FST606 exp 9 - lab report PDF

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INTRODUCTIONViscosity is the measure of the internal friction of fluid. These internal friction is caused when a layer of fluid moves in relation to another layer. The greater the friction, the greater the amount of force required to cause this movement. This movement is known as shear (Sahi S., 201...

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INTRODUCTION Viscosity is the measure of the internal friction of fluid. These internal friction is caused when a layer of fluid moves in relation to another layer. The greater the friction, the greater the amount of force required to cause this movement. This movement is known as shear (Sahi S., 2014). Viscosity describes a fluid’s internal resistance to flow and may be thought as a measure of fluid friction. All real fluids (except superfluids) have some resistance to stress, but a fluid which has no resistance to shear stress is known as an ideal fluid or inviscid fluid. This result is typically expressed in centipoise (Cp) (Abbas K. A. et. Al., 2010). There are numerous instruments available to the food industry to measure viscosity for quality control and thus ensure that products make are of consistent quality. The various types of viscometers can be classified according to the principle on which they work. The most commonly used viscosity measurement devices are capillary flow viscometers, orifice type viscometers, falling ball viscometers and rotational viscometers (Abbas K. A. et. Al., 2010). Brookfield dial reading viscometers are widely used in the food field. They have the advantages that they are of moderate cost, portable, simple to operate, well adapted to many viscosity problems, give results quickly, can be used on Newtonian and non-Newtonian liquids, can be used to measure time dependency and hysteresis, are not affected by large particles in suspension, and require minimum maintenance (Abbas K. A. et. Al., 2010). Capillary viscometer measured viscosity by timing how long it takes for the fluid foods to flow between two points of a capillary tube. Meanwhile, rotational viscometer used a torsion spring to measure the torque required to rotate a spindel in the material. By changing rotor speed and size of spindle allows for the measurement of dirrent ranges of viscosity. The viscosity of a sample can be calculated using the formula below: (Godfrey B.M., 2011). Viscosity (centipoise) = Dial reading x factor

OBJECTIVE 1. To determine the effect of different speed selection on sample measurement. 2. To determine the effect of different Spindle Number (#) on sample measurement.

APPARATUS AND REAGENTS Brookfield Vicometer Beakers Sample: Sauce of different brands

METHOD 1. Effect of different speed selections on sample measurement (a) Approximately 500mL sample was poured into a 1L beaker. (b) The viscometer Model and fix spindle# used for the sample was recorded. (c) The dial reading was took and the viscosity of the samples was calculated using the formula below. (d) The step above was repeated by using by changing the speed to a different rpm and the viscosity of the sample was measured. (e) Step 1 – 4 was repeated for other samples. Viscosity (centipoise) = Dial reading x factor ............... (1)

2. Effect of different Spindle Number (#) on sample measurement (a) Approximately 500mL sample was poured into a 1L beaker. (b) The viscometer Model used was recorded and a suitable speed was selected based on observation from procedure (a). (c) The dial reading was recorded and the viscosity of the samples was calculated. (d) A different spindel was changed and the viscosity was measured. (e) Step 1 – 4 was repeated for other samples.

RESULT A. Effect of Different Speed (rpm) on Viscosity Measurement Viscometer Model: LV Spindle#: 1 Table 1.0: Effect of Different Speed (rpm) on Viscosity Measurement Speed (rpm)

Sample

Viscosity

Starjuice Viscosity

6 (x10) 325.0 330.0 327.5 ± 3.5

12 (x5) 242.5 237.5 240.0 ± 3.5

30 (x2) 154.0 153.0 153.5 ± 0.7

60 (x1) 100.0 100.0 100.0 ± 0.0

Viscosity (Cp) 1 2 Average ± Std Dev

327.5 x 10 = 3275 710.0 720.0 715.0 ± 7.1

240.0 x 5 = 1200 452.5 455.0 453.8 ± 1.8

153.5 x 2 = 307 200.0 200.0 200.0 ± 0.0

100.0 x 1 = 100 100.0 100.0 100.0 ± 0.0

Viscosity (Cp)

715.0 x 10 = 7150

453.8 x 5 = 2269

200.0 x 2 = 400

100.0 x 1 = 100

Graph 1.0: Effect of Different Speed (rpm) on Viscosity Measurement

Spe e d vs v is c os i t y of s auce 8000 7000 viscosity (cp)

Red Horse

1 2 Average ± Std Dev

6000 5000 Red Horse Starjuice

4000 3000 2000 1000 0

6

12 Speed (rpm)

30

60

B. Effect of Different Spindle# on Viscosity Measurement Viscometer Model: LV Speed (rpm): 6 Table 2.0: Effect of Different Spindle# on Viscosity Measurement Spindle# Sample 1 2 Average ± Std Dev

1 (x10) 325.0 330.0 327.5 ± 3.5

2 (x50) 325.0 325.0 325.0 ± 0.0

3 (x200) 200.0 400.0 300.0 ± 141.4

4 (x1000) 200.0 200.0 200.0 ± 0.0

e

Viscosity (Cp) 1 2 Average ± Std Dev

327.5 x 10 = 3275 710.0 720.0 715.0 ± 7.1

325.0 x 50 = 16250 775.0 750.0 762.5 ± 17.7

300.0 x 200 = 60000 900.0 800.0 850.0 ± 70.7

200.0 x 1000 = 200000 1000.0 900.0 950.0 ± 70.7

Viscosity

Viscosity (Cp)

715.0 x 10 = 7150

762.5 x 50 = 38125

850.0 x 200 = 170000

950.0 x 1000 = 950000

Horse Viscosity Starjuic

Graph 2.0: Effect of Different Spindle# on Viscosity Measurement

spindle# vs viscosity of sauce

VISCOSITY (Cp)

Red

1000000 900000 800000 700000 600000 500000 400000 300000 200000 100000 0 1

Red Horse Starjuice

2 Spindle# number

3

4

DISCUSSION In this experiment, the Brookfield viscometer was used to measure the viscosity of different brands sauce which are Red Horse and Starjuice sauce. Viscosity measurements are made in conjunction with product quality and efficiency. In food technology, viscosity measurements is very important in order for quality control, where raw materials must be consistent from batch to batch. For this purpose, flow behaviour is an indirect measure of product consitency and quality. There are several models of viscometer available from Brookfield but the majority operated in the same measure by the viscometer motor rotates the spindle at a define speed which is measured in rpm and the viscometer measures the resistance to rotation and reports a viscosity value (Abbas K. A. et. Al., 2010). A Brookfield viscometer model LV was used in this experiment to measure apparent viscosity. The viscometer operates by rotating a cylinder or disc in the fluid and measuring the torque necessary to overcome the viscous resistance to the induced movement. This is accomplished by driving the immersed element, which is called a spindle, through a beryllium copper spring (Corvallis Environmental Research Laboratory, 2007). Based on this experiment conducted on Brookfield viscometer with different speed in rpm and different spindle#. The result in table 1.0, shows the effect of different speed (rpm) on viscosity of two brand sauces. Once a valid reading is obtained with a dial reading, the average of dial reading is multiply by the factor for the speed used by using formula viscosity (centipoise) = dial reading x factor. These viscometers viscosity is in units of Cp. For spindle# 1 of Red Horse sauce, the viscosity in centipoise obtained are 3275, 1200, 307 and 100 of 6, 12, 30, and 60 speed in rpm respectively. For Starjuice sauce the viscosity in centipoise obtained are 7150, 2269, 400 and 100 of 6, 12, 30, and 60 speed in rpm respectively. To explain the result efficiently, the graph was plotted to discuss about the relationship of viscosity and speed in rpm of two brand of sauces. Determination of viscosity of sauce is based on the effect of speed and spindle number towards the viscosity of the sample. From the Graph 1.0, it shows that when the speed of viscometer is increase, the viscosity of sauce for both sample is decrease. This is because of the greater friction force is obtained when the speed is increasing. So, the spindle become easy to rotate through the sauce (Sahi S., 2014). Besides, a large viscosity means that a

liquid will flow very slowly whereas a small viscosity means that the liquid will flow quickly. The higher the viscosity of a liquid, the thicker it is and the greater the resistance to flow. Next, the result in table 1.1, shows the effect of different spindle# with constant speed which is 6 rpm on viscosity measurement of two brand sauces. Once a dial reading is obtained, the average of dial reading is multiply by the factor for the speed used by using formula viscosity (centipoise) = dial reading x factor. These viscometers viscosity is in units of Cp. For Red Horse sauce, the viscosity in centipoise obtained are 3275, 16250, 60000 and 20000 of 1, 2, 3, and 4 spindle# number respectively. For Starjuice sauce the viscosity in centipoise obtained are 7150, 38125, 170000 and 950000 of 1, 2, 3, and 4 spindle# number respectively. From Graph 2.0, it shows that the viscosity of sauce for both samples is increase when the spindle# size is increase. This is due to the size of spindle used. Besides, the flow resistance increases with the speed and size of the spindle. Thats mean, the lowest viscosity range can be covered by measuring with the biggest spindle at maximum speed. The highest viscosity range can be covered by measuring with the smallest spindle at the lowest speed. For a better reproducibility the same spindle/speed combination should be used for multiple tests (McGregor R.G, 2009). Rotational viscometers measure the torque required to turn a spindle in a sample of fluid at a known speed. These commonly-used viscometers are capable of measuring Newtonian and non-Newtonian fluids in a wide viscosity range. The spindle can be rotated at a fixed speed or at different speeds over time so that the viscosity can be measured over a range of shear rates (Sahi S., 2014). Fluids have different rheological characteristics that can be described by viscometer measurements. Sauce is time indipendent non-Newtonian fluid because it has different viscosity at different shear rates (different rpm speed) and it also known as pseudoplastic (Simonovich S., 2017). A pseudoplastic material displays a decrease in viscosity with an increase in shear rate and it also known as ‘shear thinning’. So the optimum speed and spindle to use for this sauce samples is 60 rpm and spindle number is 1. This is because the shear rate is greater at the speed 60 rpm and resistance very low at the spindle number 1.

CONCLUSION

In a conclusion, the experiment was succesfully conducted to determine the viscosity of the food products using viscometer depending on the effect of speed and spindle size. From the result obtained, it can be conclude that if the speed of viscometer is increase, the viscosity of sauce for both sample is decrease and if the spindle# number is increase, the viscosity of sauce for both samples is increase.

REFERENCES Brian Michael Godfrey. (2011). Experimental Results for Viscosity Measurements Performed on The International Space Station Using Drop Coalescence in Microgravity. Master's

Thesis,

University

of

Tennesse.

Retrieved

from

https://trace.tennessee.edu/utk_gradthes/972 Corvallis Environmental Research Laboratory. (2007). Transport of Oil Under Smooth Ice Ecological research series, United States Environmental Protection Agency Research reporting series: Ecological research. Environmental Protection Agency, Office of Research and Development. Retrieved from https://books.google.com.my/books?id=-VhRAAAAMAAJ&dq K. A. Abbas, S. M. Abdulkarim, A. M. Saleh and M. Ebrahimian. (2010). Suitability of Viscosity Measurement Methods for Liquid Food Variety and Applicability Infood Industry. Journal of Food, Agriculture & Environment. Vol.8, pp 100-107. Retrieved from https://www.researchgate.net/publication/236268492_Suitability_of_viscosity_measurement_me thods_for_liquid_food_variety_and_applicability_in_food_industry_-_A_review Robert G. McGregor. (2009). Viscosity: The Basics. Brookfield Engineering Laboratories.

Retrieved

from

https://www.chemengonline.com/viscosity-the-basics/?

printmode=1 Sarab Sahi. (2014). Viscosity Measurements in Food Products and Manufacturing. Retrieved from https://www.newfoodmagazine.com/article/15042/viscosity-measurements-foodproducts/

Sarah Simonovich. (2017). Understanding Viscosity and Non-Newtonian Fluids Will Help

Your

Ketchup

Game.

Retrieved

from

https://medium.com/petroleum-service-

company/understanding-viscosity-and-non-newtonian-fluids-will-help-your-ketchup-game584c1724a609#:~:text=Regardless%20of%20whether%20you%20shake,is%20dependent%20on %20shear%20rate.&text=With%20force%2C%20a%20thick%20fluid%20becomes%20thinner....