Protein removal from tobacco
Proteins and amino acids are precursors of numerous nitrogen compounds in smoke together with alkaloids. The reduction of proteins content in tobacco can contribute to reduce certain Hoffmann's analytes in smoke such as N heterocyclic compounds (quinolines, N-heterocyclic amines), aromatic amines, HCN. Proteins level in tobacco (up to 20%) is highly variable and depends on genotypes, tissue, cultural and curing conditions. The curing of tobacco significantly modifies proteins content and properties. Approximately 50% of proteins are hydrolyzed or degraded during harvesting and curing. Most of the remaining proteins have a lower solubility than in green tobacco. An overview of potential methods to remove proteins in tobacco will be presented. Proteins removal methods can be divided in two classes: proteins removal from fibres materials and from soluble extract. Proteins in fibres are strongly linked or imbedded into the tobacco matrix and their extraction is more difficult. Fibres proteins may be removed by proteins solubilisation (alkali, surfactant, salting-in treatments) or by proteins hydrolysis (enzymatic treatments). Soluble extract proteins may be removed by different techniques such as precipitation, adsorption, filtration. Factors such as pH, ionic strength, temperature, reactant concentration can improve protein solubility or precipitation. Efficiency of different treatments for proteins removal in fibres and water extracts will be reported.