Post-harvest content of free titratable acids in the grain of proso millet varieties (Panicum milliaceum L.), and changes during grain processing and storage

Abstract

A triennial evaluation of the content of titratable acids (TA) in grain was carried out on 12 varieties of proso millet (<I>Panicum miliaceum </I>L.). The model variety, Mironovskoe 94, harvested in 2004, was used for the monitoring of sensory changes in TA content, in relationship to different storage conditions and the application of different grain processing methods. The Czech state norm (CSN 56 0512-9 1995) Determination of Titratable Acids, with a slight modification, was used as the standard method. The TA contents in dry matter varied between 39 and 78 mmol/kg of grain dry matter, and significant differences between varieties and experimental years were found. The method of proso millet processing had a key role in the final sensitivity to rancidity. The storage conditions had a much lower influence on TA content than the processing technology. The clearly detected sensory changes found in scoured grains corresponded with TA contents within the range of 90 to106 mmol/kg. The monitoring of the TA content can be considered as a suitable tool for the prediction of rancidity processes in millet grains.