Creating a Successful Grape Sampling Strategy
The key to a good estimate of fruit maturity is collection of a sample that is truly representative of the entire harvested unit. This requires a systematic sampling strategy that collects a large enough sample, in random fashion, to objectively represent the entire crop that will be harvested and processed. A good harvest sample should give analytical results that are comparable to the juice or must at the time of harvest and processing.
It is important to recognize the high level of variability in fruit composition that exists within a vineyard, between clusters on a single vine and even within a single fruit cluster.
· Variation in vineyard soils can result in high and low vigor areas in the vineyard.
· Clusters from different parts of a vine may have very different degrees of sun exposure.
· Individual flowers open for a period of one to two weeks resulting in berries that are different ages at harvest.
· Interior and exterior berries on a cluster have different heat and light histories and as a result may have very different compositions.
The first step in collecting a representative sample is to develop a sampling scheme that collects fruit from vines in every portion of the vineyard block. Sample vines can be selected either randomly throughout the block or by a grid system (for example, every twentieth vine in every fourth row). Avoid sampling from vines at the end of rows, or from odd vines that are obviously different than the majority of vines in the vineyard block. It is best to determine the sampling scheme before you enter the block, and maintain the prescribed sampling routine.
Sample size should be related to the degree of variability within the block. Vineyards with a high degree of variability require sampling a larger percentage of the vines to obtain a representative sample.
Fruit samples should contain proportional quantities of fruit collected from exposed and shaded locations in different parts of the canopy and on opposite sides of the row. Secondary clusters and sun burned or diseased fruit should only be included in the sample if they will be harvested and processed along with the rest of the crop.
Samples may be taken as individual berries or whole clusters, but either way careful attention must be given to obtain a truly representative sample.
· Take 200 to 500 berries per block
· Take berries from random clusters on both sides of the row
· Take four berries from each cluster from the top, bottom, front and back of the cluster
A representative and repeatable sample of 200 to 400 berries taken from at least 20 to 40 clusters should be collected in the vineyard or directly from harvest containers.
Collecting cluster samples is efficient in the vineyard, but requires extra work to break cluster samples apart into loose berries prior to analysis. Many clients perform this step themselves prior to delivery of samples. If cluster samples are submitted in lieu of berry samples, a $30 sample preparation fee will apply. We encourage our clients to submit berry samples to minimize additional sample preparation fees.
Most harvest samples received at ETS Laboratories come to the laboratory as juice. When preparing berry samples, they are easily pressed by hand in their collection bag and the juice can be decanted into a 60mL sampling tube.
Cluster samples require special handling. To get a representative sample, all the berries must be stripped from the cluster. The berries are then mixed and 500 g (16 oz) of berries are submitted as a sample. A sample preparation fee will apply to all samples submitted as clusters.
Samples for ETS Juice Panels should be frozen or boiled prior to shipment to prevent fermentation. Samples for Scorpions should NOT be boiled or frozen, as this will kill yeast and bacteria cells, resulting in inaccurate results. The Enhanced Juice Panel requires two 60 mL tubes. If the samples are being shipped, one tube should be frozen or boiled to prevent fermentation. The second tube should not be boiled or frozen but kept cool to preserve DNA. We recommend that samples be shipped overnight delivery on ice packs to preserve their integrity
Harvest Juice Panel Analyses
· 60 ml juice sample - freeze or boil for shipment.
· BOILING: Boil samples with a loosely fitting cap on to prevent sample evaporation and concentration. Do not over boil.
· FREEZING: Do not overfill tube. Leave a small space for expansion prior to freezing sample. Freeze sample in plastic container - not glass - to prevent expansion breakage.
· Clearly indicate juice treatment (frozen or boiled) on each individual sample label.
Please note we are unable to run Harvest Juice Panels on fermenting samples. Order Chemistry panels and individual component tests on fermenting samples and wine samples.
· 60 ml juice sample – Keep cool for shipment.
· DO NOT BOIL OR FREEZE.
Enhanced Juice Panel (2 tubes required)
· Tube 1: 60 ml juice sample - freeze or boil for shipment
· Tube 2: 60 ml juice sample - do not freeze or boil
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