Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1040923
This invention relates to removing bitter flavour and
pea flavour from a pea flour.
Pea flours are an excellent source of vegetable protein.
They are made by grinding dried peas. The starchy components can
be separated to leave a flour that i8 higher in protein content.
For the purposes of this invention pea flour includes whole pea
flour and higher protein pea flours prepared by a process that
removes some starch components. Pea flours tend, however, to have
a bitter taste and a characteristic pea flavour which are objection-
able if they are to be mixed with other foods.
If one can efficiently remove the bitter taste and pea
flavour the utility o$ pea flour is greatly increased. So treated,
it would have extensive use as an additive to other food products
to increase their protein content and as a whole food. For
example, vegetable protein concentrates, made from soy bean, are
useful as meat extenders. They can be added to meat product~ to
supplement the protein content and increase food value. The cost
of vegetable protein is substantially less than meat protein and
the economics of the mixture will be readily apparent.
To be useful in food systems, the removal of the bitter
characteristic and the pea flavour must, however, be done in such
a manner that the end product possesse~ desirable functional pro-
perties. Two desirable functional properties of vegetable proteins
in food system- are their water binding and emul~ification c~pa-
c~t~e8.
The water binding capacities of vegetable protein~ can
be determined directly using a method such as the hydration capa-
city method of the American As~ociation of Cereal Chemi~ts (AACC
method ~6-20). The emul~ification properties of vegetable proteins
are complex and are influence~ by the other components in the
food sy~tem. It i~ well-known, however, that the protein must not
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104~9Z3
be substantially denatured if it is to be capable of interacting
with other components in a food system in the formation and sta-
bilization of emulsions. Therefore, high protein solubility of
vegetable protein concentrates is necessary for good emulsification
properties. A generally accepted method for the determination of
protein solubility is the nitrogen solubility index (N.S.I.) method
of the American Association of Cereal Chemists (AACC method 46-23).
Undenatured pea flour has a high N.S.I.
Moist steam has been used in the processing of protein
flours. It has, for example, been used in the processing of soya
bean flour. In the processing of soya bean flour it is co~mon to
extract the oil with a solvent to increase the protein content
and then treat the remaining meal and solvent with steam. The
~team is used primarily to remove the solvent. The effects of
the application of steam to soya bean meal have been the subject
matter of considerable previous study and they are well known.
One of the known effects is that it denatures the product to a
point where its nitrogen solubility index i8 reduced so that it
is not useful for further processing in many human food systems. ~ -
It has a low emulæification ability. Most of the product treated
in this way is used for animal feèd because of its low nitrogen
solubility index.
Pea flour is of a somewhat different nature to soya
bean flour, in that there is no oil that must be removed. It does,
however, have the bitter characteristic that must be removed before
it can be usefully used in a human food system. It also has a
pea flavour characteristic that is objectionable in same food
~ystems.
It is an object of this invention to provide a simple
method for debittering pea flour~ so that it can be incorporated
into human food system~. It i8 also an object of the invention to
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remove the characteristic pea ~lavour of pea flours.
It has been found that one can satisfactorily debitter
a pea flour and at the same time remove most of the pea flavour
for subsequent use in a human food system.
A method of removing bitter flavour and pea flavour from
a pea flour for addition to food systems, according to this inven-
tion, comprises the steps of contacting the flour with steam for
a time dura~ion sufficient to debitter the pea flour and cause
the steam to take up volatiles and then leading off the steam and
10 volatiles before a substantial cooked pea flavour develops. The
invention will be clearly understood after reading the following
detailed speciflcation.
In the drawings:
Figure 1 is a graph illustrating the range of steam
pressures and temperatures to which pea flour can be subjected to
debittering in an autoclave in accordance with this invention.
As indicated in the preamble to this application, the
¦ invention is concerned with the debittering and deflavouring of
a pea flour. Pea flours are manufactured by grinding dried peas
20 and then in the case of protein concentrates of pea flour separat-
ing the ground product to achieve a product with a higher protein
content. The manufacture of high protein vegetable flours is well
known. Generally speaking, the dried vegetable, bean or pea, is
ground into a fine powder and then separated by air-classifica- -
tion to achieve a concentration of particles having a size with
a high protein content and particles having a low protein content.
While peas have a protein content of about 24 per cent. The pea
flour will have a protein content in excess of this amount and -~
levels of 60 percent protein are readily achieved by air-classi-
30 fication. - ~ -
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~)40923
The flour, as manufacturedl has a bitter taste. It also
has an objectionable pea flavour. If the concentrate is to be
mixed with other protein food products to increase their protein
content, it must be debittered and the objectionable pea flavour
must be removed. This invention removes bitter taste and, at the
same time, removes pea flavour.
In a preferred embodiment of the invention, the pea
flour ls placed on a tray to a thickness of about one inch and
then placed in an autoclave and subjected to a low temperature
steam for a short period of time. It has been found that the
application of saturated steam at atmospheric pressure for a period
of between 12 and 30 minutes satisfactorily debitters the pea
flour. Other satisfactory conditions for debittering are steam
at about five p.s.i. between 3 and 9 minutes. Figure 1 i8 a graph
illustrating these and other conditions of temperature and pressure, ,~
for pressures up to 18 p.~.i. in the autoclave, for preferred
treatment of dry pea flour in accordance with the invention. The
area marked A represents conditions of application for moist heat
- to achieve a satisfactorily debittered product. It is apparent -~
20 that at pressures above 18 p.s.i. the time for proper treatment --
i~ very short. A pea flour debittered within the conditions marked
- in the area A is satisfactorily debittered without reducing the
nitrogen solubility index to a level wher`e it is not useful in
food systems. The lower line of this graph repre~ents the minimum
conditions necessary to debitter ~nd minimize the pea flavour. -~
~ Under these conditions pea flour solubility is reduced only slightly
i from an N.S.I. of 70 to an N.S.I. of not less than 50. The upper
curve ~epresents the maximum conditions tolerated which will not
result in any further significant reductions in the nitrogen ~olu-
bility index. The conditions defined by the area A, and its extra-
pol~tion to the right, therefore, characterize the production of
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1045~9Z3
debittered and deflavoured pea flour with an acceptable protein
denaturation, i.e. N.S.I. 50 - 70.
Typical pea flour, at the beginning of the autoclave
process, has a moisture content of about five percent. Moi~ture
contents in the order of less than 10 percent will be most com~on,
but it is contemplated that treatment of pea protein flour is
practical with moisture contents to 25 percent. As the moisture
content of the flour increases, the orange-brown colour of the
resulting product increases. High colour is an objectionable
feature of a protein flour for many uses~ For example, protein
flours are used as meat extenders and a high orange-brown colour
in tbe extender could be objectionable from an appearance point
of view. Excessive application of steam also causes a cooked pea
flavour in the resulting product which is objectionable.
Figure 1 used saturated steam. The steam is preferably
~aturated but it will be appreciated that variations to achieve
the equivalent of Figure 1 may be possible within the scope of
the invention. Lower amounts of steam are possible a8 long a~
moist heat conditions are maintained. A given quality of steam
20 must be applied long enough to remove the bitter flavour and the ~ -
pea flavour but not 80 long that a cooked pea flavour develops in
the product.
A steam pressure of about 0 p.s.i. is preferred because,
'~a8 appeares from Figure 1, the process can be carried out over a
wider range of time at thi~ pressure.
Following i~ a table of typical pea flour treatment
re~ults obtained by contacting a 60 percent protein pea flour in
an autoclave.
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TABLE ONE
AACC AACC
Steam NSI ~ydration
Test Temp. Pres~ure Time pH=6.3 Capacity
No. C p.s.i. Min. % % Flavour
_ - - 76 190 bit~er, pea
1 100 0 10 65 237 slight bitter,
slight pea
100 0 15 60 243 no bitter,
very slight pea
3 100 0 30 59 280 no bitter,
very slight pea
4 100 0 40 49 291 no bitter
very slight pea
5. 108 5 2 65 221 bitter, very
slight pea
6 108 5 5 59 230 no bitter,
very slight pea
7 108 5 7~5 61 271 no bitter,
very slight pea
8 108 5 10 52 302 no bitter,
very slight pea
9 116 10 2 60 237 no bitter,
very slight pea
116 10 5 55 246 no bitter,
very slight pea
11 116 10 10 45 253 no bitter, - `
slight cooked pea
12 116 10 20 37 322 no bitter,
slight cooked pea
13 121 15 1 59 265 ~o bitter
very slight pea
14 121 15 2.5 50 271 no bitter
very slight pea
i 15 121 15 5 40 291 no bitter
slight cooked pea
16 il6 10 30 20 260 no bitter,
slight cooked pea -
It will be noted that a sample treated with saturated
st-am at zero p.s.i. and 100C. for fifteen minutes had no bitter
flavour. It did have a slight pea flavour and a nitrogen 301u-
bility index of 60. An N.S.I. value of over 25 i8 de~irable.
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Thus, this product is a very satisfactory product. The slight
~ pea flavour is not objectionable and this product can be readily
f used in food systems without detection of a pea flavour.
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104()923
As processing time and/or steam pressure increases,
the N.S.I. is further reduced. Product treated to reduce N.S.I.
to 45 had a slight cooked pea taste that is undesirable. Product
with an N.S.I. of 76 was bitter. A desirable application of
steam to dry pea flour is one that reduces N.S.I. to between 70
and 50.
It will be noted that a~ steam treatment of the pea
flour increases and N.S.I. is decreased the residual pea flavour
is reduced to a minimum. As steam treatment is continued after
a minimum residual pea flavour is reached, a cooked pea flavour
develops. The development of a cooked pea flavour beyond a cer-
tain point can be a condition that limits the application of steam
for a satisfactory product. Thus, test ~15 has an N.S.I. of
40 which, under some conditions, might be satisfactory for a
pea flour for use in food systems. It also has a slight cooked
pea flavour that made it objectionable. Similarly tests 11 and
12 had a slight cooked pea flavour that made them objectionable.
A cooked pea flavour that i~ ob~ectionable i8 to an extent a
subiective considera~ion ~ut in practice it will readily be
de~termine~. Tt is not intended to claim within the scope of
this invention heat treatments that develop substantial cooked
pea flavour that is objectionable.
The debittering or removal of the bitter flavour is
thought to be a chemical reaction that takes place during the
moist heat trea~ment caused by the steam. The pea flavour that
i8 also removed by steam application ~ thought ~o be carried
away with the steam volatiles as they circulate through the
~ùtoclave. While it has been found satisfactory to arrange the
pea flour cn a tray to a thickness of about one inch, it will be ~ -
apparent that the thickness is deter~i~ed to achieve heat and
moisture penetration in a given case and that it i8 a matter of
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IV409Z3
adjustment by the operator. Vibration of the tray or other means
of agitating the flour, e.g. tumbling, could improve penetration
efficiency. Equipment other than an autoclave may well be used
to apply moist heat to the pea flour. Moreover, less than satur-
ated steam would most likely achieve a good result, but would
require more time.~ It is intended that variations in steam con-
dition from saturated as indicated in Figure 1 with appropriate
variations of tLme to achieve removal of bitter flavour and pea
flavour without introducing a substantial cooked pea flavour
10 8hould be con-qidered within the scope of this invention. It is
al~o intended that variations in the mixing of the steam with
the pea protein by physical or mechanlcal means with appropriate
variations of time to achieve a similar result should be considered
within the scope of this invention.
The foregoing experiments described in this invention
concerned the debittering and deflavouring of pea flours by ~
treatment of the dry or partially hydrated solid material with -
steam. It has also been found that aqueous slurry of pea flours
can be debittered and the pea flavour removed by injecting steam.
20 A gimple apparatus known as a iet cooker has been found suitable
; for the debittering and deflavouring of aqueous slurry of pea
flour. This apparatus is well-known in food processing industries
and i5 conventionally used for sterilization purposes. It
consists of two feed pipes, one for the aqueous slurry and the -
other for steam; a mixing chamber where the steam disperses in
and heats up the aqueous slurry, and finally an exit tube where
ii the heated slurry leaves the chamber. It is believed that the
s debittering and deflavouring of pea flour in such an apparatus
occurs by the same mechanisms which operate when the dry material
30 is ~reate*~with steam, i.e. the debittering occurs by some chem-
ical reaction during the heat treatment whereas the pea flavours ~ -
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are carried away with the steam volatiles. When an aqueous slurry
of pea flour is treated with steam in a jet cooker the flashing-
off of the pea flavours with the steam as it leaves the exit
tube is particularly effective. Subsequent removal of water by
spray drying or ring drying produces a bland product devoid of
any bitter or vegetable flavours. Other drying methods could be
used.
In a jet cooker the aqueous slurry is subjected to
steam treatment for a very short time, generally of the order of
one to ten seconds. Sufficient steam pressure is used to raise
the temperature of the aqueous slurry above 100C and preferably
to temperatures above 120C. At these elevated temperatures
more protein denaturation occurs than in the treatment of dry pea
flour but the extra denaturing is compensated for by another
acquired characteristic of the slurry treated product. It has
an increased hydration capacity.
By way of example, in experiment #17 a slurry of 35 pounds
of a 60~ protein pea flour in 65 pounds of cold water was steam
treated in a small jet cooker having an exit tube one inch I.D.
and ten feet in length. The exit valve was adjusted such that a
slurry temperature of 165C was reached. The products of this
treatment had no bitter flavour, no pea flavours and no cooked
pea flavour and was in the form of a cream coloured gel. A -
cream coloured p~wder was obtained by spray drying a homogenized -~
slurry of the gel in hot water.
In experiment $18 a water slurry of 60% pea:flour was
steam treated as described in experiment #17 excep~ that the
slurry pH was ad~usted with hydrochloric acid to 4.3 prior to
steam treatmen4~and then neutralized with sodium hydroxide to - ~-
30 pH 6.7 after the steam treatment. ~ ~
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104()9Z3
When aqueous 81urries of pea flours are treated in a
jet cooker to temperatures above 120DC the solubility of the
protein in water is significantly reduced ~uch that the recovered
dried products have N.S.I. values below 50%. However, as above
indicated, these debittered and deflavoured products have unique
functional properties which are very useful in food systems.
Following is a comparison of certain functional properties of
a 60~ protein pea flour treated in various ways.
TABLE TW0 `
AACC "
AACC Hydration
N.S.I. Capacity
Colour Flavour ~ %
Untreated cream Bitter, pea 76 190
Steam treated (Exp. 2) tan Very slight 60 243
pea
Jet cooked (Exp. 17) cream Bland 28 542
Jet cooked (Exp. 18) cream Bland 30 522
RoLbr-dried light brown Cooked pea 30 310
Table two summarizes ~everal of the properties of the
products treated according to this invent~on and also includes
data for a pea flour debittered by a conventional roller drying
process of an aqueous slurry. During roller drying the solution
or slurry is heated on laxge rollers or drums. In drying the
solids will generally reach temperatures of 100C or more. These
conditions lead to protein denaturation. Although this heat treat-
ment succes~fully debitters the pea flour it does not remove the
pea flavour. This is probably because during the heating of the `-
~lurry on the rolls in~ufficient steam is generated to carry
away the pea flavours. The pea flavours remained trapped within
the aqueou~ slurry and in addition cooked pea flavours develop. ~
By contrast, product made with jet-cooking of a pea flour siurry ~ -
or steam treatment of the dry pea flour had no objectionable
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104V9Z3
pea fla~our and no cooked pea taste.
Another undesirable property which occurs during roller
drying of pea flour slurries is the development of brown coloura-
tion. This phenomenum was observed, although to a far less
extent, during the steam treatment of dry pea flours. It was
also observed that the brown colouration intensified when the dry
materials were partially hydrated prior to steam treatment. For
some unexplained reason the brown colouration does not occur
~urinq the jet cooking of aqueous slurries of ~e~`flours.
A most surprising and extremely useful result from the
~et cooking treatment of a pea flour aal~eous slurry is the great
enhancement of the water binding capacity in the recovered pea
product as in~icated in the graph by hydration capacity. It is
known that heat treatment can often improve the water binding
capacitY of ve~etable protèins but the observed enhancement in
the pea protein concentrate deflavoured by the jet-cooking process
is very much greater than expected. This is revealed in Table Two
from a comparison of the hydration capacities for jet-~ooked and ~ -
roller-dried pea flours which have the same N.S.I. The usefulness
of a debittered and deflavoured pea flour with excellent water
binding capacity is readily apparent. Although the deflavoured
products from experiments 17 and 18 woula be expected to have
lower emulsification capacities than the deflavoured product from
exper~ment 2 their lower protein solubilities are compensated for -
~by`their superior water binding capacities to the extent that all
three products perform very satisfactorily in extending meat -
products. ` `~
The exact nature of the reactions responsible for the
improved water binding properties are not known. It i8 believed,
h~wever, that hydrolytic chemical reactions are occurring during
the steam treatment of aqueous slurries of pea flour in a jet cooker.
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104()923
To summarize, it has been found that in pea flours
bitter flavour and pea flavour can be removed by steam treatment
without incurring a cooked flavour to yield products with desirable
functional properties in food systems. Dry and partially hydrated
pea flours can be treated with a moderate Lmprovement in water
binding properties and with only a small decrease in protein
solubility. An aqueous slurry of pea flour can be treated without
browning to yield products with excellent water binding capacity,
moderate protein solubility and excellent dispersability in
aqueous systems.
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