Understanding the Relationships between Free Asparagine in Grain and Other Traits to Breed Low-Asparagine Wheat

Unlocking the potential health improving properties of sprouted wheat

Sprouting can enhance the bioavailability and stimulate the production of health-promoting compounds. This research explored the potential health benefits of wheat sprouting, focusing on underexplored areas in existing literature such as alterations in phenylalanine ammonia-lyase (PAL) activity and glutathione levels during wheat sprouting. Furthermore, special attention was directed toward asparagine (Asn), the main precursor of acrylamide formation, as regulatory agencies are actively seeking to impose limitations on the presence of acrylamide in baked products. The results demonstrate elevated levels of PAL (4.5-fold at 48 h of sprouting), antioxidants, and total phenolics (1.32 mg gallic acid equivalent/g dry matter at 72 h of sprouting), coupled with a reduction in Asn (i.e. 11-fold at 48 h of sprouting) and glutathione concentrations, after wheat sprouting. These findings suggest that sprouting can unlock health-promoting properties in wheat. Optimizing the sprouting process to harness these benefits, however, may have implications for the techno-functionality of wheat flour in food processing.

Reducing Acrylamide Formation Potential by Targeting Free Asparagine Accumulation in Seeds

Acrylamide is a probable carcinogen in humans and is formed when reducing sugars react with free asparagine (Asn) during thermal processing of food. Although breeding for low reducing sugars worked well in potatoes, it is less successful in cereals. However, reducing free Asn in cereals has great potential for reducing acrylamide formation, despite the role that Asn plays in nitrogen transport and amino acid biosynthesis. In this perspective, we summarize the efforts aimed at reducing free Asn in cereal grains and discuss the potentials and challenges associated with targeting this essential amino acid, especially in a seed-specific manner.

Different wheat loci are associated to heritable free asparagine content in grain grown under different water and nitrogen availability

KEY MESSAGE

Different wheat QTLs were associated to the free asparagine content of grain grown in four different conditions. Environmental effects are a key factor when selecting for low acrylamide-forming potential. The amount of free asparagine in grain of a wheat genotype determines its potential to form harmful acrylamide in derivative food products. Here, we explored the variation in the free asparagine, aspartate, glutamine and glutamate contents of 485 accessions reflecting wheat worldwide diversity to define the genetic architecture governing the accumulation of these amino acids in grain. Accessions were grown under high and low nitrogen availability and in water-deficient and well-watered conditions, and plant and grain phenotypes were measured. Free amino acid contents of grain varied from 0.01 to 1.02 mg g-1 among genotypes in a highly heritable way that did not correlate strongly with grain yield, protein content, specific weight, thousand-kernel weight or heading date. Mean free asparagine content was 4% higher under high nitrogen and 3% higher in water-deficient conditions. After genotyping the accessions, single-locus and multi-locus genome-wide association study models were used to identify several QTLs for free asparagine content located on nine chromosomes. Each QTL was associated with a single amino acid and growing environment, and none of the QTLs colocalised with genes known to be involved in the corresponding amino acid metabolism. This suggests that free asparagine content is controlled by several loci with minor effects interacting with the environment. We conclude that breeding for reduced asparagine content is feasible, but should be firmly based on multi-environment field trials.

KEY MESSAGE

Different wheat QTLs were associated to the free asparagine content of grain grown in four different conditions. Environmental effects are a key factor when selecting for low acrylamide-forming potential.

Impact of amino acids and sugars after thermal processing on acrylamide formation in synthetic potato models and real potatoes

Amino acids and sugars, along with the thermal processing, are considered the main parameters to control acrylamide formation in fried potatoes. To evaluate which of these parameters had the greatest influence, 10 synthetic potato-starch-based models formulated in different amino acid and/or sugar combinations and three potato cultivars were assigned. High-performance-liquid chromatography and gas chromatography flame-ionized-detectors were applied to quantify amino acids, sugars, and acrylamide. Results showed that reducing sugars and sucrose significantly increased acrylamide formation amongst all potato samples. Synthetic potato models Asn-GFS contained the highest amount of acrylamide compared to Glu-Fru and real potatoes (Agria and Kennebec). Thus, sugars were considered critical factors for acrylamide formation in potatoes and remained the most practical way of reducing its production.

Genetic control of grain amino acid composition in a UK soft wheat mapping population

Wheat (Triticum aestivum L.) is a major source of nutrients for populations across the globe, but the amino acid composition of wheat grain does not provide optimal nutrition. The nutritional value of wheat grain is limited by low concentrations of lysine (the most limiting essential amino acid) and high concentrations of free asparagine (precursor to the processing contaminant acrylamide). There are currently few available solutions for asparagine reduction and lysine biofortification through breeding. In this study, we investigated the genetic architecture controlling grain free amino acid composition and its relationship to other traits in a Robigus × Claire doubled haploid population. Multivariate analysis of amino acids and other traits showed that the two groups are largely independent of one another, with the largest effect on amino acids being from the environment. Linkage analysis of the population allowed identification of quantitative trait loci (QTL) controlling free amino acids and other traits, and this was compared against genomic prediction methods. Following identification of a QTL controlling free lysine content, wheat pangenome resources facilitated analysis of candidate genes in this region of the genome. These findings can be used to select appropriate strategies for lysine biofortification and free asparagine reduction in wheat breeding programs.

Formulation and Processing Strategies to Reduce Acrylamide in Thermally Processed Cereal-Based Foods

Acrylamide, a thermal process contaminant, is generated in carbohydrate-rich foods processed at high temperatures (above 120 °C). Since acrylamide indicates a human health concern, the acrylamide contents of various foods and the dietary exposure of the population to acrylamide are very well investigated. Commonly consumed foods in the daily diet of individuals such as bakery products, potato products and coffee are major dietary sources of acrylamide. In recent years, dietary exposure levels of the population and mitigation measures for reducing acrylamide in different food products have gained importance to decrease the public's exposure to acrylamide. Since the complete elimination of acrylamide in foods is not possible, various mitigation measures to reduce acrylamide to levels as low as reasonably achievable have been developed and applied in the food industry. Mitigation strategies should be applied according to the different product categories during agricultural production, formulation, processing and final consumer preparation stages. The aim of this review is to evaluate formulation and processing strategies to reduce acrylamide in various cereal-based food products and to discuss the applicability of mitigation measures in the food industry by taking into consideration the organoleptic properties, nutritional value, cost and regulations in the light of current knowledge.

Exploring Variability of Free Asparagine Content in the Grain of Bread Wheat (Triticum aestivum L.) Varieties Cultivated in Italy to Reduce Acrylamide-Forming Potential

Acrylamide, a suspected human carcinogen, is generated during food processing at high temperatures in the Maillard reaction, which involves reducing sugars and free asparagine. In wheat derivatives, free asparagine represents a key factor in acrylamide formation. Free asparagine levels in the grain of different wheat genotypes has been investigated in recent studies, but little is known about elite varieties that are cultivated in Italy. Here, we analysed the accumulation of free asparagine in a total of 54 bread wheat cultivars that are relevant for the Italian market. Six field trials in three Italian locations over two years were considered. Wholemeal flours obtained from harvested seeds were analysed using an enzymatic method. Free asparagine content ranged from 0.99 to 2.82 mmol/kg dry matter in the first year, and from 0.55 to 2.84 mmol/kg dry matter in the second year. Considering the 18 genotypes that were present in all the field trials, we evaluated possible environment and genetic influences for this trait. Some cultivars seemed to be highly affected by environment, whereas others showed a relative stability in free asparagine content across years and locations. Finally, we identified two varieties showing the highest free asparagine levels in our analysis, representing potential useful materials for genotype x environment interaction studies. Two other varieties, which were characterized by low amounts of free asparagine in the considered samples, may be useful for the food industry and for future breeding programs aimed to reduce acrylamide-forming potential in bread wheat.

Identifying the origin of acrylamide in Peruvian panela production to inform strategies for its reduction

Maximum levels of acrylamide have been set by the European Commission (EU) 2017/2158 for several food products due to its carcinogenic properties. Although not regulated yet, European buyers are requesting maximum levels of 0.8 mg kg^-1 in artisanal panela (raw cane sugar) from northern Peru. Panela in this area is produced by 600 small holder farmers and exportation guarantees a respectable price in an area with a high index of poverty. The objective here was to determine the cause of high acrylamide concentrations in panela to inform cost effective minimisation strategies. We monitored panela production from field to final product to understand the scale of the problem, identify the cause of acrylamide formation, as well as the effect of storage on its concentration. We also determined the utility of rapid kits for asparagine quantification. Our results indicate that high acrylamide levels are a widespread problem (85% of samples analysed) and there was a correlation between acrylamide and asparagine of R² = 0.58 (p < 0.001), but not with any post-harvest processing variable. We estimate that with a concentration of asparagine of <0.1 g l^-1 in sugarcane juice, the threshold set by buyers for acrylamide can be met. Potential solutions to reduce asparagine include varietal selection, improved agronomic practices and the use of asparaginase during panela production. However, any proposed measure should be applicable in the context of the rural Peru. Additionally, we confirm the utility of rapid and low-cost kits for measuring asparagine. This pioneering study provides a baseline for effective management for acrylamide minimization in panela.

Comparative Compositions of Grain of Bread Wheat, Emmer and Spelt Grown with Different Levels of Nitrogen Fertilisation

Five cultivars of bread wheat and spelt and three of emmer were grown in replicate randomised field trials on two sites for two years with 100 and 200 kg nitrogen fertiliser per hectare, reflecting low input and intensive farming systems. Wholemeal flours were analysed for components that are suggested to contribute to a healthy diet. The ranges of all components overlapped between the three cereal types, reflecting the effects of both genotype and environment. Nevertheless, statistically significant differences in the contents of some components were observed. Notably, emmer and spelt had higher contents of protein, iron, zinc, magnesium, choline and glycine betaine, but also of asparagine (the precursor of acrylamide) and raffinose. By contrast, bread wheat had higher contents of the two major types of fibre, arabinoxylan (AX) and β-glucan, than emmer and a higher AX content than spelt. Although such differences in composition may be suggested to result in effects on metabolic parameters and health when studied in isolation, the final effects will depend on the quantity consumed and the composition of the overall diet.

The Use of DArTseq Technology to Identify New SNP and SilicoDArT Markers Related to the Yield-Related Traits Components in Maize

In the last decade, many scientists have used molecular biology methods in their research to locate the grain-yield-determining loci and yield structure characteristics in maize. Large-scale molecular analyses in maize do not only focus on the identification of new markers and quantitative trait locus (QTL) regions. DNA analysis in the selection of parental components for heterotic crosses is a very important tool for breeders. The aim of this research was to identify and select new markers for maize (SNP and SilicoDArT) linked to genes influencing the size of the yield components in maize. The plant material used for the research was 186 inbred maize lines. The field experiment was established in twolocations. The yield and six yield components were analyzed. For identification of SNP and SilicoDArT markers related to the yield and yield components, next-generation sequencing was used. As a result of the biometric measurements analysis, differentiation in the average elevation of the analyzed traits for the lines in both locations was found. The above-mentioned results indicate the existence of genotype–environment interactions. The analysis of variance for the observed quality between genotypes indicated a statistically significant differentiation between genotypes and a statistically significant differentiation for all the observed properties betweenlocations. A canonical variable analysis was applied to present a multi-trait assessment of the similarity of the tested maize genotypes in a lower number of dimensions with the lowest possible loss of information. No grouping of lines due to the analyzed was observed. As a result of next-generation sequencing, the molecular markers SilicoDArT (53,031) and SNP (28,571) were obtained. The genetic distance between the analyzed lines was estimated on the basis of these markers. Out of 81,602 identified SilicoDArT and SNP markers, 15,409 (1559 SilicoDArT and 13,850 SNPs) significantly related to the analyzed yield components were selected as a result of association mapping. The greatest numbers of molecular markers were associated with cob length (1203), cob diameter (1759), core length (1201) and core diameter (2326). From 15,409 markers significantly related to the analyzed traits of the yield components, 18 DArT markers were selected, which were significant for the same four traits (cob length, cob diameter, core length, core diameter) in both Kobierzyce and Smolice. These markers were used for physical mapping. As a result of the analyses, it was found that 6 out of 18 (1818; 14,506; 2317; 3233; 11,657; 12,812) identified markers are located inside genes. These markers are located on chromosomes 8, 9, 7, 3, 5, and 1, respectively.