Stephany Ayoubi and Charlotte Holdorf

Lab Group #3 ​ Title: Carbohydrates II: Gelatinization

Purpose: Effect of temperature and of added ingredients on gelatinization of various starches. ​ Introduction:

Starch is a complex carb made up of amylopectin and amylose. It is a major carbohydrate that can be found in either plant tuber or even seed endosperm, known as “starch granules”. The common sources of this carbohydrate that will be tested in this experiment are corn starch, potato starch, rice starch, tapioca, wheat, all purpose flour and arrowroot. It is important to find out what temperature gelatinization occurs for each type of starch. These starches have various chemical structures. For instance, amylose makes of 0­28% of starch and contributes to gel formation. However, amylopectin, makes up 80­100% of starch and contributes to the viscosity of pastes. The functions of these starches are significant in the industrial world. The range of functions include; thickening, non­enzymatic browning, moisture retention, drying agent, foam strengthener and emulsifier. It is important to compare expectations and scientific standards for these starches to the results obtained in the lab. This lab will also be testing the effects of sugar, acid, modified starches and lipids. Viscosity will be observed through initial and and cooled line spread test, which will test the thickening power of the starch. The gel strength will be tested by a percent sag calculation. Other observations will include general appearance and consistency as well as magnified structure under a microscope.

Materials and Methods:

1. Lugol reagent

2. large beaker

3. water

4. coverslip

5. microscope

6. measuring tablespoon

7. Line spread plate

8. Thermometer

9. Custard cup

10. Shallow pan

11. Ice

12. 64g Waxy Maize Starch

13. Small Saucepan

14. 50 g sugar

15. 65 ml lemon juice

16. 26.5 g butter

17. 265 ml 0.25% alpha­amylase solution

18. 18g Rice Starch

19. 18g Corn Starch

20. 18g Waxy Maize Starch

21. 18g Tapioca Starch 22. 18g Potato Starch

23. 18g Wheat Starch

24. 18g AP Flour

25. 18g Arrowroot

Procedure for microscopy:

i. Examine slides of a few granules of the uncooked starch dissolved in water and a thin

smear of a drop of the heated starches with various treatments. under the microscope

j. While the starch solutions are on the slide , stain with Lugol reagent (2% KI, Sigma),

cover with coverslip and re­observe.

k. Note the color and draw the shape and size of the starch granules

Procedure 1:

1. In a large beaker, combine 18g of each type of starch with 265­ml cold water.

2. Suspend a thermometer in a pan (using a ring stand). Make sure the tip is completely

under the liquid but does not directly come in contact with the beaker.

3. Cook the mixture using a medium­low heat, continuously stir until a boiling temperature

is reached. Mark this temperature once reached.

4. The mixture should now be a hot paste that you can perform a line spread with. The line

spread should be done using 2 tablespoons for 30 seconds.

5. The remaining sol should be cooled to 24 degrees celsius. Place the sol in a small custard

cup and cover with saran wrap. Put this custard cup in a shallow pan of ice water.

6. If the sol gels, perform a percent sage test. If the sol remains a paste, perform another line

spread test. Procedure 2:

1. Stir in 64g of waxy maize starch in 944ml of cold tap water in a small saucepan.

2. Suspend a thermometer in a saucepan (using a ring stand). Make sure the tip is

completely under the liquid but does not directly come in contact with the saucepan.

3. While heating, stir (using stirring utensil, not thermometer)

4. At intervals of 60,70,80,90 and 95 degrees celcius remove 2 tbsp of the sol and perform a

line spread test using 2 tablespoons for 30 seconds.

5. Determine the the viscosity peak by graphing your results and comparing to the book’s

graph.

6. Repeat steps one through three.

7. Maintain for 20 minutes at the peak viscosity temperature that was determined from the

graph. Stir continuously.

8. Cool the paste obtained in ice water and at intervals of 10 degrees celsius until 50 degrees

celsius is reached.

9. If the paste transforms to a gel, perform a % sag test. if the product is still a paste perform

another line­spread. Observe the samples and fill out the table A.

Procedure 3:

A) 18 g of cornstarch and 50 g sugar in 265­ml of water

B) B) 18 g cornstarch in 200 ml of water + 65 ml lemon juice

C) 18 g of cornstarch in 265 ml of 0.25% alpha­amylose solution

D) C) 18g of cornstarch and 26.5 g fat (butter) in 265­ml water

1. Suspend a thermometer in a pan (using a ring stand). Make sure the tip is completely

under the liquid but does not directly come in contact with the pan.

2. While heating, stir (using stirring utensil, not thermometer)

3. Cook the mixture using a medium­low heat, continuously stir until 95 degrees celsius is

reached. This will be the end point temperature, take note of temperature if end

temperature is not 95 degrees celsius.

4. Perform a 2 tablespoon, 30 second line spread test with the hot paste.

5. The remaining sol should be placed in a small custard cup, covered with saran wrap and

cooled to 24 degrees celsius using a shallow pan of ice water to place the custard cup in.

6. If the product gels after 24 degrees celsius is reached perform a percent sag test, if the

product remains a paste, perform another line spread test.

7. Record results in Table B.

Observations:

Table A: Type of Linespread or % sag tests Starch

Steps 1­4 60 degrees 70 degrees 80 degrees 90 degrees 95 degrees celsius celsius celsius celsius celsius

Corn starch 21.3 11.3 9.5 3.8 2.5

Potato Starch 12 4.5 3 4 3

Steps 6­9 Peak ­10 degrees ­20 degrees ­30 degrees ­40 degrees Viscosity celsius celsius celsius celsius

Corn Starch 13 13 15 14 13

Potato Starch 3.85 4 3.5 ­ 4

Table B: Procedure 1: Sample End Line Line % sag transpare consisten General Temperat Spread Spread ncy cy appearan ure (Hot) (cold) ce

Rice 75 4 3.75 n/a slightly thick, white degrees cloudy soft gel cloudy celsius gel

Corn 90 3.55 3 71 transluce jello­like off­white nt gel

Waxy 76 7 4 40 slightly thick gel white gel transpare nt

Tapioca 104 15 22.3 n/a minimal watery no cloudy gelatiniz ation, pinkish color Potato 70 3.5 2.5 n/a cloudy thick gel thick & pasty

Wheat 92 3 4 n/a not thick, cloudy transpare gluey nt

AP Flour 103 6.75 7 n/a not thick, foggy, transpare viscous cream nt colored gel

Arrowro 79 3 5.3 n/a very thick, gel like, ot clear sticky clear

Procedure 3: Table B

Sample End of Line Line % sag transpare consisten General temperat Spread spread ncy cy appearan ure (hot) (cold) ce

Corn + 95 0.5 1.5 60% transpare paste­lik clear gel Sugar degrees nt egel celsius

Corn + 95 4 8.25 n/a not firm, but light Lemon degrees transpare not a gel yellow, celsius nt firm

Corn & 96 1.5 ­ 35.7 none gel gel, alpha­am degrees creamy ylase celsius white

Corn + 95 10 7 n/a opaque yogurt jello­like fat degrees celsius

Results:

For procedure one, results were as expected. The corn starch formed a thick gel, As time increased, the viscosity of the paste increased. And when temperature decreased and the product was cooled viscosity also increased. Referencing to results obtained in Table B, one can see that the first line spread test result was observed to be 4 and the second at 3.75. That is a decrease by

0.25 which suggests an increase in viscosity. The first line spread was taken at the end temperature of 75 degrees celsius.

For procedure two, results were again exactly as expected. As the time increased, the viscosity of the corn starch increased. Subsequently forming a gel.

For procedure three, an interfering agent was added to the mix. Testing the effect of sugar on starch gelatinization provided results that were unexpected. As learned in class, sugar has a negative effective on the strength of gel and viscosity strength. That was not seen in the results of the linespread test. A higher viscosity was actually seen due to lower line spread results seen in procedure 3 versus procedure 1, which presents the fact that the paste was more viscous when sugar was added. Also, results were unexpected for the percent sag test. Percent sag, decreased from 70% found in procedure one to 60% in procedure 3, which means the gel strength increased. The only part that was expected was the end temperature. The end temperature seemed to be 5 degrees celsius higher for the corn plus sugar. This makes sense because sugar increase gelatinization point temperature.

Discussion;

In procedure two, expected results occurred. It was expected that the potato starch would have a higher viscosity and lower linespread test result. This was seen in the results obtained from the experiment. Potato Starch in the increasing temperature zone, had a higher viscosity than corn starch. However, as time increased, results should have been different. The procedure should have ended with a more viscous corn starch compared to the potato starch, when comparing to the graph. On the other hand, Corn starch seemed to be less viscous than potato starch in the end. at ­40 degrees celsius.

In procedure 1, all groups were assigned a different type of starch; rice, corn, waxy maize, tapioca, potato, wheat, ap flour and arrowroot. At low temperatures, viscosities like wheat, tapioca and corn starch should have been lower than potato, however this was not the case in the experiment. The results that were obtained were mainly due to the structure of each starch.

The more gel like results were due to the higher amylose content. Amylose is a linear structure and easily forms gel. Amylose was most present in corn starch and wheat starch. On the other hand, tapioca, waxy maize and potato starch had a higher amylopectin content which produce soft gels or thick pastes. The potato starch has large granules and ong amylose molecules that thicken early on but with time the viscosity decreases. Waxy corn maize has little or no amylose starch, so that explains the unstable paste result and the 40 percent sag. Tapioca starch has weak intermolecular content and the swollen granules district easily, which is why the texture seemed watery.

In procedure 3, the interfering agents produced an expected result. The added fat increased the viscosity just as expected. This is because the starch binds with the fat and thickens the mixture. The modified starch, amylose that was added had a beginning line spread of 1.5 which is a high viscosity. This is expected because modified starches increase gel formation and stabilize its sensitivity to heat while decreasing chance of syneresis. The second line spread was not recorded so a comparison cannot be made. Overall, sugar had the lowest line spread number which was surprising because sugar competes with starch. When acid was combined with the cornstarch a great difference was seen. The line spread increased from 4 to 8.25, increasing more than 50 percent. This is due to the general effects of acid on starch; decreasing thickness of product, breaking swollen granules and decreased viscosity. It was interesting to see the wheat starch outcome, due to the high protein content of the starch, a “gluey” consistency was the outcome and a thick gel due to the amylose content.

Viewing the structures under the microscope, provided an opportunity to confirm the starch content of each carbohydrate. If stained blue, such as corn starch and potato starch, it was confirmed that the main percent starch was amylose. If stained red after adding iodine, as seen in waxy maize corn, the content was confirmed majority to be consisted of amylopectin. It was also positive to see that the amylose structured starches consisted of larger granules, more swelling when compared to the red stained slides consisting of amylopectin.

A lot of the results were not as expected, there could've been a # of reasons that this could have happened. Materials are very important when it comes to scientific experiments. Cross contamination of starches or interfering agents could definitely skew the results and impact final observations. Another possible source of error could have been measurements of starch and liquid and time management. Taking linespread at the correct temperature is very important to results and confirming what is expected. References:

Cifuentes, Mariana, Papaspyrou, Salome, Sivaprasad, Usha 2014 Experimental Foods 709:489 ​ Laboratory Manual

Simpers, Rachel. "Starches." Rutgers University. Fall 2014. Lecture.