carbohydrates lecture 4

Question 1

Three different types of corn

Answer 1

regular corn: consists of about 20% amylose
waxy corn: consists of about 0-7% amylose
High amylose: consists of 70% amylose and is used in foods that need to crystallize very quickly such as batters etc.

Question 2

gelatinization of regular corn vs. waxy corn

Answer 2

regular corn gelatinizes into a thick opaque gel which spoils and becomes hard gel in a day whereas waxy corn is clear and liquid like but remains stable and only becomes a little bit thicker the next day.

Question 3

enzyme modification by alpha amylase

Answer 3

alpha amylases cut off the alpha 1,4 ends of starch producing fragments that are small or very small depending upon the amount of time it was subjected to the enzymatic treatment.

Question 4

enzyme modification by beta amylase

Answer 4

Beta amylase breaks of the nonreducing ends of a starch molecule(branched parts?) and the left over molecule is B limit dextrin which has limted applications (like what?)

Question 5

chemical modification

Answer 5

1. dextrinization-after being subjected to high temperature and processing conditions the starch is broken up and reforms through crosslinking create a polymer that is resistant to break down by enzymes and acts as a fiber
2. lipophilic subsitution- starch reacts with a lipophilic group to produce an amphipahtic surfactant
3. stabalization-add side groups to the sugars on starch to prevent them from creating glycosidic bonds, crosslink and crystallize
4. crosslinking-polymers are crosslinked to produce a stronger structure resistant to enzyme degradation
5. enzyme hydrolysis- break down of specific fragments by enzyme»a,1,6 bonds and make the structure act more like amylose
6. oxidation-hydrolyze starch molecules and help create better film coatings with starch (make it less thick? why is a carbonyl group added)
7. acid hydrolysis-random break down of starch to lower molecular weight

Question 6

Stabalization vs. crosslinking

Answer 6

These are most often combined together:

Crosslinking: this occurs when you want to add links in addition to just H bonds which produce permenant crosslinks that are difficult to break. You can do this by reacting starch with pocl3 and AA.
-best done with foods subjected to high processing conditions

Stabalization is best done through by reacting propylene with S3MP
-best done with foods undergoing refrigeration, heating and cooling, freeze thawing»danger of crystallizing too much.