Soaking and fermentation of Lupin seeds to improve their nutritional properties

Abstract

Lupin seeds contain like many other grains and legumes the mineral inhibitor phytate. The presence of this anti-nutrient decreases the bioavailability of minerals such as zinc and iron. Especially people that live in areas where grains and legumes are the staple food source, as well as vegan and vegetarian groups, may be more vulnerable to mineral deficiencies. The presence of phenolic compounds in food can prevent cellular damage and act as an antioxidant. During this study, different methods were investigated to reduce the phytate content alongside an increase of total phenolic content, thereby increasing its nutritional profile. By dehulling, soaking, and fermenting the Lupin seeds the possible reduction of phytate and increase in total phenolic content were analyzed.
The seeds of the Lupin angustifolius plant have, with their low carbohydrate (<2%), high protein (36%) and fiber (35%) content, a strong nutritional profile that is comparable to other legumes like soybean and lentils. Not only the nutritional profile but also the ability to grown at many geographic locations, and the ability to convert atmospheric nitrogen into more usable forms that improve the soil quality make it an excellent growing crop with many benefits.
The Lupin seeds were bought from a local farmer in Skåne and divided into three batches. The seeds in method 1 were dehulled and submerged for 24-hour in water with a ratio of 1:3 (w/v) containing 0.5% NaCO3, followed by a 24-hour fermentation (37°C) with Lactobacillus plantarum 299v (1%). The seeds in method 2 ware dehulled and subjected to a 24-hour fermentation (37°C) with Lactobacillus plantarum 299v (1%). Where in method 3 whole lupin seeds were subjected to a 24-hour soaking period (ratio 1:3 w/v, 0.5% NaCO3) and 24-hour fermentation (37°C) with Lactobacillus plantarum 299v (1%).
During the fermentation, the pH, TTA (titratable acidity), protein, phytate, and total phenolic content were determined every 3 hours until 12 hours, and 24 hours after the initial start of the fermentation. Neither of the 3 methods was able to reduce the phytate content significantly (p=>0.05). Where results from ANOVA showed that only a combination of dehulling and soaking reduced the phytate content significant (p=<0.05) with 19%. On the other hand, the initial total phenolic content increased on average 3 fold, all the 3 methods showed to be significant (p=<0.05). The seeds that were dehulled, soaked and fermented (method 1) showed with 24% the biggest increase of phenolic compounds, the seeds that underwent only the dehulling and fermentation process (method 2) showed the smallest increase of 21%.
According to this study, a combination of dehulling, soaking, and fermentation does not significantly reduce the phytate content. Whereas a 3 fold increase is measured of total phenolic content after a 24-hour fermentation period.
For further research, it is possible to use a different Lactobacillus species and soak the seeds at a temperature that is more in line with the optimum temperature for phytase activation. Further, the phytase activity can be measured throughout the entire process to follow its changes.

Popular Abstract

While the trend nowadays increases the demand for new plant-based products, so is the demand to find new high nutritional food sources. One of these high-nutritional food sources and upcoming legumes is called Lupin. The Lupin seeds have a low carbohydrate, high protein, and high fiber content what makes them an attractive new food source. For many years people that live in all levels of society are fighting against mineral deficiencies. Especially people that have grains and legumes as their staple food source. Like many other legumes, Lupin contains nutrient absorption inhibitors such as phytate that decrease the bioavailability of several minerals. Lupin seeds also contain phenolic components, which are reported to promote anti-inflammatory conditions, and due to their anti-oxidation effect, they have the ability to prevent cellular damage through free-radical oxidation reactions. For this reason, the aim of this study was to investigate if it was possible to reduce this mineral inhibitor by dehulling, soaking, and fermentation of the seeds, in addition, to increase the total phenolic content and thus its nutritional profile.
To reduce phytate, three different methods were compared. In the first method, Lupin seeds were removed from their coat (dehulled) and subjected to a 24-hour soaking period followed by a 24-hour fermentation. In the second method, dehulled seeds were only subjected to a 24-hour fermentation. Where in the third method Lupin seeds were subjected to a 24-hour soaking period and 24-hour fermentation with their coat. None of these methods were able to significantly reduce the phytate content. Where only a combination of dehulling and soaking showed to reduce the phytate content significantly. On the other hand, all 3 methods showed a 3 fold increase in total phenolic content.
Although there are a lot of variables that can have an influence on the phytate content: type of bacteria used during the fermentation, initial concentration of phytate reducing enzymes, and the different types of Lupin seeds are just 3 of them. Changing these parameters can result in a decrease of phytate and can thereby have a positive effect on mineral absorption and mineral deficiencies. In addition, the higher concentration of phenolic compounds in the fermented lupin seeds presents a potential nutritional improvement in terms of antioxidants found in Lupin seeds and a study on their bioavailability and health effects is warranted.

• author: Hermans, Luut
• supervisor: Claudia Lazarte
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLGM01 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Lupin, Fermentation, Soaking, Dehulling, Phytate, Phenols, Total phenolic content, Protein, Food technology, Livsmedelsteknologi
• language: English
• id: 9015790
• date added to LUP: 2020-06-24 13:36:15
• date last changed: 2020-06-24 13:36:15