Droplet Size Distribution of Oil-in-Milk Emulsions: Continuous Emulsification via a Vortex-Based Hydrodynamic Cavitation Device

The continuous generation of oil-in-milk emulsions is gaining increasing interest in the food industry. In this work, flaxseed oil-in-milk emulsions were produced continuously for the first time using a vortex-based hydrodynamic cavitation device (VD). A loop configuration was used for operating the device in a continuous mode. The droplet size distribution (DSD) of oil-in-milk emulsions with a surfactant (sodium lauryl sulfate) was measured. The influence of the oil volume fraction (α_o = 0.05–0.45), effect of pressure drop (ΔP = 100, 150, and 200 kPa), and ratio of flow through VD, Q, and emulsion, (Formula presented), on DSD was investigated. DSD was found to be bimodal in nature. The Sauter mean diameter (d₃₂) was found to increase with α_o. A new empirical correlation was developed to predict d₃₂ as a function of the key operating parameters. The DSD and key characteristic diameters (d₃₂, D₁₀, D₅₀, and D₉₀) of FO in milk emulsions were estimated for the first time using an at-line characterization methodology based on an inexpensive voltage sensor and an ANN model. The methodology was validated by comparing the predicted DSD with experimental data. This work demonstrates that the presented approach of using VD in a loop configuration leads to emulsions with a Sauter mean diameter of less than 5 μm and energy consumption per unit mass of emulsion of less than 10 kJ/kg. The results presented will be useful for developing and establishing continuous milk-based emulsions.