Huanlu Song

A comparative study of aroma-active compounds between dark and milk chocolate: relationship to sensory perception.

BACKGROUND The most important aroma-active compounds of two types of chocolate and cocoa liquor used for their production were analysed by gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and aroma extract dilution analysis (AEDA). Furthermore, the relationship between odorants and sensory perception of chocolate was measured by quantitative analysis, sensory evaluation and correlation analysis. In addition, some chemicals were added to the original dark or milk chocolate to validate their roles in the aroma property of chocolate. RESULTS A total of 32 major aroma-active compounds were identified in the chocolate with the flavour dilution factors of 27-729 by AEDA, including seven aldehydes, six pyrazines, three pyrroles, four carboxylic acids, four lactones, two alcohols, two ketones, one ester, one pyrone, one furan and one sulfur-containing compound. Further quantitative analysis showed that dark chocolate had higher contents of pyrazine, pyrrole, carboxylic acids, alcohols and Strecker aldehydes, whereas the concentration of lactones, esters, long chain aldehydes and ketones were higher in the milk type. CONCLUSION Differences in volatile composition and descriptive flavour attributes between the dark and milk chocolate were observed. The relationship between aroma-active compounds and sensory perception in the chocolate was verified.

Discovery of kokumi peptide from yeast extract by LC-Q-TOF-MS/MS and sensomics approach

BACKGROUND Yeast extract can impart thickness, complexity and long-lasting taste impression, coined kokumi taste, to blank chicken broth. In this research, the kokumi-active peptide in yeast extract was discovered by ultrafiltration, liquid chromatographic and quadrupole-time-of-flight-tandem mass spectrometric technologies. Furthermore, the sensory characters of these peptides were evaluated by a sensomics approach. RESULTS A total of 10 kokumi peptides were identified from yeast extract. They were γ-Glu-Cys-Gly, γ-Glu-Leu, γ-Glu-Val, γ-Glu-Tyr, Leu-Lys, Leu-Gln, Leu-Ala, Leu-Glu, Leu-Thr and Ala-Leu. Apart from the well-known kokumi-active glutathione and γ-glutamyl dipeptides, five leucyl dipeptides were first proposed having kokumi activity. Among them, Ala-Leu was found to have the highest kokumi threshold concentration (1.5 mmol L(-1) ) in the blank chicken broth, while Leu-Glu was the lowest (0.3 mmol L(-1) ). A subsequent dose-response experiment indicated that the bitter-tasting leucyl dipeptides could impart kokumi taste to chicken broth at low concentrations (less than bitter threshold concentrations). Interestingly, the kokumi sensation began to decrease when such peptides exceeded the threshold concentration by approximately 16-fold in the blank chicken broth. CONCLUSION Key kokumi-active fractions were purified from yeast extract. Among them, ten important kokumi peptides from yeast extract were identified.

Response Surface Methodology for Meat‐Like Odorants from the Maillard Reaction with Glutathione II: The Tendencies Analysis of Meat‐Like Donors

Understanding the flavor effect of molecules on food products is fundamental for the food technologist. In this study, the formation of different meat-like compounds was controlled by various influence factors. Furthermore, the concept of interrelationships between Maillard reaction products (MRPs) was demonstrated by statistical analysis for the first time, which provides data and hence production system parameters by which to generate and optimize meat-like flavors through Maillard reactions. We report here the analysis and synthesis trend of the 13 meat-like donors which are regarded as forming the major flavor compounds of cooked meat. Response surface methodology (RSM) has not previously been reported in the literature as a technique to identify which parameters have the greatest influence on the synthesis of these flavor compounds. RSM has been used here to identify the influence of initial pH and ΔpH on flavor compound generation. As all ΔpH had positive RSM values between 0.5 and 1.5 it can be concluded that MRPs of this meat flavor-adapted system would be mostly acidic. These positive values also indicate that under this condition the Maillard reaction is stable and will therefore promote more meat-like flavor compounds to be generated. In addition to ΔpH, varied concentrations of glutathione, cysteine, thiamine, and xylose were investigated for their ability to influence the generation of meat-like flavors.

Response surface methodology for meat-like odorants from Maillard reaction with glutathione I: the optimization analysis and the general pathway exploration.

This study is about reaction condition optimization and exploration of the general pathway of GSH-participating Maillard reaction. Response surface methodology (RSM) is used to define the reaction condition for optimal meat flavor product generation from synthetic oligopeptides via the Maillard reaction. The optimal reaction condition is: (A) temperature: 131.53 °C, (B) reaction time: 94.85 min, (C) volume of 0.2M phosphate buffer: 49.61 mL and (D) initial pH of reactants: 4.79. The priority sequence is: A > D > C > B, and the verification score was 9.1. A preliminarily pathway scheme using CAMOLA has been constructed to suggest a reaction mechanism for meat-like aroma product formation. In addition, a 2-pathway and 3-stage formation scheme of the GSH-participating Maillard reaction has been constructed.

Characterization and comparison of key aroma-active compounds of cocoa liquors from five different areas

ABSTRACT The volatile constituents of cocoa liquor and the differences between cocoa liquors from different origins were studied. Direct solvent extraction-solvent assisted flavor evaporation and gas chromatography-olfactrometry-mass spectrometry in conjunction with aroma extract dilution analysis were used to identify the key flavor compounds in five cocoa liquors. There were significant differences of specific compounds between cocoa liquor from different areas of origins. Then, the purge and trap method was used to gathering the aroma-active components of five cocoa liquors from different origins, and one internal standard was used during this process for the further quantitative analysis by gas chromatography-olfactrometry-mass spectrometry. The results indicated that 3-methylbutanal, acetic acid, tetramethylpyrazine, and 3-methylbutanoic acid were the components with high concentrations. The contents of most compounds in the five kinds of cocoa liquor were dramatically different. The content of odorants of cocoa liquors from Papua New Guinea was higher than that of the others and that from Indonesia was the lowest. For sensory evaluation, the overall odor outlines of the five cocoa liquors were very similar, the Papua New Guinea cocoa liquor had higher preference than those of the other four samples. Principal component analysis showed that the characteristics of cocoa liquor from Papua New Guinea, Indonesia, and Ivory Coast were very significant.

Comparison of Four Extraction Methods, SPME, DHS, SAFE, Versus SDE, for the Analysis of Flavor Compounds in Natto

Natto is a kind of traditional fermentation food. Organic soybean of china northeast was selected as the material to produce natto according to the condition optimized before. Four extraction methods (SAFE (solvent-assisted flavor evaporation), SDE (simultaneous distillation and extraction), SPME (solid phase microextraction), and DHS (dynamic headspace sampling)) were applied to extract the volatile compounds of natto. Aroma compounds were separated and analyzed with gas chromatography-olfactometry-mass spectrometry (GC-MS/O) of DB-5 and DB-Wax capillary columns. Seventy-seven compounds were identified by four extraction methods. Among them, 42, 23, 31, and 36 compounds were identified by SPME, DHS, SDE, and SAFE, respectively. SAFE and SDE had a better extraction effect on ester, ether, and aromatic compounds, while SPME and DHS could extract ketone, acid, and pyrazine compounds effectively. SPME was fit for the extraction of natto aroma compounds. These compounds included 14 ketones, 9 alcohols, 4 aldehydes, 6 acids, 4 sulfur compounds, 5 esters, 8 pyrazines, 19 aromatics, and 8 others. Fourteen compounds were identified as key aroma compounds in natto, including 2,3-butanedione, 5-methyl-2-hexanone, 3-hydroxy-2-butanone, 2-nonanone, furaldehyde, acetic acid, 2-ethyl butyric acid, ethyl acetate, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, 3,5-dimethyl-2-ethylpyrazine, 2,3,5,6-tetramethylpyrazine, 2,3,5-methyl-6-ethylpyrazine, and benzaldehyde. Pyrazine was the important aroma compound with the high FD (flavor dilution) value in natto.

Flavour-active compounds in thermally treated yeast extracts: Flavour-active compounds in thermally treated yeast extracts

BACKGROUND Aroma-active compounds and non-volatile substances determine the characteristic aroma and taste of yeast extract (YE). Changes in the characteristic aroma and taste of YE due to thermal reaction are rarely studied, and the relationship between aroma-active compounds and non-volatile compounds is not yet clear. RESULTS Non-volatile compounds identified by HPLC and LC/MS/MS were reduced by a rise in temperature, except for some amino acids. Peptides underwent degradation. In addition, a further rise in temperature above 120 °C resulted in a bitter and sour taste. Furans, pyrazines, thiophenes, thiazoles and some branched chain sulfur compounds were derived from GC/O/MS (SPME and SAFE). Sensory results revealed that the concentration of volatile compounds increased with an increase in temperature. The overall aroma profiles of YE at 25, 100 and 110 °C were buttery, green, nutty and meaty, while YE at 140 °C had a strong sour and sulfur odour. CONCLUSION The non-volatile compounds of YE were reduced and different volatile compounds were produced under different thermal treatments. There was a negative correlation between these two types of compounds. The different taste sensors and all precursors were correlated with each other. There are significant relationships between different odorants and aroma-active compounds of YE after thermal treatment.

Determination of the key aroma compounds in Sachima and using solid phase micro extraction (SPME) and solvent-assisted flavour evaporation (SAFE)-gas chromatography-olfactometry-mass spectrometry (GC-O-MS)

ABSTRACT The aroma-active compounds present in Sachima samples purchased at retail from the same batch code and stored for different durations of the shelf life were analysed by two methods: solid phase micro extraction (SPME) and solvent-assisted flavour evaporation (SAFE)-gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 41 volatile key compounds were identified. Among them, the predominant compounds in Sachima were tentatively identified by dilution analysis as being 3-(methylthio)propionaldehyde, 2-pentylfuran, 2-methyl-3-(methylthio)pyrazine, dimethyl disulfide, and dipropyl trisulfide. These compounds produced the highest due to their highest calculated flavour dilution (FD) factors. Sensory evaluations of the extracted compounds by a panel of trained individuals revealed that the ‘egg’ aroma was the main characteristic aroma due to its high sensory assessment score. With increasing length of storage of the product from 0 to 10 months, the overall acceptability of the Sachima aroma declined gradually. The observed changes in concentration of the different volatile compounds during storage indicated that the Maillard reaction and lipid oxidation continued during storage, so that aroma compounds and off-flavour compounds were being generated simultaneously. In addition, the undesirable smell of Sachima that increased during storage was not just generated from one volatile compound with a distinct off-flavour, but rather it was the result of an increase in both pleasant and unpleasant aromas. Furthermore, the pleasant aroma components appeared to still play a dominant role in the overall aroma profile of Sachima even after 10 Months of storage, which is within the stated shelf life on the product label.

Correlation between the key aroma compounds and gDNA copies of Bacillus during fermentation and maturation of natto

The aim of the study was to analyze the correlation between the key aroma compounds and gDNA copies of Bacillus natto during fermentation and maturation of natto. Solvent-assisted flavor evaporation (SAFE) techniques were employed to extract volatile organic compounds. Aroma compounds were separated and analyzed through gas chromatography-olfactometry-mass spectrometry (GC-MS/O) using DB-5 and DB-Wax capillary columns. Seventy-nine compounds were extracted and identified, including 17 ketones, 17 alcohols, 9 aldehydes, 6 acids, 7 esters, 8 pyrazines, 8 aromatics, and 7 others. Twenty-two compounds were identified as the key aroma compounds of natto by aroma extraction dilution analysis (AEDA). Pyrazines played a key role in the flavor of natto both during the fermentation and maturation. 2,5-Dimethylpyrazine, 2,3,5-trimethylpyrazine, 2,3,5,6-tetramethylpyrazine, and 2,3,5-methyl-6-ethylpyrazine contributed substantially to natto flavor. They presented significant positive and negative correlations with the gDNA copies of Bacillus natto during fermentation and maturation, respectively.

Comparison of fresh watermelon juice aroma characteristics of five varieties based on gas chromatography-olfactometry-mass spectrometry

Qualitative and quantitative analysis and odor active value (OAV) calculation were applied to identify the aroma-active compounds of fresh watermelon juice in five varieties: Seedless, Jingxin, Lianfa, Qilin, and Texiaofeng. Principal component analysis and cluster analysis were selected to compare the similarity and difference among watermelons juices. Fifty-five volatiles were identified in watermelon juice in five varieties, among which 6 volatiles were identified for the first time in watermelon. (Z)-6-nonenal, (E, Z)-2,6-nonadienal, (E)-2-nonenal, and (E, E)-2,4-nonadienal contributed greater to aroma profiles than alcohols due to lower threshold through odor active values. It was indicated by principal component analysis and cluster analysis that watermelon juices were separated into three groups, Jingxin, Lianfa-Texiaofeng, and Seedless-Qilin, whose characteristic volatiles were aldehydes, alcohols, and ketones respectively. The average distance between JX and the other varieties was higher than that of others through cluster analysis, indicating that the aroma of Jingxin differed from that of the other four varieties greatly.