Mary Ann Augustin

Encapsulation of food ingredients

Microencapsulation is a relatively new technology that is used for protection, stabilization, and slow release of food ingredients. The encapsulating or wall materials used generally consist of starch, starch derivatives, proteins, gums, lipids, or any combination of them. Methods of encapsulation of food ingredients include spray-drying, freeze-drying, fluidized bed-coating, extrusion, cocrystallization, molecular inclusion, and coacervation. This paper reviews techniques for preparation of microencapsulated food ingredients and choices of coating material. Characterization of microcapsules, mechanisms of controlled release, and efficiency of protection/stabilization of encapsulated food ingredients are also presented.

Structure and visco-elastic properties of set yoghurt with altered casein to whey protein ratios

Abstract Set yoghurts with a consistent total protein content were manufactured from milks reconstituted from skim milk powder (SMP), or blends of SMP and whey protein concentrate (WPC) powders with crude protein concentrations between 25% and 80% (w/w) so that the casein to whey protein ratio varied from 4.7:1 to 0.5:1. As the casein to whey protein ratio was decreased the maximum gel strength of the yoghurt increased, the initial gradient of the force–distance curves generally decreased, whey drainage was reduced, and the gels were generally less viscous. Scanning electron microscopy indicated that gels with a lower proportion of casein had a finer structure with numerous small pores and a dense network of crosslinks. When the casein to whey protein ratio was maintained at a constant level, the physical properties of the gels were generally similar, regardless of the protein concentration of the WPC powder that was used. The relationship between the casein to whey protein ratio and the physical properties of the yoghurts is considered in terms of the microstructure of the protein network.

Microencapsulated Lactobacillus rhamnosus GG Powders: Relationship of Powder Physical Properties to Probiotic Survival during Storage

Freeze-dried commercial Lactobacillus rhamnosus GG (LGG) were encapsulated in an emulsion-based formulation stabilized by whey protein and resistant starch and either spray-dried or freeze-dried to produce probiotic microcapsules. There was no difference in loss of probiotics viability after spray drying or freeze drying. Particle size, morphology, moisture sorption, and water mobility of the powder microcapsules were examined. Particle size analysis and scanning electron microscopy showed that spray-dried LGG microcapsules (SDMC) were small spherical particles, whereas freeze-dried LGG microcapsules (FDMC) were larger nonspherical particles. Moisture sorption isotherms obtained using dynamic vapor sorption showed a slightly higher water uptake in spray-dried microcapsules. The effect of water mobility, as measured by nuclear magnetic resonance (NMR) spectroscopy, at various water activities (a(w) 0.32, 0.57, and 0.70) and probiotic viability during storage at 25 °C was also examined. Increasing the relative humidity of the environment at which the samples were stored caused an increase in water mobility and the rate of loss in viability. The viability data during storage indicated that SDMC had better storage stability compared to FDMC. Although more water was adsorbed for spray-dried than freeze-dried microcapsules, water mobility was similar for corresponding storage conditions because there was a stronger water-binding energy for spray-dried microcapsule. This possibly accounted for the improved survival of probiotics in spray-dried microcapsules.

Structural Rearrangement of β-Lactoglobulin at Different Oil–Water Interfaces and Its Effect on Emulsion Stability

Understanding the factors that control protein structure and stability at the oil-water interface continues to be a major focus to optimize the formulation of protein-stabilized emulsions. In this study, a combination of synchrotron radiation circular dichroism spectroscopy, front-face fluorescence spectroscopy, and dual polarization interferometry (DPI) was used to characterize the conformation and geometric structure of β-lactoglobulin (β-Lg) upon adsorption to two oil-water interfaces: a hexadecane-water interface and a tricaprylin-water interface. The results show that, upon adsorption to both oil-water interfaces, β-Lg went through a β-sheet to α-helix transition with a corresponding loss of its globular tertiary structure. The degree of conformational change was also a function of the oil phase polarity. The hexadecane oil induced a much higher degree of non-native α-helix compared to the tricaprylin oil. In contrast to the β-Lg conformation in solution, the non-native α-helical-rich conformation of β-Lg at the interface was resistant to further conformational change upon heating. DPI measurements suggest that β-Lg formed a thin dense layer at emulsion droplet surfaces. The effects of high temperature and the presence of salt on these β-Lg emulsions were then investigated by monitoring changes in the ζ-potential and particle size. In the absence of salt, high electrostatic repulsion meant β-Lg-stabilized emulsions were resistant to heating to 90 °C. Adding salt (120 mM NaCl) before or after heating led to emulsion flocculation due to the screening of the electrostatic repulsion between colloidal particles. This study has provided insight into the structural properties of proteins adsorbed at the oil-water interface and has implications in the formulation and production of emulsions stabilized by globular proteins.

Nano- and micro-encapsulated systems for enhancing the delivery of resveratrol

There has been interest in the use of trans‐resveratrol as a natural preventative agent for improving health and alleviating a range of diseases. However, resveratrol has low bioavailability, and this has been associated with its poor water solubility, its low stability against environmental stress, and its inability to reach a target site in the body to exert the desired health effect. Encapsulation offers a potential approach for enhancing the solubility of resveratrol, stabilizing it against trans‐to‐cis isomerization, and improving its bioavailability. A range of encapsulant materials, formulations, and technologies have been examined for enhancing the delivery of resveratrol. Research on the efficacy of encapsulated resveratrol formulations and relevant doses for specific applications is required before recommendations may be made for the use of these formulations for human health outcomes.

Enhanced creaming of milk fat globules in milk emulsions by the application of ultrasound and detection by means of optical methods

The effects of application of ultrasonic waves to recombined milk emulsions (3.5% fat, 7% total solids) and raw milk on fat destabilization and creaming were examined. Coarse and fine recombined emulsions (D[4,3]=9.3 μm and 2.7 μm, respectively) and raw milk (D[4,3]=4.9 μm) were subjected to ultrasound for 5 min at 35°C and 400 kHz or 1.6 MHz (using a single transducer) or 400 kHz (where the emulsion was sandwiched between two transducers). Creaming, as calculated from Turbiscan measurements, was more evident in the coarse recombined emulsion and raw milk compared to that of the recombined fine emulsion. Micrographs confirmed that there was flocculation and coalescence in creamed layer of emulsion. Coalescence was confirmed by particle size measurement. These results imply that ultrasound has potential to pre-dispose fat particles in milk emulsions to creaming in standing wave systems and in systems with inhomogeneous sound distributions.

Nanostructured materials in the food industry.

Nanotechnology involves the application, production, and processing of materials at the nanometer scale. Biological- and physical-inspired approaches, using both conventional and innovative food processing technologies to manipulate matter at this scale, provide the food industry with materials with new functionalities. Understanding the assembly behavior of native and modified food components is essential in developing nanostructured materials. Functionalized nanostructured materials are finding applications in many sectors of the food industry, including novel nanosensors, new packaging materials with improved mechanical and barrier properties, and efficient and targeted nutrient delivery systems. An improved understanding of the benefits and the risks of the technology based on sound scientific data will help gain the acceptance of nanotechnology by the food industry. New horizons for nanotechnology in food science may be achieved by further research on nanoscale structures and methods to control interactions between single molecules.

Binding of resveratrol with sodium caseinate in aqueous solutions

The interaction between resveratrol (Res) and sodium caseinate (Na-Cas) has been studied by measuring fluorescence quenching of the protein by resveratrol. Quenching constants were determined using Stern-Volmer equation, which suggests that both dynamic and static quenching occur between Na-Cas and Res. Binding constants for the complexation between Na-Cas and Res were determined at different temperatures. The large binding constants (3.7-5.1×10(5)M(-1)) suggest that Res has strong affinity for Na-Cas. This affinity decreases as the temperature is raised from 25 to 37°C. The binding involves both hydrogen bonding and hydrophobic interaction, as suggested by negative enthalpy change and positive entropy change for the binding reaction. The present study indicates that Na-Cas, a common food protein, may be used as a carrier of Res, a bioactive polyphenol which is insoluble in both water and oils.

Influence of processing on functionality of milk and dairy proteins.

The inherent physical functionality of dairy ingredients makes them useful in a range of food applications. These functionalities include their solubility, water binding, viscosity, gelation, heat stability, renneting, foaming, and emulsifying properties. The suitability of dairy ingredients for an application can be further tailored by altering the structure of the proteins using appropriate processes. The processes discussed include physical modification (heat treatment, acidification, addition of mineral slats, homogenization, and shear), enzymatic modification (renneting, hydrolysis, and transglutamination), and chemical modification (use of chemical agents and the Maillard reaction). Emerging food processes (high pressure and ultrasound) are also discussed. The challenges for using dairy ingredients for the delivery of nutrients and bioactive components, while maintaining physical functionality, are also highlighted. There is a need for continued research into the fundamental aspects of milk proteins and their responses to various stresses for further differentiation of milk products and for the delivery of ingredients with consistent quality for target applications.

Oxidative Stability of Microencapsulated Fish Oil Powders Stabilized by Blends of Chitosan, Modified Starch, and Glucose

Various indices of lipid oxidation were used to assess the oxidative stability of microencapsulated fish oil powders prepared from tuna oil-in-water emulsions (pH 4.9 or 6.0) containing chitosan, an emulsifying starch, and glucose. There were good agreements among the induction period for oxidation under accelerated conditions (80 degrees C, 5 bar oxygen), the development of oxidation volatile markers from fish oil (namely, propanal, 1-penten-3-ol, 1-penten-3-one, 2,4-(Z,E)-heptadienal, and 2,4-(E,E)-heptadienal), and the loss of eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) over four weeks of storage at 25 degrees C. All indices of oxidation showed that powders prepared from emulsions at pH 6.0 were more stable to oxidation than corresponding formulations at pH 4.9. It is suggested that the increased electrostatic interactions between the chitosan and emulsifying starch at the higher pH contributed to the increased stability of the microcapsule powders.