Seedless Raisins

The dominant variety is the Thompson Seedless (known as Sultanina in Europe and the Middle East), prized for its thin skin, lack of seeds, and balanced sweetness. Golden raisins are Thompson Seedless grapes treated with sulfur dioxide to prevent browning and oven-dried rather than sun-dried, yielding a lighter color and tangier flavor. Muscat raisins, larger and more aromatic with floral notes, are less common and often seeded. Zante currants, despite their name, are tiny Black Corinth grapes dried to intensely tangy morsels—technically raisins but distinct in character. Other regional varieties include Flame raisins (from red seedless grapes), Monukka, and Sultana varieties from Turkey, Iran, and Greece.

Raisins rank among humanity's oldest processed foods, probably discovered when grapes dried on the vine in the arid climates of the Near East, and known in Persia and Egypt by around 2000 BCE. Ancient Phoenicians and Armenians perfected viticulture and raisin production, establishing vineyards across the Mediterranean from Málaga to Corinth—the latter lending its name to currants. Raisins appear in biblical texts; David was given "a hundred clusters of raisins" by Abigail as provisions, and they adorned Greek and Roman temples as symbols of abundance. The modern seedless raisin industry traces to 1872, when grower William Thompson obtained Sultanina cuttings and planted them near Yuba City in California's Sutter County. The vines first fruited in 1875, and over the following decades his thin-skinned, seedless grape—dubbed "Thompson Seedless"—came to dominate California raisin production. According to a popular industry legend, an 1873 heat wave dried much of the grape crop on the vine, and the shrivelled fruit was sold in San Francisco as a "Peruvian delicacy"—though these were not yet Thompson Seedless grapes, and California growers had already been drying raisins on a small scale. Armenian immigrants brought centuries of expertise to the San Joaquin Valley, which today is one of the world's major raisin-producing regions.

The transformation from grape to raisin involves complex biochemistry beyond simple dehydration. As moisture evaporates—from around 80% to roughly 15–18%—natural sugars (glucose and fructose) concentrate dramatically, reaching approximately 60% of the dried fruit's weight. Enzymatic browning occurs as phenolic compounds oxidize, alongside the Maillard reaction between sugars and amino acids, creating the characteristic brown pigmentation and developing caramelized, roasted flavor notes. Some studies have reported fructans, a type of dietary fibre, in raisins that are not found in fresh grapes, though the amounts measured vary considerably. The grape's waxy skin presents a barrier to moisture loss; commercial producers often pre-treat grapes with an alkaline drying-oil emulsion (typically potassium carbonate with ethyl esters of fatty acids such as ethyl oleate) to alter the waxy cuticle and accelerate drying. Sun-dried raisins develop deeper, roasted aromatics due to prolonged heat exposure, while shade-dried and mechanically dried raisins retain brighter, fruitier volatile compounds. Nearly 100 aromatic compounds have been identified in raisins, with drying method significantly influencing the final sensory profile.

California's San Joaquin Valley is one of the world's largest raisin-growing regions, alongside Turkey, the leading producer, with somewhere around 50,000–70,000 hectares under vines in recent years. Water scarcity represents the industry's most pressing sustainability challenge, prompting investment in drip irrigation, deficit irrigation strategies, and wastewater recycling. Leading processors utilize anaerobic digesters to convert organic waste into biogas and reclaimed water. Organic raisins, grown without synthetic pesticides or fertilizers, support soil health and biodiversity but command premium prices. When possible, choose raisins from producers committed to sustainable water management, fair labor practices, and minimal chemical intervention. Look for the EU organic logo (the green leaf) or brands transparently communicating their environmental initiatives.