Fire can also be used to cook and concentrate sugar-rich plant juices into syrups or solid crystalline sugar. Many different plants are used to these ends, but most famously, the ancient people of Papua New Guinea domesticated the sugarcane plant, which spread to India, China, and North Africa and was much later named Saccharum officinarum by Europeans. See sugarcane. Other plants used for sugar extraction include various species of palm trees, agave, and beets (the sugar beet was specifically bred for its high sucrose content). See agave nectar; palm sugar; and sugar beet. Boiled-down plant juices provide raw sugars that usually have a brownish color. This raw sugar can then be further refined. See sugar refining and sugar, unrefined. In the twentieth century, the production of sugar has shifted from natural sucrose to enzymatically treated cornstarch generated in wet mills that turn starches into pure glucose syrup, which can then be enzymatically transformed into fructose. Industrial food companies mix glucose and fructose in a 50:50 ratio to generate high-fructose corn syrup. See corn syrup. This product represents an ironic convergence with honey, which also consists mostly of 1:1 free glucose and fructose. Honeybees cleave the nectar sugars with their salivary enzymes as they chew nectar into mature honey; this process allows honey to be 80 percent sugar, a concentration not achievable with the disaccharide sucrose found in nectar alone.