Carey et al. 2015 — Percolating cooking water reduces iAs in rice by up to 85%
Carey et al. tested 41 rice samples of diverse geographic origin — UK (multiple varieties), US, India, Pakistan, Bangladesh — for inorganic arsenic (iAs) content before and after three cooking methods: the conventional absorption method (limited water, fully absorbed), the high-volume water method (excess water, drained), and a percolating/filter method (continuous water flow through a filter during cooking). The central finding is that the percolating cooking method reduced iAs by 50–85% compared to raw grain, substantially outperforming the conventional absorption method (which retains most grain iAs) and the high-volume-water drain method (which reduces iAs by approximately 30%). The study is directly relevant to infant feeding because rice-based infant foods are a primary iAs exposure route for infants, and cooking method is a consumer-controllable mitigation lever.
Key numbers
- 41 rice samples tested (diverse origins: UK, US, India, Pakistan, Bangladesh)
- Raw grain iAs range: approximately 40–200 µg/kg (dry weight, varies by variety and origin)
- Conventional absorption cooking: retains approximately 90% of raw grain iAs
- High-volume water drain method: retains approximately 70% of raw grain iAs (approximately 30% reduction)
- Percolating/filter method: retains approximately 15–50% of raw grain iAs (50–85% reduction)
- iAs measured by HPLC-ICP-MS; total As cross-verified
- Highest raw iAs samples: Bangladeshi and US long-grain varieties; lowest: Indian basmati
Methods (brief)
Laboratory cooking experiment; HPLC-ICP-MS for speciated As; samples sourced from UK retail markets representing multiple geographic origins; three cooking protocols compared; n=41 rice samples across varieties and origins.
Implications
Certification: Cooking method is a meaningful mitigation factor that could be incorporated into product-level guidance for rice-based infant foods. Courses: Key teaching point — processing method substantially affects consumer exposure independently of raw material iAs content. Geographic origin effects on raw iAs are well-established; this adds a processing-method dimension. App: As-consumed iAs estimates from raw grain values require a cooking-method adjustment factor; this study provides the adjustment basis.