Determination of titratable acidity in white wine

Abstract

The amount of titration acid in must is in the largest number of cases with in the range 5.0-8.0 g/dm3. Wines, as a rule, contain less acids than must, and according to Regulations, titratable acidity is in the range of 4.0-8.0 g/dm3 expressed in tartaric acid, because a part of tartaric acid is deposited in the form of salts (tartar or argol) during alcohol fermentation. For wines that contain less than 4 g/dm3 of titratable acids there arises a suspicion about their origin, that is, that during the preparation some illegal acts were done. Because of that, the aim of this paper is to determine titratable acidity in white wine, using standard methods of determination, which are compared with the results received by potentiometric titration using ion-selective electrode. According to the received results it can be seen that wine titration with indicator gives sufficient reliable values of wine titration acidity. However, as potentiometric titration at pH value 7.00 is more reliable and objective method, the values of titratable acids content in wine, expressed through tartaric acid, are given according to this result. The analysis of differential potentiometric curves shows that these curves can give us an answer to the question of the presence of a larger amount of other nonorganic substances, which have already existed in wine. However, none of the used methods gives absolutely reliable answer what substances are present in analysed samples.Kolicina titracionih kiselina u siri se, u najvecem broju slucajeva, krece izmedju 5 i 8 g/dm3. Vina, po pravilu, sadrze nesto manje kiselina nego sira, a prema Pravilniku, titraciona kiselost se krece izmedju 4,0 i 8,0 g/dm3 izrazeno u vinskoj kiselini, jer se deo vinske kiseline istalozi u obliku soli (stresa) u toku alkoholne fermentacije. Za vina koja sadrze ispod 4 g/dm3 titracionih kiselina postoji sumnja u njihovo poreklo, tj. da su prilikom njihovog spravljanja vrsene nedozvoljene radnje. Zbog toga je cilj rada bio da se izvrsi odredjivanje titracione kiselosti u belom vinu, standardnim metodama odredjivanja koje su uporedjene sa rezultatima dobijenim potenciometrijskom titracijom uz jon-selektivnu elektrodu. Na osnovu dobijenih rezultata uocava se da titracija vina uz indikator daje dovoljno pouzdane vrednosti titracione kiselosti vina. Medjutim, posto je potenciometrijska titracija, pri pH vrednosti 7,00, pouzdanija i objektivnija metoda, vrednosti za sadrzaj titracionih kiselina u vinu, izrazenih preko vinske kiseline, date su upravo na osnovu ovog rezultata. Analiza diferencijalnih potenciometrijskih krivih, ukazuje da ove krive mogu pruziti odgovor na pitanje o prisustvu vece kolicine drugih neorganskih supstanci, koje se vec nalaze u vinu. Medjutim, ni jedna od ispitivanih metoda ne daje dovoljno pouzdan odgovor koje supstance su prisutne u analiziranim uzorcima, vec odgovor na ovo pitanje moze pruziti jedino metoda jonske hromatografije.