Prebiotic potential and gastrointestinal effects of immature wheat grain (IWG) biscuits

Natural Variation in the Content and Degree of Polymerization of Fructans in Wheat: Potential for Selection of Genotypes with Beneficial Health Composition

Fructans are important biocompounds because of their health-promoting effects as dietary fiber and prebiotics and also because of their harmful effects as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) particularly in people suffering from irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), and recently as potential triggers of non-celiac wheat/gluten sensitivity. In this work, we have analyzed the fructan contents as well as its degree of polymerization (DP) in a genetically diverse set of wheat varieties, modern and landraces, from different commonly consumed species (N = 124). A significant variation in fructan contents within and between species was observed, with the following relationship: Triticum aestivum (Landraces) > Triticum aestivum (Modern) ≥ Triticum turgidum (Modern) = T. turgidum (Landraces) ≥ Triticum spelta. In addition, a substantial part of the fructans (>50%) showed a DP ≤ 6. Considering that wheat is a major source of fructans, our results can contribute to a better nutritional management of our diets and be a basis for targeted wheat breeding to alter fructan contents.

Young cereal grains as a new source of healthy and hypoallergenic foods: a review

Young cereals contain higher quantities of nutrients such as sterols, γ-oryzanols, tocols and phenolic compounds than mature grains. They are more easily digested with low allergenic potential. Applications of young cereals include plant-based milk substitutes, substitution of wheat flour, malting, fructose and pigments production. Research on young cereals is scarce and mainly focused on botanical studies. This review focused on major young cereals (wheat, rice and corn) compositions, bioactive compounds and applications that will benefit future research in plant-based food and functional ingredients. During grain maturity, amylose content increased, whereas amylopectin content and its structure varied depending largely on grain type. In rice, non-significant differences in average chain length of amylopectin during grain maturity were reported, with protein contents of young rice and wheat higher than at their mature stages. High digestibility of the flowery-to-milky stage rice protein indicated lower allergen levels. Immune-reactive gluten was not found in young wheat. Young wheat contained high essential amino acids with a more balanced profile, particularly for lysine. The angiotensin-converting enzyme inhibitory effect of milky stage protein hydrolysate was higher than mature protein. Young grains contained less starch with more fiber and sugar. Antioxidant activity in young rice was high as it contained gamma-oryzanol, ascorbate, glutathione tocopherols and phenolic compounds. This review of the available information concerning the composition, properties and functional ingredients of immature cereals will assist future research in plant-based food and functional ingredients.

Prebiotic Potential of Cereal Components

One type of functional food that has been receiving much attention is food rich in prebiotics. The old but still valid definition of prebiotics defines them as non-digestible food components that selectively stimulate the growth and/or activity of the beneficial bacteria in the colon and, as a result, improve the host health. Cereals, as one of the main components in the human diet, contain substantial levels of dietary fiber with probable prebiotic potential. In addition, dietary fiber, particularly soluble dietary fiber, has recently emerged as a promising natural highly functional food ingredient in food production. This review focuses on the prebiotic potential of cereal dietary fiber types and covers the achievements and developments regarding its isolation. First, the probiotic and prebiotic concepts will be discussed. Next, different components of dietary fiber and their effect on the host bacteria through in vitro and/or in vivo studies will be reviewed. In a last part, this paper also discusses means of boosting the prebiotic properties of cereal components and innovative strategies for the extraction of cereal dietary fiber. The review focuses on wheat as a leading cereal crop that is widely and intensely used throughout the world in food production.

Synthesis and accumulation of amylase-trypsin inhibitors and changes in carbohydrate profile during grain development of bread wheat (Triticum aestivum L.)

BACKGROUND

Recent studies indicate that amylase-trypsin inhibitors (ATIs) and certain carbohydrates referred to as FODMAPs (fermentable oligo-, di-, monosaccharides and polyols) play an important role in promoting wheat sensitivity. Hitherto, no study has investigated the accumulation of ATIs during the development of the wheat caryopsis. We collected caryopses of common wheat cv. 'Arnold' at eight different grain developmental stages to study compositional changes in ATI and FODMAP content.

RESULTS

The harvested caryopses were analysed for their size, protein and carbohydrate concentrations. ATIs were further characterized by MALDI-TOF MS, and their trypsin inhibition was evaluated by an enzymatic assay. The results showed that ATI accumulation started about 1 week after anthesis and subsequently increased steadily until physiological maturity. However, the biological activity of ATIs in terms of enzyme inhibition was not detectable before about 4 weeks after anthesis. Carbohydrate analysis revealed the abundance of short-chain fructans in early stages of grain development, whereas non-water-soluble carbohydrates increased during later developmental stages.

CONCLUSIONS

The results provide new insights into the complex metabolisms during grain filling and maturation, with particular emphasis on the ATI content as well as the inhibitory potential towards trypsin. The time lag between ATI accumulation and development of their biological activity is possibly attributed to the assembling of ATIs to dimers and tetramers, which seems to be crucial for their inhibitory potential.

Multifunctional fructans and raffinose family oligosaccharides

Fructans and raffinose family oligosaccharides (RFOs) are the two most important classes of water-soluble carbohydrates in plants. Recent progress is summarized on their metabolism (and regulation) and on their functions in plants and in food (prebiotics, antioxidants). Interest has shifted from the classic inulin-type fructans to more complex fructans. Similarly, alternative RFOs were discovered next to the classic RFOs. Considerable progress has been made in the understanding of structure-function relationships among different kinds of plant fructan metabolizing enzymes. This helps to understand their evolution from (invertase) ancestors, and the evolution and role of so-called "defective invertases." Both fructans and RFOs can act as reserve carbohydrates, membrane stabilizers and stress tolerance mediators. Fructan metabolism can also play a role in osmoregulation (e.g., flower opening) and source-sink relationships. Here, two novel emerging roles are highlighted. First, fructans and RFOs may contribute to overall cellular reactive oxygen species (ROS) homeostasis by specific ROS scavenging processes in the vicinity of organellar membranes (e.g., vacuole, chloroplasts). Second, it is hypothesized that small fructans and RFOs act as phloem-mobile signaling compounds under stress. It is speculated that such underlying antioxidant and oligosaccharide signaling mechanisms contribute to disease prevention in plants as well as in animals and in humans.

Multifunctional fructans and raffinose family oligosaccharides

Fructans and raffinose family oligosaccharides (RFOs) are the two most important classes of water-soluble carbohydrates in plants. Recent progress is summarized on their metabolism (and regulation) and on their functions in plants and in food (prebiotics, antioxidants). Interest has shifted from the classic inulin-type fructans to more complex fructans. Similarly, alternative RFOs were discovered next to the classic RFOs. Considerable progress has been made in the understanding of structure-function relationships among different kinds of plant fructan metabolizing enzymes. This helps to understand their evolution from (invertase) ancestors, and the evolution and role of so-called "defective invertases." Both fructans and RFOs can act as reserve carbohydrates, membrane stabilizers and stress tolerance mediators. Fructan metabolism can also play a role in osmoregulation (e.g., flower opening) and source-sink relationships. Here, two novel emerging roles are highlighted. First, fructans and RFOs may contribute to overall cellular reactive oxygen species (ROS) homeostasis by specific ROS scavenging processes in the vicinity of organellar membranes (e.g., vacuole, chloroplasts). Second, it is hypothesized that small fructans and RFOs act as phloem-mobile signaling compounds under stress. It is speculated that such underlying antioxidant and oligosaccharide signaling mechanisms contribute to disease prevention in plants as well as in animals and in humans.

Prebiotics to fight diseases: reality or fiction?

Bacteria living in the gastrointestinal tract are crucial for human health and disease occurrence. Increasing the beneficial intestinal microflora by consumption of prebiotics, which are 'functional foods', could be an elegant way to limit the number and incidence of disorders and to recover from dysbiosis or antibiotic treatments. This review focuses on the short-chain low-digestible carbohydrates (LDCs) which are metabolized by gut microbiota serving as energy source, immune system enhancers or facilitators of mineral uptake. Intake of foods containing LDCs can improve the state of health and may prevent diseases as for example certain forms of cancer. Given the large number of different molecules belonging to LDCs, we focused our attention on fructans (inulin, fructo-oligosaccharides), galacto-oligosaccharides and resistant starches and their therapeutic and protective applications. Evidence is accumulating that LDCs can inhibit bacterial and viral infections by modulating host defense responses and by changing the interactions between pathogenic and beneficial bacteria. Animal studies and studies on small groups of human subjects suggest that LDCs might help to counteract colorectal cancer, diabetes and metabolic syndrome. The action mechanisms of LDCs in the human body might be broader than originally thought, perhaps also including reactive oxygen species scavenging and signaling events.