Date

2022-2-11

Author

Tırpancı, İrem Bige

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Acidified milk drinks (AMD) has recently gained popularity due to their nutritional aspects. Most of these drinks suffer from sediment formation and wheying off during shelf life and in order to prevent it, hydrocolloids such as pectin is used as stabilizers. It is important to have a stable beverage without sacrificing milk protein content. Moreover, having an alternative pasteurization method such as High Hydrostatic Pressure (HHP) rather than a thermal treatment could also be a better choice to protect nutritional and sensorial properties. Considering all these and fragmentation effect of HHP on milk proteins, it was hypothesized that HHP may enhance the pectin adsorption onto caseins and help obtaining a physically stable beverage. Therefore, the aim of this study was to use HHP as a pasteurization method and observe its effects on the stability of the AMD in comparison with heat treatment. For this manner, HHP was applied at 100, 300 and 500 MPa for 5 minutes at 25 °C and sedimentation ratio, Brixº, soluble protein amount were measured and particle size analysis was done in comparison with heat treated control samples which were pasteurized at 75 °C for 15 minutes. Finally, at a selected condition where the stability was maximum (0.5% pectin), Turbiscan analysis was carried out. It was shown that either by thermal process or HHP, pectin concentration and pH are significant parameters for the stability of AMD. It was seen that a pectin dosage of 0.2% is not enough to stabilize the beverage. At pH 5, system was not stable either. The lowest brix values and protein solubility and the highest sediment ratios and serum separations were observed with 0.2% pectin at pH 5. The average particle size at pH 5 was significantly higher compared to the other samples and size distributions were in broader ranges. Protein aggregation by HHP became more visible at pH 5. However, at pH 4 and 4.5, HHP provided stable results. Therefore, it was seen that when there is sufficient and effective pectin support in the system, HHP could be utilized instead of heat treatment. Turbiscan stability assessment also justified that, at a certain pectin concentration and lower pH values, HHP could provide comparably stable products over heat treatment.

Subject Keywords

Acidified milk drink, High hydrostatic pressure, Stability, Turbiscan

URI

https://hdl.handle.net/11511/96357

Collections

Graduate School of Natural and Applied Sciences, Thesis