Combined effect of controlled fermented oat and jujube powder on texture and antioxidant activity of the produced wheat bread

Bread is the main source of nutrients and it is a cheap staple food in the daily diet of people in many parts of the world. One of the most important ways to improve the quality of bread is to ferment cereals and use fruit resources. Cereal fermentation has a well-known potential to improve the nutritional properties of the baked goods. It stabilizes the levels of various bioactive compounds, retards starch retrogradation and increases mineral bioavailability. A diet rich in cereal and fruit-based products could improve human health. Oat grain has a high functional potential due to its composition. This grain is known to be an excellent source of dietary fiber, antioxidants and a well-balanced protein fraction. Jujube fruit is also getting popularized due to the high content of vitamins, phenolic, polysaccharides and natural colorant agents. The quality of available commercially jujube depends on the contents of its bioactive compounds and micronutrients. There is no report about simultaneous application of fermented oat and jujube powder in processing of wheat bread. Accordingly, the aims of this study were to produce a supplemented wheat bread containing these ingredients, and evaluate the textural and antioxidant properties of the product.   

In the present study, controlled fermented oat containing selected LAB isolated from oat sourdough (as starter culture) was used to produce supplemented wheat bread. Crumb hardness, porosity, specific volume, overall acceptability and antioxidant activity in wheat bread containing fermented oat, jujube powder and their mixture were investigated in comparison with the control (wheat bread). All the experiments were done in triplicates. A complete randomized design with the least significance difference (LSD) post-hock was also used to statistical analysis of the data at p < /em>< 0.05 by SPSS (version 20) software.  

The highest amount of crumb hardness was observed in the sample containing mixture of controlled fermented oat and jujube powder, meanwhile the lowest amount of hardness was belonged to the control sample. The results of specific volume showed an inverse relationship between the values ​​of hardness and specific volume, and the lowest specific volume was observed in sample containing controlled fermented oat along with jujube powder. The highest amount of specific volume was also observed in the control sample. The porosity of all the produced breads was also significantly (p < /em><0.05) higher than the control sample, and the highest porosity was observed in the sample containing controlled fermented oat. The amount of produced gaseous compounds and carbon dioxide during fermentation affect the porosity of the produced bread. Furthermore, water retention capacity is also involved in increase in bread specific volume. Water reduces the stiffness of protein structures and allows better air to enter the dough texture and more specific volume of the product. Wheat breads containing controlled fermented oat + jujube powder and jujube powder (alone) had the highest antioxidant activity, and the control sample had the lowest antioxidant activity. During fermentation, the amount of phenolic compounds or flavonoids increases, and fermentation also causes the synthesis or release of various compounds that have antioxidant properties. Characterization of wheat bread containing the optimal formulation of controlled fermented oat and jujube powder didn’t show significant effect on the overall acceptability of the product. The presence of fiber in fortified breads is likely to increase water uptake, which in turn increases water retention capacity, reduces dough stability and increases overall acceptability. Fruits and whole grains are rich in phytochemicals such as phenolic compounds. Application of phenolic compounds in bread processing, in addition to improve antioxidant properties, affects the physicochemical properties of the dough and the quality characteristics of the produced bread due to various interactions with flour compounds such as gluten and starch. Accordingly, the combined use of plant-rich resources such as jujube powder and fermented oat, which are rich in minerals and micronutrients, can be used to improve the nutritional and quality characteristics of the supplemented wheat bread as a simple and efficient method. Due to the adverse effects of chemical additives and improvers, the importance of providing natural alternatives such as fermented substrates and plant resources in wheat bread processing is quite necessary. The best alternatives for this purpose include sourdough and fiber-rich plant. Wheat bread containing a mixture of controlled fermented oat and jujube powder had the highest crumb hardness and the lowest specific volume. Antioxidant activity in all samples was significantly higher than the control sample and wheat bread containing a controlled fermented oat and jujube powder with 90.52% had the highest amount of antioxidant activity. According to the results, controlled fermented oat and jujube powder, as functional ingredients, may be successfully incorporated into the wheat bread with positively effects on its quality characteristics.