Unit 9D?

Question 1

moisture sorption isotherm

Answer 1

having a graph with relative humidity and water content
examines how a food product behaves as a function of RH
change in weight in relation to RH

Question 2

relationship between Aw and RH

Answer 2

Aw= RH/100

Question 3

When we deal with foods do we say RH or Aw

Answer 3

Aw

Question 4

how to create moisture sorption isotherm?

Answer 4

measure the change in weight as a function of RH
set up a series of hermetically sealed chambers containing different saturated salt solutions

difference in weight- water lost or gain of moisture due to atmosphere in chamber?

Question 5

why do you need to specify the temperature on these graphs?

Answer 5

hotter air can hold more mass of moisture

need to specify the temperature

Question 6

what does MSI graph tell you?

Answer 6

1) expected moisture sorption behaviour
2) can indicate the effect of temperature
3) allows one to determine the expected Aw of a product at a specific temperature and RH which is the point where no absorption or release of moisture occurs
4) predict the final moisture content

Question 7

what is important in predicting product stability

Answer 7

Aw

Question 8

other factors affecting the drying process

Answer 8

1) reducing pressure ( under vacuum) reduces the temperature difference required in any drying process as the BP of water is reduced
2) latent heat (enthalpy) of evaporation
3) makeup/structure of the product

Question 9

Pasteurization vs blanching?

Answer 9

animal based product (P) and vegtables (B)

Question 10

Sulfiting

Answer 10

soaking food in sodium bisulphate and water for 10-30 mins

Question 11

Sulfuring

Answer 11

exposing fruits to fumes from buying sulphur for up to 4 hours
ex) dried apricots- to keep bright orange colour

Question 12

Drum drying *

Answer 12

rotating heated drums

Question 13

spray drying

Answer 13

very small drops of the food are sprayed into the top of a head chamber and tower and dehydrate

best for powdered milk

Question 14

vacuum drying

Answer 14

heated trays or shelves called platens transfer heat in vacuum chamber
expensive
highest quality

Question 15

freeze drying

Answer 15

dehydofreezing
expensive
used for high end products
maintains best flavour

Question 16

concentration *

Answer 16

lower shipping costs because less volume and extended shelf life

Question 17

the open kettle

Answer 17

frequent stirring
take a long time
not best choice

Question 18

heat evaporation method

Answer 18

enter and leaves the evaporator

Question 19

filtration method

Answer 19

small particles pass through files isolating and concentrating

Question 20

green peas must be soaked in sodium bisulphate solution before dehydration to eliminate enzyme activity? T or F

Answer 20

F- rich in thiamine, which is sensitive to sodium bisulphate

Question 21

for every 15 degree change in temperature, air holds how much more moisture?

Answer 21

twice as much

Question 22

does sulphiting extend or shorten drying time?

Answer 22

extend

Question 23

why do you sulphite

Answer 23

to control enzyme activity

Question 24

does sulphuring extend or shorten drying time

what are other advantages?

Answer 24

shortens, inhibits old growth and repels insects

Question 25

what do both sulfiting and sulphating destroy?

Answer 25

thiamine

Question 26

belt drying

Answer 26

tunnel dehydrator on a moving belt - foods can reach 5-7% moisture in just one hour

Question 27

fastest food drying process

Answer 27

spray drying

Question 28

dropping food through a heated chamber or tower

Answer 28

spray drying

Question 29

best for heat sensitive products such as milk, protein powder

Answer 29

spray drying

Question 30

best method for heat resistant products

Answer 30

drum dry

Question 31

which method produces the highest quality, why?

Answer 31

vaccuum drying bc is lowers the pressure and that lowers the boiling point and decresses heat damage

Question 32

what is vacuum drying used for

Answer 32

fruit juices

Question 33

% moisture content in intermediate-moisture foods

Answer 33

20-50%