Study of ashes and their use to determine twig content in yerba mate

in the technique used to determine percentage of twigs in yerba mate (according to argentinean food code), the sample is sieved and separated into three fractions. in the two upper fractions twigs and leaves are separated manually. the lower fraction (<40 mesh per inch), called powder, is considered as leaves because it is very difficult to separate it manually. previous researchers predicted the twig content in this fraction, using properties that are very different in leaves and twigs (crude fiber, water extract and color parameters). in this research, another property was used in order to predict twig content in the powder: ash content. in order to obtain the calibration line, percentage of ashes were determined in samples prepared with different percentage of twigs. the fitted line had a very high estimate error (± 8.3 % of twig). using this line, percentage of twigs was estimated in commercial samples. powder fraction should contribute, additional quantities varying between 0.1 and 11.4 % to twig percentage.