Study into an alternative treatment method to sulphur dioxide in mulberry winemaking

Abstract

The characteristics of alcohol fermentation of mulberry juice treated under four different conditions of ultra-high pressure (100 MPa/10 min, 200 MPa/10 min, 300 MPa/10 min, 400 MPa/10 min), sulphur dioxide (60 mg/L), and a combination of ultra-high pressure and sulphur dioxide (30 mg/L) were assessed in this work. The volatile aroma constituents of mulberry wine made from mulberry juice using different treatments were isolated by solid phase microextraction (SPME) and identified by gas chromatography-mass spectrometry (GC-MS). A total of twenty five volatile aroma compounds of mulberry juice were identified, while nineteen volatile aroma compounds (five alcohols, four acids, and ten esters) were detected in mulberry wine. Ethyl acetate, butanoic acid ethyl ester, octanoic acid ethyl ester, acetic acid 2-phenylethyl ester, decanoic acid ethyl ester and ethyl 9-decenoate were the major esters and the main components of the mulberry wine, followed by 2-methyl, 1-propanol. Aldehydes were the major volatile fraction in mulberry wine, followed by alcohols. Pressure processing maintained the original flavour distribution of the juice. There were no significant differences among different mulberry wines in the types and concentrations of the volatile aroma components. It could be concluded that ultra-high pressure (300 MPa/10 min, 400 MPa/10 min) treatment could replace sulphur dioxide in winemaking in order to improve safety while maintaining the flavour compounds of mulberry wine.