5.0 PACKING

CAVIAR SALINITY, IN%	TEMPERATURE IN °C
	FREEZING STARTS	FULL FREEZING
3.6	-7.5	-8.5
5.8	-10.5	-17.0
7.6	-15.0	-17.0

Apart from the salt content, the freezing temperature is affected by moisture and fat con-tent. The more fat, the lower the freezing temperature.

In comparison with pure brine, the egg inner yolky fluid of the same salinity starts to freeze at temperatures 2 to 2.5°C lower. This would be the lowest storage temperature to keep caviar refrigerated. Table 5-2 shows how strongly storage temperature affects shelf life. Beyond the storage times shown in the table the caviar might be down- or outgraded.

TABLE 5-2

SALMON CAVIAR SHELFLIFE VS. STORAGE TEMPERATURE
(3.5 TO 5% SALINITY)

STORAGE TEMPERATURE IN °C	SHELFLIFE IN MONTHS
+10 to +18	0.15 - 0.2
0 to +2	3-4
-2 to -4	5-12
-5 to -7	8-16

When caviar is refrigerated the membranes become denser, the egg inner yolky liquid more viscous and the egg as a whole becomes more elastic. These properties disappear when caviar is brought back to room temperature. So the changes are reversible. When caviar is subjected to the freezing of inner yolky liquid, some irreversible changes oc-cur. Yolk of a salted egg comprises a protein-fat-brine emulsion. When the frozen brine component is thawed the fat droplets congregate in larger particles, and a protein con-taining liquid is coagulated and released from the emulsion. This in turn makes the egg less elastic, the egg looks dull and is easier to rupture. This is why when salmon caviar is frozen in large size, and tall pails, one observes after thawing a lot of juice on the bot-tom and a considerable number of broken egg membranes. However, the taste and fla-vour do not change significantly. Freezing caviar in small retail packages is the most advantageous way of freezing.

Frozen caviar constitute a non transparent hardened mass of eggs which contains ice crystals and is much paler than the original caviar colour. Frozen caviar stands up very well to the rigors of transportation. That is why to get the largest gain in quality and shelf life, when frozen caviar is shipped, thawing should be done only before the prod-uct is passed on to the consumer. The prevailing practice in sushi bars and delicatessen stores is to keep salmon caviar frozen, and only thaw it according to demand. Freezing and storing should be done at -20°C. Japanese researchers recommend long term storage at -40°C. Thawing should be executed as slowly as possible. For salmon caviar minimum damage to the egg (rupture and juice release) is achieved when the temperature is raised not more than 2°C per day.

Release of excessive juice and collapse of the egg shape depends very much on caviar initial quality. Second grade caviar with initially soft and weak eggs will drastically de-grade as a result of freezing and become unusable. Only high quality first grade, loose and dry caviar should be frozen. Smaller size egg caviars, except for sturgeon eggs, are less susceptible to freezing. High quality salmon caviar has been kept frozen in vacuum packages for over 2 years and retained its high quality.

Our own chemical and organoleptical examinations proved that the shelf life of frozen salmon caviar can be safely extended to 1 year. This means that caviar supply can last year round, which is important for this highly seasonal product in terms of supply - de-mand balance. When high quality eggs were used for frozen caviar, a qualified taste panel gave higher marks to this product as opposed to the fresh caviar processed from the same roe.

If the frozen concept is used for small size retail packaged caviar, the risk of develop-ment of excessive juice is negligible as the small amount of eggs is protected by a rigid container and they are not squeezed by their own weight.

In large bulk pails one finds after thawing a considerable amount of juice. For this rea-son we recommend that the institutional bulk package size of frozen caviar should not exceed 3 pounds.

In spite of all this, there is still prejudice among retailers and consumers who often re-ject consideration of caviar as a frozen product. Strangely enough, the quality cautious Japanese market tends to accept frozen caviar, whereas the European market hesitates to do so.
An additional argument in favour of the frozen concept is that there is no hesitation to use vacuum packing for both retail or bulk institutional packages, which helps to fight losses of moisture and fat oxidation. It should be noted that without vacuum, even fro-zen products in the long run are influenced by these processes, especially the upper layer of caviar in the package, which is exposed to air.

The issue of using vacuum packing for refrigerated caviar is often disputed by the ex-perts working with product safety programmes. The fact of the matter is that if a refrig-erated, uncooked, vacuum packed product is temperature abused during its lifetime, botulism can develop. The vacuum situation might prevent any visible signs of common spoilage but induce botulism development, which is not noticeable and the user may get the wrong impression that the product is safe.

Having raised this potential danger we must point out that historically, caviar has a very good record regarding botulism occurrences. The development of botulism toxin in salmon caviar, inoculated with Clostridium botulinum, was tested on our behalf by the U.K. Tony Laboratory. No toxin was detected after inoculation and storage for 3 months at +20°C. The caviar was 3.5% salinity at pH 5.5.

We would like to speculate that one reason for the extremely low probability of con-tamination of caviar with botulism is that the roe constitutes part of an inner organ, pro-tected naturally by many layers of connective tissues which do not come in contact with the external environment.

If the technological operations and the general sanitation level in the plant are adequate there is an extremely low probability of caviar becoming contaminated. To conclude we believe that vacuum packing and freezing of caviar are acceptable procedures.

5.2 BULK AND RETAIL PACKAGE

It is common sense that caviar, as a non-cooked and perishable product, should be proc-essed, preserved and packed in its final retail or institutional package as close as possi-ble to the fishing grounds. However, for years the logistics of the caviar distribution sys-tem remains awkward. Namely the lions share of caviar is repacked and sometimes re-processed far from the fishing grounds and close to the distributors worldwide. The re-packed packages often end up at the original fishing sites as retail products. This tradi-tion introduces inevitable losses of quality and loss of original labelling information.

The motives behind this unusual marketing tradition are of a purely commercial nature, e.g. custom duties in France are 30% on jars but nil on pails. However, in the long run such a strategy has proven to be damaging. Nowadays processors are reacting favoura-bly to the suggestion of developing retail caviar products.

The Soviet Union is increasing every year its retail packaging line capacity for both sturgeon and other caviars, altogether 8 automated and numerous semi-automated proc-essing lines are taking care of about 50% of the total sturgeon caviar production. Stur-geon caviar is vacuum packed and pasteurized in glass jars, mainly 2 and 4 oz (56 and 113 gram respectively), and 90 gram tins. The rest is packed in 1.8 and 0.6 kg cans/ the lid being secured with a rubber band. The cans are packed higher than the rim, up to 7 mm for 0.6 kg and 15 cm for the 1.8 kg can. The lids are put on according to the marks on the body and lid. The 4 to 6 cm wide rubber bands are put on after pressing and draining. For the internal market, and for the so-called pressed caviar, small wooden barrels with a sophisticated fabric and oil paper lining arrangement are still used. In the past wooden barrels were the prevailing packaging option.

Salmon caviar is packed in the Soviet Union in 150 g tins and 5 Ib plastic pails. Also 25 and 50 litre wooden barrels are used. Pollack roe in flat 100 g tins are becoming increas-ingly popular. Iranians have a limited capacity for packing sturgeon caviar in 100, 200 and 300 grams tins. The rest is packed in 0.6 and 1.8 kg tins.
Alaskan and British Columbia salmon caviar are almost exclusively packed in institu-tional plastic containers and pails ranging from 1 to 10 and sometimes even to 50 Ib. pails (see Figure 5-1). Less than 2% of salmon caviar in B.C. is packed in 100 and 50 g jars.

FIGURE 5-1: Bulk Salmon Caviar Packages

On the top and bottom of each package a waxed paper gasket is used. The packing of bulk containers is done in portions to allow the caviar to settle. Slight pressure could be applied to ensure it is tightly packed and to dispel air cavities. Sometimes caviar is put in polyethylene bags and only then into pails. Any air cavities accelerate quality dete-rioration. Longitudinal shapes of plastic pails, as well as the large sizes of any bulk package result in more drip and egg breakage. If the packing is not fully airtight, the outer layers dries up during transportation which create losses.

When caviar is frozen in bulk packages a simple method is used to avoid product sur-face oxidation. Before freezing the container is turned upside down, the caviar slips to-wards the lid and may even create some vacuum at the bottom. After freezing the con-tainer is turned right side up and the product remains frozen and fills the container up to the rim. No bulging of the frozen mass towards the lid is observed.

Another improvement is to put oil-paper divider gaskets between each measured portion of the bulk package. This allows the product to be thawed in portions according to the demand thus avoiding freezing twice. It is possible to defrost and freeze caviar again, however, all the described deficiencies (egg weakness, less viscous yolk, collapsed shape and excessive juice) will manifest themselves more strongly. East coast Canadian and Icelandic companies are still packing the majority of their heavy salted lumpfish roe in 105 kg plastic barrels. However more and more companies on the fishing grounds are switching to retail packaging of a finished, dyed and ready to consume retail packaged product.

It is only a matter of time, before the concept of retail packing of all types of caviar close to the fishing and processing sites will prevail.

Meanwhile major repackers at consumption centres (New York, Paris, Hamburg, Lon-don) are utilizing their packing capacities to repack all kinds of caviar. This provides for a diverse product list under the same label and regular employment, because different types of roe are harvested throughout the world at different times.

 

5.3 PACKAGE TYPE

Both the type and size of package determine the targeted market niche. The dominant existing retail package is a shallow, wide opening glass jar, slightly cone shaped. The most common sizes are 50 and 100 grams, or 2 and 4 ounces. Three varieties of closures are used: crimping (traditional Russian jar), twist off cap (Romanoff) and screw cap (Danish caviars). There are some 100 to 150 g aluminium tins on the market but glass sizes larger than 100 g are rare.

In British Columbia special 50 and 100 g caviar jars, with a twist-off lid, are manufac-tured. 'Snap on' type vacuum packed tins for caviar are custom packed in USSR for 'Lufthansa'. As opposed to the crimped glass jars or sealed cans the 'snap on' type clo-sures do not need special tools to open them.

It is commonly known (and written on caviar labels) that after opening of the retail con-tainer, caviar has to be consumed within a reasonably short time, often 2-3 days. This makes it difficult to serve caviar in places like restaurants or on airlines. To service this market it would be appropriate to use single serve portions of 10 to 20 g. These portions could be packed in preformed aluminium or plastic, lightweight containers and ther-mosealed with foil. Single serve portions could be frozen as well as pasteurized.
Fancy glass or ceramic containers are used for the gift item market. Figure 5-2 the con-tainer can be used as a household item after the product is consumed.

FIGURE 5-2: Fancy Containers

Depending on the chosen packaging option the cost of retail packaging compared to bulk may increase substantially. But these costs will be always absorbed by the higher price of retail packages.

 

5.4 CHEMICAL PRESERVATION

It should be said upfront that an optimal solution to the question which preservative is best to use for caviar, is not yet solved. The consumer trend towards preservative free products is not relevant in regards to caviar since the amount of caviar in our overall food consumption is negligible. In dealing with an expensive and perishable product the use of preservatives is advised. The Russian quality standards for products certified for export prohibit processing without chemical preservation. Caviar can be processed without preservatives for export only at the customer's request.

Certainly, any use of preservatives has to comply with the regulatory restrictions, such as "GRAS" (Generally Recognized As Safe for use in foods, U.S.A.), or additives ap-proved by the European Community which have a designated registration number with the letter 'E' in front (e.g., E211 - means sodium benzoate), or similar restrictions. Regu-latory requirements are different in different countries and change from time to time.

There are several ways to introduce preservatives into the product. For dry salted cav-iars (e.g. sturgeon, lumpfish), the crystalline preservatives are mixed into the salt and applied together. In this case one should check the residual level of the preservative in the final product, since it depends on the brine uptake after salting. The Japanese proc-essors sometimes introduce preservatives into the brine. For caviar products, where the brine is reused not more than 2-3 times, this may be costly. When reusing the brine the solution has to be fortified to the original desired preservative concentration. Preserva-tive concentration in the final product should be checked.

A better way to introduce preservatives for brine salted caviars is to apply them after salting, and before draining is finished. The preservatives used are usually highly solu-ble in water. Small amounts of measured preservative solution can be evenly sprinkled over the caviar batch and then gently mixed in while the caviar is wet. In this case the uptake of preservative is minimal, which makes it easier to monitor the preservative concentration in the final product.

The preservative combinations historically used in different caviar products by the So-viet Union (and still in use for their domestic market) are:

Nisin is an antibacterial substance produced by certain strains of the lactic acid bacte-rium, Lactococcus lactis. Stable to boiling in acids and soluble in dilute adds, it is widely used in cheese processing. Successful use of Nisin for caviar was reported by the Russians.

Nisin's specific action is against spores. Unlike other preservatives nisin inhibits the germination process at the stage of pro-emergent swelling of spores before cell division. It is demonstrated that spores damaged by heat are more sensitive to nisin. Nisin levels needed to control non-botulinal spoilage are 250 to 500 IU/g, for antibotulinum protec-tion levels higher than 500 IU/g are required.

The experiments were carried out on pasteurized, processed cheese spreads with mois-ture contents of 51-60% and low sodium chloride levels. Nisin was effective in prevent-ing the growth and formation of Clostridium botulinum type A and B toxins. Many countries permit the use of Nisin for cheese, milk products, canned vegetable products, bakery products at concentrations from 500 to 10,000 IU/g. Toxicity studies carried out with levels of Nisin far in excess of those that would be used in food indicate that Nisin is non-toxic. Nisin is rapidly inactivated in the intestine by digestive enzymes. In 1969 the Joint Food and Agriculture Organization/World Health Organization (FAO/WHO) Expert Committee On Food Additives recommended its acceptance for food use.

Exported caviar is prepared according to customer specification. For the majority of im-porting countries the only preservative allowed nowadays is Sodium Benzoate. France allows the use of Hexamethylentetramine and Sodium Benzoate in equal parts, less than 0.1%. There are cases when caviar meant for domestic use in the Soviet Union, but somehow exported, contains borax. Quality certificates should be requested and chemi-cal examinations done.

In the past Japanese processors have used a sophisticated combination of preservatives and colour enhancement agents for salmon caviar:

The mixture was introduced into the brine.

For dry salting of carp, whitefish, pollack, and herring caviars, 0.16% potassium nitrate (on the weight of the caviar), is introduced with the salt to give the finished product an even pinkish-yellow colour. In other countries the processors are mainly using sodium benzoate (0.1%) or not using preservatives at all. Benzoic Acid and Sorbic Acid are listed as class II preservatives in the Canadian Food and Drug Act:

'For marinated or otherwise cold processed packaged fish products, sodium benzoate may be used but the maximum level may not exceed 1,000 ppm'.

B.C. Research requested and obtained a positive reply from the Bureau of Chemical Safety, Food Directorate, Health Protection Branch on the use of benzoic acid for cav-iar. Sodium benzoate is usually used because of its better solubility in water.

The effectiveness of chemical preservatives has to be carefully considered. In most cases caviar spoilage starts due to microorganism growth. In essentially sterile packages it may be caused by enzymes or fat oxidation. The degradation ultimately renders the product unusable. The antimicrobial potency of all commercial food preservatives is pH dependant. Sodium benzoate is active against yeast, mold and bacteria. However, it is most effective up to pH=4.0 and not recommended above pH 4.5.

Thus, for caviar products sodium benzoate's effectiveness, especially in bacterial con-trol, is very limited. Sorbic acid and potassium sorbate show best activity against yeast, mold and bacteria at up to pH levels of 6.5. They do not show any activity against lactic add bacteria. The upper pH limit of sorbate's efficacy warrants their use in caviar prod-ucts. Although a sorbate/benzoate blend would have a broader range of efficacy against all kinds of microorganisms, this combination is not used.

The use of preservatives does not exclude pasteurization. However, usually pasteurized caviar is not preserved chemically. The best policy would be to use preservatives to cus-tomer specification. Unfortunately the customer is often unknown when processing takes place. The reluctance to accept preservatives by consumers is reenforced by the ban in many countries on previously used preservatives which later proved to be car-cinogens, e.g. borax, nitrates.

One additional obstacle in using chemical preservatives is the possible product after-taste. Sodium benzoate is characterized by a sweetish, astringent taste. Urotropin (or Hexamethilentetramine) has a sharp sweetish and bitterish aftertaste. Potassium sorbate has neutral taste characteristics. Modem ways of food flavouring allows the processor to compensate for any taste distortions.

Antioxidants are not used for caviars. We don't know any reasonable explanation for this.

Certainly, caviar quality assurance efforts should be directed towards providing fresh roe for processing, immaculate sanitation and good packaging solutions and adherence to storage recommendations. However, cases of caviar quality problems during shelf-life still occur. Thus the caviar processor, distributor and consumer are facing the neces-sity of further development of optimal preservation technologies.

The benefits which preservatives and antioxidants would provide for caviars, apart from longer shelf-life, are reliability, uniformity of quality, protection of wholesomeness, protection of fat-soluble vitamins. In advocating the use of preservatives one should stress the limited effectiveness of preservatives under conditions of temperature abuse. Table 5-3 illustrates the effect of preservatives on microorganism development for salmon caviar at various storage temperatures.

TABLE 5-3

RELATIVE GROWTH RATE OF MICROORGANISMS

USE OF PRESERVATIVES	AT STORAGE TEMPERATURES, °C
	12-18	6-11	0	-2	-3
Caviar without preservatives	2.5	1.75	1	0.75	0.35
0.1% urotropin added	1.75	1.25	1	0.70	0.30
0.3% Borax added	2.00	1.85	1.2	0.80	0.30
0.1% Urotropin and 0.3% borax added	1.50	1.05	0.6	0.50	0.30

As one can see at -2° and -3°C preservatives are not beneficial. It is only at abusive storage temperatures that the preservatives help. Keeping caviar cold along the harvest-ing, processing and storage chain provides the safest quality assurance.

 

5.5 ADDITIVES AND DYES

In 1854 Mr. R.G. Westacott of Worcester, Massachusetts, registered with United States Patent Office a patent No 7,895 on 'Sturgeon caviar taste improvement by adding 'oil extracted from the liver or milts of the male sturgeon'. Since this first attempt to enhance caviar product flavour many attempts were and are being made.

Salmon caviar is known to be sweetened, artificially dyed with bright red dyes, smoked and oiled. Adding up to 0.015% by weight of the humectant glycerol aims to prevent the eggs from sticking. Glycerol is introduced together with oil. It is used often for sockeye caviar because glycerols sweet aftertaste covers the potential slight bitterness of sockeye caviar.

Oiling is widely used. Vegetable oil is introduced before packing in order to prevent eggs from sticking together and to make them look shiny. Oil is added in the range 0.3 to 1.0% by weight, on average 0.6%. If the eggs are loose minimal amounts are applied. Oil is sprayed evenly over the surface of drained caviar and may be gently mixed in manually, on a flat stainless steel table using spatulas. Some sources recommend pre-heating oils to 160°C and then cooling them down to normal temperature before use. Sometimes oil is applied to the table surface where the eggs are mixed, to the palms of the hands, to the bowls and instruments. This prevents whole eggs from sticking to the surfaces, whereas broken membranes remain stuck and can be easily removed.

Adding oil may introduce into caviar a foreign flavour specific to the oil, which could spoil the taste. The oil should be of highest quality, refined, of neutral taste and mini-mally susceptible to oxidation and evaporation. Olive, peanut and corn oils are recom-mended.

Dyes are used almost exclusively for smaller size eggs to obtain bright attractive colours (e.g. the orange-red in flyfish caviar) or to imitate the most expensive sturgeon black caviar (lumpfish and whitefish caviars).

As in the case with preservatives the use of dyes is strictly regulated in each country by type and allowable concentrations. In Canada, the limits are within 150 to 300 ppm. In the U.S., the decision of maximum concentrations is left to 'good manufacturing prac-tices'.

There is, though, a group of dyes which are exempt from certification - usually the ones derived from natural plants. These dyes contain many unidentified organic components., e.g. carp caviar is dyed with a beet extract, which also sweetens the product.

Synthetically manufactured food dyes are pure substances and their use is always regu-lated. Some dyes could be of both natural or synthetic origin, e.g. caramel, carotenoids. All dyes are declared on the label by their individual name or certification number. The cost of synthetic dyes is usually less.

Dye manufacturers usually supply blends of primary basic dyes to fit the caviar proces-sor's requirements. Dyes can be supplied as powders, granulated or predissolved. Powders are not convenient because they are dusty and difficult to handle. Dyes for caviar should have very high solubility in water and be fully dissolved before use in a dyeing solution. Solution is facilitated by stirring and warm-ing. The strength of the dyeing solution and the caviar exposure (contact) time should be checked experimentally in order to find the best combination. It may differ even for the same type of caviar if the eggs differ in maturity, salinity or freshness.

Dyes may degrade from heat, light, oxidation or due to microorganisms. They also react differently depending on final product acidity.

It is advisable to prepare a concentrated water stock solution to keep consistency of product shade. This solution should be stored protected from heat, light and contamina-tion. Poorly dyed caviars, where the dye fixation is not stable, will leach when served as garnish and make the product not useable, see Figure 6-1.

Some caviar processors are adding flavouring agents to produce a caviar product which is easily recognizable and favoured. This is done only with roes which do not have a distinguished, natural, yolky, pleasant flavour but have rather a blend taste, e.g. cod, pike herring, desalted lumpfish eggs, etc. The commonly used flavours are:
bay leaf extract, vinegar marinade, lemon juice, pickle mix extract, egg yolk powder, anchovy flavour, meat sauces, etc.

There are on the market salmon, shellfish, sturgeon and even caviar concentrates in the form of paste and water or oil soluble flavours. A research challenge is to develop a sturgeon-caviar substitute from lumpfish or whitefish roe, which tastes similar to stur-geon caviar, dyes a greyish-brownish colour, and has soft egg membranes in order to eliminate the chewiness. The existence of a very specific sturgeon flavour has been con-firmed by numerous organoleptic trials. This flavour can be described as very mild, pleasant, sweet, yolky, not 'fishy' and it is easily recognizable.

 

5.6 PASTEURIZATION

Pasteurization technology of food products has not changed essentially since it was sug-gested by Louis Pasteur over a century ago. Pasteurization, i.e. thermotreatment of air-tight or vacuum packed caviar, aims to kill the majority of microorganisms, inactivate ferments and create conditions to slow down the process of spore development. As opposed to cooking processes, which kill all microorganisms (and spores at elevated tem-peratures), caviar pasteurization is executed substantially at mild temperatures which do not affect the organoleptic properties of caviar: taste, texture, and colour. Pasteurization of caviars aims to provide longer shelf-life, and even allow short term storage at room temperature. It is one more statistically sound safety barrier for food quality which may be utilized together with or without chemical preservation. It does not guarantee free-dom from spoilage at abusive temperatures if the initial microbiological contamination is extensive and the type of microorganisms involved tolerate the combination of pas-teurization temperatures and exposure times.

Pasteurization makes it easier to meet the market demand for extra low caviar salinities, while not using chemical preservatives and still having a reasonable shelf life. Use of 'double' pasteurization is reported to eliminate the spores of the spore forming microor-ganisms. Before the second pasteurization, the caviar is incubated for at least 24 hours at ~25°C to allow the spores to vegetate and become susceptible to the second pasteuri-zation treatment. It is reported that sometimes this pasteurization and incubation proc-ess is repeated alternately three times. Another advantage of pasteurized caviar is that they withstand the rigor of freezing much better in that the eggs do not get softer. A storage temperature of -10 to -20°C could be considered.

Pasteurization is a costly technological operation (labour and energy) which also ad-versely affects product organoleptical properties if the technological regimes are not controlled properly. The range of pasteurization temperatures is 50 to 70°C. At these mild temperatures egg proteins do not undergo substantial coagulation and their appear-ance remains the same. Slight changes in colour are noticeable, e.g. paling for salmon caviar, darkening towards yellowish colour for the off-white whitefish caviar. After pas-teurization the outer membrane and interior yolky liquid become denser. As a result of thermal denaturation the amount of soluble proteins, e.g. albumin is reduced. Different caviar types react somewhat differently to pasteurization. The delicate sturgeon eggs tend to firm up, get chewier whereas soft or immature salmon eggs may lose their shape. Mature and fresh salmon eggs do not change substantially as a result of pasteurization.

Only the best grades of caviar, for maturity and freshness, should be pasteurized. Caviar designated for pasteurization should be drained after salting to a lesser extent. In fact caviar destined for pasteurization is filled into containers quite moist. Pasteurization of poor quality eggs may produce unedible product because the eggs may burst and offen-sive odours may be released.

The recommendations of pasteurization time-temperature regimes often differ. Obvi-ously the higher the pasteurization temperature and longer the exposure, the more effec-tive is the microorganism and enzyme inactivation process. The limits to pasteurization temperature and exposure time are set by the described above adverse effects on caviar organoleptical properties. In each case the processor has to make a balanced decision depending on initial contamination, egg quality, required shelf-life and consumer re-quests. The numerical values given in Table 5-4 summarize the experience of caviar processors throughout the world and can be used as guidelines.

TABLE 5-4

PASTEURIZATION REGIMES

CAVIAR TYPE	MAXIMUM PASTEURIZATION, TEMPERATURE, °C	EXPOSURE TIME (wanning up time excluded), min.
Sturgeon & Whitefish	58-59	60-90
Salmon & Lumpfish	65-69	60-120

What is important is that the accuracy of temperature control should be within ±1°C and the temperatures should be homogeneous throughout the pasteurizer space. It is well documented that at temperatures exceeding the maximum levels shown in Table 5-4 by 1 to 2°C, the changes in caviar are drastic and it may become unusable. For instance, at 56-60°C only slight changes in pink salmon caviar colour are noticeable, at 71 °C all the eggs look dull, at 72°C the egg yolk is totally coagulated and the caviar converts into a chewy "boiled egg mass'. It is reported that the use of nisin permits reduction of pas-teurization time, thus preventing eggs from excessive toughening.

The pasteurization temperature should be measured in the middle of the container. Pas-teurization in containers larger than 150 g is not heard of. Depending on the container design (glass or tin, dimension ratio) the 'warming up' period until the temperature in the middle of the container reaches its target, is different and ranges from 10 minutes for 25 g tins to 40 minutes for 150 g glass jar. Caviar pasteurization is usually performed as a batch process in a water bath, heated by electricity or steam. The water/caviar mass ratio in pasteurization tanks should be 5:1. The water temperature before immersing the racks could be raised by 1-2°C higher than the desired pasteurization temperature. The even-ness of temperature in the tanks is provided by constant water circulation. Water tem-perature is easy to control and monitor. The pasteurizers should have good thermoinsu-lation. Conveyor type pasteurizers, where hot water is sprayed over the containers are widely used for lumpfish caviar pasteurization. Figure 5-3c. Pasteurization tanks are of-ten self-made and care should be taken to ensure homogenous temperatures throughout the tank volume, automatic temperature regulation, sufficient thermoinsulation, safe unloading of the hot racks while moving them for cooling and drying.

FIGURE 5-3: Lumpfish Caviar Packing Line, Reykjavik

5.7 PACKAGING OVERVIEW

An example of a step-by-step retail packaging technology flow-chart is shown in Figure 5-4.

FIGURE 5-4

CAVIAR RETAIL

The diagram does not cover all possible options and serves only to outline caviar retail packing specifics. The choice of packing line machinery and specific technological steps depends on the desired packaging line capacity. Any retail packaging line is quite universal and could be used with minor adjustments for packaging caviar, fisheries or other products. Container sterilization can be done using steam sterilizers or dry-heat ovens. Lids or caps, with plastic or other sealing liners, may not withstand the high ster-ilization temperatures and should be washed or rinsed with hydrogen peroxide solutions.

Frozen bulk products are thawed to 10°C to provide for sufficient fluidity of the product while it is filled and compacted. The filling operation is one of the most time consuming in the whole caviar processing line. Both volumetric and weight portioning can be used. Most important is to provide for a dense packing, so that all air pockets in the container are eliminated. Compacting salmon caviar with excessive force after the container is filled may bring about the rupture of eggs. That is why manual packing takes place in portions, the previous portion being compacted before the next portion is filled. In automated fillers the so-called 'bottom up' technique may be useful. This technique syn-chronizes a movement of the filling nozzle upward from the container bottom during the filling process. The same desired effect can be achieved by synchronized movements of the container down.

Salmon caviar constitutes a semi-viscous sticky material which is extremely difficult to fill. Its consistency and viscosity differ substantially from batch to batch. Single eggs stick slightly together and also tend to stick to the bins and containers. Vegetable oil may be used to facilitate egg mass flow. Also, 100% brine can be used, in tiny amounts for the same purpose, keeping in mind that some brine will be absorbed by the eggs af-ter packing. Difficulties in eliminating air pockets could be caused by the glass jar con-figuration. In case of the jar in Figure 5-5, it is important to compact salmon caviar in the cone shaped comers. Other difficulties in filling are related to weak eggs, which burst easily when exposed to excessive mechanical pressure.

FIGURE 5-5: Manual Filling

These conditions warrant a relatively slow salmon caviar filling process. This is not a problem with smaller size egg caviars.

Many packers are using piston fillers and experience excessive egg breakage. Pneumatic piston fillers are volumetric fillers which push the product with considerably speed. Me-chanical piston fillers allow for better piston movement speed regulation.
Another solution is to use an auger filler with an undersized auger and oversized funnel. Portioning is provided by setting the number of auger revolutions per portion. At auger speeds of 150 to 200 r.p.m., accurate 50 g weight portioning can be achieved. To avoid caviar drips after the auger stops, a cutoff disk should be used.

To summarize, mechanised and automated filling of caviar products into retail contain-ers is possible with speeds of 8 to 30 containers per minute per one filling head, the lar-ger number relating to small size containers and strong eggs. The majority of small re-tail caviar packaging companies are filling caviar manually, sometimes using specially designed spatulas.

If the retail package is meant for vacuum packing a sufficient head space should be left, usually 3 to 5 mm from the rim. If the package is only air tight sealed, no head space is needed and the container should be filled to the rim. In both cases it is advisable to put a tight oil paper gasket over the surface of the caviar to preserve the product surface from drying, freezer burn or simply to keep it neat. Gaskets could be soaked in antioxidants, preservatives, brine or vegetable oil.

There are many types of vacuum packing or sealing machines available. The choice de-pends first of all on the closure design: double seaming of cans; crimping metal closures over glass; twist-off; press on twist-off; pry-off; deep snap-reseal closures; or ther-mosealed foil lids. Figure 5-6. Not all of the vacuum closure types withstand pasteuriza-tion.

FIGURE 5.6: Retail Package Closures

Depending on the needed capacity the widest range of automated machines are avail-able: from small vacuum chamber machines with manual in-feed of a single container to fully automated multi-head vacuum and gas-flush machines. There is not sufficient in-formation on the effectiveness of gas-flush technology for caviar products. Steam injec-tion into head space to obtain vacuum is not suitable for caviar/ because it may overheat the product surface.

Vacuumization maintains the majority of lids or ends concave.

A vacuum level of 125 cm of mercury is sufficient. A very affordable way to vacuum pack twist-off or similar closures by using a standard vacuum chamber is described be-low step by step, see Figure 5-7 and 5-8.

Figure 5-7:

Use Of Vacuum Chamber Machines

After filling, put the lid cap onto the jar and twist it lightly to bring the closure lugs in contact with the containers interrupted threads. Figure 5-7.4). Fill the chamber to capac-ity with jars. Figure 5-8.9. Close the chamber and draw vacuum. The air is drawn out of the jars because there is still a clearance between the glass and the cap. As soon as the chamber opens, atmospheric pressure will press the cap towards the glass rim, the plas-tisol gasket will vacuum seal the container, and the cap surface will cave in. Figure 5-8.10.

Figure 5-8:

Use Of Vacuum Chamber Machines

By applying reasonable force, close the twist-off cap tightly. It will turn only slightly and finish the vacuum packing operation. Figure 5-8.11.
Applying excessive torque when tightening may result in 'overturning' of the cap. A good idea is to execute the final tightening turn using a device which regulates the torque.

Some caps, for different reasons, won't cave in and the operation is then repeated. When vacuum packing is done this way it is necessary to use oil paper gaskets to prevent cav-iar from being sucked out. Check-weighing of caviar products is mandatory.

All the containers (pasteurized or not) are quickly washed at 50°C in 1-2% alkaline wa-ter and passed on for cooling in a 25-35°C waterbath with running water or by spraying with water at water temperatures not lower than 18°C to stop the pasteurization process. Finally, containers are dried by blowing warm dry air for 15-20 minutes or by wiping dry. Sometimes containers are placed in the pasteurizer upside down to make it easier to detect leakages.

Further operations of labelling, tamper-resistant sealing and boxing are self-explanatory. If pasteurized caviar is meant to be stored frozen, it should be refrigerated for at least 24 hours before placing in the freezer. Usually the original boxes in which the glass jars were supplied are reused for product delivery.