Methods that can reduce the phytate content of cereals while maintaining the maximum amount of micronutrients would be most beneficial, and these include soaking, fermentation, and germination/malting, as described below. In some industrialized countries, milled cereal flours are enriched to compensate for the micronutrients lost. Hence, bioavailability of iron, zinc, and calcium may be enhanced, although the content of minerals and some vitamins of these pounded cereals is simultaneously reduced. Household pounding is used to remove the bran and/or germ from cereals, which in turn may also reduce their phytate content when it is localized in the outer aleurone layer (e.g., rice, sorghum, and wheat) or in the germ (i.e., maize) ( 9).
To minimize the oxidation of carotenoids and loss in cooking water, shorter cooking times and use of steaming rather than boiling are recommended ( 8). However, whether such improvements in bioavailability compensate for the losses in activity of heat-labile and water-soluble vitamins (e.g., thiamin, riboflavin, vitamin C, folate) remains to be determined. Thermal processing can also enhance the bioavailability of thiamin, vitamin B-6, niacin, folate, and carotenoids by releasing them from entrapment in the plant matrix ( 6, 8). There is some evidence that boiling of tubers ( 5, 6) and blanching of green leaves ( 7) induce moderate losses (i.e., 5–15%) of phytic acid.
Thermal processing may improve the bioavailability of micronutrients such as thiamin and iodine by destroying certain antinutritional factors (e.g., goitrogens, thiaminases), although whether it degrades phytate, a potent inhibitor of iron, zinc, and calcium absorption, depends on the plant species, temperature, and pH. These methods have been discussed in detail elsewhere ( 5) and are summarized briefly below. These methods include thermal processing, mechanical processing, soaking, fermentation, and germination/malting. Several traditional food-processing and preparation methods can be used at the household level to enhance the bioavailability of micronutrients in plant-based diets. A variety of interventions that are appropriate for the rural poor need to be considered to overcome these limitations. Given the heavy reliance of low-income populations on cereals as a food source, the negative effects of low mineral bioavailability on mineral status and subsequent health are potentially quite substantial. The low bioavailability of nutrients, arising from the presence of antinutrients such as phytate, polyphenols, and oxalate, is another factor that limits the quality of predominantly plant-based diets ( 3, 4). In resource-poor communities, it has become clear that malnutrition is attributable not solely to insufficient amounts of food but also to the poor nutritional quality of the available food supply ( 1, 2), particularly among plant-based diets containing only small amounts of micronutrient-dense animal-source foods. The suitability of these strategies and their impact on nutritional status and functional health outcomes need to be more broadly assessed.
#Who created food processing methods plus#
A long-term participatory intervention in Malawi that used a range of these strategies plus promotion of the intake of other micronutrient-rich foods, including animal-source foods, resulted in improvements in both hemoglobin and lean body mass and a lower incidence of common infections among intervention compared with control children. A combination of strategies is probably required to ensure a positive and significant effect on micronutrient adequacy. These strategies aim to increase the physicochemical accessibility of micronutrients, decrease the content of antinutrients, such as phytate, or increase the content of compounds that improve bioavailability. These include thermal processing, mechanical processing, soaking, fermentation, and germination/malting. Several traditional household food-processing and preparation methods can be used to enhance the bioavailability of micronutrients in plant-based diets. One aspect of dietary quality with respect to adequacy of micronutrient intakes is bioavailability. Dietary quality is an important limiting factor to adequate nutrition in many resource-poor settings.
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