Fungi In Manufacturing of Food
Although the use of fungi as a component in the food making process is more common now than in the recent past, these food products, with some notable exceptions, are still not a familiar sight to western cultures. The use of the term food-making process is used here to mean those food products that require the aide of fungi in their production. For example, the one with which you are most familiar is baked bread. The yeast is utilized in making the dough rise so that bread will come out light and fluffy. Without yeast, bread would be much denser and harder. Blue cheese would be another examples. Asian cultures, however, have a large varieties of such food, some of which have become well known in this country. This is possibly because larger number of Americans have become more adventurous in their dietary habits that has led to these types of food becoming more common place in our society. This is particularly true, in Hawaii, where there is a large Asian population. I have excluded mushrooms from such foods since they are the actual food product rather than being utilized to create another food product. We will cover some examples of such products and discuss the processes by which fungi are integrated into their production.
Leavened and Unleavened Bread
Although the growth of grains made civilization possible. Its use as bread did not come about immediately. People first had to learn about separating the bran and husks of the grain from the seed itself. For centuries, the entire grain was eaten, cooked or raw. The latter was difficult since the raw grain is as hard as a rock. Softening of the grain so that it could be chewed would take days of soaking in water or boiled to soften the grain more rapidly. Although this was not the most easily prepared, eaten, or even tasty food, there were health benefits to eating the raw grain. The husk of the grain is very nutritious, and contains bran. These unprocessed "whole grains" or those with the husk removed resulted in what is referred to as bulgur, in the Middle East, and groats in Europe. It was much later that people learned that whole grains could be cracked on a stone, which would remove at least some of the husk and with the reduction in surface area, the grains also required less cooking time. A tasty porridge could be made from this product when mixed with water, oil and sometimes honey, or the mixture could be placed on a hot stone to make the first flat bread or unleavened bread. However, the first hard bread must have been difficult to chew and even harder to digest for not all of the bran and husks could be removed from the grain in this fashion. Through refinement of milling technique, i.e. grind stone, mortar, etc., the grains were ground into flour. However, the resulting flour was still somewhat coarse and contained not only the bran and husk, but also stone chips. When flat bread was first made is not known, but the knowledge has been documented prior to 8000 B.C. since ancient, excavated dwellings from that time period have been found to have preserved flat bread (that's real hard bread!). It is thought that flate bread was consumed for thousands of years before the accidental discovery of leavened bread.
The Egyptians were believed to be the first to baked leavened bread, at around 3000 B.C. Wild yeast attracted to grain and flour mixture was responsible for making bread rise. With the development of more varieties of grains, baking leavened bread eventually became a skill, in Egypt, along with their ability to brew beer. It was probably much later that the Egyptians learned that they could take part of the risen dough from one baking to the next. This was a revolutionary concept since bread making would no longer rely on the chance landing of yeast on the dough. In addition, this gave a more consistent quality to bread. Relying on the chance landing of yeast on bread dough also invited unwanted bacteria and other fungi to infest the dough, often leading to bad taste in bread. Bread became a significant part of Egyptian life as evidenced by their use of bread for their money in trading for goods and their homage to Osiris, the god of grain. Even the workers who built the pyramids were paid with bread.
When leavened bread was first discovered and for thousands of years after, the reason as to why this type of bread was light and fluffy was not known. As in many other unexplained phenomena, a supernatural explanation was given for its existence. In the case of the ancient Egyptians, it was said that the god Osiris observed that the journey from Earth, to the land of the dead, was a difficult one and decided to lighten their burden, by giving mankind the ability to make leavened bread, so that their travel could be made with a lighter load. However, even today, some unleavened, commercial breads are made (Figure 1). One reason that it is still made is for its consumption during the Seder, the ceremonial dinner that is held during the first two days of the Passover, celebrating the Exodus of the Hebrews from Egypt. The story goes that in their haste to leave Egypt, the Hebrews took the raw dough for bread on their journey and baked it in the hot desert sun into a hard unleavened cracker called matzoh because they did not have the time to allow the bread to rise. The Passover refers to God "passing over" the houses of the Jews, as he was slaying the first borne of Egypt.
|Fig. 1: Unleavened bread (left) and leavened bread (right)|
The cultivation of grains and bread making eventually spread to Europe where many advances in bread making occurred. Rome, in 500 B.C., used a circular quern (Figure 2), a grain mill to make flour.
Fig. 2: The Quern is a hand mill used for grinding grain. It consist of two circular stones, one on on top of the other. Grain is admitted through the circular opening in the center of the top stone and turned with with a wooden handle being inserted into the slot on top.
By 150 B.C., Rome formed the first baker's guild and the at this time the wealthy Romans insisted upon having the more expensive white bread because the bran flakes in the flour bread made from ground grains was not a desirable product for the wealthy. Because bran gave bread a dark appearance and had a laxative property about it and gave people gas, only peasants ate bread made from grains. This trend is something that has persisted in Europe and English speaking countries to this day even though we now know that eating white bread has its nutritional draw backs.
The members of the first baker's guild, Collegium Pistorum, was unusual for its time. The bakers were the only Roman craftsmen who were freemen. All other traders were conducted by slaves. However, there were also disadvantages. The bakers and their children were not allowed to withdraw from the guild to take up another trade. They also were not allowed to mix with comedians and gladiators or to attend performances at amphitheatres so as not to be influenced by the vices of the ordinary people. This guild, now called the Guild of Master Bakers, has survived to this day with its headquarters in England and with its own coat of arms (Figure 3).
|Fig. 3: Coat of arms for Guild of Master Bakers.|
However, because of the preference for white and brown bread by 1307 A.D., The bakers of white and brown bread did part company for a time to form separate guilds, but by 1569, Queen Elizabeth I ordered the two back into a single guild.
The practice of taking a bit of risen dough, the leaven from a previous loaf of bread also continued for thousands of years, following its discovery in Egypt, and continued among the early settlers of North America. It became a custom to give daughters a bit of leaven, to take with her when she got married. In this matter, yeast in risen dough, have been passed on for many generations. Even today, there are still families that have retained this practice and have leaven that can be traced back in their families for over 200 years. Leavens that were passed on also differed in quality. Gold prospectors during the 19th. century, in the Pacific Northwest, made a practice of carrying among their possessions, a bit of "sourdough," the name they gave to their bread starter. The sour dough bread that resulted from this type of leaven has become one of the most popular of breads. In San Francisco, the sourdough center of the world, one of the famous bakeries claims to have a sourdough starter that is over 135 years old.
Some superstitions also became associate with bread. In ancient Palestine, it was customary not only to throw all leaven out of a home where someone had died, but all the leaven in neighboring houses, as well, because it was thought that the angel of death had thrust his sword into the leaven. Folklore concerning yeast have come about even in more recent time. In the United States, there is the story of how the Fleischmann brothers of Austria visited the United States in 1865 to attend their sister's wedding. However, they were less than thrilled about the flavor of the bread served to them. Two years later, when they emigrated to America, they decided to take a yeast sample with them because they were concerned about the lack of good yeast in America. The leaven of that yeast culture went on to become the basis of their yeast business, Fleischmann's Yeast, that still exist today.
While the use of leaven was important in ensuring that baked bread would rise, it was not very convenient. After the discovery that yeast was the leavening agent responsible for making bread rise, a practical means of obtaining yeast for the purpose of baking bread was developed that did not require saving the leaven from previous loaves. This was the yeast cake, which could be stored for long periods of time and had the added advantage of being able to buy specific strains of yeast for baking different types of bread. The production of yeast cake is a simple process, which involves the removal of water from yeast cells, which suspends their metabolism, making possible the long term storage of yeast. Today, the use of dried yeast is more commonly used in baking bread in homes.
In approximately 5000 years since leavened bread has been baked, bread has remained essentially the same. Grinding the grain into flour, mixing it with water and other ingredients, depending on what kind of bread you are making, forming the dough into loaves, allowing them to rise and then baking them in an oven. What has changed is that bread making has become fully automated. One automated feature, the bread slicing machine was invented in 1912, but was slow to catch on. It would not be until 1933 that 80% of commercial bread would be pre-sliced. Americans loved this new innovation and this was when the origin of the expression "the best thing since sliced bread" was coined.
Nutritional improvements also occurred during the 20th. Century. In late 1930s and early 1940s, bread was selected for a diet enrichment program in the United States. Diseases such as pellagra, beriberi, and anemia had become widespread. These diseases were associated with a lack of B-vitamins and iron. Since bread was a daily food item for most Americans, even those with poor diets, specific amounts of iron, thiamin, niacin, and riboflavin were added to white flour. This enrichment program was a major factor in the elimination of pellagra and beriberi in the United States, as well as in reducing anemia among Americans. In 1998, folic acid, a key nutrient in the prevention of serious birth defects, was added to all enriched grain foods, including bread.
Although the sight of mold in food is a sign that it is contaminated and should be discarded, there are some foods in which the presence of visible fungal mycelium is very much a part of the product. Among these are some of our cheeses. Two of the most familiar examples are Camembert and Roquefort, also known as blue cheese. These cheeses are among the favorites among gourmets. These cheeses are made from two species of Penicillium, P. camemberti, in Camembert cheese and P. roqueforti in Roquefort cheese.
Among one of the earliest of manufactured foods, the discovery of the cheese making process, itself, is believed to have occurred approximately 4000 years ago. As was the case with any food that requires the addition of microorganisms, the discovery was an accidental one. Because of the seeming magical transformation of milk into cheese, its origin, again, has been shrouded in myths and folklore. One story tells of an Arabian merchant carrying his milk with him in a pouch made from the stomach of a sheep. This is relevant since a sheep's stomach contains rennet, an enzyme that is required in the cheese making process. Rennet is the substance that makes milk curdle and separates it into whey (liquid) and curd (solid). By nightfall, this process had occurred and the merchant drank the whey and ate the curd. Upon his return home, the merchant told of his wonderful discovery and how satisfied he had been with his meal. In separating the liquid from the cheese, a product now existed that had much of the same qualities of milk, but now could be enjoyed as a food for a journey that would not spoil as quickly, and was also lighter than the original milk product.
It would be another 2000 years, according to some legends, before molds and other microorganisms were added to cheese for flavor. This development, again, was thought to have occurred accidentally. Afterall, why would you purposely place mold on cheese? The origin of Roquefort Cheese, according to Roquefort publicists, long ago, a young French shepherd boy took his sheep out to graze near the little village of Roquefort. During this time a sudden downpour occurred which forced the boy to take shelter in a cave. When the rain stopped, the boy had to go out and round up the sheep so that he could take them home. However, he had forgotten his lunch. It would be several weeks before he would return, to that particular cave, to find that his lunch was still sitting where he had left it. The bread was dried and had crumbled away and the cheese seemed to have veins of green growing throughout (Figures 4a-b). Although it did not look to be very good, the boy was very hungry and took a bite from the discolored cheese, and decided that it tasted better than any cheese he had previously had. So, the boy ran down to the village, shouting, "a miracle, a miracle," The people that gathered around the boy sampled the cheese, and from that day on they began bringing cheese to the caves around Roquefort so that it could be transformed into blue cheese. The same caves are still used for the manufacturing of Roquefort Cheese, today. This is the story that is so often told that even schoolchildren, by the time they reach the second grade, in Roquefort, know this story, verbatim.
|Fig. 4a: Roquefort cheese, with wrapping paper of cheese shown above.||Fig. 4b: Close up of cheese showing blue-green mycelium of P. roqueforti.|
Although no caves appear to be as well suited for the production of Roquefort cheese as the one in which it was discovered, Penicilium roqueforti is so ubiquitous that it was difficult to maintain a monopoly on this cheese, in Roquefort. However, this would not be due to lack of trying. The people of Roquefort feared that other cheeses of lesser quality manufactured under their name would destroy the reputation of their own Roquefort cheese. To prevent such an occurrence, the good people of Roquefort went to King Charles VI, who ruled that only the cheese of Roquefort could be called Roquefort. Although this would be repealed later, the use of Roquefort is still currently limited by French regulation to prevent cheese makers from misrepresenting the origin of their cheese. Today, cheese made with P. roqueforti, but not from the town of Roquefort, is usually generically referred to as blue cheese from the blue-green mycelium growing through the cheese.
Despite decrying the damaging of their reputation from competing producers of blue cheeses, it was impossible, even in the caves of Roquefort, to obtain a consistent quality of Roquefort Cheese since there were usually a variety of different fungi, as well as bacteria, that would be growing on the cheese that would give the finished product a slightly different taste each time the cheese was made. It would not be until the discovery that P. roqueforti was the key ingredient responsible for the manufacture of this cheese that inoculation of pure cultures could be used to produce a consistent quality in Roquefort Cheese.
In making Roquefort cheese, in Roquefort, P. roqueforti is added to the cheese made from sheep's milk. The cheese is salted and holes made throughout the cheese for aeration, and left for several days. The cheese is then allowed to age for two to five months. The variation in time is dependent on who is going to eat it. Americans like the cheese to be new and mild, while the French prefer it to be very old and strongly flavored.
"Roquefort" cheeses all contain the same molds, but are not made with the same kind of milk. In the United States and Canada, either goat's or cow's milk is used, while in Roquefort, sheep's milk is used, exclusively. This is why it is more costly. A sheep can only give one quart of milk a day, and only for six months of the year. Herds of 700,000 ewes provide the milk needed to produce Roquefort cheese, in Roquefort. The cheese, today, is still made in the twenty five caves in the nearby mountainside where the shepherd boy supposedly discovered the process so many years ago. Some of these caves go down the mountain approximately twelve stories. During the six months that the ewes are giving milk, the entire population of the town is involved in cheese manufacturing.
Blue cheese is also made in the United States, but it was not always possible for Americans to produce Roquefort cheese. France had kept the recipe, for Roquefort cheese secret, for centuries and did not cooperate when the United States expressed interest in producing this product. It was not until until 1918 that Roquefort cheese was produced in the United States. Mycologists had to first identify the fungus involved in the process and then through trial and error determine how much of an the fungus should be inoculated into a given amount of cheese. In addition, the optimum temperature, humidity and other environmental conditions required to produce quality Roquefort cheese had to be determined, as well.
Today, there are many blue cheeses other than Roquefort, and these do not originate in France, each one with its own distinctive quality. For example, in 879 A.D., the Italians, developed Gorgonzola, a pressed cheese made from cow's milk, and this cheese would make Italy the cheese-making center of Europe in the two centuries that followed. The English developed Stilton, a waxy cheese, with a wrinkled rind. the Greeks Kopanisti is known for its woody and peppery taste, and the Norwegians have Gammelost, which is a low fat cheese made from skim milk. Each one is unique because a slightly different recipe is used in their manufacture, but all require P. roqueforti.
Camembert cheese is quite different in appearance. The fungus involved in the manufacture of this cheese is Penicillium camemberti. The mycelial growth of this species occurs only on surface of the cheese and does not work its way inside to form veins as in P. roqueforti. Legend has it that the process for making this cheese was a relatively recent. It's creation has been credited to Marie Harel, in 1791, a native of the tiny village of Camembert, in Normandy. The story goes that she was given the recipe for this cheese by a priest. During the French Revolution, in 1789, all Roman Catholic priests in France were required to swear allegiance to the newborn republic. Those who refused were executed or forced into exile. Some hid in the countryside waiting for the day when they would be able to return to their homes. In October of 1790, the Abbé Charles-Jean Bonvoust took refuge in Marie Harel's farm. He was from the Brie, a region near Paris famous for its cheeses. In return for the shelter, Marie Harel was given the recipe for the making of Camembert cheese. The cheese was named by Napoleon as he passed through this small town. The people of Camembert thought the name unimaginative, but this was the name that gave fame to both the cheese and the town. This is a nice story, but one that is doubtful. Camembert apparently was well known for Camembert cheese long before the birth of Marie Harel. Thus, the origin of this cheese is unknown. Nevertheless, the bicentennial of Camembert cheese was celebrated in 1991.
As was the case with Roquefort cheese, there are several types of cheeses that are made with the aid of P. camemberti. Each one with a slightly different recipe and its own distinct taste. Brie, which is made in France, is a very similar cheese.
A cheese requiring a fungus and a bacterium is Limburger, a very strong cheese, in both flavor and odor. It is named for its place of origin, Limburg, Belgium and is not a very common cheese that is readily available. It is currently manufactured in Northern Europe and the United States. The cheese requires the action of two microorganism, a bacterium, Brevibacterium linens, which is responsible for the strong odor and a yeast. It is not a cheese that I or many other people have consumed because of its strong odor of rancid butter from the breakdown of milk fat by the bacterium. However, I have heard it said that the taste is not nearly as strong as the odor, which does not tell me a lot. Because of its strong aroma, my only knowledge of this cheese comes from a Three Stooges episode that I saw many years ago where Curly would "flip-out" each time he heard the tune Pop Goes the Weasel. The only way to calm him down was to give him cheese. At the end he was given Limburger Cheese and as he exhaled, the strong odor from the cheese made everybody in front of him pass out.
Since the accidental discovery of cheese, by Arabian merchants long ago, it has spread from the Middle-east to the West, especially through the United States, which is the biggest producer and consumer of cheese. Recently, the popularity of cheese has made its way to the East, and countries such as Korea and Japan now have ranked cheese as one of the favorite snack foods among teenagers.
One final note on cheese is the reference as to
how these cheeses are produced. The processes are usually referred to as "mold-ripened."
This, again, demonstrate how we can change the meaning of a process to sound more
favorable when fungi are carrying out a process which benefits us. Normally, when we see
fungi growing on our food, we say that it is "rotted." This latter
process is actually what is occurring in mold-ripened cheeses!
There are relative few foods, in Western cultures, that rely on the addition of microorganisms in their manufacturing. However, this is common place in Eastern cultures. Many of these foods predate recorded history. Until recently, such foods were virtually unknown in Western cultures. However, with the ever increasing population of the world, alternative sources of food have been sought. Many of these alternative food sources originate from Asian cultures. Although there is not currently any danger of a food shortage in this country, Western cultures have realized that their diets are not necessarily the most healthy. The earliest of these food products involved fermentation and today, fermented foods still play a prominent role in the diets of millions of people in the world. We will cover some of the more common examples, some of which you will be familiar.
There has now been a great deal of research that has been carried out on some of the fermented food products, so that the identify of the fungus involved in the process has been established. Some of the more familiar ones include miso, shoyu, tofu and tempeh. However, the microorganisms (this includes bacteria) involved in the majority of fermented food (there are approximately 500 of these) are unknown. Unlike Western cultures, in which fermented food is usually carried out by yeasts, Eastern cultures have utilized a number of different mycelial fungi.
Shoyu (soy sauce) is probably the most familiar Asian food product in this country, but probably few people know how it is made. All of you probably are aware that it is made from soybeans. The soybeans are cooked mixed with wheat flour, pressed into cakes, and placed in a special room where it is inoculated with Aspergillus oryzae (the same species used in making saki). The mixture is then incubated for three days. If all goes well the cakes will become covered with yellow mycelial growth. The molded cake is referred to as Koji, which is a fermentation product of grains. The koji is now mixed with salt and water and is now referred to as the Moromi. The moromi is then inoculated with a bacterium, Peiococcus soyae, which will ferment the mixture for approximately 6 months. The aged liquid which is pressed out is the soy sauce. Because it is a fermentation product, soy sauce does not spoil when left out.
Shoyu can also be made quickly without
the aide of microorganisms. This method is said to be "non-brewed". Soybeans are boiled with hydrochloric acid for 15 to 20 hours. After
most of the amino acid is removed, the mixture is cooled to stop the hydrolytic reaction. The amino acid liquid is then neutralized, pressed
through a filter, mixed with active carbon and purified through
Color and flavor are introduced to this hydrolyzed vegetable protein mixture by adding caramel color, corn syrup for sweetness, and salt. The mixture is then refined and packaged.
Shoyu was discovered
in China more than 2,500 years ago, and is thought to be one of the world’s
oldest condiments. Today, it has become increasingly known in the West as a flavoring
and flavor-enhancing ingredient.
The recipe for shoyu was thought to have been discovered over a long period of time. In preparation for winter, people of prehistoric Asia would preserve meat and fish by packing them in salt. The liquid by-products that leeched from the preserved meat were subsequently used as a base for savory broths and seasonings.
In the sixth century, when Buddhism became widely practiced in both Japan and China, vegetarianism became more widespread and created the need for meatless seasoning. One of the early meatless seasoning consisted of a salty paste of fermented grains, which was the first known product to resemble modern shoyu. While studying in China, a Japanese Zen priest came across this new seasoning. When he returned to Japan, the priest began making his own version of this seasoning and introduced it to others, which eventually evolved into the modern shoyu. Over the years, the Japanese modified the ingredients and brewing techniques of shoyu. One change was the addition of wheat in equal proportion to the soybeans. This produced a sauce with a more balanced flavor profile that enhanced food flavors without overpowering them.
Tempeh is one product that has gained some degree of popularity in the United States. It is a food product made from the fermented products of usually legume seeds with Rhizopus oligosporus, and is believed to have originated in Indonesia. Legumes are the main source of dietary protein in many developing countries, and in Indonesia, soybeans, peanuts and mung beans are the three important grains that are cultivated. The preparation of tempeh is the same regardless of the grain used. The principal steps in its preparation are the removal of the seed coat so that the fungus can reach the nutritional cotyledons underneath. The beans are then soaked in water, boiled or steamed until nearly cooked. The beans are then drained and cooled. The cooled beans are then ready for inoculation with R. oligosporus. The inoculation of the fungus into the boiled beans digests the complex carbohydrates and other organic compounds that may cause gas. Today, there is limited production of tempeh, in the United States, as well as changes in the recipe. It is not uncommon to find tempeh made with grains, such as rice, rather than legumes in the United States.
Miso is a Japanese word for fermented
soybean paste. Miso is not usually consumed by itself, but is dissolved in water as a base
for soup or used as a flavoring agent. Miso fermentation consists of washed, polished
rice, which is steamed and inoculated with Aspergillus oryzae. The inoculated rice
is incubated for 48 to 50 hours at 40 C or below, resulting in rice koji.
The carbohydrates and proteins of the inoculated rice are digested by the fungus
and converts it to sugars and amino acids. The rice koji is then inoculated by yeasts and bacteria and allowed to
ferment for about a week at 28 C and then raised to 35 C for about seven months.
Some Food Making Terms Involving Fungi
Aspergillus oryzae: Fungus involved in the making of soy sauce and miso.
Bulgur: In Middle East, said of whole or cracked grain, usually wheat. It is then cooked. Making it a more edible product that the whole grain, which was very hard and not digestible.
Flat bread: Bread which is unleavened and therefore harder and heavier.
Gorgonzola: An Italian variety of blue cheese made from cow's milk. As in all blue cheeses, it is made with the aide of Penicillium roqueforti.
Groats: European counter part of Middle East bulgur.
Koji: The resulting product that arises when cooked soybeans that has been pressed into cakes and inoculated with Aspergillus oryzae and allowed to grow for several days.
Leaven: Dough from bread that contains yeast that will make bread rise. The act of taking leaven from active dough and mixing it with fresh dough saved time and ensured that dough would rise when baking bread.
Leavened bread: Bread made from dough that contains yeast, which results in a light and fluffy bread.
Miso: In Japanese, literally fermented soybean paste. Used in making soup base, or flavoring agent. Requires the addition of Aspergillus oryzae.
Mold-ripened cheese: Cheese requiring the addition of a fungus in the making of the cheese.
Penicillium camemberti: Species of fungus used in the making of Camembert Cheese and other related cheese.
Penicillium roqueforti: Species of fungus used in the making of Roquefort Cheese, as well as other blue cheeses.
Rhizopus oligosporus: Species of fungus used in the making of tempe.
Roquefort Cheese: Cheese made in the town of Roquefort, France, requiring the fungus Penicillium roqueforti.
Soy sauce (=shoyu): Condiment, believed to be Chinese in origin, requiring the use of Aspergillus oryzae.
Stilton: British variety of blue cheese. As in all blue cheeses, it is made with the aide of Penicillium roqueforti.
Tempe: In the strict sense, legumes that have been cooked and inoculated with Rhizopus oligosporus. The breaking down of complex carbohydrates, in the legume, by the fungus, makes it a more digestible product. In tempe made in the West, grains have also been used.
Unleavened bread: Bread that is made from dough that does not contain yeast to make the dough rise. The product is a heavy and flat bread.
Yeast cake: A yeast product that is made from yeast, which has had its water removed, thereby suspending its metabolism and making it possible to store the yeast for long periods of time. This is how yeast is often sold, commercially.
Questions to Think About
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