Self-Assembly in Food – A New Way to Make Nutritious Products - Food Colloids: Self-Assembly and Material Science - page 20

body'. It is divided into regions that specialize in the separate processes of
digestion, nutrient absorption and waste elimination: the mouth, the pharynx,
the oesophagus, the stomach, the small and large intestine, and the rectum. The
digestive system can therefore be seen as the gatekeeper, controlling what is
allowed to get into the body and what is kept out.
As a consequence we need to see food development in a broader context.
Food scientists will have to provide food products adapted to the physiolog-
ical, physico-chemical and colloidal processes involved in perception, as well
as nutrient transformation, liberation and absorption during digestion. 15 In
other words, it will be important to master the kinetics and thermodynamics
of nutrient incorporation into a food product, liberation during digestion and
absorption into the cells, making use of food structures that facilitate the
realization of the desired nutritional benefits. It is worthwhile to learn from
past experience of food drug interactions, which represent a similar context
to that mentioned above. Food drug interactions can lead either to improve-
ment of drug absorption or to treatment failure; they may even provoke
serious toxicity. 16,17 The most important pharmacokinetic effects of
food drug interactions are caused by changes in drug absorption due to
physico-chemical interactions (e.g., chelation) between the drug and certain
food components, and physiological responses such as changes in gastric
acidity, bile secretion or gastrointestinal motility. 18 Effects of foods on drug
absorption can be classified in terms of those causing decreased, delayed,
increased or accelerated absorption, and those where the food has no signi-
ficant effect. It has been shown 19 that negative food effects can be influenced
by adapting the pharmaceutical formulation. Furthermore, food drug inter-
actions typically depend on the size and composition of the meal, as well as
the exact timing of drug intake in relation to eating. Bioavailability of
lipophilic drugs is often increased by a high fat content, either due to an
increase in drug solubility or stimulation of bile secretion. A high fibre content
can reduce bioavailability of some drugs (e.g., digoxin) because of drug
binding to the fibre. The complexity in foods with built-in health benefits
will be even greater, where the food itself will take over the place of the
pharmaceutical formulation. Instead of seeing it from the negative side, we
can explore the different 'kinetic' effects on nutrient uptake - i.e.,reducingit
('keep something out'), sustaining it (slow release), increasing it (better

utilization) or accelerating it ('getting a boost').
Of particular interest is the question as to how the dynamics of nutrient uptake
is influenced by food structure and composition, e.g., microstructural features
such as particle size and shape, self-assembled structures and molecular structure.
Figure 1 illustrates the complexity existing in foods in the form of a phase
diagram. The macronutrients (carbohydrates, proteins and lipids) determine the
dry matter of any food. Adding water to each binary composition will determine
the phase behaviour in systems of lipid + protein + water, carbohydrate +
protein+water and lipid+ carbohydrate +water. These ternary systems can be
used as a guide to get a better insight into the complexity of structure formation
in complex foods. Of special interest to us is the spontaneous formation of