CHEMICAL COMPOSITION AND NUTRITIONAL QUALITY OF WHEAT GRAIN

ABSTRACT

Wheat (Triticum aestivum) is one of the main food sources worldwide and plays a key role in global food security. Its grain is rich in starch, proteins, lipids, dietary fiber, vitamins, and minerals. In recent years, deficiencies of iron, zinc, and selenium have become significant public health concerns. Therefore, improving the nutritional quality of wheat, particularly through biofortification, is highly important. This study analyzes the chemical composition of wheat grain and discusses genetic and agronomic strategies aimed at enhancing its nutritional value.

АННОТАЦИЯ

Пшеница (Triticum aestivum) является одним из основных источников питания населения мира и играет важную роль в обеспечении глобальной продовольственной безопасности. Зерно богато крахмалом, белками, липидами, пищевыми волокнами, витаминами и минералами. В последние годы дефицит железа, цинка и селена стал актуальной проблемой здравоохранения. В связи с этим повышение пищевой ценности пшеницы, особенно посредством биофортификации, имеет важное значение. В работе проанализированы химический состав зерна и стратегии улучшения его питательных свойств с использованием генетических и агрономических методов.

Keywords: wheat, chemical composition, protein, starch, biofortification, micronutrients, nutritional quality.

Ключевые слова: пшеница, химический состав, белок, крахмал, биофортификация, микроэлементы, пищевая ценность.

INTRODUCTION

Wheat (Triticum aestivum) is one of the oldest and most important cereal crops in human history. Today, it serves as a primary source of energy and protein for billions of people worldwide. Flour, bread, pasta, and other wheat-based products constitute an essential part of the daily diet.

With the rapid growth of the global population and increasing food demand, improving not only wheat yield but also its nutritional quality has become critically important. Recent data indicate that a large proportion of the world’s population suffers from micronutrient deficiencies, commonly referred to as “hidden hunger.” Deficiencies of iron, zinc, and vitamin A particularly affect the health of children and pregnant women.

Wheat grain has a complex chemical structure, primarily composed of starch. It also contains important protein fractions (gliadin and glutenin), lipids, dietary fiber, vitamins, and minerals. The anatomical structure of the grain — endosperm, bran, and germ — results in the uneven distribution of nutrients. For example, zinc and iron are mainly concentrated in the aleurone layer and germ, whereas starch is predominantly located in the endosperm.

The nutritional value of wheat proteins depends on the content of essential amino acids. Low levels of lysine, tryptophan, and threonine limit the biological value of grain protein. In addition, antinutritional factors such as phytic acid reduce mineral bioavailability.

Modern scientific approaches, including breeding, genetic modification, and biofortification, provide opportunities to enhance wheat’s nutritional quality. Developing micronutrient-rich varieties, modifying starch composition, and increasing essential amino acid content are important for global public health.

Therefore, the aim of this study is to conduct a comprehensive analysis of the chemical composition and nutritional properties of wheat grain and to scientifically substantiate prospects for improving its nutritional quality.

MATERIALS AND METHODS

This study is a scientific review aimed at the comprehensive evaluation of the chemical composition and nutritional properties of wheat grain, focusing on common wheat (Triticum aestivum) as the primary research object. The anatomical structure of the grain—endosperm (80–85%), bran (13–17%), and germ (2–3%)—was analyzed to assess nutrient distribution across fractions.

Scientific data on major macronutrients, including starch (60–75%), proteins (10–18%), lipids (2–3%), dietary fiber, vitamins, and minerals, were systematized and evaluated in terms of biological significance. Protein classification followed the Osborne system, dividing wheat proteins into albumins, globulins, gliadins, and glutenins. Essential amino acid limitations, particularly lysine, tryptophan, and threonine deficiencies relative to WHO recommendations, were assessed.

Starch structure, including amylose (20–30%) and amylopectin (70–80%) proportions, granule size distribution, and the role of biosynthetic enzymes such as GBSS, was analyzed. Physiological properties of resistant starch were also evaluated. Lipid composition, fatty acid profiles, phospholipids, sterols, dietary fibers (arabinoxylan and β-glucan), phytic acid effects, vitamin complexes (tocopherols, tocotrienols, carotenoids), and mineral concentrations (Zn, Fe, Se) were reviewed.

Additionally, genetic and agronomic biofortification strategies—including breeding, gene modification, mineral fertilization, and soil optimization—were analyzed to assess their effectiveness in improving wheat nutritional quality.

RESULTS

The findings demonstrate that Triticum aestivum grain possesses a complex anatomical and chemical structure, with nutrient distribution varying significantly among its morphological fractions. The grain consists of 80–85% starchy endosperm, 13–17% bran, and 2–3% germ. The endosperm serves primarily as an energy source rich in starch and gluten proteins, while the bran contains most minerals, dietary fiber, and bioactive compounds. The germ is characterized by high concentrations of protein, lipids, and vitamin E.

Starch accounts for 60–75% of dry matter and consists of amylose (20–30%) and amylopectin (70–80%). Alterations in SSIIa gene activity and RNAi-mediated suppression of starch-branching enzymes increased amylose content and resistant starch formation, enhancing butyrate production during intestinal fermentation.

Total protein content ranges from 10–18%, with gliadin and glutenin representing about 75% of total protein. Essential amino acids, particularly lysine, tryptophan, and threonine, were below recommended levels, limiting biological value.

The germ contains 8–13% lipids, predominantly linoleic acid. Bran fiber content reaches up to 53%, mainly arabinoxylan and β-glucan. Phytic acid reduces mineral bioavailability but is largely degraded during fermentation.

Average mineral concentrations were 20–35 mg/kg for Zn, 28.8–56.5 mg/kg for Fe, and 0.02–0.60 mg/kg for Se. Overall, results confirm that wheat nutritional quality depends on grain fraction, genotype, and biochemical composition, and can be improved through biofortification strategies.

DISCUSSION

The results confirm that the chemical composition of Triticum aestivum grain determines its nutritional and functional value. The uneven distribution of nutrients among the endosperm, bran, and germ explains the nutritional differences between whole-grain and refined flour products. While the endosperm is rich in starch and gluten proteins, most minerals and bioactive compounds are concentrated in the bran and germ.

The high starch content (60–75%) characterizes wheat as a major energy source. The amylose-to-amylopectin ratio is physiologically significant, as increased amylose enhances resistant starch formation, promotes butyrate production during intestinal fermentation, and may reduce inflammation and colon cancer risk. Thus, high-amylose wheat varieties are promising from both technological and preventive health perspectives.

Although wheat is an important plant protein source, low lysine content limits its biological value. Improving amino acid balance through breeding and genetic modification remains essential. At the same time, the high gliadin and glutenin content ensures bread-making quality but may contribute to celiac disease and gluten sensitivity, highlighting the need to balance technological performance and health considerations.

Despite their relatively low concentration, wheat lipids—particularly linoleic acid—and germ-derived tocopherols and tocotrienols contribute to antioxidant protection and cardiovascular health. Dietary fibers such as arabinoxylan and β-glucan support metabolic health, although phytic acid may reduce mineral bioavailability. Fermentation can partially mitigate this effect.

Iron and zinc concentrations are closely linked to global micronutrient deficiencies. Since these elements are concentrated in bran and germ, refining reduces their levels. Therefore, genetic and agronomic biofortification strategies are effective approaches to combating “hidden hunger.” Overall, modern breeding, molecular, and agronomic tools offer significant potential to enhance wheat nutritional quality, though genotype–environment interactions and antinutritional factors require further investigation.

CONCLUSION

The findings confirm that Triticum aestivum grain possesses a complex chemical composition and high nutritional and functional value. Its high starch content (60–75%) characterizes wheat as a major energy source, while variations in the amylose–amylopectin ratio influence both technological properties and human health, particularly through increased resistant starch and improved gut microbiota activity.

With a protein content of 10–18%, wheat represents an important plant protein source; however, limited levels of essential amino acids such as lysine, tryptophan, and threonine reduce its biological value. Although gliadin and glutenin ensure desirable baking quality, they may also raise health concerns in sensitive individuals.

Despite their relatively low proportion, lipids—especially in the germ—along with tocopherols, contribute to antioxidant protection. Dietary fibers such as arabinoxylan and β-glucan support metabolic health, whereas phytic acid may limit mineral bioavailability.

Wheat is also an important source of micronutrients, particularly zinc, iron, and selenium. Their concentration in bran and germ supports the nutritional advantages of whole-grain products. Genetic diversity and biofortification strategies provide effective means to enhance Fe and Zn content.

Overall, improving wheat nutritional quality through modern breeding, molecular biology, and agronomic biofortification remains a key direction for strengthening global food security and public health.

Reference:

1. Asqarov I. R. Tabobat qomusi. – Toshkent: Mumtoz so‘z, 2019. – 592 p. [in Uzbek]
2. Šramková Z., Gregová E., Šturdík E. Chemical composition and nutritional quality of wheat grain // Acta Chimica Slovaca. – 2009. – Vol. 2, No. 1. – P. 115–138.
3. Shewry P. R., Hey S. J. The contribution of wheat to human diet and health // Food and Energy Security. – 2015. – Vol. 4, No. 3. – P. 178–202. – DOI: 10.1002/fes3.64.
4. Shewry P. R., Halford N. G. Cereal seed storage proteins: Structures, properties and role in grain utilization // Journal of Experimental Botany. – 2002. – Vol. 53, No. 370. – P. 947–958. – DOI: 10.1093/jexbot/53.370.947.
5. Asqarov I. R., Xasanova D. T. Undirilgan bug‘doy asosida olingan oziq-ovqat qo‘shilmasining antioksidantlik xususiyatlarini o‘rganish // Journal of Chemistry of Goods and Traditional Medicine. – 2023. – Vol. 2, No. 3. – P. 174–177. [in Uzbek]
6. Xasanova D. T. Vzaimootnosheniya sem’i i gosudarstva i funktsii sem’i // Izvestiya VUZov (Kyrgyzstan). – 2014. – No. 2. – P. 45–46. [in Russian]