Effects of Calcium Powder Mixtures and Binding Ingredients as Substitutes for Synthetic Phosphate on the Quality Properties of Ground Pork Products

Raw pork ham (M. biceps femoris, M. semitendinosus, and M. semimembranosus) used in this study was purchased from a local meat processor (Pukyung Pig Farmers Livestock Cooperatives, Korea) at 24–48 h postmortem. After removing subcutaneous and intermuscular fat and visible connective tissues from the fresh ham, lean pork meat was cut in squares of 4–5 cm, vacuum-packaged in nylon/PE film bags, and stored in a freezer at -18℃ until processing. Pork back fat was prepared in the same manner. The frozen pork ham and back fat were stored at 2℃–3℃ for 24–36 h before processing. The thawed raw materials were ground in a chopper (TC-22 Elegant plus, Tre Spade, Italy) with an 8-mm plate and then again ground with a 3-mm plate. A phosphate blend (mixtures of sodium tripolyphosphate, tetrasodium pyrophosphate, and sodium hexametaphosphate) (Polymix-CS, SDBNI Co. Ltd., Korea) was used as the synthetic phosphate. The egg shell calcium (egg shell calcium 50, Essentron Co. Ltd., Korea) and oyster shell calcium (oyster shell calcium 40, JK Biochem Co. Ltd., Korea) were purchased from commercial suppliers. The egg shell calcium and oyster calcium powders tested in this study contained 39.6% and 51.6% calcium, respectively. As binding ingredients, egg white powder (Egg white, TOF Co. Ltd., Korea), whey protein concentrate (WPC, TOF Co. Ltd., Korea), concentrated soybean protein (CSP, TOF Co. Ltd., Korea), isolated soybean protein (ISP, Yujin Co. Ltd., Korea), carrageenan (carrageenan WG-5, MSC Co. Ltd.), and collagen powder (collagen powder, Ikjin Co. Ltd., Korea) were also prepared. The formulation of the pork meat products with the calcium powder mixtures and binding ingredients is presented in Table 1.

The control was processed by mixing ground pork meat and back fat with 1.5% NaCl, 0.3% phosphate blend, and 15% ice water in a mixer (KitchenAid 5K5SS, Whirlpool Corp., USA) for 5 min (Fig. 1). For treatments, 1.5% NaCl and 15% ice water were incorporated into the ground pork meat and back fat; samples were then produced by combining 0.5% natural calcium mixtures (NCM, comprising 0.2% oyster shell calcium and 0.3% egg shell calcium powder) with 0.25% egg white powder (treatment 1), whey protein concentrate (treatment 2), concentrated soybean protein (treatment 3), isolated soybean protein (treatment 4), carrageenan (treatment 5), or collagen powder (treatment 6). The meat mixtures from each batch were stuffed into conical tubes (50 g each) using a stuffer (MOD.5/V Deluxe, Tre Spade, Italy). The stuffed tubes were centrifuged at 2,000×g for 10 min in a centrifuge (FELTA5, Hanil Scientific Inc., Korea) to remove air pockets. The tubes were then transferred into a 90℃ water bath (CB60L, Dong Won Scientific System, Korea) and cooked to an internal temperature of 75℃. Changes in temperature were monitored by inserting a K-type thermocouple attached to a digital thermometer (TES-1384, Ketech Scientific Instrument Co., Ltd., Taiwan) into the center of the samples. After cooking, the samples were immediately cooled on ice slurry for 20 min and placed at 2℃–3℃ overnight, prior to analyzing dependent variables. All experiments were performed in triplicate.

Fig. 1. Schematic diagram of manufacturing process for ground pork meat products with natural calcium powders and various binding ingredients.

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Five grams of the samples was weighed before and after cooking and homogenized with 20 mL of distilled water for 1 min in a homogenizer (DI 25 basic, IKA^®-Werke GmbH & Co. KG, Germany). The pH was measured using a pH meter (Fisher Scientific Accumet AB150, Thermo Fisher Scientific, Inc., Singapore) equipped with a glass electrode.

Moisture content of the cooked products was measured using the drying method (AOAC, 2007). The samples were dried using a 105℃ dry oven (CB60L, Dongwon Scientific System, Korea) for 12 h, and the difference between the weight of each sample before and after drying was calculated.

As previously described, the weight of each sample in the conical tube was measured prior to cooking and then again after cooking and cooling to determine the cooking loss using the following equation:

Commission Internationale de l'Eclairage (CIE) measurements were used to determine lightness (CIE L*), redness (CIE a*), and yellowness (CIE b*). CIE L*a*b* values were measured on freshly cut surfaces of the cooked samples using a colorimeter (Chroma Meter CR-400, illuminant C; Konica Minolta Sensing Inc., Japan). Two slices from each cooked sample were cut in half (parallel to the longitudinal axis), and three CIE L*a*b* readings per slice were taken immediately after cutting. The colorimeter was standardized against a white calibration plate (CIE L*=+94.90, a*=-0.39, and b*=+3.88).

After cutting the samples to a width of 2.5 cm perpendicular to the longitudinal axis, their hardness, springiness, cohesiveness, gumminess, and chewiness were measured using a texture analyzer (TA-XT2i, Stable Micro System, UK) equipped with a 50-mm-diameter aluminum cylinder (Bourne, 1978). The cross-head speed for measurement was 5 mm/s.

All experiments were performed in triplicate. Statistical analysis of the results was performed using the generalized linear model (GLM) procedure of the SAS package program (SAS, 2012). When the analysis of variance showed a significant difference between the means of different samples, the significance of the differences was further analyzed by Duncan's multiple range test (p<0.05).

The pH of meat products can affect their water holding capacity. The incorporation of alkaline phosphates and their blends in meat products can increase the pH, causing unequal positive and negative charges in meat proteins and resulting in higher water holding capacity (Glorieux et al., 2017; Lamkey, 1998; Long et al., 2011). The pH values of ground pork products treated with calcium powder mixtures and various binding ingredients before and after cooking are presented in Table 2. Before cooking, the treatments had higher (p<0.05) pH than the control, although no differences in pH were observed (p>0.05) among the pork products treated with the different combinations of NCM and binding ingredients. The increase in pH of the treatments was probably due to the NCM added. Cho et al. (2017) had found that the incorporation of egg shell calcium and oyster shell calcium powders to ground pork products can increase the pH. They had also reported that egg shell calcium could more significantly increase the pH than oyster calcium. After cooking, the pH of the control was lower (p<0.05) than that of all the treatments. Among the treatments, treatment 6 had the highest pH, whereas treatments 2 and 3 had the lowest. The pH of treatments 1 and 4 were in between that of the others. According to Prestes et al. (2013), the pH of collagen fiber powder and collagen fiber were 7.78 and 8.05, respectively. Therefore, the high pH of treatment 6 could be attributed to the combined effect of calcium powders and collagen powder. Generally, higher pH in meat results in more water retention (Sebranek, 2009, Sebranek, 2015; Trout and Schmidt, 1983).

Based on the observed pH of the cooked products, it is expected that water retention ability would vary in the different formulations. However, all treatments had similar (p>0.05) moisture contents, compared to the control (Table 2). It has been shown that phosphates and salt in meat products increase the meat protein solubility and ionic strength, thereby contributing to water retention ability (Petracci et al., 2013; Sebranek, 2015; Trout and Schmidt, 1983). Therefore, this result indicated that the absence of synthetic phosphate had no detrimental effect on moisture content, which might have been due to the variation in pH caused by the addition of natural calcium powder and binding ingredients.

The cooking loss of ground pork products treated with calcium powder mixtures and various binding ingredients are shown in Table 2. Interestingly, the cooking loss ranged from 1.15%–2.21% in products with calcium powder mixtures and binding ingredients, which was lower (p<0.05) than that observed in the control (2.79%). In particular, treatments 2, 3, and 6 had the lowest (p<0.05) cooking loss, indicating that calcium powder mixtures coupled with whey protein concentrate, concentrated soybean protein, or collagen powder could be potential phosphate replacers for industrial applications. Bae et al. (2017), after testing eggshell calcium, oyster shell calcium, marine algae calcium, and milk calcium in ground pork products, suggested that eggshell calcium could be an ideal phosphate replacer for minimizing cooking loss. Park et al. (2008) tested guar gum, ĸ-carrageenan, alginic acid, and chitosan to identify a suitable substitute for inorganic polyphosphate in the pork model system. They reported that pork samples treated with guar gum and ĸ-carrageenan showed lower cooking loss than those treated with polyphosphate.

Table 3 shows the instrumental color values of ground pork products treated with calcium powder mixtures and various binding ingredients. We found no differences (p>0.05) in CIE L* values between the control and the treatments. In addition, all treatments with NCM and binding ingredients had similar (p>0.05) CIE L* values. CIE a* values of treatments 1, 2, 5, and 6 were not different (p>0.05) from the control, but those of treatments 3 and 4 were lower (p<0.05) than that of the control. Generally, cooked meat products with higher pH are darker and redder in color (Barbut, 2009; Casco et al., 2013; Trout, 1989). However, treatment with 0.5% NCM and 0.25% binding ingredients had no effect on the CIE L* value in this study. The lighter color of the binding ingredients likely contributed to lighter products by reducing the effect of pH (Hughes et al., 1998; Youssef and Barbut, 2011). The low CIE a* values in treatments 3 and 4 could be attributed to the inherent color of the soybean products used in this study. This result is consistent with that of Park (2011a), who reported that redness decreased with the addition of concentrated soybean protein in cooked pork patties. We found no differences (p>0.05) in CIE b* values between the control and treatments. These findings are consistent with the results of Cho et al. (2017), who demonstrated that cooked pork products treated with a combination of oyster shell calcium and egg shell calcium powder had similar CIE b* values.

Table 4 shows the textural properties of ground pork products treated with calcium powder mixtures and various binding ingredients. Among the samples tested in this study, the control had hardness similar (p>0.05) to treatments 2 and 6. Choi et al. (2014) obtained similar results by adding 0.5% oyster calcium and 0.5% whey protein to restructured pork ham, and Meullenet et al. (1994) reported similar results for chicken frankfurter treated with collagen fibers. The hardness of treatments 1, 3, 4, and 5 was lower (p<0.05) than that of the control. However, springiness and cohesiveness were not different between the control and treatments (Table 4). Cho et al. (2017) reported that springiness and cohesiveness of pork products treated with 0.5% oyster shell calcium or a combination of 0.3% oyster shell calcium and 0.2% eggshell calcium powder did not differ significantly from those of the control treated with synthetic phosphate blend, which is consistent with our findings. The control had higher (p<0.05) gumminess than all the treatments except treatments 2 and 6, which had a similar (p>0.05) gumminess as the control. Chewiness was higher (p<0.05) in the control than in treatments 1, 2, 3, 4, and 5, but no differences (p>0.05) in chewiness were found between the control and treatment 6. Previous studies have reported higher gumminess and chewiness in meat products with phosphate. Bae et al. (2017) reported that hardness, gumminess, and chewiness were significantly higher in the control samples with synthetic phosphate than in samples treated with natural calcium powders. Cho et al. (2017) found that gumminess and chewiness were the highest in pork products containing a phosphate blend and that a combination of 0.2% oyster shell and 0.3% egg shell calcium improved gumminess and chewiness, which may complement the textural properties of pork products. However, in this study, the combined use of calcium powders and whey protein concentrate or collagen powder improved the textural properties of pork products (Table 4). Lee et al. (2011) had reported that the addition of oyster shell powder (0.15%, 0.3%, and 0.5%) and 0.5% whey protein to emulsion sausages significantly increased their hardness, springiness, and chewiness, compared with sausages with or without 0.3% sodium tripolyphosphate, which was partially consistent with the results of our study.