Proximate Analysis of Milk Powder

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