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Featured researches published by Fenglin Gu.
Food Chemistry | 2014
Zhizhe Dong; Fenglin Gu; Fei Xu; Qinghuang Wang
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 R²(adj) was shown to be more suitable in describing the kinetics of vanillin extraction. By fitting the parameters C(eq), k₁, k₂, and f, a kinetics model was constructed to describe vanillin extraction in terms of irradiation power, ethanol concentration, and extraction time.
Foods | 2013
Fenglin Gu; Lehe Tan; Huasong Wu; Yiming Fang; Fei Xu; Zhong Chu; Qinghuang Wang
A survey on five kinds of cocoa beans from new cocoa planting countries was conducted to analyze each kind’s basic quality. The average bean weight and butter content of Hainan cocoa beans were the lowest, at less than 1.1 g, and 39.24% to 43.44%, respectively. Cocoa beans from Indonesia where shown to be about 8.0% and 9.0% higher in average bean weight and butter content, respectively, than that of Papua New Guinea and about 20.0% and 25.0% higher in average bean weight and butter content than Chinese dried beans, respectively. The average total polyphenolic content ranged from 81.22 mg/10 g to 301.01 mg/10 g. The Hainan 2011 sample had the highest total polyphenolic content, followed by the unfermented sample from Indonesia and the Papua New Guinea sample. The polyphenolic levels found in the Hainan 2010 sample were 123.61 mg/10 g and lower than the other three samples, but the Indonesian fermented sample had the lowest total polyphenolic content of 81.22 mg/10 g. The average total amino acid content ranged from 11.58 g/100 g to 18.17 g/100 g. The total amino acid content was the highest in the Indonesian unfermented sample, followed by the Hainan 2011 sample and the Papua New Guinea sample. The levels found in the Hainan 2010 sample were lower; the Indonesian fermented sample had the lowest total amino acid content.
Molecules | 2012
Fenglin Gu; Fei Xu; Lehe Tan; Huasong Wu; Zhong Chu; Qinghuang Wang
Vanillin was extracted from vanilla beans using pretreatment with cellulase to produce enzymatic hydrolysis, and response surface methodology (RSM) was applied to optimize the processing parameters of this extraction. The effects of heating time, enzyme quantity and temperature on enzymatic extraction of vanillin were evaluated. Extraction yield (mg/g) was used as the response value. The results revealed that the increase in heating time and the increase in enzyme quantity (within certain ranges) were associated with an enhancement of extraction yield, and that the optimal conditions for vanillin extraction were: Heating time 6 h, temperature 60 °C and enzyme quantity 33.5 mL. Calculated from the final polynomial functions, the optimal response of vanillin extraction yield was 7.62 mg/g. The predicted results for optimal reaction conditions were in good agreement with experimental values.
Molecules | 2014
Yanjun Zhang; Limei Mo; Feng Chen; Minquan Lu; Wenjiang Dong; Qinghuang Wang; Fei Xu; Fenglin Gu
Production of vanillin from natural green vanilla pods was carried out by enzyme-assisted extraction combined with pre-freezing and thawing. In the first step the green vanilla pods were pre-frozen and then thawed to destroy cellular compartmentation. In the second step pectinase from Aspergillus niger was used to hydrolyze the pectin between the glucovanillin substrate and β-glucosidase. Four main variables, including enzyme amount, reaction temperature, time and pH, which were of significance for the vanillin content were studied and a central composite design (CCD) based on the results of a single-factor tests was used. Response surface methodology based on CCD was employed to optimize the combination of enzyme amount, reaction temperature, time, and pH for maximum vanillin production. This resulted in the optimal condition in regards of the enzyme amount, reaction temperature, time, and pH at 84.2 mg, 49.5 °C, 7.1 h, and 4.2, respectively. Under the optimal condition, the experimental yield of vanillin was 4.63% ± 0.11% (dwb), which was in good agreement with the value predicted by the model. Compared to the traditional curing process (1.98%) and viscozyme extract (2.36%), the optimized method for the vanillin production significantly increased the yield by 133.85% and 96%, respectively.
AMB Express | 2017
Fenglin Gu; Yonggan Chen; Yinghua Hong; Yiming Fang; Lehe Tan
High-performance liquid chromatography–mass spectrometry (LC–MS) was used for comprehensive metabolomic fingerprinting of vanilla fruits prepared from the curing process. In this study, the metabolic changes of vanilla pods and vanilla beans were characterized using MS-based metabolomics to elucidate the biosynthesis of vanillin. The vanilla pods were significantly different from vanilla beans. Seven pathways of vanillin biosynthesis were constructed, namely, glucovanillin, glucose, cresol, capsaicin, vanillyl alcohol, tyrosine, and phenylalanine pathways. Investigations demonstrated that glucose, cresol, capsaicin, and vanillyl alcohol pathway were detected in a wide range of distribution in microbial metabolism. Thus, microorganisms might have participated in vanillin biosynthesis during vanilla curing. Furthermore, the ion strength of glucovanillin was stable, which indicated that glucovanillin only participated in the vanillin biosynthesis during the curing of vanilla.
Applied and Environmental Microbiology | 2015
Yonggan Chen; Fenglin Gu; Jihua Li; Shuzhen He; Fei Xu; Yiming Fang
ABSTRACT 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.
Molecules | 2018
Fenglin Gu; Feifei Huang; Guiping Wu; Hongying Zhu
Black pepper (Piper nigrum L.) is the most widely used spice in the world. Blackening is considered to be beneficial and important in the processing of black pepper because it contributes to its color and flavor. The purpose of this paper is to investigate polyphenol oxidation as well as the chlorophyll and vitamin C (VC) degradation in the blackening of Piper nigrum L. Black pepper was produced by four methods, and changes in polyphenols, chlorophyll and VC were studied by high performance liquid chromatography (HPLC) and ultraviolet-visible and visible (UV-Vis) spectrophotometry. The results show that polyphenol oxidase activity significantly decreased during the preparation of black pepper, and the concentrations of phenolic compounds, VC, and chlorophyll a and b also significantly decreased. Polyphenol oxidation and chlorophyll and VC degradation contribute to the blackening. A crude extract of phenolic compounds from black pepper was prepared by the system solvent method. The greater the polarity of the extraction solvent, the higher the extraction rates of the phenolic compounds and the total phenol content. Pepper phenolic compounds were analyzed by HPLC analysis.
Molecules | 2015
Fenglin Gu; Yonggan Chen; Yiming Fang; Guiping Wu; Lehe Tan
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.
Molecules | 2018
Fenglin Gu; Guiping Wu; Yiming Fang; Hongying Zhu
In the present study, nontargeted metabolomics was used to screen the phenolic and polyhydroxy compounds in pepper products. A total of 186 phenolic and polyhydroxy compounds, including anthocyanins, proanthocyanidins, catechin derivatives, flavanones, flavones, flavonols, isoflavones and 3-O-p-coumaroyl quinic acid O-hexoside, quinic acid (polyhydroxy compounds), etc. For the selected 50 types of phenolic compound, except malvidin 3,5-diglucoside (malvin), l-epicatechin and 4′-hydroxy-5,7-dimethoxyflavanone, other compound contents were present in high contents in freeze-dried pepper berries, and pinocembrin was relatively abundant in two kinds of pepper products. The score plots of principal component analysis indicated that the pepper samples can be classified into four groups on the basis of the type pepper processing. This study provided a comprehensive profile of the phenolic and polyhydroxy compounds of different pepper products and partly clarified the factors responsible for different metabolite profiles in ongoing studies and the changes of phenolic compounds for the browning mechanism of black pepper.
Archive | 2012
Fenglin Gu; Qinghuang Wang; Shaofang Lu; Zhong Chu; Huasong Wu; Lehe Tan; Wanlan Ji