Browsing by Author "Kanth, Iinaroosa"

Milk based infant formulas are tailored for small children and their nutritional content is designed to mimic the nutritional content of human milk. Processing parameters such as heat treatment temperature and homogenisation pressure affect the stability of infant formulas. Product features such as solution pH and composition also have a big role in the final stability. The most common mechanisms causing instability in infant formulas are creaming and sedimentation. The aim of this study was to understand phenomena behind the stability of model infant formula emulsions. The behaviour of whey proteins and caseins and their interactions at varying solution pH before processing (pH 6.5–7.6) and processing pre-heat temperatures (60 ºC–95 ºC, 0s or 20s holding) was investigated. The effect of pre-denaturation of whey proteins to emulsion stability was also assessed. The stability of the model emulsions were analysed using mainly fat droplet size distributions, by determining the protein composition at the interface and by measuring creaming phenomena occurring over time.In addition, the amount of denaturation of whey proteins was analysed. Based on the results, alternating pH and pre-heat treatment temperatures affected in the stability of the model emulsions. Emulsions pre-heated at 90 ºC (20s holding) and 95 ºC (20s holding) led to most stable emulsion with less creaming and smaller droplet sizes than the emulsions heated at lower temperatures. In pH tests, the emulsions at pH 6.8 and 6.9 resulted in better stability than the emulsions with lower or higher pH. The pH and pre-heat treatment temperatures as well as the pre-denaturation of the whey proteins also affected the interfacial composition of the model emulsions. When model emulsions were pre-heated at 60 ºC more caseins were attached at the surface of the oil droplets whereas in increasing temperatures caseins were replaced mostly by β-lactoglobulins. In pH adjusted emulsions the amount of casein at the interface decreased when the pH of the emulsion increased. The biggest variation in the interfacial composition of the emulsions was detected in model emulsions where whey proteins were pre-denatured by pH adjustment and heat treatment. According to the study results, higher pre-heat treatments and pH values close to neutral conditions led to most stable model infant formula emulsions.