SOP: Determination of Total Ash Content in Milk Powder

GIFSQ — Global Institute for Food Safety & Quality

Scope

This method is applicable to all dairy products.

1. Principle

When milk powder is ignited at high temperature in a muffle furnace, organic matter is burnt out and mineral and other inorganic matter remains in the ash.

2. Apparatus

a. Platinum or silica crucible: about 70 mm diameter and 25 to 50 mm deep

b. Muffle furnace: capable of being controlled at 550 ± 20°C

c. Desiccator: containing an efficient desiccant

d. Safety tongs having long arms

e. Bunsen burner or electric hot plate

3. Procedure

Weigh accurately about 3 g of the dried milk sample in the crucible, previously dried in a hot air oven and weighed

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Heat the crucible gently on a burner or hot plate at first, and then strongly in a muffle furnace at 550 ± 20°C till grey ash is obtained

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Cool the crucible in a desiccator and weigh it

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Heat the crucible again at 550 ± 20°C for 30 minutes; cool the crucible in a desiccator and weigh

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Repeat this process of heating for 30 minutes, cooling and weighing until the difference between two successive weighings is less than 1 mg. Record the lowest mass

4. Calculation

Total ash (on dry basis), % by mass = [(M₂ − M) ÷ (M₁ − M)] × [100 ÷ (100 − M₀)] × 100

Where,
– M₂ = mass in g of the crucible with ash
– M = mass in g of the empty crucible
– M₁ = mass in g of the crucible with the material taken for the test
– M₀ = moisture, % by mass, calculated as per the method for dried milk

References

Manual of Methods of Analysis of Foods, Milk and Milk Products, FSSAI 2016, Method 10.7.