3.5 Analysis of Quality Parameters
The following procedures were conducted using internationally standardized methods as
prescribed by the American Oil Chemists' Society (AOCS) to ensure accuracy, reliability, and
consistency in the analysis of edible oil quality.
3.5.1 Free Fatty Acids
The method for determining free fatty acids (FFA) adhered to the AOCS Ca 5a-40 standard. To
ensure accuracy and reliability, several validation steps were undertaken. A blank titration was
performed to account for any impurities or interferences in the reagents. The sample weight was
measured using a pre-calibrated analytical balance to ensure precision. The sodium hydroxide
solution was standardized against a primary standard potassium hydrogen phthalate to ensure
accurate normality. The endpoint for titration was consistently identified as the appearance of a
permanent pink color for 30 seconds, using phenolphthalein as the indicator. The ethanol and oil
mixture was warmed on a hot plate to ensure complete dissolution and reaction. The procedure
was conducted in triplicate, and standard deviations were determined to verify the consistency
and reliability of the results.
3.5.2 Peroxide Value (PV)
Peroxide value (PV) was determined according to the AOCS Cd 8-53 method. To validate this
method, a blank titration was conducted to correct for any peroxide present in the reagents. The
sample weight of 5.0 g was measured accurately using a pre-calibrated analytical balance. To
confirm its normality, the sodium thiosulphate solution was standardized before analysis using
primary standard potassium dichromate. The oil and acetic acid-chloroform solution mixture was
swirled consistently for 2 minutes to ensure complete dissolution. The procedure was performed
in triplicate, and standard deviations were calculated to verify the consistency and reliability of
the results.
3.5.3 p-Anisidine Value
The p-anisidine value was determined using the AOCS Cd 18-90 method. To ensure the validity
of this method, the sample weight was measured accurately using a pre-calibrated analytical
balance. Calibrated measuring glassware was used to ensure consistent concentration, and the
UV-Vis spectrophotometer was pre-calibrated. A blank was measured before analysis to
establish a baseline. The procedure was repeated to confirm consistency, and it was performed in
triplicate with standard deviations calculated to verify the reliability of the results.
3.5.4 Iodine Value
The iodine value was determined using an FT-NIR (Fourier Transform Near-Infrared)
spectrometer. The FT-NIR spectrometer was calibrated using a set of standard oil samples with
known iodine values, ensuring the machine provided accurate and reliable measurements. The
measurements were conducted under controlled temperature conditions of 55°C to ensure
consistency and reliability. The FT-NIR measurements were validated by comparing them with
traditional titration methods to ensure the accuracy of the data obtained. This involved cross-
referencing the iodine values obtained from the FT-NIR machine with those derived from
standard chemical titration methods. The procedure was repeated multiple times to verify the
consistency and reproducibility of the FT-NIR measurements, ensuring reliable results across
different samples and measurement sessions. The FT-NIR machine underwent operational
qualification (OQ) to ensure it operated correctly and consistently under specified conditions,
including checks for wavelength accuracy, photometric accuracy, and baseline stability. The FT-
NIR machine's performance qualification (PQ) was validated by analyzing standard samples and
comparing the results with known values, ensuring the machine performed accurately in the
actual operational environment and met the required specifications.
Oxidative stability index
The method used to determine oil stability was according to the AOCS cd 12b-92 oil stability
test. Correction temperature Delta T was determined for each temperature setpoint and block. An
external pre-calibrated temperature sensor determined the temperature of the sample, while an
internal temperature sensor measured the heating block temperature. The difference between the
two that is block heating temperature and temperature of the sample measured by an external
temperature sensor was used as the correction temperature (Delta T).
The cell constant of each conductivity channel was determined using an analytical grade
standard of 1mmol/L of potassium chloride. The weighing balance used was within the
calibration schedule and validation of the weighing scales was done each morning.
Acknowledgment
This work is dedicated first and mostly to the Almighty God for the gift of life, energy, and
resources.
The work would not have been done if it had not been for Golden African Kenya Limited; they
opened their doors and allowed me to use their resources to achieve my goals. Much gratitude to
Mr. Dan Oyugi who, allows me to use some of the office hours to do the research work. Mr. Dan
Oola was very instrumental in data analysis and the entire personnel of the GAKL community.
To my supervisors, Prof Ruth Wanjau and Dr.Matthew Tonui, words wouldn't be enough to
show how grateful I am. The journey has been worthwhile, and the learning is immeasurable. I
will forever be in debt.
Last to my loving family, who sacrifice time and sleep just to make sure the trophy is brought
home. I am grateful for the support.
Dedication
This work is dedicated to my loving mother and dad, who believed in me.
