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In vitro and in vivo amino acid digestibility of selected soybean, oat and wheat varieties to identify targets with high protein quality and digestibility for future variety development

Principal Investigator: Lamia L’Hocine

Research Institution: Agriculture and Agri-Food Canada

Timeline: April 2013 – March 2018

Objectives:

  • Assess the effect of varietal differences of Canadian oat, soybean and wheat on protein quality and digestibility using the revised FAO recommendations.
  • Identify oat, soybean and wheat varieties with bioactive peptide and prebiotic potential that can be marketed for their promotion of digestive health.
  • Study the functional properties of varieties with the most promising traits to identify targets for future variety development.

Impacts:

  • This project delivered new information on the composition, physiochemical and nutritional properties of 30 oat, 26 soybean and 30 wheat varieties.
  • Data from the growing location (GxE) subset of samples showed the important impact environmental conditions have on the nutritional profile of the crops tested. This information, including amino acid profiles and protein nutritional quality scores, can be used in nutritional considerations for future variety development.
  • The project was able to evaluate the oat, soybean and wheat varieties using the new DIAAS method and compare the results to the previous FAO recommended methods for assessing protein quality. The in vitro method offered a more rapid and affordable option compared to the current recommended in vivo bioassays, or former PDCAS testing methods.
  • Improvements of an in vitro human digestion model were made by the development of an ileal digestion step to assist with the prediction or true ileal protein and amino acid digestibility. This is now the new recommended method for protein quality assessment as it measures amino acid digestion at the end of the small intestine rather than the overall digestibility of a protein over the total digestive tract.
  • This project provided the agricultural industry with crucial information and science-based knowledge of protein nutrient, biological and health properties.
  • The study showed that the growth of selected probiotics is affected by the type of grain and by cooking and that beyond the nutrition value, grains can also have prebiotic effects that can be modified by processing.
  • The project results will allow plant breeders to develop markers for screening and develop crop varieties with distinctive value-added health benefits, resulting in leading edge marketability for domestic and international markets, opening the door for Canadian growers and processors to capture new and growing global needs for functional foods.

Scientific Summary:

Results:

Evaluation process

A selection of Canadian oat, soybean and wheat varieties with high and low protein content was acquired from plant breeders to:

  1. Assess the nutritional quality of the selected varieties for amino acid composition, digestibility using an in vitro method (lab system to model human digestibility), and the calculation of the new DIAAS.
  2. Perform in vitro, in vivo (animal digestibility testing) protein and ileal digestibility tests on selected varieties.
  3. To simulate real-life samples of the processed products, raw and uncooked flours were also analyzed to assess the impact of processing (thermal treatment) on protein and amino acid digestibility.

New information

This research project delivered new information on the composition, physicochemical and nutritional properties of 30 oat, 26 soybean and 30 wheat varieties.

The project also worked with oat varieties grown in different locations to evaluate the gene (G) x environment (E) (variety x location) effect, collecting valuable data on the impact of these factors on their nutritional properties. Data obtained from the growing location (GxE) subset of samples shows the important impact environmental conditions have on the nutritional profile of the crops tested. The results of this information, including amino acid profiles and protein nutritional quality scores, can be useful in nutritional considerations for future variety development.

The project was able to evaluate the oat, soybean and wheat varieties using the new DIAAS method, and compare the results to the previous FAO recommended methods for assessing protein quality.  The in vitro method offers a more rapid and affordable option when compared to the currently recommended in vivo bioassays, or former PDCAS testing methods.

Results comparison

The cost of in vivo testing is significantly higher than in vitro. Both tests were performed through the project to assess and identify a more streamlined, cost-effective research process for future projects assessing digestibility. 

The evaluation of the efficacy of affordable and convenient in vitro methods was conducted to accurately estimate protein nutritional quality when compared to the FAO’s recommended in vivo method.

Selected varieties with higher protein quality and digestibility were identified and subjected to both in vitro and conventional in vivo protein digestibility tests.

Improvements of an in vitro human digestion model were made by the development of an ileal digestion step to assist with the prediction of true ileal protein and amino acid digestibility, which is now the new recommended method for protein quality assessment. Ileal digestion measures amino acid digestion at the end of the small intestine rather than the overall digestibility of a protein over the total digestive tract.

Thermal processing evaluation

For the first time, information on protein quality and protein and amino acid digestibility of processed oat, soybean and wheat products is available as a result of the thermal testing conducted through the project. Final food products typically undergo thermal treatments like cooking, baking and boiling before being eaten and digested. Thermal process testing was used to simulate common food products from selected varieties of each crop to determine if protein quality and digestibility changed through the thermal process.

A preliminary evaluation of the bioactive and prebiotic potential was undertaken for selected oat, soybean and wheat varieties, which can be marketed for their promotion of digestive health. 

The research project also trained several national and international highly qualified personal, including four post-doctorate researchers and three undergraduate trainees.

Successes

The results of this project will lead to improvements in the nutritional quality of Canadian oat, soybean and wheat. New data on the nutritional quality of 30 wheat varieties, 30 oat varieties and 26 soybean varieties were generated on the basis of amino acid composition and in vitro digestibility. In general, despite variations in certain amino acid concentrations between the studies varieties, similar amino acid distribution patterns were observed from one cultivar to another. The highest variability was observed among oat varieties, and a strong effect of growing location on amino acid concentrations was also observed on a “per gram of flour” and a “per gram of protein” basis. These results suggest an impact not only on the grain protein content, but also on its composition.

As a result of the research project, potential amino acid profiles and amino acid digestibility coefficients can now be evaluated and used as a strategy to screen and classify oat, soybean and wheat varieties for distinctive protein quality traits.

Protein quality isn’t just a nutritional aspect, it’s also functional, offering health benefits like antioxidant peptides. The project results now provide researchers with additional information to evaluate oat, soybean and wheat varietal influences and thermal treatments on protein bioactive properties for their potential incorporation in functional and nutraceutical foods. A process to evaluate grains for prebiotic potential to market the products for the promotion of digestive health is now available as a result of this research project.

Oat, soybean and wheat are important economic crops to Canadian growers, seed companies, processors and exporters. This research work provides the agricultural industry with crucial information and science-based knowledge of protein nutrition, biological and health properties. The study revealed that the growth of selected probiotics is affected by the type of grain and by cooking. The project research suggests that beyond the nutrition value, grains can also have prebiotic effects that can be modified by processing. Consumer interest in the effects of food and food components on health continues to grow, offering significant potential for value-added grains by identifying and enhancing the functional components.

Future Opportunities

This research will allow plant breeders to develop markers for screening and develop crop varieties with distinctive value-added health benefits, resulting in leading edge marketability for domestic and international markets. This information also opens opportunities for Canadian growers and processors to capture new and growing global needs for functional foods. The profitability and sustainability of the Canadian agri-food industry is also enhanced with the ability to provide highly nutritional and functional quality protein sources to the market.

A new complementary but different research project is already underway, studying the impact of oat varieties on the generation of antioxidant peptides during in vitro simulated human digestion.

External Funding Partners:

This research activity was part of the Canadian Field Crop Genetics Improvement Cluster led by the Canadian Field Crop Research Alliance (CFCRA).

Funding for this project was provided in part by Agriculture and Agri-Food Canada through the Growing Forward 2 (GF2) AgriInnovation Program and in part by CFCRA members. Grain Farmers of Ontario is a founding member of the CFCRA.

Project Related Publications:

A. J. Hernández -Alvarez, A. Hernández -Jabalera, S. Ribéreau, A. Achouri, Y. Arcand and L. L’Hocine. 2016. Protein Nutritional Quality, Amino Acid Profile and Digestibility of 30 Canadian Wheat Varieties. Poster presentation at: The 107th AOCS Annual Meeting & Expo., Salt Lake City, Utah.

A. Hernández -Jabalera, A. J. Hernández -Alvarez, S. Ribéreau, A. Achouri, Y. Arcand and L. L’Hocine. 2016. Assessment of Protein Nutritional Quality in Canadian Soybean Varieties: Relation with Nutritional and Non-nutritional Component. Poster presentation at: The 107th AOCS Annual Meeting & Expo., Salt Lake City, Utah. Alberta N.A. Aryee, Chi B. Do and Yves Arcand. 2015. Assessing the Composition, Physicochemical Properties and Digestibility of Oat to Predict Nutritional Quality. Poster presentation at: Food Structures, Digestion and Health, 3rd International Conference, Wellington, New Zealand.

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