Properties of Frankfurter-type Sausages with Pork Back-fat Replaced with Bovine Heart Surimi-like Materials

The bovine heart surimi-like material (BHSM) was manufactured using three washing steps. Fresh bovine hearts (24-h postmortem) were obtained from a commercial slaughterhouse. The bovine heart was trimmed to visible fat and connective tissues with knife, and the lean muscle was cut into approximately 2-cm cubes. The lean muscle was ground through a 3-mm-diameter orifice using a mincer. The minced samples were combined with 5 volumes distilled water and homogenized using a Polytron homogenizer (T25-B, IKA Sdn. Bhd., Malaysia) at 8,000 rpm for 30 s. The resulting slurry was filtered through a metal sieve with a 2-mm mesh to remove the connective tissue and re-filtered through cheese cloth. The filtrate was centrifuged at 2,000 g for 20 min, and the supernatant containing fat and water-soluble proteins was discarded. The residue was washed with 5 volumes distilled water and subjected to final centrifugation at 2,000 g for 10 min and the supernatant was discarded. The final residue used in the experiment.

Three independent replicates of each batch were prepared in same ways. Fresh beef, pork lean and pork back-fat were obtained from a local meat processing plant. The beef and pork lean meat was trimmed of any visible fat and connective tissue, and each replicate was ground separately through a 3-mm plate in twice. Prior to incorporation into the sausage batter, the moisture content of BHSM was presented to 85%, and different amounts of BHSM were added with water to provide four different formulations. Four different formulations of frankfurter-type sausages were processed in a pilot plant: 1) without BHSM (control); 2) containing 20% BHSM; 3) containing 40% BHSM; and 4) containing 60% BHSM. In the formulation of frankfurter-type sausages manufactured with 20%, 40%, and 60% BHSM of the pork back-fat were replaced. The ingredient composition of the frankfurter-type sausages is presented in Table 1.

For each batch of frankfurter-type sausages, all ingredients were mixed and homogenized in a silent cutter (AS-30, Ramon, Spain). All added ingredients were mixed for 5 min and maintained at a final temperature below 15℃. The emulsified sausage batter was stuffed into cellulose casings (approximate diameter of 40 mm) using a stuffer (H15, TALSA, Spain). The sausages were then held for 24 h at 4℃ to allow the ingredients to equilibrate. Sausage samples were then cooked for 60 min at 80℃ to an internal temperature of 75℃ in a chamber (750-TH-11 Cook & Hold oven, Alto-Shaam, USA). After cooking, sausage samples were cooled to 4℃, packaged in oxygen-permeable bags (polyethylene, 26.8×27.9 cm, 2 mm, Thai Griptech Co. Ltd., Thailand), and stored at 4℃ for 1 or 14 d. Proximate composition, cooking loss, emulsion stability, pH, color, texture profile analysis, and TBARS were determined after storage for 1 d, and sensory characteristics were analyzed after 1 and 14 d.

The proximate composition analysis of the frankfurtertype sausage, including moisture, crude protein, crude fat and crude ash, was performed according to AOAC methods 950.46 (oven air-drying), 992.15 (Kjeldahl nitrogen), 985.15 (ether-extractable component), and 920.153 (muffle furnace) for sausage (AOAC, 2000).

The pH was measured using a digital pH meter (MP 230, Mettler Toledo, Switzerland). Approximately 3 g of cooked sausage sample was added to distilled water (27 mL). A slurry was then made using a polytron homogenizer (T25-B, IKA, Malaysia) and the pH measured. The pH meter was calibrated daily using standard buffers of pH 4.0, 7.0 and 9.0 at 25℃.

The yield due to cooking was determined for each treatment-replication combination. Weight of uncooked and cooked sausages was recorded (Boles and Swan, 1996). The cooking loss was calculated as follows:

Cooking loss (%) = [uncooked weight (g) − cooked weight (g) / uncooked weight (g)] × 100

Emulsion stability was determined using the methodology proposed by Jiménez-Colmenero et al. (2005) with some modifications. Raw batter (25 g) was transferred into a centrifuge tube. The samples were heated in a boiling water bath for 30 min at 70℃ followed by centrifugation at 1,000 rpm for 10 min. The total amount of fluid released was expressed as a percentage of the original weight. The content of released fat was determined from the difference in the total liquid released after drying at 105℃ for 16 h.

Color was assessed on the cut surface of the cooked sausages using a Minolta Chromameter CR-300 (Minolta Co., Japan) standardized with a white plate (Y=93.5, X= 0.3132, y=0.3198). Five replicate measurements were taken and results were expressed as CIE (Commission International de l’Eclairage) L*, a*, and b*.

Thiobarbituric acid-reactive substances (TBARS) content of the sausage samples from each treatment was determined using the TBARS method (Buege and Aust, 1978). The sausage sample homogenate (2 mL) was transferred to a disposable test tube (13×100 mm), and Dibutyl hydroxyl toluene (10%, 50 μL) and thiobarbituric acid/trichloroacetic acid (TBA/TCA) solution (4 mL) were added. The sample was mixed using a vortex mixer, and then incubated in a boiling water bath for 15 min to develop the color. The sample was analyzed at 531 nm against a blank containing 2 mL of deionized distilled water and 4 mL of TBA/TCA solution. The amounts of TBA were expressed as mg of malondialdehyde (MDA) per kg of sample.

TPA was performed using an Instron Universal Testing Machine (Model 3343, Instron, MA). Three cooked sausage cores (diameter 2.5 cm, height 2.0 cm) per treatment were axially compressed to 70% of their original height. Force versus time curves were obtained using a 98-N load cell applied at a crosshead speed of 100 mm/min. The textural attributes of hardness, cohesiveness, springiness, gumminess and chewiness were calculated from the curve (Bourne, 1978).

Sausage samples from each treatment were evaluated by an 8-member trained, expert descriptive attribute sensory panel at Gyeongsang National University. The panelists were selected and trained according to the procedures of Jung et al. (2012) as modified by Meilgaard et al. (1999). Panelists were given samples representing anchor points for each attribute, and training sessions using emulsion-type sausages with or without BHSM in the meat lab. The panelists were trained using a 5-point scale (“5=extremely intense” and “1=slightly intense”) for emulsion-type sausage color, cooked sausage flavor, and texture attributes (hardness and juiciness). Final anchor point ratings were decided upon by the training panel after initial evaluation and discussion. They were trained with emulsion-type sausage products for 2 wk on the product characteristics to be evaluated. Cold water was also provided for rinsing their mouths before each sample was tested.

Panelists evaluated the samples in terms of color, flavor, odor, juiciness, tenderness and overall acceptability using a 9-point hedonic scale, where 1=“dislike extremely” and 9=“like extremely,” as described by Meilgaard et al. (1999). The samples were placed in glass containers (Pyrex^®, Charleroi, PA) with plastic covers before the sensory test. Each panelist received at least 2 cubes per sample and evaluated 8 randomly ordered samples (with/without BHSM) per day (day 1 or day 14).

The experiment had to three replications. Data was analyzed by the procedures of generalized linear model (GLM) of SAS (2014) Tukey’s multiple range test was used to compare the mean values of treatments. Mean values and standard error of the means (SEM) were reported. In case of sensory data was analyzed by the two-way analysis of variance (GLM) was used to evaluate the significance of differences of the obtained data, mean values and standard deviations were reported. Statistical significance for all comparisons was made at p<0.05.

The proximate compositions and pH of frankfurter-type sausage are presented in Table 2. The ash contents showed no significant differences among the sausage samples. However, as expected, the treatments differed significantly with respect to their levels of moisture, protein, and fat. The moisture content was higher in the samples with 40% BHSM (T2) and 60% BHSM (T3) than the control (p<0.05). Compared to the control, 40% BHSM (T3) had a significantly lower protein content due to the added BHSM (p<0.05). The fat content was also lower in the samples with 40% BHSM (T2) and 60% BHSM (T3) than the control (p<0.05). The replacement of animal back-fat with BHSM was expected to decrease the total fat content in the sausage batters. Desmond and Kerry (1998) reported that a decrease in the protein content of frankfurter sausages from the addition of surimi-like extracts from bovine heart. However, Choi et al. (2012) obtained similar results in pork patties, with the addition of surimi-like materials from porcine muscle leading to increased protein content and reduced total fat content. Similar results were also found in ham pâté with added isolated plasma and globin (Viana et al., 2005).

The pH values of frankfurter-type sausages were higher in the samples with added 40% BHSM (T2) and 60% BHSM (T3) than the control (p<0.05). Seo et al. (2015) obtained similar results in pork sausages, where pork was replaced with chicken breast and surimi levels increased pH values. Myofibrillar tissues such as myosin and actomyosin are dramatically influenced by pH and an increase in gel pH led to an increase in water-holding capacity (Kristinsson and Hultin, 2003).

The physicochemical properties of frankfurter-type sausages are presented in Table 3. The lightness and redness values were not significantly different among all sausage samples (p>0.05). However, frankfurter-type sausages in T2 had a higher lightness value than the other samples, and the measured redness and yellowness were also lower in the T2 sample. Jin et al. (2007) suggested that surimilike material has high whiteness and lightness due to the removal of pigments, including myoglobin. Desmond and Kerry (1998) also reported a decrease in the lightness and redness values of frankfurter sausages due to the addition of surimi-like material. Therefore, manufactured frankfurter-type sausages containing 40% BHSM showed increased lightness and decreased redness value in the present study.

The T3 treatment sausage exhibited a higher cooking loss than the control (p>0.05), whereas no significant differences were detected among the control, T1, and T2 frankfurter-type sausages (p<0.05). In general, cooking loss was used to measure of the lost juices amount during cooking. Desmond and Kerry (1998) reported that up to 15% of a surimi-like material from bovine heart may be employed in the preparation of frankfurter sausage formulations without increasing cooking loss. Based on the results of our study, 40% BHSM may be used in sausage formulations without affecting cooking loss.

Lipid oxidation is closely related to fat level and the higher the amount of fat and unsaturated fatty acids present, the greater the TBARS value obtained (Tang et al., 2001). The TBARS value was higher in the treatment with 60% BHSM (T3) than the control (p<0.05). However, no significant difference was observed between the 20% BHSM (T1) and 40% BHSM (T2), when compared to the control. Ahmad and Srivastava (2007) observed that the TBARS value was not significantly affected by the addition of heart. On the other hand, pork sausages in which the pork is replaced with chicken breast and surimi displayed increased TBARS values (Seo et al., 2015). TBARS values were usually below 0.7-1.0 mg malondialdehyde/kg meat, and taste with fat oxidation of acid deterioration would be affected in sensory evaluation tests when reaching levels above 1.0 mg malondialdehyde/kg meat (Ockerman and Kesh, 1982).

Table 3 shows the effects of adding BHSM on the emulsion stability of frankfurter-type sausages. Fat exudation showed no significant differences among the sausage samples. However, T2 and T3 sample groups had the lowest water exudation, and therefore, the highest emulsion stability. Faria et al. (2015) obtained similar results in bologna-type sausages, where the replacement of pork back-fat with pork skin and amorphous cellulose increased emulsion stability, and the higher emulsion stability observed in treatment samples can be attributed to the high amorphous cellulose content. Therefore, a high amount of BHSM has the ability to interact with proteins, forming a more gel-like matrix, and preventing the exudation of water (Anderson and Berry, 2001). These results were expected since proteins are used as fat replacers due to their ability to bind water and emulsify fat droplets.

The texture profile analysis of frankfurter-type sausages are presented in Table 4. The hardness value was higher in the treatment samples T2 and T3 than the control (p<0.05), and the hardness of the frankfurter-type sausages gradually increased with the increasing amount of BHSM. The cohesiveness value was higher in T1 than the control sample (p<0.05). In comparison to the control, all treatment samples had a significantly higher gumminess value due to BHSM addition (p<0.05), and the chewiness value was higher in T2 and T3 than the control (p<0.05).

Fat positively influences the water-binding capacity and textural properties of meat products. The reduction of fat can lead to unacceptable textures and sensory properties (Keeton, 1994). In the present study, the replacement of back-fat with BHSM could explain the observed harder texture properties of the frankfurter-type sausages. However, Viana et al. (2005) reported a decrease in the hardness of ham pâté from the addition of globin and plasma as fat replacers. Yang et al. (2007) also reported that pork sausage containing hydrated oatmeal and tofu displayed a reduced hardness when compared to the low-fat control. The use of surimi-like material as a protein additive in an emulsion sausage formulation led to a reduction in hardness (Desmond and Kerry, 1998). In another study, the presence of texture-modifying extenders may reduce binding among proteins rather than the water-binding property of the extenders (Kerry et al., 2005).

The changes in sensory evaluation in frankfurter-type sausages with added BHSM during storage at 4℃ are presented in Table 5. The odor scores increased during storage for 14 d in the T2 and T3 samples, and the juiciness score decreased after 14 d in the control sample (p<0.05). On day 1, there was no difference in color, flavor, odor and tenderness score between the control and treatment samples (p<0.05). However, the juiciness and overall acceptability scores of the frankfurter-type sausages with 60% BHSM (T3) were lower than those of other samples. On day 14, the flavor score was lower in the treatment samples T2 and T3 than the control (p<0.05). The T3 sample displayed a lower juiciness score compared to the control (p<0.05). There was no difference in the overall acceptability, but control was high score than other treatments. Choi et al. (2012) reported that sensory characteristics are increased by the addition of 10% or 20% surimi-like material form pork muscle. Desmond and Kerry (1998) also reported that the addition of 7% or 10% surimi-like material from bovine heart significantly affected product tenderness and overall acceptability. However, several studies have found similar results for lowand reduced-fat products, with these leading to unacceptable product palatability. There were no significant differences in sensory acceptability between pork sausage with 30% fat and low-fat pork sausage with 6.3% fat and 25.3% surimi (Murphy et al., 2004).

In present study, a slight reduction in flavor scores was observed in the samples that had back-fat replaced with BHSM. Furthermore, a significant reduction in overall acceptability scores was observed in the T3 where back-fat was replaced with BHSM. Because BHSM was odor, but all treatments did not significantly differ from the results of overall acceptability obtained after 14 d (p<0.05). Therefore, our study demonstrated that acceptable frankfurter-type sausages can be produced when back-fat is replaced with up to 40% BHSM.