Hemiselülaz Enziminin Tam Buğday Unlu Keklerin Fiziksel Özellikleri Üzerine Etkisi

Abstract

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.

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. Quality 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. 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. Hemicellulase affected the Extensograph and Farinograph properties of flours. The energy value of strong white flour was increased by 25 ppm enzyme addition while 50 ppm enzyme showed similar effect on weak white flour. The extensibilities of white flours was increased with hemicellulase, 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. Water absorption capacity of three flours were also increased. While hemicellulase decreased the development time of weak white flour by 50 ppm addition, it increased the development time of whole-wheat flour by the same concentration. For all three flours, 25 ppm hemicellulase increased the stability value and decreased the softening degree. 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. 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. Hemicellulase caused reduction of springiness value 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. 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. The effects of cake ingredients such as egg, sugar, milk or milk powder, on hemicellulase activity is 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.