تاثير زانتان بر خواص فيزيكي و بافتي نان باگت حاوي كنجاله ارده

Effect of xanthan gum on physical and textural properties of Baguette bread containing Tahinimeal

كنجاله ارده نقش تغذيه اي مناسبي از نظر پروتيين با كيفيت بالا و مواد معدني نظير كلسيم و فسفر ايفا مي كند. جايگزيني بخشي از آرد گندم با كنجاله ارده اثرات نامطلوبي بر خواص فيزيكي و بافتي نان دارد. در مطالعه حاضر، اثرات صمغ زانتان (0، 25/0 و %5/0) بر خواص فيزيكي نان باگت داراي كنجاله ارده (0، 37/4، 45/9 و %53/14) شامل حجم مخصوص، تخلخل، رنگ مغز و پوسته نان و خواص بافتي شامل سختي، صمغيت و پيوستگي بررسي شد. آزمون هاي فوق با آرايش فاكتوريل و در قالب طرح تصادفي كامل انجام شد. خواص بافتي پس از 3، 24 و 48 ساعت نگهداري تعيين شد. نتايج نشان داد كنجاله ارده در غلظت بالاتر از %37/4 باعث كاهش معني دار تخلخل، افزايش معني دار سختي و صمغيت، كاهش معني دار حجم مخصوص درسطح %53/14 مي شود (01/0 > P). با افزايش كنجاله ارده، مولفه L* مغز و پوسته كاهش و مولفه هاي a* و b* مغز افزايش معني دار نشان داد. %25/0 صمغ زانتان تخلخل را افزايش داد ولي %5/0 صمغ باعث افت معني دار تخلخل و حجم مخصوص در مقايسه با شاهد شد (01/0 > P). با افزايش صمغ زانتان، افزايش مولفه L* مغز و پوسته و كاهش معني دار مولفه b* مغز مشاهده شد. افزايش معني دار سختي و صمغيت با افزايش صمغ زانتان از %25/0 و افزايش زمان نگهداري مشاهده شد (01/0 > P). افزايش كنجاله ارده، صمغ زانتان و زمان نگهداري كاهش معني دار پيوستگي را نشان داد (01/0 > P). با افزودن %25/0 صمغ زانتان اثرات نامطلوب كنجاله ارده بر خواص فيزيكي، بافتي نان باگت تا حدودي جبران شد.

Introduction: Nowadays, one of the most important nutritional problems in different societies is the protein mal-nutrition. Since bread is the main food material being consumed in all over the world, bread enrichment using the grains rich in protein such as sesame seeds would be an appropriate alternative. However, addition of sesame products such as Tahini meal would cause some technical difficulties such as dough stability, water absorption, dough extension time, etc. in bread manufacturing processes.In this study the effect of addition of xanthan gum to on physical and textural properties of Baguette bread containing tahini meal was investigated. Materials and methods: Wheat flour and tahini meal were supplied from Damghan and Ardakan cities, respectively. They were then refrigerated prior to baking process and different chemical tests were carried out according to standard methods. Protein was measured based on Kejeldahl method. Moisture content as well as ash content were determined using oven method.Raw fat was calculated according to AACC-No. 30-10 and raw fiber was measured using appropriate instrument (Scientific velp-FIWE6 F30530201). Starch determination was carried out using Small universal polarimeter (SUP-Germany). Xanthan gum was purchased from Provisco Ltd. (Switzerland) in food grade quality. Bread yeast (Saccharomyces cerevisiae) was also supplied in dried form. All other chemical enhancers were purchased from Merck Ltd. (Germany). Baguette dough was produced from mixture of wheat and Tahini meal flour based on protein content and the amount of protein in final dough was increased from 10.28% in flour free of tahini meal to 12, 14 and 16% in different treatments. The rest time for all flour samples was fixed at 15 min and the baking process was carried out for 15 min at 300°C. Baked breads were exposed to room temperature for two hours and then were packed using poly-ethylene (PE) film for further tests. Specific volume of bread samples was measured using rapeseed displacement method (AACC, No. 54-30, 2000). Samples porosity was determined using image processing techniques. Samples were cut to 2cm×2cmcubes and an appropriate scanner (Canoscan 8800F, Japan) with 300 pixel resolution was used to acquire the images for further process using Image J(1.6r, 2010). Apparent color for the baguette samples (in terms of CIE ‘L*’- lightness,“a*” - redness and greenness, and “b*”- yellowness and blueness) were also measured using image processing techniques (Image J, 1.6r, 2010).Texture profile analysis (TPA) test was carried out using a texture analyzer (QTS Texture Analyzer, CNS Farnell, Hertfordshire, UK) to study the effect of xanthan gum and tahini meal on parameters such as hardness, gumminess and cohesiveness in all baguette samples. Results and discussion: ANOVA test showed the significant effect of xanthan gum and tahini meal on the porosity of samples. The porosity of samples containing less than 0.5% xanthan gum at all tahini meal levels, was significantly less than control sample.Similar results were obtained in the case of specific volume meaning that the employed treatments have significant effect on bread’s specific volume. Increasing tahini meal from 9.45% to 14.53% caused significant decrease in specific volume. This could be due to the weakness of dough gluten matrix. These results are in agreement with other works reported by other researchers (Paraskevopoulouet al., 2010; Mohammad Idrisset al., 2012; and Guardaet al., 2004). The results obtained for apparent color of bread core also showed the effect of xanthan and tahini meal. The only exception was found in case of a* value when studying the effect of xanthan gum, meaning that xanthan gum has no significant effect of this parameter. In the case of apparent color in bread crust, the studied treatments (xanthan gum and tahini meal) showed significant effect on all color parameters. Different textural properties of baguette samples including hardness, gumminess and cohesiveness were also measured. Conclusion: The results indicated obvious effect of xanthan gum and tahini meal levels on these mentioned parameters. Increasing tahini meal and xanthan gum levels would increase hardness as well as gumminess. However, addition of xanthan gum and tahini meal cause significant decrease in cohesiveness. This could be due to dilution effect of these substances which decrease the concentration of protein matrix existed in flour’s gluten.