CETvol87
DOI: 10.3303/CET2187054
Paper Received: 9 September 2020; Revised: 8 March 2021; Accepted: 14 April 2021
Please cite this article as: Monteiro C.C., Sarache G., Januario J.G., Berwig K.P., Raniero G.Z., Monteiro A.R., Moreira da Silva F., 2021,
Biopolymer Based on Brewing Waste and Extruded Maize: Characterization and Application, Chemical Engineering Transactions, 87, 319-324
DOI:10.3303/CET2187054
CHEMICAL ENGINEERING TRANSACTIONS
VOL. 87, 2021
A publication of
The Italian Association
of Chemical Engineering
Online at www.cetjournal.it
Guest Editors: Laura Piazza, Mauro Moresi, Francesco Donsì
Copyright © 2021, AIDIC Servizi S.r.l.
ISBN 978-88-95608-85-3; ISSN 2283-9216
Biopolymer Based on Brewing Waste and Extruded Maize:
Characterization and Application
Claudia C. F. Monteiroa,*, Gabriel Saracheb, Jaqueline G. B. Januáriob, Kimberli P.
Berwigc, Ghiovani Z. Ranieroc, Antonio R. G. Monteiroc, Fernando Moreira da
Silvad
a
Department of Design, Universidade Estadual de Maringa (Brazil)
b
Department of Food Engineering, Universidade Estadual de Maringa (Brazil)
c
Post graduation program in Food Science, Universidade Estadual de Maringa (Brazil)
d
Faculdade de Arquitectura of Arcteture, Universidade de Lisboa (Portugal)
ccfmonteiro@uem.br
The brewing industry produces more than 100 billion litres a year worldwide and consequently more than 20
million ton of solid waste. This waste is mostly destined for animal feed; however, it ends up being a form of
disposal of low added value. On the other hand, furniture and decorations items of a bar can use such waste
for its confection, which adds value to the waste and mentions the own beer. This work aimed to develop and
characterize a biopolymer obtained from the brewing residue (milled malt after mashing process) and extruded
maize to be used as a raw material for furniture and in architectural wall coverings. The proportions of
components, time and temperature of the drying process and malt milling were variated in nine treatments.
The wood chipboard was used as a control as well. Tensile strength, young's modulus, and elongation at
break were analysed, water absorption index (WAI) and water solubility index (WSI) were determined, and the
colour was evaluated. After the material was characterised, the better mixtures were applied to make a board
used in furniture and wall coverings. The sensorial analysis (visual) was made with 117 non trained panellists
to evaluate the new material's acceptance to replace wood-based boards. The main results showed that lower
drying temperature, as well as the higher amount of extruded maize, could increase the resistance of the
material. There is no significant evidence that particle size affects the material's resistance; on the other hand,
it was essential to increase the material acceptability, the smaller was particle size, the better was the
acceptance as a substitute of wood-based boards. It was possible to conclude that the material has high
acceptance and adequate physical properties to be used in some furniture and covering walls. It is an
excellent alternative to increase the value of this industrial waste.
1. Introduction
Plastics are unique materials that fulfil a wide range of functions in society but harm the environment by
consuming resources (Wang and Wang, 2017). According to Rutiaga et al. (2005), conventional plastics are
obtained from synthetic polymers derived from petroleum and, for this reason, constitute an environmental
problem because their high stability can result in more than 100 years of degradation. The higher the global
plastic production level, the greater the CO2 and greenhouse gas (GHG) emissions. In this context, there are
several initiatives to minimise this problem, such as the one undertaken by the United Nations (UN), which has
sought to motivate the implementation of ecologically correct methods in all countries of the world (Oktavilia et
al., 2020).
Technologies have been applied to reuse agro-industrial by-products and, thereby, reduce their disposal,
adding value, and minimising environmental impacts (Saraiva et al., 2019). Cereal-based by-products can be
applied in the production of bio-based materials, for example, bio-based polyethene (bio-PE), bio-based
polyethene terephthalate (bio-PET), bio-based polyurethane (bio-PUR), polylactic acid (PLA), modified starch,
cellulose derivatives and polyhydroxyalkanoates (PHA). These compounds have high added value and
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transversal application in the industry, following a circular economy approach and minimal or zero waste
generation (Skendi et al., 2020).
Beer is a beverage widely consumed worldwide, made from water, malt, hops and yeast as primary
ingredients. The leading global countries in beer production are China, the United States and Brazil. According
to the Statistics Portal, beer production has increased in recent years, from 130 billion litres in 1998 to 191
billion litres in 2019 (STATISTA, 2020). Consequently, the waste generated by the brewing industry also
increased. The production of beer is characterised by a process that generates many residues (among them,
malt cake, brewer's yeast and trub), which have characteristics that make it possible, in many cases, to be
reused in other industrial processes (Marsarioli, 2019). In the last few decades, there has been a large
increase in the number of micro-breweries globally, adding value to the product. However, the waste from
these small factories generally does not have a correct destination, since as they are not large volumes in
each factory, there is usually no economic interest in this waste, so solutions for the disposal of this waste on
a smaller scale can be useful to reduce the environmental impact of this growing industrial sector and at the
same time add value to manufacturers (Monteiro et al., 2019).
The efficient management of these by-products aims to limit environmental pollution caused by their
elimination and make these by-products useful. Disposing of waste in an environmentally sustainable manner
is a critical challenge, with the development of viable processes for using or valorising brewery waste
(Rachwal et al., 2020). Some works have been using beer residues mixed with synthetic or natural resins to
produce biodegradable materials. However, these resins have a considerable environmental impact as well as
a high cost. On the other hand, corn is a source of starch, natural, cheap, renewable, and biodegradable, is an
attractive combination of availability and price. Thus, it is an excellent candidate to produce biodegradable
materials.
However, to obtain a material using starch, it is necessary to employ techniques to destroy the original
semicrystalline structure of its granules, which can be done by a combination of mechanical and thermal
energy. The resulting material is biodegradable and fully decomposable into non-toxic waste (Schlemmer et
al., 2014). Thus, maize must undergo an extrusion process for its pre-gelatinisation and thus act as a binding
agent in the material. From different sources, starch can be mixed, kept intact, used in various resins as filler
or melted to mix compounds. According to Justin et al. (2017), the extruded maize is made in a highly efficient
and low-cost material and energy consumptions.
Thermoplastic starch or plasticised starch offers an exciting alternative to synthetic polymers in specific
applications (Vroman and Tighzert, 2009). Significant research is carried out to develop a new class of totally
biodegradable "green" composites called biocomposites (Netravali and Chabba, 2003). Starch can be used as
a biodegradable polymeric compound. Degradation occurs by hydrolysis in the acetal bond by enzymes.
Amylases attack the α-1,4 bond while glycosidases attack the α-1,6 bond. Degradation products are non-toxic
(Vroman and Tighzert, 2009).
The traditional industrial production model (extraction, production, consumption and waste) has proved
unsustainable in the context of the current market, of technology, of the quest for conscious production. The
new way of thinking about production fits the circular economy concept, which proposes a behavioural change
in the way of consuming and using natural resources and waste. Important actions in this circular economy
scenario are the change in product design and consumption, in the process of raw materials and waste
exploitation and the conflicting action between environmental sustainability and economic growth (Cosenza,
2020).
The production of materials with the addition of industrial residues and reducing the environmental impacts
caused by the plastic industry and its chain can contribute significantly and add value and reduce these
industries' environmental impact. Therefore, this work aimed to develop and characterize a material produced
with beer residue and extruded maize.
2. Material and methods
2.1 Materials
To obtain ground and standardised beer residue, the used malt residue was supplied by a small local brewery
(Maringá, PR, Brazil). After the mashing process of a pure malt lager, the resulting residue was immediately
dried in an oven at 70 °C with air circulation for 48 hours, the grinding was done in a hammer mill and
separated into three different granulometry (3.5-6, 6-14, 14-28 mash) and later stored in polypropylene bags
until the moment of use.
Corn grits, used to obtain the milled corn extrudate, were provided by Nutrimilho (Maringá, PR, Brazil) and
extruded according to Monteiro et al. (2016) using IMBRA RX50 single screw equipment (INBRAMAQ,
Ribeirão Preto, SP, Brazil) with 50 mm diameter and 200 mm length. The die plate had two holes of 3 mm
diameter, and extrusion parameters were 20 A of motor amperage, a feed rate of 12 g.s-1 and a screw speed
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of 90 rpm. After the extrusion, the extrudates were ground, and the 60-80 mesh fraction was separated and
later stored in polypropylene bags until use.
2.2 Material production process
To prepare the biomaterial, beer residues were mixed with the extruded ground corn in the proportions and
granulometry shown in Table 1. Experimental design of material production, with 25 g of distilled water was
added and homogenised manually until a uniform mixture was obtained. Subsequently, the mixture was added
in a metallic tray 15 cm in diameter and pressed by a hydraulic press at 7 ton, and it results in a 40 kg/cm2
pressure for 300 seconds. The materials were then transferred to greenhouses at the respective temperatures
provided in the experimental design (next section) for 24 hours. Finally, the samples were conditioned in a
dryer for 48 hours before analysis.
2.2.1 Experimental design
The proportions of components, the temperature of the drying process and particle size of waste malt milled
were variated in eight treatments. It was made a central point in triplicate. Table 1 shows the experimental
design of material production.
Table 1: Experimental design of the material production process
Treatment Malt waste (g) Extruded maize (g) Dry temperature (ºC) Particle size of malt waste (mash)
T1 55 45 45 14-28
T2 55 45 45 3,5 – 6
T3 55 45 105 14-28
T4 55 45 105 3,5 – 6
T5 85 15 45 14-28
T6 85 15 45 3,5 – 6
T7 85 15 105 14-28
T8 85 15 105 3,5 – 6
T9 70 30 75 6 – 14
2.3 Material characterization
For the material characterisation, the sample was cut into specimens with 10 x 100 mm dimensions.
2.3.1 Density
Specimen’s thickness was determined using a digital micrometre (0.001 mm resolution, Mitutoyo, Japan). Five
points of each specimen area were evaluated, and the volume was calculated using the average thickness
with specimen dimension. The mass of specimens was evaluated in an analytical balance.
2.3.2 Tensile strength
The mechanical resistance was analysed using a Universal testing machine (model DL1000, EMIC, São José
dos Pinhais, Brazil). Each sample was loaded by 100 kgf at 1 mm*s-1, with probe angled at 135° and analysed
according to ASTM D1037-12 (ASTM, 2012), with some modifications.
2.3.3 Water absorption index (WAI)
The Water Absorption Index of the samples was evaluated according to Ayrilmis et al. (2009) with
modifications made by Monteiro (2019). To evaluate WAI, the specimens were dipped in water, fast dried, and
weighed (initial weight), immersed in distilled water (30:1 water/sample w/w) for 24 h at 25 °C, fast dried again
and weight (final weight). The WAI is calculating by the division of final weight by initial weight. The tests were
conducted in triplicate.
2.3.4 Colour
Colour was evaluated using a Minolta Chroma Meter CR‐400 colourimeter with D65 illuminate as the
reference, with readings in three-point each sample for each treatment. Results were expressed by the
CIELAB system, with values of L*, a* and b* whose L* values. The nine treatments were evaluated.
2.3.5 Acceptance
The materials' acceptability test was made in a virtual environment by 117 untrained testers (37 male and 80
females from 18 to 48 years old, mean 28 years old). The samples were photographed in a 56 Megapixels
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camera to make the appearance evaluation. All eight samples and three repetitions of the central point were
presented, coded with random numbers. To evaluate appearance's overall acceptability, the 11-point
structured hedonic scale was used, where 0 represented the minimum score 'disliked extremely' and 10, the
maximum score 'liked extremely'. The Research Ethics Committee approved these tests of the State
University of Maringa (CAAE 18718013.3.0000.0104).
2.3.6. Statistical analysis
All data were treated statistically from the analysis of variance (ANOVA) with subsequent analysis of the
Tukey tests' means at 5 % probability and correlation test. The statistical tests were made using software
Sisvar 5.6 (Ferreira, 2011).
3. Results and discussion
Table 2 presents the results obtained for density, mechanical resistance, and water resistance (WAI). The
results obtained for density and mechanical resistance show a significant correlation (Pearson, p-value=0.00)
between them (r=0.76). In this way, it is possible to affirm that the increase in density contributed positively to
the increase in resistance. However, it was not the only aspect that defined the resistance.
Table 2: Physical properties of the material
Treatment Particle size of
malt waste (mash)
Density (g.mL) Mechanical resistance (Kgf) WAI
T1 14-28 0.89ab 21.95b 2.69a
T2 3,5 – 6 0.94a 27.32a un
T3 14-28 0.85b 14.05c 1.64c
T4 3,5 – 6 0.72d 10.15d un
T5 14-28 0.82bc 5.37e 2.97a
T6 3,5 – 6 0.78c 10.75d un
T7 14-28 0.83bc 6.37e 2.18b
T8 3,5 – 6 0.65e 4.14e un
T91 6 – 14 0.79
c 10.81d un
T92 6 – 14 0.82
bc 10.13d un
T93 6 – 14 0.83
bc 10.67d un
Means with different letters in the same column are significantly different (P ≤ 0.05).
un – undetermined (the sample was completely dissolved)
Based on the statistical analysis of the data, it was possible to identify that the granulometry of the raw
material was not an important factor for increasing the resistance of the material, which differ from the work of
Mikalouski et al. (2014) which reported an influence of the granulometry in the expansion index of the
samples. On the other hand, the increase in extruded maize in the mixture has contributed positively to the
increase in the material's resistance.
Water absorption was not evaluated for seven samples because they were completely dissolved. For the other
four samples, the values are too high indicating that the material is not suitable for water-resistant functions.
Compared with the results found by Monteiro et al. (2019), the results are lower. Low water resistance is a
disadvantage compared to more resistant materials; however, this can be easily solved using a sealant to be
applied to the material after its production, if it requires waterproof resistance.
Table 3 presents the results of the material appearance analysis. The colour tests showed that the malt
residue's granulometry had little influence on colour. On the other hand, the increase of the proportion of
extruded corn in the mixture, as expected, increased the intensity of yellow in the sample. The drying
temperature was the factor that most interfered in the sample's staining, especially the samples that dried at
105 °C, as can also be seen in Figure 1. Figure 1 shows the appearance of the materials obtained in the eight
treatments, as well as the repetitions at the central point (T9).
T1 T2 T3 T4 T5 T6 T7 T8 T9
Figure 1: Appearance of material
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It was not possible to establish a relationship between the samples' instrumental colour parameters and
sensorial acceptance. By the sensorial acceptance of appearance, the materials produced with finer
granulometry (14/28) had significantly higher acceptance then the thicker granulometry (3.5 – 6). The drying
temperature also exerted influence in the evaluation of appearance.
Table 3: Appearance of material
Treatment Colour Sensorial acceptance
L a b
T1 50.34 (1.74) 2.36 (0.26) 24.78 (0.19) 7.16ab
T2 53.03 (2.71) 0.73 (0.23) 26.24 (1.86) 4.99c
T3 41.17 (0.94) 5.90 (0.76) 22.65 (0.32) 7.39a
T4 39.33 (0.78) 6.78 (0.59) 22.48 (1.56) 6.35b
T5 53.39 (1.55) 3.01 (0.46) 24.84 (0.07) 7.25ab
T6 53.58 (1.79) 1.29 (0.17) 24.34 (1.54) 5.89b
T7 41.25 (1.57) 6.72 (0.35) 23.49 (1.01) 7.83a
T8 40.92 (2.60) 7.47 (0.60) 25.41 (1.13) 7.01ab
T91 52.75 (1.06) 1.28 (0.42) 24.41 (1.96) 5.76
bc
T92 53.88 (1.76) 0.85 (0.33) 24.29 (0.87) 6.02
b
T93 55.46 (1.55) 1.14 (0.11) 25.00 (1.55) 6.23
b
Means with different letters in the same column are significantly different (P ≤ 0.05).
Although the T2 treatment had the best mechanical resistance, this treatment resulted in the worst acceptance
of appearance. However, the T1 sample, the second-best in mechanical resistance was also one of the best
samples in the appearance attribution. Thus, T1 and T3 samples' resistance can be considered adequate
simultaneously as these treatments provide good sensory acceptance of appearance.
The resistance of the materials produced in the T1, T2 and T3 treatments were significantly lower than those
found by Monteiro et al. (2019) up to 80.9 Kgf in the samples and 61.9 in the Medium Density Fiberboard
(MDF). However, the resistance is sufficient for the elaboration of some furniture and utensils that do not
require high mechanical resistance and application in wall coatings.
The low variability presented in the treatments T91 to T93 indicated the material's high reproducibility, and
even in the sensorial acceptance analysis, the values were within the same confidence interval.
4. Conclusions
Based on the results presented, the treatments with 55 % malt residue and 45 % extruded corn with more
acceptable grain size (14/28) showed good performance both in resistance and in sensorial acceptance in
appearance attribute. Thus, the sample T1 presented the best process parameters within the studied range,
resulting in a material with desirable characteristics. Although the material has a lower resistance than
materials in which the waste is mixed with resins, this resistance is sufficient for several applications. The
great advantage is represented by the much lower environmental impact than materials with resins as binding
agents.
So, this work showed that it is possible to produce a low-cost material, totally biodegradable, and could be
applied, in further research, to the construction of various utensils and architectural coatings.
Acknowledgements
The authors gratefully acknowledge the support from Brazilian National Council for Scientific and
Technological Development (CNPq) through the research project 303597/2018-6, the Portuguese Foundation
for Science and Technology (FCT), Research Centre for Architecture, Urbanism and Design (CiAUD) Faculty
of Architecture, University of Lisbon (FA/ULisboa) and Fundação Araucária de Apoio ao Desenvolvimento
Científico e Tecnológico do Paraná (FA).
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