RESUMEN
A protocol was optimized to determine the volatile profile from monovarietal virgin olive oil (VOO) by multiple headspace solid-phase microextraction (MHS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analysis. For this, a Plackett-Burman (PB) and central composite rotational designs (CCRD) were used to define the best condition of extraction. Moreover, fatty acids profile and principal component analysis (PCA) was used to identify markers among the cultivars. The amount of 0.1 g of sample was enough to express the volatile composition of the olive oils by MHS-SPME. Volatile compounds [nonanal, (Z)-3-Hexen-1-ol, (Z)-3-Hexenyl Acetate, Hexyl Acetate, 3-Methylbutyl Acetate, (E)-2-Hexen-1-ol, (E)-2-Hexenyl Acetate] and fatty acids [C17:1, C18, C18:1, C18:2] were those reported such as the markers in the varieties of olive oils. The PCA analysis allowed the classification of the most representative volatiles and fatty acids for each cultivar. Through two principal components was possible to obtain 81.9% of explanation of the variance of the compounds. The compounds were quantified using a validated method. The MHS-SPME combined with multivariate analysis showed a promising tool to identify markers and for the discrimination of olive oil varieties.
Asunto(s)
Microextracción en Fase Sólida , Compuestos Orgánicos Volátiles , Microextracción en Fase Sólida/métodos , Aceite de Oliva/química , Brasil , Quimiometría , Compuestos Orgánicos Volátiles/análisis , Ácidos Grasos/análisisRESUMEN
Effect of yeast inoculation format (F), temperature (T), and "on lees" ageing time (t) factors were evaluated on the composition of sparkling wines by a quantitative fingerprint obtained from volatile metabolites and the response of an electronic nose (E-nose). Wines elaborated according the traditional method at 10 and 14 °C, free cells and yeast biocapsules formats were monitored at 15 and 24 months of ageing time. Sixty-six volatiles identified and quantified in the eight sampling lots were subjected to a pattern recognition technique. A dual criterion based on univariate (ANOVA) and multivariate analysis (PLS-DA) through the variable importance projection (VIP) values, allowed to identify ten volatiles as potential markers for T factor, eleven for t and twelve for F factors. The discriminant models based on E-nose dataset enable a 100% correct classification of samples, in relation with t and F factors and the 83% for T factor.
Asunto(s)
Nariz Electrónica , Saccharomyces cerevisiae/metabolismo , Compuestos Orgánicos Volátiles/análisis , Vino/análisis , Temperatura , Factores de TiempoRESUMEN
This study investigated the evolution of both free and bound volatile compounds in 'Shine Muscat' grape from post-fruit set to post-maturity and limiting factors of the lipoxygenase (LOX) pathway. C6 compounds and terpenes were the main free and bound volatile compounds, respectively. At pre-softening, volatile compounds concentrations were mainly regulated by expansion dilution, and terpene concentrations decreased significantly, which resulted in the minimum terpene concentrations occurred at softening. The volatile compounds were mainly regulated by metabolic synthesis at post-softening, and the production of C6 compounds, terpenes and esters largely began at 10, 12â¯weeks post-flowering and maturity stages, respectively. In the LOX pathway, LOX, alcohol dehydrogenase and the substrate alcohols were the limiting factors. The aroma maturity stages occurred at 15.4â¯weeks post-flowering. Finally, the developmental patterns of the volatile compounds in grape were summarized considering previous results in neutral and non-Muscat aromatic varieties.
Asunto(s)
Evolución Molecular , Vitis/química , Compuestos Orgánicos Volátiles/análisis , Alcohol Deshidrogenasa/metabolismo , Frutas/química , Frutas/metabolismo , Cromatografía de Gases y Espectrometría de Masas , Lipooxigenasa/metabolismo , Microextracción en Fase Sólida , Especificidad por Sustrato , Terpenos/análisis , Terpenos/aislamiento & purificación , Vitis/crecimiento & desarrollo , Vitis/metabolismo , Compuestos Orgánicos Volátiles/aislamiento & purificación , Compuestos Orgánicos Volátiles/metabolismoRESUMEN
Saccharomyces cerevisiae flor yeast is used for the first time in sparkling wine-making. Twenty-six oenological variables and fifty-three volatile metabolites are quantified in the middle (Pâ¯=â¯3â¯bar) and at the end (Pâ¯=â¯6â¯bar) of the second fermentation, carried out in open and closed bottles. A heat-map of volatiles and the fingerprints obtained for ten chemical families and ten odorant series visualize the changes for each condition. Terpenes, fatty acids and volatile phenols increased their contents by pressure effect at the end of the study by 25.0, 7.8 and 2.2%, respectively. The remaining families decrease between 17.4% and 30.1% for furanic compounds and esters in the same stage. A Principal Component Analysis established that nine volatiles are mainly affected by pressure and five by fermentation stage. The use of ethanol-tolerant flor yeasts constitutes an innovative procedure for the enhancement of the sparkling wines diversification.
Asunto(s)
Dióxido de Carbono/química , Fermentación , Saccharomyces cerevisiae/metabolismo , Vino/análisis , Dióxido de Carbono/análisis , Ésteres/análisis , Odorantes/análisis , PresiónRESUMEN
An integrated science-based approach, combining analytical and sensorial data and different data analysis methods, proved successful to study the impact of storage time, storage temperature and oxygen availability on strawberry juice volatiles and allowed to get a multi-perspective view on these changes. An untargeted GC-MS approach showed that the volatile fraction of shelf-stable strawberry juice clearly changed during ambient storage and that oxygen availability (linked to the type of bottle) had a limited effect. To gain further insight, several characteristic aroma compounds were quantified during storage at ambient (20⯰C) and accelerated (28-42⯰C) temperatures, kinetic parameters were estimated and odour activity values were calculated. The kinetic parameters showed that all characteristic aroma compounds changed significantly during storage at all temperatures and that the rate of change in some compounds was accelerated by storage at higher temperatures. The observed changes in strawberry juice volatiles caused sensorial differences between non-stored and 20⯰C stored samples as shown by the sensory evaluations and odour activity values.
Asunto(s)
Fragaria/química , Jugos de Frutas y Vegetales/análisis , Cromatografía de Gases y Espectrometría de Masas/métodos , Odorantes/análisis , Compuestos Orgánicos Volátiles/análisis , Frutas/química , Análisis MultivarianteRESUMEN
High quality sparkling wine made by the traditional method requires a second alcoholic fermentation of a base wine in sealed bottles, followed by an aging time in contact with yeast lees. The CO2 overpressure released during this second fermentation has an important effect on the yeast metabolism and therefore on the wine aroma composition. This study focuses on the changes in chemical composition and 43 aroma compounds released by yeast during this fermentation carried out under two pressure conditions. The data were subjected to statistical analysis allowing differentiating between the base wine and the wine samples taken in the middle and at the end of fermentation. The differentiation among wines obtained to the end of fermentation with or without CO2 pressure is only achieved by a principal component analysis of 15 selected minor compounds (mainly ethyl dodecanoate, ethyl tetradecanoate, hexyl acetate, ethyl butanoate and ethyl isobutanoate).
Asunto(s)
Vino , Dióxido de Carbono , Fermentación , Odorantes , Presión , Saccharomyces cerevisiae , Levadura SecaRESUMEN
The suitability of the cold storage (2°C) of fruit to maintain the quality of 'Manzanilla de Sevilla' and 'Manzanilla Cacereña' intended for virgin olive oil extraction was investigated. This temperature was effective in keeping the best commercial category of oil quality in both manually harvested olives and in mechanically harvested 'Manzanilla Cacereña' fruits for 11days. Mechanical harvesting induced significant decreases in oxidative stability and in the main phenolic compounds contents in the oils during cold storage and, only initially, in the total volatiles, regardless of the cultivar considered. However, the contents of volatile esters, associated to fruity flavor, were always higher in the oils from mechanically harvested fruits. 'Manzanilla de Sevilla' oils exhibited higher total volatiles during fruit cold storage, regardless of the harvesting system used.
Asunto(s)
Olea , Frío , Frutas , Aceite de Oliva , FenolesRESUMEN
The effect of Maillard reaction products (MRPs), formed during the production of dark malts, on the synthesis of higher alcohols and esters in beer fermentations was investigated by headspace solid-phase microextraction GC-MS. Higher alcohol levels were significantly (p<0.05) higher in dark malt fermentations, while the synthesis of esters was inhibited, due to possible suppression of enzyme activity and/or gene expression linked to ester synthesis. Yeast strain also affected flavour synthesis with Saccharomyces cerevisiae strain A01 producing considerably lower levels of higher alcohols and esters than S288c and L04. S288c produced approximately double the higher alcohol levels and around twenty times more esters compared to L04. Further investigations into malt type-yeast strain interactions in relation to flavour development are required to gain better understanding of flavour synthesis that could assist in the development of new products and reduce R&D costs for the industry.
Asunto(s)
Cerveza , Ésteres , Fermentación , Alcoholes , Reacción de MaillardRESUMEN
Nine wines obtained by fermenting Aligoté musts with individual starter cultures of eight Saccharomyces cerevisiae yeast strains and with the indigenous microbiota were compared in terms of their composition in minor volatile aroma compounds. An easy handle methodology Stir-Bar-Sorptive-Adsorption, Gas Chromatography-Mass Spectrometry based, permits the identification of 49 aroma compounds. The rearrangement of these aroma compounds in six chemical families permits the establishment of a finger printing for each wine. Eighteen aroma compounds that exhibit a high differentiation power (p⩽0.05) were selected for chemometric analysis. The Principal Component Analysis carried out with these aroma compounds reveal that the first two principal components explain 53.8% and 17.2% of the total variance, respectively, allowing the establishment of nine different groups, in accordance with the wine types obtained. These results reveal analytical differences among the wines that are not recognized by sensorial analysis.