Addition of Mannoproteins and/or Seeds during Winemaking and Their Effects on Pigment Composition and Color Stability.

The increase of temperature can cause a decoupling of sugar and anthocyanin accumulation in grapes, leading to wines poor in color. Different enological techniques are nowadays under study to overcome this problem. Among them, the present study has evaluated the color and pigment composition modifications caused by the addition during Syrah winemaking of either Pedro Ximénez seeds (intended to increase chemical stability) or/and two different mannoproteins (color-protective and astringency-modulator) to increase colloidal stability. Color and pigment composition modifications were assessed from CIELAB color parameters and from HPLC-DAD-MS n results before and after cold-treatment (used to force colloidal instability). The addition of both seeds and mannoproteins increased color stability against cold and, additionally, against SO2-bleaching in the case of mannoproteins. However, the initial pigment composition and color of the samples were differently affected by these additions, being clearly affected (Δ E* ab > 3) in the cases of seeds and with the astringency-modulator mannoprotein and hardly modified with the other one.