Food Standards and Quality Control

Food Standard and Quality Control

Lesson 03 :Food Sampling

Problems in Sampling

1. Sample bias: Bias may be introduced by non probability sampling plans such as purposeful or convenience sampling. Bias may also result from substitution of a more conveniently acquired sample by the sampler.


2. Identification of the sample
   Sample containers should be clearly identified with markings that are not affected during transportation and storage. Plastic bags that are later to be stored in ice water should be marked with water- insoluble inks. Otherwise, samples may be unidentifiable at their destination.


3. Sample storage
   The sample should be placed in an appropriate container that protects it from moisture loss or absorption during transport and storage. The sample should be stored under conditions that prevent degradation. The method of protection depends upon the final use of the sample. If the constituent of interest is light sensitive, the sample should be protected from light by being wrapped with aluminum foil or placed in an amber or otherwise opaque container. If oxygen can cause changes in the sample, it should be stored under nitrogen or other inert gas. If temperature is a problem, it should be controlled. Freezing protects many samples, but it should be avoided in products consisting of unstable or potentially unstable emulsions. Preservatives (e.g., mercuric chloride, potassium dichromate, chloroform) may be used under some conditions