On the Rise: Using Minitab to Assess How Bran Influences Phytic Acid in Bread

The last time you ate bread, perhaps you checked how much fiber was in a slice—but did you think about how much phytic acid it contained? You’re not alone. Nearly every culture in the world eats bread, but few people consider the potential risks and benefits associated with the phytic acid it contains.

Thanks to a team of researchers at several universities in Turkey, they may not have to.

The team recently used Minitab Statistical Software to study the interactions between the main ingredients in bread and the effect they have on its phytic acid level. Their findings, detailed in the Turkish Journal of Field Crops, may give bakers more control over bread’s nutritional value.

Phytic acid—which is found in grains, legumes, and nuts—has numerous health benefits. But the compound’s antioxidant properties, and abilities to reduce excessive amounts of iron and decrease the risk of colon cancer, are sometimes overshadowed by its capacity to inhibit mineral absorption.

As more people learn that insufficient dietary fiber can lead to diseases, the demand for high-fiber foods is rising. In response, bakers enriched their bread by increasing the amount of bran in their recipes—a change that also boosts the amount of phytic acid the bread contains.

So how can bakers give people the higher-fiber bread they want while keeping phytic acid levels at an acceptable level?

Scientists at Baskent, Gazi, and Ankara Universities in Turkey decided to investigate the best way to manipulate the bread-making process to suit nutritional needs.

The team used Minitab Statistical Software and a statistical technique called Design of Experiments to measure the effect of input variables (wheat bran, yeast, and fermentation time) on phytic acid. Specifically, they employed a Box-Behnken design (BBD), a type of “response surface design” widely used in industry to find optimal levels for input variables based on experimental data.

In their experiments, the researchers set three levels for each input variable. They held one factor at the center level while applying different combinations of levels for the other variables, and measured the effects of each combination on phytic acid level. They then repeated the process with each of the remaining two factors held at the center level. The experimental design they selected let them collect the data they needed with the lowest number of experimental runs, while still representing all possible factor combinations.

The analysis of a response surface design typically includes graphs that reveal how different levels of the input variables affect the outcome. When the Turkish scientists analyzed their data and looked at the graphs created by Minitab, they discovered that the amount of bran and fermentation time influenced the level of phytic acid, while the amount of yeast, either alone or in any interaction, did not affect it significantly.

A contour plot lets you visualize the effects of two predictor variables on a response variable. In the plot below, the predictors Fermentation Time and Yeast Amount appear on the X-Y axes, and the different color bands represent the amount of phytic acid in the resulting bread when the percentage of wheat bran in the flower is held at 10%.

Bread Contour Plot

Their analysis indicates that the amount of phytic acid increases or decreases proportionately with the amount of wheat bran added. Applying the optimal fermentation time—which they found to be 60 minutes—after selecting the wheat type with the lowest phytic acid content, produces bread that balances the compound with the desired nutrition.

The results of their work may not bring phytic acid into broad consumer awareness in the same way people know about fiber, fat, and carbohydrates. But as bread companies build on their research fine-tune their own formulations, the hope is that most of us will never need to worry about the amount of phytic acid in one of the world’s most popular foods.

This story was adapted from an article published in the 2012 issue of the Turkish Journal of Field Crops.

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