Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
11.2.2 POLYSACCHARIDES
The function of polysaccharides in foodstuffs generally originates from chain
entanglement, formation of junction zones between the ordered polysaccharide
chains, and subsequent aggregation. 3,4 These effects are essentially governed by
molecular properties (e.g., molecular weight, degree of branching, chain rigidity,
and functional groups) of polysaccharides 35 and such factors as the concentration
and variety of the polysaccharides and the presence of biopolymers (e.g., proteins),
sugars, or salts.
Table 11.2 lists key functions of polysaccharides. Generally, native and modified
starches provide the widest variety of functions among food polysaccharides due
to variations in their amylose content, molecular and granular structure, and physicochemical
state. Therefore, they are not mentioned again in the following descriptions.
Typical gelling agents from agar and alginate to carrageenans (CAR, especially
κ- and ι-type) and pectins exhibit gel characteristics from a hard and brittle
texture with high syneresis potential to a soft, elastic, and cohesive texture with
insignificant syneresis. 2 Alginate and carrageenans can also be used as thickening,
suspending, and stabilizing agents in diverse foodstuffs, by adjusting their concentrations
and selecting proper cations in the systems. 31,38 Most of the commonly used
thickening agents — guar gum (GG), locust bean gum (LBG), CAR, carboxymethyl
cellulose (CMC), and xanthan gum (XG) — are also good at suspension, and
stabilization and crystallization inhibition, partially due to their branched structures
(for GG, LBG, and XG), 33 extended rigid chains (for CMC and XG), 35 or polyelectrolyte
nature (for CAR, CMC, and XG). Gum arabic, starch (often used to reduce
cost), and starch hydrolyzates (used as encapsulation aids) 23 are the best choices
for emulsification and flavor encapsulation. 34 Polysaccharides with a cellulose
backbone [i.e., β-(1→4)-D-glucan, found in XG, CMC, methyl cellulose (MC),
hydroxypropylmethyl cellulose (HPMC), and microcrystalline cellulose (MCC)]
usually have higher resistances to shear, temperature, and drastic pH change than
do other polysaccharides. 42,44 They are therefore suitable for preparation of foods
such as emulsions, salad dressings, and sauces. Because of their hydrophobicity,
these nonanionic cellulose derivatives exhibit anticaking and bulking properties. In
various foods, they act as fat mimetics. They are also binding agents in tablets. 41
Bulking agents and fat mimetics can be roughly grouped into water-soluble dietary
fiber (psyllium, inulins, and β-glucans from oat bran) and insoluble dietary fiber
[MCC, hemicelluloses, tamarind seed xyloglucan (TSX), wheat β-glucans, and
partially resistant starch and konjac flour]. Their key functions are revealed when
they are dispersed or they form microparticulate gels. 56,57,59,60 In fabricated or lowcalorie
products, they provide a fat-like texture and creamy appearance. Among
the anionic polysaccharides that have considerable potential to interact with proteins,
CMC, pectin, alginate and propylene glycol alginate (PGA) can be used to
coat the surface of fresh meat products. CAR and alginate are superior in binding
processed meat products. Biodelivery hydrogels can be easily prepared from alginate
or chitosan solutions because of their calcium-ion-mediated 36,37 or alkalinepH-induced
66 gelation, respectively.