mam ANALYSIS
19
% zoox
:
f
‘
°
.
…
100K
.
Ê
5
=
2
;
3 …,
-.
‘“
…
v100
-90
-IO
-7
-6°
-40
—30
-20
40
0
TEMPEBAÏUHE
°c
FIGURE 8. Thermal analysis of 1 % methyl cellulose in 0.9 % sodium chloride, showing recrystallisation and
the saline eutectic.
without any additive.
Further work with this yeast was then directed in an effort to
study the thermal characteristics of the internal contents of the yeast cell.
The disintegrated mass obtained by disintegrating a large sample of yeast cells in the
“X-Freeze Press” as designed by Edebo (1961) was used to dilute a 8.5 % saline solution to
give a nal concentration of 0.85 % saline. The result of differential thermal analysis and
electrical conductivity measurements showed that the intracellular content of the yeast
cell behaved in a similar manner to that of the various additives examined and described
previously (gure 7).
This suggested that there was a protective substance within the
yeast cell which was able to form a glass—type structure on slow freezing. From a knowledge of the results obtained by Mazur (1960) using a fast freeze, it was suspected that
such a fast freeze may produce a metastable glass which would recrystallise on thawing;
this, however, was undetectable in the experiments carried out. In comparison, a suspension of the bacterium Streptococcus faecalis in 0.9 % saline failed to mask the saline eutectic
and to prevent supercooling. The fact that such an organism can be considered to be
frost resistant in comparison with the yeast, suggests that it may owe some of its resistance to the structure of the cell wall which had been ruptured for this particular study.
Thermal analysis has found tremendous application in predicting optimum thermal treat—
ment and drying temperatures in the freeze—drying of labile products, together With 1ts
role in examining the eect of protective additives on salt concentration and me crystal—
lisation as previously discussed.
The results obtained with suspensions of 11v1ng cells,
however, suggest that this technique may prove to be of even further value m elucrdatmg
the reasons why some cells appear to be naturally resistant to freezmg damage.
19
% zoox
:
f
‘
°
.
…
100K
.
Ê
5
=
2
;
3 …,
-.
‘“
…
v100
-90
-IO
-7
-6°
-40
—30
-20
40
0
TEMPEBAÏUHE
°c
FIGURE 8. Thermal analysis of 1 % methyl cellulose in 0.9 % sodium chloride, showing recrystallisation and
the saline eutectic.
without any additive.
Further work with this yeast was then directed in an effort to
study the thermal characteristics of the internal contents of the yeast cell.
The disintegrated mass obtained by disintegrating a large sample of yeast cells in the
“X-Freeze Press” as designed by Edebo (1961) was used to dilute a 8.5 % saline solution to
give a nal concentration of 0.85 % saline. The result of differential thermal analysis and
electrical conductivity measurements showed that the intracellular content of the yeast
cell behaved in a similar manner to that of the various additives examined and described
previously (gure 7).
This suggested that there was a protective substance within the
yeast cell which was able to form a glass—type structure on slow freezing. From a knowledge of the results obtained by Mazur (1960) using a fast freeze, it was suspected that
such a fast freeze may produce a metastable glass which would recrystallise on thawing;
this, however, was undetectable in the experiments carried out. In comparison, a suspension of the bacterium Streptococcus faecalis in 0.9 % saline failed to mask the saline eutectic
and to prevent supercooling. The fact that such an organism can be considered to be
frost resistant in comparison with the yeast, suggests that it may owe some of its resistance to the structure of the cell wall which had been ruptured for this particular study.
Thermal analysis has found tremendous application in predicting optimum thermal treat—
ment and drying temperatures in the freeze—drying of labile products, together With 1ts
role in examining the eect of protective additives on salt concentration and me crystal—
lisation as previously discussed.
The results obtained with suspensions of 11v1ng cells,
however, suggest that this technique may prove to be of even further value m elucrdatmg
the reasons why some cells appear to be naturally resistant to freezmg damage.