The Effects of Leaf and Cluster Shading on the Composition of Cabernet Sauvignon Grapes and on Fruit and Wine Sensory Properties

A comparison was made between the effects of leaf shading and cluster shading on grape composition and fruit and wine sensory properties. The experimental design permitted selective natural shading of grapevines while maintaining identical vine vigor and viticultural practices. The rates of berry growth and sugar accumulation were slower in fruit from vines with shaded leaves. Leaf shading also decreased both the rate of pre-veraison malate accumulation and the rate of post-veraison malate decline. Malate, potassium, and pH were higher in fruit from the leaf shading treatments at harvest. Shading clusters did not affect sugar, acid, or potassium accumulation, but anthocyanins and total soluble phenols were lower in fruit that developed in shade. Total vine shading slowed the rate of tartrate accumulation but did not affect the final tartrate content at harvest. Neither leaf nor cluster shading alone affected tartrate accumulation. Sensory evaluation of the aroma of crushed fresh grapes detected differences between the aroma of the control and each of the shade treatments. Similarly, wines made from fruit of the control treatment were significantly different in aroma and flavor from wines made from the three shading treatments.