MICROSCOPIC IMAGING OF NETWORK STRANDS IN AGAR, CARRAGEENAN, LOCUST BEAN GUM AND KAPPA-CARRAGEENAN LOCUST BEAN GUM GELS

The ultrasrructure of gels formed from agar, kappa carrageenan, iota c arrageenan, locust bean gum and mixtures of kappa carrageenan and locu st bean gum have been studied by fast-freeze deep-etch rotary-shadowed replica microscopy. The reproducibility of images obtained suggests t hat the technique is robust and preserves features of native network a rchitecture at the nanometre level. Agar gels show a range of strand t hicknesses, whereas kappa carrageenan has a more homogeneous structure . Iota carrageenan network strands are thinner than those in kappa car rageenan, but thicker than those in locust bean gum gels. Mixed gels o f kappa carrageenan and locust bean gum indicate thorough mixing and, therefore, no phase separation at the 10-100 nm level. Apparent binary polymer contacts are consistent with, but do not prove unequivocally, the presence of inter-polymer associations.