Processing of Horticultural Crops

Exercise

Practical 5 - Estimation of Ash content

Aim: To estimate the ash content in fresh and processed products.

Theory and principle: Estimation of ash contents is important as it gives an idea about the presence of minerals in the food samples. Determination of ash is also required to evaluate fruit chutneys as the maximum limit for ash in this product shall not exceed 5% as per FPO specifications.

Apparatus/instruments/equipment

• Crucibles
• Heating plate
• Muffle furnace
• Desiccators
• Sensitive balance

Procedure for estimation

1. Place the crucibles in a muffle furnace and heat at 550ºC for 15 minutes.
2. Remove the crucibles from the furnace, cool in desiccators for one hour and weigh.
3. Weigh 5 g of sample in a crucible.
4. Keep the sample on a hot plate till it becomes thoroughly charred.
5. Place the crucible inside the muffle furnace and heat to 550ºC for 5 to 6 hours.
6. Let the furnace cool and take out the crucibles containing ash which is white in colour.
7. If traces of carbon still remain, cool the crucible and break up the ash with a glass rod.
8. Place the sample again in muffle furnace at 550ºC.
9. Cool the crucible in a desiccator and re-weigh the crucible containing ash.
10. Calculate ash using standard equation.

Observation:

Sample No.	Weight of empty crucible	Weight of sample	Weight of crucible with sample	Weight after Ashing	Ash (%)
1.
2.
3.

Calculations:

weight of crucible with ash – weight of crucible

Ash (%) = ------------------------------------------------------------ x 100

weight of sample