SOP: Preparation of Dehydrated Sample for Analysis

GIFSQ — Global Institute for Food Safety & Quality

Principle

A representative portion of the dehydrated product is ground to a uniform fineness and thoroughly mixed, so that every analytical portion drawn from it represents the bulk. This ground preparation is not used for the enzyme tests, which are carried out on pieces of the product.

Apparatus required

• Grinder (suitable for dehydrated vegetables)
• 30-mesh sieve
• Coffee grinder (for dehydrated onion)

Procedure

General

Take a representative sample of at least 50 g

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Grind in a suitable grinder until at least 99% passes through a 30-mesh sieve

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Mix the material remaining on the sieve with the material that passed through; the mixture is the prepared sample

Dehydrated onion

Rapidly mix the bulk sample and take a representative sub-sample of about 25 g

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Pass the sub-sample through a coffee grinder

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Rapidly mix the whole of the ground sample, without sieving; the mixture is the prepared sample

Precautions

• Carry out all operations as expeditiously as possible: dehydrated vegetables are, in most cases, hygroscopic and take up moisture during grinding and handling.
• Do not discard the sieve residue; it is mixed back with the material that passed through.
• For dehydrated onion, mix rapidly before and after grinding, and skip the sieving step.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.