Elemental composition of Malawian rice.

Area of Science:

• Agricultural Science
• Food Science
• Nutritional Science

Background:

• Malawi faces widespread dietary deficiencies in calcium (Ca), iron (Fe), iodine (I), selenium (Se), and zinc (Zn).
• High phytic acid (PA) consumption can worsen mineral deficiencies.
• Rice (Oryza sativa) is a staple in some Malawian populations, making its mineral content crucial for food security.

Purpose of the Study:

• To determine the mineral composition of rice from Malawian farmers' fields and markets.
• To assess levels of essential minerals and potentially toxic elements in rice.
• To evaluate the impact of phytic acid on mineral bioavailability.

Main Methods:

• Rice samples (21 white, 33 brown) were collected from 18 extension planning areas in Malawi.
• Elemental analysis was performed using inductively coupled plasma-mass spectrometry (ICP-MS).
• Arsenic speciation utilized high-performance liquid chromatography (HPLC)-ICP-MS, and phytic acid was quantified via a PA-total phosphorus assay.

Main Results:

• Brown and white rice had median Ca (66.5, 37.8 mg/kg), Fe (22.1, 7.2 mg/kg), Se (0.025, 0.028 mg/kg), and Zn (17.0, 14.4 mg/kg).
• Median phytic acid concentrations were 5438 mg/kg in brown rice and 1906 mg/kg in white rice, with high PA:Zn molar ratios.
• Potentially toxic elements like arsenic (As), cadmium (Cd), and lead (Pb) were found at low concentrations, with minimal risk.

Conclusions:

• Malawian rice, similar to maize, is deficient in Ca, I, Se, and Zn, failing to meet dietary requirements.
• Biofortification strategies hold potential for increasing Se and Zn concentrations in rice.
• Concentrations of Fe varied significantly, likely due to soil contamination; risks from toxic elements in rice are minimal.