Coencapsulation of polyphenols and anthocyanins from blueberry pomace by double emulsion stabilized by whey proteins: Effect of Homogenization parameters
Bamba, B.S.B., Shi, J., Tranchant, C.C., Xue, S.J., Forney, C.F., Lim, L.T., Xu, W., Xu, G. (2018). Coencapsulation of polyphenols and anthocyanins from blueberry pomace by double emulsion stabilized by whey proteins: Effect of Homogenization parameters. Molecules, [online] 23(10), http://dx.doi.org/10.3390/molecules23102525
Plain language summary
Polyphenols are known for their strong antioxidant properties and potential health benefits,including the prevention of diet-related chronic illnesses such as type 2 diabetes, cardiovascular diseases, neurodegenerative diseases and some cancers. Polyphenols can be obtained through the diet by regular consumption of plant-based foods, specifically fruits, vegetables, cereal grains and certain beverages. However, the contents and types of phenolic compounds in these foods vary greatly, which can limit their dietary intake. Increasingly, the food and pharmaceutical industries aim to deliver these health-promoting compounds to consumers in various forms, such as fortified foods, functional foods and beverages as well as dietary supplements. This presents considerable challenges, however, as polyphenols are generally unstable following their extraction from plant materials. They are prone to undesired inactivation or degradation under conditions that typically occur in foods and during food processing, such as low or high pH, heat, presence of enzymes, proteins, metallic ions, oxygen and light, leading to losses in their biological activity and functionality. In addition, many phenolic compounds have a relatively low solubility in food matrices and low bioavailability in humans. Some have an unpleasant odor, bitter taste. Microencapsulation has proven an excellent method to protect food ingredients against adverse reactions, deterioration and undesirable interactions with other ingredients, to improve their solubility and mask unpleasant off-flavors. The multicore-microencapsulation can improve the bioactivity of the individual compounds due to synergistic effects. Polyphenol-rich extracts typically contain various phenolic compounds, which may promote the health benefits of the extracts due to synergistic action among their constituents. Emulsion-based encapsulation is considered as one of the most promising for the protection and delivery of polyphenols because relatively high encapsulation efficiency, stability and effective controlled release can be achieved under certain conditions.
Blueberry pomace is a rich source of high-value bioactive polyphenols with presumed health benefits. Their incorporation into functional foods and health-related products benefits from coencapsulation and protection of polyphenol-rich extracts in suitable carriers. This study aimed to create a water-in-oil-in-water (W1/O/W2) double emulsion system suitable for the coencapsulation of total phenolics (TP) and anthocyanins (TA) from a polyphenol-rich extract of blueberry pomace (W1). The effect of critical physical parameters for preparing stable double emulsions, namely homogenization pressure, stirring speed and time, was investigated by measuring the hydrodynamic diameter, size dispersity and zeta potential of the oil droplets, and the encapsulation efficiency of TP and TA. The oil droplets were negatively charged (negative zeta potential values), which was related to the pH and composition ofW2 (whey protein isolate solution) and suggests stabilization by the charged whey proteins. Increasing W1/O/W2 microfluidization pressure from 50 to 200 MPa or homogenization speed from 6000 to 12,000 rpm significantly increased droplet diameter and zeta potential and decreased TA and TP encapsulation efficiency. Increasing W1/O/W2homogenization time from 15 to 20 min also increased droplet diameter and zeta potential and lowered TA encapsulation efficiency, while TP encapsulation did not vary significantly. In contrast, increasing W1/O homogenization time from 5 to 10 min at 10,000 rpm markedly increased TA encapsulation efficiency and reduced droplet diameter and zeta potential. High coencapsulation rates of blueberry polyphenols and anthocyanins around 80% or greater were achieved when the oil droplets were relatively small (mean diameter < 400 nm), with low dispersity (<0.25) and a high negative surface charge (-40 mV or less). These characteristics were obtained by homogenizing for 10 min at 10,000 rpm (W1/O), then 6000 rpm for 15 min, followed by microfluidization at 50 MPa.