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The effect of enhancement with salt, phosphate and milk proteins on the physical and sensory properties of pork loin
MEAT SCIENCE Meat Science 72 (2006) 380–386 www.elsevier.com/locate/meatsci
The effect of enhancement with salt, phosphate and milk proteins on the physical and sensory properties of pork loin J.E. Hayes
a,*
, E.M. Desmond a, D.J. Troy a, D.J. Buckley b, R. Mehra
c
a
Teagasc, The National Food Centre, Ashtown, Dublin 15, Ireland Department of Food Technology, University College Cork, Ireland Teagasc, Dairy Products Research Centre, Fermoy, Co. Cork, Ireland b
c
Received 10 September 2004; received in revised form 5 April 2005; accepted 15 May 2005
Abstract Pork loins were pumped to 110% of original weight with solutions containing 5.5% salt and 3.3% sodium tripolyphosphate, 5.5% salt and 3.3% b-lactoglobulin (b-lg) enriched fraction or 5.5% salt and 3.3% whey protein concentrate 80% (WPC80) for comparison with non-enhanced control loins. The enhancement of pork loins significantly increased (p < 0.001) the tenderness and juiciness. Warner-Bratzler shear force values were lower (p < 0.001) in enhanced then in non-enhanced control chops. The enhanced pork chops had a slightly higher overall flavour and overall acceptability to the control pork chops. Sensory analysis showed that b-lg enriched fraction and WPC80 can be used as replacement ingredients to reduce the amount of phosphate used in enhancement solutions, as they were comparable to salt/sodium tripolyphosphate (salt/STPP) enhancement solution. Consumers rated the tenderness, juiciness and taste of the enhanced chops significantly (p < 0.001) higher then the control chops. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Enhanced pork; Sensory; Phosphate; b-Lactoglobulin enriched fraction; Whey protein concentrate
1. Introduction Tenderness and juiciness rank as the top attributes in most consumer surveys (Rust, 1998). However, a lot of the fresh pork today is often overcooked at the preparation stage, therefore producing a tough and dry product (Rust, 1998). Miller (1998) stated that enhancement is not a method to improve low pork quality, but it is a method being used by the pork industry, particularly in the US, to improve the overall quality of fresh pork in retail display. ‘‘Enhancement of fresh pork’’ is the process of adding non-meat ingredients to fresh pork, to improve the eating quality (juiciness, tenderness and flavour of the pork) of the final product (Meisinger, 2002). Enhance-
*
Corresponding author. Tel.: +35 318 059 500; fax: +35 318 059 550. E-mail address: [email protected] (J.E. Hayes).
0309-1740/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2005.05.009
ment typically consists of a solution of water, sodium tripolyphosphate (STPP), salt and varying flavouring agents injected into the muscle (Miller, 1998). The pork industry has taken advantage of injection technology to provide consumers with enhanced, more tender, juicy products (Brewer, Jensen, Prestat, Zhu, & McKeith, 2002; Glaeser, Nattre, Gibson, & Aalhus, 2003; Prestat, Jensen, McKeith, & Brewer, 2002a; Sheard, Nute, Richardson, Perry, & Taylor, 1999). Phosphates, the most common ingredients used for enhancement, increase muscle pH leading to increased water-holding capacity, decreased purge loss, improved flavour, colour stability (Keeton, 1983; Ockerman, Plimpton, Cahill, & Parrett, 1978; Prestat et al., 2002b; Sutton, Brewer, & McKeith, 1997) and juiciness (Sheard et al., 1999). The objective of this study was to evaluate the effects of enhancement using salt, STPP, b-lg enriched fractions and WPC80 on the physical and sensory attributes of
J.E. Hayes et al. / Meat Science 72 (2006) 380–386
fresh pork loins and to evaluate the use b-lg enriched fractions and WPC80 as possible replacement ingredients for STPP, which may lead to the potential reduction of phosphate in the enhancement solution. The objective of this study was to evaluate the effects of enhancement using salt, sodium tripolyphosphate (STPP), b-lg enriched fractions and whey protein concentrate 80% (WPC80) on the physical and sensory attributes of fresh pork loins and to evaluate the use of b-lg enriched fractions and WPC80 as possible replacement ingredients for STPP, which may lead to the potential reduction of phosphate in the enhancement solution. 2. Materials and methods 2.1. Sample preparation Fresh whole pork loins (72 h post-mortem, pH 5.6–5.9) were pumped to 110% of original weight with a brine solution using a Dorit Model No. PSM-21-4.5 multi-needle brine injector. Three brine solutions were formulated: 5.5% salt and 3.3% sodium tripolyphosphate, 5.5% salt and 3.3% b-lactoglobulin enriched fraction or 5.5% salt and 3.3% WPC80 for comparison with non-enhanced control loins. Ten loins were used for each treatment. After pumping, loins were vacuum packaged and held for 24 h at 2 °C to allow for equilibration of the injected solution throughout the loin. Loins were then sliced into chops (2.54-cm thick), vacuum packaged, stored at 4 °C and analysed within 7 days. 2.2. Compositional analysis After removal of the epimysial connective tissue and subcutaneous fat the pork chops were homogenised in a Robot Coupe Blender (R101, Robot Coupe SA, France). Moisture and fat were determined by an automated, integrated microwave moisture and dichloromethane fat extraction method (Bostian, Fish, Webb, & Arey, 1985) using the CEMÒ microwave moisture/solids analyser system (Model No. AV-80, CEM Corporation, 3100 Smith Farm Road, Matthews, NC 28106, USA) and a CEMÒ (Model No. FES-80) automatic extraction system. 2.3. PH pH measurements (Orion pH meter, Model 420A) were performed on pork loins (LD) prior to enhancement to ensure pH was within the range of 5.6 and 5.9. pH was measured according to an adapted procedure described by Troy (1987). 2.4. Purge loss Pork loins were weighed immediately after injection (pumping) and then vacuum packaged. The loins were
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then allowed to equilibrate at 4 °C for 24 h and reweighed for pump loss (% purge) determination (Sutton et al., 1997). 2.5. Cookloss and Warner-Bratzler shear force The chops (2.5 cm) were cooked in bags in a water bath at 78 °C, until an internal temperature of 75 °C was achieved. The chops were removed from the bags, dabbed with tissue paper to absorb excess water and the weight was recorded. Seven cores with diameters of 1.25 cm were cut from each chop, parallel to the fibre direction. These cores were sheared at the central point on a Warner-Bratzler device attached to an Instron Universal testing machine. The cores were placed such that the Warner-Bratzler blade was perpendicular to the direction of the muscle fibres. The crosshead speed used was 5 cm/min. Merlin software for windows was employed and the results were expressed in NewtonÕs (N). 2.6. Sensory characteristics Pork chops were assessed for a number of sensory characteristics by an eight-member trained panel chosen from a pool of assessors based on their experience and ability in sensory evaluation (ASMA, 1983). Training of the panellists served to familiarise them with the characteristics to be evaluated: tenderness, moistness/juiciness, flavour intensity, overall flavour and overall acceptability. The characteristics were evaluated using a 6/8-point hedonic scale where one and six/eight were the extremes of each characteristic. (6 = extremely tender, extremely juicy, extremely firm and extremely acceptable and 8 = extremely good flavour). Pork chops were cooked by grilling with turning every 3 min until cooked to an internal temperature of 71 °C. Samples were prepared for presentation by cutting 2.5 cm cubes from each pork chop. Samples were labelled with three digit random numbers and served within 2 min of cooking in random order to panellists in individual booths under red light. Panellists were instructed to cleanse their palates with water between samples. For the consumer study, each consumer was given a control pork chop (A) and one of three enhanced pork chops (STPP/salt (B), Salt/b-lg fraction enhanced (C), salt/WPC80 enhanced (D)) each of which was randomly assigned. A sample of 60 people took part in the experiment by filling out a questionnaire for each sample and recording their preference. Two samples were given to each consumer (one enhanced and one non-enhanced) with a questionnaire per pair of samples. The attributes tested for were tenderness and juiciness. The individuals were also asked which sample they preferred and based on their preference, would they be willing to purchase
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the pork chops. The consumer study was analysed using SPSS Version 9.0 for Windows. 2.7. Colour determination Instrumental colour determinations were made on the surface of the enhanced and non-enhanced pork chops using the CIE L*a*b* system with a dual beam xenon flash spectrophotometer (Ultra Scan XE, Hunter lab. CIE L* (lightness), a* (redness/greeness), b* (yellowness/blueness) values were recorded (CIE, 1978). The UltraScan XE was standardised using a black and white tile. The illumination (D65, 10°) with 8° viewing angle and a 25 mm port size. D65 was the chosen illuminant as it represents daylight. Pork chops were stored in refrigerated storage at 4 °C during analysis (LMS cooled incubator, Davidson and Hardy Ltd., Ireland). 2.8. Statistical analysis Statistical analysis was preformed using The SAS system (SAS, 1985). One-way analysis of variance (ANOVA) was used to compare means and to identify significant differences (p < 0.05) between treatments. Results for the consumer study were analysed using the software program Statistics Package for Social Sciences (SPSSÒ Base) Version 9.0 for Windows.
3.2. Cook loss Cook loss values are shown in Table 1. No significant difference (p > 0.05) was found between enhanced chops (B, C, D) and control chops (A). This is in agreement with studies carried out by Brashear, Brewer, Meisinger, and McKeith (2002) and Sheard et al. (1999). Pumping or injecting fresh pork with STPP/salt-containing solution has been shown to increase fluid retention when the product is cooked (Jones et al., 1987). Phosphate enhancement has been shown to reduce cook loss (Cannon, McKeith, Martin, Novakofski, & Carr, 1993; Detienne & Wicker, 1999). Robbins et al. (2002), reported a significantly higher cook loss (2%) for beef steaks enhanced with salt/STPP compared to controls. In early work carried out by Grey, Robinson, and Jones (1978), broiler chickens injected with STPP had higher cook losses than non-injected chickens. This apparent increase in cooking loss in injected products may be because they have more liquid to lose (10% injection level), and while salt and phosphates help hold water, they clearly cannot hold on to all of the additional liquid introduced into the product. If enhanced pork loins lost all of the added liquid during cooking, the cooking loss difference between enhanced and control samples would be expected to be 10%. In this study, the cooking loss differences were <1%, which suggests that the enhanced samples did hold onto >9% of the added liquid. 3.3. Drip loss
3. Results and discussion 3.1. Compositional analysis The moisture content of the enhanced pork loins (B, C, D) increased significantly (p < 0.001) in comparison to the control as expected (Table 1). The control loin (A) had the lowest moisture content of 74.5% while STPP/salt (B) enhanced had the highest at 77%. Jones, Carr, and McKeith (1987) found that enhancement with STPP/salt increased % moisture of the product. The significant difference of 1% between STPP/salt (B) enhanced and the other enhanced samples (C, D) may be due to the presence of STPP in the brine solution. However, Sutton et al. (1997) found that moisture was not affected by STPP.
Drip loss ranged from 0.9% to 2.8%, and was not significantly (p > 0.05) affected by either STPP/salt injection (B) or salt/WPC80 (D) injection (Table 1). However, a small but significant difference (p < 0.05) was recorded in the pork chops injected with salt/b-lg enriched fraction (C) in comparison to the control sample. Sutton et al. (1997) found that the addition of STPP to meat systems increases the meat pH. Increasing the meat pH improves the WHC by moving the meat pH further from the meat protein isoelectric point. 3.4. Purge loss The differences in purge losses were small but significant (p < 0.05) (Table 1). Salt/b-lg enriched fraction
Table 1 The effect of enhancement on the physical properties of pork loins
A B C D
Treatment
Moisture (%)
Fat (%)
Protein (%)
Cook loss (%)
Drip loss (%)
Purge loss (%)
Control STPP/salt enhanced Salt/b-lg fraction enhanced Salt/WPC80 enhanced SED
74.5a 77.0c 76.4bc 76.0b 0.19
1.0b 0.7ab 0.6a 0.8ab 0.07
22.4b 19.0a 20.5c 20.5c 0.24
31.5a 30.7a 31.4a 30.6a 0.62
1.7ab 0.9a 2.8c 2.0bc 0.24
0.0a 1.2b 1.8c 1.6bc 0.19
SED: standard of the difference of the means error. a,b Means in the same column with unlike superscripts are different (p < 0.001).
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enhanced (C) recorded the highest purge loss of 1.8%. Sutton et al. (1997) reported that STPP decreased purge loss in fresh injected loins. 3.5. Warner-Bratzler shear force All of the shear force values decreased (p < 0.001) in the enhanced pork chops (B, C, D) compared to the control (A) (Table 2). The control had the highest peak force of 38.5 N. All of the enhanced products were similar (p > 0.05) in peak force values. The salt/b-lg enriched fraction enhanced (C) had a slightly higher peak force (27.7 N) in comparison to salt/WPC80 (D) enhanced (24.9 N). Prestat et al. (2002b) found that enhancement with 0.4% STPP and 0.4% salt significantly (p < 0.05) decreased WBSF values. Positive correlations also occurred between juiciness and tenderness (r = 0.60, p < 0.05) (Table 2). Our research shows similar results with shear forces correlating well with sensory attributes of tenderness (r = 0.98; p < 0.05 for WarnerBratzler shear) and juiciness (r = 0.97; p < 0.05 for Warner-Bratzler shear) (Table 2). Smith, Simmons, McKeith, Bechtel, and Brady (1984) also noted lower shear force values for pork loins enhanced with 0.48% STPP. However, Sutton et al. (1997) found no differences between controls and pork chops enhanced with 0.4% STPP. 3.6. Sensory characteristics Tenderness was significantly increased (p < 0.001) with enhancement (Table 3). The pork chops enhanced with phosphate/salt (B) and salt/WPC80 (D) recorded the highest tenderness scores of 6.7 (‘‘very tender’’) in comparison to 5.2 (‘‘slightly tender’’) for the control. These results are also in agreement with Brashear et al. (2002) who found that the use of a salt/STPP solution increased tenderness in enhanced compared to the non-enhanced control. Pork loins enhanced with salt/ WPC80 (D) had a significantly higher (p < 0.001) tenderness rating compared to the pork chops enhanced with the salt/b-lg enriched fraction (C). Brewer et al. (1996) and Smith, Scanga, Belk, and Smith (2002) have also demonstrated that loins with added STPP and salt are more tender than the controls with added water. Sheard et al. (1999) and Smith et al. (1984) reported that Table 2 Correlation coefficients between sensory and WBSF measurements Tenderness JUICINESS O/A WBSF
Juiciness
O/A
0.989* 0.934 0.968*
0.884 0.984*
0.920
O/A, overall acceptability; WBSF, Warner-Bratzler shear force; no superscript, non-significant. * p < 0.05.
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phosphate-injected pork roasts were more tender than non-enhanced fresh cooked pork roasts. On the other hand, Jones et al. (1987) reported no tenderness difference between phosphate enhanced and control pork roasts. Juiciness was significantly (p < 0.001) improved on enhancement. Enhanced chops were moderately to very juicy in comparison to the control, which was found to be only slightly juicy. Previously other workers found that pork chops enhanced with phosphate/salt solution were more juicy then control (Brewer, Gusse, & McKeith, 1999; Keeton, 1983; Matlock, Terrell, Savell, Rhee, & Dutson, 1984; Ockerman et al., 1978; Smith et al., 2002). Pork loins enhanced with salt/WPC80 (D) had significantly higher juiciness ratings compared to the salt/b-lg enriched fraction (C) enhanced. In other studies, pork loins containing 10% water and up to 0.5% phosphate in the final products tended to have juicier chops (Jones et al., 1987; Sheard et al., 1999). Juiciness has also been improved in phosphate-enhanced pork in other studies (Smith et al., 1984; Sutton et al., 1997). The differences in overall flavour were small but significant (p < 0.024). Pork loins enhanced with phosphate and salt had a higher overall flavour rating in comparison to the control (‘‘very good’’ vs. ‘‘good’’). No difference was recorded between the salt/b-lg enriched fraction enhanced (C) and the salt/WPC80 enhanced (D) (p > 0.01). All the treatments were found to have either good or very good overall flavour rating. Keeton (1983) found that pork flavour was significantly improved by enhancement. More recently, however, Smith et al. (1984), Jones et al. (1987) and Sutton et al. (1997) reported that pork flavour was masked by addition of 0.4–0.475% STPP, i.e., had lower flavour intensity when compared to the controls. The enhanced pork loins were found to be lower (p < 0.001) in overall firmness when compared to the control. All of the enhanced pork loins were similar (p > 0.05) in overall firmness. The control (A) had the highest overall firmness rating of 6.3 and was significantly different to all the enhanced chops, which were found to be slightly firm with an average firmness rating of 5.4. The overall acceptability results indicate that the panellists found all the enhanced chops more acceptable to the control chops. STPP/salt enhanced (B) chops had significantly higher (p < 0.06) overall acceptability in comparison to the control (4.7 vs. 4.0). Smith et al. (2002) found that overall the enhanced products were very similar to each other and superior to the control products for sensory traits and WBSF measurements. Enhancement adds value to pork loins, but only if consumers perceive them to be as or more acceptable than control loins (Brewer et al., 2002). Glaeser et al. (2003) found that the overall eating quality of pork was markedly improved by needle injection of a brine solution, containing STPP and salt.
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Table 3 Enhancement effects on the sensory characteristics of pork loins Treatment A B C D
Tenderness
Juiciness
a
Control STPP/salt Salt/b-lg fraction Salt/WPC80 SED
a
4.8 6.7c 6.0b 6.8c 0.12
5.3 6.7c 6.1b 6.7c 0.12
Overall flavour
O/F
a
b
4.1 4.6b 4.3a 4.3a 0.09
6.3 5.4a 5.6a 5.3a 0.08
O/A
WBSF (N)
a
38.5b 24.7a 27.7a 24.9a 1.63
4.0 4.7b 4.3a 4.4a 0.09
O/F = overall firmness; O/A = overall acceptability; SED, standard of the difference of the means error. a,b Means in the same column with unlike superscripts are different (p < 0.001).
The responses in each category for each question in the consumer study have been presented as frequencies. Frequency distributions are useful with categorical data as they summarise all the responses to a survey question, which can then be tabulated. Sixty-three consumer evaluation sheets were sufficiently complete to use for data analysis. Fig. 1 shows the results of the frequency distributions. Seventy-eight percent of consumers rated the enhanced chop more tender over the control. Sixteen percent of those people commented on the fact that the enhanced pork chop was noticeably more tender than the control chop. This result is similar to that reported by the sensory analysis taste panel; where the three enhanced pork chops were significantly higher in tenderness rating compared to the control pork chop. Seventy-one percent of the consumers found the enhanced pork chops juicier than the control. Seven percent of consumers commented that the enhanced chop was juicier. This result is also comparable to the sensory taste panel, where the control pork chop had a significantly lower (p < 0.001) juiciness rating in comparison to all three of the enhanced chops. Sixty percent of the consumers rated the taste of the enhanced pork chop higher then control chop. Eighteen percent commented that the enhanced chop was nicer and tasted better than the control. In the sensory taste panel the overall flavour of the three enhanced pork chops (B, C, D) was rated higher then the control (A). When the consumers were asked which sample they preferred, 62% stated they preferred the enhanced pork chop (Fig. 2). Thirteen percent commented that both were acceptable and there was not a noticeable differ38%
Preference
62%
3.7. Colour determination L* values (lightness) of raw chops were unaffected by enhancement at day 1 or day 7 (Table 4). Prestat et al. (2002a) found that lightness was affected by both enhancement and storage time. Enhancement did have significant effects on both a* and b* values. Redness 70%
40%
Tastier
ence between the two samples. The sensory taste panel rated the overall acceptability of the control pork chop (A) lower compared to the three enhanced chops (B, C, D). Thirty-eight percent of respondents preferred the control sample, 32% stating that they would purchase the product, 6% stating that they would not purchase the product. Sixty-two percent of respondents stated that they preferred the enhanced sample, 60% stating that they would buy the product, while only 2% stated that they would not buy the product. Visual acceptability and consumer purchase intent of enhanced pork loin roasts was evaluated by Brewer et al. (2002). Approximately 67% of the respondents stated they would not buy ‘‘enhanced’’ pork. More than 55% ‘‘probably’’ or ‘‘definitely’’ would buy the displayed enhanced products used in the Brewer study, however they were unaware that the products were enhanced and were basing their judgments on appearance only. Enhancement adds value to pork loins but only if consumers perceive them to be more acceptable then unenhanced loins. Brewer et al. (2002) stated that the figures from their study indicated that there is a substantial market for enhanced products. However, some consumer education as to the nature and advantages of enhancement may be required.
2%
60%
60%
50%
29%
Juicier
40%
71%
20%
22%
More tender
6%
30%
60% 32%
10%
78%
0%
0%
10%
20%
30%
40%
Enhanced
50%
60%
70%
Control
Fig. 1. Consumer study on pork enhancement.
80%
90%
Preference A Would Buy
Preference B Would Not Buy
Fig. 2. Based on your preference would you purchase this product?
J.E. Hayes et al. / Meat Science 72 (2006) 380–386
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Table 4 The Effect of enhancement on the colour of pork chops
A B C D
Treatment
Day 1
Day 7
L*
a*
b*
L*
a*
b*
Control STPP/salt Salt/b-lg fraction Salt/WPC80 SED
60.5a 57.8a 58.0a 59.1a 0.70
5.3b 3.2a 5.5b 5.2ab 0.41
14.1b 11.9a 14.0b 14.0b 0.36
60.3a 58.5a 59.1a 60.2a 0.63
1.8a 2.2a 3.7b 3.8b 0.33
12.4ab 11.6a 12.6b 12.9b 0.20
SED, standard error of the difference of the means. a,b Means in the same column with unlike superscripts are different (p < 0.001).
(a*) decreased significantly (p < 0.05) in chops enhanced with salt/STPP (B) at day 1. However, redness at day 7 was increased significantly in chops enhanced with salt/ b-lg enriched fraction (3.7) (C) and salt/WPC80 (3.8) (D). Redness (a* values) decreased in all treatments between days 1 and 7 but in particular for control (A). Eckert, Maca, Miller, and Acuff (1997) also reported a decrease in redness (a*) as storage time increased. Yellowness (b*) at day 1 decreased significantly in chops enhanced with salt/STPP (B), however, yellowness (b*) at day 7 increased (p < 0.05) in chops enhanced with salt/b-lg fraction and salt/WPC80. These alterations are likely the result of pH alterations (increases) induced by phosphate addition. Prestat et al. (2002b) found that redness (a*) increased and yellowness (b*) decreased in chops enhanced with phosphate and salt at day 1. Carpenter, Saffle, and Kamstra (1961) and Krause, Ockerman, Krol, Moerman, and Plimpton (1978) reported similar results for L*, a* and b* values when evaluating phosphate effects on pork and beef. However, Sutton et al. (1997) reported that L*, a* and b* values for raw samples were unaffected by the addition of phosphate enhanced chops. Wang and Brewer (1999) reported that 0.1% phosphate did not affect yellowness (b* value), while 0.2% and 0.3% phosphate solutions significantly decreased it. Phosphate solutions generally increase product colour slightly, shifting the overall colour of red meat from lighter to darker. A proportion of this shift appears to be in the wavelength regions used to calculate b* value (yellowness) which may also account for the fact that phosphate-treated meat often appears darker than controls (Wang & Brewer, 1999). No visual colour effects were apparent between enhanced pork loin and the control loins. Brewer et al. (2002) found that 55% of consumers rated colour of enhanced loins as ‘‘somewhat acceptable (28%) or ‘‘very acceptable’’ (27%).
4. Conclusions Enhancing pork loins with solutions containing sodium polyphosphate, b-lg enriched fraction and
WPC80 enhanced sensory attributes of chops derived from them with few detrimental effects on physical and quality characteristics. Tenderness and juiciness were significantly increased (p < 0.001) with the enhancement of pork loins. b-lg enriched fractions and WPC80 can be used as potential replacement ingredients to reduce the amount of phosphate used in enhancement solutions, as they were comparable to salt/STPP enhancement solution. In the consumer study, consumers rated the tenderness, juiciness and taste of the enhanced chops significantly higher then the control chops. Sixty percent of the consumers preferred the enhanced pork chops. Sixty-two percent stated that they preferred the enhanced sample, 60% stating that they would buy the product, while only 2% stating that they would not buy the product. These findings indicate the potential of pork enhancement in meat products and the benefits enhancement would bring to the pork industry.
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Prestat, C., Jensen, J., McKeith, F. K., & Brewer, M. S. (2002a). Cooking methods and end point temperature effects on sensory and colour characteristics of pumped pork loin chops. Meat Science, 60, 395–400. Prestat, C., Jensen, J., Robbins, K., Ryan, K., Zhu, L., McKeith, F. K., et al. (2002b). Effects of enhancement solutions on characteristics of cooked, reheated pork chops. Journal of Muscle Foods, 13(1), 37–51. Robbins, K., Jensen, J., Ryan Homco-Ryan McKeith, F. K., & Brewer, M. S. (2002). Enhancement effects on sensory and retail display characteristics of beef rounds. Journal of Muscle Foods, 13, 279–288. Rust, R. E. (1998). Marketing opportunities for enhanced fresh pork. Meat International, 8(10), 36–39. SAS (1985). Statistical Analysis System. Campus Drive, Carys, NC. 27513, USA: SAS Institute Inc. Sheard, P. R., Nute, G. R., Richardson, R. I., Perry, A., & Taylor, A. A. (1999). Injection of water and polyphosphate into pork to improve juiciness and tenderness after cooking. Meat Science, 51, 371–376. Smith, K. R., Scanga, J. A., Belk, K. E., & Smith, G. C. (2002). Tenderness and sensory traits of branded, enhanced and nonenhanced pork loin hops. Animal Sciences Research Report. Department of Animal Sciences, Colorado State University. Smith, L. A., Simmons, S. L., McKeith, F. K., Bechtel, P. J., & Brady, P. L. (1984). Effects of sodium tripolyphosphate on physical and sensory properties of beef and pork roasts. Journal of Food Science, 49, 1636–1641. Sutton, D. S., Brewer, M. S., & McKeith, F. K. (1997). Effects of sodium lactate and sodium phosphate on the physical and sensory characteristics of pumped pork loins. Journal of Muscle Foods, 8, 111–112. Troy, D. J. (1987). The effect of carcass treatment on the breakdown of myofibrillar proteins during conditioning of beef muscle. MSc. thesis, University College Dublin, Ireland. Wang, C., & Brewer, M. S. (1999). Sodium lactate/sodium polyphosphate effects on – oxidation in precooked frozen pork patties. Journal of Muscle Foods, 10, 47–162.
The effect of enhancement with salt, phosphate and milk proteins on the physical and sensory properties of pork loin J.E. Hayes
a,*
, E.M. Desmond a, D.J. Troy a, D.J. Buckley b, R. Mehra
c
a
Teagasc, The National Food Centre, Ashtown, Dublin 15, Ireland Department of Food Technology, University College Cork, Ireland Teagasc, Dairy Products Research Centre, Fermoy, Co. Cork, Ireland b
c
Received 10 September 2004; received in revised form 5 April 2005; accepted 15 May 2005
Abstract Pork loins were pumped to 110% of original weight with solutions containing 5.5% salt and 3.3% sodium tripolyphosphate, 5.5% salt and 3.3% b-lactoglobulin (b-lg) enriched fraction or 5.5% salt and 3.3% whey protein concentrate 80% (WPC80) for comparison with non-enhanced control loins. The enhancement of pork loins significantly increased (p < 0.001) the tenderness and juiciness. Warner-Bratzler shear force values were lower (p < 0.001) in enhanced then in non-enhanced control chops. The enhanced pork chops had a slightly higher overall flavour and overall acceptability to the control pork chops. Sensory analysis showed that b-lg enriched fraction and WPC80 can be used as replacement ingredients to reduce the amount of phosphate used in enhancement solutions, as they were comparable to salt/sodium tripolyphosphate (salt/STPP) enhancement solution. Consumers rated the tenderness, juiciness and taste of the enhanced chops significantly (p < 0.001) higher then the control chops. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Enhanced pork; Sensory; Phosphate; b-Lactoglobulin enriched fraction; Whey protein concentrate
1. Introduction Tenderness and juiciness rank as the top attributes in most consumer surveys (Rust, 1998). However, a lot of the fresh pork today is often overcooked at the preparation stage, therefore producing a tough and dry product (Rust, 1998). Miller (1998) stated that enhancement is not a method to improve low pork quality, but it is a method being used by the pork industry, particularly in the US, to improve the overall quality of fresh pork in retail display. ‘‘Enhancement of fresh pork’’ is the process of adding non-meat ingredients to fresh pork, to improve the eating quality (juiciness, tenderness and flavour of the pork) of the final product (Meisinger, 2002). Enhance-
*
Corresponding author. Tel.: +35 318 059 500; fax: +35 318 059 550. E-mail address: [email protected] (J.E. Hayes).
0309-1740/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2005.05.009
ment typically consists of a solution of water, sodium tripolyphosphate (STPP), salt and varying flavouring agents injected into the muscle (Miller, 1998). The pork industry has taken advantage of injection technology to provide consumers with enhanced, more tender, juicy products (Brewer, Jensen, Prestat, Zhu, & McKeith, 2002; Glaeser, Nattre, Gibson, & Aalhus, 2003; Prestat, Jensen, McKeith, & Brewer, 2002a; Sheard, Nute, Richardson, Perry, & Taylor, 1999). Phosphates, the most common ingredients used for enhancement, increase muscle pH leading to increased water-holding capacity, decreased purge loss, improved flavour, colour stability (Keeton, 1983; Ockerman, Plimpton, Cahill, & Parrett, 1978; Prestat et al., 2002b; Sutton, Brewer, & McKeith, 1997) and juiciness (Sheard et al., 1999). The objective of this study was to evaluate the effects of enhancement using salt, STPP, b-lg enriched fractions and WPC80 on the physical and sensory attributes of
J.E. Hayes et al. / Meat Science 72 (2006) 380–386
fresh pork loins and to evaluate the use b-lg enriched fractions and WPC80 as possible replacement ingredients for STPP, which may lead to the potential reduction of phosphate in the enhancement solution. The objective of this study was to evaluate the effects of enhancement using salt, sodium tripolyphosphate (STPP), b-lg enriched fractions and whey protein concentrate 80% (WPC80) on the physical and sensory attributes of fresh pork loins and to evaluate the use of b-lg enriched fractions and WPC80 as possible replacement ingredients for STPP, which may lead to the potential reduction of phosphate in the enhancement solution. 2. Materials and methods 2.1. Sample preparation Fresh whole pork loins (72 h post-mortem, pH 5.6–5.9) were pumped to 110% of original weight with a brine solution using a Dorit Model No. PSM-21-4.5 multi-needle brine injector. Three brine solutions were formulated: 5.5% salt and 3.3% sodium tripolyphosphate, 5.5% salt and 3.3% b-lactoglobulin enriched fraction or 5.5% salt and 3.3% WPC80 for comparison with non-enhanced control loins. Ten loins were used for each treatment. After pumping, loins were vacuum packaged and held for 24 h at 2 °C to allow for equilibration of the injected solution throughout the loin. Loins were then sliced into chops (2.54-cm thick), vacuum packaged, stored at 4 °C and analysed within 7 days. 2.2. Compositional analysis After removal of the epimysial connective tissue and subcutaneous fat the pork chops were homogenised in a Robot Coupe Blender (R101, Robot Coupe SA, France). Moisture and fat were determined by an automated, integrated microwave moisture and dichloromethane fat extraction method (Bostian, Fish, Webb, & Arey, 1985) using the CEMÒ microwave moisture/solids analyser system (Model No. AV-80, CEM Corporation, 3100 Smith Farm Road, Matthews, NC 28106, USA) and a CEMÒ (Model No. FES-80) automatic extraction system. 2.3. PH pH measurements (Orion pH meter, Model 420A) were performed on pork loins (LD) prior to enhancement to ensure pH was within the range of 5.6 and 5.9. pH was measured according to an adapted procedure described by Troy (1987). 2.4. Purge loss Pork loins were weighed immediately after injection (pumping) and then vacuum packaged. The loins were
381
then allowed to equilibrate at 4 °C for 24 h and reweighed for pump loss (% purge) determination (Sutton et al., 1997). 2.5. Cookloss and Warner-Bratzler shear force The chops (2.5 cm) were cooked in bags in a water bath at 78 °C, until an internal temperature of 75 °C was achieved. The chops were removed from the bags, dabbed with tissue paper to absorb excess water and the weight was recorded. Seven cores with diameters of 1.25 cm were cut from each chop, parallel to the fibre direction. These cores were sheared at the central point on a Warner-Bratzler device attached to an Instron Universal testing machine. The cores were placed such that the Warner-Bratzler blade was perpendicular to the direction of the muscle fibres. The crosshead speed used was 5 cm/min. Merlin software for windows was employed and the results were expressed in NewtonÕs (N). 2.6. Sensory characteristics Pork chops were assessed for a number of sensory characteristics by an eight-member trained panel chosen from a pool of assessors based on their experience and ability in sensory evaluation (ASMA, 1983). Training of the panellists served to familiarise them with the characteristics to be evaluated: tenderness, moistness/juiciness, flavour intensity, overall flavour and overall acceptability. The characteristics were evaluated using a 6/8-point hedonic scale where one and six/eight were the extremes of each characteristic. (6 = extremely tender, extremely juicy, extremely firm and extremely acceptable and 8 = extremely good flavour). Pork chops were cooked by grilling with turning every 3 min until cooked to an internal temperature of 71 °C. Samples were prepared for presentation by cutting 2.5 cm cubes from each pork chop. Samples were labelled with three digit random numbers and served within 2 min of cooking in random order to panellists in individual booths under red light. Panellists were instructed to cleanse their palates with water between samples. For the consumer study, each consumer was given a control pork chop (A) and one of three enhanced pork chops (STPP/salt (B), Salt/b-lg fraction enhanced (C), salt/WPC80 enhanced (D)) each of which was randomly assigned. A sample of 60 people took part in the experiment by filling out a questionnaire for each sample and recording their preference. Two samples were given to each consumer (one enhanced and one non-enhanced) with a questionnaire per pair of samples. The attributes tested for were tenderness and juiciness. The individuals were also asked which sample they preferred and based on their preference, would they be willing to purchase
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the pork chops. The consumer study was analysed using SPSS Version 9.0 for Windows. 2.7. Colour determination Instrumental colour determinations were made on the surface of the enhanced and non-enhanced pork chops using the CIE L*a*b* system with a dual beam xenon flash spectrophotometer (Ultra Scan XE, Hunter lab. CIE L* (lightness), a* (redness/greeness), b* (yellowness/blueness) values were recorded (CIE, 1978). The UltraScan XE was standardised using a black and white tile. The illumination (D65, 10°) with 8° viewing angle and a 25 mm port size. D65 was the chosen illuminant as it represents daylight. Pork chops were stored in refrigerated storage at 4 °C during analysis (LMS cooled incubator, Davidson and Hardy Ltd., Ireland). 2.8. Statistical analysis Statistical analysis was preformed using The SAS system (SAS, 1985). One-way analysis of variance (ANOVA) was used to compare means and to identify significant differences (p < 0.05) between treatments. Results for the consumer study were analysed using the software program Statistics Package for Social Sciences (SPSSÒ Base) Version 9.0 for Windows.
3.2. Cook loss Cook loss values are shown in Table 1. No significant difference (p > 0.05) was found between enhanced chops (B, C, D) and control chops (A). This is in agreement with studies carried out by Brashear, Brewer, Meisinger, and McKeith (2002) and Sheard et al. (1999). Pumping or injecting fresh pork with STPP/salt-containing solution has been shown to increase fluid retention when the product is cooked (Jones et al., 1987). Phosphate enhancement has been shown to reduce cook loss (Cannon, McKeith, Martin, Novakofski, & Carr, 1993; Detienne & Wicker, 1999). Robbins et al. (2002), reported a significantly higher cook loss (2%) for beef steaks enhanced with salt/STPP compared to controls. In early work carried out by Grey, Robinson, and Jones (1978), broiler chickens injected with STPP had higher cook losses than non-injected chickens. This apparent increase in cooking loss in injected products may be because they have more liquid to lose (10% injection level), and while salt and phosphates help hold water, they clearly cannot hold on to all of the additional liquid introduced into the product. If enhanced pork loins lost all of the added liquid during cooking, the cooking loss difference between enhanced and control samples would be expected to be 10%. In this study, the cooking loss differences were <1%, which suggests that the enhanced samples did hold onto >9% of the added liquid. 3.3. Drip loss
3. Results and discussion 3.1. Compositional analysis The moisture content of the enhanced pork loins (B, C, D) increased significantly (p < 0.001) in comparison to the control as expected (Table 1). The control loin (A) had the lowest moisture content of 74.5% while STPP/salt (B) enhanced had the highest at 77%. Jones, Carr, and McKeith (1987) found that enhancement with STPP/salt increased % moisture of the product. The significant difference of 1% between STPP/salt (B) enhanced and the other enhanced samples (C, D) may be due to the presence of STPP in the brine solution. However, Sutton et al. (1997) found that moisture was not affected by STPP.
Drip loss ranged from 0.9% to 2.8%, and was not significantly (p > 0.05) affected by either STPP/salt injection (B) or salt/WPC80 (D) injection (Table 1). However, a small but significant difference (p < 0.05) was recorded in the pork chops injected with salt/b-lg enriched fraction (C) in comparison to the control sample. Sutton et al. (1997) found that the addition of STPP to meat systems increases the meat pH. Increasing the meat pH improves the WHC by moving the meat pH further from the meat protein isoelectric point. 3.4. Purge loss The differences in purge losses were small but significant (p < 0.05) (Table 1). Salt/b-lg enriched fraction
Table 1 The effect of enhancement on the physical properties of pork loins
A B C D
Treatment
Moisture (%)
Fat (%)
Protein (%)
Cook loss (%)
Drip loss (%)
Purge loss (%)
Control STPP/salt enhanced Salt/b-lg fraction enhanced Salt/WPC80 enhanced SED
74.5a 77.0c 76.4bc 76.0b 0.19
1.0b 0.7ab 0.6a 0.8ab 0.07
22.4b 19.0a 20.5c 20.5c 0.24
31.5a 30.7a 31.4a 30.6a 0.62
1.7ab 0.9a 2.8c 2.0bc 0.24
0.0a 1.2b 1.8c 1.6bc 0.19
SED: standard of the difference of the means error. a,b Means in the same column with unlike superscripts are different (p < 0.001).
J.E. Hayes et al. / Meat Science 72 (2006) 380–386
enhanced (C) recorded the highest purge loss of 1.8%. Sutton et al. (1997) reported that STPP decreased purge loss in fresh injected loins. 3.5. Warner-Bratzler shear force All of the shear force values decreased (p < 0.001) in the enhanced pork chops (B, C, D) compared to the control (A) (Table 2). The control had the highest peak force of 38.5 N. All of the enhanced products were similar (p > 0.05) in peak force values. The salt/b-lg enriched fraction enhanced (C) had a slightly higher peak force (27.7 N) in comparison to salt/WPC80 (D) enhanced (24.9 N). Prestat et al. (2002b) found that enhancement with 0.4% STPP and 0.4% salt significantly (p < 0.05) decreased WBSF values. Positive correlations also occurred between juiciness and tenderness (r = 0.60, p < 0.05) (Table 2). Our research shows similar results with shear forces correlating well with sensory attributes of tenderness (r = 0.98; p < 0.05 for WarnerBratzler shear) and juiciness (r = 0.97; p < 0.05 for Warner-Bratzler shear) (Table 2). Smith, Simmons, McKeith, Bechtel, and Brady (1984) also noted lower shear force values for pork loins enhanced with 0.48% STPP. However, Sutton et al. (1997) found no differences between controls and pork chops enhanced with 0.4% STPP. 3.6. Sensory characteristics Tenderness was significantly increased (p < 0.001) with enhancement (Table 3). The pork chops enhanced with phosphate/salt (B) and salt/WPC80 (D) recorded the highest tenderness scores of 6.7 (‘‘very tender’’) in comparison to 5.2 (‘‘slightly tender’’) for the control. These results are also in agreement with Brashear et al. (2002) who found that the use of a salt/STPP solution increased tenderness in enhanced compared to the non-enhanced control. Pork loins enhanced with salt/ WPC80 (D) had a significantly higher (p < 0.001) tenderness rating compared to the pork chops enhanced with the salt/b-lg enriched fraction (C). Brewer et al. (1996) and Smith, Scanga, Belk, and Smith (2002) have also demonstrated that loins with added STPP and salt are more tender than the controls with added water. Sheard et al. (1999) and Smith et al. (1984) reported that Table 2 Correlation coefficients between sensory and WBSF measurements Tenderness JUICINESS O/A WBSF
Juiciness
O/A
0.989* 0.934 0.968*
0.884 0.984*
0.920
O/A, overall acceptability; WBSF, Warner-Bratzler shear force; no superscript, non-significant. * p < 0.05.
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phosphate-injected pork roasts were more tender than non-enhanced fresh cooked pork roasts. On the other hand, Jones et al. (1987) reported no tenderness difference between phosphate enhanced and control pork roasts. Juiciness was significantly (p < 0.001) improved on enhancement. Enhanced chops were moderately to very juicy in comparison to the control, which was found to be only slightly juicy. Previously other workers found that pork chops enhanced with phosphate/salt solution were more juicy then control (Brewer, Gusse, & McKeith, 1999; Keeton, 1983; Matlock, Terrell, Savell, Rhee, & Dutson, 1984; Ockerman et al., 1978; Smith et al., 2002). Pork loins enhanced with salt/WPC80 (D) had significantly higher juiciness ratings compared to the salt/b-lg enriched fraction (C) enhanced. In other studies, pork loins containing 10% water and up to 0.5% phosphate in the final products tended to have juicier chops (Jones et al., 1987; Sheard et al., 1999). Juiciness has also been improved in phosphate-enhanced pork in other studies (Smith et al., 1984; Sutton et al., 1997). The differences in overall flavour were small but significant (p < 0.024). Pork loins enhanced with phosphate and salt had a higher overall flavour rating in comparison to the control (‘‘very good’’ vs. ‘‘good’’). No difference was recorded between the salt/b-lg enriched fraction enhanced (C) and the salt/WPC80 enhanced (D) (p > 0.01). All the treatments were found to have either good or very good overall flavour rating. Keeton (1983) found that pork flavour was significantly improved by enhancement. More recently, however, Smith et al. (1984), Jones et al. (1987) and Sutton et al. (1997) reported that pork flavour was masked by addition of 0.4–0.475% STPP, i.e., had lower flavour intensity when compared to the controls. The enhanced pork loins were found to be lower (p < 0.001) in overall firmness when compared to the control. All of the enhanced pork loins were similar (p > 0.05) in overall firmness. The control (A) had the highest overall firmness rating of 6.3 and was significantly different to all the enhanced chops, which were found to be slightly firm with an average firmness rating of 5.4. The overall acceptability results indicate that the panellists found all the enhanced chops more acceptable to the control chops. STPP/salt enhanced (B) chops had significantly higher (p < 0.06) overall acceptability in comparison to the control (4.7 vs. 4.0). Smith et al. (2002) found that overall the enhanced products were very similar to each other and superior to the control products for sensory traits and WBSF measurements. Enhancement adds value to pork loins, but only if consumers perceive them to be as or more acceptable than control loins (Brewer et al., 2002). Glaeser et al. (2003) found that the overall eating quality of pork was markedly improved by needle injection of a brine solution, containing STPP and salt.
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Table 3 Enhancement effects on the sensory characteristics of pork loins Treatment A B C D
Tenderness
Juiciness
a
Control STPP/salt Salt/b-lg fraction Salt/WPC80 SED
a
4.8 6.7c 6.0b 6.8c 0.12
5.3 6.7c 6.1b 6.7c 0.12
Overall flavour
O/F
a
b
4.1 4.6b 4.3a 4.3a 0.09
6.3 5.4a 5.6a 5.3a 0.08
O/A
WBSF (N)
a
38.5b 24.7a 27.7a 24.9a 1.63
4.0 4.7b 4.3a 4.4a 0.09
O/F = overall firmness; O/A = overall acceptability; SED, standard of the difference of the means error. a,b Means in the same column with unlike superscripts are different (p < 0.001).
The responses in each category for each question in the consumer study have been presented as frequencies. Frequency distributions are useful with categorical data as they summarise all the responses to a survey question, which can then be tabulated. Sixty-three consumer evaluation sheets were sufficiently complete to use for data analysis. Fig. 1 shows the results of the frequency distributions. Seventy-eight percent of consumers rated the enhanced chop more tender over the control. Sixteen percent of those people commented on the fact that the enhanced pork chop was noticeably more tender than the control chop. This result is similar to that reported by the sensory analysis taste panel; where the three enhanced pork chops were significantly higher in tenderness rating compared to the control pork chop. Seventy-one percent of the consumers found the enhanced pork chops juicier than the control. Seven percent of consumers commented that the enhanced chop was juicier. This result is also comparable to the sensory taste panel, where the control pork chop had a significantly lower (p < 0.001) juiciness rating in comparison to all three of the enhanced chops. Sixty percent of the consumers rated the taste of the enhanced pork chop higher then control chop. Eighteen percent commented that the enhanced chop was nicer and tasted better than the control. In the sensory taste panel the overall flavour of the three enhanced pork chops (B, C, D) was rated higher then the control (A). When the consumers were asked which sample they preferred, 62% stated they preferred the enhanced pork chop (Fig. 2). Thirteen percent commented that both were acceptable and there was not a noticeable differ38%
Preference
62%
3.7. Colour determination L* values (lightness) of raw chops were unaffected by enhancement at day 1 or day 7 (Table 4). Prestat et al. (2002a) found that lightness was affected by both enhancement and storage time. Enhancement did have significant effects on both a* and b* values. Redness 70%
40%
Tastier
ence between the two samples. The sensory taste panel rated the overall acceptability of the control pork chop (A) lower compared to the three enhanced chops (B, C, D). Thirty-eight percent of respondents preferred the control sample, 32% stating that they would purchase the product, 6% stating that they would not purchase the product. Sixty-two percent of respondents stated that they preferred the enhanced sample, 60% stating that they would buy the product, while only 2% stated that they would not buy the product. Visual acceptability and consumer purchase intent of enhanced pork loin roasts was evaluated by Brewer et al. (2002). Approximately 67% of the respondents stated they would not buy ‘‘enhanced’’ pork. More than 55% ‘‘probably’’ or ‘‘definitely’’ would buy the displayed enhanced products used in the Brewer study, however they were unaware that the products were enhanced and were basing their judgments on appearance only. Enhancement adds value to pork loins but only if consumers perceive them to be more acceptable then unenhanced loins. Brewer et al. (2002) stated that the figures from their study indicated that there is a substantial market for enhanced products. However, some consumer education as to the nature and advantages of enhancement may be required.
2%
60%
60%
50%
29%
Juicier
40%
71%
20%
22%
More tender
6%
30%
60% 32%
10%
78%
0%
0%
10%
20%
30%
40%
Enhanced
50%
60%
70%
Control
Fig. 1. Consumer study on pork enhancement.
80%
90%
Preference A Would Buy
Preference B Would Not Buy
Fig. 2. Based on your preference would you purchase this product?
J.E. Hayes et al. / Meat Science 72 (2006) 380–386
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Table 4 The Effect of enhancement on the colour of pork chops
A B C D
Treatment
Day 1
Day 7
L*
a*
b*
L*
a*
b*
Control STPP/salt Salt/b-lg fraction Salt/WPC80 SED
60.5a 57.8a 58.0a 59.1a 0.70
5.3b 3.2a 5.5b 5.2ab 0.41
14.1b 11.9a 14.0b 14.0b 0.36
60.3a 58.5a 59.1a 60.2a 0.63
1.8a 2.2a 3.7b 3.8b 0.33
12.4ab 11.6a 12.6b 12.9b 0.20
SED, standard error of the difference of the means. a,b Means in the same column with unlike superscripts are different (p < 0.001).
(a*) decreased significantly (p < 0.05) in chops enhanced with salt/STPP (B) at day 1. However, redness at day 7 was increased significantly in chops enhanced with salt/ b-lg enriched fraction (3.7) (C) and salt/WPC80 (3.8) (D). Redness (a* values) decreased in all treatments between days 1 and 7 but in particular for control (A). Eckert, Maca, Miller, and Acuff (1997) also reported a decrease in redness (a*) as storage time increased. Yellowness (b*) at day 1 decreased significantly in chops enhanced with salt/STPP (B), however, yellowness (b*) at day 7 increased (p < 0.05) in chops enhanced with salt/b-lg fraction and salt/WPC80. These alterations are likely the result of pH alterations (increases) induced by phosphate addition. Prestat et al. (2002b) found that redness (a*) increased and yellowness (b*) decreased in chops enhanced with phosphate and salt at day 1. Carpenter, Saffle, and Kamstra (1961) and Krause, Ockerman, Krol, Moerman, and Plimpton (1978) reported similar results for L*, a* and b* values when evaluating phosphate effects on pork and beef. However, Sutton et al. (1997) reported that L*, a* and b* values for raw samples were unaffected by the addition of phosphate enhanced chops. Wang and Brewer (1999) reported that 0.1% phosphate did not affect yellowness (b* value), while 0.2% and 0.3% phosphate solutions significantly decreased it. Phosphate solutions generally increase product colour slightly, shifting the overall colour of red meat from lighter to darker. A proportion of this shift appears to be in the wavelength regions used to calculate b* value (yellowness) which may also account for the fact that phosphate-treated meat often appears darker than controls (Wang & Brewer, 1999). No visual colour effects were apparent between enhanced pork loin and the control loins. Brewer et al. (2002) found that 55% of consumers rated colour of enhanced loins as ‘‘somewhat acceptable (28%) or ‘‘very acceptable’’ (27%).
4. Conclusions Enhancing pork loins with solutions containing sodium polyphosphate, b-lg enriched fraction and
WPC80 enhanced sensory attributes of chops derived from them with few detrimental effects on physical and quality characteristics. Tenderness and juiciness were significantly increased (p < 0.001) with the enhancement of pork loins. b-lg enriched fractions and WPC80 can be used as potential replacement ingredients to reduce the amount of phosphate used in enhancement solutions, as they were comparable to salt/STPP enhancement solution. In the consumer study, consumers rated the tenderness, juiciness and taste of the enhanced chops significantly higher then the control chops. Sixty percent of the consumers preferred the enhanced pork chops. Sixty-two percent stated that they preferred the enhanced sample, 60% stating that they would buy the product, while only 2% stating that they would not buy the product. These findings indicate the potential of pork enhancement in meat products and the benefits enhancement would bring to the pork industry.
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