton wool was placed on top of the sample in the thimble.
The adapter was inserted on top of cotton wool in the thimble.
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On the extraction unit, the adjustable nob of each side of the unit was raised upward
and the thimbles (for two samples) were attached in their positions tightly.
The knobs were lowered to allow thimbles to lift up and give space for fixing the
aluminium cups.
60ml of petroleum ether were measured in a measuring cylinder and transferred to
each of the aluminium cups.
The rubber ring was placed on each of the aluminium cups.
Each cup was placed on top of the extraction hot plates and then adjusted using the
lower knobs so as to attach each cup under its corresponding thimble as labeled, that
is, 1 for 1, or 2 for 2.
The upper adjustable knob was raised in the boiling position so as to allow the
thimble units get inserted into the petroleum ether (solvent) in each aluminium cup
NOTE
1. Care is taken to ensure that all fittings are air tight
2. Aluminium cups must not be interchanged
The tubings connected from the service unit and tap (water) to extraction unit
were kept in position as required and air tight.
Tap water was opened, and confirmed that it flows to the condensing unit and
returns to the sink through drain.
STARTING TO RUN THE EXPERIMENT (boiling)
The mains of the service unit was switched on.
The extraction temperature was adjusted to 1000C and set the safety knob to
1500C.
The extraction process was monitored. Condensation of the solvent was seen
rolling down back to the sample through the extraction unit taps in open position.
When condensate was seen rolling down (checked by closing and opening taps
temporarily and leaving open), the timer was turned in the clockwise direction to
the 30minute mark so that boiling should run for 30minutes.At the end of boiling
time, timer rings while returning back to the 60/0 minutes mark.
RINSING
At the end of boiling, thimbles were raised out of the solvent by pressing the
upper buttons to the RINSE position.
Timer was immediately set to 30 minutes.
At the end of the rinse time (30 minutes), taps of extraction unit were closed to
stop solvent from condensing through the thimbles.
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Solvent was left to condense and collect above the taps at the base of the
condenser. This process was left to run until no more solvent was condensing.
DRYING RESIDUE AND EVAPORATION OF SOLVENT
The compressed air valves were raised upward to open them (on the extraction
unit).
On the service unit, compressed air supply was switched on and set timer15
minutes.
NOTE: compressed air facilitates drying of the residue in the thimbles and evaporation
of the solvent further from the thimbles and aluminium cups
CLOSING DOWN
At the end of drying, compressed air was switched off, air taps closed, power
switched off, and the flow rate of the cooling water reduced.
The apparatus was left to cool for 15 minutes
Cooling water was turned off completely.
Aluminum cups were removed carefully (should be having oil).
The cups were put in the oven, set at 1050C, and left to dry for two hours.
At the end of 2hours, oven was switched off and left to cool to 400C without
opening its door.
At 400C, the cups were removed, put in the desiccator, and left to cool in there for
exactly 30 minutes.
At the end of 30 minutes, each cup was weighed, obtaining weight W3
The percentage fat content in food samples was determined using the following
formula;
% fat = (W3 − W2)
W1 x 100
Where W3= Weight of extraction cup + residue weight (g)
W2 = Weight of extraction cup (g)
W1 = original sample weight (g)
TABLE OF RESULTS
Dry weight of cup (W2) (g) No.1 No.2
38.7855 38.6098
Weight of the sample (W1) (g) 3.0094 3.0016
Weight of cup + residue weight (W3) (g) 39.1003 38.8828
Weight of Oil (g) 0.3148 0.273
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TREATMENT OF RESULTS
% fat = Weight of Oil
Weight of Sample x 100%
Replicate 1
% fat = 0.3148
3.0094 x 100%
% fat = 10.46%
Replicate 2
% fat = 0.273
3.0016 x 100%
% fat = 9.10%
Calculation of mean percentage
Mean =∑𝒙
𝒏 =
(10.46+9.10)
2= 9.78%
Calculation of standard deviation
Percentage X Deviation (X— X ) Square deviation (X— X )2
10.46 0.68 0.4624
9.78 0.68 0.4624
∑ (X— X )2 = 0.9248
Standard deviation = √(∑(X— X )2)
𝒏−𝟏
=√(0.9248)
𝟐−𝟏= 𝟎. 𝟗𝟔𝟏𝟕%
Calculation of Relative standard deviation (RSD)
RSD = 𝑺𝒕𝒂𝒏𝒅𝒂𝒓𝒅 𝒅𝒆𝒗𝒊𝒂𝒕𝒊𝒐𝒏
𝒎𝒆𝒂𝒏 =
(0.9617)
9.78 x 100%
RSD = 9.83%
23
Recommendation
The RSD is greater than 5% because one of the sides of the Soxtec machine leaks so the
petroleum ether used for extraction leaks which leads to low mass of the fat extracted. Thus
replicate 1 result is the correct one.
EXP 3: DETERMINATION OF MOISTURE CONTENT IN FOOD SAMPLES
PRINCIPLE
Moisture determination is one of the most important analyses performed on a food sample
and yet one of the most difficult from which to obtain accurate and precise data.
The dry matter that remains after moisture removal is referred to as Total solids. This
analytical value is of great economic importance to a food manufacturer because water is
inexpensive filler.
Moisture is a quality factor in the preservation of some food products and affects the food
stability for example, in dried milks and dehydrated vegetables and fruits.
Computation of nutritional value of foods requires that you know the moisture content.
Moisture data are used to express results of other analytical determinations on a uniform
basis (such as, dry weight basis)
EQUIPMENT AND MATERIALS
Usual laboratory apparatus not otherwise specified, and the following items
o Electric drying oven
o Petri dishes
PREPARATION OF GLASSWARE
The glassware were washed and rinsed with distilled water.
Dry glassware was placed in electric oven for 4 hours at1050c
Glassware were removed from the oven and then cooled in the desiccator for 30
minutes
After 30 minutes, the glassware was weighed and recorded the weights respectively.
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PROCEDURE
5g of sample was weighed into the petri-dish. The sample was heated in an electric oven for
4hours set at 1050C. After, the sample was removed from the electric oven then transferred to
the desiccator to cool to room temperature for 30 minutes. After the sample and the petri-dish
were weighed results recorded.
The moisture content calculations were determined using the formula