lecture 20-starch
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Briefly describe starch digestion
Occurs in about 120 minutes. goes from starch to maltose and smaller dextrins through amylase and then other enzymes break it into glucose for it to be absorbed
What is glycemic response?
Effect of starch containing food on our blood sugar levels (blood chemistry)
Define glycemic index.
-value used to measure how slowly/rapidly the consumption of a given food increases blood glucose level
How to measure glycemic index and typical values.
Gi= glucose response to test food/glucose response to reference food x100 Test food measured over time after having 50 g of food Reference as well should be digestible carb or glucose like white bread Typical values: Low: 0-55 Mid: 56-69 High: more than or equal to 70
Define glycemic load and give typical values.
-used to quantify the overall glycemic effect of a standard portion or serving food GL=glycemic index x amount of available CHO/ 100 Typical values: Low=0-10 Mid=11-19 High=equal or more than 20
What are the factors affecting gi of foods and briefly describe
Amylose: amylopectin ratio -high amylose content decreases gi because absorbs less water making tighter strcutures that make it harder for enzymes to access so slower digestion Presence of other food components that interact with starch like lipids Physical barrier or trapping of starch -example bran acts as a physical barrier making it harded for enzymes to acess endosperm Type of starch present -order of digestion and glycemic response (RDS, SDS, RS) Processing -homoginzed, increases surface area of food and exposes interior starch to digestive enzymes -intact food that is dense and non porous have limited interactions with enzymes so make it harder for enzymes to interact
What is total starch and define the components?
Total starch=RDS+SDS+ RS SDS: slowly digestiable starch is the natural form of starch in uncooked foods, protected from enzymes and can be transformed into RDS RDS: rapid digestiable starch, amporphous in strcurure and enhances the ability for enzymes to acess it RS: escapes digestion and enters colon, no calories or fewer
What are the types of resitant starch?
RS1: physically inaccesible like grain legumes like beans RS2: resistant starch granules like unripe banana RS3: retorgraded starch, cooking to cooling like potatoes, stale bread RS4: chemically modified starch, cross bonded
Over 120 minutes what is fast, slow and no glycemic response?
Rapid: 0-20 minutes after consumption (4cal/g) Slow: 20-120 minutes after consumption (4 cal/g) No digestion- 0 calories after consumption