Chapter 32

Evaluation of Wine Grape Maturity

Wine Grape Sampling

Predicting harvest time is difficult, so growers often start sampling their vineyards several weeks before the expected harvest date. More frequent sampling should be done as the anticipated harvest date nears, especially if there are changes in the weather that could affect ripening or fruit condition. For best results, collect samples at the same time of day and the same location in the vineyard.

Vineyard Variability

It is important to recognize the high level of variability in fruit composition that exists within a vineyard and even within a single fruit cluster. Such variations within the vineyard can arise from a host of causes including vine age and health, soil water status, mixed topography and soil types, exposure of fruit, and its stage of development.

Sampling Scheme

The key to a good estimate of fruit maturity is to collect a sample that is truly representative of the entire harvested unit (i.e., block of one variety) that gives analytical results that reflect the analyses of the juice/must at the time of harvest and processing. The first step in collecting a representative sample is to develop a sampling scheme that collects fruit from vines in every part of the vineyard block.

Berry Sampling

This method involves collecting individual berries, and although commonly practiced, this method can be flawed by the tendency to sample too few berries and to select riper, more mature ones.

Cluster Sampling

Cluster sampling typically gives compositional data that are closer the fruit at harvest than that of berry sampling.

Sample Size

Sample size should be related to the size of the vineyard block and the degree of variability within the block.

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