Chemistry Reference
In-Depth Information
6
Alginates in Foods
Alan M. Smith and Taghi Miri
Alginate has been widely investigated since it was first isolated and
described in 1881 by Stanford (E.C.C Stanford, 1881) and has since
become a vastly utilised polymer with a variety of applications. Algi-
nate is exploited not only in the food industry, but also in the paper and
textile industries, and for pharmaceutical and, more recently, biomed-
ical applications. The versatility of alginate has led to it being a fairly
well-understood material and has been subject to a great number of
systematic rheological investigations, information from which has been
subsequently utilised in food applications. More recently, their 'high
value' pharmaceutical and biomedical applications have driven the de-
velopment and understanding of alginate further. This chapter intends
to provide a brief overview of the chemical properties of alginates and
to review the influence of molecular structure on the physical, func-
tional and, more specifically, rheological properties which are exploited
in food systems. Specific applications in foods are also covered, which
highlight the multi-functional nature of alginate and its future potential.
6.1
ALGINATE SOURCE AND MOLECULAR STRUCTURE
Alginate is the major structural component of brown seaweed (Phaeo-
phyceae), providing both mechanical strength and plasticity to seaweed
that is analogous to pectins in plants. There are different species of brown
seaweed that contain alginates; however, the species that are most com-
mercially exploited for alginate production are
Laminaria hyperborea,
Macrocystis pyrifera, Saccharina japonica
and
Ascophyllum nodosum
(Gomeza
et al.
, 2009), with an estimated annual industrial production of
30,000 metric tonnes (Draget
et al.
, 2006b). Alginate composition and
hence physical properties vary depending on the area of the plant the al-
ginate is extracted from (Jothisaraswathi
et al.
, 2006). This can also vary
