University Assignment: Proximate Analysis of Milk Powder Report

This report details a student's investigation into the proximate analysis of milk powder, focusing on determining the levels of protein, fat, moisture, ash, and carbohydrates. The study employed various analytical methods, including Kjeldahl for protein determination, Soxtec for fat analysis, vacuum oven drying for moisture content, and dry ashing for ash content. The report outlines the experimental procedures, materials used, and the results obtained, comparing them with the manufacturer's specifications (Natco Ltd). The findings revealed discrepancies in protein and fat content compared to the manufacturer's data, while ash and moisture content showed similarities. The discussion section analyzes potential sources of error and their impact on the results, concluding with recommendations for improved accuracy in future analyses. The report highlights the importance of proximate analysis in food quality control, regulatory purposes, and product development, providing a comprehensive overview of the analytical processes involved.

PROXIMATE ANALYSIS OF MILK POWDER
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PROXIMATE ANALYSIS OF MILK POWDER
ABSTRACT
In any case there is need for product development, regulatory purposes and finally quality
control in the food industry, proximate analysis comes in handy. In this practical session,
proteins, fats, moisture, ash and carbohydrates in milk powder were well analyzed by the
proximate analysis procedure. Several methods were used in this practical and they include the
Kjendahl, Soxtec, Vacuum oven drying, the dry ashing and finally the indirect method. Results
did indicate that proteins were at 16.25%, fats were at 50%, moisture at 1.2% and finally the
results for ash were at 5.5%.This results when compared with the contents as indicated by the
original manufacture(Natco ltd) were similar with the exception of only proteins and fats.
INTRODUCTION
Proximate analysis is one of the procedures in the analysis of contents found in food and it
involves establishing the level or rather the content of proteins, fats, ash, carbohydrates and
finally moisture. All these fractions of food comes in handy for the purposes of quality control,
regulation and finally for product development. The core object of this experiment was to
determine the components of milk powder utilizing the proximate analysis method (Kaur &
Kochhar, 2017). The source of the milk powder for the experiment was NATCO food limited
and was prepared by evaporating milk in a heated chamber which later turned into finer particles.
To find out the content of each macronutrient, there were different methods used. The Kjeldahl
method was used to determine the level of proteins. The final amount of protein was calculated
through the nitrogen content found in the milk by what we call the conversion factor. Since the
Kjeldahl method is known to be very precise and reproducible, that was the reason as to why it

was preferred. In the estimation of fats on the other hand, Soxtec method was utilized since it is
very versatile and flexible besides the ability to manage several organic solvents extraction
demands.
Dry ashing was the method used to find out the content of ash present in the milk powder by
incorporating both the isomantle and the muffle furnace. There are several inorganic elements
which include calcium, potassium that exist within the ash and they usually remain after ignition
in the muffle furnace up to the time carbon is completely expelled. Loss of weight by drying
using the vacuum oven drier was used to find out the content of moisture present in the milk
powder. This method is widely preferred in the food industry since it is very simple and
reproducible. Finally, the carbohydrates were estimated by an indirect method that involve
summing up the quantity of the proximate.
According to a study by Marconi, it was found out that milk from a cow has higher protein in
comparison to that from the mare using the proximate analysis method (Gyar, Bala, & Reuben,
2014). There however, exist very little studies that aim to find out the composition of whole milk
powder in itself. There is therefore the need to further study that part.
Proximate analysis is key as it offers broad ideas on the quality of milk powder that is used in the
food industry. The analysis is to find out if the food produced is to the set standards of the
manufacturer’s specifications that assists in improving the overall quality of the food in case
there exist any form of discrepancy.

METHOD
Determination of moisture using the vacuum oven drying method.
Materials: gloves, analytical balance, pipette, desiccator, vacuum oven, glass rod, moisture dish,
ethanol, safety tongs, steam bath, milk powder, pipette and safety glasses.
Using an analytical balance, we weighed 10 g of sand and 2g of milk powder inclusive of the
moisture dish and the glass rod. We then added 10 cm3 of alcohol into the dish and all the
contents were thoroughly mixed by the rod. To evaporate the alcohol, the remaining dish was
transferred to the steam bath by using the safety tongs. The dish was later after evaporation,
placed into the vacuum oven for a period of one hour then later transferred to a desiccator. The
final reading was then made after cooling down.
(The detailed procedure can be found in appendix 1.)
Determination of protein using the Kjeldahl procedure
Materials: 0.2M HCL acid,50% m/v sodium hydroxide, kjeltic digestion tubes, kjeltec
distillation unit, digestion block, ash less filter paper,2% m/v boric acid,250cm3 conical flask,
gloves, milk powder, water and catalyst tablet.
A single gram of milk powder together with a catalyst tablet were placed in a filter paper which
was later folded. 15cm3 of the nitrogen free sulphuric acid and the filter paper were placed in the
kjeltec digestion tubes. A blank was then produced using the same procedure but this time
without the sample. The tube was then heated up in the digestion block at 400 0C up to the time
we saw a clear blue-green liquid. We however continued heating for 30 more minutes. The tube
was then removed and after cooling, 50 cm3 of the distilled water was then added. 25 m/v of the

boric acid was then added in the 250 cm3 conical flask and placed in the distillation unit. The
digestion tube was then placed into the unit and then added 50 % m/v sodium hydroxide aliquot
to offer a murky brown colour then the steam was distilled into the boric acid. The flask was then
removed together with the distillate and then 0.2 M HCL titrated up to the time the colour
changed to grey. This signified the end point.
(The detailed procedure is found in appendix 4)
Determination of ash
Materials: safety glass gloves, desiccator, analytical balance, silica crucible, muffle furnace,
milk powder, isomantle, safety tongs, heat proof mat.
We weighed the crucible using an analytical balance then weighed 5 g of milk powder in the
crucible. The crucible was then later transferred to the isomantle for a period of one hour until it
appeared black and dry and smoking stopped as well. The crucible was then removed and placed
in the muffle furnace for a period of 3 hours until it turned into ash. The crucible was then left to
cool in the desiccator so that it could be weighed to the analytical balance.
(The detailed procedure can be found in appendix 3)
Determination of fat using the soxtec method
Materials: Cotton wool, thimble, soxtec extraction unit, steam bath, gloves, milk powder,
petroleum ether, analytical balance, safety tongs, fan over, 150 cm3 flask.
Using an analytical balance, the weight of the tin was determined and then dry milk powder and
sand were then placed in the thimble. The excess was then wiped off using the cotton wool that
had been soaked in petroleum ether.50 cm3 of the petroleum ether was then used as the extracting

solvent while setting up the extraction unit. The thimble was then lowered into the tin in the
Soxtec extraction and the fat was then extracted for 45 minutes. When the thimble reach was
raised to the rinsing position for 15 minutes, the stopcock was closed then the ether evaporated
for 10 minutes. Close to the end of the process, the tin that contained the fat was removed then
transferred to the steam bath using the tongs. After the ether had evaporated in the steam bath,
the fat was left to dry into the fan for 20 minutes at 1030 C. Lastly, the tin was then removed from
the fan into the desiccator so as to allow cooling.
(The detailed procedure can be found at appendix 2)
RESULTS
Nutrients/proximate % (m/m) Energy conversion
factor
Energy value
kj kcal kj kcal
protein 16.25 17 4 33.25 20.25
fat 50 37 9 1850 450
Ash 5.5 - - - -
Moisture 1.2 - - - -
Total Carbohydrate
including fiber
27.05 16 3.75 432.8 101.43
Energy value:
TOTAL.
2316.05 571.68

% percentage error = experimental value – theoretical value X 100
Theoretical value
The percentage error for protein is calculated as follows;
Experimental value- theoretical value
=16.25-24.95
=-8.7
Therefore percentage error
=-8.7/24.95
=-0.3 x 100
=-33%
Percentage error for fat in the experiment
=experimental value-theoretical value
=50-26
=24
=24/26=0.9
Therefore % error for fat
=0.9 x 100
=90%

Percentage error for ash
Experimental value-Theoretical value
=5.5-6
=-0.5
Therefore % error for ash
=-0.5/6
=-0.08 x 100
=-8.3%
Percentage error for moisture
Experimental value- theoretical value
=1.2-6
=-4.8
Therefore % error for moisture
=-4.8/6
=-0.8
-0.8 x 100
=-80%.
Percentage error for carbohydrates

Experimental value-Theoretical value.
27.1-38.8
=-11.7
Therefore percentage error
=-11.7/38.8
=-0.3 x 100
=-30%.
DISCUSSION
The aim of the experiment was to determine the composition of the milk powder using the
proximate analysis method and it involved different methods such as the Soxtec method,
Kjeldahl method, the vacuum oven and finally the dry ashing method. A combination of this
methods assists in finding out the level of the macronutrients and the proximate in the milk
powder.
The ash content
The ash content of the milk powder was 5.5% as indicated on the table 1.This was found out
through the process of simple dry ashing method. In the calculations, it was the weight of the ash
over the sample weight and this was very important to identify the content of the ash. Like any
other experiment, there could be sources of error and they include high temperatures and the loss
of volatile minerals like zinc, iron and finally copper.

The fat content
Based on the findings as shown in table 1, it was found out that the fat content was 50% and it
was established through the Soxtec method that is a gravimetric procedure for analyzing fats. To
find out the percentage content of the fats during calculations, the weight of the sample was
compared against the weight of the fats. Product left behind during whipping the sample from the
lid with cotton wool presented a problem during the experiment. Inaccurate results might occur
since the exact amount of the sample had not been put forward to test.
Protein content
From the experiment, the protein content in the milk powder was 16.25% and was estimated by
the Kjeldahl method which is known for its precision and accuracy. Nitrogen content was very
key in calculations and the challenges during this method was that the amount of the catalyst
tablet and water were really reduced .As opposed to the recommended use of two tablets, only
one was used. As opposed to 75cm3 only 50 cm3 was used. This could alter the reliability and
accuracy of the results.
Moisture content
From the table, the moisture content was 1.2 % and it was estimated using the vacuum oven
drying method and it involves addition of ethanol and sand assists in calculating consistency of
milk powder. During evaporation of the alcohol, potential harm could arise from the tin
remaining in the bath for a very short period of time and this means not all the alcohol could
evaporate.
As compared to the content by the Natco manufacturers, the results were contradicting in that
manufacturers did indicate a protein content of 24.5%, fat 26%, moisture content 3.5% while the

ash content was at 6%.This therefore suggests that there are chances of some flaws during the
experiment.
CONCLUSION
The proximate analysis is an umbrella of several methods that are used to estimate
macronutrients in milk powder. The macronutrients include moisture, fat, protein, ash and
carbohydrate. This analytical method allows for calculations to find out the energy content of the
milk powder leading to production of what is known as the nutrition label. In comparison with
the data from the manufacturers, they were contrasting especially those of fats and proteins.
Results from as and moisture were however similar. It is therefore highly recommended that the
analysis be carried out with a lot of precautionary measures.

APPENDIX
1. Determination of moisture using the vacuum oven drying
1. Weighed 10g of sand using an analytical balance
2. Weighed sand, glass rod and moisture dish
3. 2g of powder milk powder and sand were weighed in the moisture dish using the
analytical balance
4. 10cm3 of ethanol was added to the dish using a pipette and mixed using a glass rod
5. The dish was then placed safely on the steam bath in the fume cupboard using the safety
tongs
6. After evaporation of the alcohol in the steam bath, the dish was then lifted using safety
tongs and was placed on the heat proof mat.
7. The dish was put in the vacuum oven and left for an hour to dry.
8. The dish was then removed from the oven and let to cool in the desiccator
9. Using an analytical balance, a final reading of the weight of the milk powder, sand with
the rod were then measured.
2. Determination of fat by the Soxtec method
1. Using an analytical balance, the weight of the tin was measured.
2. With the use of glass rod, dry milk powder together with sand were placed into the
extraction thimble.
3. With the use of cotton soaked in the petroleum ether, the remaining sample was wiped
then placed into the thimble.
4. The thimble was then placed in the tin