Q. Determine the total ash content in flour?
After undertaking this activity, you will be able to:
• assess the mineral content in the given sample of flour,
• check the given sample for conformance to the standard for ash content,
• determine the total mineral content for dry samples, and
• estimate the increase in mineral content due to any fortification / enrichment of the flour.
Principle
Ash content of a foodstuff represents inorganic residue remaining after destruction of organic matter. It may not be the exact measure of the total mineral content, as some changes may occur due to volatilization of some components or some interaction between constituents. High ash content or a lower alkalinity of ash may be suggestive of the presence of adulterants. The acid-insoluble ash is a measure of sand and other silicious matter present. The process of combustion evaporates moisture and oxidizes the organic matter to vanish in air. The incombustible residue is the ash. The major constituents of the ash in flours are calcium, phosphorus, iron, sodium, potassium, halogens, silica or sand or silicious matter.
During the process of ashing, if the temperature crosses 570°C, then some of the inorganic salts in the ash get fused. Although, such fusion may not affect the total ash content of a sample but it affects the acid-insoluble ash. Over-heated ashes reflect a metallic tinge of the cations present. Copper imparts a greenish tinge, iron imparts a brownish and alkali metals a greyish tinge. Incomplete ashing gives a black tinge. The complete ashing is indicated by the absence of ember like glow in the ash when the crucible is observed immediately after taking it out of the furnace. Ash is significant for the miller because it is an indicator of the quality of the streams that are included in the flour. Ash content in the wheat kernel is higher near the bran layer or outside of the kernel. The center of the kernel has the lowest ash content.