Bread is basically wheat kernels crushed and mixed with water then heated. There are two primary types of wheat, Common and Durum, and two types of bread, leavened and flat. Wheat has been cultivated for over 10,000 years, originating in the Fertile Crescent of the Middle East.

Composition and nutrients Link to the Composition and nutrients heading

A wheat kernel is composed of three parts: the bran, germ, and endosperm. The protein content of wheat is crucial as it indicates the potential for gluten formation, which arises from the interaction of two specific proteins. Generally, the protein content in wheat correlates directly with the hardness of the kernel.

Protein? In wheat? The majority of wheat protein is gluten and gluten is considered an incomplete protein because it lacks essential amino acids, particularly lysine. Gluten is also 10% less digestible than meat protein, because it resists digestive enzymes and has tighter chemical bonds than meat.

• The bran makes up 14.5% of the kernel’s weight

  • Insoluble fiber, B vitamins, trace minerals, and some protein.

• The germ accounts for 2.5% of the kernel’s weight

  • Unsaturated fats, B vitamins, antioxidants, trace minerals, and phytochemicals.

• The endosperm is 83% of the kernel’s weight

  • Starch and protein, with small amounts of B vitamins, iron, and soluble fiber.
  • Flours that aren’t “whole wheat” only use this portion.

Anti-nutrients Link to the Anti-nutrients heading

Wheat contains anti-nutrients which affect bioavailabity and absorption of nutrients:

• Phytic Acid (Phytates):

  • Wheat is 0.39-1.35% phytic acid by weight, highest concentration in the bran.
  • Forms insoluble complexes with iron, zinc, magnesium, and calcium, reducing their absorption.
  • Fermentation and baking can reduce levels, but a significant amount remain.

• Wheat Germ Agglutinin (WGA):

  • 0.01-0.05% of the total protein content in wheat.
  • Binds to the digestive tract lining, potentially causing discomfort and reducing nutrient absorption.
  • Heat-stable and resistant to digestive enzymes.

• Amylase-Trypsin Inhibitors (ATIs):

  • ATIs represent approximately 2-4% of the total wheat protein.
  • Inhibit amylase and trypsin enzymes, reducing starch and protein digestion and absorption.
  • Heat-stable and resistant to digestive enzymes.

• Tannins:

  • Tannin content in wheat ranges from 0.05-0.46% by weight.
  • Bind to proteins and minerals (iron, zinc, calcium), reducing their absorption.
  • Somewhat heat-stable and are resistant to digestive enzymes.

• Saponins:

  • Levels ranging from 0.06-0.33%.
  • Form insoluble complexes with minerals such as iron and zinc.
  • Heat-stable and resistant to digestive enzymes.

Types of wheat Link to the Types of wheat heading

Common Wheat Link to the Common Wheat heading

Triticum aestivum, makes up 95% of wheat production worldwide.

• Cultivars and Hardness: Includes numerous cultivars, often distinguished by their hardness.
• Use and Characteristics: Common wheat is also known as bread wheat, and is used to make most types of flour.

Durum Wheat Link to the Durum Wheat heading

Triticum turgidum ssp. durum, responsible for the other 5% of global wheat production.

• Cultivars and Hardness: Also has many cultivars, including landrace. Durum literally means hard in latin and is a very hard wheat, so its cultivars aren’t typically distinguished by their hardness.
• Use and Characteristics: Typically used for pasta and flat bread. Semolina and bulgur wheat are common uses. Durum is also often used for Atta flour, though not exclusively, which is used for flat breads.

Flour Link to the Flour heading

The transformation of wheat into flour involves milling and aging. The aging process allows the proteins to strengthen and the absorbency to normalize, mostly due to oxidation. Before aging flour inconsistently absorbs water and has “weak” protein thus poor gluten formation.

• Enrichment became a common practice in the 1930s in America, and refers to adding shelf stable nutrients (think multivitamins) to refined flours.
• Refined flour refers to removing the bran and germ. Refined flour has a longer shelf life.
• Bleaching flour is done to chemically age it. It also increases its shelf life and breaks down the starches and proteins making it softer and more absorbent.
• Whole wheat flour uses the whole kernel, bran germ and endosperm.
• Different types of flour, e.g. bread, all purpose, desert, etc. typically are differentiated by their protein content and this is achieved by mixing different cultivars, hard and soft, in order to achieve a desired protein content and thus amount of gluten formation.

Bread Link to the Bread heading

Flat Link to the Flat heading

Flat bread is typically denser and maintains a nutrient profile consistent with its flour base. It is typically made from flour, salt and water. Some flat bread contains butter, oil or ghee. Types of flatbread are often differentiated by the cooking method. Flat bread does contain gluten, butt not all of them allow time for the gluten to form before cooking.

Leavened Bread Link to the Leavened Bread heading

Leavened bread refers to dough that “rises” by inflating gluten pockets with air. This phenomenon can occur via several methods, each contributing uniquely to the bread’s texture and flavor.

The Methods of Leavening

1. Yeast Fermentation: The most common leavening method involves adding a yeast culture to the dough. Typically Saccharomyces cerevisiae is used, often called baker’s or brewer’s yeast.

2. Sourdough Starter: A traditional technique, sourdough bread relies on a mix of wild yeast and lactic acid bacteria from the environment. It uses a “starter,” a portion of previously fermented dough, to initiate fermentation.

3. Chemical Leavening: Less commonly, chemical agents like baking powder or soda are used to generate carbon dioxide (CO₂) through a chemical reaction. This method differs significantly from fermentation.

Yeast Fermentation

Yeast fermentation is notable not just for its leavening capabilities but also for its impact on nutrition and flavor:

• Nutrient Availability: Fermentation makes nutrients more accessible, creating B vitamins, antioxidants, and amino acids in the process.

• Reduced Glycemic Index: By consuming some of the carbohydrates, yeast lowers the bread’s glycemic index, beneficial for controlling blood sugar levels.

• Breaking Down Phytate: Yeast also tackles phytate, an anti-nutrient that impedes the absorption of other nutrients in bread.

• Adding flavor: The alcohol created by yeast remains in the bread and affects its flavor, bread can be up to 2% alcohol.

Sourdough fermentation

Sourdough stands apart due to its complex fermentation process, involving not just yeast but a diverse community of bacteria:

• Lactic Acid Bacteria: These bacteria produce lactic acid, acting as a natural preservative and imparting health benefits. They are more effective than yeast in breaking down phytates, enhancing the bioavailability of nutrients.

• Protein and Gluten Breakdown: The presence of lactic acid facilitates the breakdown of proteins and gluten in flour, making sourdough potentially easier to digest.

• Impact on Glycemic Index: Research indicates that sourdough can reduce the bread’s glycemic index by up to 30%, probably more effectively than yeast fermentation alone.

• Adding flavor: On top of the alcohol from yeast the lactic acid also affects the flavor, hence the name sour dough.

Resources Link to the Resources heading

• Sourdough study

  • vitamins and antioxidants mentioned

• Sourdough fermentation study

  • glycemic index mentioned

• Phytate study

  • mentions sourdough reducing them more

• Phytate as anti-nutrient study

• Schlemmer, U., Frølich, W., Prieto, R. M., & Grases, F. (2009). Phytate in foods and significance for humans: food sources, intake, processing, bioavailability, protective role and analysis. Molecular Nutrition & Food Research, 53(S2), S330-S375.

• Matucci, A., Veneri, G., Dalla Pellegrina, C., Zoccatelli, G., Vincenzi, S., Chignola, R., … & Rizzi, C. (2004). Temperature-dependent decay of wheat germ agglutinin activity and its implications for food processing and analysis. Food Control, 15(5), 391-395.

• Zoccatelli, G., Sega, M., Bolla, M., Cecconi, D., Vaccino, P., Rizzi, C., … & Chignola, R. (2012). Expression of α-amylase inhibitors in diploid Triticum species. Food Chemistry, 135(4), 2643-2649.

• Žilić, S. (2013). Wheat Gluten: Composition and Health Effects. In P. R. Shewry & S. J. Hey (Eds.), Health Implications of Wheat Gluten (pp. 71-86). Royal Society of Chemistry.

• Lásztity, R. (1984). The Chemistry of Cereal Proteins (1st ed.). CRC Press.

• Önning, G., & Asp, N. G. (1995). Effect of oat saponins and different types of dietary fibre on the digestion of carbohydrates. British Journal of Nutrition, 74(2), 229-237.

• Wieser, H. (2007). Chemistry of gluten proteins. Food Microbiology, 24(2), 115-119.