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2020 | Buch

Upcycling Legume Water: from wastewater to food ingredients

verfasst von: Luca Serventi

Verlag: Springer International Publishing

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

Food manufacturing generates an incredibly high volume of wastewater. The legume industry is one of the top contributors to this environmental issue, as soaking and boiling are necessary to transform dried legumes into cooked canned products and other legume-based products, such as soymilk, tofu, hummus and flours. Wastewater must be treated prior to disposal into the environment, thus raising production costs for the food industry. In addition, wastewater contains nutrients that are lost from the food chain after disposal. As water and soluble nutrients are becoming a limited resource, it is critical to optimize food manufacturing at all levels.

Recycling Legume Wastewater Into Food Ingredients presents a sustainable solution to this increasing demand for food and water. The text analyses the composition of legume wastewater and its physicochemical properties, including its potential applications in emulsifiers, foaming agents, gelling agents and antistaling ingredients. Early chapters discuss the processing of legumes and the wastewater generation involved. Further sections focus on wastewater generated by soaking and cooking, including the composition, functional properties, and food applications involved in each. Sprouting water, bioactives and applications in edible packaging are also discussed.

In presenting a sustainable solution for legume wastewater use, this text is an important key to sustainability in food processing and the reduction of waste.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction: Legume Processing

Abstract

Legumes consist of pulses (several types of beans, chickpeas, lentils and peas) and non-pulses (peanuts and soybeans). They are a good source of starch, protein and fibre for humans, consumed worldwide as staple food. The nutritional profile vary based on the legume type, cultivars and origin. Starch is the main component of pulses, representing about 50–75 g/100 g (in common beans and lima beans, respectively). On the contrary, soybeans only contain 10 g/100 g starch, in favour of more fibre (20 vs. 10 g/100 g) and, most significantly, protein: 41 vs. 15–25 g/100 g. Lipids are moderate in chickpeas and abundant in peanuts and soybeans: 50 and 20 g/100 g. Consumption occurs upon processing such as soaking, boiling and milling. When used as flours, legumes develop stable foams, emulsify and absorb water and oil. Foaming ability ranges from 40% to 175%, while the emulsifying activity index spans from 10 to 18 m²/g. Finally, water absorption capacity exceeds oil absorption: 1.3–6.7 g/g vs. 0.9–2.2 g/g, respectively. Protein supports foaming and emulsifying ability, while a combination of carbohydrates and protein contributes to the thickening abilities. This chapter provides an overview on legumes in terms of nutritional value and functionality as food ingredients.

Paramjot Kaur, Luca Serventi

Chapter 2. Introduction: Wastewater Generation

Abstract

Legumes contain abundant amounts of protein, dietary fibre, oligosaccharides, minerals, vitamins and phytochemicals. However, antinutrients are present and crystalline starch is poorly digestible. Soaking, boiling, steaming and canning are common processes used to reduce antinutrients and deliver organoleptic quality. Nonetheless, legume processing produces large volumes of wastewater and causes significant nutrient loss. Soaking was shown to mainly impact oligosaccharides, resulting in 50–75% loss. Protein, dietary fibre, vitamins and phytochemicals were lost as well. Boiling caused drastic losses of oligosaccharides (60–85%), as well as fibre, vitamins and phytochemicals. Steaming reduced protein content of various pulses by 1–5%. Canning mainly impacted the vitamin content (losses of 46–65%), in addition to dietary fibre and oligosaccharides. Some of these changes might be the result of thermal degradation, while others might indicate leaching in the processing water. Therefore, this chapter discuss the generation of wastewater during legume processing and its nutritional potential.

Silu Liu, Luca Serventi

Chapter 3. Soaking Water Composition

Abstract

Soaking legumes is necessary for consumption, but nutritional losses occur during this process. Partial explanation to the altered nutritional profile of soaked legumes could be leaching in the processing water. Therefore, this chapter examines recent publications and discusses new experimental findings on the composition of legume soaking water. Studies have shown that the soaking water of legumes contained 0.26–2.38 g-100 mL of dry matter. Seeds geometry (size, shape) and structure (whole, split) affects leaching, with the highest losses for haricot beans and split yellow peas. Soluble and insoluble carbohydrates each constitute about 30% of the leached material, followed by lower levels of protein (20–30%) and minerals (15–20%). Iron, magnesium, potassium and phosphorous were present in nutritionally relevant quantities: 100 mL of legume soaking water contained up to 200% of the recommended daily intake. On the contrary, phenolic compounds and saponins were found in modest amounts: 0.3 and 3.0 mg/g, respectively. Similarly, antinutritional factors such as phytic acid and trypsin inhibitors represented minor fractions of the solids. Only soybean soaking water contained about 3 TUI/mg of trypsin inhibitors, well below values of processed legume foods (1.6–14 TUI/mg). In closing, legume soaking water is an interesting source of oligosaccharides and minerals.

Luca Serventi

Chapter 4. Soaking Water Functional Properties

Abstract

The soaking water of legumes containd soluble and insoluble carbohydrates, protein, minerals, phenolic and saponins. These compounds are known to improve food texture and act as prebiotics. Therefore, this chapter presents new findings on legume soaking water as texturizer (freeze-dried) and prebiotic (liquid). The low fractions of soluble carbohydrates and proteins resulted in modest foaming ability (4.0–19%), modest oil absorption capacity (2.1–2.7 g/g) and insignificant effects on water absorption. In contrast, excellent emulsifying ability was observed for split yellow peas (50 m²/g), with relevant values for green lentils and yellow soybeans. Different mechanisms have been proposed: presence of both soluble and insoluble proteins (peas), saponins (lentils) and amphiphilic proteins (soy). Remarkably, prebiotic properties were observed in liquid samples. The growth of probiotic Lactobacilli occurred to levels drastically higher than a standard nutrient broth. Oligosaccharides were abundant in haricot beans, while higher biological value of soy proteins might explain soy performance. Results of lentils and peas were lower than other legume. Antimicrobial peptides known as defensin Psd1, Psd2 (peas) and Lc-def (lentils) might have inhibited microbial growth. In summary, lentil soaking water can be freeze-dried into excellent emulsifiers, especially peas. Beans and soy soaking water are also promising prebiotics.

Luca Serventi, Congyi Gao, Wendian Chang, Yaying Luo, Mingyu Chen, Venkata Chelikani

Chapter 5. Soaking Water Applications

Abstract

Legume soaking exert emulsifying properties. In addition, they contain soluble fibre, protein and phytochemicals that may deliver other functionalities. Plant-based ice creams and gluten-free bakery products rely on expensive hydrocolloids to achieve acceptable texture. Therefore, these applications were tested. Pea soaking water drastically enhanced the melting properties of plant-based ice cream. The dripping time delayed from 5 to 30 minutes and the overall melted volume reduced from 18 to 23 ml/60 ml. Slow melting relates to higher stability and was attributed to the emulsifying ability. In addition, no significant effects on colour and sensory acceptance were observed. When used to formulate gluten-free crackers, a relevant antistaling effect took place. The soaking water of haricot beans and green lentils softened texture during storage, without affecting pasting properties and moisture content. Soluble fibre (beans) and phytochemicals (lentils) were speculated to enhance protein plasticity. In gluten-free bread, yeast metabolism must be considered. Those ingredients that are high in soluble fibre and low in saponins (chickpeas, peas) significantly reduced bread crumb hardness by means of enhanced pore homogeneity, likely resulting from emulsifying abilities that supported higher gas retention and loaf volume. Soaking water of numerous pulses may replace hydrocolloids in ice cream, crackers and bread.

Luca Serventi, Jingnan Zhu, Hoi Tung Chiu, Mingyu Chen, Neha Nair, Jiaying Lin, Sachin Deshmukh

Chapter 6. Cooking Water Composition

Abstract

The discovery of Aquafaba as egg replacer has generated wide interested in the application of legume wastewater as food ingredient. Therefore, the cooking water from boiling and canning of chickpeas and other legumes have been analysed. The dry matter accounted for 3–6 g/100 g of the liquids, mainly consisting of carbohydrates: sugars, soluble and insoluble fibre. Proteins and minerals represented 10–30% of the dry matter.

High levels of iron, potassium, magnesium, molybdenum and other minerals were found. Similarly, nutritionally relevant levels of saponins (5–15 mg/g) and phenolic compounds (0.2–0.7 mg/g) leached in the cooking water. A 100 ml serve of these ingredients could provide the recommended daily intake of numerous nutrients. Interestingly, the levels of antinutritive phytic acid and trypsin inhibitors were low, possibly due to thermal degradation. Fascinatingly, it was observed that the nutritional profile of the cooking water did not correlate with legumes composition. Instead, seeds geometry determined cooking water profiles. For example, chickpeas irregular shape allowed the outer shell to break upon boiling, thus releasing more insoluble fibre than other legumes. Seed conformation, size and thickness affects solid release in the processing water, making it a new nutritionally interesting food ingredient.

Luca Serventi

Chapter 7. Cooking Water Functional Properties

Abstract

Aquafaba was shown to replace egg white in confectionery products. Nonetheless, limited information was available on its physicochemical properties. Thus, recent studies investigated legume cooking water as texturizer. Most samples were slightly acidic (pH 6.1–6.5). Foaming capacity ranged from 38% to 97% based on legume type, within range of egg white solutions of similar concentration. A direct correlation to protein content was found. Despite the boiling process, most protein was soluble (86–100%). Ultrasounds treatments enhanced foaming properties of Aquafaba up to 548%. All foams were highly stable, potentially due to saponins. Emulsifying properties were outstanding, reaching values of 47 m²/g (lentils) and 100% (chickpeas). A combination of fibre, protein and saponins potentially contributed to highly stable emulsions. Higher hydrophobicity was observed, with absorption capacity of oil exceeding that of water (2.7–3.2 vs. 0.1–2.2 g/g) due to the presence of more hydrophobic sites on macromolecules. Finally, excellent prebiotic potential was determined. Most cooking water contained high levels of fermentable oligosaccharides, protein and minerals to support bacterial growth. The only exception was soy, possibly due to the higher phytate content. In summary, pulses cooking water are good foaming and gelling agents and excellent emulsifiers. Prebiotic potential opens the door to new applications.

Luca Serventi, Congyi Gao, Mingyu Chen, Venkata Chelikani

Chapter 8. Cooking Water Applications

Abstract

Aquafaba gained popularity as vegan alternative to eggs in 2015. From that discovery, multiple food applications have been proposed. Raw foams were developed by replacing egg white with Aquafaba, although softer texture and darker colour were observed. When cream was introduced, sensory acceptability was high, with lower perceived sweetness, likely the result of phenolics and saponins. Baking into meringues highlighted the need for gelling abilities, present only in the cooking water of certain pulses. Lower saponin content and lighter colour of chickpeas and peas allowed them to be acceptable replacements of egg white in meringues. Alternatively, soy cooking water was used to manufacture gluten-free crackers. Interestingly, hardness decreased during storage, while moisture content increased. The high hydrophilicity of soy proteins was considered responsible of the antistaling mechanism. In leavened products such as gluten-free bread, chickpea cooking water significantly enhanced loaf volume and reduced crumb hardness. Superior structural stability and pores homogeneity was depicted by microscopy, comparably to the hydrocolloid xanthan gum. Finally, Aquafaba was tested in cakes and mayonnaise to replace whole eggs. Minor differences in colour were noted and overall satisfying sensory acceptance was achieved. Legume cooking water can find applications as egg replacers and hydrocolloids.

Luca Serventi, Yiding Yang, Yaqi Bian

Chapter 9. Sprouting Water Composition

Abstract

Legumes are highly nutritious but they also contain antinutrients such phytic acid and trypsin inhibitors that can hinder mineral and protein absorption. Consequently, germination of legume seeds in sprouts is an established food process to enhance their nutritional bioavailability. Sprouting at 20–35 °C, based on legume type, results in 2–5% higher protein content, while 11–17% loss of lipids was reported. Mineral profile varied according to the cultivar. For example, sprouted chickpeas contained less calcium and potassium than the raw counterpart. Phenolic compounds increased by threefolds with germination. Vitamins A, B1, B2, B3, C and E remarkably increased by up to tenfolds in numerous legumes. These results indicate higher nutritional content, along with reduced levels of antinutrients. Sprouting involves humidification of seeds which might cause solid leach. Thus, wastewater of chickpea sprouting was studied. Minerals were found. More interestingly, significant levels of the enzyme protease were determined. These findings indicate that sprouting water of legumes has potential as alternative source of minerals and proteolytic enzymes.

Dan Xiong, Congyi Gao, Luca Serventi, Yuxin Cai, Yaqi Bian

Chapter 10. Bioactives in Legumes

Abstract

Legumes exert several health benefits: anticancer, anti-inflammatory, anti-obesity, antioxidant, antimicrobial and heart protection. Bioactive compounds, namely phenolics, peptides, saponins, vitamins and lipids, are responsible for these properties. Legume wastewater was shown to contain moderate amounts of phenolics (0.3–0.6 mg/g), proteins (0.7–1.5 g/100 g) and saponins (6–14 mg/g). Phenolic compounds express all activities described above and include the following nutrients: phenolic acids, flavonoids, anthocyanins, flavanols, flavones, flavanones and tannins. Bioactive peptides consists of albumin, globulin and defensin, responsible for numerous properties. Saponins inhibit cancer growth and prevent obesity, while vitamins act as anti-inflammatory and antioxidants. Certain lipids may inhibit cancer growth and act as anti-inflammatory but were not detected in legume wastewater. Vitamin content of legume cooking water has not been investigated yet, offering noteworthy opportunities to researchers. Therefore, legume wastewater might express interesting bioactivities. Industrially, this by-product could be used to extract bioactives or as a wholesome source.

Luca Serventi, Lirisha Vinola Dsouza

Chapter 11. Edible Packaging from Legume By-Products

Abstract

The world plastic industry produces over 322 million tons of waste per year. Thus, bioplastic and edible packaging are highly researched due to their reduced environmental impact. Legumes have been used in packaging in the form of soy fibre and protein. Soy fibre is extracted by sieves, columns or freeze-drying sieving, then processed physically by compression molding or enzymatically by microbial transglutaminase. Soy proteins are extracted by centrifugation or filtration/ultrafiltration. Protein manufacturing can be achieved by addition of several ingredients: plasticizers, surfactants, biodegradable polymers and oils. Alternatively, proteins can be modified via chemical cross-linking (salts), radiation modification (UV), enzyme cross-linking or surface modification. Legume wastewater contains interesting levels of carbohydrates, with as much as 2.5 g/100 g of insoluble fibre. In addition, proteins account for up to 1.6 g/100 g. Therefore, a new technology that upcycles fibre and protein from legume wastewater into edible packaging is encouraged. The challenge is achieving acceptable structure and thermal stability while keeping the costs low. Processing legume fibre and proteins can provide the desired technological quality. In addition, upcycling by-products such as wastewater can reduce manufacturing costs. This could be the start of a new era for bioplastics and sustainable food packaging.

Yanyu Zhang, Luca Serventi

Backmatter

Titel: Upcycling Legume Water: from wastewater to food ingredients
verfasst von: Luca Serventi
Verlag: Springer International Publishing
Electronic ISBN: 978-3-030-42468-8
Print ISBN: 978-3-030-42467-1
DOI: https://doi.org/10.1007/978-3-030-42468-8