Evaluation of frankfurters obtained from croaker (Micropogonias furnieri) surimi and mechanically deboned chicken meat surimi-like material

Abstract

In order to develop a healthy low-fat frankfurter-type sausage, different levels of surimi-like material prepared from mechanically deboned chicken meat (MDCM) and whitemouth croaker (Micropogonias furnieri) meat surimi were employed in five different recipes in the percentage ratios of 100/0, 70/30, 50–50, 30/70, and 0/100, respectively. The functionality of both fish and chicken protein concentrates was evaluated based on texture analysis (breaking force, deformation, gel strength and shear force). Growth kinetics for aerobic bacteria were analyzed using the modified Gombertz model. Shelf-life was determined based on microbiological counts and sensory analysis on acceptance tests. Surimi source reflected in the physical properties of the frankfurters. Addition of MDCM surimi-like material to sausage favored greater shear force, breaking force, and gel strength. On the contrary, the increasing levels of croaker surimi reduced rheological parameter values. Deformation presented no evident correlation between the formulations and with other textural properties. Average of textural properties obtained during storage where 2.29 ± 0.16 N for breaking force, 0.74 ± 0.02 cm for deformation, 1.69 ± 0.14 N cm for gel strength, and 14.2 ± 0.8 N for shear force, for frankfurters prepared with MDCM surimi-like material. Frankfurters presented an average shelf-live of 42 days at 4°C. Mathematical models had good correlation, and may be utilized for predictive applications.

Con el fin de desarrollar una salchicha sana con bajo contenido de grasas, diferentes niveles de producto tipo surimi a base de carne de pollo mecánicamente deshuesada (CMDP) y surimi de carne de corvina (Micropogonias furnieri) fueron empleados en cinco recetas diferentes, en la relación porcentual de 100/0, 70/30, 50/50, 30/70 y 0/100. La funcionalidad de los concentrados de proteínas de los pescados y pollo se evaluó sobre la base de análisis de texturas (fuerza de corte, deformación, fuerza de gel y fuerza de rotura). Cinéticas de crecimiento de las bacterias aeróbicas fueron analizados utilizando el modelo de Gombertz modificado. La vida útil se determinó en base a los recuentos microbiológicos y análisis sensorial en las pruebas de aceptación. La fuente de surimi se reflejó en las propiedades físicas de los embutidos. La adición de producto tipo surimi de CMDP a la salchicha favoreció una mayor fuerza de rotura, corte y fuerza de gel. Por el contrario, los crecientes niveles de surimi de corvina redujeron los valores de los parámetros reológicos. Sin embargo, las propiedades de textura de las salchichas no han significativamente aumentado o disminuido durante el período de almacenamiento. Los embutidos presentaron una vida útil promedia de 42 días a 4°C. Deformación presentó una correlación no evidente entre las formulaciones y con otras propiedades de textura. La media de las propiedades de textura obtenidas durante el almacenamiento fueron 2,29 ± 0,16 N para fuerza de corte, 0,74 ± 0,02 cm para deformación, 1,69 ± 0,14 N cm para fuerza de gel y 14,2 ± 0,8 N para fuerza de rotura, para salchichas preparadas con producto tipo surimi de CMDP. Los modelos matemáticos mostraron una buena correlación y pueden ser utilizados para aplicaciones de predicción.

Keywords:

• frankfurter
• whitemouth croaker
• mechanically deboned chicken meat
• surimi
• growth prediction
• shelf life
• texture

Palabras claves:

• salchicha
• corvina
• carne de pollo mecánicamente deshuesada
• surimi
• predicción de crecimiento
• vida útil
• textura

Introduction

A typical sausage product contains as much as 30% fat. Since a high-fat diet is a risk factor for obesity and cardiovascular diseases, among other health problems, more and more consumers demand for low-fat or reduced-fat meat products. This trend is especially challenging for comminuted meat products because reducing fat often results in changes in palatability of the meat products (Wang & Xiong, 1999).

Restructured or comminuted sausage type meat products are a diverse group of foods prepared with ground meats, added salt and spices, and have evolved into a unique range of muscle-based foods. Consumer preference for alternative healthier meat type products is stimulating the research and development of meat systems with altered compositional profiles. Moreover, the consumer interest in the development of meat analogs using alternative protein sources is increasing (Murphy, Gilroy, Kerry, Buckley, & Kerry, 2004).

Meat proteins interact in gel matrix formation in both direct and indirect ways. It is important to take these factors into account in the formulation of meat products to reduce the expensive components of meat products and to replace them with an adequate proportion of cheap, under-utilized functional ingredients. Improvement in meat product formulation could be achieved employing underutilized animal proteins, reducing costs and enhancing texture (Totosaus, 2004).

Mechanical deboning is a procedure which salvages much of the meat remaining on bones after removal of the meat by skilled meat cutters. Meat can be reclaimed from neck, frame, and back bones of poultry; and bony fish trimmings after filleting, thus providing a new raw material for processed meat products: mechanically deboned meat (MDM) (Luiz, Moreira, Corrêa, & Falcão, 2004; Sousa, Teixeira, Mello, Torres, & Moita Neto, 2003). The use of MDM in heat-processed meat products, such as frankfurters, has become common due to its low price (Lee, Williams, Sloan, & Littell, 1997; Luiz et al., 2004), despite the rapid onset of oxidative rancidity results in off-flavors, odors (Lee et al., 1997), and microbial growth (Sallam, Ishioroshi, & Samejima, 2004). It has also a high content of heme pigments, connective tissue, calcium and fat (Yang & Froning, 1992), dark color, undesired textural properties, and is susceptible to lipid oxidation (Smyth & O'Neill, 1997). Lipid oxidation is one of the main causes of quality deterioration in processed meat products, while microbial contamination can precipitate major public health hazards and economic loss. However, aqueous washing and sieving have been used to remove these compounds, which result in the MDM surimi (Smyth & O'Neill, 1997).

Surimi and surimi-based products have been gaining popularity in recent years for their protein quality, low fat content, long shelf-life (SL), and convenience in consumption (Chen, 2002). Although surimi production is typically from fish raw material, there also has been considerable interest in manufacturing surimi from species other than fish (Ismail, Huda, & Fazilah, 2011; Tina, Nurul, & Ruzita, 2010). Surimi-like material made from chicken and mechanically deboned chicken meat (MDCM) have been widely studied (Babji & Gna, 1994; Babji et al., 1995; Jin, Kim, Choi, Kim, & Hur, 2009, 2010; Kee & Babji, 1991; Kijowski & Richardson, 1996; Nowsad, Huang, Kanoh, & Niwa, 2000; Nowsad, Kanoh, & Niwa, 2000a,b; Smyth & O'Neill, 1997; Yang & Froning, 1992), presenting the highest yield and maximum gel strength among other materials (Babji et al., 1995).

Surimi and surimi-like material have been studied as substituent in different products, such as emulsified sausages, i.e. processed from Argentine croaker (Umbrina canosai) surimi (Lempek, Martins, & Prentice, 2007), meat from spent laying hen surimi-like material (Jin et al., 2007), fermented fish surimi (Shan et al., 2007), and fermented bighead carp (Aristichthys nobilis) surimi (Liu et al., 2009).

The effects of individual ingredients on surimi gels have been extensively studied using carbohydrates and proteins (Kim, 2003). However, due to the thermal treatment, where the protein matrixes of non-meat and meat components are combined, it is difficult to predict the influence of different biopolymeric ingredients, especially if combined. One way to evaluate their contribution to texture is varying the concentration of each component and analyzing their effects on the textural properties of the final product before incorporation. In this way, the rheological properties of a given biopolymer can be varied and measured (Filipi & Lee, 1998).

The whitemouth croacker (Micropogonias furnieri) is a migratory euryhaline teleostean demersal fish found in the Atlantic Ocean from Northern Venezuela (20°N) to the Gulf of St. Mathias (41°S), Argentina. Over 50% of the total fisheries production in the region (south of Brazil) is supported by sciaenid species and the whitemouth croacker is one of the most abundant and important for local fisheries (Gonçalves & Passos, 2010).

The aim of this work was to develop frankfurters from whitemouth croaker M. furnieri surimi and MDCM surimi-like material and their mixtures at different ratios, and evaluates the obtained frankfurters based on their proximal composition and texture. Moreover, growth kinetics for aerobic mesophilic and psychrotrophic bacteria were analyzed using the modified Gombertz model (Zwietering, Jongenburger, Rombouts, & van't Riet, 1990) in order to predict microbial growth on them. Finally, the SL of these products was determined based on microbiological counts while the sensory analysis was conducted based on acceptance tests.

Materials and methods

Croaker surimi and MDCM surimi-like material

Fresh MDCM and whitemouth croakers were supplied from two local poultry and fish processing plants, respectively. They were transported under refrigerated conditions to our laboratory and kept at −18°C before use. The whitemouth croakers were eviscerated before freezing. The MDCM was produced in 3 mm particle size using a meat-bone separator (Baader model 694, Lübeck, Germany), operating at inlet 6°C and outlet 10°C. It was obtained from broiler's necks, frames, thighs, and backs, 24 h after the slaughtering. Broilers were 45 days aged, hybrids of Cornish White, New Hampshire, and White Plymouth Rock.

Mechanically deboned chicken meat or whitemouth croaker meat were washed in three cycles utilizing in each cycle a washing solution:meat ratio of 4:1 (v/w), temperature of 7°C, for 10 min. In each washing cycle, the stirring was kept constant at 220 rpm using a mechanical agitator (Marconi model MA-259, Piracicaba, Brazil). A 0.5% NaHCO₃ solution was utilized for the first and second washings and 0.3% NaCl solution was used for the last one. After each washing cycle, the samples were centrifuged at 7°C (Sigma model 6-15, Osterode, Germany). The first and second centrifugations were carried out at 3000 × g for 15 min, while the third one at 7000 × g for 25 min. The supernatant containing fat- and water-soluble proteins was discarded. The final slurry was sieved through a 1-mm mesh metal screen to remove connective tissues, blended with 4% sucrose, 4% sorbitol, and 0.2% Na-tripolyphosphate, packaged in five-layer nylon propylene bags, and stored at −18°C (Cortez-Vega, Soares, Fonseca, Salas-Mellado, & Prentice, 2008).

Frankfurters

Frankfurters were prepared using the following formulation (in g/kg) adapted from Lempek et al. (2007): 825.0 surimi, surimi-like material or their mixture, 75.0 potato starch, 35.0 soybean protein, 25.0 salt (NaCl), 12.0 emulsifier, 9.9 flavoring, 9.9 seasoning (SCANPRO), 3.0 sugar, 2.0 taste enhancer, 1.5 cure salt, 1.4 color fixer, 0.3 colorant. Surimi and surimi-like material were utilized at different ratios, according to the recipe: (A) 100% (825.0 g/kg) MDCM surimi-like material, (B) 70% (577.5 g/kg) MDCM surimi-like material and 30% (247.5 g/kg) whitemouth croaker meat surimi, (C) 50% (412.5 g/kg) MDCM surimi-like material and 50% (412.5 g/kg) whitemouth croaker meat surimi, (D) 30% (247.5 g/kg) MDCM surimi-like material and 70% (577.5 g/kg) whitemouth croaker meat surimi, and (E) 100% (825.0 g/kg) whitemouth croaker meat surimi. It was thawed at 10°C until it reached 0°C just before sausage manufacture. Potato starch and soybean protein were obtained from the local commerce. The other ingredients were commercially available (Duas Rodas Industrial, Jaraguá do Sul, Brazil). The carbohydrates were mixed with the surimi prior to preparation of the inlaid emulsion. Approximately 0.5 kg of shattered ice was added during the mixture and the final moisture of the paste adjusted to 60%. The emulsion was stuffed into inlaids, frankfurter cellulose casings type, with 25 mm diameter and 180 mm length (Viskase, Guarulhos, Brazil), and processed with manual inlaid equipment (Arbel, São José do Rio Preto, Brazil). The casings were prepared by submerging them in 2.0 g/kg acetic acid solution at 25°C for 4 h. The finished frankfurters were stored overnight at 4°C, then skinned, cooked for 60 min at 85°C in water bath (Quimis model Q.215-2, Diadema, Brazil), iced for 30 min, packed in polyethylene bags, labeled, and stored at 4°C for microbial and texture kinetics analysis. For proximate composition and sensory evaluation, frankfurters were stored at − 18°C until analyzed.

Proximate composition

Moisture, crude protein, and crude fat contents were determined in triplicate according to the method described by AOAC (1995). Moisture was determined by the oven drying method at 105°C until constant weight. Total protein content was determined by the Kjeldhal method. Total lipids were evaluated by the Soxhlet method. Carbohydrates were calculated by difference.

Texture analysis

Texture analysis of the frankfurter was carried out using a texture analyzer Model TA-XT2 plus (Stable Micro Systems, Surrey, England). Emulsified inlaids kept at 4°C were equilibrated at room temperature (28–30°C) before analysis. Cylindrical samples, 2.5 × 3.0 cm, were prepared and placed in the texture analyzer equipped with a spherical plunger (5 mm diameter; 60 mm/min depression speed). Analyses were performed at least in triplicate. The results were expressed as breaking force (N) and deformation (m) representing the hardness and cohesiveness of the sample, respectively. Gel strength was expressed as the product of breaking force (N) and deformation (m) (Rawdkuen, Benjakul, Visessanguan, & Lanier, 2004). Analogously, samples were submitted to a cutting/shearing test using a Warner–Bratzler shear blade (1 mm thick) to determine the shear force (N), which indicated the firmness of the sample (Bourne, 2002; Dincer & Cakli, 2010).

Microbiological analysis

For microbiological analysis, a representative product sample of 25 g was transferred to a Stomacher-bag and homogenized for 60 s in a stomacher with 225 g chilled saline peptone diluent (8.5 g/kg NaCl with 1.0 g/kg peptone). Further, appropriate 10-fold dilution of the homogenate was made with saline peptone diluent. For each dilution blank, two replica were prepared. 0.1 ml from each appropriate dilution step was spread on the surface of solid media into Petri dishes. The counting plate analyses were followed by classical methodology. Mesophilic bacteria were determined by using plate counting agar in deep (35°C, 48 h) and psychrotrophic bacteria using plate counting agar in surface (20°C, 120 h) (da Silva et al., 2010). The SL of the products was determined as the time necessary for each microorganism reaches the microbial counting established as safe, combined with the results obtained by the sensory analysis (Galarz, Fonseca, & Prentice, 2010).

Modeling

Modified Gompertz model (Equation (1)) was utilized to describe the bacterial growth curves of the frankfurters (Zwietering et al., 1990):

where N is the microbial population (CFU/g) at time (h); N ₀ is the initial microbial population (CFU/g); A is the asymptote (ln N _max/N ₀); μ _max is the maximum specific growth rate during the exponential growth phase, defined as the tangent in the inflection point per hour; and λ is the lag time (h). The three parameters (A, μ_max, and λ) were optimized by nonlinear regression.

Sensory evaluation

Sensory analyses were conducted by 54 non-trained panelists. A nine-point hedonic scale (9 = like extremely; 1 = dislike extremely) was used for the evaluation of the overall acceptability. Samples (1-cm-long pieces) were prepared by steeping the frankfurter in boiling water for 3 min, draining the liquid, and holding on a warming tray in covered plates for no longer than 30 min. Results were expressed as the percentage of total score (ABNT, 1998).

Statistical analysis

Data obtained from the proximate composition (except carbohydrates, calculated by difference) of the different frankfurter's formulations were analyzed using the statistical one-way analysis of variance, followed by the Tukey test using the Statistica v. 8.0 software (Statsoft™, Inc., Tulsa, OK, USA) to determine significant difference between formulation's composition. Statistical significance was indicated at 95% confidence level.

Results and discussion

Proximal composition

Proximate compositions obtained for MDCM surimi-like material and whitemouth croaker fish surimi and for five different frankfurter's formulations are presented in Tables 1 and 2, respectively. These values are very close to that reported for several types of sausage (TBCA-USP, 2005) and formulations (Andrès, Zaritzky, & Califano, 2006). However, whitemouth croaker fish surimi presented different composition compared to the work previously reported (Fontana, Palezi, Prentice, & Centenaro, 2009) probably due to differences in the methodology.

Table 1. Proximate composition obtained for MDCM surimi-like material and fish surimi.
Tabla 1. Composición aproximada obtenida para surimi de CMDP y surimi de pescado.

Compound (g/kg)	MDCM SLM	Fish surimi
Protein	104.0 ± 9.7	91.0 ± 7.5
Lipid	15.0 ± 2.0	1.7 ± 0.4
Ash	5.0 ± 0.8	2.9 ± 0.2
Moisture	893.0 ± 8.9	905.0 ± 9.3
Note: MDCM, mechanically deboned chicken meat; SLM, surimi-like material.
Nota: CMDP, carne de pollo mecánicamente deshuesada; PTS, producto tipo surimi.

Table 2. Proximate composition obtained for different frankfurter's formulations.
Tabla 2. Composición aproximada obtenida para diferentes formulaciones de salchicha.

Frankfurter	Formulation	Moisture (g/kg)	Ash (g/kg)	Lipid (g/kg)	Protein (g/kg)	Carbohydrates (g/kg)
100% MDCM SLM	A	763.7 ± 7.2a	17.9 ± 0.5b	16.9 ± 0.3a	99.0 ± 10.2	102.5
70% MDCM SLM + 30% fish surimi	B	739.9 ± 5.4a	21.5 ± 1.1b	14.1 ± 0.2b	100.7 ± 9.2	123.8
50% MDCM SLM + 50% fish surimi	C	689.6 ± 6.1b	40.8 ± 0.9a	11.2 ± 0.1c	108.7 ± 5.8	149.7
30% MDCM SLM + 70% fish surimi	D	696.8 ± 2.1b	23.7 ± 1.9b	7.7 ± 0.1d	116.0 ± 8.1	155.8
100% fish surimi	E	737.9 ± 5.3a	36.2 ± 2.2a	2.3 ± 0.1e	109.7 ± 4.2	113.9
Note: Different letters in the same column mean that do exist significant difference among average scores (P > 0.05) by the Tukey test. Same letters (or without letters) in the same column mean that do not exist significant difference among average scores (P > 0.05) by the Tukey test. MDCM, mechanically deboned chicken meat; SLM, surimi-like material.
Nota: Letras distintas en la misma columna significa que no existe diferencia significativa entre las puntuaciones medias (P > 0,05) por la prueba de Tukey. Mismas letras (o sin letras) en la misma columna significa que no existe diferencia significativa entre las puntuaciones medias (P > 0,05) por la prueba de Tukey. CMDP, carne de pollo mecánicamente deshuesada; PTS, producto tipo surimi.

Moisture and protein presented similar content for both surimi and surimi-like material obtained, based on the standard deviation observed (Table 1). This way it would be expected to observe no differences among the frankfurters' formulations. For protein content, there was no difference (P < 0.05) among the formulations. However, the statistical analysis of the results showed that recipes A, B, and E differ (P > 0.05) from C and D in relation to the moisture.

Based on surimi and surimi-like material composition (Table 1), it is comprehensive that as soon as the fish surimi content increases in the frankfurter formulation, the lipid content in the frankfurter reduces too. This behavior was very clear in the frankfurters composition, being that all recipes differed statistically (P < 0.05) one from each other (Table 2). However, it is hard to explain how ash content could differ so drastically in the frankfurter's formulations. The statistical analysis of the results showed that recipes A, B, and D differed (P > 0.05) from C and E (Table 2).

The moisture content of sausages are influenced by the characteristics of the meat utilized for mechanically deboning (Mielnik, Aaby, Rolfsen, Ellekjær, & Nilsson, 2002) and hydroscopic characteristics of the additives (Figueiredo, Gaspar, Borges, & Della Modesta, 2002). The high moisture on frankfurters occurred in function of the utilization of surimi and/or surimi-like material as meat raw material, which presents a high capacity of water retention (Fontana et al., 2009; Nowsad et al., 2000b; Smyth & O'Neill 1997) mainly due to the absorption of water by hydrophilic residues of myofibrillar proteins (Ng & Huda, 2011; Smyth & O'Neill 1997; Yang & Froning, 1992).

Washing of meat increases salt soluble protein (myofibrillar proteins) content and decreases sarcoplasmic proteins content (Babji & Gna, 1994). Considering that the main constituent of the frankfurter's formulations was surimi and/or surimi-like material, it is reasonable that the high moisture content is a consequence of the high content of myofibrillar protein from both raw materials. However, it was also published that moisture content was significantly lower in sausage containing spent laying hen breast surimi-like material samples than pork meat sausage control samples (Jin et al., 2007).

It was previously reported that increase in the MDCM content in the sausage resulted in a product with higher moisture and lower protein content (Daros, Masson, & Amico, 2005). Here, despite not utilizing MSCM but MSCM surimi-like material, in general, it can be observed that moisture level increased with the augment of the MDCM surimi-like material content in frankfurters. However, in the absence of MDCM surimi-like material (recipe E), the moisture content did not decrease, as could be expected (Table 2).

The surimi and surimi-like material frankfurters presented low lipid content compared to sausages obtained from other meat sources (TBCA-USP, 2005), mainly due to the low lipid content of both surimi and surimi-like material (Table 1) and the evident no pig lard addition. Ash content was significantly lower in frankfurter containing 100% MDCM surimi-like material (Table 2). This behavior was also observed for sausage from spent laying hen surimi-like material (Jin et al., 2007). It is important to underline that ash content found in the recipes proceeds not only from surimi and surimi-like material, but also from sodium mineral added in the form of NaCl (Nowsad et al., 2000b).

Texture analysis

Breaking force, deformation, gel strength and shear force from frankfurters prepared with different surimi and surimi-like material mixtures are shown in Figures 1 and 2, respectively. The recipes had (A) 100% MDCM surimi-like material, (B) 70% MDCM surimi-like material and 30% whitemouth croaker meat surimi, (C) 50% MDCM surimi-like material and 50% whitemouth croaker meat surimi, (D) 30% MDCM surimi-like material and 70% whitemouth croaker meat surimi, and (E) 100% whitemouth croaker meat surimi.

Figure 1. (a) Breaking force (N), (b) deformation (cm), and (c) gel strength (N cm) measured in frankfurters prepared with different surimi's mixtures. (A) 100% MDCM surimi-like material, (B) 70% MDCM surimi-like material and 30% whitemouth croaker meat surimi, (C) 50% MDCM surimi-like material and 50% whitemouth croaker meat surimi, (D) 30% MDCM surimi-like material and 70% whitemouth croaker meat surimi, and (E) 100% whitemouth croaker meat surimi. Data presented are average values of at least 12 determinations. MDCM, mechanically deboned chicken meat.

Figura 1. (a) Fuerza de ruptura (N), (b) deformación (cm) y (c) fuerza de gel (N cm) medidos en las salchichas preparadas con diferentes mezclas de surimi. (A) 100% surimi de CMDP, (B) 70% surimi de CMDP y 30% surimi de carne de corvina, (C) 50% surimi de CMDP y 50% surimi de carne de corvina, (D) 30% surimi de CMDP y 70% surimi de carne de corvina, y (E) 100% surimi de carne de corvina. Los datos presentados son valores promedio de al menos 12 determinaciones. CMDP, carne mecánicamente deshuesada de pollo.

Initially, breaking force values increased with the addition of MSCM surimi-like material: 0.61 N (E), 1.23 N (D), 1.44 N (C), 1.71 N (B), and 2.29 N (A) (Figure 1(a)). Deformation demonstrated a relative constancy among the treatments: 0.71 cm (E), 0.74 cm (D), 0.71 cm (C), 0.70 cm (B), and 0.71 cm (A) (Figure 1(b)). Gel strength presented the same behavior found for breaking force: 0.40 N cm (E), 0.94 N cm (D), 0.96 N cm (C), 1.05 N cm (B), and 1.44 N cm (A) (Figure 1(c)), which in these case should be expected, considering that gel strength is the product of breaking force and deformation. Shear force also increased with the addition of MSCM surimi-like material: 1.7 N (E), 7.8 N (D), 9.3 N (C), 9.7 N (B), and 14.4 N (A) (Figure 2).

Figure 2. Shear force (N) measured in frankfurters prepared with different surimi's mixtures. (A) 100% MDCM surimi-like material, (B) 70% MDCM surimi-like material and 30% whitemouth croaker meat surimi, (C) 50% MDCM surimi-like material and 50% whitemouth croaker meat surimi, (D) 30% MDCM surimi-like material and 70% whitemouth croaker meat surimi, and (E) 100% whitemouth croaker meat surimi. Data presented are average values of at least 12 determinations. MDCM, mechanically deboned chicken meat.

Figura 2. Fuerza de corte (N) se mide en las salchichas preparadas con diferentes mezclas de surimi. (A) 100% surimi de CMDP, (B) 70% surimi de CMDP y 30% surimi de carne de corvina, (C) 50% surimi de CMDP y 50% surimi de carne de corvina, (D) 30% surimi de CMDP y 70% surimi de carne de corvina, y (E) 100% surimi de carne de corvina. Los datos presentados son valores promedio de al menos 12 determinaciones. CMDP, carne mecánicamente deshuesada de pollo.

In relation to the composition, protein content in cooked frankfurters was reported to not significantly correlate with gel rupture force, which suggests that the increased gel rupture force is most likely due to the functional performance of the protein type rather than the protein content (Wang & Xiong, 1999). It is in accordance with the results found here because no significant differences (P < 0.05) among formulations were observed for protein (Table 2).

The effect of adding proteins to gels depends on the quality of the protein or the surimi (Gómez-Guillén, Borderias, & Montero, 1996) and protein substitution can produce sausages which are harder, springier, and more cohesive (Cardoso, Mendes, & Nunes, 2009). Results previously provided for sausages manufactured with various mixtures of surimi and chicken breast meat and commercial MDCM showed that breaking force was significantly higher in the formulations containing surimi-like material instead of chicken meat (Jin et al., 2008) and that increasing the levels of surimi in combination with added fat increased shear force values, and that increasing the levels of surimi in combination with added water increased shear force in pasteurized pork-surimi sausage systems (Murphy et al., 2004). Nuckles, Smith, and Merkel (1990) reported that frankfurter made from mixtures of beef heart extract and MDCM are necessary to produce the desired bind in frankfurter formulations due to the high ionic strength of soluble proteins.

However, the hardnesses of sausages containing different concentrations of spent laying hen surimi reported were lower than in lean pork sausages (Jin et al., 2007), in pasteurized pork-surimi sausage systems (Murphy et al., 2004), and in frankfurters prepared with surimi-like extract from beef hearts (Desmond & Kenny, 1998).

In the same way, the surimi source is also reflected in the physical properties of the sausages as observed by an increase in the properties with the augment of the MDCM surimi-like material concentration in the formulation (Figures 1(a), (c) and 2). The values observed for the frankfurter-type sausage with 100% whitemouth croaker meat surimi (E) are in accordance with the results published elsewhere for sausages made with geelbeck croaker surimi (Rahman, Al-Waili, Guizani, & Kasapis, 2007). In this way, it seems that the utilization of the higher quality protein from surimi and the enzymatic modification of this preparation makes it possible to increase the desirable and uniform functional properties due to the increased association of water molecules with the proteins of surimi (Stangierski, Baranowska, Rezler, & Kijowski, 2008).

Texture is dependent on muscle fiber types from different animals. The myosin ratio is increased as the red muscle fiber ratio decreased, which suggests that the myosin ratio in surimi products is also dependent on the muscle fiber type in raw muscles (Kang et al., 2009; Kang, Park, Joo, Lee, & Lee, 2010). Moreover, the differences in texture of the fish flesh among the muscle of various species can be eventually attributed to the structural difference among the heavy chains that compose the myosins and interaction between myosin and actin, summed to the fact that in the myosin from fish it is easy to dissociate the light chains (Niwa, Koshiba, Matsuzaki, Nakayama, & Hamada, 1980).

The hypothesis that the higher values of the textural properties may be related to the increasing amount of connective tissue in samples with higher amounts of MSCM surimi-like material, based on the fact that fish is commonly known to have lower content of connective tissue compared to meat from land animals (Mackie, 1993), can also not be discarded. Collagen or connective tissue may play some important roles also in the textural development of processed foods, such as surimi-based products (Mizuta, Nakashima, & Yoshinaka, 2007). However, the final slurry of the obtained surimi and surimi-like material was carefully sieved to remove connective tissues. It was previously reported that connective tissues can be effectively removed by fractionation with a sieve (Mizuta et al., 2007).

Deformation presented no evident correlation between the formulations and with other textural properties (Figure 1(b)). Deformation is influenced mainly by protein quality (Nowsad et al., 2000) and generally a higher grade surimi has a higher breaking force and deformation (Kohyama, Sakai, Azuma, Mizuguchi, & Kimura, 2001). However, it was reported that deformation was independent of the gel strength and that there was no significant difference among samples for deformation of two different grades of blue whiting surimi (Kohyama et al., 2001) and in giant squid muscle using different gelling ingredients (Gómez-Guillén & Montero, 1997). Nowsad et al. (2000b) reported that the cohesiveness of gel might be due to the entrapment of more free water within the network matrix.

The textural properties of sausages made from MDCM surimi-like material and whitemouth croaker fish surimi and their mixtures did not significantly increase or decrease over the storage period (Figures 1 and 2). Average of textural properties obtained during storage were 2.29 ± 0.16 N (A), 1.71 ± 0.20 N (B), 1.44 ± 0.14 N (C), 1.23 ± 0.09 N (D), and 0.61 ± 0.06 N (E) for breaking force (Figure 1(a)); 0.74 ± 0.02 cm (A), 0.75 ± 0.04 cm (B), 0.77 ± 0.04 cm (C), 0.76 ± 0.03 cm (D), and 0.70 ± 0.01 cm (E) for deformation (Figure 1(b)); 1.69 ± 0.14 N cm (A), 1.30 ± 0.22 N cm (B), 1.12 ± 0.15 N cm (C), 0.93 ± 0.08 N cm (D), and 0.43 ± 0.03 N cm (E) for gel strength (Figure 1(c)); and 14.2 ± 0.8 N (A), 9.5 ± 1.2 N (B), 8.0 ± 1.3 N (C), 6.7 ± 1.0 N (D), and 2.3 ± 0.4 N (E) for shear force (Figure 2).

This behavior was showed elsewhere for pasteurized pork-surimi sausage systems (Murphy et al., 2004) and might be explained due to the possible reduction of the postmortem changes common to the meat sources present on the traditional sausages. These aspects led to the accumulation of lactic acid and a decrease in pH of muscle, which have profound effects on the physical properties of the product (Jin et al., 2007). The combination of cryoprotectants/low temperature storage and washing of the mince, prior to surimi production, to reduce gel-inhibitory substances were reported to produce high and constant textural quality surimi during long periods of storage (Nowsad et al., 2000a; Simpson, Kolbe, MacDonald, Lanier, & Morrissey, 1994). In another study, it was reported that deformation was slightly higher in surimi than in only washed minces and that this parameter increased during storage. However, it failed to show any strong correlation with other parameters of texture (Nowsad et al., 2000) as observed here.

Finally, it is important to underline that the total replacement of pig lard by potato starch and soybean protein had also contribute with the texture properties. Low-fat sausage is less hard than high-fat sausage (Carballo, Fernandez, Barreto, Solas, & Colmenero, 1996) and when the fat level is reduced, there is a significant decline in texture properties of the products. The incorporation of surimi produces scarcely any alteration in the fat- and water-binding properties and the rheological characteristics of meat products (Cavestany, Colmenero, Solas, & Carballo, 1994). However, starch has been recognized as a filler in surimi and is used to increase the hardness, cohesiveness, and firmness of products and enhance the gel strength. It has also been used to improve the texture of low fat frankfurters, favoring the formation of a more compact and stronger heat-induced protein network (Carballo, Barreto, & Colmenero, 1995; Chuapoehuk, Raksakulthai, & Worawattanamateekul, 2001; Li & Yeh, 2003; Nowsad et al., 2000b).

Microbiological analysis

Figures 3 and 4 present the growth curves (log₁₀ CFU/g) for aerobic mesophilic and psychrotrophic bacteria in the frankfurter-type sausages, respectively. Initial average counts for both microorganisms found in surimi mixture sausages (1.94–2.69 log₁₀ CFU/g) were inferior to most of those obtained in other studies, where contamination levels around 3 log₁₀ CFU/g for total viable bacteria in frankfurter-type sausages (Metaxopoulos, Mataragas, & Drosinos, 2002), of 4–6.5 log₁₀ CFU/g for total viable counts in silver carp sausages (Hu, Xia, & Ge, 2007), 7.14 and 7.28 log₁₀ CFU/g for mesophiles, and 7.72 and 7.87 log₁₀ CFU/g for psychrotrophics, in retail chicken red and white sausages, respectively (Álvarez-Astorga, Capita, Alonso-Calleja, Moreno, & García-Fernández, 2002), were reported. Even contamination levels as high as 12.1 log₁₀ CFU/g were found (Vorster, Greebe, & Nortjé, 1994). The initial counting is a very important parameter because it may be reflected in the SL of the product.

Figure 3. Growth curves for aerobic mesophilics at 4°C which grew on frankfurters prepared with different surimi's mixtures. (A) 100% MDCM surimi-like material, (B) 70% MDCM surimi-like material and 30% whitemouth croaker meat surimi, (C) 50% MDCM surimi-like material and 50% whitemouth croaker meat surimi, (D) 30% MDCM surimi-like material and 70% whitemouth croaker meat surimi, and (E) 100% whitemouth croaker meat surimi. Data presented are average values of triplicates. MDCM, mechanically deboned chicken meat.

Figura 3. Curvas de crecimiento para microrganismos aeróbicos mesófilos a 4°C creció en salchichas preparadas con diferentes mezclas de surimi. (A) 100% surimi de CMDP, (B) 70% surimi de CMDP y 30% surimi de carne de corvina, (C) 50% surimi de CMDP y 50% surimi de carne de corvina, (D) 30% surimi de CMDP y 70% surimi de carne de corvina, y (E) 100% surimi de carne de corvina. Los datos presentados son valores medios de triplicados. CMDP, carne mecánicamente deshuesada de pollo.

Figure 4. Growth curves for aerobic psychrophilics at 4°C which grew on frankfurters prepared with different surimi's mixtures. (A) 100% MDCM surimi-like material, (B) 70% MDCM surimi-like material and 30% whitemouth croaker meat surimi, (C) 50% MDCM surimi-like material and 50% whitemouth croaker meat surimi, (D) 30% MDCM surimi-like material and 70% whitemouth croaker meat surimi, and (E) 100% whitemouth croaker meat surimi. Data presented are average values of triplicates. MDCM, mechanically deboned chicken meat.

Figura 4. Curvas de crecimiento para microrganismos aeróbicos psicrófilos a 4°C creció en salchichas preparadas con diferentes mezclas de surimi. (A) 100% surimi de CMDP, (B) 70% surimi de CMDP y 30% surimi de carne de corvina, (C) 50% surimi de CMDP y 50% surimi de carne de corvina, (D) 30% surimi de CMDP y 70% surimi de carne de corvina, y (E) 100% surimi de carne de corvina. Los datos presentados son valores medios de triplicados. CMDP, carne mecánicamente deshuesada de pollo.

The aerobic bacteria present in the sausages showed a fairly pronounced multiplication after 35 and 42 days of storage for psychrotrophics and mesophiles, respectively. In sausages elaborated with minced fish (MF) from sardine (Ravishankar, Setty, & Shetty, 1992), Japanese threadfin bream (Raju, Shamasundar, & Udupa, 2003) and a mixture of sardine Sardinops sagax and mullet Mugil cephalus (Rado & Oba, 1984), an increase in the aerobic psychrotrophic bacterial count was also observed during 26, 30, and 36 days of storage at 2, 6, and 5°C, respectively.

The growth curves show the effect of storage time on the growth of spoilage and deteriorating microorganisms. There was no clear relationship among the microbial growth curves general profile and the different frankfurter's formulations. However, the microbial parameters generated by Gombertz modeling reveal that as the fish surimi concentration increases from 0% (A) to 100% (E) in the frankfurter, the lag phase (λ) becomes shorter, especially for psychrotrophics, indicating the easy adaptation in this kind of substrate at a chilling temperature (4°C). The maximum specific growth rate (μ_max) was around 0.010–0.022 h⁻¹ and the asymptote (A) (ln N _max/N ₀) on the range of 9.1–13.4, for both aerobic mesophilic and psychrotrophic microorganisms, in all frankfurter's types. The Gombertz model presented a strong fit due to the high correlation observed between experimental data and predicted values (Table 3).

Table 3. Values of parameters A, μ _max, and λ obtained from the modified Gombertz model for aerobic mesophilic and psychrophilic bacteria, grew at 4°C, present on frankfurters prepared with different surimi's mixtures.
Tabla 3. Valores de los parámetros A, μ _max, y λ obtenidos a partir del modelo de Gombertz modificado para bacterias aerobias mesófilas y psicrófilas, crecidas a 4°C, presentes en las salchichas preparadas con diferentes mezclas de surimi.

Formulation	100% MDCM SLM (A)				70% MDCM SLM + 30% fish surimi (B)				50% MDCM SLM + 50% fish surimi (C)				30% MDCM SLM + 70% fish surimi (D)				100% fish surimi (E)
M.o./parameter	A	μ max	λ	r	A	μ max	λ	r	A	μ max	λ	r	A	μ max	λ	r	A	μ max	Λ	r
Mesophilics	13.4	0.017	311.6 h (13.0 days)	0.996	10.1	0.017	305.6 h (12.7 days)	0.988	11.3	0.018	287.4 h (12.0 days)	0.994	9.1	0.018	278.7 h (11.6 days)	0.985	9.4	0.015	265.2 h (11.1 days)	0.997
Psychrophilics	10.6	0.019	277.2 h (11.5 days)	0.998	10.4	0.022	232.2 h (9.7 days)	0.991	11.2	0.021	200.5 h (8.4 days)	0.993	9.7	0.016	137.8 h (5.7 days)	0.988	11.4	0.010	96.2 h (4.0 days)	0.994
Notes: (A) 100% MDCM SLM, (B) 70% MDCM SLM and 30% whitemouth croaker meat surimi, (C) 50% MDCM SLM and 50% whitemouth croaker meat surimi, (D) 30% MDCM SLM and 70% whitemouth croaker meat surimi, and (E) 100% whitemouth croaker meat surimi. MDCM, mechanically deboned chicken meat; SML, surimi-like material.
Notas: (A) 100% surimi de CMDP, (B) 70% surimi de CMDP y 30% surimi de carne de CMDP, (C) 50% surimi de CMDP y 50% surimi de carne de corvina, (D) 3% 0surimi de CMDP y 70% surimi de carne de corvina, y (E) 100% surimi de carne de corvina. CMDP, carne de pollo mecánicamente deshuesada; PTS, producto tipo surimi.

Shelf-life

The microbiological counting assesses the degree of deterioration of chilled foods. The Brazilian Legislation does not set any standard for most of the microorganisms. However, the ICMSF (1978) indicated the 10⁶–10⁷ CFU/g range as standard to determine the end of the SL of meat products. Later, it has established the aerobic bacteria counting of 10⁷ CFU/g as an indicator for the end of SL (ICMSF, 1986). Other authors provide values ranging from 10⁶ to 10⁸ CFU/g (Davies & Board, 1998; Smolander, Alakomi, Vainionpää, & Ahvenainen, 2004). Based on that, 10⁷ CFU/g was considered a limit for determining the SL in this study.

In general, frankfurter sausages prepared with whitemouth croaker surimi and MDCM surimi-like material mixtures presented an average SL of 42 days when stored under non-vacuum conditions at 4°C. In none of the studied conditions, the highest populations (around 7 log₁₀ CFU/g) of total viable bacteria were surpassed before the referred day. This is in accordance with the results previously reported. Sausages prepared with MF from Nile tilapia Oreochromis niloticus filleting waste have a SL of 40 days when stored at 0 ± 0.3°C and the maximum recommended MF inclusion to maintain good sensory quality was 60% (de Oliveira, Favaro-Trindade, Trindade, Balieiro, & Viegas, 2010). The SL of frankfurter-type sausages under vacuum packaging was reported as about 35–42 days, at a storage temperature of 4°C (Blickstad & Molin, 1983). However, frankfurter-type sausages under vacuum at 4°C were reported to present highest populations (around 8 log₁₀ CFU/g) at the end of storage (28th day) (Metaxopoulos et al., 2002). The long SLs presented here are probably due to the lower initial countings, always below 2.69 log₁₀ CFU/g.

Sensory analysis

In terms of “overall acceptability,” sensory evaluation scores showed that frankfurter recipe A prepared with 100% MDCM surimi got the highest acceptability score (45.0%). It was found that sausage sample with 100% whitemouth croaker surimi presented the lowest acceptation by the panelists (8.3%) (Figure 5).

Figure 5. Sensory analysis carried out in frankfurters prepared with different surimi's mixtures. (A) 100% MDCM surimi-like material, (B) 70% MDCM surimi-like material and 30% whitemouth croaker meat surimi, (C) 50% MDCM surimi-like material and 50% whitemouth croaker meat surimi, (D) 30% MDCM surimi-like material and 70% whitemouth croaker meat surimi, and (E) 100% whitemouth croaker meat surimi. MDCM, mechanically deboned chicken meat.

Figura 5. Análisis sensorial realizado en salchichas preparadas con diferentes mezclas de surimi. (A) 100% surimi de CMDP, (B) 70% surimi de CMDP y 30% surimi de carne de corvina, (C) 50% surimi de CMDP y 50% surimi de carne de corvina, (D) 30% surimi de CMDP y 70% surimi de carne de corvina, y (E) 100% surimi de carne de corvina. CMDP, carne mecánicamente deshuesada de pollo.

In a general way, the addition of MDCM surimi improved sensory acceptability mainly due to the better quality and texture parameters of this surimi (Gómez-Guillén et al., 1996). Surimi-like material had been incorporated into restructured products enhancing fat-binding properties in frankfurter without adversely affecting acceptability and consumer preference (Desmond & Kenny, 1998; Murphy et al., 2004; Wang & Xiong 1999).

Moreover, it was previously reported that sausages prepared with fermented bighead carp (Aristichthys nobilis) surimi presented sensory characteristics than the control (Liu et al., 2009) and that fish sausage from hybrid Clarias catfish meat and surimi showed the highest acceptability score when prepared from fish meat to surimi at a ratio of 40:60 with 10% pork fat (Chuapoehuk et al., 2001).

Conclusions

The developing of low-fat or reduced-fat meat products is especially challenging for comminuted meat products because reducing fat often results in changes in palatability and texture of meat products.

The chemical compositions and textural properties of the developed frankfurters were influenced by the whitemouth croaker surimi and MSCM surimi-like material ratio present in the formulation. The frankfurters had low lipid content compared to sausages obtained from other meat sources due to the low fat content of the raw meat materials.

The addition of MSCM surimi-like material to frankfurters favored greater shear force, breaking force, and gel strength. On the contrary, increasing levels of whitemouth croaker surimi reduced rheological parameter values. Deformation presented no evident correlation between the formulations and with other textural properties. The textural properties of frankfurters made from whitemouth croaker surimi, MSCM surimi-like material, and their mixtures did not significantly increase or decrease over the storage period.

The improvement of sensory evaluation score at sample with higher content of MSCM surimi-like material correlated with the harder texture of the finished frankfurter which indicates that panelists preferred the harder frankfurter. The frankfurter-type sausages produced and characterized here have presented promising characteristics for commercial applications.

Acknowledgment

The present study was supported by the CHILL-ON project, contract number: FP6-016333-2, as part of the Sixth Framework Programme, Priority 5, Food Quality and Safety.