Hydrogenation
A marketing/ food processing practice that helps with shelf life of foods
What are the purposes of hydrogenation and the end result?
Purposes:
1. Transform oil as a liquid to hardened fat (used for baking and for it to be more easily spreadable)
2. Enhance the shelf life
End product: Hydrogenated (stick margarine) or partially hydrogenated vegetable “oil” (tub margarine)
What are Trans Fatty Acids (TFA’s)?
A category of fatty acid found during hydrogenation
- most naturally-occurring fatty acid have “cis” double bonds (not linear)
- hydrogenation produces “trans” double bonds
Food sources of TFA’s:
Minority: Dairy products: Conjugated linoleic acid
Majority: Processed foods containing…
1. vegetable ‘oil’ shortening
2. hydrogenated/partially hydrogenated vegetable oil
3. margarine
Digestion:
Enzymatic breakdown of food constituents to smallest absorbable unit (e.g. glucose, f.a, amino acids)
Absorption:
Transfer of digested food components across absorptive surface of the gastro-intestinal tract and into vascular or lymphatic system
Metabolism:
Various pathways nutrients will take following digestion/absorption (leads to storage, precursers, and others)
How is fat digested and absorbed?
- TG’s from food enter small intestine
- bile acids (x) enter small intestine and disperse fat into smaller droplets (emulsification)
- lipases break down the fat called lipase
- micelles form (bubble)
- fatty acids and monoglycerids are then absorbed into intestinal cell
a) if f.a is 12 cells or less, it will be absorbed into the portal vein (along with water soluble nutrients like glucose)
b) if f.a is 14 cells or bigger, it will be repackaged into chylomicron (the chylo. will then enter lymphatic system through the thoracic duct - Bile acid (x) is then reabsorbed and recycled
Quick summary of Bile Acids:
- Made from cholesterol
- Required for:
a) Emulsification of fat
b) formation of micelles - normally have excess amount because bile acids are recycled 3-4 times/meal
2 important aspects of fatty acids
- chain length (e.g. 2-4 carbons: short chain fatty acids- fibre
e.g. 2-4 carbons: short chain fatty acids- fibre
6-10 carbons: medium chain fatty acids
12+: long chain fatty acids - degree of saturation: how many double bonds in a chain
Fatty Acid Types:
TYPE OF F.A: Omega-6: double bond is the 6th carbon (e.g. linoleic acid 18:2n-6)
Omega-3: double bond is the 3rd cardon (e.g. linolenic acid 18:3n-3)
20:5n-3: EPA- Eirosapentaenoic acid <3 (e.g. salmon, trout, herring, sardines)
22:6n-3: DHA- Dorosahexanenoic acid, helps/benefits retina (eyes), brain, heart (e.g. lakeside and wild game)
Essential Fatty Acid Deficiency: symptoms
- scaly dermatitis: cheeks/’rug burn”appearence
- impaired growth
- excess loss of water through skin
very rare
Role of fat in the diet:
- Source of Kcal (9kcal/g)
- Provides essential f.a (linoleic and alpha linoenic)
- Carries fat-soluble (ADEK) vitamins)
- Palatebility/mouth feel
Role of fat in the body:
- Insulation- keep warm
- Protection- skeleton and vital organs
- energy reserve-
- stores kcal in adypose (fat) cells
- reduce levels only by oxidizing fat
- used as an energy (kcal) fat reserve only if kcal<kcal expenditive - Precurser for other biomolecules
- such as eicosanoids (biological messengers) and phospholipids from f.a
- such as bile acids and steriod hoormones from cholesterol
Purpose of lipoproteins (LP)
transport fat around blood and lymphatic system
Roles of Chylomicron:
- carry fat from GI tract-> lymph-> bloodstrem
- deliver fat to adispose tissue (stored)
- present in blood 2-10 hrs after eating (when getting blood tests for total cholesterol, one must be fasted to get accurate results)
Roles of VLDL:
- made in liver to carry fat (TG) formed by liver from excess dietary carbs and proteins
- deliver to adispose tissue and becomes LDL
Roles of LDL (“bad Cholesterol”)
- Circulate in blood and deliver cholesterol to all body tissues
*- if not taken up by the liver, it remains in the blood (when liver is overloaded with cholesterol it “shuts down” receptors/doorways - remains in blood= raised LDL’s + free radicals (creates oxidization)–> oxidized LDL (looks foriegn to immune system)
What is ‘total blood cholesterol’?
TC= LDL + HDL + VLDL
