Use of amidated low methoxyl pectin to produce fish restructured products R.M. Uresti a , N. Lo ´pez-Arias a , J.J. Gonza ´lez-Cabriales a , J.A. Ramı ´rez a, * , M. Va ´zquez a,b a Unidad Acade ´mica Multidisciplinaria, Universidad Auto ´noma de Tamaulipas, Reynosa Aztla ´n, Apartado Postal 1015, Tamaulipas 88700, Mexico b A ´ rea de Tecnologı ´a de los Alimentos, Escuela Polite ´cnica Superior, Departamento de Quı ´mica Analı ´tica, Universidad de Santiago de Compostela, Campus de Lugo, 27002 Lugo, Spain Received 17 February 2002; revised 28 March 2002; accepted 10 May 2002 Abstract Recently, amidated low methoxyl (ALM) pectin has been shown to improve functional and textural properties of surimi. The objective of this work was to determine the effect of ALM pectin on fish pastes and functionality of restructured fish products. Whole muscle of sole (Cyclopsetta chittendenii ) was used to obtain solubilized pastes with 2.5% salt and 0 (control), 1, 2, 3 or 5% ALM pectin. Changes in firmness, consistency, expressible water contents and colour parameters (L p , a p , b p , chroma and hue) were measured in pastes. Fish gels were obtained by incubating pastes at 40 8C for 30 min, followed by 90 8C for 15 min. Changes on breaking force, deformation and gel strength of restructured products were measured. ALM pectin decreased significantly (P , 0.05) firmness and consistency of pastes when added at 1%. Increases in both parameters were observed using higher ALM pectin levels. Adding ALM pectin to the paste increased the yellowness and redness (P , 0.05) according with a p and b p values. ALM pectin improved significantly (P , 0.05) breaking force and gel strength, and decreased the content of expressible water when added at 1 or 2%. Higher level of addition decreased significantly all mechanical properties. Results obtained indicated that ALM pectin at 1% could be employed to improve water holding capacity and mechanical properties of restructured fish products. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Amidated low methoxyl pectin; Restructured products; Cyclopsetta chittendenii 1. Introduction Introducing of the surimi technology to occidental countries has allowed a better understanding of the biochemistry of fish muscles and the physicochemical behaviour of proteinaceous matrix during the forming of gels. Gelling is a functional property that involves three main steps in muscle protein systems: solubilizing with 2– 3% salt, heat denaturation of proteins (50–90 8C) and protein aggregation. The origins of earlier enigmatic ‘modori’ and ‘setting or suwari’ phenomena have been elucidated. Fish species of Gulf of Mexico show the setting phenomenon (Morales, Ramı ´rez, Vivanco, & Va ´zquez, 2001) and it can be induced by adding microbial transglu- taminase (Ramı ´rez, Rodriguez-Sosa, Morales, & Va ´zquez, 2000; Ramirez, Santos, Morales, Morrissey, & Va ´zquez, 2000). Some additives such hydrocolloids have been proposed to improve mechanical and functional properties of surimi and restructured fish gels (Gomez-Guille ´n, Borderı ´as, & Montero, 1997; Lee, Wu, & Okada, 1992; Park, 2000; Ramı ´rez, Barrera, Morales, & Va ´zquez, 2001). Recently, it was found that adding amidated low methoxyl (ALM) pectin improves mechanical and functional proper- ties of surimi and fish restructured gels (Barrera, Ramı ´rez, Gonza ´lez-Cabriales, & Va ´zquez, 2002). However, the mechanism involved has not been elucidated. Food hydrocolloids could modify the gelling capacity of salt to solubilize myofibrillar proteins. This influences the formation of the continuous matrix by interacting with the ingredients of the muscle paste (mainly water and proteins) during the formation of the paste or during the heat-induced formation of the continuous matrix. Some additives are considered to interact with the proteins to form a more structured system, while others acts as fillers just binding water and modifying the viscosity of the system (Lee et al., 1992). The objective of this work was to determine the effect of adding ALM pectin during preparation of restructured fish 0268-005X/03/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S0268-005X(02)00049-8 Food Hydrocolloids 17 (2003) 171–176 www.elsevier.com/locate/foodhyd * Corresponding author. Address: Unidad Acade ´mica Multidisciplinaria, Universidad Auto ´noma de Tamaulipas, Reynosa Aztla ´n, Apartado Postal 1015, Tamaulipas 88700, Mexico. Tel.: þ52-899-230622; fax: þ 52-899- 213340. E-mail address: ramirez@qui-rey.uat.mx (J. A. Ramı ´rez).