Wine Fermentation Process Research Articles

Amperometric biosensor for lactate analysis in wine and must during fermentation

A lactate oxidase-based amperometric biosensor is designed for lactate determination. Two methods of lactate oxidase immobilization on the surface of commercial SensLab platinum printing electrodes are compared. The sensor with lactate oxidase immobilized by physical adsorption in Resydrol polymer is shown to have both narrower dynamic range (0.004–0.5 mМ lactate) and higher sensitivity (320 nA/mM) as compared with that immobilized in poly(3,4-ethylenedioxythiophene) by electrochemical polymerization (0.05–1.6 mM and 60 nA/mM respectively). The operational stability of the biosensors developed is studied; the immobilization method is shown to be of no influence. The lactate content in wine and in wine material during fermentation is analyzed. The data obtained by amperometric lactate biosensor correlated with those of standard chromatography. The biosensor developed can be used in food industry for control and optimization of process of wine fermentation as well as for control of wine quality.

Effects of temperature, ammonium and glucose concentrations on yeast growth in a model wine system

SummaryIn enology, alcoholic fermentation is a complex process involving several mechanisms. Slow and incomplete alcoholic fermentation is a chronic problem for the wine industry and factors leading to sluggish and stuck fermentations have been extensively studied and reviewed. The most studied cause of sluggish and stuck fermentation is the nitrogen content limitation. Nevertheless, other factors, such as temperature of fermentation and sugar concentration can affect the growth of yeasts. In this study we modelled the yeast growth‐cycle in wine model system as a function of temperature, sugar and ammonium concentrations; the individual effects and the interaction of these factors were analysed by means of a quadratic response surface methodology. Cell concentrations and weight loss were monitored in the whole wine fermentation process. The results of central composite design show that lower is the availability of nitrogen, higher is the cell growth rate; moreover, initial nitrogen concentration also influences survival time of Saccharomyces cerevisiae.

Characterization of a flocculation-like phenotype in Cryptococcus neoformans and its effects on pathogenesis

We investigated the phenomenon of cell-cell aggregation (flocculation) in a serotype D strain of Cryptococcus neoformans (ATCC 24067, isolate RC-2). Cell aggregation into clumps of 5-40 cells (clump+ cells) occurred during the early log phase and disappeared in the beginning of the stationary phase (clump- cells). The cell aggregation phenomenon was medium dependent. Clump+ cells could be dispersed by either vortexing or proteinase K digestion. Most importantly, the transient change in cellular phenotype changed several important host-pathogen interactions. Adherence of clump+ cells to murine macrophage-like cells J774.16 was significantly (P < 0.001) enhanced compared with adherence of clump- cells. Furthermore, complement-mediated phagocytosis efficacy of dispersed clump+ cells was significantly higher (P < 0.001) compared with clump- cells. Similar findings were documented with an in vivo phagocytosis assay. Infection of mice with a low inoculum (10(4)) of clump+ cells resulted in lower fungal burden when compared with mice infected with clump- cells. Accordingly, mice infected with clump+ cells survived significantly longer than mice infected with clump- cells. These results indicate that the cellular phenotype undergoes significant changes that result in a transient flocculation-like phenotype. We hypothesize that this cell-cell aggregation is the result of changes in protein content in the polysaccharide capsule. We conclude from our data that the change in cellular phenotype has a dramatic effect on cell adherence, and on complement-mediated phagocytosis, both of which can affect the pathogenesis of the disease in the host. Our results underscore the complexity of studies that investigate host pathogen interactions and may explain differences and inconsistencies observed in in vitro and in vivo assays.

Utilisation of first principal component extracted from gas sensor measurements as a process control variable in wine fermentation

Tokaj wine fermentation process was followed with complex off-line measurements using traditional instrumental methods, human sensory assessment and gas sensor headspace measurements. The first principal component (PC1) extracted from gas sensor responses was proposed as a process control variable. The chemical interpretation of PC1 was proposed. Based on multiple linear regression model, the PC1 was well explained with the alcohol content, organic acids and ethyl acetate concentration in fermenting medium. These compounds indicate the progress of fermentation process as well as the sensory quality of final wine. Additionally, the PC1 very well correlated with human sensory assessment of the intensity of odour and flavour of fermenting medium. Therefore, the potential of gas sensor array to provide an alternative to human operator control of wine fermentation control was indicated.

Red clover isoflavonoids as anthocyanin color enhancing agents in muscadine wine and juice

Isoflavonoid extracts from red clover ( Trifolium pratense) leaves were found to enhance overall color and stability of anthocyanin 3,5-diglucosides present in muscadine grape ( Vitis rotundifolia) juice and wine through intermolecular copigmentation reactions. Predominant isoflavonoids present in red clover included formononetin, biochanin A, and prunetin and were the major polyphenolics identified to influence anthocyanin color and stability. Since red clover isoflavonoids have poor water solubility characteristics, this allowed for removal of extraneous non-isoflavonoid compounds using hot water and subsequent extraction with ethanol. Isoflavonoid solubility was evaluated as a function of ethanol concentration with recoveries up to 57% found in 20% solutions. Changes in maximum absorbance, total soluble phenolics, isoflavonoids, and anthocyanins were evaluated in muscadine juice and wine following the addition of isoflavonoid extracts with maximum color enhancement found at an anthocyanin to cofactor ratio of 1:8, after which their solubility was prohibitive. Additionally, dried leaves and ethanolic extracts of red clover were added prior to and following fermentation of muscadine wine (11% ethanol) stimulating the natural copigmentation that takes place during red wine fermentation and aging processes. Once fermentation was complete, finished wines were evaluated over a 9-week storage period at 20 and 37 °C. Despite low levels of isoflavonoids present, color improvement and anthocyanin stability was observed in the wines during storage. Little information is available on copigmentation reactions occurring in actual food systems, yet red clover isoflavonoids proved to be novel and effective color enhancing compounds when used in low concentrations in young muscadine wines.

Quinohemoprotein alcohol dehydrogenase-based reagentless amperometric biosensor for ethanol monitoring during wine fermentation

This paper describes the development and optimization of an amperometric biosensor for monitoring ethanol in beverages. The biosensor is constructed by cross-linking a quinoprotein alcohol dehydrogenase (QH-ADH) to an Os-complex-modified poly(vinylimidazole) redox polymer using poly(ethylene glycol) diglycidyl ether. The optimum biosensor configuration was evaluated by changing the ratio between enzyme, redox polymer, and cross-linker using conventional graphite rods as basis electrodes. The optimized sensor showed a sensitivity of 0.336±0.025 A M −1 cm 2 for ethanol and a detection limit (calculated as three times the signal-to-noise ratio) of 1 μM. This biosensor configuration was further evaluated in a conventional flow-injection system and the applicability for the determination of ethanol in diverse wine samples could be successfully demonstrated. Adaptation of this sensor configuration to screen-printed (SP) electrodes allowed their integration into an automated sequential-injection analyzer and the successful on-line monitoring of ethanol during wine fermentation processes.

Process control of apple winemaking by low-resolution gas-phase Fourier-transform infrared spectroscopy.

Four apple wine fermentation processes have been observed by means of direct-inlet gas-phase FTIR spectroscopy. The apple juice concentrates were each fermented by two species of Saccharomyces cerevisiae starters, and the experiment was repeated. The development of the concentrations of 1-propanol, 4-methylpyridine, acetaldehyde, acetic acid, and ethyl acetate was monitored. Two different sampling methods were used--static headspace and direct injection of the must. The performance of the FTIR method is limited by the high ethanol concentration. It can be mathematically proven that the amount of sample can be selected so that any distortion due to ethanol is minimized. Headspace GC-MS was used for preliminary compound identification.

A new fuzzy control system for white wine fermentation

This paper presents a new control strategy for the wine fermentation process based on fermentation rate control. A kinetic model of white wine fermentation has been constructed with the objective of testing the control procedure. The model only depends on very few quality parameters of the original must and can be executed in real-time, thus it can be used in real-time model-based control. A control methodology based on fermentation rate has therefore been developed, and a fuzzy multivariable controller was implemented. Further studies using different values for fermentation rate are discussed.

Examination of aroma production kinetics of different commercial wine yeasts in fermenting muscat ottonel wines with the help of spme head-space sampling and fast gc analysis

Solid phase microextraction (SPME) coupled to fast capillary gas chromatography was used for monitoring the wine fermentation process. This combination offers a simple, quick and sensitive approach suitable for characterization of head-space components of wines during the fermentation process without a complicated sample preparation procedure. In this work this method was used to observe the differences in aroma production between three different commercial yeasts and the indigenous yeast flora.

Monitoring ethanol production during wine fermentation processes by a pervaporation–enzymic derivatisation approach

A new procedure for on-line monitoring of ethanol production in the wine fermentation bioprocess is presented. The method combines the use of a pervaporation unit inserted in a continuous flow system with the use of enzymic derivatisation and fluorimetric detection as a way of improving both selectivity and sensitivity. The derivatisation reaction was based on a two-step reaction involving alcohol oxidase (AOD) and horseradish peroxidase (POD) with fluorimetric detection at λex = 310 nm and λem = 415 nm of the dimer formed. The efficiency of the derivatisation reaction was tested using different flow injection approaches with either solution phase or immobilised biocatalysts (in normal or stopped-flow modes in both cases). Finally, the approach based on the stopped-flow mode and AOD/POD immobilisation was selected for application to the continuous monitoring of ethanol production in an experimental laboratory built bioreactor prepared using baker’s yeast as active cells. The method shows different linear ranges depending on the situation of the catalyst and the mode used, with excellent precision (RSD 3.0–5.5%) and a sampling frequency of 5 h–1. The use of this biosensing system was also tested by the standard addition method in the fermentation product with acceptable recoveries in all instances (90–105%). A fully automated approach to on-line bioprocess sample collection, dilution and monitoring of the fluorimetric product is also proposed.

Stationary-phase gene expression in Saccharomyces cerevisiae during wine fermentation.

Genetic engineering of wine yeast strains requires the identification of gene promoters specifically activated under wine processing conditions. In this study, transcriptional activation of specific genes was followed during the time course of wine fermentation by quantifying mRNA levels in a haploid wine strain of Saccharomyces cerevisiae grown on synthetic or natural winery musts. Northern analyses were performed using radioactive probes from 19 genes previously described as being expressed under laboratory growth conditions or on molasses in S. cerevisiae during the stationary phase and/or under nitrogen starvation. Nine genes, including members of the HSP family, showed a transition-phase induction profile. For three of them, mRNA transcripts could be detected until the end of the fermentation. Expression of one of these genes, HSP30, was further studied using a HSP30::lacZ fusion on both multicopy and monocopy expression vectors. The production of beta-galactosidase by recombinant cells was measured during cell growth and fermentation on synthetic and natural winery musts. We showed that the HSP30 promoter can induce high gene expression during late stationary phase and remains active until the end of the wine fermentation process. Similar expression profiles were obtained on five natural winery musts.

Scopolamine Poisoning From Homemade ‘Moon Flower’ Wine

LH, a 76-year-old Caucasian male, ingested 3 teaspoons (15 mL) of a homemade wine over a 1-h period and became ill. Approximately 1.5 h later, he was taken to the emergency room of a local hospital with symptoms of respiratory distress and weakness. The plant used in making the wine was Angel's trumpet (Datura suaveolens), which reportedly contains varying amounts of scopolamine and atropine. A sample of the wine was collected and analyzed for these two compounds by reversed-phase HPLC chromatography using 97% methanol-3% deionized water. The filtered wine contained an estimated 29 mg scopolamine/mL, which produced a total ingested dose of 435 mg. No atropine was detected. The scopolamine was confirmed by TLC. An oral dose of 50 mg of atropine sulfate in humans has been reported fatal, but there is no reported fatal dose for scopolamine. The alcohol content and 3.8 pH of the homemade wine may have increased the extraction of this compound from the plant material, and the wine fermentation process may have concentrated the original extract.

Determination of glucose in fermentation processes by means of an on-line coupled flow-injection system using enzyme sensors based on chemically modified electrodes

The application of an inexpensive, easy-to-make and disposable biosensor, based on a chemically modified graphite electrode with an adsorbed and cross-linked layer of glucose dehydrogenase, as a detector in a flow-injection system for on-line monitoring of glucose in fermenters is described. The performance of the sensor as a function of time is investigated, and used for assaying glucose in a wine fermentation process. It is concluded that the sensor operates satisfactorily during at least 3 days of continuous use. No interference from ethanol is encountered. With regard to practical applications, special emphasis is placed on the interfacing of the fermenter and the analytical system.

Development of continuous fermentation using immobilized yeast cells for wine cooler process development

The continuous wine fermentation process, which employs a newly designed tapered column type bioreactor and immobilized yeast cells (Montrachet 522), was studied and its fermentation performance was compared with batch and suspended cell continuous wine fermentation systems.

Effect of Alcoholic Fermentation on Arsenic Species Content

The analysis and speciation of arsenic in must and wine samples was carried out with an ion exchange column combined with hydride-generation atomic spectrometry. The changes in the chemical species of arsenic that occur during the wine fermentation process were examined.