ABSTRACT
There is limited information on the quality of sorghum malt produced commercially at the high temperature of 30oC. This study investigated and compared wort properties of a Nigerian grown sorghum malted in the industry and malted in the laboratory. Total of 6 kg of sorghum sample used in this study was supplied by the Nigerian Breweries PLC., Aba plant. The methods of analysis of the Institute of Brewing (IOB), 1997 and Laboratory Methods in malting of International Centre for Brewing and Distilling (ICBD) were used to analyze all the parameters of the specific objectives. Variable results with similar patterns were observed on germinated sorghum malt from Nigerian Breweries Plc. Laboratory, and ranged as follows: moisture content (6.02 – 7.83%), diastatic power (23.76 - 43.32oWK), and α-amylase (38.98 - 43.88 DU) and β-amylase (29.2–34.77oL) whereas from Herriot-Watt University Laboratory, the moisture content (6.26 – 7.88%), diastatic power (23.83 - 43.72oWK), and α-amylase (40.1 – 44.0 DU) and β-amylase (30.4 – 35.1oL) were recorded. High values of α and β-amylases were enhanced at the higher temperature of 30°C except moisture content which was at 26 °C. Highest results observed by comparing laboratory made sorghum malt to commercial made sorghum malt included HWE (294 and 288 Lo/Kg) at 28oC on day 5, FAN (162 and 142 mg/L) at 28oC on day 5 and TSN (0.62 and 0.62 %) at 30oC on day 6, showed that optimum malting days is best at 5days at 280C. In analyzes for HWE and FAN, laboratory malted sorghum using a non-conventional mashing method-decantation mashing showed higher values with stronger correlation more than conventional mashing method-infusion mashing method when compared to industrially produced sorghum malt except for TSN values. These results have shown that sorghum malt can yield enough extract when compared to barley by applying this non-conventional decantation mashing method.
TABLE OF CONTENTS
Title Page i
Certification ii
Dedication iii
Declaration iv
Acknowledgements
v
Table of Contents
vii
List of Tables xi
List of Figure
xii
Abstract xiii
1.0 CHAPTER 1: INTRODUCTION
1
1.1 Background of
Study 1
1.2 Problem Statement
3
1.3 Justification of
This Research
4
1.4 Aims and Objectives 5
2.0 CHAPTER 2:
LITERATURE REVIEW 6
2.1 Sorghum: Classification and Distribution 6
2.2 Structure
of Sorghum Grain 7
2.3 Historical Use of Sorghum
in Beer Production 9
2.4 Malting
and Brewing Processes 11
2.4.1 Malt and malting 11
2.5 Sorghum Malting Process
12
2.5.1 Steeping 14
2.5.2 Germination 17
2.5.3 Kilning
20
2.5.4 Milling
21
2.5.5 Mashing 26
2.6 Enzymes in Malted Sorghum 29
2.7 Use of Sorghum Malt in Modern Beer Brewing 33
2.7.1 Generation of enzyme by sorghum malts 33
2.7.2 Extract yields 34
2.7.3 Fermentable sugars 35
2.7.4 Physiological differences of sorghum and
barley in relation to malting 36
2.7.5
Protein content, grain hydration 36
2.7.6 Malting
response
38
2.7.7 Location of enzymes 38
2.7.8 Enzyme development and soluble carbohydrate
and protein-extract
recovery
in sorghum malt 39
3.0 CHAPTER 3: MATERIALS AND METHODS 41
3.1 Grain/Malt
Samples
41
3.2 Study Site 41
3.3 Analysis of the Malt Grain 41
3.3.1 Cleaning and sorting of grains for malting 42
3.3.2 Determination of mold contamination and
weevil infestation 42
3.3.3 Determination of moisture content of the
grains 42
3.3.4
Germinative energy 43
3.3.5
Germinative capacity
44
3.4 Malting of the grains 44
3.4.1 Laboratory malting of sorghum 45
3.4.1.1
Steeping 45
3.4.1.2 Germination of the grain samples 45
3.4.1.3 Kilning/drying of germinated grains 45
3.5.
Analysis of Malt Samples 46
3.5.1 Amylase enzyme extraction assay 46
3.5.2 Diastatic power of sorghum malt 48
3.5.3 Moisture content of sorghum malt 49
3.6. Mashing of the Sorghum Samples
49
3.6.1 Decantation mashing 49
3.6.2 Infusion mashing 50
3.7 Extract
Determination 51
3.7.1 Determination of hot water extract (HWE) of sorghum malt 51
3.7.1.1 Determination of specific gravity 51
3.7.1.2 Anton parr density meter
52
3.7.2 Determination of total soluble nitrogen
(TSN) 53
3.7.3 Determination of free alpha amino nitrogen (FAN) 54
3.8 Statistical
Analysis 55
4.0 CHAPTER 4: RESULTS AND DISCUSSION 56
4.1 Analysis
of Raw Sorghum Grains Studied 56
4.2 Enzyme Assay, Moisture Content and Diastatic Power Analyses on Malted
Sorghum
Grain. 59
4.2.1 Analysis of malted sorghum
grain in Nigerian Breweries Plc.
laboratory 59
4.2.2 Analysis of malted sorghum grain in Herriot-Watt University
laboratory 61
4.3
Extract
Determination
63
4.3.1 Germination at 26oC – hot
water extract (HWE) 64
4.3.2 Germination at 28oC – hot
water extract (HWE) 65
4.3.3 Germination
at 30oC – hot water
extract (HWE) 67
4.3.4 Relationship between HWE
obtained from laboratory and industry malted
sorghum 69
4.4 Total Soluble
Nitrogen (TSN)
72
4.4.1
Germination at 26oC – total soluble nitrogen (TSN) 72
4.4.2 Germination at 28oC and 30oC–
total soluble nitrogen (TSN) 74
4.4.3 Relationship between TSN obtained from
laboratory and industry malted
sorghum 76
4.5 Free Amino
Nitrogen (FAN) 79
4.5.1
Germination at 26oC – free amino nitrogen (FAN) 79
4.5.2 Germination at 28oC and 30oC–
free amino nitrogen (FAN)
81
4.5.3
Relationship between TSN obtained from laboratory and industry malted sorghum
84
4.6 Discussion
87
5.0 CHAPTER
5: CONCLUSION AND CONTRIBUTION TO
KNOWLEDGE 95
5.1 Conclusion
95
5.2. Suggestions
for further research and contribution to knowledge 96
References
LIST OF TABLES
4.1 Results
of analysis of raw sorghum grains studied 57
4.2 Results
of analysis of sorghum malt – Nigerian Breweries Plc. Laboratory 60
4.3 Results of analysis of sorghum malt –
Herriot-Watt University Laboratory 62
4.4
Hot water
extract (Lo/Kg) of laboratory made sorghum malt (germination temperature of 26oC) compared to
commercial made sorghum malt 65
4.5 Hot water extract (Lo/Kg)
of laboratory made sorghum malt (germination temperature of 28oC)
compared to commercial made sorghum malt 66
4.6 Hot water extract (Lo/Kg) of laboratory made sorghum
malt (germination temperature of 30oC)
compared to commercial made sorghum malt 68
4.7 Total soluble nitrogen
(%) of laboratory made sorghum malt (germination temperature 26oC)
compared to commercial made sorghum
73
4.8 Total soluble nitrogen
(%) of laboratory made sorghum malt (germination temperature 28oC)
compared to commercial made sorghum malt 75
4.9 Total soluble nitrogen (%) of laboratory made sorghum malt
(germination temperature 30oC)
compared to commercial made sorghum malt 76
4.10 Free Amino Nitrogen (%) of laboratory made sorghum malt
(germination temperature 26oC)
compared to commercial made sorghum malt 80
4.11 Free
Amino Nitrogen (%) of laboratory made sorghum malt (germination temperature
28oC) compared to commercial made sorghum malt 82
4.12 Free
Amino Nitrogen (%) of laboratory made sorghum malt (germination temperature
30oC) compared to commercial made sorghum malt 83
LIST
OF FIGURES
2.1
Diagram of a sorghum kernel. 9
2.2 Schematic
diagram of wort production 13
2.3 Brewing process of western beers – Procédé de brassage des
bièresoccidentales 17
2.4 Diagram
of unmalted and malted grain sorghum – this study 32
4.5 Germination test for sorghum used in this study 58
4.6 Correlation between HWE of wort made from laboratory
sorghum malt
made at 26oC, 28oC
and 30oC – decantation Vs infusion mashing 70
4.7 Correlation between HWE of wort made from industrial
sorghum malt
made at 26oC, 28oC
and 30oC – decantation Vs infusion mashing 74
4.8 Correlation between TSN of wort made from laboratory sorghum malt
made at 26oC, 28oC
and 30oC – decantation Vs infusion mashing 77
4.9 Correlation between TSN
of wort made from industrial sorghum malt made
at 26oC, 28oC
and 30oC – decantation Vs infusion mashing 82
4.10 Correlation between FAN
of wort made from laboratory sorghum malt
made at 26oC, 28oC
and 30oC – decantation Vs infusion mashing 85
4.11 Correlation between FAN of
wort made from industrial sorghum malt
made at 26oC, 28oC and 30oC
– decantation Vs infusion mashing 86
CHAPTER
1
INTRODUCTION
1.1 BACKGROUND
STUDY
Sorghum (Great Millet), which is an
indigenous African cereal produced mainly in the savannah and grassland areas,
prevailing over most of the African continent originated primarily in Ethiopia
some 5,000 years ago (Obilana, 1985). Sorghum, like rice and barley, belongs to
the grass family- the Gramineae and
to the subfamily- the Panicoideae (Mutegi et al., 2010). Sorghum has a
great advantage by being both drought and heat tolerant, and is especially
important in arid regions and other parts of the world that is regarded in some
quarters as getting hotter (Akintayo and Sedgo, 2001; Bayode et al., 2011).
According to Nasidi et
al., (2010), “sorghum, is the 5th most important cereal
globally and 2nd in Africa. It is a staple food source to over 500 million
people and is cultivated in over 45million hectares of farmland worldwide. The
global sorghum production is estimated at over 60 million metric tons annually,
where Nigeria is
ranked among the top 3 largest sorghum producing countries in the world”. Over 10,000 cultivars of
Sorghum are available, and more are being developed of desired grain quality
(Haln, 1966). However, the two most important species are Sorghum bicolor
(L). Moench and Sorghum vulgare cv Farafara (Agu and Palmer, 1998).
Sorghum as a world food grain is ranked fifth important stable cereal and was
considered drought resistant crop (Dlamini et
al., 2007; FAO, 2006; Raihanatu et
al., 2011). It has been utilized for porridge, beer, unleavened bread,
couscous composite blends and ethnic beverages (Taylor et al., 2006).
Sorghum has, however, gradually become
very important as a source of raw material not only in brewing (Ezeogu et al., 2005); it is a principal source
of energy, protein, minerals including trace component like zinc, and iron in
diet for Africa and Indian population (FAO 2006; Mohammed et al., 2011). Besides these nutrients, sorghum also contains high
amount of phenolic acid, flavonoid, antioxidant, and condensed tannin (Awika
and Rooney, 2004; Dykes and Rooney, 2007). It is also the third largest cereal
crop in the United States of America, where it finds wide application in animal
feed production (Rooney et al., 1986).
Although sorghum grain has always been a
potential source of industrial brewing material, it was not until World War II,
when brewing materials were scarce, followed by extensive discussion in 1943 on
brewing with sorghum, that sorghum was offered as a brewing adjunct (Haln,
1966). The ban on importation of barley malt in 1988 due to high consumption of
foreign exchange led to a major change in brewing industry in Nigeria (Aloh et al., 1998). This resulted in the use
of locally available cereals, such as millet (Taylor and Dewar, 1994) and
sorghum, which emerged as the grain of choice for brewing in Nigeria (Aloh and
Agu, 2010; Agu et al., 2015).
Notwithstanding that Sorghum has been used
for centuries to brew traditional (opaque) beer in Africa (Ogundiwin and
Tehinse, 1981), in recent times Sorghum beer brewing has developed into a major
industry. Studies on sorghum are progressing rapidly and making a great impact
in the brewing industry, especially in brewing gluten-free beers for sufferers
of coeliac disease. As a result of extensive studies on sorghum malting, it was
suggested that a malting temperature of 30oC produced commercially
acceptable sorghum malt (Aloh, et al.,
2004). However, this high malting temperature for Sorghum has been reported to
facilitate the growth of afla-toxin producing Aspergillus flavus.
Nevertheless, earlier studies showed that microbial growth during the malting
of sorghum could be controlled (Agu and Palmer, 1998).
There is limited information on the
quality of sorghum malt produced commercially at the high temperature of 30oC.
Therefore, this study will investigate sorghum malt produced industrially from
Nigerian Breweries PLC malting plant and malts made in the laboratory in Nigeria
(where malting temperature is difficult to control) from the same sample
sorghum at different malting temperatures.
1.2 PROBLEM STATEMENT
Beer is one of the
most cereal-based beverages that are consumed on daily bases from cereals in
Africa and in Nigeria. This is due to the role beer fulfills in the social life
of Nigerian. The ban on importation of
barley malt in January 1988 due to high consumption of foreign exchange led to
a major shift in brewing industry in Nigeria. This resulted in the use of locally
available cereals for brewing. Sorghum is, however, the widely accepted cereal
in use where barley malt is not readily available. The extract yield during
mashing, the amount of soluble and fermentable materials, success in mashing,
rate of saccharification, etc. will depend on many factors. Research has shown
that the tropical nature of sorghum and the recommended malting temperature of
30oC will complicate matters if adequate control is not applied
during the malting of sorghum (Agu and Palmer, 1997b). There is therefore the
need to assess the quality of sorghum malt produced in the industry and that
made in the laboratory in a tropical country like Nigeria.
1.3 JUSTIFICATION OF THIS RESEARCH
The commercial value of sorghum is
shifting from a staple food source for humans to raw material for industrial
production of European type lager beer (Palmer et al., 1989). Although sorghum grain has always been a potential
source of industrial brewing material in Nigeria, it was assumed that the way
forward was to use commercial enzymes when brewing with sorghum grains (Agu,
2005). Commercial enzymes are very expensive, and it has been shown that
sorghum, when adequately malted will produce good quality malt. In this study,
the same sorghum variety malted industrially by Nigerian Breweries PLC malting
company, was used and another malted in the laboratory. Results obtained from
the study will highlight areas of disagreement from the analyses of
industrially and laboratory malted sorghum. The results will provide important
information for the industrial malting plant in Nigeria and their effect on
beer quality and cost.
1.4 AIM AND OBJECTIVES
1.4.1 Specific Aims
The Specific aim of this Research work is to compare
the Wort properties of a Nigerian grown Sorghum malted in the Industry and in
the Laboratory.
The objective of this research work is to study
the malting properties of Sorghum
1.4.2 Specific
Objective
1. To
determine the physical appearance and moisture content of the raw sorghum grain
sample
2. To
determine the germinative energy and germinative capacity of the raw sorghum
grain sample
3. To
assay for the amylases (α-amylase and
β-amylase) development of the
laboratory malted sorghum malt and the industrial sorghum malt, respectively
4. To
compare the Hot Water Extract (HWE) of the laboratory made sorghum at different
temperatures and the industrially malted sorghum using decantation and infusion
mashing methods
5. To
compare the Total Soluble Nitrogen (TSN) of laboratory made sorghum malt at
different germination temperatures to industrially made malt
6. To
compare the Total Free Amino Nitrogen (FAN) in the Hot Water Extract of
laboratory made malt at different germination temperatures to industrially made
sorghum malt.
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