Abstract
BACKGROUNDZinc‐biofortified rice could contribute to zinc intake in deficient populations, but processing it into parboiled rice could affect this potential benefit. Zinc and iron true retention (TR) in milled rice produced under conditions resembling household and commercial parboiled methods was evaluated. Zinc and iron TR in milled rice obtained from biofortified and non‐biofortified rice subjected to different soaking temperatures during parboiling was also evaluated.RESULTSConditions resembling commercial parboiling methods resulted in 52.2–59.7% zinc TR and 55.4–79.1% iron TR, whereas those used for household parboiling resulted in 70.7–79.6% zinc TR and 78.2–119.8% iron TR. Zinc TR in milled (8–16% bran removal) biofortified and non‐biofortified parboiled rice was 50.6–66.8% when soaking rough rice at 20 °C and 29.9–56.0% when soaking rough rice at 65 °C; both had lower zinc TR than non‐parboiled rice (58.0–80.6%). Iron TR was generally similar between milled non‐parboiled and parboiled rice (26.2–67.6%) and between parboiled biofortified and non‐biofortified milled rice.CONCLUSIONParboiling conditions used to obtain milled rice targeted for own household consumption resulted in higher zinc and iron TR compared to parboiling conditions used for milled rice targeted for markets. More zinc from the inner endosperm moved towards the outer layers at high soaking temperature, resulting in lower zinc TR for milled parboiled rice soaked in hotter water. Parboiled rice soaked at temperatures used in households could provide more zinc to diets compared to rice soaked in hotter water commonly used in large rice mills, especially when rice is extensively milled. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Highlights
Zinc deficiency in South Asia exceeds 25%, mainly due to reliance on staple foods with low zinc content such as rice and wheat.[1]Moderate zinc deficiency can result in clinical problems including growth retardation, cognitive impairment, cell-mediated immune dysfunctions and lack of appetite.[2]
Conditions resembling commercial parboiling methods resulted in 52.2–59.7% zinc true retention (TR) and 55.4–79.1% iron TR, whereas those used for household parboiling resulted in 70.7–79.6% zinc TR and 78.2–119.8% iron TR
Rough rice parboiled in households or in small and medium commercial mills (SMED) is commonly soaked at room temperature for several hours, whereas in automated rice mills’ (ARM) it is soaked in hot water to accelerate water absorption (60–80 °C for 4–8 h)
Summary
Zinc deficiency in South Asia exceeds 25%, mainly due to reliance on staple foods with low zinc content such as rice and wheat.[1]Moderate zinc deficiency can result in clinical problems including growth retardation, cognitive impairment, cell-mediated immune dysfunctions and lack of appetite.[2]. In Bangladesh and India – the countries that produce the most parboiled rice and where biofortified rice is available – parboiling is done in households, small and medium commercial mills (SMED) and large mills called ‘automated rice mills’ (ARM).[3,4,5,6] Parboiling is done usually by soaking, steaming and drying rough rice. Zinc-biofortified rice could contribute to zinc intake in deficient populations, but processing it into parboiled rice could affect this potential benefit. Zinc and iron true retention (TR) in milled rice produced under conditions resembling household and commercial parboiled methods was evaluated. Zinc and iron TR in milled rice obtained from biofortified and non-biofortified rice subjected to different soaking temperatures during parboiling was evaluated
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