ENTREVISTA AL DIRECTOR Y PERSONAL DEL DOBE País: Ecuador

Crude fibre is determined as that fraction remaining after digestion with standard solutions of sulphuric acid and alkali (Potassium hydroxide) under carefully controlled conditions.

Reagent

1. Sulphuric acid solution (1.25%) 2. Potassium hydroxide solution (1.25%) 3. Petroleum ether, boiling range 40 to 60^oc 4. Hot water

Instruments:

1. Hotplate

2. Beaker glass without spout

3. Fibre caps – capsule tray for 6 fibre caps + boiling stand & drying stand

4. Accessory: crucible for incineration 5. Drying chamber (oven) 105^oc 6. Muffle Furnace, Temp, 600^oc 7. Dessicator

8. Timer Principle

When doing a crude fibre analysis the components neither soluble with sulphuric acid nor with potassium hydroxide such as cellulose,

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hemicellulose and lignin are determined. The residual, undigested material is dried, weighed and then incinerated. The differences between the content and undigested part as the crude fibre is determined.

Procedure

Weigh 1.0g into the empty fibre caps which has been weighed and insert in the capsules tray. De-fating of the sample is especially important for samples with a high fat content. To de-fat, the capsules tray is immersed three times in a row into 100ml 40-60 petroleum ether. By turning it as well as moving it up and down with the help of the boiling stand, the sample is de-fatted, apply heat until sample is dry.

Pour sulphuric acid solution into the beaker, lower the capsules tray gently using the handle of the boiling stand. Mix it by stirring the boiling stand for about 1minutes so that the sample is entirely soaked and make sure the fibre cap is filled with washing solution and place the beaker on the hotplate which has been pre-heated for about 5 minutes. Bring it to a boil by setting it full. During this boiling stage the sample should floating freely in the fibre-cap. This can be done by gently stirring the boiling stand with the handling tool or by softy swirling tool thus draining the acid from the fibrecaps. Discard the acids with the solubles in the beaker. Rinse the fibre-caps contained in the fibre-capsule tray several times with hot water.

Pour potassium hydroxide solution into the beaker, repeat the above procedure with (KOH).

The fibrecaps are taken and dried in the oven with the use of drying stand.

After which each fibrecap is put into a crucible, weighed and recorded.

They are then placed in the muffle furnace at 600^oc to ash about 4 hours.

They are then brought out into the dessicator for another 30 minutes, and weighed.

Calculation

% fibre =^¼½. (.", ¼_b) –(¼_¾ . ¼_¿) – . Y ,

¼_B

Where W1 = weight of fibre caps

W₂ = weight of fibre caps with grinded sample W3 = dried sample + fibre cap

W4 = weight of small crucible

W5= weight of crucible removed from the furnace

3.1.6 Crude Fat (Ether Extract)

Reagent and Equipment:

1. Petroleum ether (b.p 40 – 60^oc)

115 2. Extraction thimbles

3. Soxhlet extraction apparatus 4. Fat cups

5. De-fatted cotton wool Method:

Weigh into an extraction thimble 1.0g of the dried grinded sample cover with defatted cotton wool weigh the fat cup to be used. Insert the sample thimble in the extraction unit 50mls of the solvent (petroleum ether) is added into the fat cups. The cups are heated by the electrical heating plate after control unit has being programmed extraction. The 4-step extraction procedure consists of boiling, rising recovery and pre drying.

After completion (it takes 1hr 30mins), remove the fat cup and place in the oven for some minutes. Then put in the dessicator, after which you take the weight of the extracted fat + fat cups.

Calculation

wieght of fat + fat cup − weight of fat cup weight of sample X 100 Free Fatty Acid

Acid value or FFA: The acid value of an oil or fat is defined as the number of mg of potassium hydroxide required to neutralize the free acid in 1g of the sample. The result is often expressed as the percentage of free acidity.

Reagents and Apparatus 1. Diethyl ether 2. Alcohol

3. Phenolphthalein solution (1%) 4. 0.1 ml sodium hydroxide Method

Mix 25ml diethyl ether 25ml alcohol and 1ml phenolphthalein solution (1%) and carefully neutralized with 0.1 M sodium hydroxide. Dissolve 1.0g of the oil in the mixed neutral solvent and titrate with aqueous 0.1M hydroxide shaking constantly until a pink colour which persists for 15sec is obtained. The titration should preferably not exceed about 10ml or other two phases are liable to separate.

Calculation

Acid value = ! & (') Y .3,

¼ '+ &.

FFA = acid value FFA = free fatty acids 2

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Ph Measurement

PH meter was switched on and allowed to warm for 5 minutes. The PH was then first standardised with PH buffer solutions of PH4, PH7, PH9 to ensure the sensitivity and accuracy of the meter this was done by dipping the same electrode of the meter into the respective buffer solution with thoroughly rinsing after each dipping.

The pH of sample was taken by dipping the same electrode after through rinsing in distilled water into the sample solution and pH value consequently read out on the meter readout unit.