Jicheng Zhan

Effect of initial ph on growth characteristics and fermentation properties of Saccharomyces cerevisiae.

As the core microorganism of wine making, Saccharomyces cerevisiae encounter low pH stress at the beginning of fermentation. Effect of initial pH (4.50, 3.00, 2.75, 2.50) on growth and fermentation performance of 3 S. cerevisiae strains Freddo, BH8, Nº.7303, different tolerance at low pH, chosen from 12 strains, was studied. The values of yeast growth (OD600 , colony forming units, cell dry weight), fermentation efficiency (accumulated mass loss, change of total sugar concentration), and fermentation products (ethanol, glycerol, acetic acid, and l-succinic acid) at different pH stress were measured. The results showed that the initial pH of must was a vital factor influencing yeast growth and alcoholic fermentation. Among the 3 strains, strain Freddo and BH8 were more tolerant than Nº.7303, so they were affected slighter than the latter. Among the 4 pH values, all the 3 strains showed adaptation even at pH 2.50; pH 2.75 and 2.50 had more vital effect on yeast growth and fermentation products in contrast with pH 4.50 and 3.00. In general, low initial pH showed the properties of prolonging yeast lag phase, affecting accumulated mass loss, changing the consumption rate of total sugar, increasing final content of acetic acid and glycerol, and decreasing final content of ethanol and l- succinic acid, except some special cases. Based on this study, the effect of low pH on wine products would be better understood and the tolerance mechanism of low pH of S. cerevisiae could be better explored in future.

Copper Tolerance and Biosorption of Saccharomyces cerevisiae during Alcoholic Fermentation

At high levels, copper in grape mash can inhibit yeast activity and cause stuck fermentations. Wine yeast has limited tolerance of copper and can reduce copper levels in wine during fermentation. This study aimed to understand copper tolerance of wine yeast and establish the mechanism by which yeast decreases copper in the must during fermentation. Three strains of Saccharomyces cerevisiae (lab selected strain BH8 and industrial strains AWRI R2 and Freddo) and a simple model fermentation system containing 0 to 1.50 mM Cu2+ were used. ICP-AES determined Cu ion concentration in the must decreasing differently by strains and initial copper levels during fermentation. Fermentation performance was heavily inhibited under copper stress, paralleled a decrease in viable cell numbers. Strain BH8 showed higher copper-tolerance than strain AWRI R2 and higher adsorption than Freddo. Yeast cell surface depression and intracellular structure deformation after copper treatment were observed by scanning electron microscopy and transmission electron microscopy; electronic differential system detected higher surface Cu and no intracellular Cu on 1.50 mM copper treated yeast cells. It is most probably that surface adsorption dominated the biosorption process of Cu2+ for strain BH8, with saturation being accomplished in 24 h. This study demonstrated that Saccharomyces cerevisiae strain BH8 has good tolerance and adsorption of Cu, and reduces Cu2+ concentrations during fermentation in simple model system mainly through surface adsorption. The results indicate that the strain selected from China’s stress-tolerant wine grape is copper tolerant and can reduce copper in must when fermenting in a copper rich simple model system, and provided information for studies on mechanisms of heavy metal stress.

Influence of technical processing units on chemical composition and antimicrobial activity of carrot (Daucus carrot L.) juice essential oil

The effect of three processing units (blanching, enzyme liquefaction, pasteurisation) on chemical composition and antimicrobial activity of carrot juice essential oil was investigated in this paper. A total of 36 compounds were identified by GC-MS from fresh carrot juice essential oil. The main constituents were carotol (20.20%), sabinene (12.80%), β-caryophyllene (8.04%) and α-pinene (6.05%). Compared with the oil of fresh juice, blanching and pasteurisation could significantly decrease the components of the juice essential oil, whereas enzyme liquefaction had no considerable effect on the composition of juice essential oil. With regard to the antimicrobial activity, carrot juice essential oil could cause physical damage and morphological alteration on microorganisms, while the three different processing units showed noticeable differences on the species of microorganisms, the minimum inhibitory concentration and minimum bactericidal concentration. Results revealed that the carrot juice essential oil has great potential for application as a natural antimicrobial applied in pharmaceutical and food industries.

Changes in Salicylic and Abscisic Acid Contents during Heat Treatment and Their Effect on Thermotolerance of Grape Plants

Heat treatment (38°C) of young grape plants (Vitis vinifera L., cv. Jingxiu) or leaf spraying with 100 µM salicylic acid (SA) increased leaf thermotolerance. Both treatments led to an increase in ABA content and a decrease in lipoxygenase (LOX) activity. ABA content showed a drastic rise by one hour after treatments and then sharply declined while LOX activity continuously decreased. In the course of heat treatment of grape plants, endogenous SA level and phenylalanine ammonia-lyase activity rapidly increased during the first hour, then declined. These results showed that endogenous SA and ABA can be involved in grape plant response to heat treatment resulted in improved thermotolerance.

Polysaccharide extraction from Sphallerocarpus gracilis roots by response surface methodology

The extraction process of Sphallerocarpus gracilis root polysaccharides (SGRP) was optimized using response surface methodology with two methods [hot-water extraction (HWE) and ultrasonic-assisted extraction (UAE)]. The antioxidant activities of SGRP were determined, and the structural features of the untreated materials (HWE residue and UAE residue) and the extracted polysaccharides were compared by scanning electron microscopy. Results showed that the optimal UAE conditions were extraction temperature of 81°C, extraction time of 1.7h, liquid-solid ratio of 17ml/g, ultrasonic power of 300W and three extraction cycles. The optimal HWE conditions were 93°C extraction temperature, 3.6h extraction time, 21ml/g liquid-solid ratio and three extraction cycles. UAE offered a higher extraction yield with a shorter time, lower temperature and a lower solvent consumption compared with HWE, and the extracted polysaccharides possessed a higher antioxidant capacity. Therefore, UAE could be used as an alternative to conventional HWE for SGRP extraction.

Effect of Cultivar, Temperature, and Environmental Conditions on the Dynamic Change of Melatonin in Mulberry Fruit Development and Wine Fermentation

High levels of melatonin have been reported in various foods but not in mulberry or its wine. This study investigated the dynamic changes of melatonin levels during mulberry fruit development and ethanol fermentation of 2 different colored mulberry cultivars (Hongguo2ˮ Morus nigra, black and Baiyuwangˮ Morus alba, white) at 2 fermentation temperatures (16 and 25 °C). Our results showed that the melatonin level increased in the beginning of mulberry development but decreased in the end. The MnTDC gene expression level correlated with melatonin production, which implied that TDC may be the rate-limiting enzyme of the melatonin biosynthetic process in mulberries. During mulberry fermentation, the melatonin concentration increased rapidly in the beginning and then decreased gradually. Low temperature delayed the melatonin production during fermentation. A relatively high level of melatonin was found in Hongguo2ˮ compared with Baiyuwangˮ during fruit development and fermentation. The variation of melatonin correlated with the ethanol production rate, suggesting that melatonin may participate in physiological regulation of Saccharomyces cerevisiae during the fermentation stage.

Profiles of Phenolic Acids and Flavan-3-ols for Select Chinese Red Wines: A Comparison and Differentiation According to Geographic Origin and Grape Variety

UNLABELLEDnThe profiles of phenolic acids and flavan-3-ols for the selected Chinese red wines and the potential of using phenolic acids and flavan-3-ols to differentiate the geographic origin and grape variety of wines from China are investigated in this study. Significant differences and markers could be found according to the geographical origin and grape variety. Through a canonical discriminant analysis a good differentiation was developed according to the geographic origin or grape variety, and the accuracy of the discriminant model was 88.9% and 100%, respectively. According to the phenolic acid and flavan-3-ols profiles of the wine samples and good differentiation in the region and the variety discriminant analysis, minimal fraudulent claims were noted for the Chinese red wines investigated.nnnPRACTICAL APPLICATIONnThis study provides some help for the protection of geographical origin and monovarietal wine claims.

Effects of Copper Pollution on the Phenolic Compound Content, Color, and Antioxidant Activity of Wine

The effects of copper pollution on the polyphenol content, color, and antioxidant activity of wine, as well as correlations among these factors, were investigated. Copper had clear influences on wine polyphenol content. At low copper concentrations, the concentrations of nearly all polyphenols increased, and the antioxidant activity values of the wine also increased. When the copper concentration reached the lowest level of the medium copper range (9.6~16 mg/L), most of the indices also improved. When the copper concentrations reached the latter part of the medium copper range (19.2 and 22.4 mg/L), many of the tested indices began to decrease. Furthermore, when the copper concentration reached the high ranges (32, 64, and 96 mg/L), the polyphenol content, CIELAB color parameters, and antioxidant activity of wine were substantially decreased, indicating the need to control increasing copper content in grape must.

Detection method optimization, content analysis and stability exploration of natamycin in wine.

A new detection method of natamycin via HPLC-MS/MS was developed that uses an Agilent 6460 HPLC-MS/MS instrument and an Agilent RP18 (2.1mm×50mm, 1.8μm); the LOD was 1μg/L, the LOQ was 3.34μg/L, the recovery was 70-94%, the RSD was approximately 2-4%, and the total run time was 5min. In the new detection method of natamycin via HPLC-MS/MS, processing of the sample before detection is necessary, which can be performed using solid phase extraction. Surprisingly, natamycin was not detected in any the sampled retail commercial wines from the Chinese market. Natamycin is very unstable in wine because many process steps, including the malo-lactic fermentation, clarification and storage, could result in degradation of natamycin. Regarding the clarifying agents, bentonite exhibited the strongest effect on natamycin. During the storage period, natamycin is very sensitive to light.

Enrichment and Purification of Polyphenol Extract from Sphallerocarpus gracilis Stems and Leaves and in Vitro Evaluation of DNA Damage-Protective Activity and Inhibitory Effects of α-Amylase and α-Glucosidase

An efficient preparative separation method for Sphallerocarpus gracilis stems and leaves polyphenols (SGslP) was established in this study. An X-5 macroporous adsorption resin was selected for the purification of the SGslP, and the polyphenol content of the purified SGslP (PSGslP) was increased 5.11-fold from 8.29% to 42.38% after one treatment run. The chemical composition of the PSGslP was analyzed by HPLC-MS/MS, and the predominant compounds were found to be luteolin-7-glucoside, acacetin-7-acetyglycoside and its isomers. In addition, the PSGslP was evaluated in vitro to determine the DNA damage-protective activity and inhibitory effects of α-amylase and α-glucosidase. The results indicated that the PSGslP exhibited significant protective activities against both ROO• and •OH radical-induced DNA damage. Moreover, the PSGslP exerted a dose-dependent inhibition effect on α-glucosidase but no inhibitory effect on α-amylase. These findings indicate that the Sphallerocarpus gracilis stems and leaves are good natural sources of antioxidants and are potent inhibitors of α-glucosidase activity and are potential anti-diabetic inhibitor.