Ekmeklik Buğday Kalitesini Değerlendirmede Kullanılan Kimyasal ve Fiziksel Özelliklerin İncelenmesi

Abstract

Differences in the quality evaluation of wheat, based on usage areas and quality-analysis methods, make accurate evaluation of wheat quality and price quotation difficult during peak purchasing periods in the commodity exchange markets. In our country, the most common parameter used in the evaluation of wheat quality and price quotation at the commodity exchange markets is the total protein content determined by the NIT method, which is fast and simple. Dumas total protein, wet gluten, and Zeleny sedimentation analyses that require the grinding of the sample are time consuming and, therefore, cannot be used to evaluate the quality at the commodity exchange markets. The relation between wheat, classified as red/white and hard/other based on color and hardness, and the quality parameters, such as the amount of total protein, amount of gluten, and the sedimentation value or the grain size is not reported to date in the literature. In this study, 39 red and 18 white pure bread wheat samples of 22 different varieties received at the Ankara Commodity Exchange Cereal Technology Laboratory mainly from the Central Anatolian Region during the 2013-2014 harvesting season were used. Samples were analyzed by using the total protein content (%), wet gluten content (%), and Zeleny sedimentation (ml) methods and the grain volumes were calculated. The results were grouped and analyzed based on grain color as red or white. Mathematical relations between the parameters were computed. For all samples, total protein content values obtained by employing the NIT and Dumas methods were found to be consistent. The TMO assigned criteria of 12.5 % total protein content was used to confirm the main classification group for each sample as ‘‘hard’’ or ‘‘other’’. Results from NIT and Dumas analyses were found to be contradicting for some samples with total protein content near the TMO threshold value. This shows the necessity to choose a single method for total protein content analysis to be employed on all samples when determining the main classification group. For red and white samples, the average total protein contents were found to be close to each other as 13.15 % and 13.49 %, respectively, indicating that the grain color is not a useful predictor of the protein content. A strong linear relationship was observed between total protein content and wet gluten content with a coefficient of determination around 0.7. Thus, one of these parameters can be used to estimate the other. As a result of the linear regression analyses between Zeleny sedimentation value and total protein content and next, wet gluten content, the coefficients of determination were found around 0.5 and 0.3, respectively. Consequently, these parameters cannot be used to estimate the Zeleny sedimentation value, which is an indicator of bread making quality. The average Zeleny sedimentation value was found as 41.0 ml for red wheat samples and 33.4 ml for white wheat samples. This indicates that the examined red wheat varieties may have better bread making potential than the white ones. Some wheat types with small grain volume were observed to have relatively higher values of protein content, wet gluten content, and Zeleny sedimentation. These properties were found at lower levels for wheat types with large grain volumes. A similar relationship between the grain volume and the other properties does not exist for the samples of the same wheat type grown in different locations. The differences in the analysis results of all wheat samples grown in different areas of the Central Anatolian Region demonstrate that environmental and growing conditions affect the quality of the crop. Further studies are needed to develop a fast and simple method for use in quality evaluation of wheat. Future work includes detailed spectroscopic analysis of protein and starch components in wheat, comprehensive evaluation of grain color to form a color index, and investigation of the correlations between the physical and chemical properties of wheat and its mechanical properties, such as hardness and strength.