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NUSC 3233 - Exam 3 Questions And Answers @ 2024
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NUSC 3233 - Exam 3 Questions AndAnswers @ 2024
Lipids - Answer -Non-polar, water insoluble compounds
- Carbon, hydrogen and small amounts of
oxygen
- 3 classes: Triglycerides, Phospholipids, Cholesterol
Triglycerides - Answer glycerol + 3 fatty acids
Structure of fats - Answer - Always have triglycerides
- Others not as common in foods, but may be generated during cooking and digestion
Types of fatty acids - Answer - Saturated: straight; packed/organized
- Unsaturated: bent; can have multiple C=C double bonds/curves
- Monounsaturated: 1 C=C
- Polyunsaturated: multiple C=C
Hydrogen orientation - Answer - Cis: H on same side of C=C; bent
- Trans: H on opposite side of C=C; linear (trans fats, stable at high temps)
18 carbon fatty acids - Answer stearic, oleic, linoleic, elaidic, polyunsaturated
Stearic Acid (saturated) - Answer chocolate production
oleic acid (omega 9) - Answer cis-monounsaturated
- avocado oil, olive oil
elaidic acid (trans omega 9) - Answer trans-monounsaturated
- margarine
linoleic acid (omega 6) - Answer 2 C=C polyunsaturated
- mixed nuts/seeds
Omega 3 - Answer 3 C=C polyunsaturated
- fish, seafood
,How to differentiate between omega 3, 6, 9? - Answer Location of the first C=C double
bond
3D structure of 18-carbon fatty acids - Answer - Stearic acid (C18:0)
- Elaidic acid (C18: 1n-9t)
- Oleic acid (C18: 1n-9)
- Linoleic acid (C18: 2n-6)
- y-linoleic acid (C18: 3n-6)
Triglyceride formation - Answer Esterification between glycerol and fatty acids
Triglycerides in food - Answer Fatty acids determine physical characteristics of fats:
- Chain length
- Degree of unsaturation
- Common Foods: French fries, fried chicken, bacon, cheeseburgers, etc.
Typically solid fats at room temp? - Answer coconut oil, butter, palm, and lard (cooking
veggies)
Physical characteristics of fats - Answer - Flow
- Deformation
- Crystallization: at low temps
- Melting point: The temperature at which the crystals of a solid fat melt
Crystallinity of solid fats - Answer - Formation of a highly organized solid structure (Van
der Waals forces)
- Solid fats are composed of many tiny crystals
- Turning fork form: Well suited to form crystal matrix
Forms of fat crystals - Answer - Alpha: small crystals, very unstable
- Beta prime: tiny crystals, smooth, moderate stability
- Intermediate: small crystals, slightly coarse (melted and re-crystalized)
- Beta: large, most stable, but fine-coarse texture and undesirable
Chocolate bloom - Answer Whitish coating that appears on the
surface of chocolate
, - Major concern in the production of chocolate
- Causes: Poor (incorrect or incomplete) tempering, Incorrect fat mixture during
production, Warm storage conditions, Incompatible between fat and cocoa butter,
Abrasion and finger marking
formation of fat crystals in foods - Answer - Chocolate tempering
- Polymorph & polymorphism
- Refrigerated chocolate tastes better - why?
Ideal chocolate crystal? - Answer Crystal #5 (beta-prime)
- 34 deg. C
- glossy, firm, best snap, melts near body temp
- If you go over the temp, you have to start over from scratch!
Hydrogenation - Answer Addition of hydrogen to an unsaturated
fatty acid
- Catalyst raises the melting point
- Liquid --> solid
- Ex: soybean oil becomes solid
Effects of Hydrogenation - Answer - Partial hydrogenation: formation of trans (most
common)
- Benefits: texture, taste, improves shelf-life, stable during deep-frying, inexpensive
- Cons: very unhealthy; partially hydrogenated vegetable oils = trans fatty acids!
Hydrogenated oil vs. trans fat - Answer partially hydrogenated oils are trans fats (even if
label says 0 g trans fat!)
- Partially hydrogenated palm
- Partially hydrogenated vegetable oil
- Trans fats generated during baking process
Interesterification - Answer Treatment with enzymes or sodium methoxide (catalyst)
- Splits fatty acids from glycerol
- Reorganizes into different triglycerides
Types of Interesterification - Answer (1) Randomized: melted fat+catalyst; all fatty acids
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