Maria Kanellaki

High-temperature alcoholic fermentation of whey using Kluyveromyces marxianus IMB3 yeast immobilized on delignified cellulosic material.

A novel system for high-temperature alcoholic fermentation of whey is described. This system consists of Kluyveromyces marxianus yeast immobilized on delignified cellulosic material (DCM). The effect of pH, initial lactose concentration and temperature on the fermentation of a synthetic medium containing lactose was studied. Batch fermentations of whey were also carried out and the formation of volatile by-products was examined. The concentrations of higher alcohols were found to be in very low levels leading to a product of improved quality. The fermented whey had an improved characteristic aroma compared to unfermented whey. The possibility to use fermented whey as raw material for the production of a novel, low alcohol content drink was also investigated.

Wine fermentations by immobilized and free cells at different temperatures. Effect of immobilization and temperature on volatile by-products

A biocatalyst was prepared by immobilization of Saccharomyces cerevisiae, strain AXAZ-1, on delignified cellulosic material (DCM) and gluten pellets (GP). Repeated batch fermentations were conducted using these biocatalysts and free cells, separately, at different temperatures. The volatile constituents were extracted with dichloromethane and the extracts were subsequently analyzed by HRGC/MS. Wines produced by DCM contained higher amounts of esters, at every temperature studied, whereas those produced by GP biocatalyst contained higher amounts of alcohols. Free cells and DCM biocatalyst gave wines with similar contents of alcohols. Wines produced by DCM biocatalyst gave better ratios of esters to alcohols and had dominating fruity aromas. GC/MS analysis proved that cell immobilization did not create serious changes in qualitative composition of the wine aroma. As regards the quantitative profile, the combined effect of temperature and immobilization resulted in the production of wines with more fruity character because of the higher ratio of esters to alcohols.

Room temperature and low temperature wine making using yeast immobilized on gluten pellets

Abstract A cryotolerant and alcohol tolerant strain of Saccharomyces cerevisiae was immobilized on gluten pellets and examined by electron microscopy. The biocatalyst was used for repeated batch fermentations in glucose and must for wine making at 30, 15, 10, 5 and 0°C, without any loss of activity. This biocatalyst produced at least a three-fold increase in the fermentation rate when compared with free cells and reduced the activation energy, E a . Wine and ethanol productivities obtained at 15°C were about half those obtained at 30°C. At 10°C the average wine productivity was about 30% of that obtained at 30°C. For each temperature, ethanol and wine productivities for immobilized cells were higher than those for free cells and the improvement increased as the temperature was decreased. At temperatures lower than 10°C, wine productivities were four to seven times higher than those of the free cells.

Influence of polysaccharide addition on stability of a cheese whey kefir-milk mixture

Abstract A kefir-type drink was prepared by fermentation with kefir granules of cheese whey containing fructose and black raisin extract. Milk (20%) was then added to improve its rheological and sensory properties and in order to prevent casein coagulation and sedimentation in the acid environment of the mixture, a number of polysaccharides were evaluated as stabilizers. Xanthan appears to be more effective at relatively low concentration levels (0.2%) compared to guar gum while high methoxyl pectin, a well-known acid milk drink stabilizer was less effective in this respect even at concentrations as high as 1%. Particle size and rheology measurements pointed out to the importance of the weak gel properties of xanthan solution in stabilizing the system against ‘wheying off’ while other stabilization mechanisms such as particle network formation as a result of depletion flocculation in the case of guar gum or pectin adsorption at the casein particle surface resulting in steric stabilization appear to be less dominant.

Continuous Wine Making by γ-Alumina-Supported Biocatalyst

The main objective of the present work was the removal of aluminum from wines produced by γ-alumina-supported yeast cells. Reagents such as Na2CO3, NH4OH, albumin, and Ca(OH)2 were used. Calcium in the presence of albumin was effective, whereas other reagents were not so effective. Because of the improved aroma and taste of distillates produced by γ-alumina-supported biocatalyst, volatile byproducts of distillates were analyzed. They were also assessed by sensory tests. Methanol, acetaldehyde, ethyl acetate, propanol-1, isobutyl alcohol, and amyl alcohols were determined in distillates. It was noted that the amounts of higher alcohols and amyl alcohols decreased as the temperature of fermentation dropped, leading to a product of improved quality and reduced toxicity.

Functional properties of single cell protein produced by kefir microflora

Single cell protein (SCP) was produced by aerobic fermentation of cheese whey by kefir microorganisms. A feed-batch system was developed on a bioreactor of 4 1. The experiments were conducted under controlled pH (5.5) and temperature (30 °C) conditions. The biomass was analyzed for protein, lipids, carbohydrates and ash and its functional properties (emulsification, foaming, gelation) were studied. Single cell protein (53.9% protein) exhibited emulsifying properties similar to those of defatted soy flour, while its Ibaming activity and foam liquid stability were much higher. Finally, texture profile analysis of gels, formed by heating water dispersions of SCP, showed that the structures produced were stronger compared with those of gels made with soy flour.

Wine production using yeast immobilized on quince biocatalyst at temperatures between 30 and 0 °C

A biocatalyst was prepared by immobilization of Saccharomyces cerevisiae, strain AXAZ-1, yeast cells on quince pieces and its suitability for fermentation of glucose and grape must was investigated. The immobilized yeast showed operational stability and no decrease in activity, even at low temperatures (0-10 degreesC). Total and volatile acidities in the wines produced were similar to dry wines. The concentrations of higher alcohols (propan-1nol and isobutyl alcohol) were low. The production of amyl alcohols proved to be temperature-dependent and decreased with lower temperatures. Ethyl acetate concentrations were relatively high, up to 113 mg/l. This probably contributes to the fruity aroma and high quality taste of the wines. GGMS analysis of wines produced using the immobilized biocatalyst and free cell fermentations showed no significant differences in the qualitative composition of aroma-related constituents

Grape skins as a natural support for yeast immobilization

Grape skins were used to immobilize Saccharomyces cerevisiae. In repeated batch fermentations of grape by immobilized and free cells, the maximum specific rate of alcohol production on glucose decreased from 7.98 h−1 at 25 °C to 0.7 h−1 at 5 °C. The rate was approximately twice as high as that on fructose. The rates for free cells were very low. The maximum alcohol yield (0.45 g g−1) was obtained at 5 °C when the immobilized biocatalyst was used.

Volatile by-products formed in low-temperature wine-making using immobilized yeast cells

Abstract The formation of acetaldehyde, ethyl acetate, propanol-1, isobutanol, amyl alcohols and methanol in repeated batch and continuous fermentations of must using a cryotolerant and alcohol-resistant yeast immobilized on delignified cellulosic material (DCM) and gluten pellets was studied. The fine and fruity aroma of the wines prepared may be attributed to the high content of ethyl acetate in the total volatiles. Immobilization of yeast cells increased ethyl acetate production and, in the case of the DCM, decreased amyl alcohol production at low temperatures compared with free cells. With the DCM-supported biocatalyst, the percentage ethyl acetate of total volatiles minus methanol remained constant as the temperature was reduced, while the amyl alcohol content was reduced. Amyl alcohols are thought to be correlated with improvement of the aroma and the decrease in toxicity of the wine.

Ethanol Production by Saccharomyces cerevisiae Immobilized on Mineral Kissiris

Abstract The attachment of Saccharomyces cerevisiae cells on the cheap and abundant ore Kissiris was investigated. Attached cells produced about 115 g/ l /d ethanol when inoculated in media containing glucose and 96 g/ l /d ethanol in raisin extract. No reduction in ethanol productivity and yield was observed for up to 29 repeated batch fermentations.