Indigenous Fermented Foods for the Tropics

Indigenous Fermented Foods for the Tropics provides insights on fermented foods of the Tropics, particularly Africa, Asia and South America, highlighting key aspects and potential developments for these food products. Sections provide an overview on the production and composition (nutritional, physicochemical, health beneficial and microbiota) of these indigenous fermented foods in the tropics, innovative techniques for investigating the composition of these fermented food products and improvement of the fermentation process to yield better nutritional constituents, health beneficial components and sensory qualities, and safety aspects to be considered in fermented foods. Other sections provide insights into the packaging and marketing of these food products as well as future prospects of fermented foods in the tropics. This book provides new perspectives and recent information to complement existing texts on indigenous fermented foods serving as a valuable reference text for detailed insights into indigenous fermented foods of the tropics.

• Discusses fermented foods from the Africa, Asia, and South America based on the raw materials used
• Offers innovative techniques for improving these indigenous products and investigating their composition as well as upgrading traditional technologies used in the production of fermented products
• Covers the role of technology and innovations in the quest for enhancing quality, and safety of fermented foods as demand for fermented food and beverage products is increased

• Language: English
• Publisher: Academic Press
• Release date: Jan 21, 2023
• ISBN: 9780323985536

Book preview

Preface

Oluwafemi Ayodeji Adebo, Chiemela Enyinnaya Chinma, Adewale Olusegun Obadina, Antonio Gomes Soares, Sandeep Kumar Panda and Ren-You Gan

Fermentation is a microbial-driven food processing technique that can be considered as being traditional with its history dated back to over 10,000 years ago or more. It remains an affordable and vital processing technique in developing countries and the tropical regions of the world, leading to numerous available food and beverage products. Technologies for improving the process, crafting new products and/or ingredients from fermentation are continually evolving. Concerted efforts documented in the available literature are acknowledged, but there is still the need to provide an updated text on fermented food products in the tropics. This book titled "Indigenous Fermented Foods for the Tropics" provides a fresh perspective on fermented food products in three tropical regions of the world (Africa, Asia, and South America). As a single text, the book provides a comprehensive overview of the indigenous fermented products of these three tropical continents, innovative techniques for improving these indigenous products, and investigating their composition as well as safety concerns and challenges associated with these indigenous fermented foods. Marketing and packaging of these products are also discussed in the latter part of the text, with a chapter providing a future outlook for these indigenous fermented food products.

This book provides recent information and complement the existing books on indigenous fermented foods, especially those from Africa, Asia, and South America. This book will thus serve as a valuable reference material for both undergraduate and postgraduate students on knowledge about traditional food processing, particularly fermentation. The book will also benefit fermentation scientists, food microbiologists, public health scientists, biochemical engineers, nutritionists, and food scientists in various industries, catering, research institutes, and universities. It will also serve as a useful reference for individuals with an interest in indigenous foods as well as scientists and professionals involved in the research and development of fermented foods and beverages.

This book would not have been possible without the admirable effort of internationally renowned authors that contributed and reviewers who through their suggestions significantly improved the quality of the chapters in this book. We would like to express our gratitude for their expertise and time. We also acknowledge the Elsevier editorial team for their prompt response, assistance, and advice. We hope you enjoy reading this book and continue to contribute to knowledge for the benefit of mankind.

Chapter 1

An insight into indigenous fermented foods for the tropics

Oluwafemi Ayodeji Adebo¹∗, Chiemela Enyinnaya Chinma²,³, Adewale Olusegun Obadina³,⁴, Antonio Gomes Soares⁵, Sandeep Kumar Panda⁶ and Ren-You Gan⁷,    ¹Food Innovation Research Group, Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Gauteng, South Africa,    ²Department of Food Science and Technology, Federal University of Technology, Minna, Nigeria,    ³Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Gauteng, South Africa,    ⁴Department of Food Science and Technology, College of Food Sciences and Human Ecology, Federal University of Agriculture, Abeokuta, Nigeria,    ⁵Research Area on Postharvest of Fruits and Vegetables - Embrapa Food Technology, Rio de Janeiro, RJ, Brazil,    ⁶School of Biotechnology, Kalinga Institute of Industrial Technology (KIIT) Deemed to be University, Bhubaneswar, Odisha, India,    ⁷Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, P.R. China∗, Corresponding author. e-mail address: [e-mail]; [e-mail]

Abstract

Fermentation is the oldest form of biotechnology process borne out of the need to extend the keeping quality of food materials. These subsequently derived fermented food products are consumed daily, and the three major continents of the tropics (Africa, Asia, and South America) have the richest diversity of these food products in the globe. These fermented foods are vital to the survival of inhabitants of these regions, providing staples, used as adjuncts, part of diets, and also represent part of the culture and heritage of tropical nations. This chapter briefly provides an insight into these food products available in Africa, Asia, and South America, with a description of the contents of the different sections in the book.

Keywords

Indigenous foods; fermented foods and beverages; tropics; fermentation; Asian foods; African foods; South American foods

1.1 Introduction

The importance of fermented foods cannot be overemphasized. Fermentation, being one of the traditional food processing techniques that have been in existence since medieval times, has brought about the production of subsequently derived food items that have sustained livelihoods and contributed to human diet (Adebo et al., 2021). Fermentation of foods, particularly bread, has been associated with the transition from hunter–gatherer communities to sessile agricultural communities in the Neolithic revolution about 14,000 years ago (Arranz-Otaegui et al., 2018; Hayden et al., 2013; Paul Ross et al., 2002) opined that fermentation was primarily used as a food preservation technique and this can be traced back to thousands of years ago Fig. 1.1, when the art of cheese making was developed in the fertile crescent between Tigris and the Euphrates rivers in Iraq. Such preservative effects make fermentation one of the most effective food preservation techniques due to the formation of organic acids, reduced pH, production of alcohols, bacteriocins as well as antimicrobial end products that help mitigate against pathogenic and spoilage microorganisms (Adebiyi et al., 2018; Paul Ross et al., 2002).

Figure 1.1 Major events in food fermentation and preservation through the years (Paul Ross et al., 2002).

Fermentation can be simply defined as an intentional process performed to transform substrates into new products through the action of microorganisms (Kewuyemi et al., 2020). A more recently adopted definition by the International Scientific Association for Probiotics and Prebiotics defines fermented foods as foods made through desired microbial growth and enzymatic conversions of food components (Marco et al., 2021). Fermented foods have been an increasingly popular food category, with an estimate suggesting that the global fermented food and ingredients market size would reach a projected US$ 59 billion by 2026 2021). According to (Tamang et al., 2016), there are over 5000 varieties of fermented food products produced and consumed in different regions of the world. While other regions of the world equally have fermented products, the tropics (Africa, Asia and South America) seem to have more diversified products, with a relatively lesser number of them documented in the literature.

The occurrence of different fermented foods in specific regions and countries of the world is associated with the dietary habits, cultures, availability, as well as accessibility to raw produce. Equally important are cultural, socioeconomic factors, ethnicity, religion, and race, all of which play significant roles in the choice of fermented product in each country and continent (Hesseltine & Wang, 1980; Tamang et al., 2020). Cereals, legumes, roots and tubers, as well as dairy-based products are majorly consumed in Africa Table 1.1, with roots and tubers being the main fermented products in South America Table 1.2. On the contrary, legumes, cereals, vegetables, as well as fish- and meat-based fermented products dominate most parts of the Asian continent Table 1.3.

Table 1.1

Table 1.2

Table 1.3

The significance of these products in contributing to the diet of the tropics is topical, considering the relatively lesser income and socioeconomic strata that majority of the citizens find themselves. Traditional food processes, such as fermentation which are easier to manage and affordable, are thus the go to processing technique for the transformation of raw materials into food forms. Further to this is poor electricity supply in many poor communities of tropical countries which also makes fermentation an important food preservation technique. Not only does fermentation transforms food, but it also creates variety, improves shelf life and help modify foods into organoleptically satisfying products (Adebiyi et al., 2018; Adebo, 2020; Rollán et al., 2019). Further to these are desirable improvements in nutritional composition, economic value and nutrient bioavailability. Beyond nutrition and sensorial qualities are health beneficial properties of fermented foods, with epidemiological studies indicating that fermented-related diets can reduce the risk of metabolic syndrome, bladder cancer, colorectal cancer and cardiovascular diseases, enhance longevity as well as quality of life (Babio et al., 2015; Gan et al., 2017; Larsson et al., 2008; Lee et al., 2017; Martínez-González et al., 2019; Pala et al., 2011; Pes et al., 2015; Sonestedt et al., 2011). Although the role of other food processing technologies cannot be downplayed, fermented foods continue to be sources of nutrition and help in meeting daily the nutritional requirements of inhabitants in tropical countries.

This book entitled "Indigenous Fermented Foods for the Tropics" is divided into different broad sections, starting with an overview and intricacies of processes involved in the production of fermented products indigenous to the three tropical continents of Africa, Asia, and South America (Section 1). These products have been classified into cereal-, legume, pulse and oilseed-, fish and meat-, dairy-, vegetable-, as well as root and tuber-based fermented food products. Further to this are insights into nutritional composition of these fermented food products, health-promoting constituents and microorganisms/microbiota responsible for the transformation of these products.

The role of technology and innovations in the quest for improving the production, quality, and safety of fermented foods is equally important and as such encouraged the increased demand for fermented food products. This demand is further driven by the fact that fermented foods are generally considered as functional food products (Kewuyemi et al., 2022; Melini et al., 2019). Thus there is the need to meet increasing consumer demands and improve the conventional fermentation techniques associated with products from the tropics to ensure the delivery of desired fermented foods with consistently better sensory attributes, nutritional and health benefits and their overall quality. Section 2 describes existing as well as potential innovative approaches for enhancing the quality of fermented foods. Advanced techniques for investigating the composition and functionality of fermented food products are also described herein. Section 3 presents safety challenges associated with these indigenous food products and ways of mitigating against them. Section 4 discusses the packaging and marketability of indigenous fermented foods of the tropics. The book is concluded with future prospects for these vital food groups.

Acknowledgments

National Research Foundation (NRF) of South Africa Thuthuka funding (Grant no: 121826), University of Johannesburg (UJ) Global Excellence and Stature (GES) 4.0 Catalytic Initiative Grant and the UJ Research Committee (URC) Grant are duly acknowledged for funding.

References

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Section 1

Overview, production and composition (health and nutritional), microbiota of fermented foods

Outline

Chapter 2 African cereal-based fermented products

Chapter 3 Asian fermented cereal-based products

Chapter 4 South American fermented cereal-based products

Chapter 5 African legume, pulse, and oilseed-based fermented products

Chapter 6 Asian fermented legumes, pulses, and oil seed-based products

Chapter 7 South American fermented legume, pulse, and oil seeds-based products

Chapter 8 African fermented fish and meat-based products

Chapter 9 Asian fermented fish and meat-based products

Chapter 10 South American fermented fish and meat-based products

Chapter 11 African fermented dairy-based products

Chapter 12 Asian fermented dairy-based products

Chapter 13 South American fermented dairy-based products

Chapter 14 African fermented vegetable and fruit-based products

Chapter 15 South American fermented fruit-based products

Chapter 16 African fermented root and tuber-based products

Chapter 17 Asian fermented root and tuber-based products

Chapter 18 South American fermented root and tuber-based products

Chapter 19 Fermented foods and gut microbiome: a focus on African Indigenous fermented foods

Chapter 20 Fermented foods and immunological effects in humans and animal models

Chapter 2

African cereal-based fermented products

Edwin Hlangwani¹, Patrick Berka Njobeh², Chiemela Enyinnaya Chinma³,⁴, Ajibola Bamikole Oyedeji¹, Beatrice Mofoluwaso Fasogbon¹, Samson Adeoye Oyeyinka⁵, Sunday Samuel Sobowale⁶, Olayemi Eyituoyo Dudu⁷, Tumisi Beiri Jeremiah Molelekoa⁸, Hema Kesa⁹, Jonathan D. Wilkin¹⁰ and Oluwafemi Ayodeji Adebo¹∗,    ¹Food Innovation Research Group, Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Gauteng, South Africa,    ²Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Doornfontein Campus, Johannesburg, Gauteng, South Africa,    ³Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Gauteng, South Africa,    ⁴Department of Food Science and Technology, Federal University of Technology, Minna, Nigeria,    ⁵Department of Biotechnology and Food Technology, University of Johannesburg, Doornfontein, Johannesburg, South Africa,    ⁶Department of Food Science and Technology, College of Basic and Applied Sciences, Mountain Top University, Ibafo, Ogun State, Nigeria,    ⁷Department of Chemical and Food Sciences, Bells University of Technology, Ota, Ogun State, Nigeria,    ⁸Biotechnology and Food Technology, University of Johannesburg, Gauteng, South Africa,    ⁹School of Tourism and Hospitality, University of Johannesburg, Gauteng, South Africa,    ¹⁰Division of Engineering and Food Science, School of Applied Sciences, Abertay University, Dundee, United Kingdom∗, Corresponding author. e-mail address: [e-mail]; [e-mail]

Abstract

The dominance of cereals as staple foods in Africa may partly be linked to the availability of numerous cereal-based fermented food products in the continent. This chapter provides an overview of cereal-based fermented food products, particularly their biochemistry (including modifications that occur during cereal fermentation), nutritional composition, health-beneficial components, as well as microbiota involved during fermentation. African cereal-based fermented foods contain substantial levels of nutrients, and their consumption is associated with numerous health benefits. While a plethora of these fermented products is available on the continent, most of them are still not fully commercialized. The composition of these vital food products is still not fully understood, thus necessitating further research.

Keywords

Fermentation; beverages; porridges; gruel; cereal fermentation

2.1 Introduction

Cereal grains and cereal-based fermented were the earliest food sources of humans (Makbul et al., 2020; Osungbaro, 2009). Nowadays, a variety of cereals are grown in about 73% of the world’s harvested area, contributing over 60% to global food production, providing energy and essential nutrients necessary for health (Awika, 2011; Karovičová & Kohajdova, 2007). These cereals, either whole grain or refined, are an important dietary source in different parts of the world (Makbul et al., 2020). Cereal-based fermented products account for approximately 77% of the total caloric consumption across Africa (Osungbaro, 2009).

Processes required to produce fermented foods have been present on earth since the beginning of humankind. Therefore, the study of these foods mainly indicates the study of the most intimate relationships between humans, microbes, and foods (Selhub et al., 2014). However, it took some time for humans to observe, accidentally, that stored fruits and cereals underwent favorable organoleptic changes and turned into alcoholic beverages (Terefe, 2016). Chemical analysis done on pottery jars found in the early Neolithic village of Jiahu, China, suggested that intentional fermentation of honey, fruit, and rice was used to provide value in traditional medicine, cultural welfare, and nutrition (Motlhanka et al., 2018). Intentional fermentation was further applied in winemaking, dairy products, brewing, and baking (Motlhanka et al., 2018).

Africans have been producing fermented products especially cereal-based (maize, sorghum, millet) products since 3500 BC (Adebo, 2020; Diaz et al., 2019; Konfo et al., 2015). Using cereals as a fermentation substrate is an effective way to develop functional foods as they are rich in nutrients that can be easily assimilated by probiotics (Ignat et al., 2020). Aceda (Sudan), uji (Kenya, Tanzania, Uganda), ogi (Benin, Ghana, Nigeria), munkoyo (Zambia), and mahewu (Southern Africa) (Fig. 2.1) are popular African examples of cereal-based fermented foods. It is important to note that fermentation of staple foods, in the context of the African continent, is still mainly a home-based process dependent on age-old techniques and locally grown raw materials (Terefe., 2016; Wedajo Lemi, 2020). The production of many African cereal-based fermented products (Table 2.1) happens in small-scale industries, villages, and homes. However, products such as bushera, chibuku, ogi, koko, umqombothi, and kunun-zaki have been commercialized on larger scales (Adebiyi et al., 2018; Hlangwani et al., 2020). The production of notable African cereal-based fermented products is described in Figs. 2.2–2.4.

Figure 2.1 Popular African cereal-based products; aceda (A) ( Suleiman et al., 2022), mahewu (also called emahewu) (B) ( Simatende et al., 2015), ogi (C) ( Obafemi et al., 2022), uji (D) ( Kubo, 2016).

Table 2.1

Figure 2.2 Flow chart of the production of some maize-based African fermented products.

Figure 2.3 Flow chart of the production of some sorghum-based African fermented products.

Figure 2.4 Flow chart of the production of some millet-based African fermented products.

The underlying nature of fermented products may be similar across different demographics throughout the continent, but these bear different names and have slight production variations (Hlangwani et al., 2020; Maleke et al., 2021). Generally, the raw materials used, the origin of the food or beverage, and the processing techniques employed are responsible for the nature of the cereal-based fermented product, making them peculiar to the cultural groups where they are relished. As such, cereal-based fermented products are an integral part of the spiritual, cultural, and socioeconomic realities of many Africans. For example, umqombothi is poured on the ground to appease ancestors (amandlozi) and served in religious ceremonies (Goitsemodimo, 2020; Hlangwani et al., 2020).

Similarly, a wide range of cereal-based fermented beverages are culturally enjoyed during circumcision, initiation school graduation, weddings, handing over of dowries, as well as births and funerals (Aka et al., 2014; Konfo et al., 2015). A Namibian nonalcoholic beverage, oshikundu is produced and served as part of the traditional initiation of young girls into womanhood (Ashekele et al., 2012). Consumers may also express their socioeconomic class and tribe by the type of cereal-based fermented products that they consume (Ezekiel et al., 2018).

The production of African cereal-based fermented foods and beverages has gradually been geared toward economic benefits. On a cottage scale, the sale of these products provides household income to many families and is often a means of economic empowerment, especially for women in rural communities (Dancause et al., 2010; Ezekiel et al., 2018; Ikalafeng, 2008; Lyumugabe et al., 2012). Cereal-based fermented products are often low-cost and thus provide affordable beverage options to low-income populations living in semi-urban areas (Hlangwani et al., 2020; Lues et al., 2009). Although per capita consumption data is lacking, the production of some of these foods and beverages runs into millions of litres per year (Ezekiel et al., 2018). This chapter provides an overview of the biochemistry, nutritional composition, health-beneficial components, as well as microbiota of African cereal-based fermented food products.

2.2 Biochemistry of cereal fermentation

In Africa, maize (Zea mays L.), pearl millet (Pennisetum glaucum L.), sorghum (Sorghum bicolor (L.) Moench), and finger millet (Eleusine coracana) are the major cereal grains used for making cereal-based fermented foods and beverages (Table 2.1). Specifically, whole-grain cereals are rich in bioactive compounds and fibers such as antioxidants, soluble fibers, non-digestible carbohydrates, and phytochemicals (γ-oryzanol, avenanthramides, benzoxazinoids, carotenoids, flavonoids, phytosterols, phytoestrogens, phytic acid, phenolic compounds, etc.) (Adebo & Medina-Meza, 2020; Kewuyemi et al., 2020; Özer & Yazici, 2019). Furthermore, most cereal-based fermented traditional foods and beverages contain a range of organic acids, bioactive peptides, phenolics (flavonoids, phenolic acids, quinones, and tannins), amino acids, minerals, bacteriocins, and vitamins (Abriouel et al., 2007; Hossain & Rahman, 2019).

Factors such as temperature, pH, growth factor requirements, length of fermentation, cereal nutrients, and moisture content of grains need to be carefully controlled to standardize quality, as they influence both the fermentation process and the final product (Ignat et al., 2020). Grinding, mashing, soaking, malting, sprouting, size reduction, salting, milling, and cooking (or heating) are some of the pre-processing technologies which have been applied to modify cereals prior to fermentation. These pre-processes remove anti-nutrients, toxic components, and improve the digestibility of the final product (Elkhalifa et al., 2006; Elkhalifa et al., 2017; Ignat et al., 2020).

The fermentation of cereals leads to activation of enzymes, detoxification, and degradation of contaminants, modification (increase, decrease, or bioconversion) of inherent metabolites and constituents, decrease in pH levels, increase in organic acids, and increased microbial and metabolic activities (Adebo et al., 2018a; Adebo, 2020). A decrease in the amount of certain non-digestible oligo and polysaccharides (stachyose, raffinose, and xylose) which reduce flatulence and abdominal distension, as well as modification in carbohydrates, has also been reported in fermented cereal grains (Galati et al., 2014). Furthermore, the enzymatic activity of the fermenting microbiota cause breakdown of starch oligosaccharides, leading to improved starch digestibility, among others (Karovičová & Kohajdova, 2007).

Improved synthesis and bioavailability of B-group vitamins have been reported during fermentation due to the ability of microorganisms that metabolize other nutrients to produce vitamins (LeBlanc et al., 2011; Samtiya et al., 2021). An increase in the amount and quality of protein and essential amino acids such as lysine, methionine, and tryptophan has been reported in sorghum, millet, maize, and other cereal products (Adebiyi et al., 2017; Price & Welch, 2013). Proteolysis and/or metabolic synthesis by fermenting microorganisms during the fermentation of cereals has increased free amino acids and their derivatives, particularly through cellular lysis, while microbial mass can also provide low-molecular-mass nitrogen-containing metabolites (Joye, 2019; Nkhata et al., 2018; Suri et al., 2014).

Phytic acid present in the form of complexes with proteins and polyvalent cations such as calcium, iron, magnesium, and zinc is degraded as the fermentation process continues, to provide optimum pH conditions necessary for the phytase activity of a wide range of microbiota (Bielik & Kolisek, 2021; Kumar et al., 2010). Fermenting microorganisms possibly use these antinutritional factors as carbon sources and such decreases may lead to an increase in the amount of bioavailable calcium, iron, and zinc by several folds (Atter et al., 2021). Fermentation generally enhances the functional properties, sensory qualities, and shelf life of the final product (Sharma et al., 2020). Unique sensorial properties and extended shelf-life make fermented foods more popular than their unfermented counterparts in terms of consumer acceptance and purchase decisions (Tamang et al., 2016).

The fermentation of cereals produces several organic acids and volatile compounds (including alcohols, aldehydes, ketones, and carbonyl compounds), which contribute to the flavor profile of each product. Pleasant aromas imparted by compounds such as butyric acid and diacetyl acetic acid make African cereal-based fermented products desirable (Hossain & Rahman, 2019; Peyer et al., 2016). Organic acids such as propionic and butyric are responsible for shelf-life extension in cereal-based fermented products (Behera et al., 2018; Egwim Evans et al., 2013). Furthermore, acetic, and lactic acids induce an inhibitory effect against the proliferation of spoilage and pathogenic microbes by lowering pH below four (Lund et al., 2020; Nkosi et al., 2021). As the pH is lowered, there is a corresponding rise in titratable acidity, with accompanying changes in functional properties (Adebo, 2020). Organic acids have an antimicrobial effect by interfering with the maintenance of the membrane potential and inhibiting the active transport in the bacterial cytoplasmatic membrane (Amrutha et al., 2017; Kovanda et al., 2019).

Flavor compounds are produced when the combined activity of malt enzymes and the proteolytic activity of fermenting microorganisms produce precursors of flavor compounds (Holt et al., 2019; Petrovici & Ciolacu, 2018). For instance, amino acids may be deaminated or decarboxylated to aldehydes, which may be oxidized to acids or reduced to alcohols (Karovičová & Kohajdova, 2007). Amino acids and their salts such as sodium glutamate contribute to the final product’s flavor (Nout & Sarkar, 1999). Flavor and taste may also be imparted by metabolites produced by lactic acid bacteria (LAB) and yeasts (Mukisa et al., 2017; Raveendran et al., 2018).

As fermentation proceeds, the amount and composition of phenolic compounds are affected (Adebo, 2020). An increase or decrease in antioxidant activity may be observed as phenolic compounds are metabolized (Adebo & Medina-Meza, 2020). During cereal fermentation, various bioactive compounds are synthesized as the cell wall of the substrates are structurally broken down. These microorganisms contain enzymes such as amylases, proteases, and xylanases, which aid in the modification of the cereal grain and chemical bond alteration, thus releasing bound phenolic compounds (Adebo, 2020). These phenolic compounds may be interconverted through decarboxylation, esterification, and hydrolysis, subjected to phase II metabolism, or conjugated to glucosides and/or related forms (Cladis et al., 2020).

2.3 Nutritional composition of African cereal-based fermented products

Beyond their spiritual, cultural, and socioeconomic values, cereal-based fermented products offer nutritional and therapeutic benefits. Many of these foods and beverages are calorie-dense and packed with bioactive compounds such as minerals, vitamins, utilizable carbohydrates (sugars), fatty acids, and digestible proteins, often imparted by the mixtures of cereal grains and the fermentation process involved. Furthermore, supplementation of these products with nuts, plant powders, spices, and tubers enhances their antioxidant properties, proteins, and thus amino acids content (Olusanya et al., 2020; Qaku et al., 2020). These African cereal-based fermented products provide between 55.34 and 1866.06 kJ/100 g of energy (Table 2.2), a bulk of which is derived from carbohydrates (Konfo et al., 2015; Lyumugabe et al., 2012; Mandishona et al., 1999) while 25% of the retained non-fermentable, partially degraded starch provides additional calories (Bamforth, 2002). Interestingly, mahewu, a fermented nonalcoholic beverage, contains over 70% carbohydrate content (Table 2.2).

Table 2.2

These cereal-based products are also relatively high in proteins. Koko, a millet gruel produced in Northern Ghana, contains proteins as much as 18.64%, a high protein content compared to most cereal-based gruels (Lei et al., 2006; Onoja & Obizoba, 2009; Soro-Yao et al., 2014a). The protein content in these products varies depending on the protein content of the raw material and the processing technology applied. Since protein substantially contributes to the staple diet of many Africans, its abundance in the starting raw material is crucial. African fermented foods also provide amino acids in diets. Millet-based beverages and gruels such as koko, kunun-zaki, malwa, zoom-koom, ben-saalga, and kirario contain significant amounts of lysine, threonine, tryptophan, and principal sulfur-containing amino acids, methionine, and cysteine, implying a better amino acid balance than in sorghum-based products (Aka et al., 2014; Brosnan & Brosnan, 2006; Kunyanga et al., 2009).

On the other hand, sorghum-based products such as amgba, bili bili, gowé, umqombothi, and hussuwa have a wide variety of amino acids, including leucine, lysine, cysteine, phenylalanine, and glutamic acid, making them good nutritional supplements (Adebo, 2020; Aka et al., 2014; Hlangwani et al., 2020). Products such as injera and umqombothi are relatively rich in dietary fiber (Table 2.2) (Ghebrehiwot et al., 2016; Hlangwani et al., 2020). Fiber is often present in high amounts as dextrins and starch residues in partially digested cereals (Joye, 2020; Lyumugabe et al., 2012). The cultivar and size of the cereal grain dictate the amount of fiber available (Abebe et al., 2015; Tsafrakidou et al., 2020). Moreover, processing steps such as enzymatic pre-treatment and fermentation can be applied to produce modified high-fiber products (Tsafrakidou et al., 2020). Table 2.2 shows the proximate composition of some African cereal-based fermented products.

Cereal grains and their fermented products are excellent sources of B-group vitamins (thiamine, riboflavin, and niacin) (Table 2.3). In particular, sorghum-based traditional beers such as amgba, dolo, umqombothi, and pito provide significant amounts of niacin, riboflavin, and thiamine (Aka et al., 2014; Ikalafeng, 2008; Lyumugabe et al., 2012). Certain sorghum-based beverages may also contain vitamin C (ascorbic acid), synthesized during germination of the substrate, and further enhanced during fermentation (Aka et al., 2014). For example, the vitamin C content in kunun-zaki produced from germinated cereals was reported to be 12,910–18,770 µg/100 g (especially millet, sorghum, and maize) (Olaoye et al., 2016).

Table 2.3

Ca, calcium; Fe, iron; K, potassium; Mg, magnesium; Mn, manganese; Na, sodium; P, phosphate; Zn, zinc.

Cereal grains products are rich in minerals, which are critical growth factors that support microbial growth for complete fermentation processes (Achi & Ukwuru, 2015). In turn, fermentation improves the food or beverage matrix by decreasing antinutritional factors (ANFs) such as phytic acid, thereby increasing the bioavailability of minerals (Verni et al., 2019). As a result, the partial breakdown of phytate means cereal-based products have higher mineral bioavailability compared to their non-fermented counterparts (Laskowski et al., 2019; Verni et al., 2019). For instance, minerals such as manganese and iron in non-fermented cereal-based products are partly bound in solid complexes with phytic acids and fiber and are thus less bioavailable (Laskowski et al., 2019).

Apart from containing lipids, vitamins, amino acids, sugars, and a wide range of hydrolytic enzymes, cereal grain embryos contain essential minerals (Achi & Ukwuru, 2015). A high mineral concentration is found in the bran fraction, especially in the aleurone layer (McKevith, 2004; Verni et al., 2019). Additional minerals are found in the seed coat enclosing the embryo and endosperm (Achi & Ukwuru, 2015). This abundance is reflected in products such as cheka, kisra, injera, kunun-zaki, and umqombothi (Abdualrahman et al., 2019; Ghebrehiwot et al., 2016; Neela & Fanta, 2020; Olaoye et al., 2016; Worku et al., 2018). These products are particularly rich in minerals such as phosphorus, potassium, iron, copper, calcium, magnesium, and manganese (Aka et al., 2014). Table 2.3 shows the minerals, vitamins, and amino acids composition of African cereal-based fermented products.

2.4 Health-promoting constituents of African-based cereal fermented products

In ancient cultures such as that of the African, traditional Japanese, and Mediterranean populations, cereal fermentation is a low-energy, low-cost, central food production strategy (Selhub et al., 2014). It is now easily understood that metabolites produced during cereal fermentation create a conducive environment for the growth of functional microorganisms, while directly inhibiting the growth of pathogenic and non-functional microorganisms (Adebo et al., 2018a; Terefe, 2016). Numerous epidemiological and clinical reports continue to demonstrate the relationship between fermented foods and human health benefits (Rezac et al., 2018). Fermentation of cereal grains has impacted human health by mitigating against carcinogenesis, mutagenesis, oxidative stress, obesity, allergies, diabetes, atherosclerosis, osteoporosis, while also increasing immunity, alleviating lactose intolerance, preventing hypertension and heart disease, reducing blood cholesterol, and protecting against pathogens (Şanlier et al., 2019; Selhub et al., 2014; Diaz et al., 2019).

Published data from in vivo and in vitro studies have indicated the antidiabetic properties of cereal-based fermented foods and beverages (Melini et al., 2019). Furthermore, consumption of fermented foods and beverages is associated with improved brain health, cognitive function, and the alleviation of mental health disorders such as depression and chronic anxiety (Şanlier et al., 2019; Selhub et al., 2014). Studies have also suggested that most cereal-based fermented beverages have anti-inflammatory, anti-diarrheal, antibacterial, anti-tumor, anti-spasmodic, anti-malarial, anti-hemorrhoid, and antioxidative properties (Adebo et al., 2018b; Hossain & Rahman, 2019; Nyanzi & Jooste, 2012; Todorov & Holzapfel, 2015).

In developing countries such as Sudan, where cereal-based fermented foods are an integral part of the human diet, researchers are exploring sustainable ways of fortifying and commercializing products (Salim et al., 2017; Şanlier et al., 2019). Across the continent, African cereal-based fermented products are still traditionally believed to have both preventive and curative properties for many known diseases, with some of these beneficial effects summarized in Table 2.4. As a result, cereal-based fermented foods continue to play a major role in the recommended daily intake of nutrients and folklore medicinal preparations (Lues et al., 2009; Wedajo Lemi, 2020). The occurrence of health-promoting components and their bioactivity make African cereal-based fermented foods and beverages worthy to be recommended for regular consumption and inclusion in worldwide dietary guidelines (Melini et al., 2019).

Table 2.4

Recent studies have established fermentation as an effective way of introducing prebiotics and probiotics into the gastrointestinal tract for additional nutritional and health characteristics (Diaz et al., 2019; Şanlier et al., 2019; Selhub et al., 2014). Rezac et al. (2018) proposed the consumption of fermented food products containing live microorganisms as a dietary strategy to improve human health by providing necessary macronutrients. Even without live microorganisms, consumption of cereal-based fermented products may still impart health benefits to the gut (Rezac et al., 2018). Abdominal symptoms associated with the ingestion of fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) in people suffering from irritable bowel syndrome can be curbed by the intake of fermented foods and beverages (Çabuk et al., 2018; Fraberger et al., 2018; Menezes et al., 2018).

For example, the consumption of cereal-based fermented beverages aids the digestive system in food assimilation and producing B-group vitamins, which are important co-factors involved in crucial metabolic processes in the human body (Kennedy, 2016; Tsafrakidou et al., 2020). LAB produces lactic acid, which reduces flatulence and abdominal distension caused by certain oligosaccharides such as raffinose, stachyose, and verbascose (Nout & Sarkar, 1999). While LAB reduces ANFs, they sequentially increase protein efficiency ratio and bioavailability of minerals and starch. These health benefits have revived the interest of Western countries in fermented foods (Melini et al., 2019). Although few of these health benefits have been highlighted (Table 2.4), further research studies and clinical trials on the effects of these products on different groups across the continent are needed to further substantiate their health-promoting and therapeutic properties. The benefits of African-based fermented products are shown in Table 2.4.

2.5 Microbiota of African-based cereal fermented products

Owing to the complexity of microbial populations in many of these cereal-fermented products, their microbiology has not been fully studied, and thus, a full understanding of their mechanisms is yet to be deciphered. However, the natural fermentation of these products yields mixed cultures of yeasts, bacteria, and fungi. The microorganisms are part of the endogenous microbiota of the substrate and only come to bear during the fermentation process. With a dynamic microbiota during the fermentation process, some microorganisms may participate sequentially, while others may participate in parallel (Blandino et al., 2003). The yeast and bacteria have a symbiotic relationship, whereby the yeast provides growth factors to promote the growth of bacteria, and the acidic environment provided by the bacteria favours yeast multiplication (Faria-Oliveira et al., 2015; Ponomarova et al., 2017). Such processes followed during spontaneous fermentation are slightly different from starter culture-based fermentation.

The composition of the food matrix, pH, salt concentration, temperature, and water activity determine the type of bacterial flora developed in each African cereal-based fermented product. LAB is responsible for mediating the fermentation process for most fermented foods in Africa and other parts of the world (Blandino et al., 2003). For a wide range of cereal-based fermented products, lactic acid fermentation contributes to the product’s nutritional value, shelf life, and safety (Phiri et al., 2019a). LAB dominates the succession of naturally occurring microbial populations in cereal processing, resulting in the generation of fermentable sugars used as sources of energy for the LAB (Abegaz, 2007; Liptáková et al., 2017). LAB produces antibiotics, hydrogen peroxide, and organic acids that impart antibiosis properties (Vieco-Saiz et al., 2019). The hydrogen peroxide produced through the oxidation of reduced nicotinamide adenine dinucleotide by flavin nucleotides can rapidly react with oxygen, thus can inhibit the growth of some microorganisms (Setta et al., 2020; Voidarou et al., 2021).

African cereal-based fermented products contain a mixture/cocktail of microorganisms as their fermentation processes are carried out spontaneously (Atter et al., 2021; Fernandesa et al., 2018; Soro-Yao et al., 2014b). The first stage of spontaneous fermentation involves lactic acid fermentation induced by different microorganisms, followed by alcoholic fermentation carried out by a portion of previous brew or dried yeast (Katongole, 2008; Phiri, 2019b). These foods are predominated by LAB more abundantly than other microorganisms such as yeasts (Table 2.5). Predominant LAB present in cereal-based fermented foods includes Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus delbrueckii, Lactobacillus sakei, Lactococcus raffinolactis, Lactococcus lactis, Leuconostoc mesenteroides (Table 2.5). Owing to the abundance of LAB, lactic acid fermentation often proceeds during the preparation of different cereal-based fermented foods made from raw materials of plant and animal origin (Lübeck & Lübeck, 2019; Nout & Sarkar, 1999). Saccharomyces cerevisiae, Candida krusei, and Candida tropicalis are predominant yeasts isolated from numerous African cereal-based fermented products (Table 2.5). The microbiota of some African cereal-based products is shown in Table 2.5.

Table 2.5

LAB contributes to the production of organic acids, other antimicrobial compounds, and mitigates against susceptible bacterial pathogens. In particular, Enterococcus faecium and Lactobacillus species isolated from various African fermented foods such as kenkey, ogi, and brukina were found to produce bacteriocins (Nout & Sarkar, 1999; Olasupo et al., 1994; Tawiah, 2016). In a follow-up study involving the experimental fermentation of maize dough, Olasupo et al. (1997) reported the inhibitory effect of bacteriocin produced by Lactobacillus casei strain 012 on the enterotoxigenic strain of Escherichia coli. Leuconostoc, Streptococcus, Lactobacillus, Bifidobacterium, Lactococcus, Enterococcus are the dominant genera of LAB with probiotic properties (Bintsis, 2018; Fijan, 2014). For these probiotic microorganisms to impart health benefits and maintain a healthy intestinal microbiota, they are recommended to be adequately and regularly ingested to a threshold value of 10⁶ CFU/mL per serving (Setta et al., 2020). While most of these studies have adopted traditional culture-dependent approaches in studying the microbiota of these products, there is a need to adopt better and more robust techniques such as metagenomics to further provide insights into the plethora of microorganisms present in them (details are provided in chapter 22).

2.6 Conclusion and future directions

African cereal-based fermented products have continued to be an important part of the staple diet of many people across the continent. Fermentation of cereal-based foods and beverages remains mainly a home-based activity in many African countries and over the years, as only a handful of products have been commercialized. Consumption of cereal-based fermented foods of African origin has potential nutritional and nutraceutical benefits to consumers, providing them with important food constituents for healthy living. Comprehensive knowledge of the microbiota involved in the fermentation of these foods is in their preliminary stage. Hence, high-precision equipment and validation methods are required for their analyses. African cereal-based fermented products have appeared mostly in the local markets of their respective countries, and this necessitates adequate efforts geared toward the development of standardized processes for their commercialization, using starter cultures to aid fermentation and upscaling of African cereal-based fermented food products. There is also the need to provide appropriate packaging technologies for prolonged shelf extension during distribution and marketing.

Acknowledgments

This work was