This is how its done in a lab for sampling. Farms use a similar process only on a much larger scale.:
Isolation of the Sugar, Lactose, and Albumin Proteins from Milk
After the isolation of casein, the milk mixture contains the sugar (lactose) and the protein (albumin).
Heat the milk mixture to about 75°C for about 5 min. on a sand bath. Heating results in a nearly
complete denaturization and precipitation of the albumins from the solution.
Decant the liquid in the beaker away from the solid into a clean plastic 10-mL centrifuge tube (borrowed
from the rack next to the Beckman centrifuge located at the end of lab 215). You may need to hold the
solid with a spatula when transferring the liquid. Press the solid albumins with a spatula to remove as
much liquid as possible and pour the liquid into the centrifuge tube. Save the albumins in the original
beaker. You should now have about 7 mL of liquid. If you have less than 2 mL, you need to add an
additional 1 mL to the albumin residue, heat to about 75°C, and decant, combining the two liquid
portions. This procedure will minimize the loss of lactose that may have crystallized along with the
albumin precipitate.
When the liquid has cooled to about room temperature, place it in the centrifuge. Make sure the
centrifuge is balanced by placing another plastic centrifuge tube filled with water to the same level as
your lactose tube, at a position 180° opposite the lactose tube. Centrifuge for 5 min according to the
instructions posted on the wall above the centrifuge.
Following centrifugation, decant the liquid away from the solid into a 50- or 100-mL beaker. Add 15 mL
of 95% ethanol to the beaker. Solids will precipitate. Heat this solution on a sand bath to about 60°C to
dissolve some of the solid. Pour equal amounts of the hot solution into two 10-mL plastic centrifuge
tubes (obtained from the rack next to the Beckman centrifuge in Room 215) and centrifuge this solution
as soon as possible before it cools appreciably. Centrifuge for 2 min. It is important to centrifuge the
solution while it is still warm to prevent premature crystallization of the lactose. A considerable quantity
of solid material is deposited on the bottom of the centrifuge tubes.
Remove the warm, supernatant liquid from the tube using a Pasteur pipet, and transfer the liquid to a
25- or 50-mL Erlenmeyer flask. (You can discard the solid remaining in the centrifuge tube.) Stopper
the flask and allow the lactose to crystallize for at least two days. Granular crystals will form during this
time.
Collect the lactose by vacuum filtration on a Hirsch funnel. Use about 3 mL of 95% ethanol to aid the
transfer and to wash the product. ?-Lactose crystallizes with one molecule of water of hydration per
molecule of lactose and therefore its formula is C12H22O11
.H2O. Weigh the product after it is thoroughly
dry. Calculate the weight percent of the ? -Lactose isolated from the powdered milk. Measure the
optical activity of ? -lactose by weighing and dissolving all of your sample in 2 mL of distilled water and
analyzing the solution by polarimetry (see Chapter 11 of the Lab Guide). Try to obtain a reading as
soon as the polarimeter readings stabilize to the nearest tenth of a degree (+0.1°C). Over a period of
time, one can observe a gradual reduction in the specific rotation.
Important: If the polarimeter continues to scan in the positive direction, reverses, and scans to the
negative values, and back again, then your sample is probably too cloudy. (Sometimes particles of
albumin will precipitate while the lactose crystals are growing.) If this is the case, you can remove the
sample solution from the cell and rinse the cell with methanol. Centrifuge the solution and return it to
the cell. If centrifuging does not remove the suspended particles (that is, the suspended particles are
really fine), fold a piece of filter paper in a cone shape and gravity filter the solution, and return it to the
cell.
Allow the albumins to dry for 2-3 days in the original beaker in which they were precipitated. Break up
the solid and weigh it. Calculate the weight percent of albumins isolated from the powdered milk.
Isolation of the Sugar, Lactose, and Albumin Proteins from Milk
After the isolation of casein, the milk mixture contains the sugar (lactose) and the protein (albumin).
Heat the milk mixture to about 75°C for about 5 min. on a sand bath. Heating results in a nearly
complete denaturization and precipitation of the albumins from the solution.
Decant the liquid in the beaker away from the solid into a clean plastic 10-mL centrifuge tube (borrowed
from the rack next to the Beckman centrifuge located at the end of lab 215). You may need to hold the
solid with a spatula when transferring the liquid. Press the solid albumins with a spatula to remove as
much liquid as possible and pour the liquid into the centrifuge tube. Save the albumins in the original
beaker. You should now have about 7 mL of liquid. If you have less than 2 mL, you need to add an
additional 1 mL to the albumin residue, heat to about 75°C, and decant, combining the two liquid
portions. This procedure will minimize the loss of lactose that may have crystallized along with the
albumin precipitate.
When the liquid has cooled to about room temperature, place it in the centrifuge. Make sure the
centrifuge is balanced by placing another plastic centrifuge tube filled with water to the same level as
your lactose tube, at a position 180° opposite the lactose tube. Centrifuge for 5 min according to the
instructions posted on the wall above the centrifuge.
Following centrifugation, decant the liquid away from the solid into a 50- or 100-mL beaker. Add 15 mL
of 95% ethanol to the beaker. Solids will precipitate. Heat this solution on a sand bath to about 60°C to
dissolve some of the solid. Pour equal amounts of the hot solution into two 10-mL plastic centrifuge
tubes (obtained from the rack next to the Beckman centrifuge in Room 215) and centrifuge this solution
as soon as possible before it cools appreciably. Centrifuge for 2 min. It is important to centrifuge the
solution while it is still warm to prevent premature crystallization of the lactose. A considerable quantity
of solid material is deposited on the bottom of the centrifuge tubes.
Remove the warm, supernatant liquid from the tube using a Pasteur pipet, and transfer the liquid to a
25- or 50-mL Erlenmeyer flask. (You can discard the solid remaining in the centrifuge tube.) Stopper
the flask and allow the lactose to crystallize for at least two days. Granular crystals will form during this
time.
Collect the lactose by vacuum filtration on a Hirsch funnel. Use about 3 mL of 95% ethanol to aid the
transfer and to wash the product. ?-Lactose crystallizes with one molecule of water of hydration per
molecule of lactose and therefore its formula is C12H22O11
.H2O. Weigh the product after it is thoroughly
dry. Calculate the weight percent of the ? -Lactose isolated from the powdered milk. Measure the
optical activity of ? -lactose by weighing and dissolving all of your sample in 2 mL of distilled water and
analyzing the solution by polarimetry (see Chapter 11 of the Lab Guide). Try to obtain a reading as
soon as the polarimeter readings stabilize to the nearest tenth of a degree (+0.1°C). Over a period of
time, one can observe a gradual reduction in the specific rotation.
Important: If the polarimeter continues to scan in the positive direction, reverses, and scans to the
negative values, and back again, then your sample is probably too cloudy. (Sometimes particles of
albumin will precipitate while the lactose crystals are growing.) If this is the case, you can remove the
sample solution from the cell and rinse the cell with methanol. Centrifuge the solution and return it to
the cell. If centrifuging does not remove the suspended particles (that is, the suspended particles are
really fine), fold a piece of filter paper in a cone shape and gravity filter the solution, and return it to the
cell.
Allow the albumins to dry for 2-3 days in the original beaker in which they were precipitated. Break up
the solid and weigh it. Calculate the weight percent of albumins isolated from the powdered milk.