Starch Gelatinisation

ADLS1  COURSE 225[pic 1][pic 2]

FOOD & NUTRITION BASICS

LABORATORY REPORT[pic 3]

LAB 2   STARCH

DUE DATE Next FNB Practical

NAME (CAPITALS) ______________________________GROUP LETTER___________

This work is the product of my own efforts and has not been copied from any other sources except where full acknowledgement has been given.

SIGNED________________________________________ Student No._____________

Aim : starch is the main source of carbohydrates in a diet of human being body. It is believed that the textural properties of starch are very important in our diets.

1. Starch gelatinisation l

Background:

Breaking down the intermolecular bonds of starch molecules when water and heat is present, allows the H-bonds sites to have more water, it oppositely dissolves the starch granules in the water, and water looks like plasticizer, this is the process of starch gelatinization.

Materials:

            1.Chopsticks

            2.Boiling tubes

            3.Glass beaker

            4.Water baths

Procedures:

1. Prepare 100 ml of a 15% w/v starch suspension in a glass beaker

2. agitate and pour equally into 3 boiling tubes

3. label 3 different temperature on the tubes (60C , 75C, 90C)

4. 3 boiling tubes were put into 3 hot water baths

            5. leave the tubes in the bath for 60 minutes and observe any changes

Results:

Tube 1 (60C): sediments were left under the tube liquid; it was little bit of thick comparing to the room temperature one. Texture and visual appearance was more like liquid and smooth. Least viscous among the 3

Tube 2 (75C): it was smooth, more viscous than 60. more like jelly type in appearance and texture, sticks to the chopstick, less viscous than 90

Tube 3 (90C): the product sticks to the chopstick, gelatinous at the bottom is very thick, there were bubbles in it. Viscosity is high, most viscous among the three

Discussion:

For 60C, there were sediments in the bottom of the boiling tube, which were not been gelatinized. It was milky colour, saturated mixture of hot water and starch. it is believed that from the results, 60 degrees is not enough for starch gelatinization

For 75C, the gelatinous was smooth, it goes through gelatinization, could see transparent liquid on the top part of the tube, which meant that it’s not been gelatinized.

For 90C, the gelatinous was thick, bottom part was the thickest. Comparing with 75C the colour of this was more transparent. There were bubbles within the gelatinous because of high temperature. It went under a complete gelatinization.

During heating, water is absorbed in the spaces of starch, which leads to the swelling phenomenon, water then reaches into the double helical parts of amylopectin. Penetration of water increases the randomness in the starch granule overall structure which causes swelling. some type of unmodified native starches start swelling at 55C, other types at 85C. Swelling becomes faster by cross linking of amylopectin, and acetylation, genetic manipulation of starch genes, amount of damaged starch granules.