Tea yeast:
In the frozen mountain area of Taiwan Province Province, when people make oolong tea, they will first kill the tea leaves and then ferment them at low temperature. After fermentation, the yeast will retire and settle at the bottom. But at this time, the yeast has already absorbed the essence of oolong tea, and after cleaning, disinfection and drying, it has become a tea yeast.
There are three kinds of tea yeast in the market: the yield of tea yeast processed as above is low, and there is basically no yield, because it is difficult to collect after being separated from tea; Oolong tea and fermentation broth are dried together and crushed into powder, which is basically oolong tea and contains almost no yeast; Oolong tea extract is combined with beer yeast extract. The product is easy to collect and process, and can be produced on a large scale. Tea yeast has a wide range of uses, and the most popular one is suitable for slimming.
Tea yeast containing tea polyphenols, its antioxidant capacity is more than E 10 times higher than that of vitamin e, which can reduce the content of neutral fat in blood and effectively reduce blood lipid. It can also improve the alkaloids of listlessness and lethargy caused by obesity and hyperlipidemia, and make you feel refreshed. Beer yeast-contains more abundant vitamin B, which is three times that of tea yeast, and yeast chromium is twice that of tea yeast. B vitamins can accelerate the metabolism of carbohydrate and fat, consume calories quickly, and make people energetic while losing weight; Yeast chromium reduces neutral fat and helps insulin accelerate sugar metabolism.
The concept of real tea yeast should be like this: it contains effective ingredients such as oolong tea to lose weight and has the characteristics of yeast. Beer yeast is also a hot-selling product to lose weight, which shows that yeast itself is effective in losing weight, while tea yeast has the advantage of combining the characteristics of tea and yeast to lose weight, which is healthier, more effective and safer.
brewer's yeast
Yeast used for brewing beer. Most of them are different kinds of Saccharomyces cerevisiae. E.C. Hansen (1883) began to isolate and cultivate yeast, and used it to brew beer. The following yeasts from Carlsberg Brewing Institute in Denmark are famous. Other famous beer yeasts are German Saaz type bottom yeast and British and Japanese top yeast. The cell morphology is the same as other cultured yeasts, and it is a nearly spherical ellipsoid, which is different from wild yeast. Beer yeast is a typical upper fermentation yeast commonly used in beer production. Besides brewing beer, alcohol and other drinks, bread can also be fermented. The strain is rich in vitamins and protein, and can be used as edible, medicinal and feed yeast, and cytochrome C, nucleic acid, glutathione, blood clot, coenzyme A and adenosine triphosphate can also be extracted from it. In microbial determination of vitamins, biotin, pantothenic acid, thiamine, pyridoxine and inositol are usually determined by beer yeast.
The colony of beer yeast on wort agar medium is milky white, shiny, flat and tidy. The asexual reproduction is mainly budding. It can ferment glucose, maltose, galactose and sucrose, but not lactose and melibiose.
According to the length-width ratio of cells, beer yeast can be divided into three categories. The first group of cells are mostly round, oval or oval (cell length/width; 2)。 This yeast is resistant to high osmotic pressure and high salt concentration, and is suitable for producing alcohol from sugarcane molasses.
Bread yeast
It is divided into pressed yeast, active dry yeast and fast active dry yeast. Squeezed yeast: a block product with water content of 70 ~ 73% produced by Saccharomyces cerevisiae. Pale yellow, compact structure, easy to crush and strong fuzzing ability. The product that can be stored at 0℃ for 2 ~ 3 months is originally obtained by squeezing and dewatering the centrifuged yeast milk with a plate-and-frame filter press, so it is called squeezed yeast, commonly known as fresh yeast. Fresh compressed yeast should not be refrigerated for too long. If the storage time is too long, the yeast will turn brown, and if the cold storage time is prolonged, the role of yeast as a starter will be reduced. When fermenting, its dosage is 65438+ 0 ~ 2% of flour, and the fermentation temperature is 28 ~ 30℃. If the temperature exceeds 54℃, the yeast will lose its activity. The fermentation time varies with the amount of yeast, fermentation temperature and sugar content of dough, and is generally 1 ~ 3 hours. Active dry yeast: a kind of dry yeast product, with a water content of about 8%, is granular and has the ability to ferment dough. Fresh yeast is made by cultivating dry-resistant and stable yeast, then extruding and drying. The fermentation effect is similar to that of pressed yeast. Products are packed in aluminum foil bags or metal cans filled with vacuum or inert gas (such as nitrogen or carbon dioxide), and the shelf life is from half a year to 1 year. Compared with pressed yeast, it has the advantages of long shelf life, no need for low temperature storage, convenient transportation and use. Fast-active dry yeast: a new product with fine particles (diameter less than 1mm) that can be fermented quickly and efficiently. The moisture content is 4-6%. On the basis of active dry yeast, it adopts genetic engineering technology, through special nutrition ratio and strict proliferation and culture conditions, and dries with fluidized bed drying equipment to obtain a highly dry-resistant Saccharomyces cerevisiae strain. Like active dry yeast, the shelf life is longer than 1 year if it is stored in vacuum or filled with inert gas. Compared with active dry yeast, its particles are smaller and its fermentation ability is higher. When in use, it can be directly mixed with flour and added with water to make dough for fermentation, and can be baked into food after fermentation in a short time. In the actual production of bread, yeast fermentation is influenced by the following factors:
Temperature: within a certain temperature range, with the increase of temperature, the fermentation speed and gas production of yeast will also increase, but the maximum should not exceed 38℃ ~ 39℃. Generally, the normal temperature should be controlled at 26℃ ~ 28℃, and if the rapid production rule is adopted, it can't exceed 30℃, because if it exceeds this temperature, the dough will ferment too fast, the dough will not be fully mature, and the gas retention ability will be poor, which will affect the quality of the final product.
PH value: The PH value of dough is between 4 and 6.
The role of sugar: The sugars that yeast can directly use are glucose and fructose. Sucrose needs to be decomposed into glucose and fructose by invertase in yeast, and then it provides energy for fermentation. There is also maltose, which is obtained by decomposing broken starch in flour by amylase in flour, and can also be used after being converted into 2 molecules of glucose by maltase in yeast.
Osmotic pressure: Osmotic pressure refers to the extra pressure added to the solution to prevent osmosis. The osmotic pressure of external culture medium has great influence on yeast activity. Because the outer membrane of yeast cells is a semi-permeable membrane, which has osmotic effect, the concentration of external culture medium will directly affect the vitality of yeast, and high concentration of soluble solid substances such as sugar, salt and inorganic salt will cause high osmotic pressure and inhibit yeast fermentation. The reason is that when the concentration of external culture medium is high, protozoa in yeast ooze out of cell membrane, protoplasm is separated, and yeast is destroyed and cannot survive. In this respect, dry yeast has stronger adaptability than fresh yeast. Of course, some yeasts can survive and ferment at high concentrations.
In bread production, osmotic pressure is mainly affected by sugar and salt. When the sugar content in the formula is 0 ~ 5%, yeast fermentation is not inhibited, but it can be promoted. When it exceeds 6%, it will inhibit fermentation. If it exceeds 10%, the fermentation speed will obviously slow down. Among glucose, fructose, sucrose and maltose, the inhibitory effect of maltose is less than the first three sugars, because the osmotic pressure of maltose is lower than other sugars.
The higher the osmotic pressure of salt, the greater the inhibitory effect on yeast fermentation. When the amount of salt reaches 2%, fermentation will be affected. Feed yeast: usually cultivated and dried by Candida or Kluyveromyces fragilis, it has no fermentation power and the cells are in a state of death. It is rich in protein (about 30 ~ 40%), B vitamins, amino acids and other substances, and is widely used as a protein supplement for animal feed. It can promote the growth and development of animals, shorten the feeding cycle, increase the amount of meat and eggs, improve the meat quality and lean meat rate, improve the luster of fur and enhance the disease resistance of young animals.