The flour you use to bake bread, whip up cookies, or roll out noodles may harbor hidden contaminants. A new investigation by the Hong Kong Consumer Council (HKCC) has revealed that over 90% of wheat flour samples collected from local supermarkets and specialty stores contain detectable levels of heavy metals, while four brands also tested positive for a vomiting toxin that can cause abdominal pain and fever. The council tested 30 varieties of wheat flour—including plain, bread, and cake flours—for food safety, quality, and composition, publishing the findings in June 2024.
Metals and Pesticides: What the Tests Found
The HKCC screened all samples for six heavy metals: arsenic, cadmium, chromium, lead, antimony, and mercury. Only two brands—White Wings and Coles—were entirely free of these contaminants. The remaining 28 samples contained cadmium, ten contained arsenic, two had chromium, and one showed lead. However, the council noted that all levels fell below Hong Kong’s regulatory limits for wheat flour, posing no significant health risk under normal consumption.
Pesticide residues were another concern. Glyphosate, a herbicide classified by the International Agency for Research on Cancer as “probably carcinogenic to humans” (Group 2A), was found in 16 samples. Among non-wholemeal flours, King’s Flour (金像牌) had the highest level at 0.18 mg per kilogram. For wholemeal high-gluten products, M&S Food topped the list at 0.45 mg per kilogram. Again, all concentrations were below legal limits, and the council concluded that ordinary use should not harm health.
Vomiting Toxin Detected in Four Brands
A more acute concern is the presence of deoxynivalenol (DON), commonly known as vomiting toxin. This mycotoxin cannot be removed through cooking or processing. Ingesting large amounts can trigger nausea, vomiting, diarrhea, abdominal pain, and fever within 30 minutes. Hong Kong currently has no specific limit for DON in wheat flour, but the European Union sets a cap of 750 micrograms per kilogram, while the World Health Organization recommends a tolerable daily intake of 1 microgram per kilogram of body weight.
Four brands tested positive for DON: Sau Tao (壽桃牌), Sun’s Kitchen (日之廚), Coles, and White Wings. The highest level was found in Sun’s Kitchen, with concentrations ranging from 117 to 306 micrograms per kilogram—all below the EU threshold. The council warned that children, due to their lower body weight, have a smaller safety margin and should be monitored. Teenagers and adults face a low risk under normal dietary patterns.
Insect Fragments and Rodent Hair: A Common Issue
Every single flour sample contained microscopic insect fragments, a type of light foreign matter visible only under a microscope. The count ranged from 1 to 57 fragments per 50 grams of flour, with Lee Cheung Wo (李祥和) showing the highest level. All were below the U.S. Food and Drug Administration’s action levels.
Additionally, Showa and M&S Food each contained rodent hair—one and two hairs per 50 grams, respectively—meeting or slightly exceeding U.S. standards. The council emphasized that no studies have shown these impurities to be harmful to humans, so consumers need not overreact.
Despite these findings, all 30 samples received food safety scores of 4.5 or higher out of 5, indicating overall acceptable quality.
Understanding Gluten: High, Medium, and Low Protein Flour
The term “gluten” refers to the network formed when flour is mixed with water and kneaded. Two proteins—glutenin and gliadin—combine to create elasticity and extensibility. Higher protein content means more gluten and greater toughness. This explains the classic uses:
- Low-gluten flour (cake flour): For cakes, muffins, and cookies.
- Medium-gluten flour (all-purpose): For cakes, cookies, bread, and udon noodles.
- High-gluten flour (bread flour): For bread and pizza bases.
Broader Implications and Next Steps
The HKCC’s findings highlight the need for clearer regulations, particularly for vomiting toxin, which remains unregulated in Hong Kong. Consumers, especially those cooking for young children, may wish to diversify their flour sources or opt for brands that showed lower contaminant levels. The council also recommends checking for related tests on peanut butter, instant noodles, and beer—where similar issues have emerged.
For the full list of flour brands tested and their specific results, refer to the HKCC’s official report. As the debate over food safety continues, this investigation serves as a reminder that even pantry staples deserve scrutiny.