Firmness and Splitting in Grapes

This year I harvested several different cultivars of grapes for the purpose of seeing what kind of firmness and splitting data I could get.  It was not a true study, just a quick “look-see” to get an idea of how it would work.  Below is some of the observations I was able to get (will help from Dr. Donna Shaw and Lavonne Stringer). Brix (sugar levels) were recorded first to see how high they were at harvest.  Nine cultivars were chosen — Blanc du bois, Champanel, Cimarron, Conquistador, FAMU99, MidSouth, Miss blanc, Victoria Red, and Villard blanc.  As you can see below, sugar levels were low for most, although these were only samples and the entire vine was not necessarily harvested.

Brix measurements of 9 grape cultivars.

Individual berries were then tested for firmness, as seen below.  In most cases, the lower the brix, the better the firmness. This is not surprising as unripe berries would be expected to be firmer.  One big exception was Conquistador which was the firmest berry by far, even at nearly 18 brix.

Firmness of nine grape cultivars.

Finally we looked at how the berries split if exposed to water. We did this in two ways, individual berries and also as whole clusters. The results were almost the same both ways but I will show both. MidSouth, FAMU99, and Conquistador showed a tendency to split when submerged in water overnight. So in this case firmness did not seem to be strongly tied to splitting tendency.

Percentage of individual berry splitting of nine grape cultivars.

Things were mostly the same when whole clusters were submerged, although there was a little more on Blanc du bois. The difference was small though and with replication and a larger sample size may not be significantly different.

Percentage of berries from whole clusters that split from nine grape cultivars.

I was surprised by the lack of splitting from Victoria red. It has what I would characterize as a thinner skin than most of these cultivars, yet it did not split at all. A good thing to know.  Obviously Conquistador has a tendency to split, as ~50% of exposed berries did just that.  Next year we will give it another go-round and see what happens then.