Characterization of protein gels by scanning and transmission electron microscopy : A methodology study of soy protein gels

• Different preparation techniques for scanning (SEM) and for transmission electron microscopy (TEM) were compared in order to characterize the structure of protein gels. SEM specimens were prepared by chemical fixation, dehydration, and critical-point drying. TEM specimens were prepared by using techniques of thin-sectioning and freeze-fracturing/etching. Thin sections were made after varying fixation and staining conditions. For freeze-fracturing/etching, the standard freezing procedure both using and omitting cryoprotectants (glycerol), as well as a particular modification of the "soil-emulsion" freezing technique without cryoprotective pretreatment were used. Finally, critical-point dried specimens (produced for SEM) were freeze-etched after infiltration with dioxane. The various techniques of preparation were applied to soy protein gels made in distilled water and in 0.2M NaCl under well defined conditions. The gel structures differed with regard to the state of aggregation which depended on the presence or absence of NaCl. The network structure was found to be of two levels. First, there was an orientation on the molecular level in the form of strands and fine ring structures. Second, there was a coarser network with voids of the magnitude of ?0.2 ?m. The pore size distribution of the latter network was found to be very sensitive to environmental factors such as low ionic strength and presence of cryoprotectants mainly due to swelling. The information obtained by the various techniques generally showed good agreement and were complementary. Distinct preparation artifacts caused by improper freezing or critical-point drying were also revealed. © 1981 Academic Press, Inc. All rights of reproduction in any form reserved.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Livsmedelsvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Food Science (hsv//eng)

Nyckelord

Food Engineering

Livsmedelsteknik

Publikations- och innehållstyp

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