**1. Introduction**

18 Recent Advances in Plasticizers

Kaytan, H., Bonnet, M. (2008), *New, innovative PVC plasticizers: N-alkyl-pyrrolidones*, in The 10th International PVC Conference, IOM Communications Ltd (2008), p. 305 Kaytan, H., Bonnet, M. (2008), *N-alkyl pyrrolidones as innovative PVC plasticisers*, Plastics,

Bonnet, M., Kaytan (2008), H., *Flexible Even at Very Low Temperatures*, Kunststoffe

Frank, A. & Knoblauch, M. (2005). *Technologiestudie zur Verarbeitung von Polyvinylchlorid (PVC),* commissioned by PlasticsEurope Deutschland e.V. and AGPU Ansell, J.M. & Fowler, J.A. (1988). The acute oral toxicity and primary ocular and dermal

Hohenberger, W. (2001). In: *Plastics Additives Handbook*, 5th ed., Zweifel, H. ed., 901, Hanser,

Third National Report on Human Exposure to Environmental Chemicals, U.S. CDC, July

H.R. 4040 - 110th Congress (2007): Consumer Product Safety Improvement Act of 2008,

irritation of selected N-Alkyl-2-Pyrrolidones, *Food and Chemical Toxicology*, Vol.26,

Rubber and Composites, 37 (2008) 9/10, p. 411

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No.5 (1988) p. 475

Munich

2005

**6. References** 

The applications of jumbo squid by-products as plasticizer agents have been never received much attention, even though there are several studies in which the properties of the catch and processing discards for productions of films have been reported.

The principal by-products that result from the catch and processing of seafood include viscera, heads, cut-offs, bone, and skin. Therefore, a large and considerable volume of solid waste is obtained, constituting an important source of environmental contaminants unless efforts for their recovery are attained (Arvanitoyannis & Kassaveti, 2008). In the case of squid, one the largest known mollusks, the global capture represents no more than 2% of the total catch. However, by-products from squid processing, which include heads, viscera, backbones or pens, ink, skin, unclaimed fins, mantles, and tentacles, may represent up to 60% of the whole weight. In addition, from all the different anatomical squid components regarded as by-products only the beak and pen are not edible. Thus, since most of the squid is not used, its by-products also pose an environmental issue for this fishery, especially in areas where it is harvested the most. The valuable and profitable components that these byproducts contain include among others chitin, chitosan, collagen, and gelatin (Kim & Mendis, 2006; Shahidi, 2006).

Collagen is a fibrous protein responsible for structural sustaining of several animal tissues, being the main protein present in skin, bones, tendons, cartilages, and teeth. In the case of mammalians, it accounts for about 20-30% from the total body protein (Quereshi et al., 2010). The term collagen derives from the Greek word *kolla* which means glue and was defined as "that constituent of connective tissue which yield gelatin on boiling" (Oxford University, 1893). Nowadays, although collagen is most of the time referred as to a single item, in fact it is a heterogeneous group of at least 19 different molecules which have a unique triple-helix configuration that forms very strong fibers. Collagen is characterized by its unusual amino acid composition, in which glycine and proline account for about 50% of them. Indeed, each polypeptide called α chain consists of a repeated sequence of the triplet Gly-X-Y,

By-Products From Jumbo Squid (*Dosidicus gigas*): A New Source of Collagen Bio-Plasticizer? 21

Squid or calamari are cephalopods which comprises a group around 300 species, being the jumbo squid or *Dosidicus gigas* one of them (Figure 1). Jumbo squid is a member of the flying squid family, Ommastrephidae (Nesis, 1985), and are known to eject themselves out of the water to avoid predators. Jumbo squid are the largest known mollusks and the most abundant of the nektonic squid. They can reach up to 2 m in length and weigh up to 45 kg. This specie is characterized by its large, tough, thick-walled mantle and long tentacles. These organisms are aggressive predators. Jumbo squid earned the nickname of "red devils" because of their red hue when hooked, which they use to camouflage from predators in deep waters where most animals cannot see the red color. This coloration is due, like other cephalopods, to the presence of chromatophores. Also, squid possess the ability to squirt ink

Jumbo squid is an endemic species to the Eastern Pacific, ranging from northern California to southern Chile and to 140 degrees W at the equator. Exploratory commercial fishing for *Dosidicus gigas* began in the 1970s off the Pacific coast of America. The catches of this fishery increased from 14 tons per year in 1974 to over 250,000 tons in 2005. Since then, it has become an extremely important fisheries resource in the Gulf of California, Costa Rica Dome

The commercial fishery of jumbo squid consists of a multinational jigging fleet, which fish at night using powerful lights to attract squid (Waluda et al., 2004). The caught of this organism depends of the season and the region. In the Gulf of California for example, this organism enter to the Gulf from the Pacific in January, to reach their northernmost limit by April, and to remain in the central Gulf from May through August; the highest aggregations of specimens are found along the western (Baja California) coast. From September squids appear to migrate onward the eastward to the Mexican mainland coast and then southwards, to the Gulf back into the Pacific (Ehrhardt et al., 1983). Whereas, in Peruvian waters the highest squid concentrations occur along the coast of northern Peru, from Puerto Pizarro to Chimbote, with low to medium squid concentrations off Pisco and Atico. The highest catches occur during autumn, winter, and spring, since squid tend to be dispersed in

Although the growth of this fishery has been spectacular, great contrasts have characterized it. Of the total catch, a major portion remains unused or minimally used. In Mexico for instance, no more than 11% of the resource is used for human consumption, regardless of its low price and high nutritional value (De la Cruz et al., 2007). Moreover, only the mantle

**2. Characteristics of jumbo squid as fishery** 

as a defense mechanism (Nigmatullin et al., 2001).

Fig. 1. Jumbo squid (*Dosidicus gigas*).

and Peru (Marakadi et al., 2005).

summer (Taipe et al., 2001).

where X and Y are often proline and hydroxyproline. Each collagen type varies in the length of the helix and the nature and size of the non-helical portions (Lee, C. R. et al., 2001).

Collagen *per se* is regarded as one of the most useful biomaterials. The excellent biocompatibility and safety due to its biological characteristics, such as biodegradability and weak antigenicity, have made collagen one of the primary resources in medical applications. In addition, other uses include gelatin production, nutritional supplements, sausage casings, and in cosmetic products it claims anti-ageing benefits (Kim & Mendis, 2006; Lee et al., 2001).

Recently, the use of fish collagen in the manufacture of biopolymer films has been reported. Collagens from different species of fish have been extracted using acetic acid, which were used later to produce biodegradable films (Venugopal, 2009). Studies on the production and characterization of films using fish gelatins are quite recent, and all fish gelatins have been observed to exhibit good film-forming properties, yielding transparent, nearly colorless, water soluble, and highly extensible films (Avena-Bustillos et al., 2006; Benjakul et al., 2006; Carvalho et al., 2008; Gomez-Guillen et al., 2007; Zhang et al., 2007).

On the other hand, chitosan is a polysaccharide that is produced by deacetylation of naturally occurring chitin, and it has a great potential for a wide range of applications due to its versatile properties, such as in food and nutrition, biotechnology, material science, drugs and pharmaceuticals, agriculture and environmental protection, and recently in gen therapy as well (Venugopal, 2009; Dutta et al., 2009; Shahidi et al., 1999; Shahidi et al., 2002). Nonetheless, pure chitosan, as a film material, does not form films with adequate mechanical properties due to its low percentage of elongation (Butler et al., 1996). For this reason, one of the current trends in designing biodegradable materials for packaging is to combine different biopolymers (Bawa et al., 2003; Bertan et al., 2005; Colla et al., 2006; Le-Tien et al., 2004; Lee et al., 2004; O'Sullivan et al., 2005; Tapia-Blacido et al., 2007; Yu et al., 2006).

Chitin and chitosan belong to a group of natural polymers produced by the shells of crab, shrimp, and lobster. In addition to be nontoxic, chitin and chitosan are inexpensive, biodegradable, and biocompatible. Regarding to film-forming properties, chitosan is more versatile as compared to its precursor chitin. Chitosan has the capacity to form semipermeable coatings which, when used in foods, prolong their shelf life by acting as barriers against air and moisture (Agulló et al., 2004).

Furthermore, since collagen in acid solution exhibited positively charged groups, it has a molecular interaction with chitosan with high potential to produce biocomposites (Liang et al., 2005; Lima et al., 2006; Sionkowska et al., 2006; Wang et al., 2005; Wess et al., 2004), acting as a possible plasticizer agent.

In the first part of this chapter, the most important characteristics of jumbo squid as fishery, as well as the most recent scientific literature dealing with chitosan and collagen films made from seafood by-products, are reviewed. In the second part, thermal, mechanical and morphological properties of chitosan and acid soluble collagen (ASC) produced by casting films are discussed. As-cast films dried in relation to the molecular interaction of ASC by using differential scanning calorimetry (DSC), scanning electron microscope (SEM), and infrared spectroscopy are also discussed in this chapter. Thermal properties by DSC, SEM images, mechanical properties, water vapor barrier properties, and water solubility characteristics of the chitosan/ASC blends are analyzed as a function of ASC content in terms of the individual properties of chitosan and ASC.
