Dehydrated lab report PDF

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Introduction Dehydrated, or food drying, is a method of food preservation on which food is dried. Traditional methods are removed water through evaporation by air drying, sun drying, smoking or wind drying.[1] Modern dehydration is a process that involves removal of water from a food system by the a...

Description

Introduction Dehydrated, or food drying, is a method of food preservation on which food is dried. Traditional methods are removed water through evaporation by air drying, sun drying, smoking or wind drying. [1] Modern dehydration is a process that involves removal of water from a food system by the application of heat under controlled condition.Many different foods can be prepared by dehydration. In some special environment areas, people remove the moisture in pork and fish and use high concentration of salt to inhibit microbial activity and maximize shelf life. Fruits and vegetables can also be dehydrated to obtain a different flavor. Also, fruits and vegetables contain enzyme, which cause them to ripen. Drying slows the effect of these enzymes, but some still work after the food has been dried, particularly vegetables. Dried fruits have been consumed historically due to their high sugar content and sweet taste, and a longer shelf-life from drying.[2] Osmotic dehydration is an operation used for the partial removal of water from plant tissue by immersion in an osmotic solution. Water removal is based on the natural and non-destructive phenomenon of osmosis across cell membranes. The driving force for the diffusion of water from the tissue into the solution in provided by the higher osmotic pressure of the hyper-tonic solution.[3] In the field of food science, the standard state is most often defined as the partial vapor pressure of pure water at the same temperature. Higher aw substances tend to

support more microorganisms. Bacteria usually require at least 0.91, and fungi at least 0.7.[4] The objectives of drying are to prevent microbial and enzymatic action by decreasing water activity below a critical point, reduce bulk which will reduce handling and transportation costs, eliminate refrigerated storage and so on.[5]

Method and material We got two steps of this lab, one is making drying curve, another is dried fruit. Drying Curve Weight of apple cubes sample:91.79g Weight of Dish:11.43g 1. Weight 80g sample 2. Put fresh apple cubes into oven at 70 oC at 1 minutes intervals for the first 5 minutes, then at 3 minutes intervals in the next 15 minutes, and then at 5 minutes intervals. Total drying time is 1 hour.

Moisture Determination: 1.

Take prepared aluminum dishes.

2.

Weight 10 g of sample into pre-weighted aluminum dish. Record the actual weight.

3.

Place dishes in a forced air oven preheated dry overnight.

4.

Safely remove with tong dishes from oven and place them in a dessicator to cool for 30 minutes.

Dried Fruit 3 apples, 1 banana, moderate sugar, cinnamon, water and lemon juice. 1. Wash, core and chop apples into small cubes. 2. Place in a pot with water, and add lemon juice, water and simmer until softened. 3. Place apples in blender, add sugar and cinnamon. 4. Puree the applesauce until very smooth. Add banana and blend again. 5. Determine the aw of the puree. 6. Line a drying tray with a fruit-leather sheet and spray with non-stick cooking spray.Pour the puree evenly, about 0.6 cm thick or quarter inch. 7. Dry at 60℃ about 8 8 hours in the food dehydrator until desirable leathery texture is obtained. 8. Determine the water activity of the finished product.

Result0 Time (min) Sample: Treatment: Unblanched Total Wt Sample wt 0 91.79 80.36 1

91.44

80.01

2

91.35

79.92

3

91.23

79.80

4

91.10

79.67

5

91.00

79.57

8

90.69

79.26

11

90.36

78.93

14

89.92

78.49

17

89.42

77.99

20

88.83

77.40

25

88.05

76.62

30

87.12

75.69

35

86.22

74.79

40

85.21

73.78

45

84.29

72.86

50

83.21

71.78

55

82.23

70.80

60

81.27

69.84

Drying Curve 82 80 78 76 74 72 70 68 66 64

0

10

20

30

40

50

60

Sample Calculation Initial Sample Weight – Final Sample Weight X 100 = % Moisture

70

Initial Sample Weight At 60 min, (80.36-10.09)/80.36*100=87.44% MR at minute 60 = (M-EMC)/(Mi-EMC) = M/Mi=0.8691

Moisture content 87.5 87 86.5 86 85.5 85 84.5 84 0

10

20

30

40

50

60

70

50

60

70

Moisture ratio 1.05

1

0.95

0.9

0.85

0.8 0

10

20

Sample Unblanched apple cubes

30

40

Dish No.

Wt of Dish 7

2.20

Wt. Wt MC % Sampl After drying e 10.30 3.82 62.9

Sample

aw

aw Dried product

Sliced Banana

0.932

0.219

Grapes

0.935

0.378

Sliced Apples

0.960

0.135

Sliced Strawberry

0.981

0.140

Apple Strawberry leather

0.996

0.412

Apple Banana leather (120 g sugar)

0.987

0.480

Apple Grape leather

0.998

0.463

Apple Banana leather (100 g sugar)

0.984

0.372

Commercial fruit leather

0.425

Commercial Craisins

0.519

Student Craisins

0.594

Sugar solution Pre-osmotic drying Post-osmotic drying

Brix 5.5 4.2

Discussion Our drying curve has a buffer zone at the beginning, and the rate of decline is low and unstable. At that stage, the moisture in the apple cubes changes from a stable state to an unstable state and evaporates in the subsequent heating. The buffer zone is a process in which moisture becomes unstable. Compare with the group which blanching treatment, our samples with unblanched treatment has lower mosture

condition, that maybe means blanched treatment can promote water evaporation. Brix of pre-osmotic drying and post-osmotic drying, one is 5.5 another is 4.2, When drying before osmotic, the surround water evaporation and sugar concentration increase, osmotic pressure increase, more sugar move into the fruit, drying after osmotic, the sugar concentration keep the same, because the water content didn’t change so osmotic pressure lower than pre-osmotic, less sugar remove to fruit so the brix also less than pre-osmotic. Source of error Because the measured data are all very accurate, some measurement errors cannot be excluded

Reference 1.Historical Origins of Food Preservation". Accessed June 2011. 2.Trager, James (1997). The Food Chronology: A Food Lover's Compendium of Events and Anecdotes from Prehistory to the Present. Henry Holt. ISBN 080505247X. 3.Rastogi,N.K., K.S.M.S.Raghavarao and K.Niranjan(2005). Developments in Osmotic Dehydration. Emerging technologies for food processing. ISBN 0-12676757-2. 4Rockland, L.B.; Beuchat, L.R. (1987). Water Activity:Theory and Applications to Food (2nd ed.). New York: Marcel Dekker. 5 lab manual...