Multi-response kinetic modelling of the formation of five Strecker aldehydes during kilning of barley malt.

Control of aroma formation during production of barley malt is critical to provide consistent and high-quality products for the brewing industry. Malt quality can be affected by the inherent variability of raw material and processing conditions, leading to inconsistent and/or undesirable profiles. Dried green malts were cured isothermally at 65, 78 and 90 °C for 8.4 h, and characteristic aroma compounds (Strecker aldehydes), precursors and intermediate compounds were analysed over time. By kinetic modelling of Strecker aldehydes, based on fundamental chemical pathways, we showed that degradation of Amadori rearrangement products and short-chain dicarbonyls was more sensitive to temperature change due to their higher activation energies compared to other kinetic steps. This study can help maltsters to manipulate formation of Strecker aldehydes, via raw material screening and process control, and hence optimise the organoleptic quality of malts and their products, such as non-alcoholic beers, where these aldehydes play a key role.

Accurate quantitative determination of the total amounts of Strecker aldehydes contained in wine. Assessment of their presence in table wines.

Strecker aldehydes (SAs) are key determinants of wine shelf-life and can be present in unoxidized wines in odorless forms, such as hydroxyalkylsulfonates, imines or acetals. A robust and accurate method for the determination of total forms of SAs, based on the classical derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and in the selective solid phase extraction of derivatives has been optimized and validated. Matrix effects have been solved by the use of adequate internal standards and by large-enough equilibration times under anoxic conditions. Method figures of merit are highly satisfactory in terms of detection limits (<0.1 µg/L), linearity (R2 > 0.997), reproducibility (5-13%) and recoveries (RSDs, between 2 and 10%, for 3-methylbutanal, 14%). The analysis of total SAs in 108 Spanish wines revealed that between 52% and 70% of unoxidized red wines and likely a similar fraction of white wines, contain levels of SAs high enough to cause oxidative aromas if bound forms of SAs cleave.

Characterization of the aroma-active compounds in black soybean sauce, a distinctive soy sauce.

Black soybean sauce's (BSS) aroma was scarcely investigated, which seriously affected BSS's quality and consumers' preference. Thus the aroma compounds in BSS were characterized using gas chromatography-mass spectrometry/gas chromatography-olfactometry coupling with recombination and omission experiments. Sensory evaluation showed the fruity odor was increased by 63% and the malty, alcoholic, floral, smoky, caramel-like and sour odors were decreased by 24-35% when compared to the control soy sauce (SS, p < 0.05). Totally, 126 volatile compounds, 44 aroma-active compounds and 22 vital aroma-active compounds were identified in BSS. Compared to SS, BSS exhibited a distinctive aroma characteristics which was caused by significantly higher odor activity values (OAVs) of 3-methylbutyl acetate (357%), ethyl propanoate (144%), ethyl 3-methylbutanoate (70%), ethyl 2-methylbutanoate (102%) and lower OAVs of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (52%), 4-hydroxy-2-ethyl-5-methyl-3(2H)-furan-3-one (50%), ethanol (48%), 4-vinylguaiacol (41%), 3-methylthiopropanal (37%), 3-methylbutanol (33%), 4-ethylguaiacol (28%). The results would contribute to BSS's quality control and aroma improvement.

Analysis of volatile compounds of five varieties of Maya cocoa during fermentation and drying processes by Venn diagram and PCA.

Fermented cocoa beans can be described as a complex matrix that integrates the chemical history of beans, their processing, and environmental factors. This study presents an analysis that aims to identify volatile compounds of five varieties of fine-aroma cocoa types. The cocoa types studied were Carmelo, Rojo Samuel, Lagarto, Arcoiris, Regalo de Dios, that grow in the Maya lands of Chiapas, Mexico. Profile of volatile compounds was obtained from each cacao type during fermentation and drying process. This profile of volatile compounds also was compared with beans unfermented, using a statistical analysis of Venn diagram and a multivariate Analysis of Principal Components (PCA). One hundred nine different compounds were identified by SPME-HS GC-MS, these compounds mainly related to desirable aromatic notes generated by esters, aldehydes, ketones, and alcohols. The differences in chemical composition of the volatile compounds were associated mainly with the process and not to cocoa varieties. Fermented dry cocoa beans showed a higher content of esters, aldehydes, pyrazines, alcohols, some acids, and furans where Lagarto (CL), Rojo Samuel (CR), and Regalo de Dios (TRD) cocoas type showed a more interesting aromatic profile. On the other hand, as expected dry unfermented cocoas presented a few numbers of aroma compounds, in the five cacao types, where alcohols, ketones and hydrocarbons predominated.

Analysis of volatile compounds of Lentinula edodes grown in different culture substrate formulations.

Volatile compounds of Lentinula edodes grown in different culture substrate (CS) formulations were analyzed to reveal (i) the relationship between volatile compound production and CS formulations, (ii) the contribution of volatile compounds to L. edodes flavor, (iii) the activities of LOX and γ-GGT enzymes, (iv) γ-GGT gene expression, and (v) the correlation between enzyme activity and volatile compound production. Our results showed that 82 kinds of volatile compounds were analyzed; 25 volatile compounds were considered key flavor components, and sulfur containing compounds, eight-carbon compounds, and aldehyde compounds also had great contributions to mushroom flavor. Bagasse could be used as a partial substitute for sawdust as a carbon source. LOX and γ-GGT activities showed a weak correlation with the volatile end products. The results indicated that the mechanisms by which CS formulations influence volatile compounds production were complex.

Impact of sodium reduction strategies on volatile compounds, sensory properties and consumer perception in commercial wheat bread.

The efficacy of two sodium reduction strategies in preserving sensory profile and consumer liking of yeasted wheat bread was tested, by combining sensory data, aroma compounds and consumer investigations. The use of (i) a reduced-sodium salt substitute, Pansalt® (NaCl 57%, other salts and minor ingredients) at 1.5%, and (ii) the heterogeneous NaCl distribution (average level of 1%) leading to enhanced saltiness by taste contrast, were compared with standard (1.5%) and reduced (1.0%) addition of NaCl. The heterogeneous NaCl distribution was effective in preserving saltiness. Salt substitution with Pansalt® was less effective but preserved the overall flavour. Higher amount of Maillard reaction volatile products, associated with more intense toasted odour of the crust, was found in breads with higher NaCl content. The consumer survey highlighted satisfactory results of Pansalt® use for 58% of the respondents (equal or higher liking and purchase intention). Heterogeneous salt distribution was effective for 31% of consumers.

Enantiomeric ratios of 2-methylbutanoic acid and its methyl ester: Elucidation of novel biogenetic pathways towards (R)-methyl 2-methylbutanoate in a beverage fermented with shiitake.

Up to 35% of (R)-methyl 2-methylbutanoate (M2MB) was observed in a beverage fermented with shiitake. As M2MB naturally occurs typically in high excesses of the (S)-enantiomer, the origin of the (R)-ester was elucidated by stable isotope labeled precursor-feeding studies. (R)-2-Methylbutanoic acid was identified as the main precursor in the substrate wort. Trace amounts of (R)-M2MB were produced by transformation of unsaturated secondary metabolites (tiglic aldehyde and tiglic acid) derived from l-isoleucine. Surprisingly, shiitake esterified (R)-2-methylbutanoic acid faster to (R)-M2MB than the corresponding (S)-enantiomer. Concurrently, spontaneous non-enantioselective degradation of M2MB occurred in shiitake. This explains diverse enantiomeric ratios of M2MB and different enantiomeric ratios of 2-methylbutanoic acid and M2MB in the beverage. As the odor threshold values of (R)-and (S)-M2MB differ significantly, these findings are of high relevance for the overall flavor of the fermented beverage and elucidate the discrepancy of enantiomeric ratios of 2-alkyl-branched acids and esters reported in nature.

Effect of chemical composition and high pressure processing on the volatile fraction of Serrano dry-cured ham.

The volatile fraction of 30 Serrano dry-cured hams with different salt and intramuscular fat contents was investigated. In addition, the effect of high pressure processing (HPP) at 600 MPa for 6 min at 21°C on the volatile compounds of those hams was studied. One hundred volatile compounds were identified and their levels subjected to analysis of variance with ham chemical composition (aw, salt content, intramuscular fat content and salt in lean ratio) and HPP treatment as main effects. Chemical composition mainly affected the relative abundance of acids, alcohols, branched-chain aldehydes, ketones, benzene compounds, sulfur compounds and some miscellaneous compounds. Salt content and fat content influenced a greater number of volatile compounds than aw. High pressure processing had a significant effect on only 8 volatile compounds, with higher levels of methanethiol and sulfur dioxide in HPP-treated samples and higher levels of ethyl acetate, ethyl butanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, dimethyl disulfide and dimethyl trisulfide in control untreated samples.

Variation of volatile compounds among wheat varieties and landraces.

Analysis of volatile compounds was performed on 81 wheat varieties and landraces, grown under controlled greenhouse conditions, in order to investigate the possibility of differentiating wheat varieties according to their volatile compound profiles. Volatile compounds from wheat samples were extracted by dynamic headspace extraction and analysed by gas chromatography-mass spectrometry. Seventy-two volatile compounds were identified in the wheat samples. Multivariate analysis of the data showed a large diversity in volatile profiles between samples. Differences occurred between samples from Austria compared to British, French and Danish varieties. Landraces were distinguishable from modern varieties and they were characterised by higher averaged peak areas for esters, alcohols, and some furans. Modern varieties were characterised by higher averaged peak areas for terpenes, pyrazines and straight-chained aldehydes. Differences in volatile profiles are demonstrated between wheat samples for the first time, based on variety. These results are significant to plant breeders and commercial users of wheat.

Modelling the Maillard reaction during the cooking of a model cheese.

During processing and storage of industrial processed cheese, odorous compounds are formed. Some of them are potentially unwanted for the flavour of the product. To reduce the appearance of these compounds, a methodological approach was employed. It consists of: (i) the identification of the key compounds or precursors responsible for the off-flavour observed, (ii) the monitoring of these markers during the heat treatments applied to the cheese medium, (iii) the establishment of an observable reaction scheme adapted from a literature survey to the compounds identified in the heated cheese medium (iv) the multi-responses stoichiokinetic modelling of these reaction markers. Systematic two-dimensional gas chromatography time-of-flight mass spectrometry was used for the semi-quantitation of trace compounds. Precursors were quantitated by high-performance liquid chromatography. The experimental data obtained were fitted to the model with 14 elementary linked reactions forming a multi-response observable reaction scheme.