| Abstract [eng] |
This thesis provides a quantification of physical changes in the evaporated milk stored at 30⁰C temperature, with the aim of increasing the stability of the product during storage that would favor the hot places and for long distance transportation. Thus, many types of research work have been performed to stabilize evaporated milk using different food hydrocolloids. This research thesis focuses on the utilization of hydrocolloids such as k- carrageenan (marine polysaccharide), carboxymethylcellulose and an enzyme microbial transglutaminase to enhance the stability and increase the viscosity of evaporated milk stored at 30⁰C. The steady-shear rate rheological properties, L*a*b* values, pH, dry matter content, fat content and oil droplet particle size distribution of EM under supplementation of different concentrations of k- carrageenan (0.001 %, 0.002 %, 0.003 %, 0.004 %, 0.005 %), carboxymethylcellulose (0.001%, 0.00050% and 0.00025%) and inoculation with transglutaminase (120U g-1 of protein) at different pH from (6.3 to 6.7) were evaluated. There was a greater influence on the physio-chemical properties of the EM by the addition of k-Car and CMC and by the treatment of EM with TG. The changes in colour values of the samples during the storage manifested the occurrence of Maillard reaction. The proteolysis in the samples was evident and this can be attributed to the decrease in the pH of the samples. The dry matter and fat content was higher in the upper phase than the lower phase after the separation of two phases in the samples. The flow behavior had a good fit with an Ostwald model (R2 > 0.97) and the EM samples exhibited pseudoplastic behavior and poly dispersal distribution of particle size. Due to cross-linking of milk protein, higher molecular weight macromolecules found at pH 6.6 and 6.7 in the skimmed milk. The addition of different concentration of CMC to evaporated milk had no positive impact on the stability of EM stored at 30⁰C. The samples with 0.005% of k-carrageenan had no cream separation throughout the storage period. The cross-linking of proteins by the inoculation of TG into evaporated milk did not prevent the seperation of fat and protein in the evaporated milk during the storage at 30⁰C. |
