PROCEDE DE PREPARATION DE CONCENTRES PROTEIQUES A PARTIR DE LA DRECHE DE BRASSERIE

PROCESS FOR PREPARING PROTEIN CONCENTRATES FROM BREWER'S SPENT GRAIN

Abrégé anglais

ABSTRACT
A method of preparing protein concentrate from brewers'
spent grain comprises extracting said brewer's spent grain with
sodium dodecyl sulfate to solubilize the protein thereof, and
thereafter removing a substantial proportion of the protein in
solution.

Revendications

The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A method of preparing protein concentrate from brewer's
spent grain comprising extracting said brewer's spent grain with
sodium dodecyl sulfate to solubilize the protein thereof, and
thereafter removing a substantial proportion of the protein in
solution.
2. A method as claimed in Claim 1 wherein said protein is
removed from solution by precipitation with ethanol.
3. A method as described in Claim 1, wherein said protein is
extracted with sodium dodecyl sulfate at an elevated temperature,
and removed from solution by precipitation with ethanol followed
by refrigeration.
4. A method as described in Claim 3, wherein said protein is
extracted with sodium dodecyl sulfate at a temperature of from
about 70° to 110°C and, after precipitation with ethanol,
refrigerated to a temperature of from about 0°C to about 20°C for
a period of time sufficient to precipitate a substantial
proportion of said protein from solution.
5. A method as described in Claim 3, wherein said protein is
extracted with sodium dodecyl sulfate at a temperature of from

about 70° to 100°C and, after precipitation with ethanol,
refrigerated to a temperature of from about 0°C to about 10°C for
a period of time sufficient to precipitate a substantial
proportion of said protein from solution.
6. A method as described in Claim 3, wherein said protein is
extracted with sodium dodecyl sulfate at a temperature of from
about 80° to 100°C and, after precipitation with ethanol,
refrigerated to a temperature of from about 0°C to about 10°C for
a period of time sufficient to precipitate a substantial
proportion of said protein from solution.
7. A method as described in Claim 3, wherein said protein is
extracted with sodium dodecyl sulfate at a temperature of from
about 90° to 100°C and, after precipitation with ethanol,
refrigerated to a temperature of from about 0°C to about 10°C for
a period of time sufficient to precipitate a substantial
proportion of said protein from solution.
8. A method as described in Claim 3, wherein said protein is
extracted with sodium dodecyl sulfate at a temperature of from
about 90° to 100°C and, after precipitation with ethanol,
refrigerated to a temperature of from about 2°C to about 8°C for a
period of time sufficient to precipitate a substantial proportion
of said protein from solution.

9. A method as described in Claim 3, wherein said protein is
extracted with sodium dodecyl sulfate at a temperature of from
about 90° to 100°C and, after precipitation with ethanol,
refrigerated to a temperature of from about 4°C to about 6°C for a
period of time sufficient to precipitate a substantial proportion
of said protein from solution.
10. A method as described in Claim 3, wherein said protein is
extracted with sodium dodecyl sulfate at about 100°C and, after
precipitation with ethanol, refrigerated to about 4°C for a period
of time sufficient to precipitate a substantial proportion of said
protein from solution.
11

Description

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The present invention relates to the field of processing
of brewery waste into useful products.
The principal by-product of the brewing industry is
brewer's spent grain (hereinafter referred to as BSG). The
composition of BSG is approximately as follows:
Table A
Component% (dry weight basis)
Moisture 7.41
Crude Protein 26.88
10 Crude Fat 8.07
Ash 4.71
Fiber 16.25
Nitrogen Free Extract 44.09
It will be seen, therefore, that protein is a major
constituent of BSG, and potentially a rich source of food.
Several proposals have been made in the past for recovery
of this protein. For instance, in The Molson Companies Limited's
U.S. Patent No. 4,315,038, dated February 9, 1982, it is disclosed
that protein can be extracted from trub by extraction with an
azeotropic mixture of isopropanol and water. In an article by
three of the present inventors (Crowe, Alli and Baker) in the
Journal of the Institute of Brewing, Vol. 91, p.l48-150, titled
Solubilization of Nitrogenous Constituents of Brewer's Spent
Grains, it is disclosed that up to 50% of the Nitrogen from BSG
solubilized by an acid detergent (cetyl-trimethyl ammonium bromide
in sulfuric acid - capable of solubilizing 90~ of BSG nitrogen)
can be recovered as a solid.
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The object of the present invention is to provide a
fairly inexpensive but efficient method of preparing a protein
concentrate from BSG.
In one broad aspect, the present invention relates to a
method of preparing protein concentrate from brewer's spent grain
comprising extracting said brewer's spent grain with sodium
dodecyl sulfate to solubilize the protein thereof, and thereafter
removing a substantial proportion of the protein in solution.
It has been discovered by the present invento~s that
sodium dodecyl sulfate (SDS) can be used as an inexpensive
extractant for BSG, with very good results. The extracted protein
is precipitated by the addition of ethanol followed by
refrigeration. It will be appreciated that other methods for the
isolation of the protein from the extract, such as those
involving, for instance, the use of a protein precipitant,
ultrafiltration, or adjustment of pH, may be used.
The practice of the present invention will be apparent
from the detailed comparative examples which follow, and which are
set out in Table B, following.
~periment 1
Commercially dried BSG (5g) was mixed with extractant
(lOOmL - 3% SDS - 0,5% Na2HP04; pH7,0). The mixture was heated
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under reflux for one hour. The residue was removed by filtration
(California Buchner unnels). Analysis of the extract showed that
62% of the BSG nitrogen was solubilized). The extract was cooled
to 4C and maintained at that temperature for 16 hours. The
precipitates were recovered by centrifugation (9500g, 0C), washed
with ethanol (95%; 20mL), centrifuged to remove the wash (12,500g;
0C) and lyophilized. Nitrogen analysis of the lyophilized
product indicated that 5% of the BSG crude protein was recovered.
Experiment 2
BSG was extracted with SDS solution under the conditions
used in Experiment 1. The reaction of the extract was adjusted to
pH2.0 using dilute HCl. The protein was recovered by
centrifugation, washed, and lyophilized as described in Experiment
1. Nitrogen analysis of the lyophilized product indicated that 2%
of the BSG crude protein was recovered.
~periment 3
BSG was extracted with SDS solution under the conditions
used in Experiment 1. The reaction of the extract was adjusted to
pH 2.0 using dilute HCl and the resultant mixture was cooled to
4C and maintained at this temperature for 16 hours. The protein
was recovered by centrifugation, washed, and lyophilized as
described in Experiment 1. Nitrogen analysis of the lyophilized
product indicated that 3% of the BSG crude protein was recovered.

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Experiment 4
BSG was extracted with SDS solution under the conditions
used in Experiment 1. Ethanol was added to the extract (70mL;
95~). The resultant precipitate was recovered by centrifugation,
washed and lyophilized as described in Experiment 1. Nitrogen
analysis of the lyophilized product indicated that 29% of the BSG
crude protein was recovered.
Experiment 5
BSG was extracted with SDS solution under the conditions
used in Experiment 1. Ethanol was added to the extract (70mL;
95%) and the resultant mixture was cooled to 4C and maintained at
this temperature for 16 hours. The resultant precipitate was
recovered by centrifugation, washed, and lyophilized as described
in Experiment 1. Nitrogen analysis of the lyophilized product
indicated that 44% of the BSG crude protein was recovered.
Experiment 6
BSG was extracted with the SDS solution as described in
Experiment 1 except that the extraction was conducted at 27C and
with agitation. Analysis of the extract showed that 29% of the
BSG nitrogen was solubilized. The protein in the extract was
recovered as described in Experiment 5. ~itrogen analysis of the
lyophilized product indicated that 16% of the BSG crude protein
was recovered.

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Experiment 7
Experiment 6 was repeated except that the extraction was
performed at 45C. Nitrogen analysis indicated that 33% of the
BSG nitrogen was extracted and that 18% of the BSG crude protein
was recovered.
Experiment 8
Experiment 6 was repeated except that the extraction was
performed at 60C. Nitrogen analysis indicated that 30% of the
BSG nitrogen was extracted and that 17~ of the BSG crude protein
was recovered.
Experiment 9
Experiment 6 was repeated except that the extraction was
performed at 75C. Nitrogen analysis indicated that 35% of the
BSG nitrogen was extracted and that 22% of the BSG crude protein
was recovered.
Experiment 10
Experiment 6 was repeated except that the extraction was
performed at 90C. Nitrogen analysis indicated that 51~ of the
BSG nitrogen was extracted and that 28% of the BSG crude protein
was recovered.
Experiment 11
The SDS extraction was conducted under the refluxing
conditions described in Experiment 1. The extracts were stored at

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4C for 16 hours. The cold extracts were centrifuged ~9500g; 0C)
to remove the precipitated material. The proteins in the
supernatant were concentrated by ultrafiltration and the retentate
was lyophilized. Nitrogen analysis of the lyophilized product
indicated that 47% of the BSG crude protein was recovered.
The procedure described in Experiment 5 gave a protein
recovery of 44%. The product which was isolated contained 9
nitrogen or 53% protein (%N x 5.83 See: Methods of Protein
Analysis (1984) I. Kerese ed. p.59, published by Ellis Horwood
Limited, Chichester, England). The proteinaceous material was
brown in colour and granular in texture. It will be understood
that the Applicant did not attempt to differentiate between
nitrogen from protein and from other sources, such as nucleic
acids. However, amino acid analysis of the protein concentrates
clearly indicates that they are proteinaceous materials.
The procedure described in Experiment ll gave a protein
recovery of 47%. The product which was isolated contained 6%
nitrogen or 35% protein (%N x 5.83). The proteinaceous material
was beige in colour and floury in texture.
It is to be understood that the examples described
above are not meant to limit the scope of the present invention.
It is expected that numerous variants will be obvious to the
person skilled in the art, without any departure from the
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spirit of the present invention. The appended claims, properly
construed, form the only limitation upon the scope of the
present invention

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