About My Experiment

A sourdough, essentially, is a mixture of even parts flour and water. Through time and “feeding” of more flour and water, the mixture will house yeasts, usually Saccharomyces cerevisiae and its relatives, alongside lactobacilli bacteria and its relatives. These bacteria can outnumber yeasts by a hundred to one! The yeasts and bacteria that develop in the mixture are found naturally in the air, flour, and on the humans baking the sourdough.

The Lactobactillus genus can possess probiotic properties, and their ability to produce acids, such as lactic acids, are useful in fermentation. The bacteria contribute carbon dioxide and aromatics to the starter, providing the smells and flavor associated with sourdough.

A sourdough starter is marked by its ability to perform fermentation. This is observed in the ability to convert sugars from the flour into products, such as carbon dioxide, acids, and ethanol. The carbon dioxide bubbles become trapped in the gluten formed by the sourdough, and creates the air bubbles we observe in the bread.

Additionally, microbe diversity and flavor can also come from the hands of sourdough bakers, differing due to individual skin microbiomes.

Lactobacilli, or lactic acid bacteria, are significantly smaller than yeasts, and can be found on the skin of fruits. They have the ability to lower the pH of the sourdough starter to 3.5. This creates the characteristically “sour” flavor of the bread.

For the core of my experiment, the type of lactobacilli I would like to produce are known as homofermentative LAB. These thrive in temperatures between 30-35 degrees Celsius. However, the lower-temperature types of bacteria, known as heterofermentative, are more likely to be produced due to constrictions of resources. These bacterium prefer temperatures between 15-22 degrees Celsius.

Sourdough bread, in itself, is considered one of the healthiest breads available. It possesses a significant mineral composition, antioxidants, fiber, and vitamins. It also has low phylate levels, which enables the human body to absorb nutrients more easily. The prebiotic and probiotic content of sourdough can improve intestinal health. Its fermentation also degrades gluten more than traditional Saccharomyces cerevisiae does alone, which makes it kinder to those with digestive issues pertaining to gluten. Alongside all of these qualities, sourdough possesses a diverse flavor and texture profile that can be developed almost anywhere.

While there is naturally flour and water in many cultures of the world, not all cultures have the time it takes to commit and develop sourdough bread. The typical starter takes around 5 days of commitment, feeding every 24 hours and then progressing to 12 hour intervals. It is easy to see why an individual might opt for a commercial packaged yeast to bake their bread.

However, this is also not a readily available option for all communities. Supermarkets in India have been reported to have dry yeast that doesn’t rise or dilute correctly, making baking difficult. Fresh yeast must be preserved in the freezer in order to last.

India has been rapidly increasing in population for decades, going from a population of under 400 million in 1950 to the most populated continent in the world, currently holding over 1.38 billion inhabitants. In 2017, 14.5% of the population was considered to be chronically undernourished. That totals to 194 million hungry people living without reliable access to food.

Finding an way to enable individuals in India to create sourdough starters more easily with materials they may throw away would sustainably impact the lives of those who would utilize this new method. The Indian city Mumbai holds largest population living in slums worldwide. This city also holds temperatures with a mean of 28 degrees Celsius annually between 1985-2015, with monthly high temperatures always at least 31 degrees Celsius. As the homofermentative LAB mentioned previously often prefer this  warmerclimate, this lactobacilli would thrive within this city.

A fruit that is heavily produced in India is the lychee. While this plant is difficult to produce in some climates, India is the fourth largest lychee producer in the world, with 90,000 tons each year. As reference to this statistic, the United States is the ninth largest lychee producing country, yet only produces 500 tons annually. As recently as August 24, 2020, reports have predicted millions of dollars of growth in the production of lychee honey to a global market, meaning the peels will become more readily available in the form of waste for potential use.

Within India, the lychee fruit can be a point of controversy, as it contains poisonous toxins if eaten unripe. 47 Indian children were recorded to have died in 2019 due to acute encephalitis syndrome. The disease is currently being studied for its potential association within the toxins of unripe lychees. Rises of the disease have also been noted to coincide with lychee seasons since 1995. Due to potential correlations between the AES and lychees, the fruit is currently a topic of study. Lychees, when combined with malnourishment, can block the natural production of sugar in our bodies.

The lychee fruit possesses a spiky peel classified as inedible, with no commonly regarded applications in cooking or baking. As this textured exterior comes in contact with the external environment, there is a high potential for natural bacteria and yeasts to be caught and carried on a lychee peel.

In 2010, the peel was been found to adsorb effluent discharge and dyes. This reveals the lychee peel’s potential to carry external substances on its peel. Additionally, in 2018, the lychee peel reaction to different antibiotics was observed, ultimately showing that a variety of bacteria lives upon the lychee peels. Considering these study findings, use of a lychee peel within a sourdough starter is expected to decrease the time it takes to develop to fermentation than in a mixture without any additional fruits. As long as the mature peel itself doesn’t contain any toxins that are transferable into the bread, the lychee peel has a unique opportunity to enable more efficient access to sourdough bread for undernourished Indian citizens.

In ensuring that the lychee peel is the fruit most capable Indian fruit of carrying potentially applicable yeasts on its surface, the addition of fresh Medjool dates to sourdough starters was also included. The smooth surface of the date is predicted to carry more bacteria and yeasts than that of the control group, but less than that of the lychee peel, therefore reaching fermentation in a time between that of the two major groups. India is the largest producer of dates internationally, so access to these fruits would also be easily available for Indian citizens.