We tested the food for contamination by cleaning agents known as quaternary ammonium compounds (QAV) and pathogens such as salmonella and listeria , as well as for germs indicating poor hygiene. Contamination with QAV may have come from improper cleaning of the machines used to make milkshakes and soft serve ice cream.

Six milkshakes were judged to be harmful to health because of the high residue levels of QAV found, eight samples showed an elevated bacterial count, and 27 samples exceeded the permitted maximum residue level of QAV of 0.01 mg/kg.

The many detections of QAV residues indicate insufficient rinsing with water after cleaning. The companies are likely to have changed the cleaning procedures; during follow-up checks, the specified maximum residue level for QAV was complied with.