150
FREEZE—DRYÏNG
,
‘
factors may be the appearance, consistency, colour, avour, aroma, and nutritiVe…value
of the product». A part of this quality changes can only be determined organoleptically;
in‘some cases objective methods can be used, e.g. for determination of consistency and
colour changes or for measuring some factorsindicating the change in nutritive
like Vitamin C,…etc; But even in such cases, in which it is possible to apply an objective;
-
method 'àcorœlationbetween the numericalvalues measured by such a method and some
'3
important quality factor must exist and be known; this means that such a correlation must,
be determined experimentally.
«
"
,?
As an example it may be mentioned that the colour of
coloured fruits or—
; ‘ 5—
vegetables (like peas or tomatoes) can be used as an indicator for the state of maturity
_ÏË
of the produce. The measurement and the control of a device grading the produce into
single groups according to their maturity is done by a photo cell; but the colour limits
‘ 7
_
for the single grades must be determined by cOmpason of quality of the specic produce——
depending on maturity—applying a sensor analysis or organoleptically.
“Fo‘r
organoleptiCal properties the expressi0ns like excellent, very
fair,_acçèptable, poor, etc.‘ Can be used, which quantitatively describe the specic
quality
mind
sometimes gures are applied—because of their convenience in
writing,
called
Ïarein general used. We, in Karlsruhe, apply a numericalsystem, inWhidh the number 10
to excellent; 8 to g00d; 6 to fair, 4 to acceptable _or satisfactory,‘ 2 to bad and 0 to spôiled.«‘ The‘se gures can be usedfor description
of any quality factor‘and therefore‘can Serve as descriptiVe criteria of stability offrozen foods.
It mu3t be mentioned
more that the détériniiiationbf quality of a frozen product
can only be done after its thaWing; therefore, the ”changes occurring during freezing are
always determined together with the thawing changes. This again leads to the conclusion
that the method Of
may inuence the result of "quality assessment, and that
we Should when making Comparison tests
careful in applying
and optimal
‘
thaWirig conditions, which have to be kn0wn;
‘
‘
°
,
‘
‘
It Should be remembered that
of the single criteria of the stability may
be very di‘ei‘ent for di‘erent pr0ducts; In Some cases the
quality “characteristic
may be the cQnsistehcy
e.g._ for cucumber, *tomatoe‘s
products it may 1??? the aÿdür-like rancidit‘y', wh1ch’aôts
the limiting factor”
the
stcrage‘ time.
"
f
‘
‘
‘
‘
‘
*
"
,
fdodsl..… ! Îf}
:
.
.
Ÿ
Ï
:
ÿ
Ï
As already mentioned, the following factors Will affect the stability of the frozen
'v
«
‘:
,
Î
It has been shown‘that with few exceptions all f00dstu‘s can béfrozeii with good results.
_
Between the different products of animal origin there are onl‘yïsmall differences in the
héhaviour‘ during
intheir
But with fruits and‘vegetables eventhe“Væetyis most of a greâtaïhïponâcëf:?
produce may, show
'
a
for freezing;
often new varieties
grown
satisfy thefreezing requirements to the
to be frozen. One knows 5sbmë”?
factors}: affecting
stlunknownwhat1tsrealreason1s
Theotherfactor afèèingzthe
îthe
_—
‘
FREEZE—DRYÏNG
,
‘
factors may be the appearance, consistency, colour, avour, aroma, and nutritiVe…value
of the product». A part of this quality changes can only be determined organoleptically;
in‘some cases objective methods can be used, e.g. for determination of consistency and
colour changes or for measuring some factorsindicating the change in nutritive
like Vitamin C,…etc; But even in such cases, in which it is possible to apply an objective;
-
method 'àcorœlationbetween the numericalvalues measured by such a method and some
'3
important quality factor must exist and be known; this means that such a correlation must,
be determined experimentally.
«
"
,?
As an example it may be mentioned that the colour of
coloured fruits or—
; ‘ 5—
vegetables (like peas or tomatoes) can be used as an indicator for the state of maturity
_ÏË
of the produce. The measurement and the control of a device grading the produce into
single groups according to their maturity is done by a photo cell; but the colour limits
‘ 7
_
for the single grades must be determined by cOmpason of quality of the specic produce——
depending on maturity—applying a sensor analysis or organoleptically.
“Fo‘r
organoleptiCal properties the expressi0ns like excellent, very
fair,_acçèptable, poor, etc.‘ Can be used, which quantitatively describe the specic
quality
mind
sometimes gures are applied—because of their convenience in
writing,
called
Ïarein general used. We, in Karlsruhe, apply a numericalsystem, inWhidh the number 10
to excellent; 8 to g00d; 6 to fair, 4 to acceptable _or satisfactory,‘ 2 to bad and 0 to spôiled.«‘ The‘se gures can be usedfor description
of any quality factor‘and therefore‘can Serve as descriptiVe criteria of stability offrozen foods.
It mu3t be mentioned
more that the détériniiiationbf quality of a frozen product
can only be done after its thaWing; therefore, the ”changes occurring during freezing are
always determined together with the thawing changes. This again leads to the conclusion
that the method Of
may inuence the result of "quality assessment, and that
we Should when making Comparison tests
careful in applying
and optimal
‘
thaWirig conditions, which have to be kn0wn;
‘
‘
°
,
‘
‘
It Should be remembered that
of the single criteria of the stability may
be very di‘ei‘ent for di‘erent pr0ducts; In Some cases the
quality “characteristic
may be the cQnsistehcy
e.g._ for cucumber, *tomatoe‘s
products it may 1??? the aÿdür-like rancidit‘y', wh1ch’aôts
the limiting factor”
the
stcrage‘ time.
"
f
‘
‘
‘
‘
‘
*
"
,
fdodsl..… ! Îf}
:
.
.
Ÿ
Ï
:
ÿ
Ï
As already mentioned, the following factors Will affect the stability of the frozen
'v
«
‘:
,
Î
It has been shown‘that with few exceptions all f00dstu‘s can béfrozeii with good results.
_
Between the different products of animal origin there are onl‘yïsmall differences in the
héhaviour‘ during
intheir
But with fruits and‘vegetables eventhe“Væetyis most of a greâtaïhïponâcëf:?
produce may, show
'
a
for freezing;
often new varieties
grown
satisfy thefreezing requirements to the
to be frozen. One knows 5sbmë”?
factors}: affecting
stlunknownwhat1tsrealreason1s
Theotherfactor afèèingzthe
îthe
_—
‘