Yeast fresh

One day while I was examing a suspension of yeast freshly prepared from a few bits of compressed yeast shaken vigorously with a little water in a test-tube, I failed to find the characteristic four-banded absorption spectrum, but before I had time to remove the suspension from the field of vision of the microspectroscope the four absorption bands suddenly reappeared. This experiment was repeated time after time and always with the same result the absorption bands disappeared on shaking the suspension with air and reappeared within a few seconds on standing. 

Sources. Only bacteria can synthesize vitamin B12. Vitamin B12 is present in animal products such as meat, poultry, fish (including shellfish), and to a lesser extent milk, but it is not generally present in plant products or yeast. Fresh pasteurized milk contains 0.9 p.g per cup and is an important source of vitamin B12 for some vegetarians. Those vegetarians who eat no animal products need supplemental vitamin B12 to meet their requirements. 

Sulfur Dioxide and Sulfites. Sulfur dioxide [7446-09-5], SO2, sodium bisulfite [15181-46-1], NaHSO, and sodium metabisulfite [23134-05-6] ate effective against molds, bacteria, and certain strains of yeast. The wine industry represents the largest user of sulfites, because the compounds do not affect the yeast needed for fermentation. Other appHcations include dehydrated fmits and vegetables, fmit juices, symps and concentrates, and fresh shrimp (79). Sulfites ate destmctive to thiamin, and cannot be used in foods, such as certain baked goods, that ate important sources of this vitamin. 

Seafood. Sorbates are used to extend the shelf life of many seafood products, both fresh and processed (103,104). For smoked or dried fish, an instantaneous dip in 5 wt % potassium sorbate or a 10-minute dip in 1.0 wt % potassium sorbate prior to drying or smoking inhibits the development of yeast and mold (105,106). For fresh fish, sorbates can be incorporated at approximately 0.5 wt % into the ice, refrigerated seawater, or ice-water slush in... 

Active dry yeasts of improved quality have been available for many years, and more recently instant active dry yeast has been introduced (15,20). This instant yeast exhibits more activity than regular active dry yeast due to improved drying techniques, and can replace compressed yeast at a rate of 33 —40%. Dried yeasts, which are stable for long periods of time at room temperature, are of interest to bakers because of the high distribution cost of fresh compressed yeast. This is especially tme for those away from distribution centers and for smaller bakers whose usage rate of yeast is low. 

Folic acid is a member of the vitamin B complex found in green plants, fresh fruit, yeast, and liver. Folic acid takes its name from folium, Latin for leaf. Pterin compounds are named from the Greek word for wing because these substances were first identified in insect wings. Two pterins are familiar to any child who has seen (and chased) the common yellow sulfur butterfly and its white counterpart, the cabbage butterfly. Xanthopterin and leu-... 

The volume of reactor without beads was 1.4 1. The column was loaded with the solidified uniform beads of S. cerevisiae. The void volume of the reactor was 660 ml when it was packed with immobilised beads. The growth of beads with different proportions of column packing is shown in Figure 8.9. A fresh feed of 10 g l 1 glucose solution was pumped from the bottom of the reactor. The optimum amount of packing obtained was 65-70% of the reactor volume. The trend of the collected data resembles the growth curve of yeast in... 

Sodium bisulfite is used in almost all commercial wines to prevent oxidation and preserve flavor. It releases sulfur dioxide gas when added to water or products containing water. The sulfur dioxide kills yeasts, fungi, and bacteria in grape juice before fermentation. When the sulfur dioxide levels have subsided, after about twenty-four hours, fresh yeast is added for fermentation. 

Martinez, L. et al.. Comparative effect of red yeast rice Monascus purpureas), red beet root (Beta vulgaris) and betanin (E-162) on colour and consumer acceptability of fresh pork sausages packaged in a modified atmosphere, J. Sci. Food Agric., 86, 500, 2006. 

The distinctive aroma of ammonia is often apparent in bakeries but not in the final product. Bakers yeast performs its leavening function by fermenting such sugars as glucose, fructose, maltose, and sucrose. The principal products of the fermentation process are carbon dioxide gas and ethanol, an important component of the aroma of freshly baked bread. The fermentation of the sugar, glucose—an example of a decomposition reaction — is given by the equation in Fig. 5.19.1. 

Sy, K.V., Murray, M.B., Harrison, M.D. and Beuchat, L.R. (2005b) Evaluation of gaseous chlorine dioxide as a sanitizer for killing Salmonella, Escherichia coli 0157 H7, Listeria monocytogenes, and yeasts and molds on fresh and fresh-cut produce . Journal of Food Protection, 68, 1176-1187. 

A procedure that is described by Tollens and Eisner4 is probably suitable for materials less pure than fresh dahlia juices. The juice is expressed in the presence of calcium carbonate, fermented at 25° with baker s yeast, defecated with lead acetate and filtered. After removal of the excess lead with hydrogen sulfide, the filtrate is frozen and thawed to cause the separation of inulin. 

Bacteria occur normally in fresh fruit and vegetable tissues. A wide variety of microorganisms have been found on fresh fruits and vegetables, which include mesophilic bacteria, lactic acid bacteria, coliforms, and yeasts and molds (Nguyen-The and... 

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