Composition and Quality of Juices and Wines of Eight Vitis Rotundifolia Michx. Cultivars

Abstract

The composition and quality of muscadine grape juices and wines of three bronze (Carlos, Magnolia and Summit) and five purple (Noble, Regale, Tarheel, NC 94-4 and NC 154-2) cultivars were assessed over a two-year period. The grapes were grown in 1975 and 1976 in the experimental vineyard at the Delta Branch of the Mississippi Agricultural and Forestry Experiment Station located at Stoneville, Mississippi.

The composition of juices was typical of grapes grown in hot, humid climates. The soluble solids ranged from 12.8 to 19.8°Brix for the two-year period. Total acid content varied chiefly with cultivar, and to a lesser extent with the year of harvest; for example, in 1975 the acid content ranged from 0.34 to 0.83% and in 1976 from 0.38 to 0.88%. Tannins, as expected, were about twice as high in juices of red grapes as in those of bronze grapes, although their respective concentrations were generally within the limits reported for bunch grapes (0.0 to 0.2%). Six cations (Ca, Mg, K, Na, Mn and Zn) occurred chiefly in the non-solid portion of juices while Fe and Cu were found mainly in the solid fraction of juices.

Wines had an average pH of 3.22 and contained 0.71% total acid, 37 mg/100 mL volatile acid, 0.68% fixed acids, 11.9% ethanol by volume, and 46 mg/100 mL methanol. The total phenol content was about three times higher in red wines than in white wines.

Tristimulus color description of white wines showed that they had a natural light golden color with little or no variation among cultivars.

The combined means of their L values for 1975 and 1976 were 96.98, 96.38 and 95.28 for Magnolia, Carlos and Summit, respectively. Out of the five red wines, Tarheel and Noble displayed the most desirable tristimulus color characteristics. Their mean L values were 39.26 (Tarheel), and 42.22 (Noble) and their saturation values were 4.55 and 19.20, respectively. For all red wines the color description ranged from light red (NC 94-4) to dark blue-red (Tarheel).

Sensory evaluation of wines was conducted by the paired comparison preference test. The paired comparison test showed that wines with higher residual sugar contents were preferred by the majority of panelists.