8.2 DETERMINATION OF TOTAL ASH
Take fresh sample for the determination, rather than left over after determination of moisture. Ignite the dried material in the dish left after the determination of moisture with the flame of a burner till charred. Transfer to a muffle furnace maintained at 550 – 600°C and continue ignition till grey ash is obtained. Cool in a dessicator and weigh. Repeat the process of heating, cooling and weighing at half hour intervals till the difference in weight in two consecutive weighings is less than 1 mg. Note the lowest weight. If ash still contains black particles add 2-3 drops of pre-heated water at 60°C. Break the ash and evaporate to dryness at 100-110°C. Re-Ash at 550°C. Until ash is white or slightly grey.
Performance characteristics to be defined in the current method as proposed below: Limit of detection : 0.055 Repeatability : 0.06gm/100gm Reproducibility : 0.20 gm/100 gm for homogeneous products like milk powders
0.60 gm/100 gm for heterogeneous products like pet foods, meat products etc.
8.2.2 Calculation
Total ash on dry basis (% by weight) = (W2 – W) X100
W1 – W
Where,
W2 = Weight in gm of the dish with the ash
W = Weight in gm of empty dish
W1 = Weight in gm of the dish with the dried material taken for test
(Ref:- AOAC 17th edn Official method 923.03 Ash of flour)
*Moisture correction factor to be included in the formula
Reference of
.3.2 Procedure
To the ash contained in the dish, add 25 mL of dilute HCl, cover with a watch glass and heat on a water bath for 10 minutes. Allow to cool and filter the contents of the dish through Whatman filter paper No 42 or its equivalent. Wash the filter paper with water until the washings are free from acid and return it to the dish. Keep it in the electric oven for 3 hours to dry. Ignite in a muffle furnace at 550 – 600°C till white or grey ash is obtained. The filtrate can be dried for 30 min in an oven at 103±2°C. Cool in a dessicator and weigh. The filtrate obtained should be free for chloride/acid. To check this, add few drops of 2M nitric acid and 0.1 M Silver nitrate solution. No precipitate or milky turbidity should occur. Repeat the process of igniting, cooling and weighing till the difference in two consecutive weighs is less than 1 mg. Note the lowest weight.
Performance characteristics to be defined in the current method as proposed below: Limit of detection: 0.05 %
Repeatability: not greater than 20%.
Reference of Method Recommended
1) AACC (1995). “Ash – Basic method” in approved methods of the American Association of Cereal Chemists, 9th edition.
2) AOAC International (1995) « Ash of flour – direct method » in Official Methods of AOAC International, method 923.03, (23.1.05).
3) AOAC International (1995) « Ash of milk – gravimetric method » in Official Methods of AOAC International, method 945.46, (33.2.10).
4) AOAC International (1995) « Ash of meat» in Official Methods of AOAC International, method 920.153, (39.1.09).
5) ISO 2171:1993 « Cereals and milled cereal products – Determination of total ash.
6) ISO/DIS 936 « Meat and meat products – determination of total ash » (Revision of ISO 936:1978).
7)AOAC 17th edn Official method 923.03 Ash of flour
Take fresh sample for the determination, rather than left over after determination of moisture. Ignite the dried material in the dish left after the determination of moisture with the flame of a burner till charred. Transfer to a muffle furnace maintained at 550 – 600°C and continue ignition till grey ash is obtained. Cool in a dessicator and weigh. Repeat the process of heating, cooling and weighing at half hour intervals till the difference in weight in two consecutive weighings is less than 1 mg. Note the lowest weight. If ash still contains black particles add 2-3 drops of pre-heated water at 60°C. Break the ash and evaporate to dryness at 100-110°C. Re-Ash at 550°C. Until ash is white or slightly grey.
Performance characteristics to be defined in the current method as proposed below: Limit of detection : 0.055 Repeatability : 0.06gm/100gm Reproducibility : 0.20 gm/100 gm for homogeneous products like milk powders
0.60 gm/100 gm for heterogeneous products like pet foods, meat products etc.
Total ash on dry basis (% by weight) = (W2 – W) X100
W1 – W
Where,
W2 = Weight in gm of the dish with the ash
W = Weight in gm of empty dish
W1 = Weight in gm of the dish with the dried material taken for test
(Ref:- AOAC 17th edn Official method 923.03 Ash of flour)
*Moisture correction factor to be included in the formula
Reference of
To the ash contained in the dish, add 25 mL of dilute HCl, cover with a watch glass and heat on a water bath for 10 minutes. Allow to cool and filter the contents of the dish through Whatman filter paper No 42 or its equivalent. Wash the filter paper with water until the washings are free from acid and return it to the dish. Keep it in the electric oven for 3 hours to dry. Ignite in a muffle furnace at 550 – 600°C till white or grey ash is obtained. The filtrate can be dried for 30 min in an oven at 103±2°C. Cool in a dessicator and weigh. The filtrate obtained should be free for chloride/acid. To check this, add few drops of 2M nitric acid and 0.1 M Silver nitrate solution. No precipitate or milky turbidity should occur. Repeat the process of igniting, cooling and weighing till the difference in two consecutive weighs is less than 1 mg. Note the lowest weight.
Performance characteristics to be defined in the current method as proposed below: Limit of detection: 0.05 %
Repeatability: not greater than 20%.
1) AACC (1995). “Ash – Basic method” in approved methods of the American Association of Cereal Chemists, 9th edition.
2) AOAC International (1995) « Ash of flour – direct method » in Official Methods of AOAC International, method 923.03, (23.1.05).
3) AOAC International (1995) « Ash of milk – gravimetric method » in Official Methods of AOAC International, method 945.46, (33.2.10).
4) AOAC International (1995) « Ash of meat» in Official Methods of AOAC International, method 920.153, (39.1.09).
5) ISO 2171:1993 « Cereals and milled cereal products – Determination of total ash.
6) ISO/DIS 936 « Meat and meat products – determination of total ash » (Revision of ISO 936:1978).
7)AOAC 17th edn Official method 923.03 Ash of flour
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