Spent Grain Snacks

Specialist
article.
Dr.-Ing. Christoph Schill
Spent Grain – a valuable raw material for a high fiber
food snack
Value-added products in Brewing by Cooking Extrusion
Dr.-Ing. Christoph Schill
Process Engineer Extruded Products
Dipl.-Ing. Konrad Munz
Senior Process Engineer Extruded Products
Bühler AG
Pasta & Extruded Products
CH – 9240 Uzwil
Bühler AG
Pasta & Extruded Products
CH – 9240 Uzwil
[email protected]
[email protected]
Uzwil, June 2013
Bühler AG
Business unit Pasta & Extruded Products
CH-9240 Uzwil
T +41 71 955 11 11
F +41 71 955 33 88
[email protected]
www.buhlergroup.com
Spent grains are the main by-product in the brewing industry. The present
practical study shows the incorporation of spent grains into indirect expanded
cereals. Fermentation and cooking extrusion are the key factors for a high-fiber
cereal with a very high customer acceptance.
Keywords: Spent grains, fermentation, cooking extrusion, indirect expanded
breakfast cereals
By-products are continuously produced during food manufacturing. Brewing beer
is not an exception in this point.
In today’s world, brewers are also challenged by keeping the bottom line costs
low and searching for attractive ways to increase the efficiency of their processes
and to get more value out of their processes.
Using by-products out of the brew process and transforming them into valueadded products gives a huge opportunity to meet these objectives, in terms of
economic consideration, practical considerations, and potential for innovative
product design. Cook [1] mentions that 30 billion kilograms of spent grains are
generated each year – a huge potential for food innovations.
Harvesting and cleaning of barley and other cereal grains are the starting point in
the brewing process. The germination of the grain starts, when they are steeped
in water at a controlled environment (temperature and time). Malt is the result
after stopping this germination process by heating, when reaching the required
ratio of starch, protein, and enzymes. The intermediate product malt is milled and
mixed up with hot water. Enzymes transfer the malt’s insoluble starches into
fermentable sugars within a certain time. One gets a sweet malt extract (also
known as sweet wort) at the end of this enzymatic fermentation. Spent grains are
the solid residue left after the malt extraction and the separation from the liquid.
Hops are added to the sweet wort (malt extract) regarding flavoring reasons.
After filtering, addition of yeast and fermentation the malt extract turns now into
beer.
Removing all the sugars from the grain, the spent grains are a by-product high in
proteins, fibers, and vitamins as well as minerals. The protein and fiber contents
account generally for 20 – 70 % of its composition [2]. Thus spent grains fulfill
perfectly the above mentioned requirements for a valued-added food ingredient.
Beer is foodstuff, so the spent grains have also the quality of food. Does it make
sense to consider the Good Manufacturing Practice (GMP) for an ingredient,
which is traditionally used as animal feed, landfill, or composting material [2]?
If it is good enough for animals to eat, why not feeding mankind, who is searching
for a healthy and well-balanced diet?
High-fiber cereals based on spent grains are the response on that question!
Cooking Extrusion – Technology with high Potential
Burtea [3] defines extrusion technology as a process, which combines continuous
mixing, kneading and expulsion of moistened starchy and/ or proteinaceous
materials through dies by enough pressure.
But a cooking extruder (Figure 1) is a real miracle of technology. He combines all
these single unit operations in only one piece of equipment.
© Bühler AG, CH-9240 Uzwil
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Figure 1: PiloTwin BCTL-42, Ø 42 [mm], co-rotating twin screw extruder, L/D =
28, Bühler AG (CH)
Regarding all possible parameters, which can influence the extrusion process,
only four main parameters determine the final product quality: moisture content,
specific mechanical energy (SME), specific thermal energy (STE), and retention
time. The product quality may be expressed in terms of final moisture content,
expansion, texture, color, or flavor.
During extrusion, raw materials are exposed to heat and shear stress for a very
short time allowing new starch and protein interactions. [4] states that molecules
realign and interact to form matrices as a result of starch gelatinization and
protein denaturation. The screws enable a continuous process and promote the
conveyance, heating, melting and mixing the material throughout the barrel.
The use of twin-screw extruders for food processing in an industrial scale started
in the 1970s, with an expanding number of applications in the 1980s, because of
the benefits extrusion technology offers: versatility, costs, productivity, product
quality, and environmentally-friendly. [5]
The extruder is the preferred technique to realize different products with distinct
product characteristics, quality aspects as well as complexities and/ or
challenges. In a commercial scale expanded corn snacks and breakfast cereals,
pet food, and meat analogs are processed by extrusion technology. [6]
High-fiber Cereals – Product with high Potential
High-fiber cereals and snacks gain increased interest in the food industry. The
dietary benefits of this type of food are outstanding and well documented.
According to recent research a high fiber diet benefits the heart, lowers the risk of
blocked arteries, heart attacks and strokes. Cholesterol, blood sugar and insulin
levels can be lowered as well. In addition to reducing the risk of certain chronic
diseases high fiber diets fill the stomach and thereby reduce the appetite. Thus
high fiber diets protect against obesity. [7]
The problems with such ingredients are that they often lack pleasant taste or
mouth feel when eaten or the unattractive product color.
The Bühler AG (Uzwil, Switzerland) has investigated different extrusion setups,
processing technologies, and product shapes concerning extruded spent
brewers’ grains to overcome the prementioned restrictions.
The following specialist article shortly represents the possibilities to generate
value-added products out of process by-products by the help of a modern
extrusion system.
We see a very high potential in the wet treatment of spent grains to transfer them
into added-value products. The key elements for this process are fermentation
and cooking extrusion of spent grains.
© Bühler AG, CH-9240 Uzwil
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Fermentation and Cooking Extrusion – Process with high Potential
In the following, the setup and the results of the carried out study are shortly
presented in the following chapters.
Recipes and Raw Materials
In this feasibility study two different recipes are conducted. The formulas are
shown in the following table 1.
Table 1: Used formulas
Formulation
[%]
Moisture Content
[%]
Formula 1
Spent grains
Rye flour
Salt
TOTAL
38.4
60.2
1.4
100
75
12
5
36
Formula 2
Spent grains
Rice flour
Rye flour
Sugar
Salt
TOTAL
36.5
31.4
26.2
4.9
5
100
75
12
12
5
5
34
Spent grains used in this study are locally purchased (Koni’s home brewery) and
represent a mixture out of three different batches. The mixtures consist of 85 % of
malted barley and 15 % of residues from corn, sorghum, and oat. The final
moisture content is 75 %. Coarse grist from rolled malt is present. The spent
grains are fermented by a lactic acid culture. In the following, regarding the coarse
grist, the slightly sweet, malty tasted raw material is fine ground to a length of
approx. 1 mm by the colloid mill.
The commercial rye and rice flour are provided from a local.
The minor ingredients salt and sugar are considered of marketable quality.
All ingredients of the recipes are mixed up in a standard bakery mixer and fed
directly into the extruder by a volumetric feeder.
The actual measured moisture content of the powder mixes are 37 % (Formula 1)
and 33 % (Formula 2). Both formulas have a tendency for bridging at these
moisture contents.
Test Setup
The present practical study is carried out in Bühler’s application test center with a
co-rotating twin screw extruder (PiloTwin BCTM-30, Ø 30 [mm], L/D = 28 (Bühler,
Switzerland)), which is shown in Figure 2. The barrels 2 – 4 are heated and the
two last barrels are cooled. The fifth barrel shows a venting spout.
Two different dies are considered in this study, one for small, one for large flakes.
A standard screw configuration for high SME input at lower screw speed is
used for both formulas.
© Bühler AG, CH-9240 Uzwil
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Figure 2: PiloTwin BCTM-30
The extruded pellets are directly transported to a flaker mill (PolyFloc BCFA-508,
(Bühler, Switzerland)). The flaked pellets are collected and dried for 5 min at 85 –
90 °C and stored at ambient conditions. After storing a final toasting step is
conducted for 30 s at 250 °C.
Results
Formula 1 provides a fairly good product. The indirect expanded flakes show a
soft crunchy texture, but the salt content is too high. The expansion may be
better. The expansion degree can be improved by replacing the rye flour with
another starchy material. A predominant “bread crust” flavor lowers the customer
acceptability.
Formula 2, with a reduced salt content, sugar addition, and the rye flour
replacement by rice flour, enables a product with excellent customer
acceptability. The expansion is improved, texture is better, so that these products
are fairly comparable to traditional corn flakes.
The final product, made with this formula, is presented in the following figure 3.
Figure 3: Indirect expanded flakes with spent grain addition (Formula 2)
The bulk densities of the second trial series range between 180 – 200 g/l.
What the Future holds – Developments with high Potential
Based on the presented results several ideas for future developments are
popping up.
What about high-fiber, no sugar flakes?
It is possible, first trials have already shown that fresh and active brewers’ grains
can be mixed up with gelatinized flours. Regarding the enzymatic activity the
ingredients are turning into a liquid. Of course, this liquid is high-viscous, sticky,
but most important, it is sweet. So it is imaginable making high-fiber flakes with a
© Bühler AG, CH-9240 Uzwil
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sweet, malty taste without any addition of sugar. This future product may be
declared as “high-fiber flakes”, “no sugar added”, and “containing spent grains”.
But what is the best solution for using spent grains? Cook [1] has already asked
what the best option is when it comes to use of brewers’ grains in the brewing
industry: maintain the status quo, which means animal feed or landfill, or innovate
and develop new solutions, which includes energy source, bio refineries, or novel
food ingredients/ applications?
He sees the answer on this question in acting locally. Each brewery has to find its
own way.
A future production process for the presented product may be as follow. Wet
spent brewers’ grains are received and the fermentation is immediately started.
This mass can be dosed into a grinding system. The fermented and ground mass
is directly fed into the extrusion system. The extruded pellets are pre-dried,
flaked, and toasted.
With the Bühler slogan “Innovation for a better World” Bühler engaged in new
ideas and supports customers to find solutions.
References
/1/ COOK, D.: Brewers’ Grains: Opportunities Abound. Brewer’s Guardian, Vol. Nov./ Dec. (2011), 60
– 63.
/2/ ACACIO, K. ET AL.: Introduction to Brewers’ spent grain.
http://share.iit.edu/bitstream/handle/10560/1935/AlternativeUsesForBrewers'SpentGrainIPRO340
Poster2Sp11.pdf?sequence=6, (Retrieved: 2013-06-06).
/3/ BURTEA, O.: Snack Foods from Formers and High-Shear Extruders. Lusas, E. W. & L. W. Rooney.
Snack Foods Processing. City, PA: Technomic Publishing Company, Inc., (2001), 281 - 314.
/4/ HARPER, J. M.: Extrusion of Foods. City, FL: CRC Press, Inc., Volume 1 (1981).
/5/ GUY, R.: Introduction. Mercier, Linko, Harper: Extrusion Cooking. (1998).
/6/ HARPER, J. M.: Food Extruders and their Applications. Mercier, Linko, Harper: Extrusion Cooking.
(1998).
/7/ YU, C. L.: High Fiber Diet Benefits. http://www.disabled-world.com/fitness/diets/fiber-dietbenefits.php, (Retrieved: 2013-06-06).
© Bühler AG, CH-9240 Uzwil
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