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Effect of nitrogen sources on fermentation process and formation of hydrogen sulfide and ethyl carbamate by wine yeast
(Wydawnictwo Politechniki Łódzkiej, 2013) Nowak, Agnieszka; Koch-Wilk, Magdalena; Pogorzelski, Eugeniusz; Czyżowska, Agata
The addition of nitrogen compounds during winemaking is required for the fermentation process to be conducted properly. These compounds are known to be essential to the vinification process, not only because they influence yeast growth but also because they affect the formation of main and by-products. The effect of nitrogen source on in vitro and in situ formation of hydrogen sulfide and ethyl carbamate was studied. Research material comprised two strains of wine yeast: Saccharomyces cerevisiae. In vitro model was carried out in a synthetic defined medium. In situ fermentations were carried out in musts prepared from apple concentration. The process of hydrogen sulfide formation was intensified in nitrogen deficiency. The presence of amino acids in a model substrate resulted in significant changes in the efficiency of formation of both compounds. Yeasts produced more H2S in the presence of Cys, Phe, Gly, Glu, Ile, Thr, Pro, Leu, Trp, Val and less in the presence Ala, Arg, Asp, His, Ser, Met. The formation of ethyl carbamate was limited by the amino acids, except Arg, Asp and Lys, which during fermentation with Syrena yeasts caused an increase in the efficiency of formation of this compound. The Fermivit V preparation stimulated yeasts to form H2S. In the presence of this preparation the Syrena yeasts formed more ethyl carbamate while Hefix yeasts formed about 3-fold less of this compound then in the presence diamonium phosphate.
Enzymatic liquefaction of apple pomace
(Wydawnictwo Politechniki Łódzkiej, 2010) Piątka, Dorota; Wilkowska, Agnieszka; Pogorzelski, Eugeniusz
Clarity is one of the most important quality criteria required in apple juices and wines. Haze formation during apple processing can be caused by homogalacturonan, rhamnogalacturonan, arabinogalactan, arabinan or xylogalacturonan. Manufacturers are looking for new technologies that guarantee high quality, decrease production costs and solve most technological problems. Nowadays production of apple juices is strongly connected with enzymes technology. Using pomace liquefaction with different pectinases and celluloses improves the yield of the apple juice, but on the other hand results in an increase in turbidity. Hence, inappropriate usage of enzymes can lead to filtration problems. Apple pomace liquefaction process need to be optimized. In this review, different methods of haze reduction was discussed.
Wpływ procesu technologicznego na stężenia związków mineralnych w soku i koncentracie jabłkowym
(Wydawnictwo Politechniki Łódzkiej, 2006) Lubecka, Izabela; Pogorzelski, Eugeniusz
Przedmiotem analiz były próby soku jabłkowego: bezpośrednio po tłoczeniu, po procesie depektynizacji, po klarowaniu, ultrafiltracji i zagęszczaniu. Na podstawie przeprowadzonych badań oraz oceny wyników można stwierdzić, że zawartość substancji mineralnych zmienia się w trakcie całego procesu technologicznego. Wykazano, że zarówno rodzaj użytego preparatu enzymatycznego podczas procesu depektynizacji, jak i ilość środka klarującego, ma wpływ na skład popiołu soku jabłkowego. Zastosowanie procesu ultrafiltracji spowodowało zatrzymanie badanych pierwiastków, w tym jonów wapnia, przez membrany filtracyjne i obniżenie ich zawartości w finalnym produkcie.