Four foods failed Centre for Food Safety checks in July.
Two fresh beef samples were found to contain illicit preservative sulphur dioxide, while a bottle of soybean milk and a prepackaged Chinese soup contained excessive bacteria.
The centre tested 11,600 food samples during the month and saw an overall satisfactory rate of 99.9%.
About 4,300 food samples were taken for chemical tests, 1,500 for microbiological tests, and the remainder were checked for radiation levels.
