1. Lab # 5
Ash Analysis

2. Ash Determination using Dray Ashing
Determination of ash in food samples. Ashing is the 1st step in the preparation of a food sample for specific elemental analysis. Because certain food are high in particular minerals, ash content become important.

3. Materials Measuring dish. Dish holder. Scale.
Muffle furnace (dry oven).
Crucible save for muffle furnace use.
Tongs.
Desiccators.
Food sample

4. Procedures The general procedure includes the following steps:
Weigh the empty crucible and record its weight.
Weigh 5 g of the sample into a crucible.
Place crucibles in cool muffle furnace. Use tongs, gloves, and protective eyewear if the muffle furnace is warm.
Ignite hours (or overnight) at about 550°C until the sample become white or grey..
Turn off muffle furnace and wait to open it until the temperature has dropped to at least 250°C, open door carefully to avoid losing ash that may be fluffy.
Using safety tongs, quickly transfer crucibles to a desiccator. Cover crucibles, close desiccator, and allow crucibles to cool prior to weighing.

5. Calculation The ash content is calculated as follows: where:
dry matter coefficient = % solids/100
× 100
wt after ashing - tare wt of crucible
% ash
(dry basis) =
original sample wt x dry matter coefficient

6. Dry Matter Coefficient
dry matter coefficient = % solids/100
For example, if corn meal is 87% dry matter, the dry matter coefficient would be 0.87.

7. Result