Linsen, rot, roh (Bio?)

TABLE 1 | Bioactive and antinutrients effects of phytochemicals commonly found in food legumes.

Lentil, one of the oldest food crops, was domesticated in south-
ern Asia as early as 7000 bc (Samaranayaka 2017). Along with
peas, chickpeas, and common beans, it is the most widely eaten
leguminous seed in the world (Harlen and Jati 2018). 

In addition to a richness of macro and micronutrients, lentils also contain a number of bioactive phytochemicals, including phenolics, flavonoids, saponins, carotenoids, phytic acid, tocopherols, and phytosterols

 Along with macronutrients and micronutrients, it provides a range of non-nutritional constituents, which are categorized as bioactive compounds. These compounds have immense roles in maintaining biological functions in plants and animal kingdom. Some of these compounds are regarded as antinutritional factors (ANFs) because they prevent nutrients from being absorbed. Processing methods such as cooking, germination, fermentation, dehulling, milling, and extrusion can drastically reduce the amount of ANFs contained in lentils. The primary objective of dehulling and milling is not to reduce or eliminate the ANFs of lentils but to increase their feasibility for using in various food applications. 
 The dark-colored (black and red) lentils contain higher amount of anthocyanin than many other common legumes such as peanut black, common bean, cowpea, and soybean (Harlen and Jati 2018).

Eating unprocessed or inadequately processed mature lentil seeds in sufficient amounts would cause digestive discomfort or sickness to the monogastric animals including humans, poultry and pigs (Sparvoli, Bollini, and Cominelli 2015). The reason for this is that lentils contain antinutritional factors (ANFs) such as trypsin inhibitors, phytic acid, and several types of tannins. ANFs are biological elements found in food materials that may lower nutrient intake or utilization, resulting in weakened digestive and metabolic processes. Different processing techniques (heat treatments, extrusion, germination or sprouting, and fermentation) are used to inactivate the ANFs (Stefaniak and McPhee 2015).

the processing of lentils has certain benefits as regards consumption and digestion as well availability of bioactive constituents, which are also discussed in this review article.

Lentils have a total saponin concentration between 654 and 1269 mg/kg (DW basis) with the primary saponins being soyasaponin I and VI (Ruiz et al. 1996). According to different research, soyasaponin I and soyasaponin βg (also known as VI) levels in 32 Italian lentils ranged from 28 to 407 mg/kg and 110 to 1242 mg/kg, respectively (Sagratini et al. 2009). The phytic acid (or inositol hexaphosphate) in lentils has been found to be 4.91 mg/g, inositol pentaphosphate 0.72 mg/g, and inositol tetraphosphate 0.09 mg/g (Ayet et al. 1997). Tannin–protein complexes result in limited protein digestibility and amino acid availability. Similarly, trypsin inhibitors take part in inactivating the digestive enzyme trypsin. 

Narrativer Review in wissenschaftlichem Journal 

DOI: 10.1002/leg3.253

Study: weak evidence

in vitro protein digestability: Soaked flours: 85.5%
Soaked and cooked flours: 91.7%
Soaked, cooked and dehydrated flours: 95.5%
Germinated seed: 75.1%
Dehulled germinated seed: 78.8%

However, it should be bear in mind that one of the main issues related to pulse consumption is related with inadequate diets; in a well-balanced diet, the level of bioactive compounds may contribute to reduce the risk of chronic diseases, but in an unbalanced diet, ANF's may decrease the nutritional quality of pulses (Margier et al., 2018).

More recently, some reports showed that, depending on the dose, some ANF (e.g., lectins, protease inhibitors, and ACE inhibitors) also display positive bioactivities, namely antioxidant, hypolipidemic, hypoglycaemic, and antitumor effects (Luna-Vital & de Mejía, 2018; Luna-Vital et al., 2015; Sánchez-Chino et al., 2015). In addition, epidemiological studies demonstrated that countries with a high consumption of pulses presented a reduced risk of several types of chronic diseases, lower incidence of colorectal cancer, type-2 diabetes, and cardiovascular diseases (Campos-Vega, Loarca-Piña, & Oomah, 2010; Champ, 2002; Sánchez-Chino et al., 2015).

Moreover, some protein ANF such as lectins have been linked to the activation of innate defence mechanisms, cancer prevention, and potential therapeutic action on prevention and control of obesity. Furthermore, lectins were reported as one of the most potent naturally occurring insecticidal proteins. In fact, various transgenic plants have been developed using lectin genes. Protease inhibitors, in turn, have shown potent anti-inflammatory properties, whereas ACE inhibitors were associated to hypertension reduction (Campos-Vega et al., 2010; Champ, 2002; Muzquiz et al., 2012; Pusztai et al., 2004; Roy et al., 2010).

In turn, dietary saponins (non-protein ANF), can lower plasma cholesterol levels by formation of insoluble cholesterol-complexes, reducing the risk of cardiovascular diseases (Muzquiz et al., 2012). Furthermore, phenolic compounds such as phenolic acids, flavonoids (anthocyanins included), and tannins, which display important functions in pulse seeds pigmentation, have been attracting interest due to their strong antioxidant activity (Giusti et al., 2017).

s observed with other pulses, lentils were reported as having positive physiologic activity, such as cholesterol and lipid lowering effects and reduced incidence of colon cancer and type-2 diabetes (Boye et al., 2010; Hefnawy, 2011; Roy et al., 2010; Shaheen et al., 2016). Considering its metabolomic profile, the dark-coloured lentil cultivars “verte du Puy” and “Black Beluga” should be highlighted, particularly considering their high content of peptides, triterpenes (mainly, α-amyrin), flavonoids, saponins, phenolics, fatty acids, and sphingolipids (Farag, Khattab, Maamoun, Kropf, & Heiss, 2019), high antioxidant and anti-inflammatory activity and lack of alkaloids (Farag et al., 2018).

The seed tegument is normally indigestible, besides having a bitter taste. As previously indicated, dehulling represents an effective way of improving the palatability and taste of some pulses, besides reducing tannins and phytic acid content (which are mainly present in the seed tegument). Likewise, the digestibility of dehulled components is significantly higher than that of the whole seed. The dehulling process has also technological advantages, as it reduces cooking (the seed tegument is impermeable), since it improves water uptake during cooking. 

Narrativer Review in wissenschaftlichem Journal

DOI: https://doi.org/10.1016/j.tifs.2019.08.022

Study: weak evidence

Lentil is one of the most important food legumes consumed widely throughout the world. Lentils are produced in diverse agroecological regions, such as Asia, North and South America, Africa, and Oceania. During the last two decades (2001–2020), world production of lentils increased by 107%, from 3.15 to 6.54 million metric tons. Canada leads lentil producing countries (with 44% share of the global output), followed by India and Australia having 18% and 8% share, respectively.

Lentils, like other pulses, contain numerous bioactive compounds, which have been generally classified as antinutritional factors (ANFs), due mainly to their adverse effect on nutrient digestibility and bioaccessibility if pulses are not fully cooked (Nosworthy et al., 2018; Sathe, 2012). These ANFs are trypsin, chymotrypsin and α-amylase inhibitors, total phenolics, tannins, flavonoids, saponins, lectins, phytic, and oxalic acid (Ganesan & Xu, 2017; Mirali et al., 2016; Roy et al., 2010; Ruiz et al., 1996; Sagratini et al., 2009). Many of these ANFs, once considered to have negative impact on health, are being recognized now as having significant health benefits, for example, possessing antioxidant activity and anti-inflammatory activity besides promoting the bioavailability of micronutrients, for example, zinc and iron (Campos-Vega et al., 2010; Sathe, 2012; Wiesinger et al., 2022). Alphonce et al. (2020) reported that optimized processing, especially, the application of heat and addition of organic acids (e.g., ascorbic acid) decreases the ANFs contents significantly.

The use of raw lentil flour should be avoided due to potential the development of rancid off-flavors produced through lipid oxidation and also intrinsic food safety implications considering the presence of ANFs.

Soaking in water is shown to effect substantial reduction in the phytate content, while the adding of sodium bicarbonate (NaHCO3) in soak water reduces phenolics and tannins (Dhull et al., 2020; Joshi et al., 2017; Martín-Cabrejas et al., 2009). Different processing methods (autoclaving, extrusion, germination or sprouting, roasting, and fermentation) have variable impacts on compositional and nutritional profile of lentils and can also reduce antinutrients' effects. Autoclaving improves digestibility due to interference of protein structure and gelatinization of starch (Dhull et al., 2022; Rehman & Shah, 2005). Extrusion processing is also reported to be effective in improving nutritional composition of lentils with optimum flavor and texture (Pasqualone et al., 2020). Ghumman et al. (2016) reported that germination/sprouting of lentil seeds has significant effect on compositional and nutritional quality, for example, an increase in crude proteins and a reduction in lipid, carbohydrates, phytic acid, and tannins contents.c

Legumes, including lentils, provide a number of numerous ecosystem benefits while also contributing to a sustainable cropping systems primarily via (1) their ability to contribute nitrogen (N) to the system by biological N2 fixation; (2) diversification of cropping systems (including crop rotation) that results in reduced incidence of disease, pest, and weed, thus, potentially increasing biodiversity; and (3) a significantly reduced fossil energy use in plant production/protection practices ..

Narrativer Review in wissenschaftlichem Journal

DOI: 10.1016/j.tifs.2019.08.022

Study: weak evidence

As phytate is water-soluble, a substantial
quantity is removed during soaking. Moreover,
this process also facilitates the action of natu-
rally occurring phytase in legumes and cereals
grains. 

Several cereal and legume lectins may inhibit
the growth of experimental animals due to reduc-
tion in the digestibility and biological value of
dietary proteins. They may impair the integrity of
the intestinal epithelium and so alter the absorp-
tion and utilization of nutrients. Dietary lectins
are therefore usually considered to be toxic and
antinutritional factors. However, many lectins
are non-toxic, such as those extracted from len-
tils, peas, faba beans, chickpeas, tomatoes and
other foods (Grant et al., 2000; Radberg et al.,
2001; Reynoso-Camacho et al., 2003).

Plant-derived toxins and allergens are abundantly
present and fundamentally unavoidable com-
pounds of our diet. Legumes and cereals contain
numerous deleterious compounds such as enzyme
inhibitors, lectins, phytates, oligosaccharides, and
phenolic compounds. Enzyme inhibitors may
reduce protein digestibility, while lectins may
reduce nutrient absorption. Phytic acid reduces the
bioavailability of minerals. Some phenolic com-
pounds diminish protein digestibility and bioavail-
ability of minerals, and galactooligosaccharides
cause flatulence. However, these compounds may
have protective and health benefits. Phytic acid has
antioxidant properties and protects against DNA
damage while phenolic compounds have antioxi-
dant as well as other important physiological and
biological properties. The Galactooligosaccharides
may encourage prebiotic activity in the human
body. Moreover, these compounds play a key role
in stimulation of the immune system, detoxifying
enzymes, regulation of lipid and hormone metabo-
lism, have antimutagen, antioxidant and antiangio-
genic effects, and can reduce the incidence of colon
cancer and tumor initiation. Lectin from kidney
bean seeds is known to inhibit HIV-1 reverse tran-
scriptase, an enzyme crucial for HIV replication.

The human body has developed built-in mech-
anisms through which most intrinsic or other
toxic substances are either converted into harm-
less compounds or excreted from the body.
However, plant-derived food sources must be
heat-treated before consumption in order to
diminish their toxic factors. These have little
influence after cooking.
Considering the health benefits of secondary
metabolites, these may be marketed as functional
and nutraceutical ingredients. Future research
should be focused on isolation, characterization,
immunological responses and their heath benefit
issues.

Several cereal and legume lectins may inhibit the growth of experimental animals due to reduction in the digestibility and biological value of

dietary proteins. They may impair the integrity of the intestinal epithelium and so alter the absorption and utilization of nutrients. Dietary lectins

are therefore usually considered to be toxic and antinutritional factors. However, many lectins are non-toxic, such as those extracted from len-

tils, peas, faba beans, chickpeas, tomatoes and other foods (Grant et al., 2000; Radberg et al.,2001; Reynoso-Camacho et al., 2003).

Narrativer Review

DOI: 10.1002/9781118474563.ch16

Study: weak evidence

 In a previous study, the proteome profile of low molecular weight (<50 kDa) proteins of seven different lentil cultivars developed by Bangladesh Agricultural Research Institute was demonstrated, and a total of 2873 peptides were identified, corresponding to 180 unique proteins. Of these, >24% were reported to be identified as lentil allergens (Shaheen et al., 2019). World health authorities recommend that people maximize their protein intake from plant sources (such as legumes) and reduce protein intake from animal sources, as increased vegetable protein intake is positively associated with reduced both cardiovascular disease-related deaths and all-cause mortality (Chelladurai & Erkinbaev, 2020). 
 
 Germination plays an important role in reducing nonnutritive compounds in legumes and increasing the levels of available carbohydrates, dietary fiber, and other components, and germination is one of the most common and effective processes to improve the nutritional quality of legumes (Vidal-Valverde et al., 2002). Cooking lentils by boiling improves taste and flavor, and also increases the bioavailability of nutrients (Pal et al., 2017; Xu & Chang, 2008).
 The presence of high levels of dietary trypsin inhibitors from legumes has been reported to cause reductions of up to 50% in protein and amino acid digestibility in living systems (Gilani et al., 2005). It has been reported that the majority of the toxic and antinutrient effects of harmful compounds can be prevented by germination, sprouting, boiling, autoclaving, fermentation, genetic manipulation, and other processing methods (Siddhuraju et al., 2002; Soetan, 2008).
 Epidemiological studies have shown that pulse consumption is inversely proportional to the incidence of various chronic diseases such as coronary heart disease, type II diabetes mellitus, cardiovascular diseases, cancer, and aging (Villegas et al., 2008). It has been stated that the prevention and treatment of degenerative diseases are related to the antioxidant compounds in lentil sprouts (Salas-Perez et al., 2018; Zou et al., 2011). In addition, it has been reported that germinating lentils have properties against arterial hypertension (Torres-Acosta & Calvo-Araujo, 2011). With the fresh consumption of lentil sprouts, carbohydrates, fibers, vitamins, minerals, and high amounts of phytochemicals with antidiabetic, anti-inflammatory, anticancer, antihypertensive, and antioxidant activities are taken into the body (Dziki et al., 2015). Limited studies were carried out on physicochemical and bioactive properties, fatty acids, phenolic compounds, and mineral contents of raw, germinated, and boiled lentil seeds. The aim of this study was to investigate the effect of germination and boiling on oil content, total phenol, flavonoid, antioxidant activity, phenolic compounds, fatty acids, and mineral contents of raw, germinated, and boiled lentil seeds
 
 The protein content of germinated and boiled lentils increased compared to the control sample.
  The total phenol and flavonoid contents of the lentils of the control samples were higher than those of the germinated and boiled ones. Enzyme activity and applied temperature during germination and boiling, respectively, caused a decrease in the amount of bioactive components of lentil seeds. 
  
  Since lentils have high phenolic content, antioxidant activity is also high. Therefore, it has been reported that there is a linear relationship between the phenolic component and antioxidant activity values of lentil seeds (Xu & Chang, 2007). 
  
Laborstudie in wissenschaftlichem Journal

DOI: 10.1111/1750-3841.16099

Study: weak evidence

(Chaudhary and Tremorin 2020). It has been reported in a recent study by Chaudhary and Tremorin (2020) that when cooked lentil puree was used in the lean beef burger formulation, ~33% and 26% reductions in environmental food print and cost were observed, respectively.

However, the existence of unwanted flavor compounds, raffinose family oligosaccharides, antinutritional factors (ANFs) (e.g., saponins, phytic acid, tannins, lectins, and protease inhibitors), and the allergenic proteins, respectively, results in a “beany flavor,” gastrointestinal discomfort and flatulence, adverse nutritional effects (e.g., reduced protein digestibility and nutrient absorption), and allergenic reactions.

The EAA contents of lentil proteins were found to be comparable to those of dairy proteins, and it has been stated that the EAA contents of lentil proteins exceed the recommended daily intake of FAO/WHO (FAO/WHO 1991) for healthy adults (except cysteine and methionine amino acids) (Alrosan et al. 2022). Bioactive peptides, another functional component in lentils, have health-promoting abilities such as reducing inflammation and blood pressure and supporting the immune system (Faris, Takruri, and Issa 2013).

In addition, the dietary fiber, resistant starch, and oligosaccharides of lentils have proven health benefits (e.g., hypocholesterolemic, anticancerogenic, antitumor, hypoglycemic, and antimicrobial effects in human body) associated with their significant contribution to gastrointestinal health (Ganesan and Xu 2017). They can regulate bowel function and modulate the structure and activities of the gut microbiota, which stimulates the growth of probiotic bacteria (Ganesan and Xu 2017).

Saponins, the bioactive compounds of lentils, have hypocholesterolemic, hypoglycemic, anti-inflammatory, and antimicrobial effects that positively affect human health (Ganesan and Xu 2017; Del Hierro et al. 2020; Mustafa et al. 2022). The hypocholesterolemic effect of saponins can be explained by two mechanisms. One of them is the prevention of cholesterol absorption from the small intestine by forming an insoluble saponin-cholesterol complex, and the second mechanism is the solubilization of cholesterol in the small intestine (Mustafa et al. 2022). Saponins inhibit the production of proinflammatory cytokines and inflammatory enzymes and the degradation of IκB-α, which results in anti-inflammatory effect (Conti et al. 2021). Del Hierro et al. (2020) stated that fermentation of saponin-rich fractions from red lentils by human gut microbiota modulated the growth of specific intestinal bacteria, mainly lactic acid bacteria and Lactobacillus spp., via the transformation of saponins into sapogenins (soyasapogenol B), resulting in antimicrobial activity.

Additionally, the phenolic compounds in lentils have antioxidant activity which can potentially reduce the incidence of various cancers.

Narrativer Review in wissenschaftlichem Journal

DOI: 10.1002/leg3.70000

Study: weak evidence

Grain legumes or pulses, including lentil (Lens culinaris Medik), have gained increasing popularity among consumers and food processors in recent years. This trend has been driven by the consumers opting for plant-based proteins and environmentally sustainable food sources. Global production of lentils has more than doubled since 2001 (from 3.15 to 6.58 million metric tons in 2020), which signifies the commercial importance of this nutrient-dense legume. As per the USDA's nutrients data (2022), lentil contains 24.6% protein, 63.4% carbohydrates, 2.7% ash content, and 1.1% total fat. High amount of dietary fiber, slowly digestible starch and potassium, and low sodium in lentil align well with consumer choices for healthy foods. Many studies have reported on the health benefits of consuming lentils, especially being effective in reducing various health conditions, such as hypertension, cardiovascular diseases, diabetes mellitus, and cancer. The relatively higher protein and lower carbohydrates content of lentil compared with cereal grains can help in expanding the utilization of lentils and lentil-based ingredients to develop new products. Combined with high dietary fiber, resistant starch, and bioactive polyphenolic content, the demonstrated nutritional benefits can fill the ever-increasing demand for plant-based proteins well beyond traditional consumption of lentils in developing countries. This article reviews the composition and nutrient profile of raw and processed lentils, effect of various processing methods on composition and nutrient profile, and health benefits of lentils.

Narrativer Review in wissenschaftlichem Journal

DOI: 10.1002/leg3.156

Study: weak evidence

Although phytic acid and its mineral salts have
beneficial effects on human health such as decreasing the risk
of heart disease, colon cancer, and renal stone formation, its
role as a food antinutrient has been a major concern for
mineral bioavailability for human populations that are mainly
dependent on cereals and legumes. 

Lebensmittelanalytische Studie in wissenschaftlichem Journal

DOI: 10.1021/jf901636p

Study: weak evidence