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The influence of keeving on the quality parameters of fermented apple beverages
Tomasz Tarko1, Aleksandra Duda-Chodak1, Magdalena Januszek1,
Paweł Sroka1,Małgorzata Siuta1
1 University of Agriculture in Krakow, Department of Fermentation Technology and Technical Microbiology, Krakow, Poland
Keeving is a process not commonly used in the production of alcoholic beverages. The process consists in removing from the apple juice the nutrients, among others amino acids,by binding them with pectins. As a result of the method, fermentation occurs slower and stops spontaneously.The purpose of the experiments was to assess the impact of keeving on the basic quality parameters of fermented apple beverages.The musts used for the experiments were made of the Rubin apple cultivar. Pectinesterase (Univar, Poland) was added to the ground apples and left for 24 hours to separate the juice and pectin. The must was pressed (Zottel hydropress), which was then poured into fermentation containers and CaCl2 was added in three concentrations (0.1, 0.2 and 0.4 g/l). Must was inoculated with various yeast strains: wine (Elegance), cider (Gozdawa), distillery (RED Ethanol) or wild (Wild & Pure). The process of fermentation was carried out for 30 days at 20°C, during which time a brown cap (chapeau brun) was collected and fermentation continued. A fermented must not to be subjected to keeving was a control. The ethanol concentration, extract content, total and volatile acidity as well as the content of free amino nitrogen (FAN) were determined in beverages using the methods described byOIV.The significant influence of keeving and various yeast strains on the quality parameters of fermented beverages has been demonstrated. The use of keeving caused that the ethanol content in beverages was lower, leaving more unfermented extract. Keeving caused also that the volatile acidity of drinks was approximately 2-fold higher, while the total acidy slightly lower. A much lower content of FAN was also observed. The highest attenuation was observed after the use of distillery yeast, and the beverages obtained with their participation were characterized by low volatile and total acidity.
Keywords — fermented applebeverages, keeving, wine quality parameters
