The type of processing also influences the level of provitamin A retention in maize.
During both milling and processing, biofortified maize hybrids showed good levels of retention of provitamin A carotenoids when using apparent retention values .
Boiled cassava roots retain 56 to 100% of provitamin A content .
Screening of cassava accessions from the International Center for Tropical Agriculture (CIAT) germplasm collection found a range of 0-19 ppm of provitamin A in existing cassava varieties, exceeding the breeding target of 15 ppm [33, 34].
Breeding programs for provitamin A cassava are based at CIAT and the International Institute of Tropical Agriculture (IITA).
Three first-wave provitamin A cassava varieties with 6-8 ppm of provitamin A (about 50% of the target) were released in 2011 in Nigeria.
Two forms of vitamin A are available in the human diet: preformed vitamin A (retinol) and provitamin A carotenoids.
Setting Provitamin A Target Levels for Maize Breeders and Establishing Nutritional Efficacy
As discussed, targets are based on age- and gender-specific nutrient requirements; daily consumption amounts of maize and maize products; nutrient retention after traditional storage, processing, and cooking; and the bioavailability of provitamin A in maize, that is, the degree to which the human body can absorb provitamin A from maize and convert it to retinol, the form of vitamin A used by the body.
Although the richest sources of preformed vitamin A in the Nigerian diet are animal-based (for example, liver, dairy products, fish oils, and eggs), the most common sources of the nutrient are provitamin A carotenoids, including beta-carotene, from orange and yellow fruits and vegetables (pumpkin, yellow squash, carrots, yellow sweet potatoes, green leafy vegetables, mango, papaya, and other local carotene-rich fruits), some of which are highly seasonal in availability .
Setting Provitamin A Target Levels for Cassava Breeders and Establishing Nutritional Efficacy
As discussed, vitamin A target levels for plant breeders are based on age- and gender-specific nutrient requirements, daily consumption amounts of cassava and cassava products, nutrient retention after traditional storage, processing, and cooking, and the bioavailability of provitamin A in cassava, that is, the degree to which the human body can assimilate provitamin A from cassava and convert it to retinol.