Lentils: the world’s protein source

#SmartProtein

Lentils, together with chickpeas, fava beans, and quinoa form the ‘fantastic four’ alternative protein sources within the Smart Protein project. These crops, together with side streams from beer and pasta production, comprise the raw materials for developing a new generation of foods that are cost effective, resource efficient, and nutritious. But what makes lentils one of the chosen ones? Read on, and get some insights into the secret life of lentils.

By Basti Rückert

What makes lentils ‘smart’

Lentils contain an average of 26% high-quality protein. Together with other grain-legume seeds, they are the main source of dietary protein for over a billion people. On top of that, they have great potential for use in novel plant-based foods. The protein in lentils helps to increase nutritional value, while lentils also enable better processing properties and gustatory qualities.1)Khazaei, Hamid; Subedi, Maya; Nickerson, Mike; Martínez-Villaluenga, Cristina; Frias, Juana; Vandenberg, Albert (2019): Seed Protein of Lentils: Current Status, Progress, and Food Applications. In: Foods (Basel, Switzerland) 8 (9). DOI: 10.3390/foods8090391 And, like other legumes, they are a perfect fit for crop rotation. Lentils are able to get around 85% of their required nitrogen from the atmosphere, which helps to improve the fertility of the soil for other crops – and means that farmers can save money on fertilizers while also having another product to sell.2)2 Kabir, Md. Humayun; Das, Pronabananda; Islam, Md. Monirul; Hossain, Md. Belal; Mamun, A. N. K.; V., Rallos Roland (2019): Effect of different doses of nitrogen on nitrogen fixation and yield of lentil using tracer technique. In: Biol. and Pharm. Sci. 6 (3), S. 69–75. DOI: 10.30574/gscbps.2019.6.3.0027.
Additionally, lentils have such a strong nutritional composition that they are an important element in helping to overcome malnutrition.

Tacking world hunger

Lentils are a staple crop, especially in regions where many people suffer from poverty. They contain essential macro- and micronutrients, especially iron and zinc, as well as vital vitamins (E and K, among others) that are less available in other common foods. Iron and zinc are particularly bioavailable due to the very low levels of phytic acid in lentils. (This acid normally has the effect of binding iron and zinc and hinders their absorption in the small intestine.)3)Thavarajah, Dil; Thavarajah, Pushparajah; Wejesuriya, Asoka; Rutzke, Michael; Glahn, Raymond P.; Combs, Gerald F.; Vandenberg, Albert (2011): The potential of lentil (Lens culinaris L.) as a whole food for increased selenium, iron, and zinc intake: preliminary results from a 3 year study. In: Euphytica 180 (1), S. 123–128. DOI: 10.1007/s10681-011-0365-6., 4)Bhatty, R. S. (1988): Composition and Quality of Lentil (Lens culinaris Medik): A Review. In: Canadian Institute of Food Science and Technology Journal 21 (2), S. 144–160. DOI: 10.1016/S0315-5463(88)70770-1. In addition, lentils contain phytonutrients which have anti-inflammatory, antioxidant, and anticarcinogenic effects.5)Faris, Mo’ez Al-Islam Ezzat; Takruri, Hamed Rabah; Issa, Ala Yousef (2012): Role of lentils (Lens culinaris L.) in human health and nutrition: a review. In: Mediterranean Journal of Nutrition and Metabolism 6 (1), S. 3–16. DOI: 10.3233/s12349-012-0109-8. It has also been demonstrated that consuming pulses improves serum-lipid profiles and decreases several other risk factors for cardiovascular diseases, such as blood pressure and inflammation.6)Mudryj, Adriana N.; Yu, Nancy; Aukema, Harold M. (2014): Nutritional and health benefits of pulses. In: Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme 39 (11), S. 1197–1204. DOI: 10.1139/apnm-2013-0557.
Although lentils combine all these features in one small seed, they are missing some essential amino acids. However, most people consume lentils together with grains (usually rice), which provides a cheap and wholesome meal that contains all the essential amino acids.7)van Vliet, Stephan; Burd, Nicholas A.; van Loon, Luc J. C. (2015): The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. In: The Journal of nutrition 145 (9), S. 1981–1991. DOI: 10.3945/jn.114.204305. Examples include Indian dhal with rice or naan, and lentil soup/stew with different kinds of bread (such as injera in Ethiopian and Eritrea, and lahoh in Somalia), as eaten in many parts of Africa.8)Bundeszentrum für Ernährung (2020): Hülsenfrüchte: Gesund essen. Was macht Hülsenfrüchte so wertvoll? Link. Last access: 03.12.2020. But where do these little bundles of energy come from?

The ancient pulses from the ‘Old World’

Cultivated lentils (Lens culinaris) originally come from Western and Central Asia. They were one of the earliest crops domesticated in the ‘Old World’ (Africa, Asia, and Europe). 9)Cambridge Dictionary (2020): Definition of ‘the Old World’ from the Cambridge Academic Content Dictionary. Link. Last access: 03.12.2020., 10)Yadav, Shyam S.; McNeil, David L.; Stevenson, Philip C. (2007): Lentil. An Ancient Crop for Modern Times. Dordrecht: Springer. Link. Last access: 03.12.2020. Today, this legume grows in more than 70 countries and is consumed globally. In 2018, 6.3 million tonnes of lentils were produced around the world. The leading countries were Canada (33% of world total), India (25%), and the United States (6 %).11)Food and Agriculture Organization of the United Nations. (2020). Link. Last access: 03.12.2020. Lentil production has grown at more than 10% per year since 1960 (only soya-bean production has grown faster), probably because of their faster cooking time compared to other pulses. The lens-shaped seeds occur in many different colours (brown, black, green, white and gray), with or without patterns (spotted, marble, dotted), while the cotyledon colour can also vary (red, yellow, green).12)Nosworthy, Matthew G.; Neufeld, Jason; Frohlich, Peter; Young, Gina; Malcolmson, Linda; House, James D. (2017): Determination of the protein quality of cooked Canadian pulses. In: Food science & nutrition 5 (4), S. 896–903. DOI: 10.1002/fsn3.473., 13)Vandenberg, A.; Slinkard, A. E. (1990): Genetics of Seed Coat Color and Pattern in Lentil. In: Journal of Heredity 81 (6), S. 484–488. DOI: 10.1093/oxfordjournals.jhered.a111030. The type of variant determines its respective market share. The highest demand, globally, is for red and green lentils. Whereas red lentils are consumed nearly everywhere in the world, large green lentils, consumed as whole seeds, are mainly purchased in Europe, the Middle East, and South America.14)Erskine, William; Muehlbauer, Fred J.; Sarker, Ashutosh; Sharma, Balram. (2009): The lentil. Botany, production and uses. Wallingford: CABI. Link., 15)Khazaei, Hamid; Subedi, Maya; Nickerson, Mike; Martínez-Villaluenga, Cristina; Frias, Juana; Vandenberg, Albert (2019): Seed Protein of Lentils: Current Status, Progress, and Food Applications. In: Foods (Basel, Switzerland) 8 (9). DOI: 10.3390/foods8090391. However, there are so many more opportunities to use these pulses than just eating them as they are.

Versatile applications

Processing has a major impact on the characteristics of the final raw ingredients. Ultrafiltration, for example, results in a significantly higher protein content, with a higher protein solubility. Furthermore, lentil protein isolates generated using this method have superior characteristics in terms of fat- and water-binding capacity, gelling properties, and foam-formation capacity. Compared to traditional dairy proteins, lentil-protein isolate shows promising properties, a low carbon footprint 16)Alonso-Miravalles, L., Jeske, S., Bez, J., Detzel, A., Busch, M., Krueger, M., Wriessnegger, Clara L., O’Mahony, J. A.; Zannini, E. and Arendt, E. K. (2019): Membrane filtration and isoelectric precipitation technological approaches for the preparation of novel, functional and sustainable protein isolate from lentils. European Food Research and Technology, In Press. Link., and can be used to replace eggs in baked goods such as doughnuts and muffins or function as an emulsifier in salad dressings. When used as flour, lentils are involved in the production of gluten-free crackers.17)Khazaei, Hamid; Subedi, Maya; Nickerson, Mike; Martínez-Villaluenga, Cristina; Frias, Juana; Vandenberg, Albert (2019): Seed Protein of Lentils: Current Status, Progress, and Food Applications. In: Foods (Basel, Switzerland) 8 (9). DOI: 10.3390/foods8090391. In addition, a recent publication from Jeske et al. (2019) showed the high potential for lentil protein isolates in the production of milk substitutes. The formulation and characterisation of a lentil-based milk substitute was revealed, using different homogenisation and pasteurisation approaches. The resulting ‘lentil milk’ contained a protein content of 3.3 % (w/w), fat content similar to commercial cow’s milk, and sensory attributes comparable to other plant-based milks such as soya. Through high pressure homogenisation, solubilisation and surface hydrophobicity was increased, while the free sulfhydryl groups decreased. Furthermore, treatment with high temperatures resulted in a whiter colour of the final product. 18)Jeske, S., Bez, J., Arendt, E. K. and Zannini, E. (2019): Formation, stability, and sensory characteristics of a lentil-based milk substitute as affected by homogenisation and pasteurisation. European Food Research and Technology, In Press, doi: 10.1007/s00217-019-03286-0 This is great news and means that there will be even more lentil-based foods available soon, thanks to the Smart Protein project.
Right now a lot of lentils are still eaten unprocessed (although cooked). The world’s biggest consumer of unprocessed lentils is India. A typical Indian lentil dish is dhal, served with steamed rice or bread, and thinner lentil soups. They are easy to prepare, affordable – dhal is an accompaniment to nearly every meal and probably India’s number-one comfort food.19)Yadav, Shyam S.; McNeil, David L.; Stevenson, Philip C. (2007): Lentil. An Ancient Crop for Modern Times. Dordrecht: Springer. Link. Last access: 03.12.2020.

To make your own dhal, rinse lentils under running water, chop onion, garlic, ginger, bell pepper, and carrots. Sauté the vegetables, add spices, the lentils, and vegetable broth. Let it simmer until you are happy with the thickness of the dhal. While your dhal is cooking, the lentil flavour, as well as the accessibility and availability of nutrients, will continue to improve.20)Xu, Baojun; Chang, Sam K. C. (2008): Effect of soaking, boiling, and steaming on total phenolic contentand antioxidant activities of cool season food legumes. In: Food chemistry 110 (1), S. 1–13. DOI: 10.1016/j.foodchem.2008.01.045. Season the dhal and serve it warm with rice, potatoes, or naan.

Picky or not picky, that is the question

Today lentils grow successfully on all continents, except Antarctica. This global distribution is possible because they don’t require a lot of water (250 mm of annual rainfall is sufficient). In fact, lentil crops are susceptible to damage from flooding and waterlogging. In drought-affected regions, farmers often choose lentils for their fields.21)Erskine, William; Muehlbauer, Fred J.; Sarker, Ashutosh; Sharma, Balram. (2009): The lentil. Botany, production and uses. Wallingford: CABI. Link.22)Hamdi, A., Erskine, W. (1996): Reaction of wild species of the geneus Lens to drought. Euphytica 91, 173–179. DOI: 10.1007/BF00021067.Another important regulating variable for lentil cultivation is climate and temperature. As a cool-season crop, lentils require low temperatures during vegetative growth. That’s why, for example, in tropical and subtropical regions, sowing happens after the harvest of summer crops and the lentils are grown in winter. But, where the winters are too cold, sewing takes place in spring. As soon as the plant continues to develop and mature, it requires warm temperatures (optimum growth between 18-30°C).23)Roy C. D., Tarafdar S., Das M., Kundagrami S. (2012): Screening lentil (Lens culinaris Medik.) germplasms for heat tolerance. Trends Biosci. 5, 143–146. Link.24)Sita, Kumari; Sehgal, Akanksha; Kumar, Jitendra; Kumar, Shiv; Singh, Sarvjeet; Siddique, Kadambot H. M.; Nayyar, Harsh (2017): Identification of High-Temperature Tolerant Lentil (Lens culinaris Medik.) Genotypes through Leaf and Pollen Traits. In: Frontiers in plant science 8, S. 744. DOI: 10.3389/fpls.2017.00744. Lentils are not that picky about soil. They have adapted to different types and, so long as there is good drainage, they grow nearly everywhere, from sand to clay. Given a choice, however, they would prefer deep, sandy loam soils that are moderate in fertility.25)Erskine, William; Muehlbauer, Fred J.; Sarker, Ashutosh; Sharma, Balram. (2009): The lentil. Botany, production and uses. Wallingford: CABI. Link

Lentils: a sweet dessert?!

If you have a sweet tooth and are craving a sugary treat, the first things that come to your mind might be chocolate, muffins, pudding, cookies etc. It’s unlikely that many people will connect sweetness with lentils. But there are actually some interesting lentil-based desserts you should try out. Check out these lentil power bites, carrot lentil muffins, lentil brownies and lentil blondies.

All in all, lentils are a perfect fit for the Smart Protein project. They can be included in nearly every kind of dish, from savoury to sweet. They are able to grow nearly everywhere on the globe, which makes a local supply chain possible. In the future, this could help countries to be more independent in terms of protein and staples. Lentils are a great opportunity to prevent malnutrition and also offer the opportunity for creating new plant-based foods that are not only resource efficient, but also cost effective, nutritious, and delicious.

References

1 Khazaei, Hamid; Subedi, Maya; Nickerson, Mike; Martínez-Villaluenga, Cristina; Frias, Juana; Vandenberg, Albert (2019): Seed Protein of Lentils: Current Status, Progress, and Food Applications. In: Foods (Basel, Switzerland) 8 (9). DOI: 10.3390/foods8090391
2 2 Kabir, Md. Humayun; Das, Pronabananda; Islam, Md. Monirul; Hossain, Md. Belal; Mamun, A. N. K.; V., Rallos Roland (2019): Effect of different doses of nitrogen on nitrogen fixation and yield of lentil using tracer technique. In: Biol. and Pharm. Sci. 6 (3), S. 69–75. DOI: 10.30574/gscbps.2019.6.3.0027.
3 Thavarajah, Dil; Thavarajah, Pushparajah; Wejesuriya, Asoka; Rutzke, Michael; Glahn, Raymond P.; Combs, Gerald F.; Vandenberg, Albert (2011): The potential of lentil (Lens culinaris L.) as a whole food for increased selenium, iron, and zinc intake: preliminary results from a 3 year study. In: Euphytica 180 (1), S. 123–128. DOI: 10.1007/s10681-011-0365-6.
4 Bhatty, R. S. (1988): Composition and Quality of Lentil (Lens culinaris Medik): A Review. In: Canadian Institute of Food Science and Technology Journal 21 (2), S. 144–160. DOI: 10.1016/S0315-5463(88)70770-1.
5 Faris, Mo’ez Al-Islam Ezzat; Takruri, Hamed Rabah; Issa, Ala Yousef (2012): Role of lentils (Lens culinaris L.) in human health and nutrition: a review. In: Mediterranean Journal of Nutrition and Metabolism 6 (1), S. 3–16. DOI: 10.3233/s12349-012-0109-8.
6 Mudryj, Adriana N.; Yu, Nancy; Aukema, Harold M. (2014): Nutritional and health benefits of pulses. In: Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme 39 (11), S. 1197–1204. DOI: 10.1139/apnm-2013-0557.
7 van Vliet, Stephan; Burd, Nicholas A.; van Loon, Luc J. C. (2015): The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. In: The Journal of nutrition 145 (9), S. 1981–1991. DOI: 10.3945/jn.114.204305.
8 Bundeszentrum für Ernährung (2020): Hülsenfrüchte: Gesund essen. Was macht Hülsenfrüchte so wertvoll? Link. Last access: 03.12.2020.
9 Cambridge Dictionary (2020): Definition of ‘the Old World’ from the Cambridge Academic Content Dictionary. Link. Last access: 03.12.2020.
10, 19 Yadav, Shyam S.; McNeil, David L.; Stevenson, Philip C. (2007): Lentil. An Ancient Crop for Modern Times. Dordrecht: Springer. Link. Last access: 03.12.2020.
11 Food and Agriculture Organization of the United Nations. (2020). Link. Last access: 03.12.2020.
12 Nosworthy, Matthew G.; Neufeld, Jason; Frohlich, Peter; Young, Gina; Malcolmson, Linda; House, James D. (2017): Determination of the protein quality of cooked Canadian pulses. In: Food science & nutrition 5 (4), S. 896–903. DOI: 10.1002/fsn3.473.
13 Vandenberg, A.; Slinkard, A. E. (1990): Genetics of Seed Coat Color and Pattern in Lentil. In: Journal of Heredity 81 (6), S. 484–488. DOI: 10.1093/oxfordjournals.jhered.a111030.
14, 21 Erskine, William; Muehlbauer, Fred J.; Sarker, Ashutosh; Sharma, Balram. (2009): The lentil. Botany, production and uses. Wallingford: CABI. Link.
15, 17 Khazaei, Hamid; Subedi, Maya; Nickerson, Mike; Martínez-Villaluenga, Cristina; Frias, Juana; Vandenberg, Albert (2019): Seed Protein of Lentils: Current Status, Progress, and Food Applications. In: Foods (Basel, Switzerland) 8 (9). DOI: 10.3390/foods8090391.
16 Alonso-Miravalles, L., Jeske, S., Bez, J., Detzel, A., Busch, M., Krueger, M., Wriessnegger, Clara L., O’Mahony, J. A.; Zannini, E. and Arendt, E. K. (2019): Membrane filtration and isoelectric precipitation technological approaches for the preparation of novel, functional and sustainable protein isolate from lentils. European Food Research and Technology, In Press. Link.
18 Jeske, S., Bez, J., Arendt, E. K. and Zannini, E. (2019): Formation, stability, and sensory characteristics of a lentil-based milk substitute as affected by homogenisation and pasteurisation. European Food Research and Technology, In Press, doi: 10.1007/s00217-019-03286-0
20 Xu, Baojun; Chang, Sam K. C. (2008): Effect of soaking, boiling, and steaming on total phenolic contentand antioxidant activities of cool season food legumes. In: Food chemistry 110 (1), S. 1–13. DOI: 10.1016/j.foodchem.2008.01.045.
22 Hamdi, A., Erskine, W. (1996): Reaction of wild species of the geneus Lens to drought. Euphytica 91, 173–179. DOI: 10.1007/BF00021067.
23 Roy C. D., Tarafdar S., Das M., Kundagrami S. (2012): Screening lentil (Lens culinaris Medik.) germplasms for heat tolerance. Trends Biosci. 5, 143–146. Link.
24 Sita, Kumari; Sehgal, Akanksha; Kumar, Jitendra; Kumar, Shiv; Singh, Sarvjeet; Siddique, Kadambot H. M.; Nayyar, Harsh (2017): Identification of High-Temperature Tolerant Lentil (Lens culinaris Medik.) Genotypes through Leaf and Pollen Traits. In: Frontiers in plant science 8, S. 744. DOI: 10.3389/fpls.2017.00744.
25 Erskine, William; Muehlbauer, Fred J.; Sarker, Ashutosh; Sharma, Balram. (2009): The lentil. Botany, production and uses. Wallingford: CABI. Link