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CHECKING YOUR UNDERSTANDING OF PRESERVATION CHEMISTRY
TUTORIAL #B3
Last updated  August 17, 2012

Question 1: Cooking is one of the most common ways to extend the life of food. However, cooking must raise the food to certain temperatures to kill the bacteria in the food. Check the Web for the minimum safe cooking temperature for, let's say, ground beef.
Question 2: Cooking dries food to some extent, but smoking, sun drying, or air drying was used to extend the life of food even more. Nowadays they make dehydrators to assist with this. Find a site that sells food dehydrators. Give the web address for the site. Now as a separate task, see if you can attach an image of a food dehydrator. To get an image off of a Web site, move cursor over it and click right mouse button. (For Mac users just hold mouse over image for awhile) A menu should appear. Choose "Save Picture As..." if using Internet Explorer, or "Save image as..." if using Netscape. When you email your answers, see if you can attach the picture to the email.

Question 3: Without refrigeration, earlier societies had to find other ways to preserve foods. Packing the food in salt was one way. Nowadays not too many foods are preserved that way because we all know that too much salt is bad for you. But search the Web and find a food that is sold packed in salt. (tip: search by using quotes around "packed in salt".

Question 4: The image at the right shows yeast cells that are added to wine to convert sugars to alcohol. Are yeast cells plants, bacteria, fungi, or viruses? (Tip: www.dictionary.com is pretty good for definitions of many things.

Question 5: Garlic is known for its antibiotic capabilities. The first structure, alliin, is contained in garlic but has no antibiotic properties. When crushed, an enzyme (alinase) in the garlic comes in contact with "alliin" and removes the right half . Note: C=carbon, H=hydrogen, S=sulfur, O=oxygen.

The enzyme takes two halves from two Alliin molecules and...

...and as the two halves are joined, water is released.

The result is the compound, "Allicin," which is very antibiotic. This compound gives garlic its known antibiotic properties. So crushed garlic mixed with food will kill bacteria in the food.
However, when cooked, the Allicin breaks down into diallyl-disulfide. Unfortunately, this is no longer antibiotic. Garlic in cooked foods is healthy but the allicin will not be present to kill bacteria in the body. What's the difference between the Allicin molecule above and the diallyl-disulfide molecule shown to the right?

 

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