Wheat grain proteins: past, present, and future

Research on wheat grain proteins is reviewed, including achievements over the past century and priorities for future research. The focus is on three groups of proteins that have major impacts on wheat quality and utilization: the gluten proteins which determine dough viscoelasticity but also trigger celiac disease in susceptible individuals, the puroindolines which are major determinants of grain texture and the amylase/ trypsin inhibitors which are food and respiratory allergens and are implicated in triggering celiac disease and nonceliac wheat sensitivity

Can we increase the use of wheat and other cereals as sources of protein?

Wheat and other cereals are important sources of dietary protein and have the potential for exploitation to replace products based on animal proteins. However, grain protein contents are low, about 10–15%, compared to more protein-rich legumes and oilseeds. Grain protein content is determined by genetic and environmental factors, particularly nitrogen fertilisation, and is also inversely correlated with grain yield. Strategies to increase grain protein content are reviewed including exploiting genetic variation in the relationship between yield and protein content (grain protein deviation). The functional properties of cereal grains for processing are determined by the properties of the prolamin storage proteins, which include the gluten proteins of wheat. Understanding the structures and functional properties of these proteins will therefore facilitate their modification to generate a wider range of properties to extend the use of cereal proteins to replace animal proteins in food systems

The Contribution of Wheat to Human Nutrition and Health

Wheat provides 20% of calories globally but up to 50% in some regions. In addition to energy, it provides protein, dietary fibre, mineral micronutrients (iron, zinc and selenium), B vitamins and beneficial phytochemicals. However, grain composition varies between genotypes with strong effects of environment. In addition, beneficial components are concentrated in the embryo and outer layers which form the bran on milling. Hence their concentrations are depleted in white flour

Wheat

Wheat is the dominant crop in temperate countries being used for human food and livestock feed. Its success depends partly on its adaptability and high yield potential but also on the gluten protein fraction which confers the viscoelastic properties that allow dough to be processed into bread, pasta, noodles, and other food products. Wheat also contributes essential amino acids, minerals, and vitamins, and beneficial phytochemicals and dietary fibre components to the human diet, and these are particularly enriched in whole-grain products. However, wheat products are also known or suggested to be responsible for a number of adverse reactions in humans, including intolerances (notably coeliac disease) and allergies (respiratory and food). Current and future concerns include sustaining wheat production and quality with reduced inputs of agrochemicals and developing lines with enhanced quality for specific end-uses, notably for biofuels and human nutrition

Wheat glutenin polymers 1. structure, assembly and properties

The importance of wheat glutenin polymers in determining the processing quality of wheat is generally accepted. Similarly, genetic and molecular studies have provided detailed information on the sequences of the glutenin subunits and identified associations between individual subunits and either good or poor quality for breadmaking. However, our knowledge of the polymers themselves, including their molecular masses, structures and pathways of synthesis and assembly, remains incomplete and is largely based on studies carried out between 20 and 50 years ago. The current paper therefore reviews this knowledge and identifies priorities for future research which is required to facilitate the use of modern molecular tools to develop improved types of wheat for future requirement

Modern Wheat

The yields of wheat in the UK and across much of the world have increased massively over the past century, from a few tonnes per hectare at the start of the twentieth century to current UK average yields of between eight and nine tonnes per hectare. Many factors have contributed to these increases, with genetic improvement by plant breeding being particularly important in the second half of the 20th centur

Do gluten peptides stimulate weight gain in humans?

Observations from animal and in vitro laboratory research, and anecdotal evidence, have led to the suggestion that gluten consumption stimulates weight gain by the presence of peptides expressing opioid activity. Another proposed mechanism is that gluten peptides decrease resting energy expenditure resulting in a positive energy balance. In order to induce such effects in vivo, intact food peptides must be absorbed in sufficient quantities, remain intact in the blood for sufficient time to have long-lasting biological activity and bind to receptors involved in appetite, satiety and energy regulation. However, although peptides from food may pass from the intestine into the blood in extremely low quantities, they are generally rapidly degraded by plasma and vasculum-bound aminopeptidases, resulting in very short half-lives and loss of bioactivity. At present, gluten peptide sequences that influence regulators of energy metabolism have not been identified. Furthermore, data on the quantitative absorption of gluten peptides in the blood stream, their stability and lasting bioactivity are also lacking. Therefore, there is no evidence for proposed effects on driving appetite by the brain, nor on energy expenditure and weight gain. Furthermore, the level of overweight observed in various countries appears to be independent of the level of wheat consumption, and abundant observational evidence in humans shows that the levels of gluten consumption are neither related to daily calorie intake nor to BMI. This narrative review therefore discusses the proposed effects of gluten on bodyweight (BW) and putative biological mechanisms in the light of the current evidence