Hemiselülaz enziminin tam buğday unlu keklerin fiziksel özellikleri üzerine etkisi
Effect of hemicellulase on whole wheat flour cake's physical properties
Yazar: YUSUF YAVAŞ
Danışman: PROF. DR. DİLEK BOYACIOĞLU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Gıda Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2012
Konu: Gıda Mühendisliği = Food Engineering
Dizin: Buğday kepeği = Wheat bran ; Buğday rüşeymi = Wheat germ ; Buğday unu = Wheat flour ; Doku analizi = Texture analysis ; Enzimler = Enzymes ; Hacim analizi = Volumetric analysis ; Hamur = Dough ; Kek = Cake ; Tahıllar = Cereals

Özet:
Bu çalışmada tam buğdayın sıklıkla tüketilen unlu bir mamul olan keklerde kullanılması araştırılmıştır. Bu amaçla hem tam buğday ununun kullanım alanını arttırarak ürün çeşitliliği kazandırmak; hem de keklerin besleyici değerinin arttırılması hedeflenmiştir. Tam buğday teknolojisindeki mevcut sıkıntılar göz önüne alınarak hemiselülaz enzimi katkı olarak kullanılmış ve kekin fiziksel özelliklerine etkisi araştırılmıştır.Hemiselülaz enzimi özellikle ekmek üretiminde hamurun işlenebilirliğini arttırarak, homojen yapılı, düzgün hacimli, yumuşak dokulu bir ürün elde edilmesini sağlar. Kek üretiminde hemiselülazın kullanılmasına dair yeterli bilgi bulunmamakla birlikte bu ürünleri de olumlu yönde etkileyeceği düşünülmüştür.Çalışmada bir kuvvetli beyaz un, bir zayıf beyaz un ve bir de tam buğday unu olmak üzere üç un örneği kullanılmıştır. Unların kalite analizleri yapılmış, hemiselülaz enzimi ilave edilerek elde edilen hamurların reolojik özellikleri belirlenmiştir. Hemiselülaz enzimi ilavesi Ekstensograf enerji değerinde, Farinograf su kaldırma ve stabilite değerlerinde artışa neden olmuş; Farinograf yumuşama derecesini ise düşürmüştür.Tam buğday ununun iki farklı tip un ile (kuvvetli ? zayıf) %0, %25, %50, % 75 ve %100 oranında ikame edilmesi ve hemiselülazın üç farklı oranda (0, 25, 50 ppm) ilavesiyle kek denemeleri yapılmıştır. Kekler 175°C 'deki fırın sıcaklığında 60 dakika süreyle pişirilmiştir. Piştikten sonra soğutulan keklerin hacmi kolza ile yer değiştirme metoduyla ölçülmüştür. Spesifik hacim, ölçülen hacmin kek ağırlığına bölünmesiyle bulunmuştur. Hacim ölçümü yapılan kekler plastik ambalajlara konup saklanmış ve bir sonraki gün doku analizi yapılmıştır. Doku analizi, doku analizörü ile yapılmış ve keklere ait sertlik, yapışkanlık, elastiklik, bağlılık, sakızımsılık ve çiğnenebilirlik değerleri elde edilmiştir. Sonuçlar istatistiksel olarak değerlendirilmiştir.Tam buğday ununun paçallarda kullanılmasıyla hacim ve spesifik hacim değerlerinde olumsuz bir etki tespit edilmemiştir. Hemiselülaz enziminin yalnızca tam buğday unu içeren keklerde önemli derecede arttırıcı etkisi görülmüştür. Ancak diğer unlarla yapılan keklerin hacim özelliklerini geliştirmemiştir. Tam buğday unu, kuvvetli beyaz unla ikame edildiğinde sertliği azaltıcı etki göstermiştir. Aynı zamanda yapışkanlık, sakızımsılık ve çiğnenebilirlik üzerine olumlu katkı sağlamıştır.Hemiselülaz enzimi zayıf beyaz unda sertliği azaltarak olumlu etki göstermiş ancak elastiklik değerini düşürmüştür. Çiğnenebilirlik ve sakızımsılık üzerine olumlu etki etmiş ancak istatistiksel açıdan önemli fark görülmemiştir. Hemiselülaz keklerin bayatlamasını geciktirici katkı sağlamıştır.Tam buğdayın kek formülasyonlarına katılarak kek kalitesinin geliştirilmesi önerilmektedir. Ancak hemiselülazın kekler üzerine etkinliği üzerine ileride yapılacak araştırmalara ihtiyaç duyulmaktadır.

Abstract:
Publications reporting the importance of whole grain products on human?s nutrition are outnumbering day by day. Thus, the interest on whole grain products is rapidly increasing. Whole grain foods are playing very important role to compensate the need for functionally nutritive foods. They include some nutrients, which are known for their prevention from cardiovascular diseases, cholesterol and some cancer types. Whole-wheat flour products are the most preferred ones among the functional foods, as they are rich sources of dietary fiber, vitamins and minerals.On the other hand, there are some technological troubles faced with the whole wheat breads and other products that are derived from whole wheat. Whole-wheat flour and their products have shorter storage time. Besides, the machinability of their dough is lower and it decreases the quality and yield of bread. Thus, these factors are limiting the manufacture of these products. Additionally, their negative effects on texture, appearance, taste and flavor are restricting the interest to the whole-wheat products. In recent years, many studies are performed in order to increase the quality and acceptability of products with whole-wheat flours.In this study, the use of whole-wheat flours in cake products, which are commonly consumed, was investigated. For this purpose; the variety of whole-wheat products will be increased and the nutritional value of cakes will be increased. Considering the problems in the manufacture of whole-wheat products, hemicellulases are used as an additive to improve cake?s physical properties.Hemicellulases increase the machinability of dough, so they provide homogeneous and soft texture and well-shaped volume in bread production. There is not much information about use of hemicellulase in cakes, but their positive effects are important.Three different flour samples were used in this study: strong white flour, weak white flour and whole-wheat flour. Qualities of wheat flours were analyzed. Rheological properties were followed with the addition of hemicellulase enzyme. Hemicellulase addition increased the Extensograph energy value, Farinograph water absorption and stability values, but decreased the Farinograph?s softening degree.Whole-wheat flour was substituted with two types of flour (strong ? weak) with substitution of 0%, 25%, 50%, 75%, and 100%. With the addition three levels of (0, 25, 50 ppm) hemicellulase, cakes were prepared and baking were tested. Cake dough was prepared by mixing sugar with egg and then adding liquid ingredients (milk and oil) and dry ingredients (flour mix, vanilla, baking powder and hemicellulase) which were previously mixed. Then all ingredients were mixed and whipped. Prepared cakes were baked in the 175°C oven temperature for 60 minutes.After baking, cakes were cooled for volume measurement with the rapeseed replacement method. Specific volume was determined by dividing cake volume to cake weight.Following the volume measurements, cakes were stored in plastic packages until texture profile analysis were tested for the next day. Texture profile analysis was performed with texture analyzer. Values for hardness, adhesiveness, springiness, cohesiveness, gumminess and chewiness were obtained. Results were evaluated statistically.Quality parameters of flours indicated that whole-wheat flour has higher amount of ash (0,969) than other flours, as expected. Gluten and sedimentation values of weak white flour were very low that these results confirmed that it is weak type flour. Besides gluten, (28.1) and sedimentation (34-40) values of strong white flour were high and it is accepted as strong type flour.Hemicellulase affected the Extensograph and Farinograph properties of flours. The energy value of strong white flour was increased by 50 ppm enzyme addition while 25 ppm enzyme showed similar effect on weak white flour. Nevertheless, 25 ppm enzyme addition decreased the energy value of whole-wheat flour. Hemicellulase increased the extensibilities of white flours, but it decreased the extensibility of whole-wheat flour. Resistance to extension of weak white flour and whole-wheat flour were increased with the addition of hemicellulase, but that parameter of strong white flour was not change with the enzyme addition. With 50 ppm hemicellulase addition, water absorption capacities of three flours were increased significantly.While hemicellulase increased the development time of whole-wheat flour by 50 ppm addition, it did not cause to change the development time of strong white flour by 25 or 50 ppm enzyme. For both two levels of enzyme addition, the development time of weak white flour was decreased. For all three flours, 25 ppm hemicellulase increased the stability value significantly but 50 ppm enzyme did not alter the stability values of flours. Hemicellulase addition decreased the softening degree of all flours, and this decrease was observed significantly by 25 ppm enzyme.Cake tests were performed in combinations of two refined white flour having different characteristics with whole-wheat flour. In overall evaluation, cakes made using weak white flour have better quality than the ones made with strong white flour. In general, addition of whole-wheat flour to cake mixtures did not affect negatively. Physical properties were not much influenced in substitutions with weak white flour. In substitutions with strong white flour, addition of whole-wheat flour has influenced positively, volume and specific volume were improved. Whole-wheat flour provided cakes with softer texture and higher chewiness quality in cakes made with strong white flour. It also decreased adhesiveness in cakes made with weak white flour.Effect of hemicellulase on cakes showed variability. Because of high standard deviation, differences were not statistically significant and effect of enzyme on volume was not observed. Nevertheless, volume and specific volume was increased significantly in cakes made with only whole-wheat flour. The highest increase rate was observed on 50 ppm enzyme added cakes made with strong white flour with 8.6%. Effect of hemicellulase was more positive on cakes including high level of whole-wheat. 25 ppm enzyme addition decreased cake volumes made with weak white flour, but higher levels of enzyme did not influence this property.The highest decrease rate was observed on 25 ppm enzyme added cakes made with weak white flour and whole-wheat flour with 10.2%. In overall evaluation volumes of cakes made with weak white flour were much higher than those made with strong white flour.Cake weights are measured and the results are obtained between 358.55 and 366.63 grams. Because of different loss of weight, specific volumes of cakes are varied. The highest increase rate was observed on 50 ppm enzyme added cakes made with whole-wheat flour with 9%. Maximum specific volume value was determined on cakes made with whole-wheat flour (25%) and weak white flour. On the other hand, the highest decrease rate and minimum value was determined on cakes made with whole-wheat flour (25%) and strong white flour.Hemicellulase addition caused small changes on hardness value but these changes were not statistically significant. Hardness values of cakes made with strong white flour were higher than cakes made with weak white flour and the maximum hardness value was obtained on cakes made with 25 ppm enzyme added 100% strong white flour. Adhesiveness values of cakes were increased by 25 ppm hemicellulase addition on weak white flour and by 50 ppm hemicellulase addition on strong white flour.Hemicellulase caused reduction of springiness and cohesiveness values of cakes made with weak white flour, generally. On the other hand, it improved the chewiness and gumminess qualities of cakes with strong white flour, but not statistically significant.In cakes with strong white flour, hemicellulase did not much affect staling of cakes. As the percentage of whole-wheat in cakes increased, staling rate of cakes also increased. 25 ppm enzyme addition decreased staling rate in cakes with weak white flour more than other cakes.The effectiveness of hemicellulase on cakes needs to be investigated much more. In this study, effect of enzyme on different types of flour was different. For this reason, the optimum level must be determined for different types of flour. Besides, effect of different types of hemicellulases on cakes needs to be investigated.The effects of cake ingredients such as egg, sugar, milk or milk powder, on hemicellulase activity are not known exactly. During fermentation of bread, hemicellulase can also be activated. However, cakes are directly taken to the oven for baking right after they are prepared. It is estimated that hemicellulase cannot find the time period for activation when it is thought that they are usually activated in ambient temperature. It is guessed that using thermophilic enzymes, which can activate at higher temperatures in cakes, can generate desired results. Further studies are needed for the enlightenment of these subjects.It is shown that whole-wheat flour can be used in cakes but optimum level for use must be determined. The interest to the whole-wheat products is based on its naturalness. Hence, microbial enzymes must be preferred to improve the properties of a product, instead of using chemical additives that deteriorate the naturalness of it. With the production of whole-wheat flour cakes, a product with high nutritional value can be derived especially for youth and children.