Chemistry Reference
In-Depth Information
with gastric juice and this reduces the satiation potentially provided by
a thickened liquid.
A number of attempts have been made to model the behaviour of
the human stomach (Wickham
et al
., 2009). These models are based
on mixed tanks, which are run in sequence to mimic the behaviour of
different parts of the stomach, i.e. the upper stomach, the lower stomach
and even the small intestine. However, the approach has been used to
investigate the digestive process and to a large extent to ignore the impact
that food structure has on the flow and mixing behaviour, which would
be observed in the real human stomach. These models do help from a
nutritional aspect, including the molecular breakdown of components,
but for the food engineer, there really needs to be further investigation
to help design food material properties, including rheology for specific
behaviour in the human GI tract.
Many people (de Wijk
et al
., 2008) have studied the effect of viscosity
on the eating frequency of foods. In addition, they have investigated
energy (sugar) update changes as a consequence of the meal viscosity
(Spiller, 1994).
Other investigations (Marciani
et al
., 1998a, 1998b) have attempted to
study food inside people using MRI. These researchers have investigated
the effect of viscosity on gastric emptying and their results have shown
only a slight effect for changes in viscosity to levels that are unpalatable.
So far the effect of increasing the viscosity of a food has not resulted
in changes on satiety in the range required to have a significant effect
on dietary intake of food. So if control is to be obtained, then we need
to have a rheological control beyond viscosity. This has introduced the
idea of self-structuring systems discussed in detail later.
10.2.3
Food in the intestine
Studies in the intestine are very difficult and until recently have received
virtually no attention at all for the healthy human.
In order to build a model of the human intestine, one would need
to consider mass transfer, mixing and molecular degradation. A model
intestine (Fig. 10.6) has been developed to study the chemical engineer-
ing aspects of the process (Thakaran
et al
., 2007). The machine has
two cuffs that can be inflated either together or independently. These
are designed to give the pulse flow, which is present within the human
intestine. The extent of squeezing and timescale for the pulses can be
varied.
The other part of the design is to have a semi-permeable membrane
as an inner tube, which is then enclosed in a non-permeable membrane
as the outer wall. This allows the transport of material to be measured
