Did you know that it is not possible to freeze whole egg but you can freeze egg yolk? You cannot freeze tomatoes. Find out the reasons.

2. Food
Intended use
Freezing problem
Cooked egg whites
Salads, sandwiches,
Soft, rubbery, tough
Milk based sauces
casseroles
Curdles or separates
Sour cream
Toppings, salads
Separate, watery
Gelatin
Salads, desserts
weeps
Cucumbers, lettuce
salads
Become limp, lose
crispness
Fried foods
Ready to eat
Lose crispness,
become soggy
Reference: Taken from a handout provided by University of Minnesota. (additions done to the original)
http://www1.extension.umn.edu/food/food-safety/preserving/teaching-lessons-and-materials/docs/handout.pdf

4.  Eggs
along with
their outer shell.
 Cooked
egg white
 Anomalous
behavior
of water causes
expansion of the
liquid inside the egg
and causes the egg
shell to crack.
 It
becomes tough and
rubbery due to loss of
elasticity

5. comprises of
denatured
proteins held in
the form of an
elastic gel
freezing results
in the
concentration of
proteins than
present in the
original gel
Cooked
egg
white
the gel
structure
contracts
irreversibly
resulting in the
formation of a
tougher
structure
Increase in the
size of ice
crystals
penetrates this
gel structure
effectively
releasing some
elasticity

7. Formation of
ice crystals
may lead to
rupturing of
cells.
Inability of the
cells to
reabsorb all of
the frozen
water.
Reasons for
limpness in
certain fruits
and
vegetables
upon freezethaw.
Destruction of
the colloidal
structure of
the cell.

8.  Physical
damage due to ice crystals may lead to
loss of cell turgor and dislocation of endogenous
water.
 Excessive
leaching
of
water
soluble
pigments, water soluble vitamins and minerals in
the exudate.
 Free movement of cellular content may cause
mixing of materials that were previously
compartmentalized which may give rise to off
flavors and odors.

10. Gelatinization of starch upon addition to gravy
and subsequent heating.
Retrogradation and syneresis upon freezing.
On thawing, the gravy appears as a separated
and curdled mixture.

11. Scanning electron microscope pictures of starch gel after freeze-drying and
variable number of freeze-thaw cycles. (The hollow dark pits represent ice
crystals. 1C-1 freezethaw cycle,3C-3 cycles, 5C-5 cycles)
Reference: Hyo-Young Jeong, Seung-Taik Lim, “Crystallanity and Pasting properties of FreezeThawed high Amylose Maize
Starch”, Starch/Staerke 55 (2003), 511-517.

12.  Wheat
flour is not a wholly satisfactory
stabilizer.
 If it is used in combination with gelatin or
some other colloid, the coagulation may be
retarded.
 White sauces and gravies in which wheat
flour is largely or wholly replaced by waxy
maize or waxy rice flour are relatively more
stable.

14.  Sauces
like Mayonnaise and Hollandaise sauce
are examples of oil in water emulsions.
 In cases where the oils freeze before the water,
oil crystals are formed which act as bridges.
 If the interfacial layer between the fat droplets
is relatively thin, one oil crystal can penetrate
the other oil crystal leading to partial
coalescence.
 Upon thawing, these fat molecules completely
coalesce together thus separating from the
emulsion.

15.  As
the water freezes, its expansion causes
the fat droplets to squeeze together which in
itself may cause partial coalescence.
 This occurs when the water freezes before
the oil droplets can freeze.
 The emulsifiers may also be squeezed out of
the interface separating the droplets
creating some oil to oil contact.
 Upon increasing the temperatures , the oil
droplets completely fuse together effectively
separating from the continuous phase.

16. Microscopic images
of oil in water
type of emulsion.
A2- Freshly made
B2- After 5 freezethaw cycles.

17. 
Donald K Tressler, The freezing Preservation of
foods- Freezing of pre-cooked and prepared
foods, vol 2, Pg 16-17.

Food freezing-Today and tomorrow. Edited by:
W.B. Bald. Pg 117

http://www.dissertationtopic.net/doc/1642375

http://lnu.divaportal.org/smash/get/diva2:4278
21/FULLTEXT01.pdf

18. Sayali Sanjay Savant
M.Tech
Institute of Chemical Technology, Mumbai