Lactic acid bacteria are important to fermentation of human foods like yogurt, pickles and cheese. Their transformative powers might be magic in a time before microscopic knowledge. Here's more about the amazing activities of these industrious microbes in food and drink.
About Lactic Acid
Lactic acid is an organic acid produced during the fermentation process. It creates the tart flavor of fermented foods. Chemically, lactic acid is a byproduct of glucose metabolism when bacteria convert carbohydrates into energy under anaerobic (non-oxygen) conditions.
Lactic acid has important functions in food preservation. It lowers the pH, creating an environment to inhibit spoilage-causing microbes, while also providing distinctive flavors and textures. In some food and drink processes, bacteria like these work together with yeast.
Lactic acid bacteria (LAB) also create tangy yogurt and kimchi. Little Miss Muffet would not have her curds and whey without them.
Lactic acid bacteria belong to genera including Lactobacillus, Streptococcus, Lactococcus, Leuconostoc, and Pediococcus. Characterized by their ability to ferment sugars into lactic acid, the bacteria are ideal for fermentation and preservation.
Lactic acid bacteria are common in various habitats, including dairy products, fruits, vegetables and other plants. LAB occur in the human gastrointestinal (GI) tract, an extreme environment for microbes.
Lacticaseibacillus paracasei is genotypically and phenotypically related to other members of the Lacticaseibacillus casei group. This group also includes Lacticaseibacillus zeae and Lacticaseibacillus rhamnosus.
Lactic acid bacteria reproduce by binary fission, in which a single cell divides into two identical daughter cells. Under optimal conditions, such as warmth and the presence of sugars, LAB can double in number every 20 to 30 minutes.
These bacteria can live for days to weeks, depending on environmental conditions, their nutrient sources and competing organisms. In a well-controlled fermentation setting, lactic acid bacteria can thrive for a long time. Bacteria are potentially immortal.
The Nature of Lactic Acid Fermentation
In the process of pure lactic acid fermentation, lactic acid bacteria use glucose as a carbon source to produce the carbon acid pyruvate through glycolysis. Glycolysis involves the breakdown of one 6-carbon-molecule of glucose into two 3-carbon-molecules.
Pyruvate then uses the action of lactate dehydrogenase (LDH) to produce lactic acid. Lactate dehydrogenase is an enzyme found in nearly all living cells.
Lactic acid bacteria live naturally in raw ingredients such as milk and grain. They have co-evolved with mammals for thousands of years, forming symbiotic relationships to benefit both parties.
In nature, lactic acid bacteria help decompose organic matter. Their fermentation activity produces acids to enhance soil health, suppress pathogens, and support beneficial microbial communities. They're crucial in detoxifying plant pathogens and enhancing food preservation.
Lactic Acid Fermentation Process
The fermentation process of lactic acid bacteria begins when they're introduced to a carbohydrate source, like milk or vegetables. For dairy products, the bacteria convert lactose (milk sugar) into lactic acid, which lowers the pH.
This causes milk proteins or caseins to coagulate and form curds, the key to cheese production.
In yogurt, specific strains of Lactobacillus and Streptococcus are used, producing a creamy texture and tangy flavor.
For vegetables, such as in sauerkraut or kimchi, LAB ferment sugars naturally found in the vegetables. Each fermentation process varies depending on the type of bacteria used, time, temperature, and other factors, resulting in a delightful range of artisan flavors and textures.
In modern times, lactic acid bacteria still vital in food production. They're used not only in yogurt and cheese but also sourdough bread, pickles, sausages, and beverages like kefir. Lactic acid bacteria find application in probiotics.
As live microorganisms considered to have human health benefits they support intestinal wellness and improve digestion. They're also used in animal feed additives, and in the biotechnology industry for the production of biofuels and pharmaceuticals.
Improper fermentation processes can lead to food spoilage or pathogen growth. Proper hygiene, handling and storage of fermented foods are essential to prevent harmful bacteria. While lactic acid bacteria are generally beneficial, some can pose risks in food spoilage.
Cheese Production
Cheese ripening, cheese maturation or affinage, is a process in cheesemaking. It creates the distinct flavor of cheese, and through the modification of ripening agents, determines the features of different varieties of cheeses, such as taste, texture, and body.
The process is characterized by a series of complex physical, chemical and microbiological changes using bacteria and enzymes of the milk, lactic culture, rennet, lipases and added molds or yeasts. Most cheese is ripened, except for fresh cheese.
Facts About Lactic Acid Bacteria
Diversity: There are more than 200 different species of lactic acid bacteria
Probiotic Benefits: Many strains exhibit probiotic properties, helping maintain a healthy microbiome.
Acid Tolerance: LAB can survive acidic environments, making them well-suited for fermentation processes.
Flavor Enhancer: The acids and other metabolites they produce contribute to the unique flavors of fermented foods.
Lactic acid bacteria are gram-positive, meaning they have a thick cell wall that retains a violet stain in Gram's method of staining bacteria.
Some strains of lactic acid bacteria have antimicrobial properties to inhibit the growth of pathogenic bacteria.
These bacteria are known for their resilience in diverse environments, allowing them to thrive under varying conditions.
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