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Color of yeast: A Colour Reaction in Yeast

A Colour Reaction in Yeast

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volume 156, pages 52–53 (1945)Cite this article

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AFTER being dried at 90° C., bakers’ yeast pre-treated with sodium fluoride assumes a more or less strong red colour, all according to the pH of the solution in which the yeast has been shaken. On the other hand, untreated yeast assumes a yellow colour after drying. With concentrated hydrochloric acid there is obtained from the red yeast a wine-red extract, which has a pronounced maximum at 4900 A. Fig. l shows the absorption spectrum of the extract in half concentrated hydrochloric acid.

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  1. Wenner-Gren’s Institute for Experimental Biology, University of Stockholm,




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Causes and when to see a doctor

Vaginal discharge color guide: Causes and when to see a doctor

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Medically reviewed by Holly Ernst, P. A. — By Nicole Galan, RN — Updated on March 31, 2023

Vaginal discharge can be many colors. Different discharge colors can indicate different health conditions such as infections and menstruation.

In this article, we provide a color-coded guide to vaginal discharge. Learn what the colors mean and when to see a doctor.

Vaginal discharge is fluid secreted from tiny glands in the vagina and cervix. This fluid leaks from the vagina each day to remove old cells and debris, keeping the vagina and reproductive tract clean and healthy.

The amount of vaginal discharge can vary significantly from person to person. The color, consistency, and amount can also change from day to day, depending on where a person is in their menstrual cycle:

  • Days 1–5. At the beginning of the cycle, discharge is usually red or bloody, as the body sheds the uterine lining.
  • Days 6–14. Following a period, a person may notice less vaginal discharge than usual. As the egg starts to develop and mature, the cervical mucus will become cloudy and white or yellow. It may feel sticky.
  • Days 14–25. A few days before ovulation, the mucus will be thin and slippery, similar to the consistency of egg whites. After ovulation, the mucus will go back to being cloudy, white or yellow, and possibly sticky or tacky.
  • Days 25–28. The cervical mucus will lighten, and a person will see less of it, before getting another period.

The shade of red can vary from bright to a dark rust color. Red discharge is most commonly the result of bleeding during a period.

Menstrual bleeding happens, on average, around every 28 days, though the normal range between 21 and 35 days. A period typically lasts for 3–5 days.

Anyone who experiences bleeding between menstrual periods should see a doctor. Though there are many benign causes of intermenstrual bleeding, it can sometimes signal a serious condition.

Anyone who has gone through menopause and not had a period for at least 1 year should see a doctor if they experience vaginal bleeding. It can sometimes be a sign of endometrial cancer.

The shade of white can extend to include cream or light yellow. If a person has no other symptoms, white discharge is most likely a sign of healthy lubrication.

However, if the white discharge has a consistency like cottage cheese or is accompanied by a strong odor, it can indicate an infection. An individual should see a doctor.

White, thick, strong-smelling discharge is usually associated with a yeast infection, which can also cause itching or irritation.

If the discharge has a very slight yellow hue, it may not indicate a problem. This is especially likely if the hue only coincides with a change in diet or dietary supplements.

Discharge that is a darker shade of yellow, yellowish-green, or green usually signals a bacterial or sexually transmitted infection. See a doctor promptly if vaginal discharge is thick or clumpy, or it has a foul odor.

Discharge can be light or a much deeper pink. It usually contains a little bit of blood.

Pink discharge most commonly occurs with spotting before a period. However, it can also be a sign of implantation bleeding in early pregnancy.

Some people experience a little bit of spotting after ovulation, which can also cause pink discharge.

Discharge can be pink after sexual intercourse if the sex has caused small tears or irritation in the vagina or cervix.

Most ordinary vaginal discharge is clear or whitish. It may be slippery or have the consistency of egg whites.

A person is likely to experience more clear, slippery discharge just before ovulation, during sexual arousal, and during pregnancy.

Gray vaginal discharge is not healthy, and it can be a symptom of a common bacterial infection called bacterial vaginosis (BV).

BV usually causes other vaginal symptoms as well, including:

  • itching
  • irritation
  • a strong odor
  • redness around the vulva or vaginal opening

Anyone with gray discharge should promptly see a doctor. Following diagnosis, the doctor will usually prescribe antibiotics to treat the BV.

Share on PinterestDiscuss any unexplained changes in vaginal discharge with a doctor.

See a doctor if vaginal discharge has an unusual smell or appearance. A person should also seek medical care if they experience vaginal symptoms such as:

  • itching
  • pain or discomfort
  • discharge that is frothy or like cottage cheese
  • bleeding between periods or after menopause
  • spotting after sex regularly
  • grey, green, or yellow discharge
  • a strong odor
  • a burning sensation during urination

The doctor will perform a pelvic exam. They may also need to take a sample of discharge for testing.

Below is a summary of causes for each color of vaginal discharge:

  • starting or ending a period
  • cervical infection
  • cervical polyp
  • endometrial or cervical cancer
  • cervical bleeding
  • irritation in the vagina
  • implantation bleeding
  • healthy discharge
  • yeast infection
  • sexually transmitted infection, such as trichomoniasis
  • healthy discharge
  • pregnancy
  • ovulation
  • hormonal imbalances
  • BV

In most people, infections or hormonal imbalances are responsible for unusual changes in vaginal discharge. Medication may be necessary.

A person should see a doctor if they notice irregular changes in vaginal discharge or other symptoms that might indicate a reproductive health issue.

Last medically reviewed on January 10, 2020

  • Infectious Diseases / Bacteria / Viruses
  • Pregnancy / Obstetrics
  • Sexual Health / STDs
  • Women’s Health / Gynecology
  • Cat 1
  • vaginalhealth

How we reviewed this article:

Medical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

  • 5 Types of vaginal discharge & what they mean. (n.d.)
  • Barad, D. (n.d.). Vaginal discharge
  • Vaginal discharge. (2013, October)
  • Vaginal discharge. (2014, April 1)
  • Vaginal discharge. (2017, November 28)
  • Vaginal discharge. (2018, January 22)
  • What’s the cervical mucus method of FAMs? (n.d.)

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Medically reviewed by Holly Ernst, P. A. — By Nicole Galan, RN — Updated on March 31, 2023

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Yeast: composition, types and parameters affecting activity. Yeast application details

Beer sediment was a top fermenting yeast. Nothing was known about the types and races of yeast; the plant nature of yeast and their composition were established in 1835-1836. and somewhat later, thanks to the improvement of the microscope and the emergence of methods for isolating pure cultures of microorganisms.

In 1850, a method was discovered for the production of pressed yeast for bread baking: it was yeast obtained from distilleries. The yeast contained in the foam, from the fermentation vats through the chutes placed along the vats, entered the yeast collectors. Then it was washed out, mixed with cold water in settling tanks, and the resulting precipitate was pressed out on screw presses.

Louis Pasteur’s discovery of the influence of atmospheric oxygen on the vital activity of yeast and the rapid development of mechanical engineering made it possible to manufacture yeast in factories. So in 1872, the first Lesaffre yeast factory appeared in the city of Marc-en-Barolles in northern France. Since then, yeast has become the concern’s main research and production product.

Yeasts (Saccharomyces cerevisiae) are microorganisms belonging to the group of unicellular fungi, which includes about 1500 species. Yeast cells are spherical or oval in shape, 3-7 microns in diameter. 1 g of live yeast contains 10 billion cells. This is such a huge amount that if all the cells contained in 0.5 kg of yeast are lined up in one line, a chain 42,000 km long is formed. That’s more than one revolution around the Earth!

What is a yeast cell made of?

  • Shell: 18% polysaccharides (SS)
  • Cell membrane: lipids, lipoproteins, proteins
  • Intracellular constituents: itoplasm, nucleoli, protein-rich organic compounds, nucleic acids and their metabolic products, amino acids, peptides, vitamins 9 0014

Average composition of yeast

  • Dry matter: 30-33%
  • Nitrogen: 6. 5-9.3% (to dry matter)
  • Protein: 40-58%
  • Carbohydrates: 35-45%
  • Fats: 4-6%
  • Minerals: 5-7.5%
  • Vitamins: B1, B2, B6, PP

Parameters affecting yeast activity 900 11

Yeast can survive in a variety of environments

In the presence of oxygen (aerobiosis) and nutrients (sugar) yeast consumes O2 and glucose to produce CO2, water and heat. The energy produced by the yeast is consumed for their reproduction. This reaction is used by yeast manufacturers when producing yeast.

In the absence of oxygen (anaerobiosis) – yeast ferments. Yeast transforms glucose into:

  • CO2;
  • alcohol;
  • flavoring substances;
  • small amount of heat.

This reaction is used in baking.

Parameters affecting yeast activity

1. Temperature

2. Yeast dosage

The higher the yeast dosage, the faster the fermentation.

3. pH

4.5 to 6 is the optimum limit for yeast activity. The pH of direct baked bread is in the range of 5.6 – 5.7.

4. Hydration

Water facilitates yeast activity by dissolving fermentables and improving cell motility.

5. Concentration and type of sugars

90 089 28/34

90 088

Pressed yeast Dry active yeast Dry
instant yeast
Semi-dry frozen yeast
Water (%) 66/72 7/8 4/6 20/26
CB (%) 92/93 94/96 74/80
Shelf life 4 – 5 weeks 2 years 2 years 2 years 900 92
Storage conditions (°C) 0…+6 Room temperature Room temperature — 18…- 24
How to use Direct application Dilute in water and mix into the batch Direct application Direct application
Pressed yeast in bars has limited contact with air. Yeast contains reserve sugars, thanks to which they retain their lifting power. The energy requirement is minimal if the storage conditions are observed. Consistency, color and friability varies depending on the country of use. Stable at room temperature. The dead cells that form the shell protect the live yeast against oxidation and moisture -> slight reducing effect.

9008 8

Highly active deactivated
Recipe < 10% sugar > 10% sugar Hard flour
Process Direct, frozen Direct, op arny, freezing Dough that needs to be stretched
Product Breads Pastry, puff Pizza, flat breads, puff, products for industrial lines
Benefits Stability Osmotic stability Extensibility

Compressed yeast

Compressed yeast is the traditional form of yeast. Rectangular blocks of fresh yeast packaged in different types of packaging materials (paper, foil, cellophane, etc.). This type of yeast is the most used in industrialized countries.

Packed yeast is kept in the refrigerator for 2 days to ensure uniform cooling to a temperature of 4-7 degrees before being sent to the refrigerator warehouse. Pressed baker’s yeast is stored in refrigerators at a temperature of 0-4 and a relative humidity of 80-96%.

Due to relatively high humidity, pressed yeast must be stored at a constant low temperature, otherwise it may lose its gassing capacity. Long term storage temperature ranges from 0 to 3 C. At a temperature of 7 C, yeast loses 3-4% of its activity per week. If the yeast is stored at 35C, it will lose more than 50% of its activity in 3-4 days and cause the dough to thin out due to dead yeast cells containing glutathione.

Pressed yeast can vary in color from dark brown to almost white, and the texture can vary from crumbly to plastic, smearing. Appearance depends on yeast strain, molasses source, fermentation conditions, moisture content, and yeast age.

Dry yeast

Dry (dried) yeast has all the advantages that dry products have: stable quality, long shelf life, wide temperature range, ease of transportation and storage.

Dry active yeast

The production of dry active yeast is carried out according to the technology used for pressed yeast before the pressing stage.

Instead of pressing, the yeast mass is extruded through perforated plates into thin threads, which are cut into fragments. The resulting material is then dried in dryers.

In practice, the coefficient of replacement of pressed yeast for dry active is selected according to the lifting force. This ratio is generally higher than would be expected on a dry matter basis. The gas-forming capacity of dry active yeast is initially lower than that of fresh yeast, since the inevitable loss of viable cells occurs during drying.

Instant Dry Yeast

This form of dry yeast differs from conventional yeast in that it is a free-flowing product that does not require rehydration before being added to the dough. Due to the low humidity, one part can replace three parts of pressed yeast by weight.

Just like other types of dry yeast, instant yeast does not require special storage conditions and remains active at room temperature as long as the bag remains sealed and under vacuum. Under these conditions, the loss of activity usually does not exceed 1% per month.

Instant yeast is sensitive to cold water during rehydration. This should be taken into account when kneading dough with ice.

When using active yeast, the kneading time is usually reduced. This is due to the leaching of glutathione from non-viable cells, a reducing agent that affects gluten proteins. But in instant yeast, during drying, a shell of deactivated cells, the source of glutathione, is not formed. Therefore, when working on slow kneading equipment, it will take more time for instant yeast granules to rehydrate and evenly distribute throughout the dough compared to pressed ones.

Osmotolerant yeast

Osmotolerant yeast is ideal for high sugar recipes. Osmotolerant yeast is rich in trehalose (osmoprotectant), which makes the cell stronger “from the inside”. On the other hand, due to the low content of the invertase enzyme compared to the normal strain, the consumption of sugar by the yeast is slow and gradual. Therefore, in a dough containing a large amount of sugar, the yeast cell maintains a stable metabolism and its enzymatic abilities are not disturbed. The increased content of trehalose and glycerol compensates for the high osmotic pressure (pressure on the cell “outside”) is reduced – the main cause of yeast cell death.

Liquid wine yeast – for white and red wines symbol:400190

Product description:

We owe wines made from grapefruit to microorganisms – in particular to a large group of yeasts belonging to the genus Saccharomyces cerevisiae and Saccharomyces bayanus. Used in winemaking, specially selected and processed in laboratories, noble wine yeasts are divided into a number of races, depending on substrate preferences (type of fruit, sugar concentration), speed and productivity of alcohol production. – Yeast is offered as a suspension in a special protective liquid; volume 20 ml. They are in the form of a light brown sediment in a sachet. Shake the sachet well before using them to make the liquid cloudy.

A single dose after propagation is enough to make up to 25 liters of wine.

The offer includes the following strains of yeast:

Burgundy G for red wines, both table and dessert; from fruits with a high content of tannin, such as chokeberry, plum, black grapes, elderberry, cherry, black and red currants, blackberries and blueberries.

Bordeaux G for red table wines; from fruits such as blueberries or grapes

Malaga G for red dessert wines; from fruits such as black grapes or chokeberry.

Madeira G for white and red dessert wines; fruits such as gooseberries, pears, raspberries, apricots, strawberries, red and white currants, raisins, and cereals.

Port wine G for white and red dessert wines; from fruits such as cherries, blackberries, black and white currants.

Tokay – for white dessert and table wines; from fruits such as gooseberries, hawthorn, pears, apples, rhubarb, apricots, rose hips, strawberries, white grapes, white currants and raisins, as well as from cereals.

Sherry G for white dessert wines, from fruits such as cherries, apples, hawthorn, rose hips, white grapes, white currants and raisins, as well as from cereals.

All of the above breeds allow the production of wines with an alcohol content of up to 14%.

Yeast of the race deserves special attention:

Universal – for white and red wine and from any fruit characterized by high resistance to alcohol up to 18%.

In the case of a yeast suspension, pre-propagation of the yeast is recommended. This procedure is called – preparation of dressing yeast, in other words, royal yeast.