APPENDICES
APPENDIX 7
THERMAL DATA FOR SOME FOOD PRODUCTS
|
|
|
|
|
|
|
Freezing
point
|
Percent
water |
Specific
heat
|
Latent
heat |
||
|
above
freezing
|
below
freezing
|
of
fusion |
|||
|
(°C)
|
(kJ
kg-1°C-1)
|
(kJ
kg-1) |
|||
| Fruit | |||||
| Apples |
-2
|
84 |
3.60 |
1.88 |
280 |
| Bananas |
-2
|
75 |
3.35 |
1.76 |
255 |
| Grapefruit |
-2
|
89 |
3.81 |
1.93 |
293 |
| Peaches |
-2
|
87 |
3.78 |
1.93 |
289 |
| Pineapples |
-2
|
85 |
3.68 |
1.88 |
285 |
| Watermelons |
-2
|
92 |
4.06 |
2.01 |
306 |
| Vegetables | |||||
| Asparagus | -1 | 93 |
3.93 |
2.01 |
310 |
| Beans (green) | -1 | 89 |
3.81 |
1.97 |
297 |
| Cabbage | -1 | 92 |
3.93 |
1.97 |
306 |
| Carrots | -1 | 88 |
3.60 |
1.88 |
293 |
| Corn | -1 | 76 |
3.35 |
1.80 |
251 |
| Peas | -1 | 74 |
3.31 |
1.76 |
247 |
| Tomatoes | -1 | 95 |
3.98 |
2.01 |
310 |
| Meat | |||||
| Bacon | -2 | 20 |
2.09
|
1.26 |
71 |
| Beef | -2 | 75 |
3.22 |
1.67 |
255 |
| Fish | -2 | 70 |
3.18 |
1.67 |
276 |
| Lamb | -2 | 70 |
3.18 |
1.67 |
276 |
| Pork | -2 | 60 |
2.85
|
1.59
|
197 |
| Veal | -2 | 63 |
2.97 |
1.67 |
209 |
| Miscellaneous | |||||
| Beer | -2 | 92 |
4.19 |
2.01 |
301 |
| Bread | -2 | 32-37 |
2.93 |
1.42 |
109-121 |
| Eggs | -3 | 3.2 |
1.67 |
276 |
|
| Ice cream | -3 to -18 | 58-66 |
3.3 |
1.88 |
222 |
| Milk | -1 | 87.5 |
3.9 |
2.05 |
289 |
| Water | 0 | 100 |
4.19 |
2.05 |
335 |
Based on extracts, by permission, from ASHRAE Guide and Data Books.
Specific heats, latent heats of freezing and thermal conductivities of foodstuffs can be estimated if the percentage of water in the foodstuff is known. If this percentage is p then:
(a) Specific heat
= 4.19p/100 + 0.84(100- p)/100 kJ kg-1 °C-1
above freezing
= 2.1 p/100 + 0.84(100- p)/100 kJ kg-1 °C-1
below freezing.
(b) Latent heat = 335p/100 kJ kg-1
(c) Thermal conductivity = 0.55p/100 + 0.26(100 -p)/l00 J m-1
s-1 °C-1 above freezing
= 2.4p/100 + 0.26(100 -p)/l00 J m-1 s-1 °C-1
below freezing.
These equations represent a considerable over-simplification
so they, and also the tabulated data, should be used with caution, particularly
in the region between 0°C and -18°C. Freezing of foodstuffs occurs
over a range of temperatures and not at any fixed point. For complete
data the only really satisfactory source is a thermodynamic chart such
as those prepared by Riedel (for example, in DKV Arbeitsblatt 8-11,
1957 C. F. Muller, Karlsruhe) for lean beef, and also for egg yolk, potato
and fish.
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