Effect of food processing and preparation on mineral utilization.

While effects of various nutrients and certain non-nutrient components of food on mineral utilization have been intensively studied, less is known about the effects of food processing and preparation procedures. Fermentation during the production of beer, wine, yogurt, and African tribal foods affects bioavailability of Zn and Fe. Baking affects the chemical form of Fe in fortified bread products and these changes can affect its bioavailability. Availability of Fe in milk-based infant formula depends on whether Fe is added before or after heat processing. Food packaging (e.g., tin cans) can alter food composition and thus potentially affects mineral bioavailability. Maillard browning has been reported to cause slight decreases in Zn availability both in vitro and in humans. However, we found that feeding of highly browned casein-glucose products to rats as 5% of diet produced no effect on Zn absorption (59.5 +/- 8.2% vs 54.1 +/- 7.3%) or Fe absorption (45.6 +/- 7.7% vs 46.9 +/- 12.6%) for browned vs control, respectively; nor did we find any of the adverse health effects reported by others. We found no effect on stable Zn or Cu absorption in seven men when browned foods were fed, compared to the same diets without browning. Zinc absorption was 34 +/- 13% (browned) vs 24 +/- 15% (unbrowned), and Cu absorption was 55 +/- 5% vs 55 +/- 8% (p greater than 0.05).