Bitterness in whole wheat bread can negatively influence product acceptability and consumption. The overall goal of this project was to identify the main bitter compounds in a commercial whole wheat bread product. Sensory-guided fractionation of the crust (most bitter portion of the bread sample) utilising liquid-liquid extraction, solid-phase extraction, ultra-filtration and 2-D offline RPLC revealed multiple bitter compounds existed. The compounds with the highest bitterness intensities were selected and structurally elucidated based on accurate mass-TOF, MS/MS, 1D and 2D NMR spectroscopy. Eight bitter compounds were identified: Acortatarins A, Acortatarins C, 5-(hydroxymethyl)furfural(HMF), 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP), N-(1-deoxy-d-fructos-1-yl)-l-tryptophan (ARP), Tryptophol (TRO), 2-(2-formyl-5-(hydroxymethyl-1H-pyrrole-1-yl)butanoic acid (PBA) and Tryptophan (TRP). Based on the structures of these compounds, two main mechanisms of bitterness generation in wheat bread were supported, fermentation and Maillard pathways.

Bitterness of whey protein hydrolysates (WPH) can negatively affect product quality and limit utilization in food and pharmaceutical applications. Four main bitter peptides were identified in a commercial WPH by means of sensory-guided fractionation techniques that included ultrafiltration and offline two-dimensional reverse phase chromatography. LC-TOF-MS/MS analysis revealed the amino acid sequences of the bitter peptides were YGLF, IPAVF, LLF, and YPFPGPIPN that originated from α-lactalbumin, β-lactoglobulin, serum albumin, and β-casein, respectively. Quantitative LC-MS/MS analysis reported the concentrations of YGLF, IPAVF, LLF, and YPFPGPIPN to be 0.66, 0.58, 1.33, and 2.64 g/kg powder, respectively. Taste recombination analysis of an aqueous model consisting of all four peptides was reported to explain 88% of the bitterness intensity of the 10% WPH solution.

We have developed an efficient and readily available catalyst system CuBr/racemic BINOL (1,1'-binaphthyl-2,2'-diol) that catalyzes N-arylation of aliphatic amines at room temperature, and this inexpensive catalyst system is of high selectivity and tolerance toward various functional groups in the substrates.

The chemistry and fate of hydroxycinnamic acids (ferulic, p-coumeric, caffeic, sinapic, and cinnamic acid) in a glucose/glycine simulated baking model (10% moisture at 200 degrees C for 15 min) were investigated. Liquid chromatography-mass spectrometry analysis of glucose/glycine and glucose/glycine/hydroxycinnamic acid model systems confirmed the phenolics reacted with Maillard intermediates; two main reaction product adducts were reported. On the basis of isotopomeric analysis, LC-MS, and NMR spectroscopy, structures of two ferulic acid-Maillard reaction products were identified as 6-(4-hydroxy-3-methoxyphenyl)-5-(hydroxymethyl)-8-oxabicyclo[3.2.1]oct-3-en-2-one (adduct I) and 2-(6-(furan-2-yl)-7-(4-hydroxy-3-methoxyphenyl)-1-methyl-3-oxo-2,5-diazabicyclo[2.2.2]oct-5-en-2-yl)acetic acid (adduct II). In addition, a pyrazinone-type Maillard product, 2-(5-(furan-2-yl)-6-methyl-2-oxopyrazin-1(2H)-yl) acetic acid (IIa), was identified as an intermediate for reaction product adduct II, whereas 3-deoxy-2-hexosulose was identified as an intermediate of adduct I. Both adducts I and II were suggested to be generated by pericyclic reaction mechanisms. Quantitative gas chromatography (GC) analysis and liquid chromatography (LC) also indicated that the addition of ferulic acid to a glucose/glycine model significantly reduced the generation of select Maillard-type aroma compounds, such as furfurals, methylpyrazines, 2-acetylfuran, 2-acetylpyridine, 2-acetylpyrrole, and cyclotene as well as inhibited color development in these Maillard models. In addition, adducts I and II suppressed the bacterial lipopolysaccharide (LPS)-mediated expression of two prototypical pro-inflammatory genes, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, in an in vitro murine macrophage model; ferulic acid reported negligible activity.

The influence of hydroxycinnamic acids (HCAs) on food flavor is reviewed. In coffee, wholegrain foods and related model systems, the HCAs have been reported to contribute to the flavor profile by multiple mechanisms, such as to impart taste attributes, to generate aroma and taste-active compounds by phenolic degradation, as well as to alter the mechanisms of the Maillard reaction and related flavor development. Consequently the role of HCAs on the flavor properties of food products is complex, multifaceted and can be related to the chemistry and fate of HCAs during thermal processing.

An efficient and general protocol for copper-catalyzed N-arylation of aliphatic amines and amino acids has been developed using aryl iodides under mild conditions (coupling temperature at 25-35 °C). For the N-(o-nitrophenyl) amino acid derivatives, subsequent reduction of the nitro group in the presence of tin(II) chloride resulted in 3,4-dihydroquinoxalin-2(1H)-one derivatives in good yields.

The manufacture of high‐quality whole‐grain products is challenged by poor flavour attributes, such as excessive bitterness. In a recent study our group characterized eight compounds that contributed to the bitterness of a whole‐wheat bread sample. The goal of this study was to investigate the chemical profile of these bitter compounds in relation to the perceived bitterness of four commercial whole wheat breads and one refined wheat bread. Highly significant correlations (α = 0.01) were observed between the perceived bitterness in the crust and the quantity of 5‐(hydroxymethyl)furfural (r2 = 0.93) and 2,3‐dihydro‐3,5‐dihydroxy‐6‐methyl‐4(H)‐pyran‐4‐one (r2 = 0.95). In the crumb, the bitterness was correlated with the amount of l‐tryptophan (r2 = 0.91). In summary, both Maillard‐ and fermentation‐derived compounds were identified as potential chemical markers to predict bitterness of whole‐wheat bread. Copyright © 2012 John Wiley & Sons, Ltd.

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