Mold grows on cheese when it is placed in a badly ventilated or moist area. Mold spores are airborne all around us, invisible to the naked eye. And if one spore makes it onto a piece of cheese, it can begin to reproduce rapidly and feed off of the cheese.
The amount of mold that grows on cheese depends on the type of cheese as well. There are soft, semi soft, semi hard or hard cheeses produced, and the softer the cheese, the quicker the chances it can grow mold. Most soft cheeses are more watery, and are also the freshest cheeses, and will facilitate more growth if it comes into contact with mold.
Friday, May 21, 2010
Sunday, April 11, 2010
HOW LONG DOES IT TAKE TO GROW MOLD ON BREAD?
Question: We are trying to grow mold on bread for a science experiment. It's been 3 days and still nothing. How long does it take before visible spores start to develop. Answer: You may not be getting mold because the bread may have preservatives that prevent bacterial growth. Bread without preservatives (sodium propionate) is a wonderful medium for growing mold. Here are some tips to harbor the growth of mold:Check the ingredients of the bread, we want white bread without propionates.Put five to 10 drops of water on the piece of bread and store it in a Ziploc bag in a warm place. After seven to 10 days, you should notice some fuzzy white, black, orange or green spots on the bread. The green color is typically a mold called Penicillium (from which penicillin is made). Once visible, the mold will grow noticeably each day.
WHAT TYPE OF BREAD MOLDS THE FASTEST?
How quickly a bread will mold depends on several things, one being the "water activity" of the bread. An earlier Mad Scientist message gave the following information about bread molding:"Scientists measure "water activity", that is water that is not bound into the product, to help determine "shelf life", or how long a product can remain on the shelf and be edible. Pure water has an activity of 1.0 and 0 is bone dry. Bacteria generally stop growing at a water activity less than .91, but molds grow on drier foods, until the water activity drops below .81. Bread has a water activity of about .95. However, another factor about bread that determines how quickly it spoils is its pH (or acidity). Bread has a pH of about 5.3 - 5.8 which means it is slightly acid. This also helps keep it safe to eat on the shelf."One way to estimate how quickly bread will mold would be to look at its water content. For example the percent of water in several breads is: Navaho fry bread 26%, banana bread 29%, toasted white bread 30%, plain white bread 36%, Oat bran bread 44% and canned Boston brown bread 47%. But this is not the whole story, because other ingredients in the bread may affect the "water activity". Water activity is measured by putting a bread sample in a tight container and measuring the amount of water that vaporizes from the product. If you want to learn more about how food producers determine the water activity of their bread visit the web sites of manufacturers who make the instruments bread makers use to test their product. One place to study this question is at the following. The bottom line is that the dryer the bread the less likely it is to mold. Toasting bread slows subsequent mold growth, as does refrigerating bread. And much commercial bread contains a chemical to slow mold growth. The best policy is to buy only as much bread as you can eat within a few days or store bread in the refrigerator or freezer until needed.
WHAT IS MOLD?
Mold is something that we often take for granted, as something that makes us have to throw the bread away or the cheese smell bad.
Mold is, in fact, a fascinating organism which has had many different uses over the years and our lives would not be the same without it.
Most of us know that food seems to become moldy more quickly in the summer, when it is warm, than in the winter when it is colder. Food in refrigerators seems to keep longer than food left out in the sun. Is this true? Does temperature really affect the rate at which mold grows?
Mold is, in fact, a fascinating organism which has had many different uses over the years and our lives would not be the same without it.
Most of us know that food seems to become moldy more quickly in the summer, when it is warm, than in the winter when it is colder. Food in refrigerators seems to keep longer than food left out in the sun. Is this true? Does temperature really affect the rate at which mold grows?
How Does Mold Grow?
This experiment uses 4 samples to test what conditions mold grow the best in. Depending on the age of the child(ren) you can use only 2 or 3 samples instead of all 4.
What you need:
bread (4 slices)
water
saran wrap (or some other air tight covering)
1 to 2 weeks of experiment time
Optional: Magnifying glass
Optional: Molds Printable Information Sheet
Optional: Molds Printable Activity Sheets (page 1) (page 2) (page 3) (page 4)
I prefer to print page 1 as many times as the children need. They can mark the date and sample number on each page. This allows them to draw the results.
But, it is a fair amount of work, so you may prefer to use Pages 2 thru 4 instead so they can just jot down what they see, perhaps using page 1 on the last day of the experiment.
Safety Thoughts:
Some people are allergic to molds. If this is a concern, skip the first sample (just use the last 3) and seal each of them in a clear glass jar, so the child(ren) can examine them without being exposed to the molds.
Directions:
SAMPLE 1: Take a piece of bread and slice it in half (it can be a few days old, but ensure it isn't too stale). Seal one half in saran wrap and expose the other to air.
SAMPLE 2: Take another piece of bread and slice it in half. Leave one half in the dark (a paper bag or cupboard) and the other half in strong light (sunlight works).
SAMPLE 3: Take a third piece of bread and slice it in half. Keep one half very dry and put about 1 tsp of water on the other half. (Spritz the wet piece with a few drops of water each day).
SAMPLE 4: Take a fourth piece of bread and put half of it someplace warm, in the dark (on top of the fridge in a paper bag) and the other half someplace cold in the dark (the refrigerator).
Examine the samples each day with your naked eye or a magnifying glass and record any changes in appearance.
What happened:
Molds will develop on some of the samples.
Molds grow best in warm, dark and moist conditions.
In the first sample, the sealed bread should develop mold more slowly than the unsealed bread.
In the second sample, the bread kept in darkness should develop mold more quickly than the bread kept in light.
In the third sample, the moist bread will develop mold more quickly than the dry bread.
In the fourth sample, the mold in the warm place should develop mold more quickly than the bread in the cold place.
Questions to Ask:
Where and how should bread be stored to keep it free from molds?
What other foods do you think might grow molds if left exposed?
What are some ways that people use to preserve their food?
Possible Answers:
someplace sealed, in the refrigerator, in the light, someplace dry, someplace cool
cheese, oranges, tomatoes, lemons, onions, used coffee grounds, potatoes (determining what foods mold the best can be an entirely different experiment!)
refrigerator, artificial preservatives, natural preservatives like vinegar and salt, tupperware
What you need:
bread (4 slices)
water
saran wrap (or some other air tight covering)
1 to 2 weeks of experiment time
Optional: Magnifying glass
Optional: Molds Printable Information Sheet
Optional: Molds Printable Activity Sheets (page 1) (page 2) (page 3) (page 4)
I prefer to print page 1 as many times as the children need. They can mark the date and sample number on each page. This allows them to draw the results.
But, it is a fair amount of work, so you may prefer to use Pages 2 thru 4 instead so they can just jot down what they see, perhaps using page 1 on the last day of the experiment.
Safety Thoughts:
Some people are allergic to molds. If this is a concern, skip the first sample (just use the last 3) and seal each of them in a clear glass jar, so the child(ren) can examine them without being exposed to the molds.
Directions:
SAMPLE 1: Take a piece of bread and slice it in half (it can be a few days old, but ensure it isn't too stale). Seal one half in saran wrap and expose the other to air.
SAMPLE 2: Take another piece of bread and slice it in half. Leave one half in the dark (a paper bag or cupboard) and the other half in strong light (sunlight works).
SAMPLE 3: Take a third piece of bread and slice it in half. Keep one half very dry and put about 1 tsp of water on the other half. (Spritz the wet piece with a few drops of water each day).
SAMPLE 4: Take a fourth piece of bread and put half of it someplace warm, in the dark (on top of the fridge in a paper bag) and the other half someplace cold in the dark (the refrigerator).
Examine the samples each day with your naked eye or a magnifying glass and record any changes in appearance.
What happened:
Molds will develop on some of the samples.
Molds grow best in warm, dark and moist conditions.
In the first sample, the sealed bread should develop mold more slowly than the unsealed bread.
In the second sample, the bread kept in darkness should develop mold more quickly than the bread kept in light.
In the third sample, the moist bread will develop mold more quickly than the dry bread.
In the fourth sample, the mold in the warm place should develop mold more quickly than the bread in the cold place.
Questions to Ask:
Where and how should bread be stored to keep it free from molds?
What other foods do you think might grow molds if left exposed?
What are some ways that people use to preserve their food?
Possible Answers:
someplace sealed, in the refrigerator, in the light, someplace dry, someplace cool
cheese, oranges, tomatoes, lemons, onions, used coffee grounds, potatoes (determining what foods mold the best can be an entirely different experiment!)
refrigerator, artificial preservatives, natural preservatives like vinegar and salt, tupperware
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