Sprouted Grains to Combat Malnutrition

Sprouted Grains to Combat Malnutrition: History

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Subjects: Food Science & Technology

Contributor:

Mahsa Majzoobi

Ziyu Wang

Shahla Teimouri

Nelum Pematilleke

Charles Stephen Brennan

Asgar Farahnaky

Due to the global rise in food insecurity, micronutrient deficiency, and diet-related health issues, the United Nations (UN) has called for action to eradicate hunger and malnutrition. Grains are the staple food worldwide; hence, improving their nutritional quality can certainly be an appropriate approach to mitigate malnutrition.

germination
nutrient-dense
environmentally friendly
grains
functional foods

1. Introduction

Grains, including cereals, pseudocereals, and pulses, are staple foods worldwide and significantly contribute to human nutrition and well being [1]. The popularity of grains has further increased with the growing demand for sustainable plant-based foods. However, over the last century, selected grains with high production yields have been grown to provide affordable foods for the world’s growing population and to combat food security risks due to climate shocks and disruption of the food supply chain. This has raised major concerns since selective breeding has drastically reduced the diversity of the available grains for food consumption [2]. The dominance of highly productive grains known as leading crops (e.g., wheat, rice, and corn) has marginalized the production and utilization of other grains known as minor grains (e.g., pseudocereals). In addition, by increasing the production yield of leading grains, their nutrient concentration, especially protein and micronutrients, has diminished significantly [3]. Other factors, including unsuitable soil conditions and climate shocks, can cause poor nutrient accumulation in the grains [4]. As a result, greater consumption of grains is required to provide the Food and Drug Administration (FDA) recommended intake of nutrients leading to the increased risk of diet-related noncommunicable diseases, including obesity, type 2 diabetes, cardiovascular diseases, and micronutrient deficiency [2,5]. The global rise in micronutrient deficiency and diet-related health issues coincide with the increased consumption of high-yielding crops over the last few decades [2,6].

2. Sprouting Process

Sprouting, also known as germination, is a historical process practiced since 5000 years ago. The sprouting process is a natural, flexible, cost-effective, and sustainable process of grain enrichment with macro and micro-nutrients required to treat malnutrition. When performed under optimum conditions, it is an effective, sustainable, and green intervention to enhance the nutritional quality and health benefits of the grains and to reduce/eliminate some of their major limitations, such as anti-nutrients, allergenicity, and indigestibility. It is also highly effective in mitigating some grain processing complications such as dehulling, long cooking time, and undesirable taste [9,10,11]. Sprouted grains are whole grains that have just begun germinating and are collected before sprout growth exceeds kernel length [12].

The sprouting process is adoptable at home, traditional, and industrial settings and can be applied to various grains, including native grains of areas with a prevalence of undernourishment (e.g., sorghum and pseudocereals), as well as modern grains (e.g., rice and wheat) to transform them into nutrient-dense products in a short time [13,14].

The sprouting process initiates when the grains are exposed to water and accelerates with increasing temperature. The process involves three major phases, shown in Figure 2. The first phase, known as “imbibition”, occurs during the soaking or steeping of the grains in water (often 1:1.5 w/v). It involves rapid water uptake and full hydration of the dry seeds. The absorbed water travels across the kernel and reaches the germ, scutellum, seed coat, and pericarp. This stage may take about 24 to 48 h at about 20–25 °C, during which the steeping water is often replaced to avoid contamination. In the second phase, known as “sprouting” or “germination”, the grains are drained and transferred into sprouting vessels and incubated under controlled humidity and temperature depending on the grain type, genetic variation, source, and age. However, a relative humidity of about 85–99% and a temperature range of 20–30 °C for about 3–7 days with or without light are commonly used. At this stage, the grains rapidly restore their metabolic activity and release or synthesize abscisic acid, gibberellic acid, and ethylene as the main plant hormones that stimulate the production of enzymes, including cellulase, phytase, amylase, protease, and lipase to produce simple molecules (e.g., glucose, amino acids, and phosphorous) required for the embryo to grow. The activity of these enzymes brings about significant changes in the biochemical composition, nutritional quality, health benefits, and organoleptic properties of the grains [12,15].

Figure 2. Typical sprouting process of mungbean (this figure is produced by M.Majzoobi).

3. Biochemical Changes

During sprouting, some biochemical changes occur that enhance the nutritional quality of the grains to address undernourishment and its consequent health issues. Previous studies on the sprouted grains have indicated that the extent of biochemical changes in the sprouted grains is controlled by various parameters, including grain species and variety, sprouting conditions, the seedling growth stage, and laboratory techniques [16,17]. Additionally, different biocomponents of the same grain may vary differently or remain unchanged under similar sprouting conditions; thus, choosing a sprouting condition that favors some components may be against others. Thus, the exact nutritional composition of sprouted grains is unclear and may exhibit various biological health effects compared to ordinary grains or different sprouting conditions [16,18,19]. Table 1 shows sprouting conditions that positively affect increasing nutrients and bioactive compounds in the grains.

Table 1. Sprouting conditions and biochemical changes that are in favor of improving the nutritional quality of some grains.

Sprouted Grain	Condition Used	Finding	Ref.
Normal and waxy wheat	Soaking: 20 °C, 6–8 h Sprouting: 20 ± 5 °C, 9–11 days on soft agar (1.5% agar)	Increase in protein content and digestibility, fiber, ash, total phenolic and flavonoid contents, and antioxidant activity, anti-inflammatory effects. Decrease in fat, carbohydrate, phytic acid, and cell toxicity.	[68,69,70]
Brown rice	Soaking: 28–30 °C, 12 h Sprouting: 24 h, 28–30 °C, 90–95% RH	Increase in protein content and digestibility, starch digestibility, niacin, amino acids, vitamin E, vitamin C and pyridoxine, GABA, γ-oryzanol, antioxidants. Decrease in phytic acid. No change in ash, crude fat, or carbohydrate.	[70,71]
Mung bean	Soaking: 25 °C, 12 h Sprouting: 60 h, 25 °C, 70% RH	Increase in protein content and digestibility, ash, crude fiber. Reduction in carbohydrate, resistant starch, and crude fat.	[72]
Chickpea	Soaking: 25 °C, 12 h Sprouting: 60 h, 25 °C; 70% RH	Increase in protein, ash, crude fiber, and reduction in carbohydrate and crude fat.	[73]
Quinoa	Soaking: 22 °C, 4 h Sprouting: 72 h, 22 °C, 95% RH	Increase in protein, ash, and crude fiber and reduction in carbohydrate, crude fat, and ash.	[74]
Buckwheat	Soaking: 22 °C, 1 h Sprouting: 12, 24, 36, 48, 60, and 72 h, 25 °C, 90% RH	Increase in protein, total phenolic, and flavonoid content. Decrease in crude fat and phytic acid.	[75]
Oat	Soaking: 22 °C, 4 h Sprouting: 18 °C for 96 h, ≥90% RH, in darkness	Increase in reducing sugar, protein, essential amino acids, minerals (Ca, Fe, Zn, Mg), riboflavin, and essential fatty acids. No change in soluble and insoluble fiber.	[76]

4. Processing of the Sprouted Grains

Figure 3 shows an overview of the food applications of the sprouted grains. Fresh sprouts are commonly used as culinary ingredients in restaurants and homemade cooking. Although rich in nutrients and bioactive compounds, they are prone to microbial contamination and rapid spoilage if not properly handled, packaged, and stored. Additionally, fresh sprouts are rich in some enzymes (e.g., amylase, protease, and lipase) and biological compounds (e.g., reducing sugars, amino acids, unsaturated fatty acids, and phenolic compounds). During food processing and storage, these compounds can contribute to some undesirable chemical reactions such as Maillard reactions, oxidation, and starch and protein hydrolysis, resulting in adverse effects on the quality and shelf-life of the end products. Thus, fresh sprouts are often further dried using oven, solar, or freeze-drying methods to increase their shelf-life and deactivate enzyme activity [77].

Figure 3. Common food applications of sprouted grains (this figure is produced by M.Majzoobi).

Dried and powdered sprouted grains have been included in healthy snacks, bread, breakfast cereals, noodles and pasta, prebiotic foods, fermented products, and baby foods [61,62]. However, it is critical to assess the nutritional quality of the end products to convey the expected health benefits to the consumers. Table 2 shows some food products formulated with different sprouted grains and the observed changes in quality, nutritional value, and health benefits. Bioactive compounds and many biochemical compounds such as proteins and lipids are often lost during food processing and storage as they are often decomposed at elevated temperatures, exposure to light, high shear, and pressure. Thus, choosing the suitable processing type and conditions to protect nutrients in the foods are of great importance.

The use of sprouted wheat and other grains such as pseudocereals, rice, and lentils in bread-making has been reported, which could manipulate obesity and diabetes in mice [78]. Nevertheless, these studies have indicated that using sprouted grains in bread-making requires careful control of the sprouting conditions and bread-making process. In a prolonged sprouting process, excessive production of hydrolyzing enzymes such as alpha-amylase, similar to the preharvest sprouting, can result in inferior dough and bread quality. It has been indicated that a sprouting time of 12 h is enough to enhance the nutritional quality of wheat without triggering excessive hydrolyzing enzymes [61]. Most of the previous studies indicated an accelerated fermentation process of the dough, a darker crust color, a softer bread crumb, a sweeter taste, and a longer shelf-life of the bread. Similar results have been reported when other sprouted grains, including oats, brown rice, maize, barley, and their mixture have been used in bread production [62,79].

Sprouting has been used to reduce grain hardness as a common issue in processing, for example, in brown rice cooking. It creates some micro-cracks and features on the grains, which can facilitate water penetration into the grains, resulting in shorter cooking time, which is an issue with hard grains such as pulses. It has been used to reduce the long cooking time of some grains, such as brown rice and barley; however, the stickiness of the cooked rice remains the same [15].

Sprouted grains are also suitable for the production of special-diet foods. Using sprouted pseudocereals such as buckwheat as a natural way of enhancing the nutritional quality of gluten-free bread has been reported. The resulting bread had significantly higher antioxidants and phenolic content [15].

It has been reported that sprouting can be used to reduce oligo-, di-, monosaccharides, and polyols (FODMAPs) compounds in some grains, including pulses and pseudocereals, to make them suitable for a low FODMAP diet. However, this method is not suitable for cereals as it accumulates fructan in the grains [80].

Table 2. Addition of some sprouted grains in foods and their effects on quality, nutritional value, and health benefits.

Spouted Grains	Sprouting Conditions	% Sprouted Grains in Foods	Product Quality	Nutritional Value of the Product	Health Benefits	Reference
Lentil	Soaking: 24 h at 20 °C Sprouting: 96 h, 90% RH, 25 °C	0, 10, 20% in bread	Up to 10% volume increased but reduced at 20% replacement; Darker color; Harder texture.	10% reduced phytic acid; 20% increase in iron; 10% increase in protein; no change in antioxidant content	Not reported	[81]
Wheat	Soaking: 26 °C, 6 h. Sprouting: 20 ◦C, 80% RH, 12 and 24 h	10 to 50% in bread and wheat-based fermented beverage	Slower starch retrogradation. Sensory attributes increased	Not reported	Not reported	[82]
Wheat, barley, pearl millet, and green gram	Soaking: in water, 8 h, 30 °C. Spouting: 35 °C, 95% RH, 24–36 h	2–8% in non-dairy probiotic drink	Increased Sensory acceptability and probiotic count	Increase in protein digestibility	Not reported	[83]
Corn	Soaking: 8 h Sprouting: 72 h, 24 °C 80–90% RH	Non-alcoholic fermented beverages (kombucha)	Improved appearance, flavor, smell, color, and mouthfeel	Not reported	Improved health benefits	[84]
Buckwheat, ed Job’s tears, and mungbean	Soaking: 10–24 h, room temperature Sprouting: 6 h-7 days, 10 °C	20% in rice cakes	Decreased starch pasting properties. Slowing retrogradation; Improved textural and sensory properties	The dietary fiber increased. Texture properties and sensory evaluation improved.	Improved starch digestion	[14]
Brown rice	Soaking: in water, 24 h at 28 °C Sprouting: 48 h and 96 h	Fermented yoghurt	Promoting the growth of the starter culture in yogurt. Increase in the average scores for organoleptic properties	Increase in phenolic compounds and GABA, consistency index, and density	Low glycaemic index, increase in health-promoting properties	[85]
wheat barley, chickpea, lentil, and quinoa grains	Soaking: in water, room temperature, 30 min Sprouting: in water, 24 h, 16.5 °C	20% in bread	Improved sensory quality	Increase in peptides, free amino acids, GABA, Decrease in phytic acid, tannins, raffinose, and trypsin inhibitors.	High protein digestibility and low starch availability	[86,87,88]

5. Challenges of Using Sprouted Grains in Foods

Fresh sprouts are highly prone to biological, chemical, and physical contaminations that occur during pre- and post-harvest processing [89]. Fresh sprouted grains are increasingly perceived as potentially hazardous foods contaminated mostly by the main sources of food-borne pathogens such as Escherichia coli O157, many serotypes of Salmonella and Bacillus cereus, and pathogens and dangerous filamentous fungi such as Aspergillus clavatus, A. flavus, A. niger, Fusarium nivale, F. culmorum, Trichothecium roseum, and Penicillium spp. [89,90]. Thus, all stages of sprouting, from seed selection to the consumption stage, must be under control to prevent any food safety hazards. Strategies to eliminate microbial risks have been described previously [91].

Another challenge is related to the high dependency of grain nutrients on various internal and external factors such as grain type and variety, physiology and dormancy, and variation in the sprouting and post-processing conditions, leading to inconsistency in the reported biochemical changes and health benefits [42,92]. Additionally, the conditions with positive effects on some biochemical components may not be in favor of others. Thus, the factors with significant effects on the biochemical composition and nutritional quality of the sprouted grains, including biofortification and elucidation, should be examined and optimized to achieve maximum benefits to address malnutrition.

Despite their excellent nutritional benefits and potential to be included in our diet, sprouted grains are still underutilized in home and industrial food production partly due to the lack of awareness about their consumption, organoleptic properties, quality, and optimum food formulation and processing techniques. There is also a lack of technical knowledge on various industrial processing methods to enhance post-harvest shelf-life and applications of sprouted grains in food and nutraceutical products [93,94].

This entry is adapted from the peer-reviewed paper 10.3390/foods12213901

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