>f—
Preservation and stability
of frozen foods
J. KUPRIANOFF
-
PROFESSOR Dr., DŒEKTOR DER BWDESFORSCHÜNGSANSTÀLT FÜR LEBENSMI'ITELÈRISCŒAL‘I‘UNG
KARLSRUHE
1. INTRODUCTION
_
‘
'
.
,
«
The freezing of foodstus is a widely commercially applied method for long term preser—
vation of perishable foodstuffs. Its effect is principally based upon the following facts :
l. Lowering of the temperature leads to slowing down
chemical and biochemical
reactions, according to the van t’Ho"s law.
2. Complete inhibition of the growth of microorganisms by surpassing their temperature
range of multiplication.
’
_
3. Freezing out of water as solutes and eliminating in this way the uid phase in which
reactions and diusion of reacting substances and of their reaction produces can
.
easily take place.
'
_
4. Slowing down of all physical changes as evaporation or sublimation leading to smaller
weight loss.
'
’
As a result of these complex effect of the lowering of temperature down to the range
of — 18 to — 30 °C, which in principle minimizes all physical and chemical changes and
eliminates microbial alterations in the foodstu‘s, their adverse quality changes during
storage are sloWn down; this results in a very slow change in organoleptical properties—as
taste, odour and consistency—and in nutritive value
of adequately frozen and stored frozen
foods.
But it must be realized that even at the lowest commercially applied storage tempe—
rature of — 30 °C, some changes—depending on produce audits pretreatment—take place.
Because these changes are progressing with the storage time and also depend on the store
temperature, they are described—as it will be shown later—by the time-temperaturetolerance (T-T—T) of the specic food in mind.
_
_
The stability of frozen foods can be judged by the assessment of their quality
at the end
of the storage; this is usually done after thawing the frozen foods, sothat 1n pr1ncrple
Preservation and stability
of frozen foods
J. KUPRIANOFF
-
PROFESSOR Dr., DŒEKTOR DER BWDESFORSCHÜNGSANSTÀLT FÜR LEBENSMI'ITELÈRISCŒAL‘I‘UNG
KARLSRUHE
1. INTRODUCTION
_
‘
'
.
,
«
The freezing of foodstus is a widely commercially applied method for long term preser—
vation of perishable foodstuffs. Its effect is principally based upon the following facts :
l. Lowering of the temperature leads to slowing down
chemical and biochemical
reactions, according to the van t’Ho"s law.
2. Complete inhibition of the growth of microorganisms by surpassing their temperature
range of multiplication.
’
_
3. Freezing out of water as solutes and eliminating in this way the uid phase in which
reactions and diusion of reacting substances and of their reaction produces can
.
easily take place.
'
_
4. Slowing down of all physical changes as evaporation or sublimation leading to smaller
weight loss.
'
’
As a result of these complex effect of the lowering of temperature down to the range
of — 18 to — 30 °C, which in principle minimizes all physical and chemical changes and
eliminates microbial alterations in the foodstu‘s, their adverse quality changes during
storage are sloWn down; this results in a very slow change in organoleptical properties—as
taste, odour and consistency—and in nutritive value
of adequately frozen and stored frozen
foods.
But it must be realized that even at the lowest commercially applied storage tempe—
rature of — 30 °C, some changes—depending on produce audits pretreatment—take place.
Because these changes are progressing with the storage time and also depend on the store
temperature, they are described—as it will be shown later—by the time-temperaturetolerance (T-T—T) of the specic food in mind.
_
_
The stability of frozen foods can be judged by the assessment of their quality
at the end
of the storage; this is usually done after thawing the frozen foods, sothat 1n pr1ncrple