Fermented foods

1. 1
Microbiology of Fermented foods
Fermented foods are foods produced or preserved by the action of microorganisms. In
this context, fermentation typically refers to the fermentation of sugar to alcohol using
yeast, but other fermentation processes involve the use of bacteria such as lactobacillus,
including the making of foods such as yogurt and sauerkraut. The science of fermentation
is known as zymology.
Many pickled or soured foods are fermented as part of the pickling or souring process,
but many are simply processed with brine, vinegar, or another acid such as lemon juice.
Fermented milk products
Fermented milk products, also known as cultured dairy foods, cultured dairy products, or
cultured milk products, are dairy foods that have been fermented with lactic acid bacteria
such as Lactobacillus, Lactococcus, and Leuconostoc. The fermentation process
increases the shelf-life of the product, as well as adds to the taste and improves the
digestibility of milk. There is evidence that fermented milk products have been produced
since around 10,000 BC. A range of different Lactobacilli strains has been grown in
laboratories allowing for a wide range of cultured milk products with different tastes.
Product
Alternative
names
Fermentation agent Description
Acidophilus
milk
acidophilus
cultured milk
Lactobacillus acidophilus Thermophilic fermented milk,
Cheese
a variety of bacteria and/or
mold
Any number of solid fermented
milk products.
Crème creme fraiche
naturally occurring lactic acid
bacteria in cream
Originally from France; higher-fat
variant of sour cream.
Cultured
buttermilk
Lactococcus lactis
(Lactococcus lactis subsp.
Lactis)
Mesophilic fermented pasteurized
milk.
Cultured sour
cream
sour cream
Lactococcus lactis subsp.
lactis
Mesophilic fermented pasteurized
cream with an acidity of at least
0.5%.
Viili filbunke
Lactococcus lactis,
Geotrichum candidum
. Originally from Sweden but
today is a Finnish specialty.
Yogurt yoghurt,
Lactobacillus bulgaricus and
Streptococcus thermophilus
Thermophilic fermented milk,
• Streptococcus lactis has been renamed to Lactococcus lactis subsp. Lactis

2. 2
Examples
1. Yogurt or yoghurt is a dairy product produced by bacterial fermentation of milk. The
bacteria used to make yogurt are known as "yogurt cultures". Fermentation of lactose by
these bacteria produces lactic acid, which acts on milk protein to give yogurt its texture
and its characteristic tang.
Worldwide, cow's milk is most commonly used to make yogurt, but milk from water
buffalo, goats, ewes, mares, camels, and yaks is also used in various parts of the world.
Dairy yogurt is produced using a culture of Lactobacillus bulgaricus and Streptococcus
salivarius subsp. thermophilus bacteria. In addition, other lactobacilli and bifidobacteria
are also sometimes added during or after culturing yogurt.
The milk is first heated to about 80 °C (176 °F) to kill any undesirable bacteria and to
denature the milk proteins so that they set together rather than form curds. The milk is
then cooled to about 45 °C (112 °F). The bacteria culture is added, and the temperature is
maintained for 4 to 7 hours to allow fermentation.
2. Cheese is a generic term for a diverse group of milk-based food products. Cheese is
produced in wide-ranging flavors, textures, and forms.
Cheese consists of proteins and fat from milk, usually the milk of cows, buffalo, goats, or
sheep. It is produced by coagulation of the milk protein casein. Typically, the milk is
acidified and addition of the enzyme rennet causes coagulation. The solids are separated
and pressed into final form. Some cheeses have molds on the rind or throughout. Most
cheeses melt at cooking temperature.
Hundreds of types of cheese are produced. Their styles, textures and flavors depend on
the origin of the milk (including the animal's diet), whether they have been pasteurized,
the butterfat content, the bacteria and mold, the processing, and aging. Herbs, spices, or
wood smoke may be used as flavoring agents. The yellow to red color of many cheeses,
such as Red Leicester, is formed from adding annatto.
Cheese is valued for its portability, long life, and high content of fat, protein, calcium,
and phosphorus. Cheese is more compact and has a longer shelf life than milk, although
how long a cheese will keep may depend on the type of cheese; labels on packets of
cheese often claim that a cheese should be consumed within three to five days of opening.
When the cheese is allowed to ripen through the activity of various microorganisms,
various cheeses are produced. Soft cheeses, such as Camembert, do not spoil rapidly.
Camembert cheese is a product of the growth of the fungus Penicillium camemberti.

3. 3
Hard cheeses have less water and are ripened with bacteria or fungi. Swiss cheese is
ripened by various bacteria, including species of Propionibacterium, which produces gas
holes in the cheese. Bleu cheese is produced by Penicillium roqueforti, which produces
veins within the cheese as it grows.
Fermented beverages
• Beer (from barely) by yeast species e.g Saccharomyces cerevisiae
• Wine (from grapes) by yeast like Saccharomyces cerevisiae,
Pickles
Pickling, also known as brining or corning, is the process of preserving food by anaerobic
fermentation in brine (a solution of salt in water) to produce lactic acid, or marinating and
storing it in an acid solution, usually vinegar (acetic acid). The resulting food is called a
pickle. When both salt concentration and temperature are low, Leuconostoc
mesenteroides dominates, producing a mix of acids, alcohol, and aroma compounds. At
higher temperatures Lactobacillus plantarum dominates, which produces primarily lactic
acid.
Asian pickle
South Asian pickles (Achar) are made from certain individual varieties of vegetables and
fruits that are chopped into small pieces and cooked in edible oils like sesame oil or brine
with many different Indian and Pakistani spices.
Sauerkraut
Sauerkraut "sour cabbage", is finely shredded cabbage that has been fermented by
various lactic acid bacteria, including Leuconostoc, Lactobacillus, and Pediococcus. It
has a long shelf-life and a distinctive sour flavor, both of which result from the lactic acid
that forms when the bacteria ferment the sugars in the cabbage.
Bread
Bread is still another product of microbial action. Flour, water, salt, and yeast are used
to make the dough. The yeast most often used is Saccharomyces cerevisiae. This
organism ferments the carbohydrates in the dough and produces carbon dioxide, which
causes the dough to rise and creates the soft texture of bread. Unleavened bread is bread
that contains no yeast.
Fermented foods by type
Bean-based

4. 4
Soy sauce, soybean paste, Beijing mung bean milk,
Grain-based
Beer, bread, rice wine, malt whisky, grain whisky
Vegetable based
Mixed pickle, sauerkraut, Indian pickle
Fruit based
Wine, vinegar, brandy
Honey based
Mead, metheglin
Dairy based
Cheese, yogurt
Fish based
Bagoong, fish sauce, rakfisk, shrimp paste, 3
Meat based
Chorizo, Salami, pepperoni
Tea based
Kombucha
Organisms mostly involved in food fermentation
Prepared by
Amjad Khan Afridi
Date: 10th
May, 2017