Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı 2

Determination of Antioxidant Capacity and Protein Contents of Some Soy Products
The soybean is the most nutritious and most easily digested food of the legumes family also one of the richest and cheapest sources of protein. Soy products (soy oil, soy meat and ground meat, soy flour, soy milk, soy cheese and soy sprout) are considered as functional food due to their content. Usage of soy proteins instead of milk proteins is an important property. Soy proteins can alternatively be used for children having allergy to animal proteins.
The purpose of this study is to determine both content of protein and total antioxidant capacity (TAC) values for products derived from soybean which is known for rich protein content and additionaly proved to be a major role for preventing cancer due to having antioxidant compounds in researches.
To determine the total protein content of soy products (soy flour, soy milk, soy ground meat, soy cheese and soy sprout), Cu(II)-neocuproine (2,9-dimethyl-1,10-phenanthroline) (Nc) total protein assay was applied using Cu(II)-Nc reagent in alkaline medium. The Lowry assay was used as comparison method.
The results obtained from Cu(II)-Nc method indicated that soy flour and soy meat have the highest protein content. BSA (Bovin Serum Albumin) equivalent results determined by the Cu(II)-Nc and Lowry methods are 63.02 and 59.4 g/100 g; 49.83 and 49.84 g /100 g, respectively. The order of other products is soy cheese > soy sprout > soy milk for both methods.
The CUPRAC method which is based on the use of Cu(II)-Nc reagent at pH 7.0 and commonly used ABTS/persulfate method were used in order to determine the total antioxidant capacities of samples. The order of total antioxidant capacities (mmol trolox/100g) of studied samples determined by the CUPRAC method were: soy flour> soy milk>soy ground meat >soy sprout>soy cheese, also by the ABTS/persulfate method: soy flour> soy milk> soy sprout> soy cheese>soy meat.
Folin-Cicalteu method was used to determine the total polyphenol contents and AlCl₃/NaNO₂ method was used to determine the total flavonoid contents.
Main isoflavone and other phenolic compounds of the studied samples were identified and quantified by reverse phase HPLC (High Performance Liquid Chromatography) method. The results showed that determined isoflavone compounds were varied from product to product. It was determined that genistin (in soy milk and soy flavor), genistein (in soy cheese and soy sprout) and daidzein (in soy meat) are the most abundant type of isoflavone.
Theoretical TAC values which are calculated with combined HPLC-CUPRAC and HPLC-ABTS methods compared with spectrophotometric TAC values. Thus, contributions of the species determined by HPLC to TAC of samples was evaluated.