Veraison to Harvest: Grape Cluster Sampling Strategy

 Hello Dear Readers!

I hope the last couple of weeks have been treating you well. The weather has been wonderful, and harvest has slowly started. As we head into the home stretch, I thought it would be useful to focus on sampling strategy for this week. This post will be available as a fact sheet on the Perennia website soon. 

The petiole sampling fact sheet is now available online. I will be on the road for the duration of harvest and dropping in to see you, so if you would like a visit, or a check-in, do let me know.

Thank you and Happy Harvest!

GRAPE SAMPLING STRATEGY

Cluster sampling for fruit maturity after Veraison and up to harvest is one of the best techniques for monitoring and tracking crop maturity.

Grape Quality is Impacted by:

• Maturity and condition of the grapes
• aroma/flavour and phenolic characteristics
• harvesting methods, transportation and processing protocols.

Grape quality parameters agreed upon between the grape producer and the wineries are the foundation for management decisions throughout the year.

Grape quality must be defined in terms of attributes suitable for a particular wine type and style.

A SYSTEMATIC SAMPLING STRATEGY

Berries Ripen at Different Rates

A crop with asynchronous clusters or berries features a range of developmental stages, leading to a mix where some berries achieve optimal sugar levels while others may be less ripe. The key to a good estimate of fruit maturity is collection of a sample that is truly representative of the entire harvested unit.

BEFORE YOU BEGIN: EQUIPMENT NEEDED

• Plastic Zip-lock bags
• Marker (label the bags prior to placing berries/clusters inside)
• Cooler and cooling blocks/ ice (if transporting the samples long distances)
• Refractometer and lab (or sending samples to the lab)

SAMPLE SIZE REQUIREMENTS

Large enough sample, sampled randomly. The goal is to objectively represent the entire crop that will be harvested and processed. (10-30 CLUSTERS PER BLOCK)

                                         

SAMPLING METHOD

There are two basic choices in fruit sampling:

CLUSTER OR BERRY sampling.

With cluster sampling, a further choice can be made by gathering clusters from throughout the vineyard, or using one or more targeted vines.

         Berry Sampling                                                                           Cluster Samples in Cooler

CLUSTER SAMPLING METHOD

Label Sampling Containers First

• Depending on variation, sample approximately 30 clusters per sampling region. (Sample at least 10 clusters from a block)
• Plan distribution in advance and stick to the plan. Skip end vines, perimeter rows, and atypical vines. Alternate left and right sides of the aisle.
• Facing the vine, rotate sampling from the left, center, and right positions on the vine. Alternate canopy depths (near vs. far).
• Alternate between high and low position on vine. Use “blind” cluster choice.

             Crush and juice grapes thoroughly before straining, tasting, and analyzing. 

Record data and note trends.

• Pictures below illustrate the progression of cultivars from veraison to maturity.

BEST PRACTICE

• Sample and taste often in the days and weeks leading up to harvest.
• Do not sample during and right after the rain.
• Be aware that weather  such  as heat spikes or rain events will affect results.
• Crush and juice samples thoroughly.
• Smaller berries and those on the interior of clusters are often left intact and will bias your sample.

• Below is an example of a lab result illustrating the sugar accumulation at the start of veraison.

SOURCES OF BIAS

Please try to avoid these sampling pitfalls.

• Sampling from only the sun-side or only the shade- side.
• Sampling only clusters near the outside of the canopy.
• Sampling the largest, most obvious, or easiest-to- grab clusters or berries.
• Sampling from diseased or other non-representative vines.
• Sampling from end vines and perimeter rows. 
• Sample processing that doesn’t thoroughly crush the berries and homogenize the juice.

Remember: Collecting samples RANDOMLY is KEY.

Thank you all for your time and see you soon!

Cheers!

Katarina

Viticulture Specialist
Perennia Food and Agriculture
Email kvucic@perennia.ca
Office 902-678-7722

Cell 902-599-1390

 

www.perennia.ca