Soya esaslı bileşenlerin soya ekmeği özelliklerine etkilerinin incelenmesi

Özet

Bu çalışmada, soya ürünlerinin fonksiyonel gıda bileşenlerinin belirlenmesi ve özellikle yeni bir soya ürünü olan Soya Sütü Tozunun (SST) ekmek özellikleri üzerine etkilerinin açıklığa kavuşturulması amaçlanmıştır. Bu amaçla SST’nin içerdiği bileşenleri ayrı ayrı içeren çeşitli ticari soya ürünleri ekmeğe ilave edilerek kalite özellikleri ayrıntılı şekilde incelenmiştir. Fonksiyonel bileşenler kapsamında soya ürünlerinde; fenolik madde miktarı ve profili, izoflavon miktarı ve profili ve antioksidan aktiviteler analizlenmiş ve kimyasal kompozisyon belirlenmiştir. Daha sonra SST’nin içerdiği bileşenlerle soya ekmekleri üretilmiş, taze ve depolanmış ekmeklerde kaliteyi etkileyen fiziksel ve fizikokimyasal özelliklere her bileşenin etkileri belirlenmiştir. Soya Sütü Tozu (SST), Soya Unu (SU), Soya Lifleri (Çözünür-ÇSL ve Çözünür Olmayan-ÇOSL) ve Soya Protein İzolatları (SPI, farklı denatürasyon derecelerinde) ile üretilen soya ekmeklerinde kompozisyon analizleri (nem, kül, protein, diyet lifi), fiziksel özellikler (ekmek hacmi, sertliği, ekmek içi ve kabuk rengi) ve fizikokimyasal özellikler (su aktivitesi, nem içeriği, dondurulabilir/dondurulabilir olmayan su miktarları, amilopektin kristallenmesi, sıkılık) depolama süresince analizlenmiştir. Soya ürünlerinde en yüksek fenolik madde, izoflavon miktarları ve antioksidan aktiviteleri SU ve SST için elde edilmiştir. Ekmeklerde hacim artışı ve yumuşaklığa ÇSL neden olurken, SPI 1 ve ÇOSL olumsuz etkiler göstermiştir. Depolama süresinde SST’nin bayatlamayı geciktirdiği ve bu etkinin çözünür lif ve yağ içeriğinin birlikte etkileriyle olduğu ve ÇOSL’nin ise bayatlamayı olumsuz yönde etkilediği belirlenmiştir. Soya sütü tozu ilavesi hem fonksiyonel bileşenler açısından zenginleştirme, hem de ekmek özelliklerinin geliştirilmesi açısından ekmek formülasyonlarında yararlı bir bileşen olarak ortaya çıkmaktadır.

Abstract

Positive health effects of soybean can be supplied to consumers via soy products that are widely consumed and having acceptable quality. Nowadays, soy bread is becoming one of the best food product for presenting those advantages to consumers. Use of soy ingredients in bakery products is quite limited as they yield breads having less acceptable sensory, textural and quality characteristics. The objectives of this study were to determine the functional food components of soy products and examine the role of each soy milk component on the functionality of soy-containing bread in order to understand the impact of soy milk powder (SMP) on physical and physicochemical properties of soy bread. In this content, firstly the properties of functional components in soy based ingredients were characterized. Afterwards, soy breads were produced by additions of soy based ingredients at levels that were simulating the components of SMP, and the effect of each component was determined on fresh and stale soy breads by evaluating the physical and physicochemical properties that were effective in bread quality. Chemical compositions; soluble and insoluble fiber fractions, protein and moisture contents of soy ingredients such as SMP, soy flour (SF), soy fibers (soluble-SDF and insoluble-ISDF), and soy protein isolates (SPI, at different denaturation levels) were determined. In the extent of functional component evaluation in soy products, phenolic contents/profile and isoflavone contents/profile were determined using reversed phase HPLC methods and antioxidant activities were analyzed by DPPH and ABTS radical scavenging activity methods. Soy breads were produced by addition of each ingredient as SMP, SF, soy fibers (SDF and ISDF) and SPIs (at different denaturation levels) in order to simulate SMP, and breads were stored for 7 days. In those breads, proximate analysis (moisture, ash, protein, dietary fiber) were carried out. In addition, physical properties (loaf volume, firmness, crumb and crust color) and physicochemical properties (water activity, moisture content, freezable water content, unfreezable water content, amylopectin crystallisation, stiffness) of breads were determined during storage by thermal analysis techniques. Soy products were found to be significantly different in their functional components and properties. SMP, in addition to its lower insoluble fiber content (14.2%) compared to that of SF (21.3%) also involved little more soluble fiber than SF. The highest phenolic contents in soy products were obtained for SF (3.15 mg GA/g sample), SMP (2.80 mg GA/g sample), and partly denatured SPI ingredients (2.02 mg GA/g sample). In addition, SF (2860.1 ppm) and SMP (1917.1 ppm) contained higher amounts of isoflavones and antioxidant activities than all other soy products. Insoluble fiber (10.4%) and soy protein additions (9.7-13.0%) significantly decreased loaf volumes. On the other hand, soluble fiber addition increased loaf volume (1.3%). The negative effect of SMP addition on loaf volume was associated to the higher insoluble soy fiber and soy protein contents. Addition of SPI, with its high protein content, increased bread firmness. On the other hand, soluble fiber addition provided significant softness in soy breads. At the end of storage significant differences in crumb and crust colors were found in each formulation. Generally, staling induced slight changes in crumb color. However, crust color got darker in all formulations. Moisture contents of breads decreased during staling. As the content of soy based ingredients increased, the amount of water held in bread matrix also increased. Highest moisture contents in breads were obtained with insoluble fiber (47.27%) and soy protein additions (47.63%). Soluble and insoluble fiber additions increased freezable water content in all fresh breads with respect to SF (10.0-16.3%). Lowest unfreezable water contents were observed in fiber added breads (12.3-14.3%). It was obvious that fiber additions significantly changed bread firmness during 7 days of storage. This change in firmness was found to be highest for soluble soy fiber (approximately 5 fold) and lowest for SMP (12.3%) additions. Amylopectin crystallisation increased in all breads during storage. Insoluble fiber additions significantly increased amylopectin crystallisation (from 0.01 W/g to 0.57 W/g). Soluble fiber additions (0.30 W/g) retarded staling with respect to SF bread (0.39 W/g). Especially, the lowest enthalpy obtained for SMP (0.12 W/g) added bread was attributed to possible synergistics effect of its soluble fiber and/or oil content of this ingredient.