There are many foods and drinks that rely on, and make use of microorganisms to break down complex carbohydrates into more digestible foods. Microorganisms can also act as a preservation agent. The basic principle is that these microorganisms make food resistant to other microbes by overgrowing desirable microorganisms that compete with limited food resources. In the process of fermentation the enzymes produced by the bacteria, mold or yeast change the characteristics of the food increasing the nutritional value of the fruit or cereal mash.
Microorganisms, what are they?
The word Microorganism is made up of "mikro" from the Greek to mean small and organism, an individual animal, plant, or single-celled life form. Thus, a microorganism is a life form not visible to the naked eye.
We are surrounded by millions of types of microorganisms. Microorganisms have adapted to all types of ecosystems and habitats; from the North Pole to the Antarctica. Millions of microorganisms live inside us symbiotically a sin our gut. Some of these microorganisms are benign and are responsible for the breakdown of matter into material that plants are able to use as nutrients. Some examples of these microorganisms are the center of this unit because of the beneficial uses they have in cooking. Others microorganisms are malign, and as such, we need to take the necessary precautions to insure that they do not sicken us or that we slow their effects so that we can consume those foods that they attack. An example of this is the bacteria that make foods and vegetables decay. Storing the produce properly so that the bacteria growth is inhibited can slow the process of decomposition.
There are five distinct types of microorganisms: 1) bacteria, 2) fungi, 3) viruses, 4) algae, and 5) protozoa. This unit manly studies two important members of the fungi family and names a few beneficial bacteria used around the household.
Single-cell organisms are present in all aspects of food preparation from its production, processing, storage, and even digestion. These microorganisms are responsible in some instances for the breaking of food sugars into alcohol molecules as in the case of beer, wine, and spirits, or in the conversion of lactose and other sugars to lactic acid, such as is in the case in yogurt making. In other instances, these microorganisms aid in the preservation of foods, such as is the case of pickled food, through the lactic acid fermentation process.
In simple terms we can refer to fermentation as the process of growing microorganisms in food. In this general definition we do not make a distinction between aerobic (using oxygen) or anaerobic (not using oxygen) chemical reactions that take place. However, these chemical reactions are important depending on the type of microorganism.
There are three different types of beneficial microorganisms that are explored as part of this unit: yeast, molds and some bacterium. These and other benign microorganisms make it possible for us to preserve foods, helps our system to break down, and prepare the nutrients trapped in the food, so that they can be easily digested. One example of the use of microorganisms is in the traditional method of soy sauce production. Here, the combination of roasted soy meal and crushed roasted wheat is fermented for three days with Aspergillus mold and then transferred into containers filled with a brine consisting of Lactobacilli and yeasts. It is in these vats that this mixture is allowed to ferment somewhere between six months to a year, prior to filtering and pasteurization. The final product is soy sauce and the byproduct cake is used as cattle feed.
Yeasts and molds
Both yeasts and molds (moulds) are fungi. One of the main characteristics of fungi is their lack of chlorophyll. Because of this, they grow by feeding on organic matter like mushrooms. Fungi can be unicellular or multi-cellular. This is what differentiates molds from yeasts. While molds are multi-cellular, and as such they grow in the form of filaments, also called hyphae (the vegetative threadlike part of the fungus), yeasts are fungi that grow as single cells.
Often when we think of fungi, the first thing that comes to mind is the harmful types responsible for food decay, causes human disease such as ring worm or athletes' feet, or causes plant disease such as mildew or rust. However, there are other fungi that are most helpful and that are used in the creation of certain drugs (i.e. Penicillin), or used in the breakdown of organic materials in recycling waste and dead organisms, or that are edible, such as mushrooms. It is however the fungi used in the making of cheese, wine, beer, and liquors, bread, and cereals that is of interest to us.
Few are the foods and drinks that have been given credit for influencing and given rise to civilization. Among these we must include bread and beer. Bread has been called the "staff of life" yet there is a continuous debate as to whether beer precedes bread as a source of nourishment. These foods and drinks would have not been possible without two of the most important yeast known to civilization: Saccharomyces cerevisiae for bread and Saccharomyces carlsbergensis for beer.
One fungus Aspergillus oryzae, also known by its most common name of koji, is widely used in Chinese and Japanese cuisine for the fermentation of soybeans in the creation of shoyu (soy sauce) and miso. This mold is also used in the creation of alcoholic beverages such as sake and huangiju. The process consists on converting a simple soluble fermentable sugar by hydrolyzing (decompose by reacting with water) sugar derivatives or complex carbohydrates present in rice, potatoes and other grains such as millet or wheat. Koji is also used in the making of rice vinegar.
The yeast of life: Saccharomyces cerevisiae
Yeast is a live single-cell organism that breaths and grows. As such, it requires an environment that facilitates its growth and subsistence. The optimum environment for Saccharomyces cerevisiae is from 12°ãC to 40°ãC (53.6°ãF to 104°ãF). This yeast tolerates temperatures from freezing to about 55°ãC (131°ãF) and even tolerates almost complete dehydration (this form, dry yeast, is the most common commercial variety).
Yeast is a natural growing organism that is present on fruits, flowers, and other objects that because of the sugar content allows the yeast to thrive. There are over 160 different types of yeast, most of which are of no real value to humans.
One of the most common and useful yeasts in history is Saccharomyces cerevisiae. This yeast is not only responsible for rising the dough in bread, but presently is even more importantly known for its use as a model system. This yeast has been identified as an ideal microorganism for biological studies due to the different biological functions shared with human cells. For example, its non-pathogenic nature, rapid growth and well-identified genetic system make it a useful organism. The cells of S. cerevisiae divide in a similar manner as our cells. Also, as a eukaryotic this yeast has a single nucleus containing chromosomes just like our won cells (Sherman, 198).
It is important to note here that both yeast and sourdough starters act as catalysts for the fermentation process to occur. The difference is that in using yeast, Saccharomyces cerevisiae is the only catalyst, while sourdough starters are composed of other yeasts and lactobacillus (a type of anaerobic bacteria responsible of turning lactose and other sugars to lactic acid).
Through the ages we see different cultures around the world creating many recipes to harvest and maintain yeasts' cultures alive. One way of maintaining these yeasts alive is through the creation of a starter. A starter is a medium of water, flour and yeast (or yogurt) that is kept alive by feeding it every so often and replacing it as time goes on. These starters mature with time. As the yeast cell dies it releases its contents into the medium and enhances the original flavor. Theses starters, although they contain some of the original yeast, are also populated with other bacteria, giving it a sour taste. Bread starters are also referred as "sponges", and in the most basic sense starters are yeast substitutes.
One of my favorite sources for making starters appeared in an article in the New York Times, on June 27, 1880 by someone under the initials L.H. This article lists at least six different ways of creating your own starter. They range from those made with grape leaves to starters made with potatoes. Who knew that there is such a variety of yeast "mediums"? I look forward to exploring some of these in my own cooking and with students. The following hop yeast recipe is but an example of the few worth exploring. In reading this recipe I deduce that the first time you create this starter, as it is the case with most starters, you make use of regular dry or other types of yeasts to expedite the process (even though you can do without it):
Three large potatoes, one handful of hops; put in a small bag; put the
potatoes and hops into two quarts of water and boil down to one quart;
take out the bag of hops and potatoes; mash the potatoes fine and throw
back into the boiling water; stir flour into this while hot until it is quite stiff;
let it stand until it is nearly cold, then add a half cupful of yeast, half a
cupful of sugar, one tablespoon of salt, and half a tablespoon of ginger;
set in a small place to rise; when light put in a covered jar and place
in a cool place. (June 27, 1880)
The more recipes for sourdough starters that you read, the more variations on one theme that you uncover. That is, in some recipes all they call for is water, flour, and time for the airborne microorganisms and those organisms in the flour to begin the fermentation process. However, in others, as the one mentioned above, we can observe the use of other ingredients that expedite or give a different flavor to the starter. The final end is the same.
The rationale for the sourdough starter is that it is created only with the natural ingredients included in the whole grain. As a matter of fact, under a less than favorable environment, adding sugar to the starter, other less beneficial bacteria might grow, making it useless. It is clear that the way to create and maintain a good sourdough starter is to encourage the growth of yeast and lactobacillus that are part of whole grains.
Something important to remember about sourdough starters is that you want to feed the starter twice a day discarding (or using for cooking) half of the amount and replacing it with more flour and water. The purpose of continuing to feed the starter is to encourage more growth and keep it alive. The starter will last longer if refrigerated. In this case you only need to feed it every couple of weeks. As stated earlier, although there are many microorganisms as part of the flour, you want to encourage only the growth of yeast and lactobacillus. At least one of the performance tasks of this unit will look at the differences between sourdough starters and yeasts.
In modern times there are other means of leavening grains that make use of substances such as baking soda and baking yeast. These products do not only expedite the cooking process, but additionally they are more consistent in the way they leaven the batters resulting in more consistent and reliable recipes.
Bacteria are another important unicellular microorganisms used in the preserving and processing of foods. A bacterium is a prokaryotic (does not have a nucleus), unlike yeast that has a nucleus (also called eukaryotic). We can find different types of bacteria that are important in the breakdown and processing of foods. Among the most important is the bacteria responsible for turning milk into yogurt (Lactobacillus bulgaricus, Lactococcus thermophilus, and/or Streptococcus thermophilus), kefir (different microbes, yeasts, and lactobacilli, Lactococci, and leuconostocs), and in cheese (Streptococcus and Lactobacillus).
In addition to the fermentation of milk, beneficial bacterial encompasses functions such as food digestion (by fermenting complex carbohydrates), acting as a barrier against pathogens and the making of vitamins (they synthesize folic acid, vitamin K, and biotin).
Among other less well known bacteria we have Aspergillus niger, which is responsible for the production (for commercial purposes) of large quantities of citric acid. In making sauerkraut, Leuconoctoc mesenteroides and Lactobacillus brevis are responsible for fermenting the sugars from raw cabbage and turning them into lactic acid, acetic acid, ethanol, and mannitol. Additionally, we have Lactobacillus plantarum and Lactobacillus mesenteroids as the bacteria responsible for starting the process of fermentation of green olives and making them edible.
As we can see from these examples, the use of bacteria extends farther than the bacteria found on the surfaces of the human body, which can be benign (i.e. Staphylococus epidermidis) or malign (i.e. Streptococcus pneumoniae). However, this bacterium is of no interest to us in that they are not a useful microorganism in the processing, preparation or cooking of food.
Chemistry: Why does it matter?
Matter occupies space and has mass. Thus it matters; it is in your face if big enough, or even when so small that cannot be seen with the human eye. It is the properties it has and the way that it behaves that matters in matter. And so matter matters in this unit for the simple reason that it is the focus of the study of chemistry and of this unit as we explore it through cooking.
Chemistry does not only offer a closer understanding of everything in the world that surrounds us and how it works. In doing so, it looks at the properties of matter in terms of atoms, the building blocks of matter. These properties of matter relate not only to its composition (the kind of atoms it contains) but also its structure (how these atoms are arranged).
Atoms are combined into molecules. A molecule is made up of at least two atoms bound by a chemical bond with a specific arrangement or shape. There are at least three ways of depicting molecules: through three-dimensional computer models, tangible plastic models, or line drawings. One important aspect of chemistry is visualizing molecular structures. For this reason, students in this unit will be able to depict molecules through line drawings and tangible plastic models to visualize chemical and physical changes. In a chemical change, the atoms are rearranged and there is no gain or loss in the number of atoms, however, the molecules present before the change are not the same after the reaction. In a physical change, all the molecules present at the end of the reaction are the same as those present at the beginning. The only difference is that the arrangement of those molecules relative to one another has changed.
There are about one hundred basic substances, called elements, which make up matter. In studying changes to matter, we look at the way that the properties of these elementary substances, or elements, affect their composition.
Among some of these basic elements, we have carbon, oxygen, hydrogen, or iron. Additionally, these elements are the building blocks that when combined can create an unlimited number of chemical compounds.