Headspace volatiles profiles of different spring varieties and a wild relative of wheat flour.

Volatile profiling was conducted on four wheat varieties Triticum aestivum cv. Chinese Spring (CS), Highbury (High), Paragon (Para), Pavon76 (Pav76), and one wild relative Triticum timopheevii (P95). Headspace solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to explore differences in flavor formation mechanisms in different flours before and after starch gelatinization. Solvent retention capacity (SRC) analysis revealed subtle differences in water absorption, gluten strength, and starch characteristics across wheat flour types. Rapid Visco Analysis (RVA) of whole wheat flour demonstrated significant variations in pasting properties among wheat varieties, with P95 exhibiting higher viscosities compared to CS and High potentially influenced by starch gelatinization, protein-starch interactions, and lipid content. Aroma contributions of P95 clustered positively in PCA plots, contrasting with the four main varieties, indicative of species-level differentiation. Furthermore, the study highlighted the roles of viscosity, protein structure, lipid content, and fatty acid composition in modulating the release and perception of volatile aroma compounds during heating. This study sheds light on how the distinct characteristics of wheat flour influence aroma profiles, revealing species-level differences and the pivotal role of physiochemical properties in shaping flavor development mechanisms.

Aroma binding and stability in brewed coffee: A case study of 2-furfurylthiol.

The aroma stability of fresh coffee brew was investigated during storage over 60 min, there was a substantial reduction in available 2-furfurylthiol (2-FFT) (84%), methanethiol (72%), 3-methyl-1H-pyrole (68%) and an increase of 2-pentylfuran (65%). It is proposed that 2-FFT was reduced through reversible chemical binding and irreversible losses. Bound 2-FFT was released after cysteine addition, thereby demonstrating that a reversible binding reaction was the dominant mechanism of 2-FFT loss in natural coffee brew. The reduction in available 2-FFT was investigated at different pH and temperatures. At high pH, the reversible binding of 2-FFT was shown to protect 2-FFT from irreversible losses, while irreversible losses led to the reduction of total 2-FFT at low pH. A model reaction system was developed and a potential conjugate, hydroxyhydroquinone, was reacted with 2-FFT. Hydroxyhydroquinone also showed 2-FFT was released after cysteine addition at high pH.

Enhancing Robusta coffee aroma by modifying flavour precursors in the green coffee bean.

This study attempted to improve Robusta sensory properties by modifying the beans chemical composition. Building on our previous work, which modified bean pH through acid pre-treatment, a model system was developed where, sugar solutions (glucose, fructose, sucrose) were used to pre-treat Robusta coffee beans with the aim to modify the concentration/availability/location of these aroma precursors. Beans were then dried to equal water activity, subjected to equal roast intensity and ground to comparable particle size distributions. The treatment significantly impacted aroma generation during roasting leading to an altered level of pyrazines, furans, ketones, organic acid and heterocyclic nitrogen-containing compounds (p < 0.05). The optimum treatment was 15 g/100 g fructose. 80% treated Robusta could be blended with Arabica in coffee brew without significant aroma differences being perceived when compared to 100% Arabica brew. Furthermore the aroma of the fructose treated Robusta was more stable than Arabica over six weeks accelerated shelflife storage.

Modifying Robusta coffee aroma by green bean chemical pre-treatment.

Green Robusta beans were subjected to pre-treatment with the aim of reducing the perceived aroma difference between Arabica and Robusta coffee. Treatment was a short soaking procedure with varying concentrations of acetic acid (up to 5%). Samples were subjected to thermal treatment (roasted) and ground to a standardised particle size distribution. Aroma compounds were evaluated by headspace analysis using solid-phase microextraction and gas chromatography-mass spectrometry. Pre-treatment significantly affected aroma formation during roasting and resulted in a modified level of pyrazines, furanic compounds and sulfur-containing compounds (p < 0.05). Principal component analysis illustrated that the aroma profile of the pre-treated Robusta coffee was closer to the target Arabica coffee after roasting. Sensory results confirmed that the aroma of the 2% acetic acid pre-treated Robusta brew was similar to Arabica; the maximum inclusion level of Robusta coffee in a blend could be increased from 20% to 80%.

Analytical ultracentrifugation in saliva research: Impact of green tea astringency and its significance on the in-vivo aroma release.

Current saliva testing methods rely on cutting edge yet expensive techniques for the detection and analysis of genetic material, proteins and biomarkers for clinical use. However, these techniques are limited in scope and often cannot be used with complex food materials. We propose an efficient ex-vivo tool for evaluating biologically relevant interactions between food components and human saliva using sedimentation velocity analytical ultracentrifugation (SV-AUC). We evaluated macromolecular content from "unstimulated" (US) and "stimulated" (SS) samples pooled from 5 healthy volunteers. Over 90% of total saliva protein consisted of α-amylase and mucin, and up to 10% was secretory immunoglobulin A (SIgA). It was shown that α-amylase concentration increased upon parafilm stimulation, which lead to a decrease in the viscosity of saliva. Then, we used a simple food system (green tea) to evaluate changes in the salivary protein content caused by green tea polyphenols. It was found that aroma release from green tea is highly influenced by interactions between α-amylase and polyphenol epigallocatechin 3-gallate (EGCG). This interaction was found to increase the viscosity of the salivary bulk, suggested to contribute to astringency, and increased the concentrations of ß-ionone, benzaldehyde and isovaleraldehyde (P < 0.01), suggested to play a significant role in the characteristic flavour of green tea.

Determination of volatile marker compounds of common coffee roast defects.

Coffee beans from the same origin were roasted using six time-temperature profiles, in order to identify volatile aroma compounds associated with five common roast coffee defects (light, scorched, dark, baked and underdeveloped). Thirty-seven volatile aroma compounds were selected on the basis that they had previously been identified as potent odorants of coffee and were also identified in all coffee brew preparations; the relative abundance of these aroma compounds was then evaluated using gas chromatography mass spectrometry (GC-MS) with headspace solid phase micro extraction. Some of the 37 key aroma compounds were significantly changed in each coffee roast defect and changes in one marker compound was chosen for each defect type, that is, indole for light defect, 4-ethyl-2-methoxyphenol for scorched defect, phenol for dark defect, maltol for baked defect and 2,5-dimethylfuran for underdeveloped defect. The association of specific changes in aroma profiles for different roast defects has not been shown previously and could be incorporated into screening tools to enable the coffee industry quickly identify if roast defects occur during production.