Course:FNH200/Projects/2024/Sourdough

From UBC Wiki

Introduction

Science of sourdough diagram

Sourdough acts as a cereal dough that can be used to produce various types of bread such as steamed bread or flatbread, with lactic acid bacteria and yeast acting as fermenting agents. Sourdough fermentation is considered to be one of the oldest food production processes dating back 14,000 years. [1] The unique fermentation process of sourdough leads to a more tangy taste compared to other leavened breads, and the crust has a slight bitter hint to it. [2]

Finished Sourdough
Cross section of sourdough
Baking dough

History and Cultural Significance

Sourdough was the first bread produced through natural leavening, with evidence of its use dating back to 2000 BC in ancient Egypt. Sourdough is thought to have been discovered when wild yeast settled into left out dough, resulting in bread with improved texture and flavor. [3] Sourdough is culturally significant across the world, representing culture and nourishment in ancient Greece, acting as a pillar in France’s culinary identity, and as a symbol of the miners strength during the California Gold Rush. [4]

Picture of sourdough starter

Types of Sourdough

There are 3 types of sourdough, each with their own production methods that lead to different sensory and functional properties. [5][6]

Type I:

  • Has no microbial starter, uses frequent backslopping of sourdough (using existing portions of a fermented dough for the next fermentation batch), is fermented with wild yeast for less than 24 hours below 30 degrees Celsius, and used in artisanal bread.
  • Rich in Fructilactobacillus sanfranciscensis.

Type II:

  • Fermented with commercial yeast at higher temperatures for a quicker build and a lower pH system, resulting in a mildly sour taste and more predictable baking outcomes.
  • Rich in Limosilactobacillus reuteri or Lactobacillus delbrueckii.

Type III:

  • Dried version of type II sourdough, allowing for easier transport.

How to Preserve Sourdough

Kneading sourdough

To preserve sourdough, lactic acid bacteria (LAB) is added to the sourdough mixture, which is capable of converting carbohydrate substrates into organic acids. LAB produces a wide range of organic acids such as acetic acid, lactic acid, and citric acid as the end product of fermented carbohydrates. Organic acids from LAB then lowers the pH of the environment, which helps inhibit the growth of pathogenic microorganisms and prevent spoilage. This fermentation process formed by the relationship between lactic acid bacteria and yeast, is also what contributes to the distinctive taste, texture, and nutritional profile of sourdough.

Fructilactobacillus sanfranciscensis is a type of LAB found in Type I sourdough that produces both lactic acid and acetic acid. Limosilactobacillus reuteri, which is often found in Type II, sourdough is known for producing reuterin, an antimicrobial compound, which can inhibit undesirable microbes, enhancing the microbial stability of the dough. Finally, lactobacillus delbrueckii is less common than the other two species but primarily produces lactic acid and is used with sourdough mixtures that contain some dairy products. [7]

Nutritional and Flavor Profile

On average, one medium slice of sourdough made from white flour and weighing 2 ounces contains the following nutritional content: [8]

  • Calories: 188
  • Carbs: 37 grams
  • Fiber: 2 grams
  • Protein: 8 grams
  • Fat: 1 gram
  • Selenium: 32% of the Daily Value (DV)
  • Folate: 21% of the DV
  • Thiamine: 21% of the DV
  • Niacin: 20% of the DV
  • Riboflavin: 17% of the DV
  • Manganese: 15% of the DV
  • Iron: 13% of the DV
  • Copper: 10% of the DV

Sourdough and regular whole wheat bread contain a good amount of minerals. However, our body’s ability to absorb these minerals are limited by the presence of phytic acid, also known as phytate. Phytate is known as an antinutrient because it binds with minerals, making it difficult for our digestive system to absorb. But because of sourdough's unique fermentation process, the lower pH environment produced deactivates the phytate by more than 70% compared to regular whole wheat bread. [9] Therefore, sourdough enables our body to absorb nutrients more effectively than regular bread.

The flavor behind sourdough varies depending on the sourdough starter used. The sourdough starter contains a variety of yeasts and LABs, affecting the final pH levels. Lower pH levels leave a sour taste, while higher pH levels leave behind a lighter tangy flavor. In addition, the temperature, fermentation period, and yeast also affect the lactic acid bacteria and consequently, the overall flavor.

Preparation Process

To make sourdough, following a proper preparation process under controlled conditions such as temperature and fermentation time is crucial in achieving optimal results. [10] To make a sourdough starter, you may follow the steps presented in this video.

Sourdough Bread Recipe:

  1. Combine the following into a bowl.
    • 250g water
    • 150g active sourdough starter
    • 25g olive oil
    • 500g bread flour
    • 10g fine sea salt
  2. Squish mixture until flour is fully incorporated and the dough feels dry, shaggy, and rough.
  3. Get plastic wrap and cover the bowl and let it rest for 30 to 60 minutes.
    • This will start developing the gluten before kneading.
  4. Knead the dough into a ball.
  5. Put the dough into an oiled bowl and then cover it and leave at room temperature.
    • Let it rest until it doubles in size (3-12 hours).
    • The time it takes is dependent on the room temperature, with warmer temperatures leading to more microbial activity from the culture, resulting in faster rising.
  6. Cut up the dough ball into the desired size and put it in an oven safe pot with parchment paper and leave for 30 to 60 minutes.
  7. Cut a slash down the center of the dough and cover the pot. Put it in the oven for 20 minutes at 400º F.
  8. Take out the pot, remove the lid, and put it in for another 40 minutes.
  9. Let bread cool on a wire rack for at least an hour before you slice and enjoy!

Science Behind Sourdough

The unique characteristics of sourdough stem from the microbial activity from lactic acid bacteria (LAB) and yeast, which interact with the flour components through fermentation.  The starter culture, when prepared correctly, has these 2 microorganisms present. LAB is responsible for creating lactic acid, acetic acid, amino acids, and peptides which greatly contribute to bread flavor and aroma. In addition, they breakdown carbohydrates like maltose which helps in the fermentation process. [11] Yeast is responsible for producing CO2 and ethanol, making the bread rise and giving the bread its airy texture. [11] These 2 microorganisms have a symbiotic relationship, stemming from their complex metabolic interaction, as yeast produces nitrogenous compounds and excess amino acids, which LAB uses to facilitate its growth. [12]

Sourdough vs Other Bread-Making Techniques

Sourdough differs from other bread-making methods in its fermentation process as it does not use baker’s yeast for quick leavening but instead uses a natural starter composed of wild yeast and lactic acid bacteria (LAB). This process takes longer, but produces a distinctive tangy taste due to the organic acids produced by LAB. Yeast-leavened bread on the other hand has a sweeter and milder flavor with a shorter preparation time, making it more suitable for commercial production. [3]

Another difference lies in the nutritional profile. Sourdough’s long fermentation process breaks down phytic acid in the flour, making minerals like iron and magnesium more bioavailable compared to other breads. [13]

Exam Question

Question: Which of the following contribute to the unique flavor profile of sourdough bread? (Select all that apply)

a) Lactic acid bacteria

b) Presence of gluten

c) Yeast fermentation

d) Maillard reaction

e) High sugar content

Answer: a) Lactic acid bacteria, c) Yeast fermentation, d) Maillard reaction

Explanation:

This question should be included on the final exam because it assesses understanding of lactic acid bacteria and yeast, which are essential microorganisms involved in influencing the flavor and texture of fermented products. It also tests understanding of the Maillard reaction, which contributes to the complex flavors and brown crust produced during baking. Together, these aspects are foundational to anyone looking for a career in food science.

References

  1. ↑ Gänzle, Michael G; Qiao, Nanzhen; Bechtner, Julia (2023 Dec 16). "The quest for the perfect loaf of sourdough bread continues: Novel developments for selection of sourdough starter cultures". Int J Food Microbiol. Check date values in: |date= (help)
  2. ↑ "What Should Sourdough Bread Actually Look Like?". The Pantry Mama.
  3. ↑ 3.0 3.1 Lau, Siew Wen; Chong, Ann Qi; Chin, Nyuk Ling; Talib, Rosnita A.; Basha, Roseliza Kadir (2021 Jun 23). "Sourdough Microbiome Comparison and Benefits". National Library of Medicine. Check date values in: |date= (help)
  4. ↑ "The History of Sourdough Bread Across Cultures". TEXAS Real FOOD.
  5. ↑ Garcia-Vaquero, Marco; Rocha, João Miguel F. (31 July 2023). Sourdough Innovations. Boca Raton: CRC Press. ISBN 9781003141143.
  6. ↑ Calvert, Martha D.; Madden, Anne A.; Nichols, Lauren M.; Haddad, Nick M.; Lahne, Jacob; Dunn, Robert R.; McKenney, Erin A. (2021 May 10). "A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research". National Library of Medicine. Check date values in: |date= (help)
  7. ↑ Ceresino, Elaine Berger; Juodeikiene, Grazina; Schwenninger, Susanne Miescher; da Rocha, João Miguel Ferreira (2024). Sourdough Microbiota and Starter Cultures for Industry. Springer.
  8. ↑ Petre, Alina (2023 May 19). "How Healthy Is Sourdough? How to Make It and More". healthline. Check date values in: |date= (help)
  9. ↑ Ma, Sen; Wang, Zhen; Guo, Xingfeng; Wang, Fengcheng; Huang, Jihong; Sun, Binghua; Wang, Xiaoxi (2021 May 10). "Sourdough improves the quality of whole-wheat flour products: Mechanisms and challenges-A review". National Library of Medicine. Check date values in: |date= (help)
  10. ↑ Raffa, Emilie (January 3, 2014). "Sourdough Bread: A Beginner's Guide". The Clever Carrot.
  11. ↑ 11.0 11.1 Pérez-Alvarado, Omar; Zepeda-Hernández, Andrea; Garcia-Amezquita, Luis Eduardo; Requena, Teresa; Vinderola, Gabriel; García-Cayuela, Tomás (2022). "Role of lactic acid bacteria and yeasts in sourdough fermentation during breadmaking: Evaluation of postbiotic-like components and health benefits". Frontiers in Microbiology.
  12. ↑ "Yeast Creates a Niche for Symbiotic Lactic Acid Bacteria through Nitrogen Overflow" (PDF). Elsevier Inc. October 25, 2017. line feed character in |title= at position 48 (help)
  13. ↑ Z, Alkay; F, Falah; H, Cankurt; E, Dertli (31 May 2024). "Exploring the Nutritional Impact of Sourdough Fermentation: Its Mechanisms and Functional Potential". Europe PMC.
Retrieved from "https://wiki.ubc.ca/index.php?title=Course:FNH200/Projects/2024/Sourdough&oldid=846415"