Nutritional potential of new oat and spring wheat cultivars

Kshitiz Pokhrel

Doctoral thesis

Abstract:

Based on global grain production, wheat (Triticum aestivum L.), and oats (Avena sativa L.) hold prominent positions as essential sources of nutrition for both humans and animals. Interestingly, wheat ranks as the second main grain crop, serving as a staple food providing essential nutrition to billions. Similarly, oats rank as the sixth main grain crop, holding a unique position among cereals. Previously regarded primarily as horse feed, oats have now gained significant attention not only in the public and food industry but also in the pharmaceutical sector. Their nutritional potential continues to play a vital role in global diets, making them promising cereals in sustaining humanity’s well-being. The overall aim of the thesis was to highlight the nutrition potential of oat and spring wheat cultivars, by investigating their fat content, fatty acid composition, carotenoid content, tocol (vitamin E) content, and phenolic compounds. Oat is a rich source of fat, and the fatty acid composition of oats is desirable for human consumption. The lipid component of oats has nutritional, medical, and technological potential. Consequently, the fat content and the fatty acid composition of oats play a crucial role in determining the grain’s energy and significantly impact overall nutritional quality. In our research, we have investigated 38 diverse genotypes of oats, including hulled and naked Canadian and European varieties. Additionally, we have also evaluated six oat varieties registered between 2011 and 2014 and eight yellow oat varieties. These oats are commonly cultivated worldwide. The lipid of milled oat grains was extracted using petroleum ether. Fat content was determined through a gravimetric method, after drying at 103 ± 2 °C until a constant weight was achieved. After preparing fatty acid methyl esters from fresh fat, the fatty acid composition was analyzed using GC-MS. Finally, the proportions of fatty acids were calculated using the area normalization method, and the results are expressed as relative percentages of each fatty acid. According to our results, the lipid content of Canadian and European oat genotypes was 2.9 – 6.29% and 3.52 –9.51% respectively. Notably, the French genotype, Ivore, presented the highest quantity of oleic acid and total MUFA content. Additionally, the Russian genotype Lidya contained the highest palmitic acid. This study found that the PUFA/SFA ratio was 1.39 – 2.05 in Canadian genotypes and 1.21 – 2.24 in European oat genotypes. Importantly, Canadian oat genotypes have a higher proportion of unsaturated fatty acids compared to European genotypes, suggesting they offer a healthier choice for consumers. This study’s uniqueness lies in its illustration of how diverse oat genotypes can influence the fat content and fatty acid composition even if they are grown under the same climatic condition and within a single season. When comparing the fat content of naked and hulled oats, it was found that naked oats contained a higher amount. Moreover, husk removal led to changes in the fatty acid compositions in oats, resulting in an increase in PUFA and a decrease in MUFA. Furthermore, dehulled oats, after husk removal, contained a higher fat compared to hulled oats. Consequently, husk removal led to a reduction in the proportion of oleic acid and an increase in linoleic acid. Additionally, the result of our study has also found the major fatty acids of naked oats and hulled oats are the same but the composition is different. Additionally, our research reveals that oat lipids have low atherogenicity and thrombogenicity indices, indicating their potential health benefits. The findings of these studies highlight the dietetic significance of new oat cultivars hold for both human food and animal feed. Due to its relatively higher fat content among cereals, oats are susceptible to oxidation reactions. This vulnerability is mainly attributed to the presence of a high proportion of MUFA and PUFA

Abstract:

in oat oil. So, we examined the oxidative stability of crude oat lipids together by comparing the two stability tests Rancimat and the Schaal oven test. Additionally, we determined whether tocols, known for their antioxidant properties, could extend the stability of oat oils. The outcomes of the Schaal oven test were remarkable, with all samples demonstrating an induction period of more than 50 days. On the other hand, Rancimat test, the induction period of Saul was longer than others, 9.02 h at 100°C. Additionally, our study confirmed that oats indeed contain significant tocols (Sanitini with 155.2 mg/kg of oil). Our study has found that the highest tocol content in oats correlates with greater stability in Rancimat test. On the other hand, wheat is a highly demanded cereal throughout the globe. A substantial portion of the global population relies on daily diets composed of food made from wheat. During the past few decades, various publications have suggested consuming whole grain food products due to their positive health impacts. Therefore, our study aims to analyse the nutritional composition of coloured spring wheats in comparison with winter wheats, with a particular focus on bioactive phytochemicals, including carotenoids, phenolic compounds, and tocopherols. Coloured wheats are carotenoid-rich, mainly lutein (over 80% of carotenoids). Ferulic acid dominates among analyzed colored wheat varieties. Beta-tocotrienol is the main vitamin E form. Among the six coloured wheat varieties studied, we found 30-36 mg/kg DW of tocols, 5-21 mg/kg DM of carotenoids, and 94-197 mg/kg of phenolic compounds in the samples. Spring wheat has higher tocols and carotenoids content, while winter wheat has more phenolic compounds. The potential health advantages of consuming whole grains could stem from the phytochemicals within them. Most of the wheat grains are consumed in the form of bread/bun, which is popular in every part of the world and constitutes a significant portion of daily diets. Sensory analysis of buns is essential as it allows to us understand how these phytochemicals in coloured wheat may influence the sensory attributes of final products. Linear unstructured graphical scale was used for sensory profile evaluation of descriptors focused on overall appearance liking, pleasantness of colour, the intensity of colour, overall taste liking, overall intensity of taste, intensity of sweet taste, intensity of salty taste, and overall sample acceptance. The results showed variations in preferences and perceptions among the assessors for different bun samples. AF Oxana (winter wheat) bun received higher scores in most attributes, while AF Jumiko had the lowest scores in several attributes. Tercie (spring wheat) bun scored highest for overall appearance liking. Last but not least, winter wheat affects colour and appearance attributes, while spring wheat influences taste attributes.

Keywords

oil stability, lipid composition, tocols, wheat, carotenoids, phenolic compound, oat

Jazyk práce: English

Datum vytvoření / odevzdání či podání práce: 24. 8. 2023

Obhajoba závěrečné práce

• Vedúci: prof. Ing. Lenka Kouřimská, Ph.D.
• Oponent: Ivana Capouchová, CSc., prof. Ing., Marcela Sluková, externi, Magdalena Franczyk-Żarów, externi

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Doctoral programme:
Agricultural Chemistry