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Sang Moo Kim
Department of Marine Food Science and Technology
Gangneung-Wonju National University
Republic of Korea
smkim@gwnu.ac.kr

ABSTRACT

Squid is a cephalopod of the order Teuthida, which comprises around 300 species over the world, but only four species in Korea. The world production of squid is estimated to be about 82,552 MT in 2012, but 187.8 MT (0.23%) in Korea. Like all other cephalopods, squid has a distinct tail (ear), bilateral symmetry, a mantle, and arms. Squid has eight arms arranged in pairs and two, usually longer, tentacles. Squid is a strong swimmer and certain species can "fly" for short distances out of the water. The main body mass is enclosed in the mantle, which has a swimming fin along each side. The skin is covered in chromatophores, which enables the squid to change color to suit its surroundings, making it practically invisible. Squid is one of the very important commercial fishes over the world and mainly utilized or produced as a sliced raw fish, dried, seasoned and smoked products, and fermented product, etc. For the processing squid products, fresh squid is eviscerated and washed, and then utilized as a raw material. As a result of processing, there is a lot production of processing wastes: viscera, ink, tail (ear), arm, pen, blood, milt and skin, etc., where some of them are utilized as a feed or fertilizer. Squid body (mantle) and tail are main raw materials for the manufacture of dried, seasoned and smoked products, and the fermented product. Therefore, tail, pen, skin, ink and blood are usually discarded as a processing waste, which results in serious environmental problem. Hence, the squid industry has been tried to reduce the squid waste in order to save the cost price and solve the environmental problem: skin for collagen and seasoning, ink for bioactive substance, pen for chitosan or fertilizer, viscera for fertilizer or fermentation additive (accelerator), and tail (ear) and arms for the fermented or seasoned product.

INTRODUCTION

Squid is a cephalopod of the order Teuthida, which comprises around 300 species over the world. Typically 4 species (Todarodes pacificus, cuttlefish, Mitra squid, Beka squid) of squid are caught in Korea. The world production of squid is estimated about 82,552 MT in 2012, but only 187.8 MT (0.23%) are produced from Korea. The majority are no more than 60 cm (24 in) long, although the giant squid may reach up to 13 meters (43 feet).

Like all other cephalopods, squid has a distinct tail (ear), bilateral symmetry, a mantle, and arms. Squid has eight arms arranged in pairs and two, usually longer, tentacles. Squids are strong swimmers and certain species can "fly" for short distances out of the water. The main body mass is enclosed in the mantle, which has a swimming fin along each side. These fins, unlike in other marine organisms, are not the main source of locomotion in most species. The skin is covered in chromatophores, which enables the squid to change color to suit its surroundings, making it practically invisible. The underside is also almost always lighter than the topside, to provide camouflage from both preys and predators.

Squid is one of the very important commercial fishes over the world and mainly utilized or produced as a sliced raw fish (Sashimi), dried, seasoned and smoked products, and fermented product (Jeot-gal), etc. For processing squid products, fresh squid is eviscerated and washed, and then utilized as a raw material. As a result of processing, there is a lot of production and processing wastes: viscera, ink, tail (ear), arm, pen, blood, milt and skin, etc., where some of them are utilized as feeds for aquaculture fishes (shrimp) and animals or fertilizers.

Squid body (mantle) and tail are the main raw materials for the manufacture of dried, seasoned and smoked products, and the fermented product. Therefore, tail, pen, skin, ink and blood are usually discarded to the ocean directly as processing wastes, which result in serious environmental problems. Fortunately, this throwing into the discard was prohibited officially in Korea in 2014.

Hence, the people in the squid industry have tried to reduce squid wastes in order to save the cost price and solve environmental problems: skin for collagen and seasoning, ink for bioactive substance, pen for chitosan or fertilizer, viscera for fertilizer or fermentation additive (accelerator), tail and arm for the fermented or seasoned product, and milt for bioactive compound, etc.

The production of squid is shown in Table 1. The total production of squid in 2008 was 183,090 MT and then decreased rapidly to 86,645 MT in 2009 and 66,698 MT in 2010. Since 2010, this increased gradually to 82,552 MT in 2012. The four species of squid: Todarodes pacificus, Mitra squid, Beka squid, and cuttlefish are produced in Korea. Total production in 2008 was 191.9 MT, while 187.8 MT in 2012, which fluctuated a little depending on environmental conditions such as water temperature, current, etc. Among four species, the Todarodes pacificus occupies most of the squid production.

The proximate composition and major components of squid are presented in Table 2. The contents of moisture, protein, lipid, and ash are 77.5, 19.5, 1.3, and 1.7%, respectively. Typically there is no carbohydrate concentration in squid.

PROCESSED FOOD

The total production of the processed squid in 2006 was 23,672 tons, where the dried squid was 13,019 tons, while 20,789 tons in 2011 with only 1,461 tons of the dried one becausethe surimi-based product was produced to 8,137 tons from only 557 tons in 2006 (Table 3). The seasoned/smoked and surimi-based squid are the two main products in the processed squid products.

Dried squid

The dried squid is usually consumed as a side dish eaten while drinking or served as snack between meals. For the manufacture of dried squid, they are usually sun-dried in the beach or shipped, and sometimes cold air-dried because it is difficult to dry during rainy and cold seasons. Nowadays, the semi-dried product is more attractive to the young generation because the dried one is too tough to chew. There are four different artificial ways of drying which are used for the manufacture of the dried squid products; hot air drying with hot air at 400-500oC, cold air drying with cold air at 10oC, vacuum drying, and spray drying.

Seasoned squid

There is a huge market for the seasoned product because it is more delicious and soft than the dried one. In manufacturing the seasoned squid product, fresh squid is eviscerated and washed with tap water. The squid body and head are peeled of the skin with a protease and seasoned with a seasoning sauce consisting of starch syrup, sugar, alcohol, MSG, salt, agar, etc. The seasoned squid is mainly consumed as a side dish for drinking and meals (Choi et al. 2012).

Smoked Squid

Squid body and tail (ear) are seasoned in the same way as the seasoned squid products and are then smoke-dried. The smoked squid is also consumed the same way as the seasoned one.

Fermented squid

There are two kinds of fermented squid products; Jeot-gal and Sik-hae.

Jeot-gal

Jeot-gal is a traditional Korean fermented seafood with a 10% salt concentration. The fermented squid is usually manufactured using only body and tail (ear). There is also similar product (Shiokara) in Japan. The squid body and tail (ear) are cut or sliced into 0.5 x 5 cm, seasoned with sauce, and then fermented. The fermented squid is consumed as a side dish for rice meal.

Sik-hae

Sik-hae is also a traditional fermented seafood with low salt concentration of 3-5%, where white fishes such as flounder (flatfish), Alaska pollock, skate, etc. are mainly used as a raw material. Sik-hae is manufactured by mixing the ingredients such as radish, grain (cooked rice or millet), red pepper, garlic, ginger, etc. and then fermenting, which is shorter fermentative periods (2-3 weeks).

Surimi-based squid

Global production of surimi in 2012 was 850,000 MT where Alaska Pollock surimi was only 170,000 MT due to the decrease in its production over the last decades. Topical fish surimi including Threadfin bream was 550,000 MT and giant squid one was 1,000 MT. Giant squid has not been used as a raw material for the manufacture of surimi-based product because of its strong fish smell due to CH4Cl and weak gel forming ability. In order to improve this inferiority, konjac flour and transglutaminase were added as a gel texture enhancer (Choi et al. 2012). Therefore, squid surimi-based product was successfully manufactured for commercialization. Nowadays, giant or general squid are used as a surimi raw material by 20-30% because Alaska pollock, a traditional raw material for surimi, which is very expensive due to low production.

Food additives

Enzymatic hydrolysis is a process in which enzymes facilitate the cleavage of bonds in molecules with the addition of the elements of water. It plays an important role in the digestion of food. Enzymatic squid hydrolysate was developed as a new functional food additive. Protease (Alcalase) decomposed the squid meat into low-molecular weight substances with functional activities; strong antioxidant activity, tyrosine inhibitory activity, ACE inhibitory activity, and cholesterol lowering effect (Kim et al. 2009). The squid protein hydrolysate contains the high amount of amino acids and nucleotides. Squid complex seasoning is comparable to commercial natural seasonings.

General foods

Sun-dae

Sun-dae is a traditional Korean food. Generally pork or cow intestines are used to pack the mixed ingredients such as cooked rice, cellophane noodle, cow or pork meat, mushroom, carrot, garlic, sugar, onion, soysauce, etc. Sun-dae originated from North Korea.

In the manufacture of Sun-dae, squid is defrosted and the guts are removed. Then the body and legs are separated and soaked in a seasoning liquid at 0 ~ 5 ºC for 3 hrs. After heat treatment at 100 ºC for 10 min, the rice is filled into the squid's body. After drying at 50 ºC for 1 hr, the squid is cooled and then vacuum packed. The packages are sterilized at 120 ºC for 50 min. The seasoning liquid usually consist of soy, grain, MSG, sugar, water, and licorice, kelp broth, etc.

Snack

Squid snack is usually manufactured for children. Squid snack with ink was once commercialized, but the practice stopped because squid ink hindered to make the squid snack (crunchy).

Steak

The squid meat is also used the manufacture of squid steak.

SQUID WASTES

Ink

Squid ink is composed of not only large amounts of melanin, but also proteins, lipids, glycosaminoglycans, muco-saccharides. Squid ink possesses a wide range of biological roles as it not only inhibits the activity of plasmin to promote thromboxane and elevates immunological competence to kill cancer cells to exert its anti-tumur effects, but it also has leukocyte-number elevating, antioxidant, antiradiation, antiretrovirus, and antibacterial properties.

Food ingredient

The squid ink is utilized as an ingredient in the manufacture of bread, confectionery, tofu, pasta (spaghetti), curry, potato chips, candies, snacks, kimchi (Kim 2009), sauces (Kim 2008), noodles (Kyoung et al. 2009), etc.

Peptide

The squid ink was used as a raw material in the manufacture of functional peptide. The squid ink peptide sequence was identified as Gln-Pro-Lys. It significantly inhibited the proliferation of DU-145 cells, in which its activity was dose-dependent. This research showed the effect of sepia (one of squid) ink oligopeptide which could inhibit on the growth of cancer cell (Fang et al. 2011). Therefore, the squid ink peptide can be commercialized as functional peptide agent.

Pen

There are two types of chitin being precursor of chitosan. ?-Chitin, which is usually extracted from shell of shrimps or crabs, has dense crystal structure with low solubility at organic solvent. On the contrary, ?-chitin from squid pen has relatively loose crystal structure. Chitin (chitosan) is usually extracted with organic solvent. Because of this, squid pen is usually discarded as an industrial waste (Pack et al. 2008).

Chitosan is derived from chitin by removing acetyl group in it to enhance bio-availability and used as a bioactive polymer. Chitosan and its oligomers are effective in reducing LDL-cholesterol level in liver and blood. It is also known to possess antitumor, antioxidant, antihypertension, and antimicrobial activities, etc.

Squid chitosan was used as an ingredient for the manufacture of functional tofu to remove soybean's bitter flavor. There is no significant difference of whiteness of tofu when compared with the control. Squid chitosan tofu has better hardness, strength, cohesiveness, springiness, gumminess than the control.

Skin

Collagen

Squid skin is a good source in the manufacture of collagen. The inner and outer squid shell is used as a raw material for collagen and products such as cosmetic ingredient.

Taurine

Taurine, or 2-aminoethanesulfonic acid, is an organic acid widely distributed in animal tissues. It is a major constituent of bile and can be found in the large intestines. It accounts for approximately 0.1% of the total human body weight. Taurine has many fundamental biological roles such as conjugation of bile acids, antioxidation, osmoregulation, membrane stabilization and modulation of calcium signaling. It is essential for cardiovascular function, and development and function of skeletal muscle, the retina and the central nervous system. Taurine is unusual among biological molecules in being a sulfonic acid, while the vast majority of biologically occurring acids contain the more weakly acidic carboxyl group. While taurine is sometimes called an amino acid, it is indeed an acid containing an amino group (Korea Taurine Study Group. 2003).

Milt

Protamine, a cationic peptide derived from ?sh (salmon) milt (spermatic cells), is used in medical applications as a carrier for injectable insulin, a heparin antagonist and, more recently, as an antibacterial ingredient in some food products.

The biofunctional activities of squid milt hydrolysate were investigated for its commercialization. Squid milt hydrolysate showed strong antioxidant activity including hydrogen peroxyl radical and super anion radical scavenging activity with an IC50 values of 62.68 and 85.97 µg/mL, respectively. Squid milt hydrolysate also possessed high MMPs and elastase inhibitory activities with an IC50 of 67.21 and 178.81 µg/mL, respectively. Therefore, squid milt hydrolysate may be useful as a biofunctional peptide for the treatment of anti-aging and enzyme (MMPs and elastase)-related diseases (Wahyudi 2013).

Liver

Squid liver oil is an abundant source of polyunsaturated fatty acids, especially EPA and DHA. The polyunsaturated fatty acids are oxidized easily during storage and processing. There are many methods such as spray drying, coating, and extrusion process, etc. to produce the fish oils, where spay drying is known to be the most economical. Recently encapsulation process was introduced to produce the squid liver oil: the microencapsulated squid oil was achieved by spray drying method in which the equilibrium moisture content had higher values at lower storage temperatures, and higher water activity (Hwang et al. 2008).

Viscera

Squid viscera like fish viscera are non-edible part produced in large quantities in Korea by the fish processing industry as a by-product. The disposal of these by-products is a major problem for organized industries as well as for instant processing in market places.

Fermentation enhancer

Squid viscera were used in the manufacture of fish sauce as a fermentation enhancer (Choi et al. 2011). The addition of squid viscera accelerated the digestion of Alaska pollock meat (Kim 1999).

Oil

The oil obtained from the squid viscera consists of multi-compounds such as EPA, DHA and other valuable polyunsaturated fatty acids. Polyunsaturated fatty acid such as EPA and DHA is one of the functional components that prevent myocardial infarction and cerebral thrombosis to be converted into prostaglandin in vivo as well as its physiological function such as improving learning ability, preventing deteriorating eyesight, myocardial infarction and cerebral thrombosis, etc (Kang et al. 2005).

The viscera of squid include lots of fats and vitamin B, minerals compared to common fish. Especially, the fat content is high 30-40% which contains EPA and DHA more 40% than squid liver oil (Salim Uddin et al. 2009).

Lecithin

Lecithin is a sticky fatty substance composed mainly of phospholipid mixtures with small amount of glycerides, neutral lipids, and other suspended matter. Lecithin, which occurs in egg yolk, animal and plant tissues, is used for its emulsifying properties in the food, pharmaceutical and cosmetic industries. Pharmacological use of lecithin is included in treatments for hypercholesterolemia, neurologic disorders and liver ailments. Lecithin has also been used to modify the immune system by activating specific and nonspecific defense systems. The main commercial sources of lecithin are soybeans and egg yolk. To date, the soybean is the most frequently used and studied source of lecithin. Lecithin from marine sources has several valuable nutritional benefits. Marine phospholipids are valuable resources that can be applied to diverse areas such as nutrition, pharmacy, and medicine as well as basic research because they contain high levels of ?-3 fatty acids.

Lecithin is primarily extracted with solvents such as diethyl ether, hexane, chloroform, and ethanol. Acetone is also used to precipitate lecithin from other lipids. However, some of these solvents are considered undesirable because of environmental and health concerns. Currently, an environmentally friendly solvent, supercritical carbon dioxide (SC-CO2), is widely used to extract nonpolar lipids with lipid-soluble bioactive compounds from different sources. Further, SC-CO2 extraction provides some advantages over conventional extraction processes because carbon dioxide (CO2) is nonflammable, nontoxic, inert to most materials, inexpensive, and can be used under mild operational conditions (Salim Uddin et al. 2011).

Enzyme

Enzymes have been used as processing aids in various food related industries for a long time. In general, enzyme technology has evolved to become an integral part of the food industry. Proteases execute a large variety of functions and have important biotechnological applications. Lipolytic enzymes are currently attracting an enormous attention because of their biotechnological potential. They constitute the most important group of biocatalysts for biotechnological applications. Some of the industrially important chemicals manufactured from fats and oils by chemical processes could be produced by lipases with greater rapidity and better specificity under mild conditions. Amylases are used for preparation of sizing agents in textile industry, preparation of starch pastes for use in paper industry and removal of spots in laundry. Squid viscera are rich source of various enzymes that may have some unique properties of interest forboth basic research and industrial applications.

Tail (ear)

Squid tail is one part of squid with tough texture, which is also called as squid ear. Because texture is not better than the body of squid, people tend to dislike eating directly. Therefore, squid tail is usually used as a raw material for the manufacture of the seasoned or other processed products.

Arm

Squid arm possessing sucker is a part to be able to adhere and move squid. Because of more tough texture than body part, people tend to avoid eating it. Therefore, it is discarded as a processing waste sometimes except for the dried or seasoned product (Kim 2008).

CONCLUSION

Squid is one of the important commercial fishes over the world. Hence, there are various processed squid products such as the dried, smoked, seasoned, and fermented products. Consequently, there are a lot of processing by-products and waste which results in enormous environmental problem. Therefore, these by-products and waste should be treated and utilized. Fortunately, there are many attempts to reduce and utilize the squid waste including by-products. It is expected that the squid waste will not be a big problem if government and industry take care of them seriously and continuously.

REFERENCES

  • K.D. Choi, U.Y. Park and I.S. Shin. 2012. Microbial contamination of seasoned and dried squid Dosidicus gigas during processing. J Korean Food Sci Technol. 44(4):422-427
  • S.H. Choi and S.M. Kim. 2012. Quality properties of giant squid (Dosidicus gigas) surimi-based product manufactured with Amophophallus konjac flour. J Korean Soc Food Sci Technol. 41(7):975-981
  • S.M. Kim, K.S. Choi and N.H. Cho. 2009. Hydrolysed functional substances from meat of squid using protease and manufacturing method thereof. Korea Patent. 10-2009-0028165
  • H.S. Kim. 2009. Kimchi using sepia and soy sauce and method for manufacturing the same. Korean Patent. 10-2009-0079541
  • J.S. Kyoung and D.S. Cha. 2009. The functional dangmyen with squid ink and its preparation. Korean Patent. 10-2009-0029986
  • M.J. Kim. 2008. India ink soy sauce additive of uncurdled bean curd or bean curd stew, and its manufacturing method. Korean Patent. 10-2008-0108782
  • D.G. Fang, F.F. Huang, Z.S. Yang, Y.U. Di and Y.F. Yang. 2011. Anticancer activity of an oligopeptide Isolated from hydrolysate of Sepia Ink. Chin J Nat Med. 9(2):0151-0155
  • S.H. Park, O.S. Kim, S.Y. Cho, G.W. Kim, J.S. Kim, H.K. Kim, H.Y. Ahn and K.W. Heo. 2008. A method for preparing soybean curd using ?-chitosan. Korean Patent. 10-0840547
  • Korea Taurine Study Group. 2003. The Mystery of Taurine. Woosuk Publishers. p20.
  • S.H. Hwang and K.S. Youn. 2008. Sorption characteristics of microencapsulated squid liver oil powder by spray drying. Food Engineering Progress. 12(3):170-175
  • S.H. Choi and S.M. Kim. 2011. Quality properties of fermented squid seasoning manufactured with fermentation accelerator. Korean J Food Sci Technol. 43(3):334-340
  • S.M. Kim. 1999. Effect of squid viscera on the fermentation of Alaska pollack scrap sauce. J. Food Sci. Nutr. 4(2):103-106
  • K.Y. Kang, D.H. Ahn, G.T. Wikinson and B.S. Chun 2005. Extraction of lipids and cholesterol from squid oil with supercritical carbon dioxide. Korean J Chem Eng. 22(3):399-405
  • M. Salim Uddin, H. Kishimura, H.M Ahn and B.S. Chun. 2009. Comparative study of digestive enzymes of squid (Todarodes pacificus) viscera after supercritical carbon dioxide and organic solvent extraction. Biotechnology and Bioprocess Engineering. 14:338-344
  • M. Salim Uddin, H. Kishimura and B.S. Chun. 2011. Isolation and characterization of lecithin from squid (Todarodes pacificus) viscera deoiled by supercritical carbon dioxide extraction. Food Chemistry. 76(2):350-354
  • E.J. Kim. 2008. Process of manufacture of seasoned squid leg. Korea Patent. 10-0013138
  • Wayudi. 2013. Biofunctional Actibities of Hydrolysates from Salmon Protamine and Squid Milt. MS Thesis. Gangneung-Wonju National University, Korea.


Index of Images

  • Table 1 Squid production

    Table 1 Squid production

  • Table 2 Squid composition

    Table 2 Squid composition

  • Table 3 Processed squid production in Korea

    Table 3 Processed squid production in Korea

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