Effects of combining microbial transglutaminase and high pressure processing treatments on the mechanical properties of heat-induced gels prepared from arrowtooth flounder (Atheresthes stomias) Rocı ´o M. Uresti a , Gonzalo Velazquez a,b , Manuel Va ´zquez a,c , Jose ´ A. Ramı ´rez a, * , J. Antonio Torres b a Department of Food Science and Technology, Universidad Auto ´ noma de Tamaulipas, U.A.M. Reynosa-Aztla ´ n, Apdo. Postal 1015, Reynosa, Tamaulipas, 88700 Mexico, USA (Mail address: PMB 374, 501 N. Bridge Street, Hidalgo, TX 78557, USA) b Food Process Engineering Group, Department of Food Science and Technology, Oregon State University, 100 Wiegand Hall Corvallis, OR 97331-6602, USA c A ´ rea de Tecnologı ´a de los Alimentos, Departamento Quı ´mica Analı ´tica, Universidad de Santiago de Compostela, Escuela Polite ´cnica Superior, Campus de Lugo, 27002 Lugo, Spain Received 30 August 2004; received in revised form 1 November 2004; accepted 1 November 2004 Abstract The objective of this study was to evaluate the effect of setting conditions (25 °C for 2 h or 40 °C for 30 min) and combining of microbial transglutaminase (MTGase) and high pressure processing (HPP) on the mechanical properties of heat induced gels obtained from paste from arrowtooth flounder (Atheresthes stomias). Treatments included fish paste control without added MTG- ase, fish paste incubated with MTGase but not pressurized (MTGase + cooking), fish paste incubated with MTGase and pressurized at 600 MPa for 5 min (MTGase + HPP + cooking) and fish paste pressurized at 600 MPa for 5 min and incubated with MTGase (HPP + MTGase + cooking). The controls and the treated samples were then subjected to one of two thermal treatments: 90 °C for 15 min or 60 °C for 30 min before cooking at 90 °C for 15 min. Samples of fish paste heated at 60 °C before cooking could not be used to prepare gels for texture profile analysis (TPA). TPA showed that pressurization improved the mechanical properties of gels made from paste treated with MTGase and set at 25 °C. The opposite was observed for samples set at 40 °C. Setting at 40 °C appeared to induce proteolytic degradation of myofibrillar proteins. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: High pressure; Arrowtooth flounder; Atheresthes stomias; Setting; TPA; Proteolysis 1. Introduction Arrowtooth flounder (Atheresthes stomias) is the most abundant fishery resource in the Gulf of Alaska and even greater than Alaskan Pollock (Theragra chal- cogramma)(Regenstein, 2004). However, it has low commercial value because its flesh texture degrades dur- ing heating. Efforts to improve the commercial value of this species have been reported recently (Uresti, Vela ´z- quez, Ramı ´rez, Va ´zquez, & Torres, 2004a, 2004b). Many fish species show protein degradation during heating, a phenomenon extensively studied in kam- aboko manufacture, and called ‘‘modori’’. Myosin, the myofibrillar protein responsible for functional and 0308-8146/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2004.11.005 * Corresponding author. Tel.: +34 982 285 900; fax: +34 982 241 835. E-mail addresses: vazquezm@lugo.usc.es (M. Va ´zquez), ramirez@ uat.edu.mx (J.A. Ramı ´rez), j_antonio.torres@oregonstate.edu (J.A. Torres). www.elsevier.com/locate/foodchem Food Chemistry 94 (2006) 202–209 Food Chemistry