Microstructure and Material Properties of Milk Fat Systems During Temperature Fluctuations

Investigating the impact of static destabilization mechanism on fat crystallization dynamics, emulsion rheology, and whipping properties of whipping cream

In this work, the effect of storage time on the fat crystallization, rheological and whipping characteristics of emulsions was studied and the static destabilization mechanism during storage was explored. As the storage time prolonged, peak melting temperature and onset of melting temperature increased while both the crystallization temperature and crystallization rate increased. Crystal birefringence was more pronounced at the oil/water interface accompanied by the desorption of interfacial proteins from fat droplets. The droplet size (d4,3) began to increase significantly (p < 0.05) from the 5th month. The viscosity and the elastic modulus increased from 505.2 mPa·s to 908.4 mPa·s, and from 23.53 Pa to 51.38 Pa, respectively, as storing from 1st to 7th month. The whipping time decreased while the partial coalescence rate increased from 50.84 % to 65.34 %. The whipped cream at the 3rd month exhibited a smooth surface, whereas a rough surface and lost gloss was observed at the 7th month.

Influence of Emulsifiers and Dairy Ingredients on Manufacturing, Microstructure, and Physical Properties of Butter

The influence of emulsifiers and dairy solids on churning and physical attributes of butter was investigated. Commercial dairy cream was blended with each of the ingredients (0.5%, w/w) separately, aged overnight (10 °C), and churned (10 °C) into butter. The employed additives showed a distinctive impact on the macroscopic properties of butter without largely affecting the melting behavior. In fresh butter, polyglycerol polyricinoleate (PGPR) emulsifier having dominated hydrophobic moieties significantly (p < 0.05) enhanced the softness. Among dairy solids, sodium caseinate (SC) was the most effective in reducing the solid fat fraction, hardness, and elastic modulus (G'), while whey protein isolate (WPI) and whole milk powder (WMP) produced significantly harder, stiffer, and more adhesive butter texture. As per tribological analysis, PGPR, Tween 80, and SC lowered the friction-coefficient of butter, indicating an improved lubrication property of the microstructure. The extent of butter-setting during 28 days of storage (5 °C) varied among the samples, and in specific, appeared to be delayed in presence of WPI, WMP, and buttermilk solids. The findings of the study highlighted the potential of using applied emulsifiers and dairy-derived ingredients in modifying the physical functionality of butter and butter-like churned emulsions in addition to a conventional cream-ageing process.

Food Structure Development in Emulsion Systems

A number of food products exist, in part or entirely, as emulsions, while others are present in an emulsified state at some point during their production/formation. Mayonnaise, butter, margarine, salad dressing, whipped cream, and ice cream represent some of the typical examples of emulsion-based foods. Controlled by both formulation and processing aspects, the emulsion architecture that is formed ultimately determines many of the attributes of the final food product. This chapter initially provides an overview of the basic constituents of emulsions and their influence on the microstructure and stability of conventional as well as more complex systems. The available spectrum of processing routes and characterization techniques currently utilized (or emerging) within the area of emulsions is then discussed. The chapter concludes with a concise outline of the relationship between food emulsion microstructure design and its performance (textural, rheological, sensorial, etc.).

The effect of butter grains on physical properties of butter-like emulsions

Milk fat exists as globules in its natural state in milk. The potential of using globular fat to modulate the rheological properties and crystallization behavior in butter-like emulsions was studied in the present work. We conducted a comparative study of butter-like emulsions, with a fat phase consisting of 0, 10, 25, 50, or 100% anhydrous milk fat (AMF), the remaining fat being butter grains, and all samples containing 20% water, to obtain systematic variation in the ratio of globular fat. All emulsions were studied over 4wk of storage at 5°C. By combining small and large deformation rheology, we conducted a detailed characterization of the rheological behavior of butter-like emulsions. We applied differential scanning calorimetry to monitor thermal behavior, confocal laser scanning microscopy for microstructural analysis, and low-field pulsed nuclear magnetic resonance spectrometry to measure solid fat content. By combining these techniques, we determined that increasing the fraction of globular fat (by mixing with butter grains) decreases the hardness of butter-like emulsions up to an order of magnitude at d 1. However, no difference was observed in thermal behavior as a function of butter grain content, as all emulsions containing butter grains revealed 2 endothermal peaks corresponding to the high (32.7°C ± 0.6) and medium (14.6°C ± 0.1) melting fractions of fatty acids. In terms of microstructure, decreasing the amount of butter grains in the emulsions resulted in formation of a denser fat crystal network, corresponding to increased hardness. Moreover, microstructural analysis revealed that the presence of butter grains resulted in faster formation of a continuous fat crystal network compared with the 100% AMF sample, which was dominated by crystal clusters surrounded by liquid oil. During storage, hardness remained stable and no changes in thermal behavior were observed, despite an increase in solid fat content of up to 5%. After 28d of storage, we observed no difference in either microstructural or rheological properties, indicating that formation of primary bonds occurs primarily within the first day of storage. The rheological behavior of butter-like emulsions is not determined solely by hardness, but also by stiffness related to secondary bonds within the fat crystal network. The complex rheological behavior of milk fat-based emulsions is better characterized using multiple parameters.