A Brix refractometer is a simple, yet precise optical instrument used to measure the concentration of dissolved solids, primarily sugars, in a liquid sample. In forage and silage work, results are expressed in degrees Brix (°Brix). In pure sugar solutions, 1°Brix equals about 1 g of sucrose per 100 g of solution, but in plant juice, the reading represents all soluble solids, including sugars, amino acids, salts, and organic acids.
The refractometer works on the principle of light refraction, light bends when passing from air into a liquid. The degree of bending, called the refractive index, increases as more dissolved solids are present. The device has a prism where a drop of plant juice is placed; light passing through the sample is measured either via an optical scale (in handheld analog models) or an electronic sensor (in digital models), and the result is instantly displayed in °Brix.
Why Brix matters in silage
Sugar content is a key driver of fermentation. Lactic acid bacteria (LAB) convert soluble sugars into lactic acid, lowering pH and stabilizing the silage. Higher sugar levels before ensiling generally lead to faster and more complete fermentation; low sugar levels can slow the process and increase the risk of spoilage.
Measuring °Brix in freshly cut forage gives farmers a rapid estimate of fermentation potential before chopping, wilting, and packing. The refractometer is portable, requires only a few drops of juice, and provides results in seconds, making it ideal for repeated field checks during harvest and for follow up testing 24–48 hours after ensiling to track sugar use.
Continue reading this article published in Feed & Additive magazine.
