I have received several emails from growers regarding ranges of fruit quality parameters for cold climate grape cultivars. Several years ago, I published an extension bulletin with ranges of Total Soluble Solids (TSS; Brix %), Titratable Acidity (TA; g/L), and pH for cultivars we have grown in the West Madison Ag Station in southern Wisconsin for many years. Some of the ranges reflect over 10 years of data collection, while for some of the newer cultivars (e.g., Itasca, Petite Pearl) we only have between two to five years of data. I have updated some of these numbers (Table 1) from the original publication based on additional years of data and I also have included some of the new cultivars that were not included previously.
I would like to point out that ranges presented for each fruit quality parameter in Table 1 are based on data collected in southern Wisconsin, where we can have a slightly longer season than in many of the northern growing areas in the state, which means than in our research vineyard we might be able to achieve higher TSS levels and lower TA than in other places in the state. Also, these are averages that include years with great conditions to grow grapes, as well as cool and rainy years in which we have struggled to get enough TSS before the first fall frost. All of that to say that these are just reference numbers from one location and that when comparing them to the fruit quality levels you achieve in your location you need to take in consideration these factors.
Table 1. Fruit quality parameters Total Soluble Solids (TSS; Brix %), Titratable Acidity (TA; g/L), and pH at harvest for several cold climate hybrid grapes cultivars at West Madison Agricultural Research Station, Verona WI.