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Final

Final Readings Notes

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Department
Chemistry
Course
CHEM 181
Professor
David Harpp
Semester
Winter

Description
World of Chem: Food Final Readings Final Readings Enhancing Taste with MSG (166-171)  Dashi is an extract of a seaweed known as kombu. The taste of dashi is mild but when added to other foods it brought out their flavours. Thus it was given then name umami meaning „delicious‟.  Monosodium glutamate was first sold as a table condiment called Aji-no-moto (essence of taste)  Msg has been accused of causing hypertension, asthma, depression, ADD and “Chinese Restaurant Syndrome”  Glutamic acid produced through fermentation of beet sugar or corn syrup.  Effects seen were fainting, rapid heartbeat, nausea and muscular twinges. Lesions in brains of mice when given msg in an amount equivalent to that found in a can of soup. But then human studies showed nothing when fed large amounts of msg.  Well controlled, double blind studies concluded that msg presents no problems at the levels normally used, but a large dose may cause burning sensation, facial pressure, headache, drowsiness and weakness in a very small percentage of people. But there was a threshold effect – symptoms were only noted in those who ingested over 2.5g of msg at one sitting.  Researchers prefer “msg symptom complex” instead of “Chinese restaurant syndrome”.  Side effects are hardly reported in Asian populations, where msg is consumed far more than in North America.  Parmesan cheese and tomatoes are rich sources of naturally occurring glutamate but nobody has suffered for „Italian restaurant syndrome‟. Glutamate also in mother‟s milk. Preserving with Radiation (222-225)  Electronic pasteurization – subjected to irradiation with a beam of microbe-destroying electrons.  The type of radiation and extent of exposure determines risk.  Visible light does not have enough energy to break chemical bonds, but x-rays can. Thus if we do this to microbes, we can kill them before eating our food.  Eating irradiated food does not expose consumers to radiation.  2-ACBs have been found in irradiated foods, which are capable of inducing mutations in cells, and when fed to rats they promoted tumour formation in animals that had been treated with a carcinogen. But the concentrations used in this study were 1000x that found in irradiated foods.  Benzene can result from radiation exposure but the amounts are inconsequential. Manipulating Genes in our Food (259-263)  Benefits outweigh the risks in genetically modified foods.  If something is good for a biotech company, it isn‟t necessarily bad for the public. No company wants to undermine its existence or profits by marketing dangerous substances.  Natural cross breeding leads to natural toxins which may have just as much of an effect on our body as genetically modified crops. World of Chem: Food Final Readings  The most common malnutrition is iron deficiency, which can cause intellectual impairment, suppressed immunity and complications in pregnancy. Millions of people suffer from iron deficiency anemia. Rice does not contain much iron, and the iron it does contain is un-absorbable because of phytates, which bind iron in the digestive tract and prevent it from being transported across the intestinal wall into the bloodstream.  Genetic modification has resulted in rice that has more iron. French beans (aka haricot beans, kidney beans, flageolets) had a gene that codes for the synthesis of a protein called ferritin, an iron-storage protein. This gene was inserted into rice. Another gene from a fungus that codes for an enzyme that breaks down phytates was also put into the rice.  Rice is also very low in vitamin A, so vitamin A deficiency is also a problem. It causes blindness, cancer and skin problems. Thus genes from daffodils and a bacterium that code for proteins that enhance beta-crotene synthesis were put in rice, which look yellow. Acrylamide in Fried and Baked Foods (276-279)  Polyacrylamide is used in water treatment to coagulate and trap suspended impurities, so acrylamide can show up in water.  When fed huge doses to test animals, acrylamide can cause tumours and neurological problems.  WHO – 0.5 ppb maximum of acrylamide in drinking water.  Acrylamide toxicity can cause numbness 
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