The development of two types of emulsifier-free ice cream : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Manawatū, New Zealand
The objectives of this study were to seek and evaluate novel, effective methods to produce emulsifier-free ice cream whilst maintain equivalent quality and functionality. Based on literature analysis of fat structuring and partial coalescence mechanisms in ice cream, two hypotheses were proposed for creating equivalent structuring and functionality in ice cream without the need for chemically manufactured emulsifiers. Methodologies for characterising overrun, particle size distribution, meltdown and microscopy tests were developed to determine product properties. The first hypothesis was based on split stream mixing of non-homogenised cream to homogenised ice cream mixes prior to freezing, with the non-homogenised cream providing a fraction of fat droplets structurally pre-disposed towards partial coalescence. Non-homogenised cream was added to mixes to make up between 2 and 10% of the fat content in ice cream. A positive correlation between the contents of mixed cream and extent of partial coalescence could be observed based on the amount of non-homogenised cream added, along with related changes to ice cream functionality. The second hypothesis was to replace commercial monoglycerides in the formulation with selected long chain free fatty acids at comparable concentrations, on the basis that naturally derived fatty acids could impart equivalent surface-active functionality to monoglycerides. From the results of particle size distribution, meltdown and microscopy tests, oleic fatty acid provided the closest equivalence to monoglyceride functionality, whilst stearic and palmitic fatty acids were found to be ineffective. Findings indicate that ice cream microstructures associated with the inclusion of monoglycerides in ice cream formulations can be successfully replicated using naturally derived raw materials with minimal changes to processing.