Kefir, The champagne of Dairy Products

Kefir is fermented milk obtained through the action of certain bacteria and yeast. Because they remain alive these microorganisms continue to produce carbon dioxide in the final product, which explains the characteristic containers used to package kefir. Carbon dioxide also accounts for the tingling sensation reminiscent of champagne experienced when eating kefir.

How Is Kefir Made?

First, grains of kefir are added to partially skimmed cow's milk. Over the next twenty-four hours, bacteria and yeast present in the kefir grains cause the milk to ferment, making it more acid (lowering its pH) and changing its texture and composition. Carbon dioxide is also produced. Following incubation and maturation, the grains are separated from the culture medium, which is added to a fermenting chamber containing pasteurized milk. The inoculated pasteurized milk is left to incubate and mature, and is transformed into kefir, which is sold plain or with fruit added to it. Kefir continues to produce carbon dioxide until it is consumed, and its packaging takes this into account. Kefir containers are Read More

Kefir, The champagne of Dairy Products

Kefir is fermented milk obtained through the action of certain bacteria and yeast. Because they remain alive these microorganisms continue to produce carbon dioxide in the final product, which explains the characteristic containers used to package kefir. Carbon dioxide also accounts for the tingling sensation reminiscent of champagne experienced when eating kefir.

How Is Kefir Made?

First, grains of kefir are added to partially skimmed cow's milk. Over the next twenty-four hours, bacteria and yeast present in the kefir grains cause the milk to ferment, making it more acid (lowering its pH) and changing its texture and composition. Carbon dioxide is also produced. Following incubation and maturation, the grains are separated from the culture medium, which is added to a fermenting chamber containing pasteurized milk. The inoculated pasteurized milk is left to incubate and mature, and is transformed into kefir, which is sold plain or with fruit added to it. Kefir continues to produce carbon dioxide until it is consumed, and its packaging takes this into account. Kefir containers are sealed with a sheet of aluminum that stretches as carbon dioxide is produced, and have large lids designed to accommodate this expansion.


© Armand-Frappier Museum, 2008. All rights reserved.

The yeast transform the lactose into carbon dioxide, and, to a lesser extent, ethyl alcohol.



Commensalism and symbiosis can be observed in kefir. Here, the diplococci feed on the waste products of yeast. Some bacteria may even die if the yeast are removed!

Photo: Miloslav Kalab, Agriculture and Agri-Food Canada, Ottawa

© Miloslav Kalab, Agriculture and Agri-Food Canada, Ottawa


The famous kefir grains

Photo: Ross McKay

© Ross McKay


Kefir grains are off-white or pale yellow, have an irregular shape similar to cauliflower buds, and a texture similar to tapioca pudding. A single grain may be up to 2 cm in diameter and weigh approximately 800 mg (1200 mg once immersed in milk). Each grain is composed of a matrix of kefiran (a type of sugar) and proteins which traps the live bacteria and yeasts that will eventually multiply.

The microbial composition of kefir grains depends on their country of origin. More than twenty bacterial species—including Lactobacillus kefirgranum, Lactobacillus kefir, Lactobacillus kefiranofaciens, Lactococcus lactis and species from the Leuconostoc. Several species of yeast—including Candida kefir, Kluyveromyces marxianus and Saccharomyces cerevisiae are also present.

Kefir grains are off-white or pale yellow, have an irregular shape similar to cauliflower buds, and a texture similar to tapioca pudding. A single grain may be up to 2 cm in diameter and weigh approximately 800 mg (1200 mg once immersed in milk). Each grain is composed of a matrix of kefiran (a type of sugar) and proteins which traps the live bacteria and yeasts that will eventually multiply.

The microbial composition of kefir grains depends on their country of origin. More than twenty bacterial species—including Lactobacillus kefirgranum, Lactobacillus kefir, Lactobacillus kefiranofaciens, Lactococcus lactis and species from the Leuconostoc. Several species of yeast—including Candida kefir, Kluyveromyces marxianus and Saccharomyces cerevisiae are also present.


© Armand-Frappier Museum, 2008. All rights reserved.

Kefir making

Kefir is the champagne of dairy products! Here you can see kefir grains, which are little balls of sugar and proteins containing bacteria and yeasts that will convert milk into a creamy, sparkling substance: kefir! The yeasts and bacteria are left to reproduce for an incubation period of 24 hours and the kefir grains are then removed from the mixture. The yeasts and bacteria produce carbon dioxide gas and this is what produces the little bubbles in the kefir. Kefir is specially packaged to account for this production of carbon dioxide gas.

Kefir: a product to discover!

Production Cinémanima inc. and Armand-Frappier Museum

© Production Cinémanima inc. and Armand-Frappier Museum


How Microorganisms Help Make Cheese

Cheese-making usually comprises three stages: coagulation or curdling, draining, and ripening. Microorganisms are an indispensable part of cheese-making: lactic bacteria are often used in curdling, and ripening usually requires the use of bacteria, molds, and sometimes even yeast.

Cheese-Making, Step By Step

1) Curdling (or coagulation)
The first step in making any cheese is curdling, the process of destablizing the network of milk proteins known as caseins. The disruption of the casein network results in the production of a curd that eventually becomes the cheese, and of a watery whey which is discarded. Curdling is achieved by adding a coagulating enzyme to the milk, acidifying the milk, or both. The properties of the cheese are determined in large part by the amount and activity of added enzymes and by the extent to which the milk is acidified.

2) Draining
The details of the draining process are determined by the type of curd involved. Acid curds are drained by simply separating the curds from the whey, sometimes with the h Read More

How Microorganisms Help Make Cheese

Cheese-making usually comprises three stages: coagulation or curdling, draining, and ripening. Microorganisms are an indispensable part of cheese-making: lactic bacteria are often used in curdling, and ripening usually requires the use of bacteria, molds, and sometimes even yeast.

Cheese-Making, Step By Step

1) Curdling (or coagulation)
The first step in making any cheese is curdling, the process of destablizing the network of milk proteins known as caseins. The disruption of the casein network results in the production of a curd that eventually becomes the cheese, and of a watery whey which is discarded. Curdling is achieved by adding a coagulating enzyme to the milk, acidifying the milk, or both. The properties of the cheese are determined in large part by the amount and activity of added enzymes and by the extent to which the milk is acidified.

2) Draining
The details of the draining process are determined by the type of curd involved. Acid curds are drained by simply separating the curds from the whey, sometimes with the help of stirring, heating, or centrifugation. Rennet curds, such as Oka cheese, automatically expulse the whey from the curd as the enzyme causes the milk's casein network to contract. This type of curd readily lends itself to mechanical processing such as cutting, stirring and pressing. The draining operation for mixed curds depends on the amount of coagulating agents used and the time at which they were added.

3) Ripening
Ripening gives the curd a specific appearance, texture, aroma and flavour. The microorganisms used in ripening vary from cheese to cheese. Fresh-milk cheeses such as cheddar and mozzarella are not ripened.

Surface-ripened cheeses become coated with molds, yeasts, or even bacteria. Oka cheese, for example, is covered by red bacteria known as Brevibacterium linens. These bacteria degrade certain amino acids in cheese and give Oka its characteristic aroma.

The molds Penicillium camemberti and Penicillium roqueforti contribute to the ripening of downy-rinded cheeses such as Camembert and the blue cheeses. These molds cause physical changes in the cheese and modify its flavour and aroma. It should be noted that the microbial population continues to multiply throughout the entire ripening stage. Factors such as temperature, atmospheric composition and the humidity of the ripening chamber, which greatly influence the microbiological and enzymatic activity in progress, are therefore strictly controlled.

The holes found in some cheeses are formed during ripening. The characteristic holes and flavour of Emmental and Gruyère cheeses are the result of the carbon dioxide and propionic acid produced by propionic bacteria.


© Armand-Frappier Museum, 2008. All rights reserved.

Various types of cheeses.

Photo : Nicole Catellier

© Nicole Catellier, Cinémanima inc.


The mold Penicillium roqueforti is used in the manufacture of Roquefort cheese.

Dennis Kunkel Microscopy, Inc.

© Dennis Kunkel Microscopy, Inc.


Cheese making

After the milk, the most important ingredients in cheese making are the microorganisms! Generally, cow’s or goat’s milk is used. Cheese is made in three steps: curdling, draining, and ripening.

All cheeses are made by curdling the milk. Caseins, the proteins found in milk, are destabilized by lactic acid bacteria or by rennet, an enzyme. This process produces the solid part, known as the curd, and the liquid part, that will be subsequently discarded, called the whey.

  • Hard cheeses such as Parmesan or Oka result when the curd is obtained using rennet.
  • The curd of cream cheeses such as cottage cheese is obtained by the action of lactic acid bacteria.
  • For some cheeses, the curd is made by a mixture of the two techniques.

Draining is the production step during which the coagulum or curd is recovered and the whey is discarded.

Ripening is the last step. This is the step that gives the curd its appearance, its aroma, and its specific taste.

The surface of a cheese is often made up of moulds; Oka cheese, for example, is covered with a red mould called Brevibactérium linens.

Some cheeses have holes formed during the ripening stage by propionic bacteria. These bacteria produce carbon dioxide gas and this is what makes the holes found in Gruyere or Emmenthal cheeses.

In the past, the cheese maker needed to add ferments to his cheese during the ripening stage. Nowadays, ferments are 500 times more concentrated than in the past, allowing a more uniform production.

That is why today, your favorite cheese will always have that same good taste every time you buy it!

Production Cinémanima inc. and Armand-Frappier Museum

© Production Cinémanima inc. and Armand-Frappier Museum


Winemaking : a job for yeast

Without yeast, there is no wine, there is only grape must. Yeast plays a role of paramount importance in the winemaking process. It converts the sugar in the must, obtained by pressing the grapes, into alcohol. The yeast also produces minor constituents, which modify the aroma and the flavour of the wine.

The multiple stages of winemaking

Grape harvesting
Grape harvesting generally starts in September and lasts for a period of about three weeks. Grapes are harvested by hand, bunch by bunch. The white wine, Orpailleur, is the product of a type of vine known as Seyval Blanc.

Pressing
The harvested grapes are pressed. The must is stored in a vat in the fermenting room. The grape pomace and the skins of the grapes are recovered and recycled as compost for the grower’s vines.

Clarification
For two days, the must is kept at a temperature below 10°C while adding proteolytic enzymes (they lyse proteins) and sulfur dioxide (SO2). The enzymes degrade the large protein particles and the SO2 contributes to the preservation of the mixt Read More

Winemaking : a job for yeast

Without yeast, there is no wine, there is only grape must. Yeast plays a role of paramount importance in the winemaking process. It converts the sugar in the must, obtained by pressing the grapes, into alcohol. The yeast also produces minor constituents, which modify the aroma and the flavour of the wine.

The multiple stages of winemaking

Grape harvesting
Grape harvesting generally starts in September and lasts for a period of about three weeks. Grapes are harvested by hand, bunch by bunch. The white wine, Orpailleur, is the product of a type of vine known as Seyval Blanc.

Pressing
The harvested grapes are pressed. The must is stored in a vat in the fermenting room. The grape pomace and the skins of the grapes are recovered and recycled as compost for the grower’s vines.

Clarification
For two days, the must is kept at a temperature below 10°C while adding proteolytic enzymes (they lyse proteins) and sulfur dioxide (SO2). The enzymes degrade the large protein particles and the SO2 contributes to the preservation of the mixture due to its anti-oxidant and anti-bacterial properties. The must deposits that result from this process are eliminated by racking, a clarification process.

Storage in tanks
The clarified must, which resembles juice more than wine, macerates at low temperature for two or three days.

Fermentation
Dry active yeasts are the ones mainly used for inoculating the must. They are obtained by freeze-drying a concentrated yeast culture. Sold as a powder, these yeasts must be reconstituted with water and sugar by the cellar master. Each gram of this powder contains approximately thirty billion yeast cells. The Lallemand Company in Montreal is one of only six plants in the world that produce these yeasts.

The cellar master adds the reconstituted yeasts to 10% of the contents of the fermentation vat, or leaven, and then incorporates this mixture into the total contents of the vat. This reduces the latency time before the fermentation process begins. The yeast, Saccharomyces cerevisiae, in the case of Orpailleur white wine, then goes to work converting the sugar into alcohol, a process that lasts about twelve days. During this time, the cellar master carefully controls the temperature (between 14°C and 17°C), which must be suitable for the yeast and yet not alter the distinctive quality of the wine, which comes from the type of grape used in its fabrication. Yeast activity must also be carefully monitored as it can be linear or have peaks. The cellar master must therefore be vigilant in order for everything to unfold as it should, leading to the desired results.

Chaptalization
It is sometimes necessary to add sugar to the must to obtain a complete fermentation or to prolong it until the desired alcohol level is attained (17 g of sugar gives 1% of alcohol).

Deacidification
Some years, because of climatic conditions, the fruit does not reach perfect maturity and the acidity of the must is too high. The acidity can be corrected to approximately 4.5 grams of H2SO4 per liter using calcium carbonate.

Fining
Bentonite (clay) is added to clarify the wine, facilitate filtration, and ensure stability. It acts by precipitating and dragging along with it most of the suspended particles and proteins.

Racking
The deposit found at the bottom of the vat is called “lees ” This can be eliminated by racking, a process which consists of recovering only the clear portion of the wine.

Refrigeration or cold-stabilization
Wine contains tartaric acid, which can eventually crystallize. To avoid this happening in the bottle, the wine is refrigerated (0 °C) for a few days before bottling. This triggers a crystallization also known as tartaric stabilization.

Blending
Depending on the desired end products, and after tasting, some vats are blended while others are not.

Oak barrel maturation
Some wines are left to mature for several months in oak barrels. The wood fibre adds vanilla and wood flavours to the wine.

Bottling
Before bottling, the wine is filtered to eliminate bacteria and yeasts.

Ageing
Some wines are aged for several years in wine cellars before reaching the desired maturity for consumption.

Tasting
Enjoy!


© Armand-Frappier Museum, 2008. All rights reserved.

Vines at the L’Orpailleur winery

Photo : Nicole Catellier

© Nicole Catellier, Cinémanima inc.


Wine preparation

Photo : Nicole Catellier

© Nicole Catellier, Cinémanima inc.


Wine preparation

Photo : Nicole Catellier

© Nicole Catellier, Cinémanima inc.


Barrel of wine at the L’Orpailleur winery

Photo : Nicole Catellier

© Nicole Catellier, Cinémanima inc.


Winemaking

Winemaking begins with growing grapes. It starts with sowing vines and maintaining them until they bear fruit. Grapes can be red or white and several varieties are available.

When the grapes are ripe and very sweet, generally around the month of September, they are handpicked, bunch by bunch, or with adapted machinery. The harvesting period lasts about 3 weeks. The grapes are then pressed to extract the liquid also called grape must.

Without microorganisms, the must will never become wine. The fermentation of the grape must is the result of the action of the yeasts. Dry active yeasts, bought in powder form, are used. They are poured into sugared water to be activated. A gram of powder contains about 30 billion yeast cells!!!

During the pressing of the grapes, a paste that contains the grape seeds and skins is recovered; this is the pomace, which will be used as compost for the vines. Immediately after the pressing of the grapes, the must is placed in enormous fermentation vats at a temperature of 10°C. This step is called the “cuverie”.

Enzymes and sulfur dioxide are added to the must in the vats. The sulfur imparts antioxidant and antibacterial properties to the must, while the enzymes degrade undesirable proteins.

The yeast strain used is called Saccharomyces cerevisiae. The fermentation begins when the yeasts are added to the vats. The transformation of the sugars into alcohol will last 12 days and the wine is kept at 0°C until it is bottled.

Before bottling, the wine is filtered and sterilized to eliminate all the bacteria and the yeasts.

Some wines can be aged for several years, depending on the desired maturity.

Once it is bottled, the wine is ready to be shared in all sorts of activities and celebrations!

To be consumed in moderation .... To your health!

Production Cinémanima inc. and Armand-Frappier Museum

© Production Cinémanima inc. and Armand-Frappier Museum


Learning Objectives

The learner will:
  • familiarize himself with the vocabulary used in microbiology;
  • explain the relationship between developments in imaging technology and the current understanding of the cell;
  • identify which microorganisms are infectious, how the immune system fights against them, and the reinforcements of modern medicine;
  • describe the benefits of microorganisms .

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