Water-soluble in the context of "Coloured pencil"

Lactose is a disaccharide composed of galactose and glucose and has the molecular formula C₁₂H₂₂O₁₁. Lactose makes up around 2–8% of milk (by mass). The name comes from lac (gen. lactis), the Latin word for milk, plus the suffix -ose used to name sugars. The compound is a white, water-soluble, non-hygroscopic solid with a mildly sweet taste. It is used in the food industry.

Gliadin (a type of prolamin) is a class of proteins present in wheat and several other cereals within the grass genera Triticum and Hordeum. Gliadins, which are a component of gluten, are essential for giving bread the ability to rise properly during baking. Gliadins and glutenins are the two main components of the gluten fraction of the wheat seed. This gluten is found in products such as wheat flour. Gluten is split about evenly between the gliadins and glutenins, although there are variations found in different sources.

Neither gliadins nor glutenins are water-soluble, but gliadins are soluble in 70% aqueous ethanol. There are three main types of gliadin (α, γ, and ω), to which the body is intolerant in coeliac (or celiac) disease. Diagnosis of this disease has recently been improving.

A proteose is any of various water-soluble compounds that are produced during in-vitro or in-vivo hydrolytic breakdown of proteins a little before producing amino acids. It forms after breaking down of polypeptides by proteases such as gastric pepsin. In addition to proteoses, peptones are also formed at this stage. The difference between peptones and proteoses is that proteoses are precipitated from solution by half saturation with ammonium sulfate, while peptones don't react even with fully saturated ammonium sulfate.