福州大学：《食品化学》课程教学资源（试卷习题）Midterm Examination 4（UC Davis）试题

Food Science Technology 100A Professor S.R.Dungan Second Midterm Examination November 22,2004 This is the beginning of the SHORT ANSWER section of the examination. (7 pts.)The first question pertains to the molecule below: 入入入 -0 -8人 B (2 pt.)Choose one fatty acid,describe its position using stereospecific numbering(sn)and give both its common and systematic name Position Common Name 0 Stearic Acid (5 pts.)Show a likely free radical structure that results when a hydrogen is lost from fatty 07 0 0 0

Food Science & Technology 100A Professor S.R. Dungan Second Midterm Examination November 22, 2004 This is the beginning of the SHORT ANSWER section of the examination. (7 pts.) The first question pertains to the molecule below: (2 pt.) Choose one fatty acid, describe its position using stereospecific numbering (sn) and give both its common and systematic name Position Common Name Systematic Name sn-1 Lauric Acid Dodecanoic Acid sn-2 Oleic Acid 9-Octadecenoic Acid sn-3 Stearic Acid Octadecanoic Acid (5 pts.) Show a likely free radical structure that results when a hydrogen is lost from fatty acid B. Any resonance structures that are formed should be shown completely. B C O C O O O O O C O O O O C O O O O C O O O C O O O O O C O O O O C 2 4 6 8 11 13 15 17 2 4 6 8 11 13 15 17 2 4 6 8 11 13 15 17 2 46 8 11 13 15 17 2 46 8 11 13 15 17

FST 100A Midterm 2;November 22,2004 Page2 (3 pts.)Explain what reactions occur and products are formed during frying of lipids. 点 s that convey a bad sme to the oil. active molecules that cause foaming

FST 100A Midterm 2; November 22, 2004 Page 2 (3 pts.) Explain what reactions occur and products are formed during frying of lipids. The two key reactions during frying are lipid oxidation and hydrolysis. Lipid oxidation produces aldehydes that convey a bad smell to the oil. Hydrolysis cleaves off free fatty acids from the triglycerides. These can produce flavors (smells), but more importantly are surface￾active molecules that cause foaming