Monday 13 June 2016

Procedure for acid value determination

Weigh 0.5g or measure 0.5ml using pipette of the oil sample in a conical flask, add 3 drops of phenolphthalein indicator and add 20ml of ethanol. Titrate with 0.1N of NaOH.
Observation: a pink coloration is observed.
From the calculation using the following equation the acid value is gotten
(Tv ×N×56.1) ÷ wt of sample used.
Peroxide Value;

The peroxide value is a measure of the peroxides contained in the oil. During storage, peroxide formation is slow at first during an induction period which may vary from a few weeks to several months. When interpreting quantitative results, the particular oil or fat, the temperature, etc should be considered. The peroxide value is usually determined volumetrically. These methods depend on the reaction of potassium iodide in acid solution with the bound oxygen followed by titration of the liberated iodine with sodium thiosulphate. Chloroform is normally used as solvent.
Procedure
Measure o.5g of the sample, add 25ml of acetic acid and chloroform in the ratio 2:1. Add 1ml of 10% KI and shake vigorously. Cover and keep in the dark for 1min and add 35ml of starch indicator.
Observation: color changes to purple upon the addition of starch indicator. Titrate with 0.02N Na2S2O3. Observation: color changes to white
 (1000× (Tv2-Tv1) N) ÷ Wt of sample used. All in mg/kg
Saponification Value
The saponification value of an oil or fat is defined as the number of miligram of potassium hydroxide required to neutralize the fatty acids resulting from the complete hydrolysis of 1g of the sample. The esters of the fatty acids of low molecular weight require alkali for saponification, so that the saponification value is inversely proportional to the mean if the molecular weight of the fatty acids in the glycerides present. The saponification value is of the most use for detecting the presence of coconut oil (SV 255), palm kernel oil (SV 247), and the butter fat (SV 225), which contain a high proportion of the lower fatty acids.
Procedure
Weigh 0.5g pipette 0.5ml of the oil sample into a conical flask, add 50ml of 0.5N ethanolic KOH and reflux and allow cooling for 30minutes. Add 3 drops of phenolphthalein indicator and titrate with 0.5N HCl.
Observation: color changes from pink to colorless.
Then carry out the calculation to determine the saponification value
(56.1×0.5× (Tv2-Tv1)) ÷ wt of samples used. All in mg/KOH/g
PROXIMATE ANALYSIS
Proximate analysis is an analysis that is carried out to determine the presence of some vital nutrient contents in food materials and non-food materials. These nutrients or food materials include:
·       Crude fiber
·       Moisture content
·       Ash content
·       Protein digestion
·       Fat content

·       Carbohydrate 

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