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Introduction
The meat processing industry is increasing 10% annually (Choi et al., 2015; Yun et al., 2013). Consumption patterns of meat products tend to be advanced, diversified, and convenient (Seo et al., 2014). Although the domestic meat processing industry is increasing in quantity every year, the quality of meat products is still insufficient (Kim and Lee, 2010). The quality of meat products can be affected by the prices of raw pork. Thus, the meat processing industry needs to improve its international competitiveness and sustainable development. Quality products at affordable prices can help the production and supply by replacing pork with by-products (Park, 2004).
Pork by-products include blood, bone, skin, feet, tail, red internal organs (liver, lung, heart, and kidney), white internal organs (large and small intestine), and head. By-product can provide energy, proteins, minerals, and vitamins required for human health (Kang et al., 2014; Seong et al., 2014). However, by-products are underutilized with low price because they are regarded as inferior protein source (Kim et al., 1999). Utilization of by-products in commercial products has so far been limited to the production of animal feed (Choi et al., 2009; Choi, 2013; Koh et al., 1984) due to their less desirable sensory quality and lower biological value of proteins with higher possibility of microbial contamination (Nuckles et al., 1990). However, food products will not be enough for people without using by-products (Choi et al., 2016; Hong et al., 2003). Thus, by-products should be used as food materials. Most studies on pork by-products have focused on the physicochemical properties of manufactured meat products containing by-products such as blood and skin (Choi et al., 2009; Choe et al., 2013). Utilizing pork head meat as food material has not been reported yet.
Pork head meat contains 21% tongue and 79% boneless meat. It provides collagen required for functional properties (Gonulalan et al., 2003; Park, 2004). The pork head meat has 57.0% moisture content, 20% protein content, 21.5% fat content, and high content of essential amino acids such as lysine, leucine, isoleucine, threonine, and phenylalanine (Ryu and Kim, 1984; Skarpeid et al., 2001). The head meat has been considered as an haute cuisine and served in great party of families with long history (Kim and Lee, 1998; Park, 2004). However, the consumption of pork head meat is being gradually reduced recently.
Therefore, the objective of this study was to determine the effect of reducing pork meat concentrations from 50% to 30% and replacing it with up to 20% pork head meat on chemical composition, cooking characteristics, physicochemical and textural properties, apparent viscosity, and sensory characteristics of frankfurters.
Materials and Methods
Fresh pork ham, pork head, and pork back fat were purchased from a local processor at 48 h postmortem. All subcutaneous and intramuscular fat as well as visible connective tissues were removed from the muscle. Pork ham (moisture 55.24%, protein 17.85%, fat 18.54%, pH 5.75, L*-value 60.12, a*-value 14.24, b*-value 9.14), pork head (moisture 57.12%, protein 15.71%, fat 18.74%, collagen 5.62%, pH 5.87, L*-value 56.24, a*-value 17.02, b*-value 8.32), and pork fat (moisture 12.61%, fat 85.64%) were ground through an 8-mm plate. Each part of the pork head meat ratio was 78% meat and 22% tongue. Ground tissues were then placed in polyethylene bags, vacuum sealed using a vacuum packaging system, and stored at 0℃ until use. Five different groups of frankfurters were produced. The experimental compositions of frankfurters are shown in Table 1. The first frankfurters served as controls were prepared with 50% pork meat without any pork head meat. The remaining four groups were prepared with the following combinations of pork meat and pork head meat: T1, 45% pork meat + 5% pork head; T2, 40% pork meat + 10% pork head; T3, 35% pork meat + 15% pork head; T4, 30% pork meat + 20% pork head. Pork meat and pork head meat were homogenized and ground for 1 min 30 s in a silent cutter (Nr-963009; Hermann Scharfen GmbH & Co., Germany). Pork back fat, NaCl, and sodium tripolyphosphate were added to the meat and mixed for 1 min 30 s. Meat batters were homogenized for 3 min. The temperature was maintained below 10℃ throughout batter preparation. The meat batter was stuffed into collagen casings (#240; NIPPI Inc., Japan; approximate diameter, 25 mm) using a stuffer (IS-8; Sirman, Italy). Meat batters were heated at 80℃ for 60 min in a chamber (MAXi3501; Kerres, Germany) followed by cooling down at 21℃ for 3 h (Choi et al., 2014).
Compositional properties of the frankfurters were performed using AOAC (2000). Moisture content, fat content, protein content, and ash content were determined by oven drying method (950.46B), Soxhlet method (960.69), Kjeldahl method (981.10), and muffle furnace method (920.153).
The meat batters were analyzed for cooking loss using the method of Choi et al. (2007) with the following.
Cooking loss (g/100g) = [(weight of raw meat batter (g) − weight of cooked meat batter (g)) / weight of raw meat batter (g)] × 100
The meat batters were analyzed for emulsion stability using the method of Blouka and Honikel (1992) with the following.
Total expressible fluid separation (mL/g) = [(the water layer (mL) + the fat layer (mL)) / weight of raw meat batter (g)] × 100
Fat separation (mL/g) = [the fat layer (mL) / weight of raw meat batter (g)] × 100
The pH values of samples were measured in a homogenate prepared with 5 g of sample and distilled water (20 mL) using a pH meter (Model 340, Mettler-Toledo GmbH, Switzerland).
The color of each samples was determined using a colorimeter (Minolta Chroma meter CR-210, Minolta Ltd., Japan; illuminate C, calibrated with a white plate, L*=+97.83, a*=−0.43, b*=+1.98). CIE L*-value (lightness), CIE a*-value (redness), and CIE b*-value (yellowness) values were recorded.
Texture profile analysis (TPA) was performed at room temperature with a texture analyzer (TA-XT2i, Stable Micro Systems Ltd., England). The hardness (kg), springiness, cohesiveness, gumminess (kg), and chewiness (kg) were determined as described by Bourne (1978). The frankfurters samples were taken from the central portion of each sample. The calculation of TPA values was obtained by graphing a curve using force and time plots (pre-test speed 2.0 mm/s, post-test speed 5.0 mm/s, maximum load 2 kg, head speed 2.0 mm/s, distance 8.0 mm, force 5 g).
The meat batter viscosity was measured in a rotational viscometer (HAKKE Viscotester® 550, Thermo Electron Corporation, Germany) set at 10 rpm. The standard cylinder sensor (SV-2) was positioned in a 25 mL metal cup filled with meat batter and allowed to rotate under a constant share rate (s−1) for 30 s (Shand, 2000).
A trained 12-member panel consisting of researchers of the Department of Food Sciences and Biotechnology of Animal Resources at Konkuk University in Korea was used to evaluate the frankfurters at the time. This analysis was conducted using the Hedonic test described by Choi et al. (2008). The color (1 = extremely undesirable, 10 = extremely desirable), flavor (1 = extremely undesirable, 10 = extremely desirable), tenderness (1 = extremely tough, 10 = extremely tender), juiciness (1 = extremely dry, 10 = extremely juicy), and overall acceptability (1 = extremely undesirable, 10 = extremely desirable) of the cooked samples were evaluated using a 10-point descriptive scale.
Experimental design was a completely randomized design with total of three independent batches. One-way ANOVA was performed on all the variables using the general linear model (GLM) procedure of the SAS (Statistical Analysis Systems Institute, 2008) statistical package. Duncan’s multiple range test (p<0.05) was used to determine the differences between treatment means.
Results and Discussion
Proximate compositions of frankfurter with different amounts of pork meat and pork head meat are summarized in Table 2. The highest moisture content was found in the control and T1 frankfurters. When pork head meat level was increased from 0% to 20%, the moisture content of frankfurters was decreased. According to Choi et al. (2016), the head meat containing connective tissue was low water holding capacity and water binding capacity. The protein and fat contents in frankfurters added with pork head meat were significantly (p<0.05) higher than those in the control frankfurters. However, the ash contents in the frankfurters added with different amounts of pork meat and pork head meat were not significantly (p>0.05) different from those in the control frankfurters. Park (2004) reported that the moisture, protein, and fat contents of sausage was not significantly different among treatments with different pork ham or pork head meat concentrations. In addition, there is no nutritional difference when pork meat is replaced with pork head meat (Park, 2004), similar to our results.
All values are mean±standard deviation of three replicates (n=9).
a,bMeans within a column with different letters are significantly different (p<0.05).
1)Control, frankfurter with 50% pork meat; T1, frankfurter with 45% pork meat + 5% pork head; T2, frankfurter with 40% pork meat + 10% pork head; T3, frankfurter with 35% pork meat + 15% pork head; T4, frankfurter with 30% pork meat + 20% pork head.
The cooking loss of frankfurters formulated with different amounts of pork meat and pork head meat is shown in Table 3. The cooking loss of frankfurters with pork head meat added was significantly (p<0.05) higher than that of control frankfurters. When the pork head meat level was increased from 0% to 20%, the cooking loss of frankfurters was also increased, in agreement with results of Park (2004) that cooking loss of sausages with increasing pork head meat level was increased. These results might be due to the composition of head meat. According to Lee et al. (2008), cooking loss of meat products can be affected by cooking method, additives, fat type, and raw meat type. The cooking loss of frankfurter in this study might be affected by proximate composition of pork head meat containing connective tissue.
All values are mean±standard deviation of three replicates (n=9).
a-dMeans within a column with different letters are significantly different (p<0.05).
1)Control, frankfurter with 50% pork meat; T1, frankfurter with 45% pork meat + 5% pork head; T2, frankfurter with 40% pork meat + 10% pork head; T3, frankfurter with 35% pork meat + 15% pork head; T4, frankfurter with 30% pork meat + 20% pork head.
Differences in emulsion stability of frankfurters formulated with different amounts of pork meat and pork head meat are shown in Table 3. The total expressible fluid separation and fat separation of frankfurters was significantly (p<0.05) increased in frankfurters when the pork head level was increased from 0% to 20% due to the composition of head meat. The emulsion stability exhibited a similar trend to cooking loss. For these reason, the head meat with collagen is poor emulsion stability of meat batters (Choi et al., 2016). Lee et al. (2008) have reported that improving emulsion stability can result in high water binding and high water absorption. Therefore, emulsion stability is valuable quality criteria in meat processing. According to Choi et al. (2007), water holding capacity is dependent on both moisture and fat contents. To maintain the appropriate juiciness of emulsion meat product, controlling the emulsion stability is very important. Some researchers have recommended that emulsion stability is an index of quality characteristics in emulsion meat products (Choi et al., 2008; Choi et al., 2015).
The pH and color of meat batters and frankfurters formulated with different combinations of pork meat and pork head meat are shown in Table 4. Control meat batters and frankfurters had the lower (p<0.05) pH values. The pH values of meat batters and frankfurters were significantly (p<0.05) increased when pork head concentration was increased. This was due to the higher pH of pork head meat at 5.87. Similarly, Park (2004) has reported that the pH of emulsion sausages formulated with pork head meat was higher than that of the control. Kim et al. (1999) have indicated that the pH values of pyunyuk products added with pork head meat are significantly higher than those of the control pyunyuk products without any by-product added.
All values are mean±standard deviation of three replicates (n=9).
a-eMeans within a column with different letters are significantly different (p<0.05).
1)Control, frankfurter with 50% pork meat; T1, frankfurter with 45% pork meat + 5% pork head; T2, frankfurter with 40% pork meat + 10% pork head; T3, frankfurter with 35% pork meat + 15% pork head; T4, frankfurter with 30% pork meat + 20% pork head.
The differences in the lightness (CIE L*- value), redness (CIE a*- value), and yellowness (CIE b*- value) values of meat batters and frankfurters with different combinations of pork meat and pork head meat are shown in Table 4. The lightness, redness, and yellowness values of meat batters and frankfurters with pork meat and pork head meat were significantly (p<0.05) decreased when pork head meat concentration was increased. Similar trends in color of emulsion sausages were previously reported by Park (2004) when pork head meat is added to emulsion sausages. Kim and Lee (1998) reported that the color values of pork head meat products can be affected by proximate compositions of meat products, protein denaturation, and fat denaturation due to heating. These effects observed in this study could also be due to the color of pork head which is darker than pork lean meat.
The textural properties of frankfurters formulated with different combinations of pork meat and pork head meat are shown in Table 5. Frankfurters in T4 had the lowest (p<0.05) hardness and gumminess. However, the hardness and gumminess of frankfurters in other treatments were not significantly (p>0.05) different from those of the control. Frankfurters in T2 had the highest (p<0.05) springiness. However, the cohesiveness of frankfurters in other treatments is not significantly (p>0.05) different from that of the control frankfurters. These results were in agreement with those of Park (2004) that the hardness of sausages added with pork head meat was not significantly different from that of the control sausage without any pork head meat. Kim et al. (1999) have reported that all treatments added with pork by-products have significantly lower shear force than the control. Thus, emulsion sausages manufacturing may be able to replace pork meat with head meat to achieve the texture similar to that of the control frankfurter without any pork head meat.
All values are mean±standard deviation of three replicates (n=9).
a-cMeans within a column with different letters are significantly different (p<0.05).
1)Control, frankfurter with 50% pork meat; T1, frankfurter with 45% pork meat + 5% pork head; T2, frankfurter with 40% pork meat + 10% pork head; T3, frankfurter with 35% pork meat + 15% pork head; T4, frankfurter with 30% pork meat + 20% pork head.
Replacing pork meat with pork head meat significantly affected the apparent viscosity of meat batters (Fig. 1). The apparent viscosity of meat batters with pork head was decreased when the pork head meat level was increased. Water holding capacity and water binding capacity of meat batters were weakened by the head meat with collagen (Choi et al., 2016), leading to the decreased the apparent viscosity. In addition, the viscosity values of both control and treatment samples were decreased when the rotation time was increased, thus, exhibiting a thixotropic behavior. These findings were in agreement with those of Park (2004) that the emulsion type sausages added with pork head meat had lower viscosity values compared to the control sausages without any pork head meat added. Choi et al. (2015) have reported that emulsion viscosity is correlated with emulsion stability in emulsion meat products. This study also revealed that higher apparent viscosity was correlated with higher emulsion stability of frankfurter meat batters. This might be due to the fact that pork head meat can lower the apparent viscosity value by diminishing water binding capacity and fat binding capacity (Choi et al., 2014).
The sensory characteristics of the frankfurters formulated with different combinations of pork meat and pork head meat are shown in Table 6. The color and tenderness scores were not significantly (p>0.05) different between control and frankfurters added with pork head meat. The control frankfurters had the highest (p<0.05) scores in flavor, juiciness, and overall acceptability. Frankfurters with increasing pork head concentrations had lower scores in flavor, juiciness, and overall acceptability, due to pork head with connective tissue. Similar results in sensory evaluations of emulsion sausages were reported by Park (2004) when pork head meat is added to emulsion sausages. They reported that the color, flavor, textural, juiciness, and overall acceptability of frankfurters with pork head did not significantly difference compared to control. Kim et al. (1999) have reported that the sensory evaluation appearance scores of all treatments with pork head meat added are significantly lower than those of the control. Thus, emulsion sausages manufacturing may be able to replace pork meat with up to 5% pork head meat to achieve an overall acceptability similar to that of regular or control frankfurters without any pork head meat added.
All values are mean±standard deviation of three replicates (n=9).
a-cMeans within a column with different letters are significantly different (p<0.05).
1)Control, frankfurter with 50% pork meat; T1, frankfurter with 45% pork meat + 5% pork head; T2, frankfurter with 40% pork meat + 10% pork head; T3, frankfurter with 35% pork meat + 15% pork head; T4, frankfurter with 30% pork meat + 20% pork head.
Conclusion
The replacement of pork meat with pork head meat was found to be able to affect the quality characteristics of frankfurters. Frankfurters formulated with a combination of 40% pork meat and 10% pork head meat maintained the similar sensory properties of control without head meat. Therefore, replacing pork meat with pork head meat in the formulation can successfully achieve qualities of control frankfurters. Replacing up to 10% pork meat with pork head meat in frankfurters is optimal for sensory characteristics.
