If a person sells to the purchaser's prejudice any food which is not—
of the nature, or
of the substance, or
of the quality,
of the food demanded by the purchaser, he is guilty of an offence, subject to section 3.
In subsection (1) the reference to sale shall be construed as a reference to sale for human consumption; and in proceedings under that subsection it is not a defence that the purchaser was not prejudiced because he bought for analysis or examination.