Which leavening agent is considered a microorganism

Hydrocolloids such as agar, alginate and carrageenan are isolated from wild and cultivated algae and used as additives in the food industry for their emulsifying and thickening properties. Some of the complex polysaccharides found in algae may be digested by bacteria in the gut since the needed enzymes for digestion are abundantly present in Japanese people but absent in people from North America.

Fermented dairy products have been prepared and consumed by people for centuries due to their high nutritional values. Fermented milk or dairy products have been part of human diet since ancient times.

Various fermented products are made by different strains. Lactic acid fermentation is performed most often by lactic acid bacteria. Due to their abundance in nature, including mucosal surfaces of the human body, and their use in fermented foods they are labeled as GRAS generally recognized as safe.

The main genera that belong to the lactic acid bacteria group are: Lactobacillus , Leuconostoc , Lactococcus , Pediococcus and Streptococcus. These bacteria ferment the carbohydrates in milk, the major one being lactose, to lactic acid and some other products. The acid precipitates the proteins in the milk and that is why fermented products are usually of thicker consistency than milk. The high acidity and low pH hinders the growth of other bacteria, including pathogens.

Some lactic acid bacteria can produce agents with antimicrobial properties. Since milk is rich in many nutrients such as protein, calcium, phosphorus, and B vitamins dairy products are an excellent food. Records of yogurt preparation as food date back to centuries BCE. Classic yogurt is the result of the fermentation of two main bacterial species: Lactobacillus bulgaricus and Streptococcus thermophilus.

Sometimes other lactic acid bacteria are added as well. In many countries, the traditional food is yogurt without any sweeteners which could be consumed plain or used to prepare a variety of dishes usually with vegetables.

Yogurt has been traditionally consumed in Eastern cultures as a cold drink after mixing with water e. After the industrialization of yogurt production in the twentieth century, yogurt with added sweetener and fruit or fruit jam has become popular in the Western world. Turkish cacik : A yogurt dish made of plain yogurt and cucumbers. Cheese is another popular and ancient dairy product.

It consists of milk proteins and fat together with lactic acid bacteria. It has longer shelf life than uncultured milk. Currently there are a few hundred varieties of cheese produced all over the world. Making cheese is similar to yogurt but after acidification usually with lactic acid bacteria Lactococci, Lactobacilli, Streptococci , the solids are separated from the whey by coagulation with rennet and processed further to yield the final product. Depending on the type of cheese, the solids could go straight to packaging or other bacteria or mold could be added e.

Lactic acid bacteria have been researched for medicinal health benefits. In the early twentieth century, the Nobel laureate in medicine, Elie Metchnikoff, believed that the longevity of peasants in Bulgaria and the Russian steppes was due to their high consumption of milk-fermented products.

He hypothesized that the lactic acid bacteria would inhabit the gut after consumption, create and acidic environment as they grow and multiply, and hence prevent the growth of proteolytic. After it was discovered that Lactobacillus bulgaricus can not live in the human gut, the idea was abandoned.

Years later, strains of Lactobacillus acidophilus were found to thrive in the gut after implantation and the research started again. Most of the researched species were isolated from different fermented dairy products. The research has been focused on curing or preventing a number of diseases like diarrhea, intestinal inflammations, urogenital infections, allergies, etc. Some species have been prepared and sold as nutritious supplements.

However, so far there has not been enough evidence to establish a definite cause and effect relationship about any of the marketed products. Privacy Policy. Skip to main content. Industrial Microbiology. Search for:. The Microbiology of Food.

Wine, Beer, and Alcohol The production of alcohol beverages is a process that involves the active participation of microorganisms, most often yeasts. Learning Objectives Explain why microorganisms are used for beer, wine, and sake production. Key Takeaways Key Points Yeasts are the main fermentor and alcohol producer in the production of wine, beer and other alcohol drinks.

The main yeast species used is Saccharomyces cerevisiae. It ferments the sugars, coming from different sources, e. Both wild and cultivated strains are used. The species or strains used in the fermentation play an important role in giving the final taste properties of the drink. Key Terms must : The unfermented grape juice of crushed grapes that contains fruit, seeds and skins. Vinegar Vinegar is a food product made by acetic acid bacteria that can ferment the alcohol in alcoholic liquids to acetic acid.

Learning Objectives Describe how vinegar is made and the common uses of vinegar. Key Takeaways Key Points The fermentation of alcohol requires oxygen and its availability can determine the rate of vinegar production. The main genus used for vinegar fermentation is Acetobacter sp. Some of the most common uses of vinegar are in food preparation, as a cleaning agent, and as a medicine.

Key Terms starter culture : Starter culture consists of live microorganisms with some medium used to start fermentation or growth in a fresh new medium substrate. Citric Acid and Other Organic Compounds Many organic compounds, like citric acid, are produced industrially by microorganisms. Learning Objectives Explain how citric acid and other organic compounds are produced by the mold Aspergillus niger. It has the ability to produce citric acid in high quantities and exports it outside the cells.

Citric acid is used in the food, chemical and pharmaceutical industries. Key Terms molasses : Molasses is viscous syrup produced from a variety of sources, such as sugar beets, sugarcane and grapes.

Edible Fungi Fungi are used as food or as producers of a variety of food products bread, wine, beer, etc. Learning Objectives Describe how yeast, molds and mushrooms are used in the food industry. Key Takeaways Key Points The single cell yeast species, Saccharomyces cerevisiae, has been used as the major leavening agent in making bread for thousands of years. Key Terms leavening agent : An organism or compound that can make dough rise and produce soft bread.

Mushrooms Edible mushrooms are macrofungi since they are visible with a naked eye. A small piece of this leavened dough was saved and used as a starter source of the same yeast for the next batch, much in the same way sourdough bread is made today. Principle-Agent Problem The principle- agent problem agency dilemma exists when conflicts of interest arise between a principal and an agent in a business setting.

In economics, the principal- agent problem also known as an agency dilemma exists when conflicts of interest arise between a principal and an agent in a business setting. This connection sets the standard for judging the performance of the agent. The diagram shows the basic idea of the principle agent problem. P is the principle and A is the agent. Fermented Foods Fermentation is also employed in the leavening of bread CO2 produced by yeast activity ; in preservation techniques to produce lactic acid in sour foods such as sauerkraut, dry sausages, kimchi, and yogurt; and in the pickling of foods with vinegar acetic acid.

Biological Control of Microbes Those that result in bacterial death are called bactericidal agents. The magic of working with mother dough is to create and maintain a constant balance among the different microbic species.

The ability of working with sourdough lies in the capacity of maintaining this balance over time. If the microflora is too heterogeneous and unstable, yeasts and lactic bacteria will start a battle for gaining the fermentative substrate, which is rich in nitrogen and vitamins. The microflora is balanced and can last over time, if temperature and humidity conditions are favorable and adequately maintained.

External conditions determine not only the ratio between different species, but also the quality and quantity of the organic acids produced, which are able to modify the rheology of the knead. By external conditions, I mean temperature, water availability, oxygen and free space: in other words, the method for preserving sourdough. Keeping sourdough in a bag, in a water bath, free or in cream, affects the ratio between yeasts and lactic bacteria, as well as the way the biga will react in the knead.