Resumen de Stability assessment of emulsions treated by ultra-high pressure homogenization and their incorporation in a uht milk-based product for delivery of conjugated linoleic acid
Research on delivery of bioactive compounds by emulsion-based systems has increased over the last 10 years. Conventional oil-in-water emulsions (>1 µm) have poor physicochemical and oxidative stability; therefore, many efforts on novel technologies development have been employed to overcome this problem. Ultra-High Pressure Homogenization (UHPH) technology has been applied in different food emulsions in order to improve their physical stability. For these reasons, development of UHPH oil-in-water emulsions containing lipophilic bioactives, such as conjugated linoleic acid (CLA), to improve their physicochemical and nutritional characteristics and shelf-life is needed.
In this thesis dissertation, the influence of different technologies (UHPH and Conventional Homogenization; CH) and ingredients (soy protein isolate, SPI; pea protein isolate, PPI; soybean oil and CLA) in oil-in-water emulsions was evaluated. In addition, a final UHT milk-based product containing CLA-emulsions was developed.
This research has been divided into four parts. The first part studied the effect of UHPH (100-300 MPa, Ti=20 °C) compared to CH (15 MPa, Ti=20 °C) on physical and oxidative stability of soybean oil (10 and 20%) emulsions stabilized by SPI was assessed in order to determine the most stable formulations. Also, complete denaturation of SPI (95 °C, 15 min) before CH treatment was performed with the aim of analyzing possible improvement of emulsion characteristics. Particularly, UHPH emulsions treated at 100 and 200 MPa with 20% of oil were the most physically and oxidatively stable due to low particle size values, higher amount of oil, and greater viscosity and protein surface load at the interface. The heating of SPI did not improve physical stability of emulsions but enhanced oxidative stability when 10% oil was used.
The second study consisted in the assessment of different emulsions (20% oil) stabilized by SPI and PPI and homogenized by CH (55 MPa, Ti=20 °C) for 1 and 5 passes on the efficiency of 6% CLA encapsulation, its release and bioefficacy using in vitro digestion and a Caco-2 intestinal cell absorption model. All emulsions protected the encapsulated CLA better than the non-emulsified control in which CLA was oxidized during storage, as well as after in vitro digestion and delivery in Caco-2 cells. Similar percentages of CLA bioavailability were found for all emulsion treatments.
To evaluate the effect of UHPH (200 MPa, Ti=20 °C) in CLA-emulsions in comparison to CH (15 MPa, Ti=20 °C), a third study was performed. For another batch of CH emulsions, a heat treatment was also conducted applying a pasteurization treatment. UHPH produced a sterile CLA-emulsion and showed better physical stability during storage compared to other treatments, maintaining an optimal oxidative stability. Again, similar percentages of CLA bioavailability in Caco-2 cells were found for all emulsion treatments.
In the last study, the incorporation of CLA-emulsions obtained by UHPH (200 MPa, Ti=20 °C) and CH (15 MPa, Ti=20 °C) in a UHT milk-based product was evaluated. The final product containing the UHPH emulsions showed enhanced physicochemical stability and sensory properties during 4 months of storage.
