Analysis of the crystallization behaviour of plant-based mixtures of triglycerides for the formulation of vegan chocolate products

Cocoa butter (CB) products, especially chocolate, occupy a relevant position in the food industry. Addition of Milk Fat (MF) to chocolate is required to enhance sensory and physical properties of finished products. At the same time, attention to environmental issues has become a crucial factor to take into consideration as well. For this reason, together with intolerance problems customers are demanding milk free chocolate products. Hence, plant based fats step in as an alternative to animal ones. In order to be a suitable option for this purpose the replacement fats need to satisfy specific physical and chemical requirements equally to milk fat that is used because of its ability to create a product that has unique organoleptic properties. The aim of this thesis work is to analyse two plant based fat mixtures crystallization process when mixed with cocoa butter compared to MF. Cocoa butter is a mixture of triglycerides (TAGs), and because of its variable composition its crystallization behaviour is a very complex subject. CB can form six different polymorphs named from Form I to Form VI from the least to the most stable, characterised by different subcell geometry, TAGs conformation and physical properties. Milk Fat constituents are dominated by TAGs as well, although the composition is more heterogeneous than that of CB and its variability is very high. Plant based fats are made of triglycerides and show a polymorphic behaviour too. When mixed together with cocoa butter they alter its crystallization process seeming a good candidate in MF replacement. Samples of CB, MF and plant based fats and their mixtures were studied via multiple analytical techniques. Polarized Light Microscopy was used to obtain crystallization and melting temperatures and their variations when changing cooling rates. Additionally, it was used to visualize crystal growth and some perceptible changes in crystal morphology during crystallization. Moreover, thanks to Matlab software it was possible to create a qualitative trend of the crystal number in time during cooling crystallization. This allowed to identify the presence of multiple phases crystallizing at different instants and possible polymorphic transitions. Raman spectroscopy analysis of room temperature stored, molten and recrystallized samples were compared to evaluate the presence of multiple recrystallized phases. At the same time, it was useful to study the differences in the spectrum of pure compounds and cocoa butter mixtures. Differential Scanning Calorimetry, by monitoring the heat flow from the sample, allowed to detect polymorphic changes and phase transitions and the temperature related to these facts. Finally, X-Ray Powder Diffraction was used to determine the number and nature of the crystal forms obtained at room temperature storage; while Small Angle X-ray Scattering analyses consented to have a detailed understanding of polymorphism during dynamic experiments. These were performed with multiple cooling and heating ramps to have a clearer view of the crystallization process leading to more stable polymorphs. In the end crystal phases have been associated to the TAGs present in the sample that more likely were responsible for their formation. This was achieved by comparing the crystallographic results to the chemical composition of the studied samples, which ultimately led to a better comprehension of how different TAGs from different fat mixtures can interact during crystallization processes.