Folates in bread: retention during bread-making and in vitro bioaccessibility

Area of Science:

• Nutritional biochemistry
• Food science
• Human health

Background:

• Bread is a significant source of folates in many diets.
• Bread production leads to substantial losses of both endogenous folates and added folic acid.
• The bread matrix may impede folate absorption.

Purpose of the Study:

• To quantify folate retention during bread-making.
• To evaluate in vitro folate bioaccessibility from bread and a breakfast meal.
• To assess in vitro folate uptake using cellular models.

Main Methods:

• Fortified wholemeal breads were prepared with folic acid and [6S]-5-methyl-tetrahydrofolate.
• Folate retention was measured at dough, proofing, and bread stages.
• In vitro bioaccessibility was assessed using the TNO gastrointestinal model (TIM).
• In vitro folate uptake was evaluated using Caco-2 cells and stable isotopes.
• Folate content was quantified using liquid chromatography-mass spectrometry (LCMS).

Main Results:

• Bread-making caused 41% loss of endogenous folates and up to 25% loss of folic acid, but 65% loss of [6S]-5-methyl-tetrahydrofolate.
• In vitro bioaccessibility was 75% for endogenous bread folates and 94% for breakfast meal folates (TIM model).
• Relative folate uptake into Caco-2 cells from [6S]-5-methyl-tetrahydrofolate-fortified bread was 71% compared to a standard solution.

Conclusions:

• Folic acid fortification demonstrated higher retention during bread-making compared to [6S]-5-methyl-tetrahydrofolate.
• The bread matrix appears to inhibit in vitro folate bioaccessibility.
• Folate bioaccessibility from a breakfast meal was nearly complete, contrasting with bread.