Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
The possibility of fast determination of alcohol and total dry extract from given relative density and refractive index in wine was examined on fifty eight samples of Slovenian white and red still wines. Calculated relation values obtained from literature were compared to values determined experimentally using official methods (pycnometry and hydrostatic balance). Determination of alcohol and total dry extract together by means of calculation was the most accurate for the group of white wines (according to the concentration of reducing sugars) with up to 5 g L–1 and the least accurate for the group of white wines with over 15 g L–1. For alcohol calculation the standard deviations and coefficients of variation for literature and our relations were different (literature relations: SD = 7.37–8.53, CV = 8.33–9.52 %, our relations: SD = 7.18–13.94, CV = 7.96–16.55 %) and they were higher for the total dry extract (literature relations: SD = 16.39 16.76, CV = 45.14–49.49 %; our relations: SD = 13.70–16.73, CV = 42.68–49.16 %). The most accurate relations for separate groups of wines (white wines with different reducing sugars content or red wines) have already been published (2–6). Our own relations for calculation of alcohol level and total dry extract were obtained by means of multiple linear regression analysis. The experiment has shown that none of the results are accurate enough to be obtained using only one relation for different wines.Ispitivana je mogućnost brzog određivanja alkohola i ukupnog suhog ekstrakta u 58 uzoraka slovenskih bijelih i crvenih nepjenušavih vina, na osnovi relativne gustoće i indeksa refrakcije. Izračunati odnosi vrijednosti, koji su dobiveni iz literature, uspoređeni su s eksperimentalno utvr|enim vrijednostima dobivenim korištenjem službenih postupaka (piknometrija i hidrostatska ravnoteža). Izračunavanje udjela alkohola zajedno s ukupnim suhim ekstraktom bilo je najtočnije za skupinu bijelih vina s koncentracijom reducirajućih šećera do 5 g/L, a manje točno za skupinu bijelih vina s udjelom preko 15 g/L. Pri izračunavanju alkohola standardna devijacija i koeficijenti varijacije razlikovali su se u literaturi i u našim podacima (literaturni podaci: SD = 7,37–8,53, CV =8,33–9,52 %; naći odnosi: SD = 7,18–13,94, CV = 7,96–16,55 %), a bili su viši za ukupni suhi ekstrakt (literaturni podaci: SD = 16,39–16,76, CV = 45,14–49,49 %; naši podaci: SD = 13,10–16,73, CV = 42,68–49,16 %). Najtočniji odnosi za pojedine skupine vina (bijela vina s različitim udjelom reducirajućih šećera ili crvenih vina) već su objavljeni u literaturi. Naši vlastiti rezultati dobiveni izračunavanjem udjela alkohola i ukupnog suhog ekstrakta za pojedine skupine vina, dobiveni su multiplom linearnom regresijskom analizom. Pokusima je potvrđeno da ni jedan od rezultata nije dovoljno točan ako se koristi samo jedan relativni odnos za različita vina
