d), cranberry fruit extract7, peppermint extract8 or replacement of milk fat of cheese with hazelnut oils9 and vegetable oils10.
No attempt has been made so far to study qualitative properties of processed cheese containing tomato powder (PCT) and processed cheese containing asparagus powder (PCA). The aim of this study is improving the health attributes of processed cheese and investigating the effect of adding tomato and asparagus powders on the rheological and physicochemical properties of processed cheese.
MATERIALS AND METHODS
Material: Processed cheese samples containing tomato powder, were prepared in a Stephan Vacuum Vertical Mixer (Stephan Machinery Corp., Mundelein, Ill., U.S.A.) by melting a mix of feta cheese, butter (3%), water (5%), emulsifier salts (2%) (Tri sodium citrate E331 (1%) and di sodium phosphate E339 (1%); Sigma-Aldrich Chemie Gmbh, Munich, Germany) and tomato powder (1%, 2% and 4% wt/wt) at 85°C for 4 min at 1500 rpm. The molten cheese samples were then hot-filled into rectangular molds, cooled to 4 ◦C, and stored at that temperature.
Processed cheese samples containing asparagus powder were prepared in the same way by adding asparagus powder (0.5%, 1% and 1.5% wt/wt). Tomato and asparagus powders were prepared by grinding of dried tomato and asparagus by a grinder (Pars Khazar Grinder Chili, Iran). Qualitative analysis including measurement of dry matter content, fat content, pH, lipolysis, proteolysis, water-soluble phenolic content (WSPC), lycopene content and antioxidant activity (AOA) were carried out on days of (1, 20, 40, 60 and 90). Rheological measurements were analyzed after 20 days of storage.
Chemical Analysis: Dry matter content was determined by drying at 102 °C to a constant weight according to the IDF, 198211. Fat content was determined by the Gerber method described by Marshal12. The pH of the samples was estimated at room temperature with the direct insertion of a glass electrode into the sample, using a previously standardized digital pH meter (PHC3031-9, Radiometer Analytical, Copenhagen, Denmark) according to the method described by Marshal12. Protein concentration was determined by the Kjeldahl method13.
Water-Soluble Phenolic Content: The water-soluble phenolic content was measured via the Folin- Ciocalteu procedure, according to an assay modified by Shetty et al.15. Homogenized water extract, was prepared by the method of Apostolidis et al.16, and 1 ml was transferred into a test tube and mixed with 1 ml of 95 % ethanol and 5 ml of distilled water. To each sample, 0.5 ml of 50 % (V/V) Folin- Ciocalteu’s reagent was added and mixed. After 5 min, 1 ml of 5 % Na2CO3 was added to the reaction mixture and allowed to stand for 60 min. The absorbance was read at 725 nm in a spectrophotometer (Jenway, Model 6305, UV/Vis., England). The absorbance values were converted to water-soluble phenolics and were expressed in mg gallic acid equivalents per gram of dry matter of sample. Standard curves were established using various concentrations of gallic acid in water.
Antioxidant Activity (AOA) by DPPH Radical Scavenging Assay: The capacity to scavenge the 2,2-diph
