Determination of the amount of free amino groups as an indicator of wheat flour protein complex quality

Abstract

The quality of wheat-based products is highly dependent on the quality of the used flour, where the quality of starch and protein fractions has the most dominant role. The degree of protein hydrolysis, which indicates the level of protein quality as well as the end-use flour quality, is determined by different methods (chemical, physical and rheological). The aim of this study was to determine the biochemical status of freshly harvested wheat in terms of the amount of free amino groups as an indicator of the protein hydrolysis degree. Determination of free amino groups was carried out from wet gluten by using modified method of Nielsen at al. (2001), where each sample was beforehand tempered at two different temperatures (30 and 37 °C). The temperature of 30 °C corresponds to the real baking conditions as well as it is commonly used in rheological measurements. Moreover, the temperature of 37 °C provides optimal conditions for the activity of hydrolytic enzymes present. Three wheat varieties were collected from two localities in northern Serbia in 2010/2011 production year. The selected localities were characterized with different micro-climatic conditions during grain filling and maturing. The obtained results indicated that the amount of free amino groups from the samples tempered at 30 °C to a greater extent depends on the locality, whilst the amount of free amino groups from the samples tempered at 37 °C to a greater extent depends on the variety. The further research should be carried out in different stages of post-harvest maturation of wheat as well as in optimal stage of flour maturation.