Protein changes in shell and epidermis of shrimp (Pandalus borealis) after maturation on ice or in salt (original) (raw)

Enzyme-assisted peeling of cold water shrimps ( Pandalus borealis )

Innovative Food Science & Emerging Technologies, 2018

An enzymatic method to facilitate the peeling of cold water shrimps (Pandalus borealis) was developed. The protease solutions were used to mature the shrimps to promote shell-loosening prior to peeling. The efficiency of peeling enzyme-treated shrimps was evaluated by a new quantitative measurement based on the tensile force, presented as a peelability profile. It was found that enzymatic maturation efficiently improved the peelability of shrimps. The factors affecting the peelability of the enzyme-matured shrimps were the type of enzyme, enzyme concentration and maturation duration, while changes in pH had no impact. Maturation of shrimps in solutions of the endoproteases Endocut-01L (180 NU/g) and Endocut-03L (60 U/g) and the exoprotease Exocut-A0 (100 U/g) resulted in better peelability compared to shrimps matured in endoprotease Tail21 (65 U/mL) and 2% NaCl. A combination of 0.25% Endocut-03L and 0.25% Exocut-A0 for 20 h resulted in the best peeling of shrimps (100% completely peeled shrimps, 3 mJ/g work and 89% meat yield). Reuse of the enzyme solution was possible due to a 95% retention rate of proteolytic activity after two 20-h cycles of maturation. The studied enzymatic maturation offered a better shrimp product with respect to texture and color in comparison with an industrial brine-matured reference, i.e.,~22% higher redness and~31% higher hardness. Industrial relevance: Enzymatic maturation is an attempt made as a pre-treatment to facilitate the removal of the shell from meat of shrimp. This approach would benefit the shrimp processing industry by 1) enhancing peeling efficiency that includes least efforts to remove the shell, high rate of completely peeled shrimps and high meat yield; 2) shortening the duration of maturation but still sufficiently loosening the shell for machine peeling; 3) performing as a chemical-free peeling aid, which may increase the preference of consumers over chemical compounds; and 4) being environmentally friendly since disposal of enzyme waste is harmless to the environment. 1. Introduction Cold water shrimp, Pandalus borealis, is one of the most commercially important species of wild shrimps in the world (Myrset, Barletta, Di Felice, Egaas, & Dooper, 2013). The shrimp is diversely named as Northern shrimp (FAO), pink shrimp or deep-water prawn (UK, Canada and USA) and deep-sea prawn (Canada) (Holthuis, 1980). P. borealis is caught mainly in the North Atlantic, especially around Greenland, the Gulf of St. Lawrence, the Bay of Fundy, the Gulf of Maine and North Pacific (Holthuis, 1980). The global catch of P. borealis constantly decreased from around 446,909 tons in 2004 to around 260,488 tons in 2015 according to (FAO, 2017). Research in shrimp processing for improvements in efficiency, yield and quality is, therefore, important for economic sustainability. Shell-loosening is an important step in processing of peeled shrimps. Structurally, the shell is tightly attached to the epidermis by attachment fibers (intracuticular fibers), and the epidermis is securely attached to the muscle by extensive interdigitation (Talbot, Clark Jr, & Lawrence, 1972). Thus, a pre-treatment is needed in order to loosen the muscleshell attachment prior to peeling. Such pre-treatment is called maturation process. The current maturations of shrimps on ice and/or in brine (typically NaCl or NaCl with phosphates) solution for several days are the most common practices to facilitate the separation of the edible meat from the shell in the shrimp industry (Dang et al., 2018). Nevertheless, shrimp is highly perishable, and such long times of maturation may lead to diminish the meat quality e.g., freshness, texture, color, flavor. The intrinsic enzymes in the shrimp and enzymes from microorganisms during post-mortem storage are accountable for enhancing shell removal (Crawford, 1980). Addition of enzymes from external