Balance the tubes by adding isopropanol or extraction buffer. Produce a pellet of DNA by centrifuging at 15,000 rpm for 15 min. Gently pour off the supernatant and lightly dry the pellets by inverting the tubes on paper towels for 1-2 min.
Onions not only provide flavor, they also provide important nutrients and health-promoting phytochemicals. High in vitamin C, onions are a good source of dietary fiber, and folic acid. They also contain calcium, iron, and have a high protein quality (ratio of mg amino acid/gram protein). Onions are low in sodium and contain no fat. Onions contain quercetin, a flavonoid (one category of antioxidant compounds).
Onions provide a wealth of potential prebiotic benefits. Prebiotics are components of foods that feed or support the growth of beneficial bacteria, or probiotics, in your large intestine. A group of prebiotic compounds known as fructo-oligosaccharides is commonly used to manufacture prebiotic supplements.