Capacidad de bombeo

Tuna 3.1.1.

The main inputs in Pacific tuna canneries are skipjack and yellowfin tuna. These can be found in the southern Philippine seas and in various pockets in the pacific. The tuna species are uniquely warm blooded, thus they are able to move quickly underwater and conserve more energy. Tuna are highly predatory and their diet consists of small to medium sized fish.

Tuna has become an important commercial product because it can be caught in huge volumes through low cost operations such as purse seining. Also, scientific studies have discovered that tuna contains very high levels of Omega-3 and protein, which are important nutrients in the human diet.

Tuna meat is widely used in different cuisines for its pleasant neutral flavor profile and firm texture.

Special care is required when handling carcasses of tuna because tuna tissues immediately produce histamine, a potentially toxic compound, at ambient conditions. Tuna is also known to contain a certain amount of mercury and it is essential that all processed tuna meat do not contain lethal amounts.

Ingredients and Additives 3.1.2.

3.1.2.1. Spices and seasonings

Spices and seasonings are added to provide the base flavor. Other Ingredients may include cuts of vegetables and broth ingredients. Philippine canneries source ingredients from varying places including Thailand, China and Macau, where dried seasoning is produced and sold at a lower cost. Vegetables and perishable ingredients components are sourced and prepared locally.

3.1.2.2. Liquid meduim

Generally, a liquid medium is added to prevent oxygen from occupying space in the can and to serve as a flavor carrier. Tuna is usually canned in brine or oil, but tomato and other broths are also used to create different flavors. As with spices and other ingredients, liquid additives are not specifically sourced.

Packaging 3.1.3.

3.1.3.1. Metal Cans

Canned packaging consists of steel plates that are electrolytically plated with tin. Tin plate is used in canning to prevent corrosion and protect the steel layer from rusting or reducing into the product. In contrast to stainless steel, tin plate can be disposed without danger and is less expensive than zinc plating. However, in fish canning, a layer of zinc lacquer is still added to prevent sulphides from decolorizing either the steel or the tin plate.

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3.1.3.2. Print labels

Print labels usually consist of glued print material around the cans. Labels are best mechanically applied to eliminate lead time. These materials are easy to produce and can be conveniently sourced from local suppliers.

3.2. Manufacturing Process

History of Canning Process 3.2.1.

The canning process was invented by a Frenchman named Bon Appert during the 1800’s, in the hope of finding a food preservation technology that would allow French soldiers to stay in camp for longer periods of time without having to resupply. Napoleon awarded Appert with 12000 francs for the discovery.

Appert discovered that heating food close to the boiling point of water then sealing them in glass jars prohibited the spoilage for long periods of time. At the time, microorganisms were yet to be discovered and the process was attributed to coincidence.

In later decades, Englishman Peter Durand refined the process by switching from glass to the tin containers benefitting the process by providing a cheaper, more durable and lighter material. He was also the first to apply the method of double folding the can and the cap to form a hermetic seal.

Principles of Canning 3.2.2.

The contents of canned food are ideal growth media for both aerobic and anaerobic microorganisms that cause spoilage and produce toxins. Aerobic spoilage is usually easy to detect by smell and essentially prohibited through hermetic sealing. Conversely, anaerobic byproducts are difficult recognize and spoilage of such type is easily overlooked. The worst case is that anaerobic byproducts reach toxic levels in food without the consumer ever noticing. Hence, there is every reason to heat to canned food products and eliminate anaerobic microorganisms that aggressively produce lethal toxins.

The most hazardous known microorganism with a significant possibility of being present in canned food is Clostridium botulinum, which is known to produce the botulinum toxin that kills within less than one hour of ingestion. To minimize the ingestion of botulinum and other deadly anaerobic toxins, it is important to treat the sealed cans with enough heat until the slowest heating point (SHP) of the can is raised to the lethal temperature and exposed at the optimum time. The optimum time of exposure is calculated by assuming that bacterial presence at lethal temperature follows a negative semi-logarithmic plot versus time, as shown in Figure 14.

In this form, the bacterial death rate is impossible to reduce to zero, but a remaining population of 10-¹² is considered to be commercially safe (Warne, 1988). The time to reach 10-¹² from an assumed starting bacterial population is the optimum time. The value D in the plot indicates the time required to reduce the population by one order of magnitude.

Figure 14. Semi-log rate of bacterial destruction at lethal temperature Source: (Warne, 1988)

The total time of heating is the sum of the time required to heat the SHP to the lethal temperature, and the optimum time of exposure. Because heating systems in vary in heating mechanisms, it becomes difficult to assess the effectiveness of a sterilization process using total time as a basis.

Instead, the value Fo is used. Fo is the cumulative effective lethal time, also called the process severity or sterilization rate, and is measured in minutes. With Fo values, a parameter has been set to comparatively assess the lethal effect of different sterilization processes. Fo values for common fish products like tuna and sardines are readily available in literature from various experimental measurements by different research bodies. Alternatively, many models that are based on thermal conductivity concepts are also available for the estimation of Fo values. (Bratt, 2010; Warne, 1988).

However, for all canning operations, empirical calculation of Fo values from equipment and material testing is still mandatory because overestimation of equipment performance and miscalculation of material thermal properties may cause inadequate thermal treatment. This, in turn, may allow the survival of harmful organisms and the accumulation of toxins. (Warne, 1988).

Overview of the Tuna Canning Process 3.2.3.

The procedure of canning fish has been established in the 1920’s. There have been many developments in the mechanization and sanitation of the process, but the principles and basic steps have not changed significantly over the years. The basic flow of the manufacturing process is shown in Figure 15 while the CPG manufacturing operation is shown in Figure 16.

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Figure 15. General Canned Tuna Process Flow Source: (Warne, 1988)

Figure 16. Overview of the CPG Canning Process Source: (CPG, 2010)

As shown above, the first operation in tuna canning is the receipt of either frozen or fresh tuna from landings by fishing boats. Frozen tuna are thawed then sent to butchering. Butchering involves removal of the heads and innards of the fish. The butchered fish are then stacked in wheeled racks that are rolled into an industrial steam pre-cooker. The precooked tuna are then sprayed with mist

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and upon cooling, are sent to a conveyor line with hundreds of stations for cleaning and skinning the cooked tuna. The cleaned tuna called loins, are mechanically cut, weighed and placed inside empty cans. Hot liquid medium is poured to form steam that exhausts the air from the top of the can, then hermetically sealed by machine. The sealed cans are placed in pallets which are rolled into the retort unit to get sterilized. The sterilized cans are cooled to room temperature and are sent to the labeling and numbering station. Figure 16 diagrams the current state of the tuna at different parts of the process.

For Figure 15 and Figure 16, the process flow remains exactly similar. The CPG flow is only more specific, showing the steps in adding liquid additives, quality check and metal detection. The general flow diagram shows the important inputs and outputs of each process.

Handling of Raw Tuna 3.2.4.

As soon as tuna is caught and slain, the tissues start to deteriorate and natural oils begin to oxidize and eventually cause the meat to turn rancid and lose nutrients. Oxidized omega 3 in fish produces such a foul odor that most people refuse to ingest it. On the other hand, the absence of blood flow starves the muscle tissues and causes the deterioration of proteins. Because both instances only happen at ambient temperatures, immediate freezing generally keeps the fish quality at a desirable level.

Additionally, the lack of an immune system allows bacterial contaminants to produce histamine, and other toxic compounds. This is especially true for tuna because of the presence of the high concentrations histidine in the meat. Histidine is converted to histamine by a bacterial enzyme called histidine decarboxylase. These bacteria are most active at ambient to warm temperatures;

hence, the further need for immediate and constant freezing.

Generally, tuna caught twelve hours away from the landing site have to be refrigerated in brine or blast frozen to retard the deterioration and oxidation of the fish and prohibit most harmful bacterial activity. Commercial ships, which are only allowed to fish away from the shore, have built in refrigeration systems that allow them to stay in the water for several days until maximum capacity is reached, all without sacrificing the quality of the fish. Municipal fishers are allowed to fish closer to the coast, thus, they are able to deliver fresh tuna without refrigeration.

Canneries receive both fresh tuna from the municipal fishers and frozen tuna from commercial ships and immediately perform a temperature and histamine test to assure raw material safety and quality.

Freezing, Storing and Thawing 3.2.5.

Depending on the process requirements, fresh tuna is either sent directly to pre-treatment or stored in a refrigerated and sanitized facility, while frozen tuna is thawed then sent to processing or stored and refrigerated. For all the reasons mentioned above, tuna that do not directly go to processing are frozen and stored in temperature maintained facilities. There are many methods of freezing tuna;

using chilled air or saltwater, freezing in blocks of ice, and blast freezing. Freezing methods are optimized to quickly bring the temperature of the tuna without extracting the moisture out.

The ideal temperature for storing oily fish such as tuna is -30^oC to inhibit oxidation of the fatty acids, and to preserve the quality and safety of the fish. Although it takes months for the fish meat to

deteriorate at this temperature, the cumulative effect of the gradual omega 3 oxidation will eventually turn the fish rancid. For this reason raw tuna stocks are best utilized at once and stored as short as possible. Management of frozen stocks in storage is therefore essential, and constant rotation of inventory should be observed.

Prior to processing, frozen fish from storage are thawed in sanitized, temperature controlled facilities. Temperatures are generally kept below 20^oC to prevent bacterial contamination, excessive dehydration and localization of heat. Sanitation is also chief concern because once the surface temperature rises, bacterial inoculation and activity become imminent. Common methods of thawing are air thawing, air blast thawing, water thawing, and integrated coking and thawing.

Air thawing means leaving the fish to thaw by itself while maintaining the correct temperature. Lag times in air thawing are usually too long and are impractical in tropical conditions due to high ambient temperatures. Moreover, the huge space requirement for massive scale operations translates to high air conditioning costs.

In air blast thawing, saturated air is circulated through a chamber to maintain a high temperature gradient with the surface of the fish. Air saturation is particularly important to eliminate the concentration gradient of moisture between the air and the fish, which would lead to eventual dehydration. Fish are lined in trolleys with racks to maximize air flow while saving space. The drawback of using air blast systems is that the inner portion of the fish remains cold while the surface has already thawed to a temperature that encourages deterioration. To complete the thawing process while avoiding the deterioration at the surface, the fish are placed in a chilled storage to equalize temperature before processing.

Water thawing is done by immersion in or spraying of chilled water. The advantage with water thawing is a more even temperature distribution through the cross section of the fish compared to air thawing methods. The high water requirement is only practical for areas with enough supply as the residual water from the process contains dissolved organic solids and bacterial contaminants and is hardly reusable.

There is no general time prescription for thawing tuna as initial temperatures, target temperatures and sizes vary greatly among processes.

Pre-Treatment 3.2.6.

Pre-treatment of fish includes physical preparations such as butchering and evisceration, and grading. Grading is done to homogenize the process feed in terms of fish type, size, and inlet temperature, while the purpose of butchering and evisceration is to remove the heads, tails and intestines, which smell unpleasant and are inedible.

Size grading is done by machine in specialized conveyors that have specific widths for the appropriate tuna sizes, and manually by weighing on a scale and using a length measuring device.

Generally, large yellowfin tuna at 3-6 feet from longliners stay in a separate process from that of medium sized skipjack at 1-2 feet from purse seiners.

Butchering and evisceration of large tuna is usually done by hand with the aid of cutting tools such as bandsaws and knives. It may also include cutting the meat into smaller manageable portions. On the other hand, sheer quantities of medium sized fish are difficult to carve by hand and are usually

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sent through a conveyor with a bandsaw attachment to remove the head and tails. Evisceration is usually done by hand afterwards.

Both steps may be done by machine, but the yield is significantly greater when done by hand. Hand working also makes inspection and quality check easier to accomplish. Low labor costs in developing countries also make it more practical and cost efficient to have pre-treatment done by hand. Throughout the process, it is important to keep proper sanitation of all surfaces, tools and hands to prevent the spoilage and contamination of the meat. Hygiene and sanitation prescriptions by the world health organization (WHO) and the food and agriculture organization (FAO) for the handling and treatment of raw fish are commonly applied.

A byproduct of this process is a substantial amount of heads, intestines and other unwanted material. This is commonly sent to an annex plant to be manufactured into fish meal, a product that returns income.

Pre-Cooking 3.2.7.

Pre-cooking of tuna is done to allow convenient cleaning and skinning of the meat, to evaporate some of the moisture from the fish and in some cases, add flavor and develop the texture. The ideal precooking method for tuna is steaming at 100-102^oC in atmospheric pressure because it is economical, produces even heating and does not dissolve as much nutrients away as boiling. A new method of pre-cooking is done in vacuum conditions to expand the meat pores and allow the penetration of steam. Vacuum pre-cooking has been observed to increase yield and minimize cooking time.

Atmospheric steam cooking is commonly done in an enclosed horizontal steam chamber, as illustrated in . Fish are first put in a chain of trolleys with holding racks. These racks are filled with tuna and the train of trolleys is rolled into the precooking chamber. The door is sealed until the steam treatment finishes. An alternative to the horizontal pre-cooking chambers is the box type steamer that accommodates a single but highly stacked trolley. Vertical steamers are now rarely used because of the inefficient steam circulation and its low holding capacity.

In contrast to atmospheric steam cooking, the system pressure in vacuum cooking is purposely lowered using pumps before the introduction of steam. Vacuum pre-cookers are usually designed in a similar way as horizontal steam pre-cookers to accommodate a large quantity of fish. In addition to expanding meat pores, the vacuum in the chamber also improves the circulation of steam.

The time of pre-cooking is primarily dependent on the initial temperature, target temperature and the size of the fish. To ensure the thorough cooking of tuna, a target backbone temperature is set usually at 50-70^oC. The temperature in the backbone indicates the temperature at the thickest and slowest heating portion of the fish meat. The usual cooking time for large fish is 8 hours and 1 hour for small fish.

In most plants, the fish are cooled through misting right after pre-cooking to reduce the possibility of bacterial infection at warm temperatures. Misting is used instead of quenching to avoid breaking the structure of the fish and losing soluble nutrients to the water.

Figure 17. Schematic diagram of a horizontal tune precooker Source: (JBT)

Skinning and Cleaning 3.2.8.

The cooked fish are sent to long conveyor lines with adjacent tables manned by designated fish cleaners. The objective of cleaning the cooked fish is to remove the skin, bones and black met that disrupt the flavor and texture of the product.

Figure 18. Cleaning and Skinning Station

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Similar to pre-treatment, skinning and cleaning involves the use of sharp tools such as knives.

Cleaning and skinning is done in a two way conveyor line with a series of side tables, as shown in Figure 15.

Workers at the skinning line pick the tuna from the conveyor, skin them and put them in baskets or trays and return them to the line. The workers from the cleaning line pick up the baskets, and remove the black meat on their tables and return the baskets to the conveyor.

Important considerations in cleaning the fish are to avoid contamination of the fish by particles from the tools, hands of the worker and the working surface. All surfaces of contact have to be remained sanitized when working.

Filling and Seaming 3.2.9.

Tuna filling and packing is usually done automatically using packing machines. In filling each can, the weight of the tuna content is always kept the same. However, this may also be done manually by pre-weighing on the tuna filling a top loading balance.

In another part of the process, the liquid medium and other ingredients are also prepared for filling.

After the can is filled with tuna, the prepared broth is also added to the can. The broth is maintained hot to create a pocket of steam above the filling of the can and avoid the inclusion of oxygen in the sealed product. It is also important to keep the filling hot because when a cold liquid is used, the

After the can is filled with tuna, the prepared broth is also added to the can. The broth is maintained hot to create a pocket of steam above the filling of the can and avoid the inclusion of oxygen in the sealed product. It is also important to keep the filling hot because when a cold liquid is used, the