The effect of maceration with stem and de-stemming process on aroma and phenolic compounds of shiraz wines

Red wines were produced from Shiraz grapes grown in Şarköy by applying partial stem-contact and without stem maceration, and the effect of this process on the composition of the wines was investigated. The phenolic properties of the wines were determined by spectrophotometric method and HPLC, aroma compounds by GC-MS/FID, sensory properties by aroma and flavor profile analysis. Stem-contact maceration significantly increased the total phenolic compound, tannins, anthocynin and total acid amounts, as well as the indices of HCl and gelatin in the wine, and significantly decreased the amount of alcohol by volume, pH and color tonality (p<0.05). Stem-contact maceration was effective on the phenolic compounds of the wine; increased the phenolic acids (gallic and caftaric), flavan-3-ol (catechin), flavanone and flavonone. Higher alcohols and esters were the dominant flavor groups in both applications. Esters that positively affected the aroma of the wine were found higher in Shiraz wine produced by destemming maceration than stem-contact maceration. Although stem application enreached higher alcohols and 6 carbon compounds, the increase was'nt to the degree that there would be generate a negative flavour. It has been determined that wine produced with stem maceration has a more dominant spicy flavor, bittirness and acidity than wine produced with de-stemmed maceration. It was concluded that during the production of Shiraz wine, partial stem-contact maceration can be recommended to obtain wine that is rich in phenolic compounds and tannins and that is suitable for aging.