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Unit 7 Working with Complex Food Systems
Reverse osmosis is used to concentrate
fruit juices with limited use of heat.
This protects the fl avor compounds and
vitamin C in the juices, which can be
damaged by heat used in evaporation.
Sometimes a series of fi lters are used
with reverse osmosis to separate several
components from a food product. One
example is whey, the liquid left from the
production of cheese. The food industry
uses the components of whey for a variety
of functions. Whey proteins act as foam stabilizers, gelling agents, and
emulsifi ers. They are used in meat extenders, processed cheese, pasta
products, and snack foods. Lactose from whey is used in icings, toppings,
and candies. When combined with sucrose, lactose helps keep foods
from being too sweet. It also increases viscosity and reduces crystal
size. The result is a smoother mouthfeel in candy and confections.
Athletes Under Pressure
Adequate water is especially important
to the athlete. During physical activity, the
body loses water through perspiration.
Perspiration causes a drop in osmotic pressure
outside the cells. Water must be consumed.
Otherwise, osmosis will move water out of the
cells to balance the concentrations on either
side of the cell membrane. If these losses are
large and the water is not replaced, a chain
reaction begins.
• Blood volume decreases—blood pressure
drops—heart rate increases to compensate.
• Transport of nutrients for energy is slowed.
• Transport of waste products in slowed.
• As water loss increases, perspiration
decreases.
• Less perspiration results in increased
body temperature.
• A 2% loss of body weight in fl uids
decreases performance. This equals 1.4 kg
(3 pounds) for a 67.5 kg (150 pound) athlete.
This much fl uid can be lost in 90 minutes
of physical activity on a cool day.
• Heat cramps occur
at a 5% loss of body
water weight. Heat
exhaustion occurs
at 5% to 10% water
loss. Heat stroke occurs
when water loss exceeds 10%.
If you are thirsty, you are dehydrated.
However, it is important to remember that
thirst is satisfi ed during physical activity
before body fl uid needs are met. It is a good
idea for athletes to weigh themselves before
and after an exercise session. For every
kilogram (2.2 pounds) lost during physical
activity, athletes should drink 1 L (4½ cups)
of water or sport beverage. During physical
activity, an athlete should consume 125 mL
(½ cup) of water or sport beverage every
20 minutes. Sport beverages provide
osmotically balanced water along with sodium,
potassium, and glucose. Some athletes fi nd
them more appealing than plain water and
are therefore more likely to drink them and
avoid dehydration.
In some food preparation procedures,
such as making homemade jelly, linen towels
are used to separate juices from pulp. To avoid
adding unwanted fl avors, do not use a linen
towel that has had fabric softener added in
the laundry.