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On Focus: Legumes

Legumes are celebrating a comeback in human nutrition, with the market rapidly growing since the 2000s. Daniel Hefft of Weetabix Ltd discusses how they can be used in the food prodcution process. 

In Europe, legumes are celebrating a comeback in human nutrition, with the market rapidly growing since the 2000s. Although they have been around in Europe for a long time, they have nearly been forgotten as an important source of energy. Prominent representatives are peas, buckwheat, chickpeas, lentils, but also groundnut and alfalfa. Legumes constitute approximately 7% of flowering plant species and are thus the third-largest plant family. Archaeological evidence traces the first use of legumes back to the time of 3300BC in India (Punjab).

India is still the key producer of legumes and accounts for about 25% of the worldwide production. However, Asia is the overall main producer of legumes. Other important producers are Argentina and the USA (mainly through soy bean for animal feed). The annual total production lies around 70 million tonnes. In general, legumes still form an important part of human nutrition in the developing world and deliver there about 10% of the daily energy intake.

The 2005 Dietary Guidelines for Americans recommend an intake of 3 cups (6 servings) of legumes per week for people with a caloric consumption of around 2,000 kcal/day and the Indian government suggest about 40g per day. The consumption of legumes is linked to several health benefits. Legumes bring higher satiety levels, a decrease of glycaemic index, and are high in fibre and protein, which fit in with the current trend of foods that are high in protein. Further, they are also rich in vitamins, such as folic acid, thiamine, niacin, and they are also rich in minerals.

Legumes are ecologically sustainable when comparing their environmental footprint with breeding of animals. Legumes require about 50 litres of water per kilogram whereas 1kg of meat requires between 5,000 to 20,000 litres water. Likewise, farming 1 kilogram of wheat requires about 10 to 80 times more water than legumes. Another important aspect is that farming legumes does not leach the soil, but instead they function as a natural fertiliser. This is due to microbes at the root system (rhizobia) that are a natural nitrogen fertiliser (nitrogen fixation function).

However, farming legumes is still very challenging in Europe. Legumes generally have lower yields than non-legume crops. A study published in 2015 [1] indicates that risk premiums are likely to be higher in Europe for most legumes compared to major non-legume species, such as wheat or corn. The study also showed that yields in America had lower risks in variation, meaning they have a more reliable crop year on year. One explanation might be the use of genetically modified legumes (e.g. GM soya), different climate conditions and a lack of knowledge of legume farming in Europe. These obstacles can be overcome with more research in this field and a better understanding of farming methods for legumes in Europe.

Legumes have a great potential to be used more in the food and beverage industry. Application fields are the production of meat substitutes, snack products, baked goods, pasta, breakfast cereals, vegan ice cream and as processing aids in the beverage industry (alternative clearing agent for gelatine in drinks to make them suitable for vegetarians).

Several technologies can be used for processing legumes. After harvesting, the crops get cleaned, peeled, ground and processed further. This is often done with similar equipment used in wheat and rice processing.

To produce meat-like and fibrous structures, technologies such as high moisture extrusion is an efficient process [2]. High moisture extrusion is applicable for high gel forming proteins and is based on the formation of disulphide-bonds. High moisture extrusion works optimally with legumes that have a protein content of 65% and above.

Classic extrusion can be used when aiming for the manufacture of products like snack food articles (e.g. puffed shapes), pasta and breakfast cereals. The main difference between both technologies is only the amount of water addition into the process.

To produce fruit juices, gelatine can be directly replaced with legume proteins such as pea proteins without interfering with the fining process. Pea proteins are first added to the juices, followed by the addition of bentonite. As a last step, colloidal silica is added. In addition to the last step, enzymes (pectinases, glucanases, etc.) can be used to increase the filterability as well as activated carbon for the removal of undesirable colouring and odorous substances.

Legumes bear a great potential for a broader application in the future. It is necessary to gain a better understanding of farming these crops, of the health benefits associated with legumes, and alternative sources of proteins. This will help companies to develop products that are unique and could potentially bring a lead over competitors. Legumes could be cultivated in countries with limited access to water or those with poor soils. They can also be used to naturally improve soils that have been leached and ensure the nutrition of populations with a source of protein. Legumes are a key ingredient for the development of vegetarian and vegan alternatives to many products.

 

Daniel I. Hefft, Process Development Engineer, Weetabix Ltd

 

References

  1. Cernay C, Ben-Ari T, Pelzer E, et al (2015) Estimating variability in grain legume yields across Europe and the Americas. Sci Rep 5:11171. doi: 10.1038/srep11171
  2. Osen R, Toelstede S, Wild F, et al (2014) High moisture extrusion cooking of peaproteiisolates: Raw material characteristics, extruder responses, and texture properties. J Food Eng 127:67–74. doi: 10.1016/j.jfoodeng.2013.11.023



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