Question

When the mustard oil is mixed with nitric acid, it gives a ______ that indicates adulteration of mustard oil.
A. Reddish brown ring appearance
B. Purple ring appearance
C. Reddish green ring appearance
D. None of the above

Answer 1

Hint: Adulteration is a process of mixing undesirable and inferior materials in food. The material or substance which is added to food is called adulterants. One of the fast screening methods is infrared spectroscopy which is used for a number of food adulteration applications.

Complete step by step answer:
Adulterated food is generally impure, unsafe or unwholesome food. Mustard oil is mostly adulterated with argemone oil. To detect the argemone oil in mustard oil, concentrated nitric acid is used. If the reddish brown colour or red colour appears in the acid layer, then it is adulterated with argemone oil.

Hence the option A is the correct one.

Additional Information:
Argemone oil is extracted from argemone seeds. It is mixed with sunflower oil and sesame oil to increase their quantity. Consumption of this oil leads to health disorders among children. Many oil brands mention ‘no argemone oil’ on their packs. In humans, argemone oil contained in adulterated mustard oil causes oxidative stress and death of red blood cells via met-haemoglobin formation by altering pyridine nucleotide and glutathione redox potential. Argemone oil contamination poses a serious threat to human health and should be checked by appropriate regulatory measures. Antioxidant therapy provides symptomatic relief and should be seriously considered for therapeutic interventions against argemone oil toxicity. Sulphuric acid also gives deep red colour on reacting with mustard oil. Development of red colour in this is due to formation of quinonoid compounds and hydrolysed sanguinarine salt which indicates the presence of argemone oil as adulterant. Upto 0.05% argemone oil adulteration can be detected with this new technique.

Note: The students generally get confused between purple rings and reddish brown rings. You should do this test at least once in your lab with the teacher and there you will get the reddish brown ring in the test tube. The other application of adulterant is that it is used to extend the quantity of the substance by reducing the quality of it.