why are petri dishes kept at 4 degrees after the yeast had grown overnight at 30 degrees.?
355353
The yeast is grown to a point at which it is confluent, or to a point in which the experiment may begin or end- It is then put at 4 degrees to halt the growth process and render it quiescent without killing or freezing it.  The same technique is used for mammalian cells.
215708
that could be the reason, if it was melted long enough for bacteria to form. I know that once you heat up milk you cannot reheat it again or you will get sick.
892657
Well in order to kill all the bacteria and germs in milk, it's pasteurised, thus making it more safe to consume by us. \n\nThey basically boil the milk at a high temperature (over 70 degrees) in order to do so.  \n\n(is that the answer you were looking for?? LOL)
521723
to avoid the configeration damage
973108
I think it is because the yeast only start "eating" and growing at a warm temp so if they are not warmed they will not take in the food coloring. When you warm the yeast they start to eat (I am assuming you have added the food coloring to their food source) causeing them to take in the food coloring as well.
687706
in our religion it is kept and used at another communion service. the reason being the unleavend bread does not contain yeast which can cause it to decompose fast
718884
&#92;\n..&#92;\n..-----&#92;\n........&#92;\n.........&#92;\n(ignore the periods)\nx axis: time\nY axis: temperature\nThe step is there because the nature of cooling objects. As the naphthalene is cooled, its temp first decreases normally. However, when it begins to solidify, the heat being removed is used up as naphthalene molecules are subjected to intermolecular forces and begin to become a solid. Therefore, the horzontal part is where the substance becomes a solid. Finally, when the naphthalene is fully a solid, the temperature decreases again. An easy way to picture this concept is with boiling water. As some water molecules change to the gaseous state, the temperature of the water does not rise above its boiling point. This is equivilent to the horzontal part of the naphthalene cooling curve. As the substance changes states, energy is being generated/used up, and the temperature does not change for a time. When the conversiion is fully made, the temperature continus on its original course.
825792
You have to be more specific.  Microorganisms grow in pretty much every condition on Earth, including hot and sulfurous ocean water by volcanic vents, in ice at the poles, in badly-preserved jars (botulism--anaerobic), inside the body, in ponds, in caves, in the dark, in the sunlight...it all depends on the specific type of microorganism.\n\nFor instance, sugar tends to kill bacteria, but mold loves sugar.  So a jar of jelly left in a fridge for a long time (cold, wet, sugary environment for the microorganisms) might not have bacteria, but it could have fuzzy mold on it.  It all depends.  \n\nBut from a food safety standpoint, you want food kept either below 40 degrees fahrenheit, or above 140 degrees, and keep it wrapped up and covered to avoid stuff dropping in it.  In general, microorganisms like: warm (not hot or cold), dark, moist, and somewhat neutral pH.  That'll grow mold, mildew, fungus, and many types of bacteria.  They usually don't like clean surfaces and they tend to die in chlorine bleach.
44253
Moisture improves heat penetration, making sterilization by moist heat more effective then dry heat. Killing microorganisms by dry heat is a lengthy process that requires high temperatures. On the other hand, most yeasts, molds, and bacteria can be killed using moist heat at 80°C for 10 minutes. These conditions are not sufficient to inactivate mold or bacteria spores, which are more heat-resistant than cells in their vegetative states.\n\nBacterial spores require exposure to moist heat at temperatures of 121°C (achieved under high-pressure conditions) for at least 15 minutes for inactivation. The "gold standard" for heat sterilizatin is inactivation of Bacillus stearothermophilus spores. If heat treatment was sufficient to inactivate test strips containing these spores, then the sterilization is considered successful.\n\nIt is important to note that there are rare types of bacteria which are capable of growing at high temperatures. These bacteria are classified as thermophiles and hyperthemophiles. Bacillus stearothermophilus is a thermophile. These organisms normally growth in unusually hot environments, including hot springs and deep-sea vents. Clearly sterilization by heat may not be the most efficient method to eliminate these types of bacteria, but they are almost never found in common environments.
610904
Temperature about 28 Celsius,yeast 10 per cent of the sugar content,duration of fermentation about a week,and you must add some tartaric or citric acid to make acidic PH
999707
You should have let your idea continue baking, at least three more hours at 450 degrees.  It still may come out undercooked but at least you should be able to convey a coherent thought using complete sentences.
465896
get yourself some pond water, theres more stuff to look at in there that just about anything else.\n\nRubbing alcohol is ok for sterilising, unless your using stuff thats potentually dangerous it will do.\n\nIn your petri dish you put Agar, it's jelly stuff u can buy it  in sachets, its made from seaweed, when u are mixing it up with water u add a drop of nutrient solution, normally specific to what your trying to grow.  The find yourself some bacteria or mold and put them in the petri dish, cover it up and watch.
60336
Because after milk is extracted, it is then cooled in the dairy and transported in refrigerated tankers for processing. Unchilled milk would soon go sour due to acid production by lactobacilli. Even if kept refrigerated, raw milk goes off rapidly due to the action of psychrophilic (cold-tolerant) bacteria. These produce proteinases and lipases which break down both the protein and the fat in milk, causing rancid and bitter tastes and clotting. \n\nOne unusual type of bacteria which can grow is called Alcaligenes viscolactis – this produces sticky threads of exopolysaccharide in the milk called ropiness.\n\n:)\nPeace
327007
Since no has taken a stab at this yet, I'll try:\n\n  As an experiment, food was first cooked (to kill germs)\nand then stored in air-tight bottles. It was taken aboard an \nEnglish ship. After a couple of months the bottle was opened\nand the food was found not to have spoiled.\n  A sheet metal worker found out about this, and thought \nabout storing food in cans instead. James Burke discusses \nthis in one of the Connections Programs. I've included a \nlink in the sources part.\n  There is no reason the surface area of the can would vary\nbetween now and then unless the cans were first made with \na square bottom. I don't believe it was.
158364
Many people theorize that this was a sanitary issue, albeit one that came about before our modern understanding of hygiene. Milk products can act as a growth medium for bacteria found in uncooked or spoiled meat, so the mixing of them was prohibited.
1102012
the change back to room temp. with the alcohol  in the mix is what causes it. I used to own a bar and I would keep the coolers at about 28 degrees  the beer wouldnt be froze till you took it out and opened it  then it would freeze right in front of the customer,,,,,, they just loved it  ,,,,, they knew they were getting the coldest beer in town.!!!!!!\n\nS
383260
It is O.K if you cook it on 70degrees because virus destroys at that temperature.