Chemistry Reference
In-Depth Information
and Blaauwhoed 2009), and compatibility with other components of the system such as starch and
other hydrocolloids (Giannouli et al. 2004). As previously stated, long-chain inulin appears to act
as a fat mimetic due to its ability to form microcrystals, which eventually may grow into a gel net-
work (Hébette et al. 1998). Only longer chains with DP > 10 participate in the gel formation, with
smaller chains remaining in the solution. The rate of crystallization, ultimate crystal size, and gel
irmness are governed by inulin concentration, DP, applied shear, and temperature (Bot et al. 2004;
Meyer and Blaauwhoed 2009). Due to lower solubility, longer chains will crystalyze at a greater
rate than the shorter ones (Zimeri and Kokini 2003). In the presence of other food ingredients,
inulin crystallization may be affected; they all compete for water and interact with each other
through weak molecular interactions. Thus, it is expected that the inal structure of the product will
also be affected. Inulin has been assessed in a number of different models. For example, Bishay
(1998) reported a synergistic effect between inulin and calcium alginate and a negative interaction
between inulin and starch. Zimeri and Kokini (2003) similarly reported that inulin interfered with
the network formation of starch acting as a diluent. There is less fundamental information avail-
able with regard to the rheological behavior of inulin in real food systems, but reports show that the
properties of the system are inluenced by the DP of inulin. For example, Shah et al. (2010) used
different types of inulin as bulking agents in the production of sucrose-free chocolate. One of the
observations was that the rate of chocolate tempering may be adjusted due to different viscoelastic
behaviors. The addition of inulin produced a substantially different trend of phase shift in compari-
son to control. Sucrose-free chocolate samples displayed two distinct peaks: the irst peak coincides
with the rewarming of sucrose-free chocolate, whereas the second appeared around 20°C during
the cooling phase. The increase of phase shift during the second step of tempering may indicate the
structural rearrangement of inulin chains due to molecular relaxation and greater viscous behavior
(Chiavaro et al. 2007). The second peak may be due to the repositioning of molten fat on the surface
of solidiied fat, which decreased friction between fat crystals and again improved viscous property
(Kloek et al. 2005).
Inulin is used either as a supplement to foods or as a macronutrient substitute in foods. As a
supplement to foods, it is added mainly for its nutritional properties. Such additions are usually in
the range of 3-6 g per portion, not exceeding 10 g. As a macronutrient substitute, it is used mainly
as a fat replacer. Typically, 1 g of fat is replaced by 0.25 g of inulin, which will lead to inulin con-
centrations of ~6 g per portion. Because inulin has been a natural component of many foods con-
sumed safely by humans over millennia, it is therefore generally recognized as safe (Coussement
1999). Inulin-type fructans are classiied as functional food ingredients. They are believed to target
gastrointestinal functions, and, also, most likely via their effects on the gut and the gut microlora,
systemic functions that are known to be related to health and well-being (Roberfroid 2005, 2007).
The potential nutritional and health beneits of this ingredient are summarized in Table 13.5. Inulin
and OF comply with most deinitions of DFs, and they are labeled as such due to their fermentation
pattern and selective stimulation of bacterial growth, inulin, and OF prebiotics.
A prebiotic is a nondigestible food ingredient that beneicially affects the host by selectively
stimulating the growth, activity, or both of one or a limited number of bacterial species already
resident in the colon (Ziemer and Gibson 1998). To exhibit such effects, a prebiotic must neither
be hydrolyzed nor absorbed in the upper part of the gastrointestinal tract and must be selective for
one or a limited number of potentially beneicial bacteria residing in the colon (Collins and Gibson
1999). The number of probiotics in the human gut tends to decrease with age (Mitsuoka 1992).
Two major strategies have been proposed to maintain a high level of probiotics to sustain beneicial
health effects: (1) continuous ingestion of probiotic-containing foods or (2) supplementation of food
with prebiotics (Gomes and Malcata 1999). Probiotics are deined as “live microorganisms that,
when administered in adequate amounts, confer a health beneit on the host” (Vasiljevic and Shah
2006, 2008). Over the years, many species of microorganisms have been identiied, scientiically
investigated, and commercially applied. They consist of not only lactic acid-producing bacteria
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