Lab # 5

Ash Analysis

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.

Materials

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

ProceduresThe general procedure includes the following steps:

1) Weigh the empty crucible and record its weight.2) Weigh 5 g of the sample into a crucible. 3) Place crucibles in cool muffle furnace. Use tongs,

gloves, and protective eyewear if the muffle furnace is warm.

4) Ignite 10-12 hours (or overnight) at about 550°C until the sample become white or grey..

5) Turn off muffle furnace and wait to open it untilthe temperature has dropped to at least 250°C, open door carefully to avoid losing ash that may be fluffy.

6) Using safety tongs, quickly transfer crucibles to a desiccator. Cover crucibles, close desiccator, and allow crucibles to cool prior to weighing.

Calculation

• The ash content is calculated as follows:

• where:

dry matter coefficient = % solids/100

%ash )dry basis (

=

wt after ashing - tare wt of crucible

× 100 original sample wt x dry matter coefficient

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.

Result