الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 122 |  |  |
| | | from | 122 | | |
Abstract
Process cheese is prepared by blending natural cheese at different ages, in the presence of emulsifying salts as well as other dairy and non-dairy ingredients followed by heating with continuous mixing to form a homogeneous product with an extended shelf life. Type and age of natural cheese are the most important factors affecting the properties of process cheese. In this study, ripened Cheddar cheese for 15 days at 25°C was used for preparing process cheese spread as control. Five treatments of process cheese spread were manufactured by adding different levels of acid casein hydrolysate by pepsin (10, 20, 30, 40 and 50%) as Cheddar cheese substitute.
All of the process cheese spread formulations were balanced for moisture, fat, protein and emulsifier salts.
The resultant cheeses were then evaluated for:
1-Chemical Composition: Moisture, Dry matter, fat, Fat in dry matter, protein, soluble nitrogen at pH 4.6, ash, pH and acidity.
2-Functional Properties: Meltability, oil separation index, color and viscosity.
3-Rheological Properties: Hardness, cohesiveness, adhesiveness, springiness, chewiness and gumminess.
4-Antioxidant Activity Free amino acids and DPPH scavenging activity.
5-Sensory Evaluation.
These parameters were evaluated in process cheese when fresh and along storage for 60 days. The results indicated that the moisture, protein, fat, and ash are statistically similar. Additionally, no significant differences (p >0.05) in pH between control and treated samples (10, 20 and 30%) were found. However, there were significant differences between these samples and treated samples with 40 and 50% acid casein hydrolysate. The pH 4.6 soluble nitrogen contents presented significant differences (p >0.05) between control and treated samples as well as within the five treatment groups. Meltability, oil separation index and viscosity were significantly affected by addition of acid casein hydrolysate.
All the rheological properties (hardness, cohesiveness, adhesiveness, springiness, chewiness and gumminess) showed significant differences (p ≤ 0.05). Addition of the acid casein hydrolysate in process cheese formulas have a significant effect on the radical scavenging activity and free amino acids. All treatments were also examined for sensory quality attributes when fresh and during storage up to 60 days and indicated that the treated samples with 10, 20 and 30 were similar to the control sample whereas the treated samples with 40 and 50%casein hydrolysate were unacceptable products.
from the forgoing results it could be concluded that addition of acid casein hydrolysate up to 30% can be used in the manufacture of process cheese spread without objectionable effect on the organoleptic properties.