Structure and main polyphenols in the haze of blackberry wine

In this work, the structure of the haze of the blackberry wine and its main polyphenol components was evaluated. The shape of the haze of blackberry wine was observed by scanning electron microscope (SEM) and atomic force microscope (AFM), which revealed the leaf like particles with a thickness of about 2 nm. The formation of haze was associated with the accumulation of these smaller particles (rather than crystallization) to form larger particles which were preferentially precipitated to the bottom of the bottle during the aging of red wine. The main components of the haze of the blackberry wine were identified by high performance liquid chromatography (HPLC), solid state nuclear magnetic resonance (SS-NMR), Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The results showed that polyphenols and protein with proportions of 37.48 g/100 g and 18.22 g/100 g, respectively. They are predominant in the blackberry wine haze, followed by 5.10 g/100 g total sugar and 17.99 g/100 g water. Ellagic acid (EA) and sanguisorbic acid (SA), as the main polyphenols, combined with protein to form haze. Among the trace elements in haze, the contents of sulfur, phosphorus and iron were higher with proportion of 0.61 g/100 g, 0.14 g/100 g and 0.14 g/100 g, respectively. This is the first time to report the haze structure of blackberry wine and the main polyphenol compounds in haze. This work provides a reference for research on formation mechanism of the haze of fruit wine and reducing or solving of them. • The combination of polyphenols and protein constitutes haze of the blackberry wine. • The haze structure of the blackberry wine is formed by lamellar aggregation. • The thickness of haze layer is about 2 nm. • EA and SA are the main polyphenols in the haze of blackberry wine. • SS-NMR, FTIR. and other analytical methods are used to verify the two polyphenols.