The one step salting process (Figure 8-3) does not imply that dyeing
and retail packing must be followed immediately by screening i.e. as
in a conveyor type process. Screened lightly salted roe can still be
stored in bulk containers for a reasonable time if good stor-age conditions
are observed e.g. temperature 0 to - 3°C. The one step caviar technology
was the first one to be employed in the 1930's in Europe. But as the
supply of roe started to come from distant fishing areas the two step
technology became almost the only one to be used.
LUMPFISH CAVIAR PROCESSING
Iceland is now becoming the major "buyer' of its
own barrel packed roe, i.e. the lump-fish caviar industry is now emerging
closer to the fishing grounds. The next logical de-velopment would be
to return to the one step technology of processing low salted lump-fish
caviar without preliminary salting. There is no doubt about the superiority
of this product in taste, and appearance. Experiments by the Icelandic
Laboratories proved it. It is only a matter of time to
overcome the logistical difficulties involved: cooling capacities, quick
transportation to processing locations, dyeing and packaging equipment
installation. Such a change will certainly improve overall product quality
but will meet resistance from the traditional packers, located at the
However, there is not sufficient evidence that one step
technology as compared with the two step technology can produce, a caviar
of the same shelf-life. Prolonged storage of lumpfish caviar processed
in one step may result in colour deterioration because the pH of this
caviar is higher than the one processed in two steps. Better colour
fixation takes place at lower pH values (about pH 4). Changes in the
dyeing and colour fixation pro-cedures may be necessary.
Substantial lowering the pH by acidification (vinegar,
citric or ascorbic adds) can intro-duce undesirable sourness.
Figure 8-3 shows ways how the roe can be converted into
different marketable products. Some of the operations are optional,
the decision to skip particular operations is made by the processor
depending on concrete batch status. Highly salted lumpfish roe bulk
packages can be kept either chilled or frozen. Freezing is more expensive
and may result in excessive drip after thawing. Nevertheless this could
be considered when long term storage is needed. Low salted retail packages
are usually not frozen in the trade. Re-packing of bulk roe to meet
clients specification can be used to check and improve product quality
Usually mechanized screening of lumpfish ovaries takes
place. Mechanized screening lowers the yield and is not convenient for
frequent cleaning of the equipment. The screening machines used differ
in size and details of design. The most common have a horizontal shaft
and regulate debris removal. A typical machine. Figure 3-8 with a 600
mm drum of 185 mm diameter at 60 rpm and two sets of double or triple
blades (pad-dles) can produce 300 to 400 kg hourly. Eggs squeezed through
the perforations are col-lected into a container with a mesh bottom
in order to drain off excessive liquids.
The major part of the debris and impurities are pushed
out by the blades towards the drum front. However many broken egg membranes
or fragments of connective tissues remain in the mass of screened eggs.
If the amount of impurities is substantial and espe-cially when the
one step low salting process is considered, eggs should be washed in
or-der to get rid of broken eggs, blood residuals, slime and other impurities.
At low salini-ties these impurities tend to trigger the spoilage process.
Potable, very cold water or light brine (2-3%) is used at a ratio 1:1
for a quick rinse. The floating impurities are de-canted and the eggs
passed for dewatering over a flat mesh horizontal screen, or eggs are
run over a slope screen. Dewatering takes 15 to 45 minutes.
If held after washing for a long time eggs may get soft
even at chilled temperatures. If eggs are processed according to the
two step technology rinsing could be elimi-nated/because the cleaning
from impurities will take place while desalting. It is recom-mended
to execute salting in equal weight batches.
The salt-preservative mixture, (for example sodium benzoate)
is also preweighed in per batch portions according to the recipe. This
eliminates potential mistakes. Eggs are mixed with fine fisheries salt
to the buyer's specification, usually 13 to 15% by weight. Sodium benzoate,
if desired, is mixed with the salt. The concentration of sodium benzo-ate
in the final product should not exceed 1,000 ppm. Variations in the
amount of salt added may occur depending on egg maturity and freshness
which effects the resulting drip loss and hence the final product salinity
in cases of one step salting. For the two step technology tuning of
salt-preservative weight ratio per batch is less important. Batch size
varies from 15 to 20 kg to ensure even salt distribution, one barrel
would contain 4-5 salted egg batches. It is recommended to apply the
salt through a sieve. Salting is usually done by gently mixing the batches
by hand in stainless steel or plastic bowls. However it is possible
to use low revolution drums or vertical shaft mixers. When mixing by
hand the operator gains experience in determining the moment when the
stirring is stopped. This requires a very qualified operator.
At first the eggs stick together, but soon the salt extracts
liquid from the eggs and forms brine. Foam appears on the .surface.
Further stirring makes the mixture denser and indi-vidual eggs are easily
separated from others. If salting is stopped too soon the eggs will
continue to release liquid during further operations. If the stirring
goes on for too long the egg mass may get stickier and form lumps. Both
extremes are undesirable. Properly done eggs do not stick to smooth
wooden paddles but tend to roll off. Stirring usually lasts 15 to 30
minutes depending on egg temperature, the longer time relating to colder
The above recommendations have to be followed strictly
only for one step processing. Bulk containers are filled with batches
of eggs of the same quality, covered and hermeti-cally sealed. The commonly
used 105 kg plastic barrels have a rubber liner inside the lid and a
hoop that clamps it. The barrel is left to cure upright in a chillroom.
After several days the salted eggs shrink and settle eliminating potential
air cavities. The head space is then topped off with more roe from the
same batch to comply with the approved packag-ing weight of the client.
This may involve control of the drain weight. The bunghole is used to
perform the final topping with brine, which prevents the top layer from
drying out. For the following 12-14 days the barrels are placed on their
sides and rolled every-day to get a homogeneous product, avoid clumps
of roe and finish the curing process. The process of rolling barrels
and topping them with brine may be repeated if necessary during storage
life. Barrels are kept and transported at chilled temperatures to the
retail package caviar processor. The processor usually keeps the barrel
for lengthy periods of time and processes caviar throughout the year,
or may keep the barrel even for a longer time.
The second step of the two step processing technology
starts with desalting and draining.
At the second step of processing, eggs are first desalted
in light brine (1 to 2%) to reach the targeted final product salinity,
usually 3 to 5% and further dyed, sometimes fla-voured, vacuum packed
and occasionally pasteurized. The two-step lumpfish caviar process has
dominated the market place for tens of years.
Desalting is done using potable cold fresh water. Use
of 1 to 2 % brines could be con-sidered for better washing of potential
slime and as a safety precaution against 'over-freshening'. Desalting
time can be determined only by experiments.
Obviously, if retail packaging capacities are sufficient
there is no need to pack low salted roes in large barrels. One could
pass them on directly after salting and draining to the packaging line.
Traditionally lumpfish is dyed in black and partially (10%-15% of worlds
production) in red. Usually less mature lumpfish eggs are dyed black
and mature eggs are dyed red. The major quality problem in dyeing is
to achieve stability of col-oured eggs during subsequent technological
steps and for the required shelf life at the consumers end.
Fading of colour as a result of prolonged storage or pasteurization
are common. Most damaging to product image is colour leaching when the
product is consumed: e.g. blackening of all kinds of garnishes when
black lumpfish caviar is added. There are nu-merous food grade dyes
in the market place which when used in different combinations, at different
concentrations, egg-dyeing solution ratios and contact time exposures,
pro-vide for any desired colour shade. Some dyes are synthetically manufactured,
some constitute preparations mode from natural products e.g. beets or
tea. In caviar dyeing both groups are used. Legality of the use of dyes
for different countries should be regu-larly checked, as they may change.
The colour fading and leaching can be diminished or eliminated
by lowering dyeing so-lution pH to 4.5 - 4.8 and by using acidifying
food additives such as ascorbic acid, citric acid, or vinegar. Such
acidification has an adverse effect in that it results in an unac-ceptable
sourish taste which has to be suppressed during product final flavouring.
This is not always possible, that is why the choice of nonfading quality
dyes is so important.
As shown in Figure 8-3 acidic components could be introduced
with the dyeing solution or later with the flavouring mix. Some processors
claim to introduce dyes and acidifying substances during the desalting
process. In the later case much more dyeing substance will be wasted.
To achieve the designated pH level, up to 1% by weight citric acid may
be added to the dying solution.
All the dyes used are water soluble. Some dissolve better
than others. To be sure of complete dilution it is advisable to use
hot water at 80-90°C. It is typical to dissolve 150 g of dry dye
powder in 2 liters of water. A typical ratio is 25 to 40 kg of eggs
mixed with 0.5 liters of dyeing solution at the above concentration.
Dyeing can be performed not only by mixing the solution with the eggs,
but also by dipping eggs inclosed in a perforated container into a large
size dyeing solution vessel.
A typical exposure mixing time is usually 4-5 minutes.
However, many processors claim both lower and higher dye concentrations,
and accordingly longer or shorter exposures.
All the numbers here are arbitrary as the art of obtaining dye stability
is still developing. Several published papers investigated colour fading
as a result of thermotreatment (pas-teurization) depending on product
salinity, adjusted pH values, exposure time and tem-peratures and proved
that food grade dyes perform very differently. Some of the dyes withstand
the rigor of thermotreatment/ some don't.
Draining and rinsing after dyeing aims to wash off excess
dyeing solution. These proce-dures, if performed twice, may result in
lighter shades as compared to the ones which were visually assessed
before rinsing. Some processors claim to use dyeing mixtures which do
not require rinsing. This depends on the dryness of the eggs and how
the ab-sorbtion of dyes proceeds. In this case the next operation of
flavouring could be com-bined with dyeing. Obviously after flavouring
the product is ready for retail package fill-ing.
To offer flavouring recommendations is most difficult,
because they are numerous and usually reflect the ethnic market taste.
There are plenty of opportunities for further de-velopment. The principal
goal in introducing the final additive mix is to improve or rather standardize
the product, so it will be recognizable as a certain brand name. Addi-tion
of thickeners or gums is produced with the aim of engineering a favourable-mouth
feel, shininess and to prevent lumping. All this is aimed to mimic the
best sturgeon cav-iar types and grades.
Flavouring and thickening agents known to be used in lumpfish,
whitefish and other small size caviars are: 'Worcestershire Sauce' (popular
in UK), anchovy paste, bay leaf extract, spices, vegetable oils, traxanthan
and other gums, glycerol, inverted sugar, vine-gar, and onion extract.
Preservatives used (subject to regulatory rules) are sodium ben-zoate,
potassium sorbate, niacin, sodium tripolyphosphate, lysozyme.
Lumpfish caviar and the majority of small size eggs easily
withstand the rigor of filling machines and the pasteurization process.
The best pasteurization temperature should be chosen after experiments,
to avoid excessive egg toughening and avoid undesirable fla-vour formation.
For lumpfish and other small size caviars the range is 55-70°C.