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NFS 4150 Experiment
1: Total Soluble Solids Estimation by Refractometer

Introduction

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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%

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
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).