NFS 4150 Experiment

1: Total Soluble Solids Estimation by Refractometer

Introduction

Analyzing sugar

content in the food and drink industry is more important than it seems. Products

that we consume every day, including wine, soft drinks, and juices, require an accurate

measurement of sugar content in order to perfect the taste and flavors of their

products before selling to stores and consumer. To find this in aqueous

solutions, testers must measure the sugar concentration in the unit of degree Brix

(°Bx).

Brix

degrees only pertain to solutions of pure sucrose. One degree Brix in a liquid is

present if it has the same refractive index as a solution of one gram of sucrose

in one hundred grams of sucrose and pure water solution. It is measured in percentage by weight of

sucrose in the solution (1). In the real world, the products set to be measured

do not contain only pure sucrose. They often contain various dissolved solutes and

types of sugars as well. But, the good thing about the Brix measurement is that

it will account for these other factors as well.

Measuring

the sugar concentration requires either a density meter or a refractometer. In this

experiment, we used the latter. This technology is commonly used to measure the

refractive index or Brix scale of a certain sample of liquid. The higher the

brix measurement is, the higher the concentration of sucrose is in the solution

(2). In this experiment, we used a handheld refractometer to confirm the Brix

scale of a 20 degree brix solution, Pepsi, Diet Coke, and Juice samples.

Materials and Methods

This

experiment was split into two parts. In activity 1, we prepared degree brix

solutions in two different methods, in method 1, we are given the task of

preparing a 20 degree brix solution. Initially, we start with weighing out 20

grams of sugar on a scale. Knowing this,

we must calculate the amount of water needed in order for the total weight of

the solution to equal 100 grams. The solution consists of two parts: sugar and

water. So for this step, all that is necessary to do is subtract 20 grams of

sugar from the 100 grams total weight to get the difference. The result is 80

grams of water. The density of water is 1 g/cm3 and we can assume

that 1 g of water is equal to 1 mL of water. To double check this, we took one

of the beakers, placed it on a balance, and zeroed the scale. Next, we poured

in enough distilled water to match to 80 grams. This did end up being around 80

mL of water. Then, we poured the 20 grams of sugar, that had been previously

weighed out, into the same beaker with the water in it. In addition, we added a

magnetic stirring rod and moved the beaker from the balance to the hot plate

that has an attached stirrer to mix the solution. Continue this until the sugar

is completely dissolved into the water. The final step is to determine the

degree brix. This is obtained with a refractometer. Taking a pipette, put one

drop onto the lens of the refractometer. The reading will be displayed inside.

As instructed, it should read 20°Bx (1).

In method 2, we again must prepare a 20 degree brix

solution. This time, we start by calculating the amount of sugar needed to make

100 mL of a 20 degree brix solution. By referencing a sucrose conversion table,

we find that the specific gravity of a 20 degree brix solution is 1.082 (1). Next,

we need to find the mass of this solution. Specific gravity is equal to density

so with some rearrangement, we find that mass is equal to volume times density.

We are given the volume of 100 mL and density of 1.082. This comes to 108.2

grams. The last calculation is to finally find the mass of sugar needed. Sugar

mass divided by total mass is equal to 20 divided by 100. We just found the

total mass to be 108.2, so the final answer is 21.64 grams of sugar. We weigh

the appropriate amount of sugar on a balance and add about 100 mL of water. Again,

we add a stirring rod and mix until the solution is completely dissolved. A

drop of this sample is again smeared on the lens of a refractometer and read to

the appropriate degree brix.

In activity 2, degree brix is measured again, but

this time we smear 3 different food samples that have been provided. The given

samples include grape juice, diet Coke, and Pepsi. In this activity, there is

no additional sample preparation necessary. One drop of the liquid simply is

placed on the refractometer for each liquid and read to the proper degree brix.

In this way, three different readings are obtained for the three liquids. These

readings are then compared to what was provided on each nutritional label.

Results

Table 1: Method 1 and Method 2 Measurements (degree

brix solutions)

Sugar

Water

Degree Brix

Method 1

20g

80 mL

19.5

Method 2

21.64g

100 mL

21.1

Method 1 Calculations

Preparing 20 degree brix solution:

1.

20g sugar

weighed

2.

Find amount

water needed

Method 2 Calculations

Calculating

sugar needed to make 100 mL of 20 degree brix solution:

1.

Specific gravity

of 20 degree brix solution is 1.082

2.

Density (d or specific

gravity) is equal to mass (m) divided by volume (V)

-When

rearranged,

3.

Find the mass of sugar

in 100 mL 20 degree brix solution

Table 2: Food Sample Degree Brix Measurements

Solution

Total sugar/serving

Serving size

Sugar percentage W/W%

Refractometer reading

Grape juice

49g

300 mL

16%

16 °Bx

Diet Coke

0g

222 mL

0%

0 °Bx

Pepsi

41g

355 mL

12%

11 °Bx

Discussion

and Conclusion

This experiment examined the purpose of a

refractometer and the use of a brix measurement by measuring sucrose content in

several solutions. In part one, our results slightly varied from the

theoretical result. Method 1 produced a degree brix of 19.5 and method 2

produced a degree brix of 21.1. Though not to different, we did not perfectly

get a reading of 20 from our 20 degree brix solution. I would account this

variance to human error. While measuring the amount of sugar and water we

needed on the balance, we could have been a few decimal points off from the

required mass. Also, during transfers, some of the sugar or water may not have

completely shifted over from the the weighing paper or graduated cylinder. In addition,

some blame may be given to systematic error. There is no way to tell if the

balance was completely accurate or tarred properly. This may have thrown off some

of our readings. Furthermore, activity 2 showed differences in refractometer readings

in comparison to the percentage labeled on the Nutrition Facts of the bottle as

well. The samples were many years old and contamination from the surroundings

could were additional limitations in producing correct results. However,

despite these errors, the discrepancies did not seem to affect the accuracy of

results too much due to the similarities between readings. Understanding sugar

content is closely tied to nutrition science and the food science industry.

References:

(1) NFS 4150 Food Science Lab “Total Soluble Solids

Estimation by Refractometer”, Wayne State University. Detroit, Michigan (accessed

22 January 2018).

(2) Echolls, T. How Does a Refractometer Work, 2017. https://sciencing.com/refractometer-work-5314561.html

(accessed 28 January 2018).