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Gu F.,Spice and Beverage Research Institute | Chen Y.,Spice and Beverage Research Institute | Chen Y.,Qiongzhou University | Chen Y.,Huazhong Agricultural University | And 3 more authors.
Molecules | Year: 2015

Colonizing Bacillus in vanilla (Vanilla planifolia Andrews) beans is involved in glucovanillin hydrolysis and vanillin formation during conventional curing. The flavor profiles of vanilla beans under Bacillus-assisted curing were analyzed through gas chromatography-mass spectrometry, electronic nose, and quantitative sensory analysis. The flavor profiles were analytically compared among the vanilla beans under Bacillus-assisted curing, conventional curing, and non-microorganism-assisted curing. Vanilla beans added with Bacillus vanillea XY18 and Bacillus subtilis XY20 contained higher vanillin (3.58% ± 0.05% and 3.48% ± 0.10%, respectively) than vanilla beans that underwent non-microorganism-assisted curing and conventional curing (3.09% ± 0.14% and 3.21% ± 0.15%, respectively). Forty-two volatiles were identified from endogenous vanilla metabolism. Five other compounds were identified from exogenous Bacillus metabolism. Electronic nose data confirmed that vanilla flavors produced through the different curing processes were easily distinguished. Quantitative sensory analysis confirmed that Bacillus-assisted curing increased vanillin production without generating any unpleasant sensory attribute. Partial least squares regression further provided a correlation model of different measurements. Overall, we comparatively analyzed the flavor profiles of vanilla beans under Bacillus-assisted curing, indirectly demonstrated the mechanism of vanilla flavor formation by microbes. © 2015 by the authors; licensee MDPI, Basel, Switzerland. Source


Chen Y.,Spice and Beverage Research Institute | Chen Y.,Huazhong Agricultural University | Chen Y.,Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops | Gu F.,Spice and Beverage Research Institute | And 8 more authors.
Applied and Environmental Microbiology | Year: 2015

Vanilla beans were analyzed using biochemical methods, which revealed that glucovanillin disperses from the inner part to the outer part of the vanilla bean during the curing process and is simultaneously hydrolyzed by β-D-glucosidase. Enzymatic hydrolysis was found to occur on the surface of the vanilla beans. Transcripts of the β-D-glucosidase gene (bgl) of colonizing microorganisms were detected. The results directly indicate that colonizing microorganisms are involved in glucovanillin hydrolysis. Phylogenetic analysis based on 16S rRNA gene sequences showed that the colonizing microorganisms mainly belonged to the Bacillus genus. bgl was detected in all the isolates and presented clustering similar to that of the isolate taxonomy. Furthermore, inoculation of green fluorescent protein-tagged isolates showed that the Bacillus isolates can colonize vanilla beans. Glucovanillin was metabolized as the sole source of carbon in a culture of the isolates within 24 h. These isolates presented unique glucovanillin degradation capabilities. Vanillin was the major volatile compound in the culture. Other compounds, such as α-cubebene, β-pinene, and guaiacol, were detected in some isolate cultures. Colonizing Bacillus isolates were found to hydrolyze glucovanillin in culture, indirectly demonstrating the involvement of colonizing Bacillus isolates in glucovanillin hydrolysis during the vanilla curing process. Based on these results, we conclude that colonizing Bacillus isolates produce β-D-glucosidase, which mediates glucovanillin hydrolysis and influences flavor formation. © 2015, American Society for Microbiology. Source


Chen Y.-G.,Huazhong Agricultural University | Chen Y.-G.,Spice and Beverage Research Institute | Gu F.-L.,Spice and Beverage Research Institute | Gu F.-L.,Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops | And 8 more authors.
Current Microbiology | Year: 2015

A Gram-positive bacterium, designated strain XY18T, was isolated from a cured vanilla bean in Hainan province, China. Cells were rod-shaped, endospore producing, and peritrichous flagella. Strain XY18T grew at salinities of 0–8 % (w/v) NaCl (optimally 1–4 %), pH 4.0–8.0 (optimally 5.0–7.0 %) and temperature range 20–45 °C (optimally 28–35 °C). The predominant menaquinone was MK-7. The major cellular fatty acids were anteiso-C15:0, iso-C15:0, anteiso-C17:0, and iso-C17:0. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain XY18T was a member of the genus Bacillus, and closely related to B. amyloliquefaciens NBRC 15535T and B. siamensis PD-A10T, with 99.1 and 99.2 % sequence similarity, respectively. However, the DNA–DNA hybridization value between strain XY18T and B. amyloliquefaciens NBRC 15535T was 35.7 %. The genomic DNA G+C content of strain XY18T was 46.4 mol%, significantly differed from B. siamensis PD-A10T (41.4 %), which was higher than the range of 4 % indicative of species. On the basis of polyphasic taxonomic study, including phenotypic features, chemotaxonomy, and phylogenetic analyses, strain XY18T represents a novel species within the genus Bacillus, for which the name Bacillusvanillea sp. nov. is proposed. The type strain is XY18T (=CGMCC 8629 = NCCB 100507). © 2014, Springer Science+Business Media New York. Source


Dong Z.,Spice and Beverage Research Institute | Dong Z.,Huazhong Agricultural University | Dong Z.,Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops | Gu F.,Spice and Beverage Research Institute | And 6 more authors.
Food Chemistry | Year: 2014

Vanillin yield, microscopic structure, antioxidant activity and overall odour of vanilla extracts obtained by different treatments were investigated. MAE showed the strongest extraction power, shortest time and highest antioxidant activity. Maceration gave higher vanillin yields than UAE and PAE, similar antioxidant activity with UAE, but longer times than UAE and PAE. Overall odour intensity of different vanilla extracts obtained by UAE, PAE and MAE were similar, while higher than maceration extracts. Then, powered vanilla bean with a sample/solvent ratio of 4 g/100 mL was selected as the optimum condition for MAE. Next, compared with other three equations, two-site kinetic equation with lowest RMSD and highest Radj2 was shown to be more suitable in describing the kinetics of vanillin extraction. By fitting the parameters Ceq, k1, k2, and f, a kinetics model was constructed to describe vanillin extraction in terms of irradiation power, ethanol concentration, and extraction time. © 2013 Elsevier Ltd. All rights reserved. Source


Gu F.,Spice and Beverage Research Institute | Gu F.,Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops | Tan L.,Spice and Beverage Research Institute | Tan L.,Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops | And 6 more authors.
Food Chemistry | Year: 2013

This paper investigates polyphenol oxidase (PPO) activity, reduced weight percentage after sun drying, and the changes in colour and appearance of green pepper (Piper nigrum Linnaeus) berries after blanching and sun drying. The results show that the degree of reduced weight percentage and browning in green pepper berries after blanching for 10 min is greater at 100 °C than at 90 and 80 °C. Moreover, the samples blanched at 100 °C for 10 min had the fastest water loss, but the lowest PPO activity. Thus, the PPO enzymatic oxidation of polyphenols might not be the only reason for the browning of green pepper berries. This result is significantly different from that of Variyar, Pendharkar, Banerjeea, and Bandyopadhyay (1988) and therefore deserves further study. © 2012 Elsevier Ltd. All rights reserved. Source

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