Can you imagine trying to eat raisins with seeds in them? Who wants that? Raisins would be gritty and crunchy. That’s why almost all raisins, around 95% are made with seedless grapes. Specifically, they are made from Thompson seedless grapes, the common white seedless table grapes you find in the grocery store, which are not white, but light green in color. Thompson seedless are great for raisin-making because of their versatility. But, they weren’t always used. Before this, grapes often had seeds.
Before Thompson seedless grapes became the main cultivar used to produce raisins, seeded varieties were used. In California, the Muscat of Alexandria grape was used for decades, up until the early 1920s.
The seeds from this grape had to be removed from the grape before drying if you wanted to produce seedless raisins. This was difficult and labor-intensive. Therefore, many commercially sold raisins had seeds in them. Ask some of the older folks in your life. They may remember raisins having seeds!
Thompson grapes were the first commercially sold seedless grapes. By 1925, Thompson seedless grapes had pretty much taken over the raisin industry, and this shift happened in most of the world. These grapes can be dried successfully in a number of ways, including sun-dried or factory-dehydrated. It’s even possible to dry them on the vine. They are also useful for just about anything else you can use grapes for, including wine, and of course, eating out of hand.
Some of the advantages of the Thompson Seedless grape for raisin production include:
- early ripening
- able to be pruned and harvested by machine
- tolerant to major pests and diseases
- they make good raisins
Other names for Thompson Seedless grapes:
- Sultana: the most popular alternative name, used internationally
- Sultanina: Used in Bulgaria, Portugal, and Spain
- Sultanina bianca: Used in Italy
- Soultanina: Used in Greece
- Lady de Coverly: Used in England
- Oval Kishmish: Used in Iraq, Iran, Israel, Palestine, Pakistan, and Afghanistan
- İzmir üzümü: Used in Turkey
Other grape varieties used to make raisins are:
Muscat Of Alexandria
The Muscat of Alexandria is a white wine grape large seeds, also called Alexandria or Gordo Blanco in Australia. It is not a modern cultivar but an ancient unmodified grape and may be oldest in existence. Before the Thompson seedless grape, the Alexandria was the principal raisin grape.
Zante Currant
The Zante Currant is a small, black, seedless grape that is tart and tangy. They are also called Corinth, Corinthian, Black Corinth, Staphis, Panariti, or simply currants (unrelated to black, red, or white currants).
Monukka
The Monukka grape is a large, seedless “black” grape with a dark purple to blue color grape that produces large raisins. It is hardy used as a table grape and to produce wine although it cannot be shipped due to it’s susceptibility to skin shattering. It is a good grape for making raisins. In fact, it is thought to have originated from a Persian grape, named Munaqqa, a word that translates to ‘raisin.’ However, the color of the raisins is variable.
Flame Seedless
The Flame Seedless grape is a hardy red hybrid of the Thompson Seedless, Cardinal, and several other grapes, familiar to buyers of red seedless grapes in the U.S. These medium-large grapes have a long growing season and must be ripened on the vine, so, although they would make an excellent raisin grape, may be difficult to use commercially for raisins compared to the Thompson Seedless. However, it is a great table grape with a sweet flavor.
Ruby Seedless
The Ruby Seedless is a cross-breed of Muscat of Alexandria, Thompson Seedless and Emperor grapes first developed by H.P. Olmo at the University of California, Davis in 1939. Its release was delayed until 1968, however, because of its susceptibility to mildew and bunch rot. This red grape makes a good table grape and can be used for raisins, although being prone to bunch rot due to it’s packed clusters makes it less commercially attractive for large-scale drying.
Fiesta
The Fiesta is a complex, seedless white grape that was first made from a complex cross in 1965 and introduced in 1973. It was chosen specifically for its ability to produce very good raisins. In the past, raisin producers were concerned about traces of seeds remaining in the grape which would ruin the raisins but these concerns have been laid to rest. Planting of this grape has been steadily increasing and it is widely accepted by raisin makers. The Fiesta, however, is not grown as a table grapes due to its sensitivity to gibberellic acid (GA), which is used for a number of reasons for snacking grapes, including to induce seedlessness and produce a sweeter flavor.
