8.0 PROCESSING DIFFERENT SPECIES

8.2 PROCESSING LUMPFISH CAVIAR

Lumpfish caviar entered the European marketplace in the 1930's and became the most popular sturgeon-caviar substitute because .the eggs were similar in size and dyed black. It is difficult to identify the first lumpfish caviar processor, but certainly it was from Denmark, Germany or Norway. Lumpfish caviar is often called 'Danish'/ 'German' or 'Scandinavian' caviar. The growing demand triggered utilization of Icelandic, Green-landic and Canadian lumpfish resources. Lumpfish fisheries by nature is a small boat coastal fishery without on-board processing capabilities and the eggs are very perish-able. For these reasons the 'two-step' lumpfish caviar processing tradition developed in which the Lumpfish caviar underwent a first heavy salting and then desalting and dye-ing.

Step one consists of screening, washing and salting the roe to 10-12% salinity and keep-ing it at 0 to +3°C temperature in plastic barrels of about 105 kg net weight each. This is done at the plants on the fishing grounds Figure 8-2. The high salt content does not guarantee a better shelf life, proper egg handling, washing and cleanliness are still es-sential. Heavy salting results in egg shrinkage and loss of yolky interior substance.

FIGURE 8-2: Lumpfish Operation On the Fishing Grounds

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.

FIGURE 8-3

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 Fisheries

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 consumer's end.

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 before shipment.

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 temperatures.

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.