Chemistry Reference
In-Depth Information
which converted the M blocks into MGM blocks with no effect on
G blocks. The solubility and gelling kinetics at low pH were then
analysed in the epimerised polymers produced. It was found that the
gelling of the MG-rich alginate with acid is kinetically slower com-
pared with native alginates. This is thought to occur due to the al-
ternating axial-equatorial/equatorial-axial glycosidic linkages, which
generates a delay in the sol/gel transition compared to the di-equatorial
(poly-M) and di-axial (poly-G) sequences (Draget
et al.
, 2006a). These
findings highlight the potential of using epimerases to regulate algi-
nate gelling kinetics by simply controlling the fraction of MG se-
quences in the polymer chain. The ability to produce tailor-made al-
ginate provides a platform for the development of intelligently designed
high-value applications of alginate in food, pharma and biotechnology
sectors.
The remainder of this chapter will focus on summarising the various
applications of alginates in food systems and how the structural aspects
discussed above are used to develop and produce improved products.
6.6
ALGINATES AS FOOD ADDITIVE
Alginates are safe and approved as food additives by the European
Community and by the U.S. Food and Drug Administration and listed
in the United Nations (FAO/WHO) Codex Alimentarius (Draget
et al.
,
2006b). As a food additive, alginates are commonly referred to
within the European Union by the following E numbers (Brownlee
et al.
, 2009):
E400:
alginic acid;
E401-E404:
sodium, potassium, ammonium and calcium salts,
respectively;
E405:
esters of alginic acids, PGAs.
Alginates are routinely used in foods to improve, change, and stabilise
texture by exploiting properties such as gelation, viscosity enhance-
ment and stabilisation of aqueous mixtures, dispersions and emulsions
(Draget, 2000, 2006b). Some of these enhancements originate from the
native physical properties of alginates themselves, as summarised above,
but some of these properties result from interactions with other compo-
nents of the food product, for example, proteins, fat, or fibre. In addition
to these routine applications, alginates have more recently been utilised
as encapsulating vehicles for controlled release, edible films and as a
functional food ingredient. Key functions of alginate in various foods
are listed in Table 6.1.
