Jelena Tomić

Wheat breadmaking properties in dependance on wheat enzymes status and climate conditions.

The objective of this study was to evaluate albumins profile, proteolytic and amylolytic activity level and baking performance of wheat varieties grown in two production years with different climate conditions (2011 and 2012) in four locations. The results of ANOVA showed that variety, location, production year, and their interactions all had significant effects on all tested wheat quality parameters. The enzymatic activity and specific bread volume were mainly influenced by the variety. The samples from 2012 production year, had the lower values of albumin content, proteolytic and amylolytic activity, and bread specific volume. The correlation analysis, performed for 2011 production year, showed that albumin fraction (15-30 kDa) and proteolytic activity were negatively correlated with bread specific volume indicating the role of this fraction on lowering the crucial bread quality parameter. In 2012 production year, albumin fractions (5-15 kDa; 50-65 kDa) showed the most correlations, especially with parameters of bread quality.

Determination of free sulphydryl groups in wheat gluten under the influence of different time and temperature of incubation: Method validation

The aim of the present study was to determine the characteristics of an analytical method for determination of free sulphydryl (SH) groups of wheat gluten performed with previous gluten incubation for variable times (45, 90 and 135min) at variable temperatures (30 and 37°C), in order to determine its fitness-for-purpose. It was observed that the increase in temperature and gluten incubation time caused the increase in the amount of free SH groups, with more dynamic changes at 37°C. The method characteristics identified as relevant were: linearity, limit of detection, limit of quantification, precision (repeatability and reproducibility) and measurement uncertainty, which were checked within the validation protocol, while the method performance was monitored by X- and R-control charts. Identified method characteristics demonstrated its acceptable fitness-for-purpose, when assay included previous gluten incubation at 30°C. Although the method repeatability at 37°C was acceptable, the corresponding reproducibility did not meet the performance criterion on the basis of HORRAT value (HORRAT<2).

Solid Fat Content, Pre-Crystallization Conditions, and Sensory Quality of Chocolate with Addition of Cocoa Butter Analogues

The objective of this study was to determine how the addition of two cocoa butter equivalents and cocoa butter improver affect the physical and sensory properties of chocolate. The laboratory-made chocolate samples were tempered at three different pre-crystallization temperatures (25, 27, and 29°C), using different concentrations (3, 5, and 7%) of two commercial cocoa butter equivalents as well as commercial cocoa butter improver of the chocolate. The nucleation time of the chocolate mass primarly depended on pre-crystallization temperature while the value of maximum torque of chocolate mass were influenced by both, pre-crystallization temperature and concentration of fats. Sensory evaluation revealed that cocoa butter equivalents were acceptable in chocolate formulation without producing a negative impact on the sensory quality, while usage of improver required adjustment of raw formulations or process parameters. The results of the instrumentally measured hardness revealed that addition of cocoa butter improver significantly (p > 0.05) increased hardness of chocolate samples.

Content of free amino groups during postharvest wheat and flour maturation in relation to gluten quality

The objective of this study was to monitor the changes in the content of free amino groups during postharvest wheat and flour maturation. The content of free amino groups of wheat flour was analysed immediately after wheat harvest, after 50 days of wheat storage and after 14 days of flour storage varying by wet gluten samples incubation temperatures and incubation times (0, 90 or 135 min at 30°C and after that 180 min at 37°C). The results were observed in relation to wheat-bug damaged kernels content, gluten index values, proteolytic activity and electrophoretic properties of gliadins and glutenins. The content of free amino groups increased during postharvest wheat and flour maturation periods. Proteolytic activity values were the highest 50 days after the wheat storage. The electrophoretic determination indicated a macromolecular redistribution of the gluten proteins from the moment of the wheat harvest until the moment of flour stabilisation.

Alveograph and Bread Making Quality of Wheat Dough as Affected by Added Glucose Oxidase

Although there is considerable interest in glucose oxidase, little is known about its activity on rheological characteristics of wheat dough and with bread making quality. Influence that the glucose oxidase exerts on rheological properties of the wheat dough is investigated on the basic of rheological determinations obtained with alveograph. Influence of glucose oxidase on bread making properties is determined on the basic of result obtained from the laboratory scale baking tests. In order to clearly establish relations between added dose of glucose oxidase (0.002; 0.004; 0.006 %) and rheological properties of wheat dough, as well as with bread making quality, analysis of dough with and without glucose oxidase (control sample) is performed and results are discussed with comparison with L-ascorbic acid as the most commonly used oxidative improver. Results show that glucose oxidase cause greatest increase of dough tenacity and causal reduction of extensibility. This leads to a negative effect on specific volume. Glucose oxidase cause increase of crumb hardness in smaller extent than L-ascorbic acid.

Effect of Climate Change on Wheat Quality and HMW Glutenin Subunit Composition in the Pannonian Plain

The primary goal of this study is to improve our understanding of the extent of influence of climatic factors in Serbia and high-molecular-weight glutenin subunit (HMW-GS) composition upon wheat end-use quality. In-depth analyses were performed on four bread wheat cultivars that are the most common in agricultural practice in Serbia. Total glutenin content showed significant difference between the production years, in opposition to gliadins. Cluster analysis of different percentages of glutenin and gliadin subunit molecular weight ranges ( 120,000) indicated that the year of production and the cultivar did not have a significant effect on the percentage ranges for glutenins. However, they had a considerable impact on the percentage ranges for gliadins. Production year and the interaction of year and cultivar had the strongest influences on the percentage of SDS-unextractable polymeric proteins. A synergistic effect of the HMW-GS composition and climatic conditio...

Changes in the rheological properties of wheat dough during short‐term storage of wheat

BACKGROUND The aim of the present study was to investigate the ability of the small- and large-deformation fundamental rheological tests to monitor the changes during short-term post-harvest storage of wheat. RESULTS At the end of wheat storage period, wet gluten quantity decreased, while gluten index increased in comparison to those of freshly harvested samples. The rheological properties of dough changed over the pre-defined period of storage in terms of becoming more elastic and less extensible in comparison to that of freshly harvested wheat. Visco-elastic properties of weaker flour samples changed more markedly during storage than those of stronger flours, indicating that the intensity of dough rheological changes during wheat storage might be dependent on gluten quality and were the characteristic of wheat variety. CONCLUSION It was shown that small deformation dynamic oscillation and large deformation creep-recovery tests can be successfully employed to monitor the changes in flour quality during wheat storage and that required storage period after wheat harvesting has to be defined according to wheat variety initial rheological properties and its gluten quality.

Effect of Starter Culture Addition and Processing Method on Proteolysis and Texture Profile of Traditional Dry-Fermented Sausage Petrovská klobása

Proteolysis and texture profile of Petrovská klobása, made with addition of starter culture, were investigated during the ripening in different conditions (traditional versus industrial). Due to intensive degradation of myofibrillar proteins, significant increases of non-protein nitrogen and free amino acids nitrogen contents were registered in all samples. Similar proteolytic changes were found in both starter and non-starter sausages, but were more pronounced in samples ripened in industrial room. In relation to ripening conditions hardness and chewiness differed significantly, while starter culture had significant effect only on hardness of sausages processed in industrial room.

Alpha-amylase activity in wheat flour and breadmaking properties in relation to different climatic conditions

The aim of the present paper was to evaluate the influence of different climatic conditions on the activity of alpha-amylase in wheat samples and bread quality parameters. Three wheat varieties grown in three different localities in three years were chosen for this study. Commonly used methods for estimation of alpha-amylase activity in wheat grain were employed. The obtained results indicated that harvest year 2013, which was characterized with the excessive amount of rainfall, exhibited the highest level of alpha-amylase activity and the lowest values of the peak viscosity. The lowest alpha-amylase level and the highest peak viscosity and FN value were observed for samples harvested in 2012 which was characterized with the greatest number of days with an average daily temperature above 30 and 35 °C. In addition, a decrease in Mixolab parameter torque C3 and specific bread loaf volume, as well as increase in the breakdown torque (C3-C4) of samples harvested in 2013 were observed, which could be attributed to rainy weather influencing increase in alpha-amylase activity. It is found that specific bread loaf volume of wheat samples is highest in 2012. Moreover, a negative correlation between alpha-amylase activity and specific bread volume for all the samples grown in three years was determined.

Biochemical Quality Indicators and Enzymatic Activity of Wheat Flour from the Aspect of Climatic Conditions

The contents of free sulphydryl groups (SH), disulphide bonds (SS), and free amino groups (NH2) were determined in order to estimate the extent of climatic condition influence on gluten quality. The analysis included four bread wheat varieties grown in two production years (2011 and 2012) with different climatic conditions in different locations. According to our previously reported results, the working hypothesis was that enzyme activity for breadmaking purpose was insufficient. The aim of this paper was to study the influence of naturally present enzymes on the bread quality by the addition of previously extracted and freeze-dried albumins to the base flour as an additive. The selection of samples was made on the basis of different combinations of proteolytic and -amylolytic enzymes activity levels. For samples from 2012 production year, the content of SH groups was significantly higher. Regarding the SS content, the obtained results exhibited the opposite trend. Variations in NH2 content were dominantly caused by temperature treatment of tested samples. The addition of freeze-dried albumins to bread improved its specific volume in a lesser extent, while bread crumb texture was significantly improved.