…are women under represented in the history of yeast research because they don’t drink enough beer?

[The Leaven – exploring the relationship between science and religion (cont)]

Now, in the 21st cent, there are about 30 yeast factories in the European Union consuming about a million tons of cane molasses per annum. European yeast production alone generates an annual turnover of 800 million Euros. Until the turn of the 19th century yeast was supplied in a liquid form very similar to that found at the bottom of beer barrels. Perhaps, in a similar way to  how bread was made in early Egyptian civilisation from fermenting beer. Pliny the Elder noted in the first century BC that Gallic and Iberian bread was particularly light because it had been made with froth from the top of beer.

There are now several forms of yeast, compressed, crumbled and active/instant dried and genetically modified. The task of baking and brewing in earlier civilisations would have been difficult without the knowledge of sterilisation and pasteurisation. In ancient times, leaven or sourdough would have been left to rise in considerably unsterile conditions in a warm temperature. This environment would have been optimal not only for yeast but for all kinds of microbial growth including those that were pathogenic to humans. It is not surprising that leaven was associated with impurity and corruption. Excessive contamination would have certainly contributed to disease.

The desired characteristics of the yeast strain used in brewing and baking are different although they use the same species Saccharomyces cervisiae, which is also known as bakers or brewers yeast. Brewing yeast needs to have an agreeable flavour and an ability to flocculate so that the wort can settle quickly to achieve clear beer. In order to achieve these characteristics yeast are selected through generations, so that a specific yeast strain produces a desired flavour. In Darwinian terms this would be known  as directional selection.  So the variety of yeast varies with a particular industrial use. For instance, pizza dough is made with reduced power dry active yeast. Its slow fermentation allows the pizza to be shaped with reduced shrinkage after baking. Most commonly yeast for the baking industry is supplied as a compressed block because this form has a longer shelf life. Just 2.5 grams of this yeast in 100g of flour divides until it reaches a population size of 25 billion yeast cells.

Package of compressed yeast. Image by Hellahulla.

There is no question that yeast has transformed the structure of modern culture. In the food industry it provides baked goods, yeast extracts and alcoholic beverages. In scientific research it is a major model organism used mainly in molecular biology to discover information about the mechanisms of cellular processes. In fact, early in the 20th century, RNA was called yeast nucleic acid because it was first discovered in yeast.

Disappointingly, no women have been attributed to any of the early scientific discoveries associated with yeast. OK, they were less likely to encounter  Leeuwenhoek’s animalcule-containing sperm or beer during their daily routines but the reasons seem more likely to be associated with the status of women within religion.  As a consequence, they are largely excluded from early investigations were scientific endeavour was mainly to reveal the complexity of God’s creation. These investigations seem to be exclusively undertaken by men. Within the Bible it is clear that women were preferred to have a more subordinate role as revealed in a letter from Paul the Apostle to Timothy [Tim (1) 2, 11-15]:

Women should learn in silence and all humility. I do not allow them to teach or have authority over men; they must keep quiet. For Adam was created first, and then Eve. And it was not Adam who was deceived; it was the women who was deceived and broke God’s law.

In subsequent chapters, I will be addressing the portrayal of women in the progress of religion and science.

…yeast symbolically represents both purity and corruption

[The Leaven – exploring the relationship between science and religion (cont)]

The term leaven originates from the latin word levere, the French equivalent being the noun levure meaning to rise. The English term yeast, probably originates from the Greek term for fermenting which was zestos. Derivatives from later European influences resulted in the medieval English terms zeest, which eventually became yest.

Fermentation procedures and the art of making leavened bread was first introduced by the Egyptians over 4000 years ago. In ancient Egypt, brewing and baking were practiced together on the same premises. Wooden and plaster models depicting Egyptians working in a brewery and bakery have been recovered from a tomb dated around 1975 BC during the reign of Amenemhat I. Egyptian hieroglyphs that show pictures of dough rising next to bread ovens have also been found. The Egyptians were therefore aware that both processes used the same substance.

A funerary model of a bakery and brewery, dating the 11th dynasty, circa 2009-1998 B.C. Painted and gessoed wood, originally from Thebes. Image by Keith Schengili-Roberts

To the Egyptians, bread was an important commodity used as a type of currency for trading and for the payment of services. In fact, the workers who built the pyramids were believed to have been paid in bread. Bread was also used to pay homage to Osiris the God of grain. The Egyptians believed that Osiris had given them the gift of leavened bread to make it lighter to carry, especially in the journey to the afterlife.

In contrast to the Egyptians who revered fermented dough, the ancient Palestinians were extremely suspicious of it. Perhaps this could be due to the different methods by which the bread was leavened. Palestinians would reserve a piece of leavened dough from a previous baking to make the next batch of bread. This dough could easily have been contaminated by harmful microbes which may not have been completely destroyed by the baking processes. If a person died all leaven was thrown out of the house and from all neighbouring houses because Palestinians thought that it may have contributed in some way to the individual’s demise, they believed that the angel of death may have thrust his sword into it.

In Britain during the 15th century, as in ancient Egypt, brewing also took place on the premises where bread was baked. The thick layer of dormant yeast cells that sank to the bottom of the brewing or wine vessel was usually referred to as the lees, while froth from the top of beer was known as barm. Barm from a good batch of beer would be reused to make more beer and to ferment bread dough. Barm, the brewer’s equivalent of leaven, used to be referred to as Godisgoode because it was thought to be a gift from God. Yeast used in brewing and baking seemed to be received in a different manner to leaven that was used to make sourdough. In fact during the 17th century the Paris Faculty of Medicine tried to ban leaven because in the New Testament St. Paul had signified that it was a substance that denotes corruption.

So it seems that fermentation generated through leaven was not viewed in the same way or as a similar process to the fermentation that produced wine. It is clear from passages in the Bible that leaven is used figuratively to symbolise the permeating influence of certain types of human behaviour, especially corruption. Traditionally unleavened bread is used to symbolise the purity of Christ’s body whereas wine symbolises the blood of Christ. This is not without some irony, as wine is made in a similar process and perhaps more likely to lead to acts of sin and corruption when consumed than is bread. Indeed, some religions do recognise this and at the beginning of the 20th Century, alcohol became prohibited for a time in a number of Nordic countries and North America due to Protestant led objections. Alcohol is also prohibited in some countries that follow Islamic laws. The contradictory views relating to fermentation in wine and bread will be discussed at greater length in a later chapter.