LABORATORY WORK No 6

Performed by:

Martina Pospisilova, Eva Rampulova, Stela Pavlickova

Conditions:

t = 20.4 °C; p = 1018.5 hPa; φ = 47.3 %

Topic:

Concentration of Substancies in Foods

Tasks:

1.

Determine the mass fraction w of various substancies in foods by means of weighing.

2.

Find out the mass fraction w of various components in foods from the labels on the packings.

3.

Compare the mass fractions w of substancies by means of a bar chart.

Theory:

Substancies are divided in chemically pure ones and mixtures. The ingredients of a mixture can be expressed for example by means of mass fraction w. The mass fraction w(B) of the substance B in the system is equal to the share of mass m(B) of this substance contained in the system and the total mass m of the system: w(B) = m(B)/m.

The mass fraction w is an unindentified figure, always less than one (the mass of the ingredient is less than the mass of the whole system), for example w(B) = m(B)/m = 15/100 = 0,15. The mass fraction is often expressed in per cent, i. e. w(B) = m(B).100/m = 15.100 % / 100 = 15 %

Aids:

Scales, substances according to the table, packings of the foods.

Procedure:

1.

Establish the mass of the ingredient m (B), e.g. of salt, sugar etc.

2.

Establish the mass m of the whole system of solid state. If the system is of liquid state (tea. soup, ...), then establish the volume V by means of graduated measuring glass, establish the consistence ρ by hydrometer and compute the mass m of the system according to the formula m = V.ρ .

3.

Compute the mass fraction w (B) of the ingredient contained in the system and put it to table 1.

4.

Establish the mass fraction w (B) of the appropriate ingredient in the food from the label on the packing of the food product (table 2).

5.

Compare the mass fractions of various substances in foods in bar chart.

6.

Find the foods with the biggest and smallest mass fractions of substances.

Picture:

Table 1:

No

Name of the ingredient

Name of the system

Mass of the ingredient
m(B) [g]

Mass of the system
m [g]

Mass fraction
w(B) [%]

1.

sugar

sweet tea

4

114

3.6

2.

salt

soup

5

1000

0.5

3.

vermicelli

200

1000

20

4.

baking powder

apple strudel

2

400

0.5

5.

apple

248

400

62.0

6.

flour

150

400

37.5

7.

potatoes

potato

salad

700

1000

70

8.

cucumbers

113

1000

11.3

9.

salt

4

1000

0.4

10.

eggs

30

1000

3

11.

sugar

3

100

0.3

12.

onion

50

1000

5

13.

pepper

100

1000

10

14.

water

cucumber

pickle

3500

5200

67.3

15.

sugar

300

5200

5.8

16.

vinegar

1400

5200

26.9

Table 2:

No

Name of food

Name of ingredient

Mass fraction w(B) [%]

1.

mineral water

MATTONI

sugar

2.1

2.

calcium Ca²⁺

0.0114

3.

chlorine Cl^-

0.03

4.

magnesium Mg²⁺

0.005

5.

instant soup

vegetables

5.2

6.

doping for body builder

ISOline

(energy drink)

proteins

0.1

7.

carbohydrates

96

8.

fats

0.1

9.

milk

MILLI

proteins

3.2

10.

carbohydrates

4.9

11.

fats

1.5

Graph:

Conclusion:

In potato salad there can be 70 % potatoes, 11,3 % cucumbers, 10 % peppers, 5 % onions, 3 % eggs, 0,3 % sugar and 0,4 % salt. Apple strudel concists of 62,5 % apples, 37,5 % flour and 0,5 % baking powder. Sweet-and-sour cucumber pickle contains 57,7 % sugar and 16,9 % vinegar. Doping for body builder ISOline (energy drink) contains 96 % carbohydrates and  0,1 % proteins and fats. Sweet mineral water MATTONI contains 2,1 % sugar and about 0,01 % calcium Ca²⁺ and magnesium Mg²⁺ cations. Long-life medium-fat milk MILLI contains 1,5 % fat, 4,9 % lactose saccharide and 3,2 % proteins.