The technological steps involved in granular sturgeon
caviar production were discussed in previous chapters. This chapter
offers a condensed summary of processing granular caviar and information
on pressed sturgeon caviar which is very popular in Russia but
less known in the rest of the world. Granular sturgeon caviar
is marketed as fresh (non-pasteurized), pasteurized, chemically
preserved and pressed. Precut pieces in 10-15 cm salted and unscreened
ovaries are not considered (according to our definition in the
for-ward), a caviar type product. It is called 'yastichnay a ikra'
and is processed mainly from immature and fat ovaries. The product
is salted in hot brine and dried.
Pressed caviar can be considered a caviar type product
because it is processed from screened ovaries. The Russian term
for pressed caviar is 'payusnaya ikra'. A pressed caviar processing
diagram is given in Figure 8-9.
PRESSED STURGEON CAVIAR
Screened eggs with very weak membranes are utilized
to produce pressed caviar. These eggs are unfit for processing
into granular caviar. Pressed caviar is produced in two grades.
To obtain a first grade pressed caviar, the eggs should not have
noticeable smell or off-taste.
For a second grade pressed caviar, a 'muddy' or
'grassy' aftertaste is acceptable. Pressed caviar can be processed
from a mixture of eggs of all species and sizes. As opposed to
granular caviar, which is dry salted, eggs for pressed caviar
are salted in warm saturated brine of the highest quality at temperatures
38 to 45°C. The egg-brine ratio is 1:5. Salt-ing lasts 60
to 120 seconds with intensive agitating. In producing pressed
caviar, brine quality is of paramount importance. Because of the
quality of the eggs used the brine is soiled rapidly and as a
rule cannot be reused. Salting is stopped as soon as the egg inte-rior
liquid is coagulated and becomes dense. After draining for 4-5
minutes the eggs are placed in linen bags and immediately placed
under a press.
Pressing is performed using all kinds of manual presses. Historically
lever-type presses were used, currently screw type presses. The
caviar mass is still warm when pressed.
Pressing lasts from 5-8 minutes depending on the
pressed mass size, egg quality and de-sired product dryness. Usually
pressing stops when a yellowish, thick, fatty emulsion is starting
to seep through the linen. Weight losses while pressing may range
from 20-30%. Moisture content in pressed caviar is 37-40%, salinity
3.5 to 7%. After pressing the caviar mass is cooled down for about
15-20 minutes and then gently mixed to ho-mogenize the salt content,
which may differ across the mass in the linen bag (inner lay-ers
retain more moisture and salt).
Pressed caviar is packaged in tins and kegs. While
filling containers, special care is taken to eliminate any air
cavities by gently pressing the product which is then shaped by
the form of the container into a single 'cake'. The product is
spreadable or sliceable (Figure 8-10). It is stored frozen.
Pressed Sturgeon Caviar
Granular sturgeon caviar is processed from fresh
and mature ovaries, extracted from living fish, which are stunned
by clubbing and bled. If there is no opportunity to deliver the
fish alive to the processing plant, or the fish died in the fishing
process, ovaries are extracted at the fishing grounds and graded.
Ovaries suitable for granular caviar are immediately screened,
kept and transported at 0°C to the processing plant for salting.
A sturgeon caviar processing diagram is shown on Figure 8-11.
GRANULAR STURGEON CAVIAR PROCESSING
Before cutting the fish the belly is washed with
potable water using a brush. The cut starts 2-3 cm from the anal
vent towards the head. The ovaries should not be damaged while
cut-ting. Belly flaps are then folded aside and the ovaries are
carefully detached, one at a time, so blood does not contaminate
them. Only then is the fish passed on to another room for gut
cleaning and butchering. Grading by species and quality follows.
Roe which are not fit to process into granular caviar are put
aside and salted as whole ovaries. Manual screening takes place
into separate vats for each specimen. Each fish, and accordingly
each caviar lot, is registered under a separate number. Screened
eggs are rinsed and agitated in cold (0 to 8°C) potable water,
floating debris is decanted. Egg-water ratio while rinsing is
1:1.5. Rinsing could be repeated twice if necessary, however the
total rinsing time should not ex-ceed 30 seconds. Rinsed eggs
are dumped over a screen for dewatering.
If salting is delayed, screened and rinsed eggs
are stored at 0°C. Screened eggs are graded by colour, egg
size, and taste. When applicable, (see Table 6-1) several lots
are mixed. Usually, only the residuals of a lot-which can not
be accommodated in one package (say, a 1.8 kg can) are designated
Batches of eggs and salt-preservative mix are weighed.
The amount of salt is 3.5 to 5.0% of egg weight. The exact percentage
depends on egg quality and desired final product sa-linity. The
mix is introduced through a sieve evenly over the egg surface
in the vat. Batch size is 5-15 kg. Salting lasts 2-4 minutes.
Manual salting is terminated when the egg mass becomes reasonably
viscous, and thin whitish strips are appearing on the surface
of the egg. If salting time is not sufficient the egg interior
is watery. If eggs are salted for too long the surrounding brine
becomes so thick that it would be impossible to drain it off.
This thick juice will result in lumping of the eggs. Such caviar
is 'overdone' and eggs do not separate easily. There are modern
mechanized salting devices which stir and simulta-neously dewater
The final salinity is affected by the intensity
of brine uptake during draining, which fol-lows salting. To enhance
dewatering salted eggs are placed over the screen in a thin layer
and the screen is frequently shaken. The drained off brine reduces
considerably the final product salinity and preservative concentration
vs the initial concentration of these sub-stances.
Filling of eggs into containers should start before
the eggs swell by absorbing the sur-rounding brine. Swelling of
the eggs into round balls should take place inside the con-tainer.
This is especially true for the large 0.6 and 1.8 kg cans, because,
draining off the excess brine and settling of the lid will provide
for an air tight package.
Filling into large cans is done manually. Caviar
is filled 10-20 mm higher than the rim. The lid is then placed
so that the seams of the lid and container body match. Cans are
then held on the side to drain off excessive brine and further
put under pressure (weights or press). The lid slips down and
air tightness is secured by a rubber band. Before put-ting on
the band, the lids are tightly pushed down, and the absence of
air cavities under the lid is checked. A traditional way of doing
it is by tapping lightly all over the lid and listening to the
sound. A dull sound is a sign that there is no air left. Finally
the cans are wiped clean, put in fabric bags and boxed in plywood
Filling, vacuum, closing, and pasteurization of glass jars are
executed on automated lines. Sturgeon caviar of different types
is shown on Figure 8-12.
FIGURE 8-12: Sturgeon Caviar