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1.
J Agric Food Chem ; 69(35): 10272-10280, 2021 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-34436886

RESUMO

Salt is very important for human health and food seasoning. Recently, several peptides isolated from natural food products have been reported exhibiting a salty taste or a saltiness-enhancing function. In this investigation, taste-active peptides occurring in commercial Chinese fermented soybean curd were isolated and identified using ultrafiltration, gel permeation chromatography, ion-exchange chromatography, and nano-LC/Q-TOF MS/MS. The salty taste-enhancing function of the target fractions was confirmed by both a rat taste cell model and/or human sensory evaluation. Four decapeptides were found as taste-active compounds. Among them, peptide E (EDEGEQPRPF) was the most potent saltiness-enhancing peptide: 0.4 mg/mL in 50 mmol/L NaCl solution could increase its salty perception equivalent to the salt level of 63 mmol/L NaCl reference solution. The sequence of the peptide has been found in the α'-subunit of ß-conglycinin [Glycine max]. The remaining peptides V (VGPDDDEKSW), DD (DEDEQPRPIP), and DG (DEGEQPRPFP) showed umami and kokumi tastes as well as a weak saltiness-enhancing sensation. These findings suggest that the decapeptide EDEGEQPRPF could be a possible alternative to partially reduce the amount of sodium intake without compromising for saltiness.


Assuntos
Cloreto de Sódio , Alimentos de Soja , Animais , China , Peptídeos , Ratos , Alimentos de Soja/análise , Espectrometria de Massas em Tandem , Paladar
2.
J Food Biochem ; : e13840, 2021 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-34189733

RESUMO

The volatile organic compounds (VOCs) in four Chinese freshwater fishes (i.e., Hypophthalmichthys molitrix (H), Aristichthys nobilis (A), Lateolabrax japonicus (L), Parabramis pekinensis (P)) were separated using gas chromatography-ion mobility spectrometry (GC-IMS) and ultrafast gas chromatography electronic-nose (uf-GC E-nose). Principal component analysis (PCA) was applied to distinguish the VOCs identified from the four freshwater fishes in both raw and cooked states. Twenty compounds were identified from the spectral database of GC-IMS, including five aldehydes, eight alcohols, six ketones, and three esters. In addition, using GC E-nose, 32 compounds were isolated by the first column MTX-5, and 24 compounds were isolated by the second column MXT-1701. PCA results showed that the four fishes could be well discriminated against. The odor profiles of raw and cooked fishes were clearly different. This study demonstrated that specific signals provided from GC-IMS could differentiate freshwater fishes. GC-IMS and uf-GC E-nose could be developed further to distinguish aquatic products based on VOCs. PRACTICAL APPLICATIONS: Two new methods, gas chromatography-ion mobility spectrometry (GC-IMS) and ultrafast gas chromatography electronic-nose (uf-GC E-nose), were used to analyze the volatile organic compounds (VOCs) in four Chinese freshwater fishes at raw and cooked status. GC-IMS has the characteristics of fast detection speed and high sensitivity. The accuracy of the qualitative analysis of the compounds is better with GC-IMS (larger data volume, leading to a better in-depth statistical analysis). Uf-GC E-nose could provide a nondestructive, fast, relatively low cost, and trustworthy way for flavor analysis. According to the techniques, the established fingerprints of VOCs provided an additional tool for food analysis.

3.
Food Res Int ; 142: 110222, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33773696

RESUMO

Chinese dry-cured hams have unique aroma characteristics appreciated by local consumers. The volatile organic compounds (VOCs) of six selected Chinese dry-cured hams (Mianning, Nuodeng, Saba, Sanchuan, Wanhua, and Xuanen) were analyzed by solvent assisted flavor evaporation (SAFE) combined with GC × GC-ToF-MS and head-space (HS) injection combined with GC-IMS. To visualize VOCs and differentiate samples, principal component analysis (PCA) and multiple factor analysis (MFA) were performed. GC × GC-ToF-MS resulted in over five times more VOCs (265) than GC-IMS (45). However, PCA and MFA indicated similar results using GC-IMS or GC × GC-ToF-MS data, suggesting HS-GC-IMS as a good choice to differentiate dry-cured hams from different regions. Xuanen ham from Yunnan Province having smoky aroma was significantly different from other hams, likely due to its unique process. Many aldehydes (heptanal, nonanal, etc.) played an important role in Sanchuan ham. Ketones were related to other four dry-cured hams, though they came from different regions. This study provides valuable analytical data to characterize and discriminate the flavor profile of Chinese dry-cured hams.


Assuntos
Produtos da Carne , Carne de Porco , Compostos Orgânicos Voláteis , China , Cromatografia Gasosa-Espectrometria de Massas , Produtos da Carne/análise , Compostos Orgânicos Voláteis/análise
4.
J Agric Food Chem ; 67(50): 13829-13839, 2019 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-30969764

RESUMO

The formation pathways of α-diketones (2,3-butanedione and 2,3-pentanedione) and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) upon coffee roasting were investigated in a kinetic study applying labeled and unlabeled sucrose (CAMOLA approach) in biomimetic in-bean experiments. The results highlighted that not only did the contribution of sucrose to the level of α-diketones in roasted coffee change with the roasting degree but also the portion of the individual reaction pathways. At early roasting stages, 2,3-butanedione was formed from sucrose mainly via the intact sugar skeleton, whereas from the middle of the roasting course, the formation foremost occurred from sugar fragments, primarily by C1/C3 and C2/C2 recombinations. In contrast, 2,3-pentanedione was generated from sucrose mainly via an intact sugar skeleton during the whole roasting cycle; nevertheless, the share of 2,3-pentanedione formed by recombination of fragments (mainly C2/C3) progressively increased with roasting time. HDMF was generated from sucrose almost exclusively via cyclization of an intact skeleton, irrespective of the roast time.


Assuntos
Coffea/química , Culinária/métodos , Furanos/química , Cetonas/química , Café/química , Culinária/instrumentação , Temperatura Alta , Estrutura Molecular , Sementes/química
5.
J Agric Food Chem ; 66(10): 2422-2431, 2018 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-28013547

RESUMO

The origin and formation pathways of the buttery-smelling α-diketones 2,3-butanedione and 2,3-pentanedione upon coffee roasting were studied by means of biomimetic in-bean experiments combined with labeling experiments. For this purpose natural sucrose in the coffee bean was replaced by fully or partially 13C-labeled sucrose or by a mixture of unlabeled and fully 13C-labeled sucrose (CAMOLA approach). The obtained data point out that sucrose contributes to both α-diketones; however, its importance and reaction pathways clearly differ. Whereas the major part of 2,3-pentanedione originates from sucrose (about 76%), its contribution to 2,3-butanedione is much lower (about 35%). Formation from intact sugar skeleton is the major pathway generating 2,3-pentanedione from sucrose, whereas 2,3-butanedione is mainly generated by recombination of sucrose fragments. The contribution of glucose and fructose moieties of sucrose to both α-diketones is comparable. Finally, kinetic experiments with fully labeled sucrose showed that the contribution of sucrose changes during roasting.


Assuntos
Coffea/química , Cetonas/química , Sementes/química , Sacarose/química , Culinária , Temperatura Alta
6.
Trends Biotechnol ; 35(4): 279-281, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28283196

RESUMO

Here, we elaborate on the natural origin and use of enzymes and cultures in sustainable food processing. We also illustrate how enzymatically treated or fermented food can contribute to solving challenges involving nutrition and health, such as aging, malnutrition, obesity, and allergy.


Assuntos
Manipulação de Alimentos , Abastecimento de Alimentos , Saúde Global , Biotecnologia , Enzimas , Fermentação , Inocuidade dos Alimentos , Humanos
7.
Food Chem ; 218: 9-14, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-27719962

RESUMO

Chlorogenic acid lactones have been identified as key contributors to coffee bitterness. These compounds are formed during roasting by dehydration and cyclization of their precursors, the chlorogenic acids (CGAs). In the present study, we investigated an approach to decompose these lactones in a selective way without affecting the positive coffee attributes developed during roasting. A model system composed of (3-caffeoylquinic acid lactone (3-CQAL), 4- caffeoyl quinic acid lactone (4-CQAL), and 4-feruloylquinic acid lactone (4-FQAL)) was used for the screening of enzymes before treatment of the coffee extracts. Hog liver esterase (HLE) hydrolyzed chlorogenic acid lactones (CQALs, FQALs) selectively, while chlorogenate esterase hydrolyzed all chlorogenic acids (CQAs, FQAs) and their corresponding lactones (CQALs, FQALs) in a non-selective way. Enzymatically treated coffee samples were evaluated for their bitterness by a trained sensory panel and were found significantly less bitter than the untreated samples.


Assuntos
Ácido Clorogênico/análise , Café/química , Lactonas/análise , Extratos Vegetais/química , Animais , Ácidos Cafeicos/análise , Comportamento do Consumidor , Ácidos Cumáricos/análise , Esterases/metabolismo , Humanos , Hidrólise , Lipase/metabolismo , Fígado/enzimologia , Suínos , Paladar
8.
J Sci Food Agric ; 96(10): 3358-64, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26526345

RESUMO

BACKGROUND: Due to allergies or other health disorders a certain segment of the population is not able to safely consume some plant proteins, which are the main protein support in human nutrition. Coeliac disease is a prominent autoimmune disorder and requires a strict adherence to a gluten-free diet. The aim of this study was to identify suitable combinations of enzymatic hydrolysis and common unit operations in food processing (centrifugation, ultra-filtration) to produce gluten-free wheat gluten hydrolysates for food application. To analyse the hydrolysates, a simple and cheap competitive ELISA protocol was designed and validated in this study as well. RESULTS: The competitive ELISA was validated using gliadin spiked skim milk protein hydrolysates, due to the latter application of the assay. The limit of quantification was 4.19 mg kg(-1) , which allowed the identification of gluten-free (<20 mg kg(-1) ) hydrolysates. Enzymatic hydrolysis, including the type of peptidase, and the downstream processing greatly affected the antigenicity of the hydrolysates. CONCLUSION: Enzymatic hydrolysis and downstream processing operations, such as centrifugation and ultra-filtration, reduced the antigenicity of wheat gluten hydrolysates. Gluten-free hydrolysates were obtained with Flavourzyme after centrifugation (25 g L(-1) substrate) and after 1 kDa ultra-filtration (100 g L(-1) substrate). A multiple peptidase complex, such as Flavourzyme, seems to be required for the production of gluten-free hydrolysates. © 2015 Society of Chemical Industry.


Assuntos
Antígenos de Plantas/análise , Manipulação de Alimentos/métodos , Glutens/imunologia , Peptídeo Hidrolases/metabolismo , Triticum/química , Alérgenos/análise , Doença Celíaca/dietoterapia , Centrifugação , Dieta Livre de Glúten , Ensaio de Imunoadsorção Enzimática/métodos , Gliadina/análise , Glutens/química , Glutens/metabolismo , Humanos , Hidrólise , Proteínas de Plantas/imunologia , Ultrafiltração
9.
J Agric Food Chem ; 63(23): 5682-93, 2015 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-25996918

RESUMO

Flavourzyme is sold as a peptidase preparation from Aspergillus oryzae. The enzyme preparation is widely and diversely used for protein hydrolysis in industrial and research applications. However, detailed information about the composition of this mixture is still missing due to the complexity. The present study identified eight key enzymes by mass spectrometry and partially by activity staining on native polyacrylamide gels or gel zymography. The eight enzymes identified were two aminopeptidases, two dipeptidyl peptidases, three endopeptidases, and one α-amylase from the A. oryzae strain ATCC 42149/RIB 40 (yellow koji mold). Various specific marker substrates for these Flavourzyme enzymes were ascertained. An automated, time-saving nine-step protocol for the purification of all eight enzymes within 7 h was designed. Finally, the purified Flavourzyme enzymes were biochemically characterized with regard to pH and temperature profiles and molecular sizes.


Assuntos
Aspergillus oryzae/enzimologia , Endopeptidases/química , Endopeptidases/isolamento & purificação , Proteínas Fúngicas/química , Proteínas Fúngicas/isolamento & purificação , Aspergillus oryzae/química , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Peso Molecular , Temperatura
10.
Carbohydr Polym ; 98(1): 842-53, 2013 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-23987420

RESUMO

Extruded cereals mainly composed of starch and enriched in fibers were produced with two types of base recipes: (i) one recipe mainly composed of wheat flour and (ii) one recipe mainly composed of corn and soya flours. The addition of fibers was performed through the use of oat bran concentrate or wheat bran, up to 32% of the recipe. The structure of the extrudates, assessed by X-ray tomography, pointed out the decrease of porosity and of mean cells size with the increase of the total dietary fibers content of the recipe. The hardness of the products, i.e. the maximum stress determined by a compression test, was linked to their porosity. The Gibson-Ashby relationship could be applied and the fit was even improved when considering the walls of the solid foam as composite materials. Fibers and proteins can be indeed considered as particles dispersed in the starchy phase. This work thus shows the impact of the structure of the extrudates on their mechanical properties. The structure is taken into account at different length scales; at the level of the porous structure and at the level of the phase of the main biopolymers present in the recipe (starch, proteins and fibers). The mechanical behavior of these products is then discussed according to their characteristics of composite solid foams.


Assuntos
Fibras na Dieta , Grão Comestível/química , Manipulação de Alimentos/métodos , Amido/química , Fenômenos Mecânicos , Porosidade , Solubilidade
11.
Food Funct ; 4(7): 1105-10, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23685778

RESUMO

A fractional factorial experimental design was used to quantify the impact of process and recipe parameters on selected product attributes of extruded products (colour, viscosity, acrylamide, and the flavour marker 4-hydroxy-2,5-dimethyl-3(2H)-furanone, HDMF). The study has shown that recipe parameters (lysine, phosphate) can be used to modulate the HDMF level without changing the specific mechanical energy (SME) and consequently the texture of the product, while processing parameters (temperature, moisture) impact both HDMF and SME in parallel. Similarly, several parameters, including phosphate level, temperature and moisture, simultaneously impact both HDMF and acrylamide formation, while pH and addition of lysine showed different trends. Therefore, the latter two options can be used to mitigate acrylamide without a negative impact on flavour. Such a holistic approach has been shown as a powerful tool to optimize various product attributes upon food processing.


Assuntos
Aromatizantes/química , Farinha/análise , Indústria de Processamento de Alimentos/métodos , Furanos/química , Oryza/química , Ramnose/química , Acrilamida/análise , Cor , Culinária , Temperatura Alta , Reação de Maillard , Viscosidade
12.
J Agric Food Chem ; 61(43): 10215-9, 2013 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-23621440

RESUMO

The formation pathways of the N-containing roast-smelling compounds 2-acetyl-1-pyrroline, 2-acetyl-1(or 3),4,5,6-tetrahydropyridine, and their structural analogues 2-propionyl-1-pyrroline and 2-propionyl-1(or 3),4,5,6-tetrahydropyridine were studied upon extrusion cooking using the CAMOLA approach. The samples were produced under moderate extrusion conditions (135 °C, 20% moisture, 400 rpm) employing a rice-based model recipe enriched with flavor precursors ([U-(13)C6]-D-glucose, D-glucose, glycine, L-proline, and L-ornithine). The obtained data indicate that the formation of these compounds upon extrusion follows pathways similar to those reported for nonsheared model systems containing D-glucose and L-proline. 2-Acetyl-1-pyrroline is formed (i) by acylation of 1-pyrroline via C2 sugar fragments (major pathway) and (ii) via ring-opening of 1-pyrroline incorporating C3 sugar fragments (minor pathway), whereas 2-propionyl-1-pyrroline incorporates exclusively C3 sugar fragments. 2-Acetyl-1(or 3),4,5,6-tetrahydropyridine and the corresponding propionyl analogue incorporate C3 and C4 sugar fragments, respectively. In addition, it has been shown that the formation of 2-acetyl-1-pyrroline in low-moisture systems depends on the pH value of the reaction mixture.


Assuntos
Culinária , Aromatizantes/química , Oryza/química , Glucose/química , Reação de Maillard , Odorantes/análise , Prolina/química , Pirróis/química
13.
J Agric Food Chem ; 57(21): 9857-9, 2009 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-19817412

RESUMO

The 12th Weurman Flavour Research Symposium contributed 177 lectures and posters to the wealth of flavor knowledge; these were presented in eight sessions: biology, retention and release, psychophysics, quality, thermal generation, bioflavors, impact molecules, and analytics. Emerging topics were discussed in three workshops dealing with flavor and health, in vivo flavor research, and flavor metabolomics. It has been an excellent forum for passionate exchange of recent results obtained in traditional and emerging fields of flavor research. The symposium allowed coverage of the broad diversity of flavor-related topics: comprising odor and taste; applying targeted and holistic approaches; using sensorial, chemical, biological, physical, and chemometric techniques; as well as considering nutrition and health aspects.


Assuntos
Aromatizantes/química , Tecnologia de Alimentos , Humanos , Odorantes , Olfato
14.
J Agric Food Chem ; 57(21): 9923-31, 2009 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-19817414

RESUMO

The formation of several key odorants, such as 2-furfurylthiol (FFT), alkylpyrazines, and diketones, was studied upon coffee roasting. The approach involved the incorporation of potential precursors in green coffee beans by means of biomimetic in-bean and spiking experiments. Both labeled and unlabeled precursor molecules were used, and the target analytes in the roasted coffee samples were characterized in terms of their isotope labeling pattern and abundance. The biomimetic in-bean experiments ruled out the 2-furaldehyde route to FFT as suggested by model studies. Furthermore, no evidence was found for the incorporation of the arabinose C5 skeleton into FFT. Pathways proposed for the formation of alkylpyrazines and diketones were confirmed, and a new mechanism is suggested for the formation of 2-ethenyl-3-ethyl-5-methylpyrazine. The role of amino acids, for example, alanine, and free sugars was substantiated. The results underscore the potential of this methodology to provide better understanding of the formation pathways occurring in complex food systems, which may be different from those obtained in model experiments.


Assuntos
Coffea/química , Café/química , Odorantes/análise , Manipulação de Alimentos , Furanos/análise , Extratos Vegetais/análise , Compostos de Sulfidrila/análise
15.
J Agric Food Chem ; 57(21): 9972-8, 2009 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-19817421

RESUMO

The quality of coffee is influenced by many factors such as coffee variety, agricultural and postharvest conditions, roasting parameters, and brewing. The pleasure of drinking coffee may be affected by off-notes such as burnt, green, earthy, or fermented. Their presence is related to the variety, fermentation during postharvest processing, or over-roasting of the beans. Sensory expert panels trained for the evaluation of coffee are able to detect off-notes and select coffees by well-defined quality criteria. The application of instrumental approaches detecting quality markers related to the perceived off-notes is shown to be useful to assist sensory panels. This paper describes the discovery of a new marker compound related to the fermented off-note occasionally perceived in coffees. The application of untargeted chemometric methods on volatile compounds revealed correlations between individual compounds and the sensory attribute. The new marker compound was identified as ethyl formate, which can be measured in the headspace of roasted and ground coffee by various analytical techniques including online proton transfer reaction mass spectrometry.


Assuntos
Técnicas de Química Analítica , Coffea/química , Café/química , Fermentação , Ésteres do Ácido Fórmico/análise , Biomarcadores/análise , Técnicas de Química Analítica/métodos , Manipulação de Alimentos , Humanos , Controle de Qualidade , Paladar , Volatilização
16.
J Agric Food Chem ; 57(7): 2889-95, 2009 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-19256512

RESUMO

The formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) was studied in aqueous model systems containing L-rhamnose and L-lysine. The approach consisted in systematically varying four reaction parameters (rhamnose concentration, rhamnose to lysine ratio, pH, and phosphate concentration) at 3 levels. A fractional factorial design was used to reduce the number of trials. The degradation of rhamnose was followed by high performance anion exchange chromatography and the formation of HDMF by solid phase extraction in combination with GC/MS. The study permitted the identification of critical reaction parameters that affect the formation of HDMF from rhamnose in aqueous systems. Although all studied parameters have some impact on the HDMF formation and rhamnose degradation kinetics, the effect of phosphate is by far the most important, followed by concentration of precursors and pH. The experimental design approach permitted us, with a limited number of experiments, to accurately model the effects of the four investigated reaction parameters on the kinetics of rhamnose degradation and HDMF formation (R(2)>0.93). Overall, the results indicate that rhamnose can be an excellent precursor of HDMF (yield >40 mol%), if the reaction conditions are well mastered.


Assuntos
Furanos/síntese química , Ramnose/química , Cromatografia por Troca Iônica , Furanos/análise , Cromatografia Gasosa-Espectrometria de Massas , Concentração de Íons de Hidrogênio , Cinética , Lisina/química , Fosfatos/administração & dosagem , Fosfatos/análise , Ramnose/análise , Água
17.
Ann N Y Acad Sci ; 1126: 241-3, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18448822

RESUMO

The formation of acetic acid from pentoses was studied in aqueous buffered systems (90-120 degrees C, pH 6.0-8.0) containing equimolar concentrations of 13C-labeled xylose and glycine. Acetic acid was quantified by gas chromatography-mass spectroscopy using an isotope dilution assay. Acetic acid was mainly formed from the C-1/C-2 carbon atoms of xylose (77-87%), while small amounts were also formed from the C-4/C-5 atoms of the pentose sugar (9-15%). Temperature and pH had only a small effect on the relative contribution of the sugar carbon atoms to acetic acid. These results support beta-dicarbonyl cleavage of 1-deoxypento-2,4-diulose as a major pathway leading to acetic acid in pentose-based Maillard reaction systems under food processing conditions. Acetic acid was confirmed as a major degradation product of pentoses at the early stage of the Maillard reaction, yielding 16 mol% and 28 mol% at pH 6.0 and pH 8.0, respectively.


Assuntos
Ácido Acético/química , Reação de Maillard , Pentoses/química , Glicina/química , Hidrólise , Cinética , Xilose/química
18.
J Agric Food Chem ; 56(10): 3639-47, 2008 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-18439018

RESUMO

The formation of furan and 2-methylfuran was studied in model systems based on sugars and selected amino acids. Both compounds were preferably formed under roasting conditions in closed systems yielding up to 330 micromol of furan and 260 micromol of 2-methylfuran per mol of precursor. The amounts obtained under pressure cooking conditions were much lower, usually below 20 micromol/mol, except for 2-furaldehyde, which yielded 70-100 micromol/mol of furan. Labeling studies indicated two major formation pathways for both furans: (i) from the intact sugar skeleton and (ii) by recombination of reactive C(2) and/or C(3) fragments. Under roasting conditions in the absence of amino acids, furan was mainly formed from the intact sugar skeleton. Formic and acetic acid were identified as byproducts of sugar degradation, indicating the split off of C(1) and/or C(2) units from hexoses. The presence of alanine, threonine, or serine promoted furan formation by the recombination of C(2) fragments, such as acetaldehyde and glycolaldehyde, which may originate from both sugars and amino acids. In aqueous solution, about half of furan was generated by the recombination of sugar fragments. 2-Methylfuran was preferably formed in the presence of amino acids by aldol-type reactions of C(2) and C(3) fragments with lactaldehyde as a key intermediate, the Strecker aldehyde of threonine. The total furan levels in cooked vegetables were increased by spiking with hexoses. However, in pumpkin puree, only about 20% of furan was formed from sugars, preferably from the intact carbon skeleton.


Assuntos
Análise de Alimentos , Furaldeído/análogos & derivados , Furanos/síntese química , Reação de Maillard , Aminoácidos/química , Carboidratos/química , Manipulação de Alimentos/métodos , Furaldeído/análise , Furaldeído/síntese química , Furanos/análise , Temperatura Alta , Modelos Químicos , Pressão
19.
J Agric Food Chem ; 56(6): 2160-9, 2008 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-18298066

RESUMO

The temporal change in the headspace composition of an aroma model mimicking Longjing green tea aroma was studied in the presence of nonvolatile Longjing green tea constituents. Upon storage at 50 degrees C, the formation of 2-butyl-2-octenal was found, which increased with time. This enal was generated by crotonization of hexanal as demonstrated in model experiments. The formation of 2-butyl-2-octenal was also detected in Longjing tea infusions and Longjing tea leaves upon storage at 50 degrees C. The presence of nonvolatiles induced a strong decrease in aroma release. These effects were mainly due to catechins, major constituents of green tea infusion. Free amino acids, that is, glycine, contributed only to significantly decrease alpha,beta-unsaturated carbonyl aroma compounds, that is, 1-octen-3-one and geranial. Model reaction containing a mixture of 1-octen-3-one and glycine indicated on the basis of NMR and MS data the formation of the tentatively identified N-1-(3-oxo-octyl)glycine resulting from a 1,4-addition. The perceived aroma of green tea infusion is very likely to be affected by the formation of new aroma compounds and the changes in aroma release affected by interactions with tea nonvolatile components. This deserves further investigations on the sensory level.


Assuntos
Aldeídos/análise , Camellia sinensis/química , Odorantes/análise , Chá/química , Cromatografia Gasosa , Glicina/química , Humanos , Cetonas/química , Olfato , Fatores de Tempo , Volatilização
20.
Anal Chem ; 80(5): 1574-81, 2008 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-18220371

RESUMO

A robust and reproducible model was developed to predict the sensory profile of espresso coffee from instrumental headspace data. The model is derived from 11 different espresso coffees and validated using 8 additional espressos. The input of the model consists of (i) sensory profiles from a trained panel and (ii) on-line proton-transfer reaction mass spectrometry (PTR-MS) data. The experimental PTR-MS conditions were designed to simulate those for the sensory evaluation. Sixteen characteristic ion traces in the headspace were quantified by PTR-MS, requiring only 2 min of headspace measurement per espresso. The correlation is based on a knowledge-based standardization and normalization of both datasets that selectively extracts differences in the quality of samples, while reducing the impact of variations on the overall intensity of coffees. This work represents a significant progress in terms of correlation of sensory with instrumental results exemplified on coffee.

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