Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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"FOOD PRDDUCT AND PRDC$SS"
The present invention relates to food products and to processes for
their preparation and use. The products may be intended either for human or for
animal consumption.
There are already available on the market a considerable number of pre-
pared foods which require relatively little cooking or other treatment to bring
them into a condition suitable for consumption. Such products are com~only
referred to as "convenienoe foods".
KnGwn foods of this kind fall generally under three headings - namely
canned, dried and frozen products. Each of these types of food, however, has
its cwn problems or disadvantages.
Canned foods are bulky and rely totally on a hermetic seal and thus on
the integrity of the can to maintain product quality.
Dry foods tend to show the lowest palatability. In particular,
rehydratable dry products tend to be regarded by the consumer as being of low
quality and palatability, and a nu~ber of technological problems have yet to be
overcome. Much work has gone into finding ways of retaining palatability,
flavour and texture by reducing the denaturation ef~ects of heat and solute con-
oentration. Although on a laboratory scale some sucoe ss has been achieved with
oertain products, major difficulties arise when this work comes to be translated
into co~mercial scale operations.
Although frozen foods have gained rapidly in sales in the last fifteen
years, and more especially the last five years, with a large increase in hc~e
freezer ownership, there are still problems associated with their use.
me current frozen food market can be divided into th~ee sectors:
(1) Uncooked frozen convenience foods such as blanched vegetables, fish fingers
and beefburgers, which do not require thawing before cooking. They do, hcwever,
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require cooking and, in order that they should not require thawing, they must of
necessity be in small pieces or have an artificially induced large surface area,
such as boil-in-the-bag foods. The cooking and preparation time of these foods
is usually from 5 to 25 minutes.
(2) Uncooked frozen bulk foods such as frozen whole chicken or meat joints.
mese products must be thawed before cooking takes plaoe and the total prepara-
tion time can be more than 24 hours.
(3) Cooked ready-to-eat foods such as frozen complete meals and roast meat
slices. These require heating in a conventional oven for more than 10 minutes
or ex$ensive alternatives, such as microwave heating.
All these p~oducts show the same major disadvantage. They require
extensive thawing and/or cooking to reach a suitable state for consumption.
Apart frcm the use of freezing in the preservation of foods, it is
also kncwn to use a freezing process to con oentrate products. me ioe formed on
freezing a liquid product may be removed from the product, e.g. fruit juioe ,
leaving a product of lower moisture content, which can be rec~nstituted. m e
extreme case is the removal of the greater part of the ice under vacuum - the
freeze~drying process - which produoes instantly rehydratable products, e.g.
instant coffee. An essential limitation of freeze-ooncentration is that it can
only be applied to liquids. Freeze-~rying can be applied ~o both solids and
liquids, but the resulting products are designed for stability under ambient con-
ditions and, although reconstitution is rapid, such products incor,oorating solid
pie oes do not have acoeptable palatability or texturs.
It is an object of the present invention to provide preserved food
products which can be quickly and easily brought into a condition for consump-
tion with acc~ptable or advantageous organoleptic properties.
mis invention provides a frozen food product which is readily penetr-
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able by thawing water comprising a frozen foodstuff or a mLxture of foodstuffshaving a moisture content below that which said foodstuff or mLxture of food-
stuffs has when ready for consumption, the product containing b~th frozen and
unfrozen water and also containing at least one physiologically tolerable water
soluble salt in an amount sufficient to maintain unfrozen water in the product
but not exceeding 4% by weight calculated on the frozen product for any indivi-
dual salt and not exoeeding a total of 10% by weight calculated on the frozen
product when more than one salt is present.
The product of this invention is reconstituted by adding warm or hot
water in such a quantity that the moisture content of the product is restored to
its normal value while at the same time the temperature of the product is raised
to its normal value for consumption.
m e invention also provides a method of preparing a frozen food pro-
duct which comprises adjusting the moisture content of a food stuff or mLxture
of foodstuffs to a level below its normal value in the foodstuff(s), incorporat-
ing in the foodstuff(s) before, during or after said adjustment in moisture con-
tent at least one physiologically tolerable water soluble salt and freezing said
salt containmg moisture depleted foodstuff to produce a frozen product contain-
ing both frozen and unfrozen water into which thawing water can readily pene-
trate, said salt being added in an amount at least sufficient to ensure the pre-
sen oe of unfrozen water in the product bu~ not exoeeding 4% by weight of the
frozen product for any individual salt and not exceeding a total of 10% by
weight of the frozen product when more than one salt is present.
Preferably the moisture oontent of the foodstuffs is reduced to a
level within the range of fram 30 to 80% advantageously 35 to 60% and preferably
40 to 55% of the original moisture oontent of the raw, untreated food.
Moisture adjustment may be effected by removing water from fresh ~ood-
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stuffs or by partially rehydrating a dried, optionally pcwdered material. Thislatter method may be used, for example, for producing reconstituted meat-like
products frcm textured vegetable protein.
Products obtained in accordance with the present invention can combine
the palatability and texture of frozen foods with the ease of preparation of
rehydratable foods. It is possible and highly desirable to achieve both thawing
and rehydration in a matter of seconds, and certainly within a few minutes.
To achieve the best results, three important factors come into con-
sideration.
First the frozen product must be porous, or otherwise readily penetr-
able, so that both thawing and rehydration are rapid and homogeneous. This can
be achieved either by manufacturing a product with small particle size or by
appropriate treatment of larger pie oes with a suitable texture. An important
preferred feature of the invention arises frcm the discovery that chunks or
pie oes of foodstuff can be used in the product, and that suitably treated these
will also thaw and rehydrate rapidly.
Second, the initial moisture content is so adjusted that when a suit-
able amount of water of a higher temperature is added to the fxozen product to
bring it to eating temperature, then the moisture content of the final product
is approxImately that which would be expected in the unfrozen product. This
oondition does not set a fixed limit to either the relative qu~ntity or the
te~perature of the water added at the thawing/rehydration stage. These tw~
factors depend entirely on the type of product. A meat-based product can be so
formulated to be consumed at 20-40C by animals or, by reducing its initial
water oontent, by mcreasing the volume of added water or by increasing tempera-
ture of added liquid, to be consumed at 50-70 & by humans. It is the total
quantity of heat (water temperature x volume) added which is important.
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Third, a proportion of the water in the product should remain unfrozen.
mis a~ount is controlled by the water-soluble salt components of the product.
The aqueous phase of a solution of a given solute in contact with ioe at equili-
brium is always at the same con oentration. Therefore, the greater the quantity
of added salt, which will usually be sodium chloride, the greater the amount of
water needed to dissolve it (i.e. which will remain unfrozen) at a given tempera-
ture below freezing. Control of the amount of frozen water is critical to the
final temFerature of the product because the latent heat of melting for i oe is
80 cal/g, as compared with the specific heat of water of 1 cal/g. Eighty times
as much heat is abstracted fron the added water to melt each gram of ice as to
raise the tem~erature of the gram of melted ice one degree. The eating tempera-
ture of the product can therefore be controlled by this ratio of frozen/unfrozen
water in the product. It is possible to calculate a relationship between water
content, soluble solids content and amount and temperature of added water for
the product which gives a desired eating temperature and concentration.
For examplel where the frozen product consists or a grams of unfrozen
water (containing a small quantity of soluble food solids), b grams frozen water
and c grams food solids and has a temperature of -KC, and where it is to be
raised to a consumption te~,perature of +P & and a final moisture content of W~O
by the addition of d grams of water initially at +TC; then, taking the specific
heat of the water to be 1, that of ice 0.3 and that of food solids 0.8 and the
latent heat of fusion of the ice 80 cal/gram:
a(K+P) + b(0.3K + 80 + P) + 0.8c(K+P) = d(T - P) ........... (1)
and a +-b--+~ = O.OlW ................................... . (2)
Assuming that the final reconstituted product is to contain l~o sodium
chloride (a typical value), which is supplied by the salt content of the frozen
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product, and bearing in mind that the concentration of sodium chloride solution
in equilibrium with ice at -20 C is about 20%, then:
a = 0.04(a + b + c + d) ........... (3)
Finally, where the result is to be expressed in percentages:
a + b + c = 100 ................... (4)
~ s an example of the application of these equations, taking the case
of a pet food stored at -20C and intended to be reconstituted with boiling
water to a desirable moisture content of 80% and salt content of 1~ at a tempera-
ture for consumption of 30C, the above equations indicate the following require-
ments:
Frozen product:
Food solids 41.5%
Frozen water 47.9%
Unfrozen water 8.5%
Salt 2.1%
Rehydration:
Frozen product at -20& 100 parts
Water at 100C 111 parts
Salts other than sodium chloride can be used, but the weight necessary
for the equivalent anti-freeze effect is usually higher. Mono sodium glutamate
m~y for example be added as a flavour enhancer, instead of or in addition to
sodium chloride. m e amount of any individual salt added is preferably from 0.5
to 4%, especially 0.5 to 2.5%, by weight calculated on the frozen product and is
usually of the order of 2% by weight.
The production of a food product according to the invention requires
that the moisture content of a foodstuff be adjusted prior to freezing. Reduc-
tion of moisture content can be achieved (a) by drying or (b) by draining out
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liquor. These different techniques can be illustrated by the follcwing examples
of their practice.
(a) For a meat product of normal isture content (75-80%), the meat is
cooked or heated until sufficient moisture has been removed to leave
a moisture content of 45-50%. After freezing, reconstitution is
achieved by addition of a quantity of water equivalent to that evapor-
ated, if the original product is to be exactly reproduced, or a
greater amount if, for example an additional quantity of sauce or
gravy is desired.
A similar result can be achieved by starting with a dry or dehydrated
material of fibrous texture, for example textured vegetable protein (TVP) or
dried meat can b used for this purpose. mis material is partially rehydrated
(to 35-60% by weight H2O) with water containing some water soluble salt before
freezing. me fibrous texture and the inclusion of the water soluble salt com-
ponent, which leads to a proportion of unfrozen water within the pieces, surpris-
ingly combine to give pieces which thaw and rehydrate within seoonds on contact
with hot water. In a preferred embcdiment this partial rehydration is carried
out with liquors cooked out of the meat components of the product, in which has
been dissolved, the appropriate quanti-ty of salt. With pieces which are too dry,
rehydration occurs too slowly; where they are too wet or without added salt,
thawing is not uniform; with larger amQunts of salt, the process is technically
satisfactory, but the taste of the final product may be unsatisfactory.
As an alternative to partially dryi~g a food product by evaporating
water therefrom it is possible to achieve a similar result by bringing the food
product into contact with an absorbent material that will abstract the requisite
amount of moisture from the fosd product. m is method may be used for example,
when it is ne oessary that the food product should not be cooked for the long
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period that may be necessary to evaporate the necessary a~ount of water from the
food product.
(b) After the meat has been cooked, liquors in excess of the required
moisture content can be drained or pressed out of the solids. The
liquor can be discarded or absorbed into a dry material such that the
moisture content of the dry material is increased to the same level as
the pressed or drained meat.
In reconstituting food products according to the invention to bring
them into a condition for consumption, a quantity of liquid must be added to
bring the product to a temperature and moisture content suitable for eating.
For a given eating temperature the quantity of added liquid needs to be judged
to ~ 25% to give an acceptable final product for a product of the meat in gravy
type. In a domestic situation one would not expect the housespouse to weigh out
the liquid onto the product.
A convenient way of measuring out the required quantity of rehydrating
liquid for this product provides a preferred feature of this invention. The
material is put into a container and just covered with rehydrating liquid. This
can readily be judged by eye. For convenience the buIk density of the product
can be varied according to the amount of liquid needed to attain a particular
final temperature and analysis. Although there are other ways of measuring the
amount of rehydrating liquid this appears to be the most convenient.
The buIk density of the product can he varied or controlled in several
ways:-
(1) m e prefrozen product may be pressed to the correct density before
freezing.
(2) Cther raw materials of appxopriate bulk density may be added to adjust
the overall density.
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(3) The material may be mechanically treated to decrease the density be-
fore freezing, e.g. by emulsification or foaming.
(4) The material may be mechanically treated as it is freezing, e.g. by
whipping.
(5) The material may be mechanically treated after freezing, e.g. by grind-
ing to reduce the buLk density.
me following illustrative Examples of the invention are given by way
of example only. All parts and percentages are by weight unless the
context indicates otherwise.
E_ample 1. Animal Food.
Meat offal was minced through a 1 cm mincer plate and cooked at loo&
for 10 minutes. On heating, meat liquor cooks out of the meat. me meats were
separated frcm ~he liquors and pressed to remove more liquor so that the mois-
ture content of the pressed meat was about 50-60%.
95.2 parts of pressed meat were minced with 2 parts salt, 2 parts of
carboxymethylcellulose (aMC) and 0.8 parts of caramel. The ingredients were
tightly pressed to a bulk density of about 0.5 g/ml and frozen at a temperature
of -20C in a domestic deep freezer.
This frozen product, when mixed with enough boiling water just to
oover the product, thawed an~ rehydrated within 30 seconds to give a final
temperature of 33C and a moisture content of 75%. Th~e reconstituted product
consisted of meat in thickened gravy and had a glossy appearance. It was highly
ac oeptable to cats and dogs.
Example 2. Animal Food.
Cboked m mced meat offal was prepared as in Example 1 and pressed to
remove excess liquors. 93.2 parts of this were mixed with 2 parts salt, 4 parts
pregelatinized starch (Instant Cleargel - Trade Mark), and 0.8 parts caramel.
This was prepared as in Example 1.
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On rehydration with enough boiling water just to cover the frozen pro-
duct, this formulatian gave a final product with thickened gravy of glossy
appearance at a temperature of 30 &.
Exa~ple 3. Animal Food.
Pressed meats were prepared as in Example 1. 95.8 parts of this were
used with 2 parts salt, 0.8 parts carob, 0.6 parts xanthan and 0.8 parts
caramel. mis was prepared as in Example 1.
~n rehydration with boiling water, thickening of the gravy was slower
than in Examples 1 and 2, but within one minute a reconstituted product with a
glossy gel at a temperature of 30C was obtained.
Example 4. Animal Food.
Pressed meats were prepared as in Example 1 and 92.2 parts were mixed
with 4 parts of alginate (Manugel GHB - Trade Mark), 1 part dicalcium phosphate,2 parts salt and 0.8 parts of caramel. This was frozen as in Example 1 and when
reconstituted as in Example 1 gave a final product with a dull gel.
Example 5. AnLmal Food.
This Ex~mple uses as gelling agent a crude pectinaceous material
(cit~us peel) the pectin content of which hac, been de-esterified to a degree ofesterification belcw 20~ ("treated peel").
Pressed meats were prepared as in Example 1 and 92.2 parts were mixed
with 4 parts of treated peel, 1 part dicalcium phosphate, 2 parts salt and 0.8
parts of caramel. This was frozen as in Example 1 and when reoonsituted as in
Example 1 gave a final product with a dull gel.
These first five Examples have involved discarding the cookout liquors
from the meat. As a first step to preserving this valuable by-product an alter-
native method of removing moisture from the meat can ke used.
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Examples 6 to 10. Ani ~ Food.
Meat offal was minced through a 1 cm mincer plate and cooked at loo&
until most of the liquor which had cooked out of the meat was reduoe d. This
meat was then placed in a heated air oven at loo& on a tray, and left until
the moisture content was reduced to approximately 50~. This process retains the
water soluble components of the liquor while the actual mDisture content is re-
duced.
This dried meat can then be treated in exactly the same way as the
pressed meats in Examples 1 to 5 (Examples 6 to 10 respectively in Table 1) to
give equally acceptable products.
Table I
Example: _ 7 8 9 10
Dried meat 95.2 93.2 95.8 92.2 92.2 (parts)
Salt 2 2 2 2 2
Caramel 0.8 0.8 0.8 0.8 0.8
CMC 2
Starch - 4
Carob - - 0.8
Xanthan - - 0.6 - -
Alginate - - - 4
Treated peel - - - - 4
Dicalcium phosphate
Instead of the moisture content being reduced ky evaporation, an alter-
native is to add dry ingredients which reduce the overall moisture content, as
shown in the following Examples 11 and 12.
Ex~mple 11. Animal Food.
The meat offal as previously described was cooked at loo& for 10
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minutes. Lcw mDistUre content ingredients were then mixed with the meat cookaut
liquors to reduce the overall moisture content to 50%. A suitable formulation
is:
Minced meats 55 parts
Potato protein 5 parts
Biscuit 5 parts
TVP 5 parts
Greaves, dry 10 parts
Meat and bone meal5 parts
NaCl 2 parts
Tallow 3 parts
Caramel 0.1 part
Xanthan 0.6 part
Carob 0.8 part
Dried deoolourised bload8.5 parts
The mix should be agitated during freezing or milled after freezing to
avoid the formation of solid frozen pieces which will not readily thaw.
Example 12. Animal Food.
Meats were oooked as in Example l and frcm that process the cookGut
meat liquors were saved. 87 parts of these liquors were mixed with 13 parts of
wheat flour, and the resultant dough was roller dried and ground to a pcwder.
By this means the liquors and their flavaurs and nu~rients are saved and, at the
same time, the starches in ~he flour are gelled, thus removing any need for the
addition in the final formula of a pre-gelled st æch.
The final formulatian for this example was 78.8 parts of cooked
pressed meats, with 19 parts of roller-dried dough of flo~r and ccokout liquors,
2 parts salt and 0.2 part caramel. This mix was frozen according to the instruc-
tions in Example 1.
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Cther suitable binding agents for the cookout liquors, which may be
incorporated prior to roller d~ying, include soya meal and gluten. Hcwever, the
addition of a gelling agent in the final formulation is desirable when these
ingredients are used.
~ Iowever, a particularly preferred embodiment of this invention is
based upon the use of meat cookout or press liquors to partially rehydrate TVP.
This is exemplified in Example 13.
Example 13. Animal Food.
Mbats were cooked and pressed as in Example 1. In the liquors were
dissolved salt and caramel. An equal weight of dry TVP was added to the liquors
and the whole agitated until the TVP had taken up the liquid. This partially
rehydrated TVP was then muxed with the pressed meats. The amount of salt and
caramel added were such as to produce concentrations of 2% and 0.8% respectively
in the frozen product.
mis mlxture can then be frozen as in Example 1 and on thawing and
rehydration gives a chunky product of good appearance. me liquors are leached
out of the IVP by the liquid added to thaw the product. However, if it is re-
quired to form a gravy, the pressed meat and TVP can be ooated with the thicken-
ing agents as in Examples 1 to 5, simply by agitating with a powder mux of these
agents.
It is also possible to combine the technologies of Examples 12 and 13,
as shown in Example 14.
Example 14. Animal Focd.
In this case part of the liquors pressed out of the meats were used to
manufacture TVP. A formulation for a vegetable protein dough is:-
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Liquors 30 parts
Defatted soya flour60 parts
Maize meal 10 parts
Sulphur 0.02 parts
This dough was extruded from a cooker-extruder at 150&. After being
cooled the resulting TVP was combined with the remainder of the liquors to give
a partially rehydrated TVP which could be used as in Example 13.
The principles of this invention are not limited to the preparation of
am mal foods. It is also possible to manufacture hunan food formulations, as
exemplified in Example 15.
Example 15. Human Food.
Braising steak was minced through a 1 cm mincer plate and cooked at
100C for 10 minutes. Liquors were pressed out of the cooked meat as in Example
1, and to these salt and caramel were added as in Example 13. These liquors
were ~h~n used to Fartially rehydrate TVP (Bontrae 7240 - Trade Mark) and there-
after the product was treated as in Example 13. Gn rehydration the product had
a pleasant beefy aroma and had the appearance of Chow Mein because of the tex-
ture of the TVP. Furthermore, sin oe Bontrae is a very absorbent fonm of TVP,
more hot liquor can be added so that the eating temperature can be close to
70-80C, without giving excess gravy.
