Simulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives that determine endpoints such as the bioaccessibility of nutrients and non-nutrients or the digestibility of macronutrients (e.g. lipids, proteins and carbohydrates) are used for screening and building new hypotheses. Various digestion models have been proposed, often impeding the possibility to compare results across research teams. For example, a large variety of enzymes from different sources such as of porcine, rabbit or human origin have been used, differing in their activity and characterization. Differences in pH, mineral type, ionic strength and digestion time, which alter enzyme activity and other phenomena, may also considerably alter results. Other parameters such as the presence of phospholipids, individual enzymes such as gastric lipase and digestive emulsifiers vs. their mixtures (e.g. pancreatin and bile salts), and the ratio of food bolus to digestive fluids, have also been discussed at length. In the present consensus paper, within the COST Infogest network, we propose a general standardised and practical static digestion method based on physiologically relevant conditions that can be applied for various endpoints, which may be amended to accommodate further specific requirements. A frameset of parameters including the oral, gastric and small intestinal digestion are outlined and their relevance discussed in relation to available in vivo data and enzymes. This consensus paper will give a detailed protocol and a line-by-line, guidance, recommendations and justifications but also limitation of the proposed model. This harmonised static, in vitro digestion method for food should aid the production of more comparable data in the future.

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A standardised static in vitro digestion method suitable for food – an international consensus

Nanoemulsions fabricated from food-grade ingredients are being increasingly utilized in the food industry to encapsulate, protect, and deliver lipophilic functional components, such as biologically-active lipids (e.g., ω-3 fatty acids, conjugated linoleic acid) and oil-soluble flavors, vitamins, preservatives, and nutraceuticals. The small size of the particles in nanoemulsions (r<100 nm) means that they have a number of potential advantages over conventional emulsions-higher stability to droplet aggregation and gravitational separation, high optical clarity, ability to modulate product texture, and, increased bioavailability of lipophilic components. On the other hand, there may also be some risks associated with the oral ingestion of nanoemulsions, such as their ability to change the biological fate of bioactive components within the gastrointestinal tract and the potential toxicity of some of the components used in their fabrication. This review article provides an overview of the current status of nanoemulsion formulation, fabrication, properties, applications, biological fate, and potential toxicity with emphasis on systems suitable for utilization within the food and beverage industry.

Food-grade nanoemulsions: formulation, fabrication, properties, performance, biological fate, and potential toxicity.

Hydrocolloids as emulsifiers and emulsion stabilizers

Recent advances in the stabilization of emulsions and foams by particles of nanoscale and microscopic dimensions are described. Ongoing research in this highly active field is providing insight into (i) the molecular factors controlling particle wettability and adsorption, (ii) the structural and mechanical properties of particle-laden liquid interfaces, and (ii) the stabilization mechanisms of particle-coated droplets and bubbles. There is much potential for exploiting the emerging knowledge in new food product applications. The preparation of cheap and effective colloidal particles based on food-grade ingredients, especially proteins, is the key technological challenge.

Food emulsions and foams: Stabilization by particles

Because of their perceived health benefits, probiotics have been incorporated into a range of dairy products, including yoghurts, soft-, semi-hard and hard cheeses, ice cream, milk powders and frozen dairy desserts. However, there are still several problems with respect to the low viability of probiotic bacteria in dairy foods. This review focuses mainly on current knowledge and techniques used in the microencapsulation of probiotic microorganisms to enhance their viability during fermentation, processing and utilization in commercial products. Microencapsulation of probiotic bacteria can be used to enhance the viability during processing, and also for the targeted delivery in gastrointestinal tract.

Recent advances in microencapsulation of probiotics for industrial applications and targeted delivery

Structuring food emulsions in the gastrointestinal tract to modify lipid digestion.

Summary
This article details recent research conducted on the complexation between milk proteins and polysaccharides and the properties of the complexes, and the application of such relationships to the food industry. Complexation between proteins and polysaccharides through electrostatic interactions gives either soluble complexes in a stable solution or insoluble complexes, leading to phase separation. The formation and the stability of these complexes are influenced by pH, ionic strength, ratio of protein to polysaccharide, charge density of protein and polysaccharide as well as processing conditions (temperature, shearing and time). The functional properties of milk proteins, such as solubility, surface activity, conformational stability, gel-forming ability, emulsifying properties and foaming properties, are improved through the formation of complexes with polysaccharides. These changes in the functional properties provide opportunities to create new ingredients for the food industry.

Complexation between milk proteins and polysaccharides via electrostatic interaction: principles and applications – a review

Characterization of protein components of natural and heat-treated milk fat globule membranes

The formation of electrostatic complexes between sodium caseinate and gum arabic (GA) was studied as a function of pH (2.0–7.0), using slow acidification in situ with glucono-δ-lactone (GDL) or titration with HCl. The colloidal behavior of the complexes under specific conditions was investigated using absorbance measurements (at 515 or 810 nm) and dynamic light scattering (DLS). In contrast to the sudden increase in absorbance and subsequent precipitation of sodium caseinate solutions at pH 50 mM NaCl). It is postulated that the structure of the nanoparticles comprises an aggregated caseinate core, protected from further aggregation by steric repulsion of one, or more, electrostatically attached GA molecules. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 121–133, 2006



This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

Formation of stable nanoparticles via electrostatic complexation between sodium caseinate and gum arabic.

During the last two decades, important insights into the physico-chemical properties of oil-in-water emulsions under various food-processing conditions have been gained. Much of this research has focused on understanding how the various types of proteins, in particular milk proteins, function as emulsifiers and stabilizers in food emulsions. Recently, attention has been given to understanding the behavior of emulsions during gastrointestinal digestion, using mainly in vitro models. These studies have provided useful information on how various types of emulsions behave in a wide range of physical (e.g. shear, temperature) and biochemical (e.g. dilution, pH, pepsin, pancreatin, mucins, bile salts) environments that are relevant to digestion. This knowledge may allow manipulation of the physico-chemical and interfacial properties to modulate lipid ingestion and to improve the bioavailability of lipid-soluble nutrients. However, many of these findings will need to be validated in in vivo models and human clinical trials. Limited studies in humans have shown that the extent and the duration of postprandial lipemia are positively related to the pathogenesis and progression of coronary heart disease. The rate of digestion of lipids also appears to be important in satiation and subsequent energy regulation.

Aiqian Ye

Papers

Structuring food emulsions in the gastrointestinal tract to modify lipid digestion.

Complexation between milk proteins and polysaccharides via electrostatic interaction: principles and applications – a review

Characterization of protein components of natural and heat-treated milk fat globule membranes

Formation of stable nanoparticles via electrostatic complexation between sodium caseinate and gum arabic.

Structural and biochemical factors affecting the digestion of protein-stabilized emulsions