Phytic bread

Generally, vegetable food protein ingredients are more absorbant than other dough components, with the result that mixing time and loaf volume is decreased. In addition, pan bread crumb becomes coarser and occasionally darker in color. Negative effects on loaf volume appear to be inversely related to phytic acid content. 

To study the effect of phytic acid, calcium and protein in bread meals in various combination, on the zinc absorption in man. 

When adding animal protein in the form of milk, egg and cheese to the whole flour meal, the zinc absorption was increased. (Table II). It seems like the binding of zinc to phytic acid and fibercomponents is overcome if enough animal protein is served together with the whole flour bread. 

In animal experiments it has been shown that a high calcium content in combination with the phytic acid in whole flour bread will decrease the zinc absorption (10), When adding milk and milk products to the whole flour bread in Dr. Sandstr0ms experiments the same positive effect was seen from the protein despite of the higher calcium content (Table III). 

It is possible that the protein competes with the binding to phytic acid or fiber comnonents in whole flour bread rather than facilitating zinc absorption. 

By increasing the fermentation period when making the dough for the bread, the decreased zinc absorption in whole flour bread can be overcome. The phytic acid is in this way broken down, and the zinc better available absorption. 

In human studies done with leavened and unleavened whole grain bread (7, 19), the conclusions drawn were the same to those drawn for animal studies. The importance of phytic acid was later questioned by the same authors and decreased absorption was described to the fiber content in the diets (20). A negative... 

Zinc deficiency has been found among peasant populations in rural areas of the Middle East. Unleavened whole wheat bread can account for 75% of the energy intake in these areas, that is, Iran, Egypt, and Turkey. This diet, which does not contain meat, does contain zinc, but it also contains phytic acid at a level of about 3 g/day. The phytic acid inhibits zinc absorption. The yeast used to leaven bread produces phosphatases that hydrolyze the phosphate groups from phytic acid. 

In his Natural History (1826), Pliny the Elder stated that those persons who are dieted npon fermented bread are stronger in body , which is an early statement on the health benefits of sourdough breads. Whole meals of cereals are a good source of minerals. Their bioavailability is limited, as they are often bound to phytic acid (myo-inositol-hexophospate). Wheat and rye contain about 1.2% of dry matter (Fretzdorff Briimmer, 1992). With the drop in pH during sourdough fermentation, endogenous phytases of the cereals are activated and the bound minerals are released (Fretzdorff Briimmer, 1992). Lactic acid bacteria and yeasts also possess phytase... 

Fretzdorff, B., Brllmmer, J.-M. (1992). Reduction of phytic acid during breadmaking of whole-meal breads. Cereal Chemistry, 69, 266-270. 

Controversy has been raging for many years as to whether, from the nutritional point of view, white or brown bread is better. Brown bread made from high extraction flour contains more protein, calcium, iron, B vitamins and fibre than white bread but its nutrients tend to be less well digested and absorbed. The case for white bread is based on its more attractive appearance, finer texture, better baking and keeping qualities and also its lower content of fibre and phytic acid which are responsible for the poorer utilization of nutrients. In Britain, where bread is only one of many articles of diet, nutritional differences between wholemeal and fortified white flours are of little practical significance. However, such differences could become important if bread ever became the single staple food. 

Diets based on unleavened wheat bread contain a relatively large amount of phytic acid (inositol hexaphosphate), which can bind calcium, iron and zinc to form insoluble complexes that are not absorbed. Phytases in yeast catalyse dephosphorylation of phytate to products that do not chelate the minerals. 

Should the Government ensure that the flour should be as nutritious as possible For instance, should ascorbic acid and zinc be added as well as a variety of other nutrients Bread has been used as a vehicle for nutrients not removed from it iodised salt in goitrous areas of the Netherlands since 1943 and Australia since 1953 sodium chloride to combat prostration in the Armed Forces from sweating in very hot conditions calcium, partly to offset the phytic acid in flours of higher extraction and partly as a supplement. There is no objection to these practices anyone who objects to, for instance, the calcium can use wholemeal flour to which no nutrients are artificially added. But to strive to make flour as nutritious as possible would be unreasonable. 

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