(Oncorhynchus mykiss) Fillet Firmness

Comparison of Variable-Blade to Allo-Kramer Shear Method in Assessing Rainbow Trout (Oncorhynchus mykiss) Fillet Firmness Aunchalee Aussanasuwannakul, Susan D. Slider, Mohamed Salem, Jianbo Yao, and Patrick Brett Kenney

Abstract: A variable-blade (VB) attachment was compared to the Allo-Kramer (AK) shear attachment for texture analysis of rainbow trout fillets from 2 experiments; effects of attachment configuration, storage regimen, and cooking temperature are evaluated. In the 1st experiment, AK detected differences in force measurement, and VB showed that the perpendicular orientation yielded the highest response (P < 0.05). Fillets refrigerated (4 ◦ C) for 0 d were firmer than fillets stored for 14 d (337.36 compared with 275.90 g/g). Raw fillets were firmer than cooked fillet (333.79 compared with 279.46 g/g). In the 2nd experiment, frozen storage at –25 ◦ C for 30 d after refrigerated storage (R3F30 and R7F30) decreased VB shear force (P = 0.0019) and AK energy of shear (P = 0.0001) by 1.5- and 2-fold compared to those evaluated after refrigerated storage for 3 and 7 d (R3 and R7), respectively. Cooking increased VB and AK texture for all storage regimens (P < 0.05). In both studies, instrumental texture did not correlate with alkaline-insoluble hydroxyproline (P > 0.05). Shear direction affected force generated by the VB attachment, and this attachment could discriminate shear force differences due to cooking and frozen-storage. Keywords: collagen, quality, rainbow trout, texture

Fillet texture was determined by a recently developed device and compared to texture determined by the Allo-Kramer shear attachment; both responses were related to collagen content. The VB attachment defined fillet texture as affected by cooking and storage condition.

Introduction An obstacle to shear force determination in aquatic food texture evaluation is associated with the low connective tissue content of fish fillets, differences in hierarchal arrangement of connective tissue, and a lack of interconnectedness caused by the myosepta that make it vulnerable to shear and compression force (Hultin 1985). Food texture is complex, involving multiparameter qualities (Guinard and Mazzucchelli 1996) and, as a result, it is important that the investigator is aware of what physical parameter is measured in an instrumental test. Variation in meat texture originates from inherent differences within the structure of raw meat/muscle tissue and this variation is related to contractile protein structures, connective tissue framework, lipid, and carbohydrate components, as well as external factors such as cooking and sample handling (Solomon and others 2008). Absence of consistent terminology for shear responses results in poor correlation between instrumental and sensory methods (Bourne 1975) and incorrect interpretation of texture data (Voisey 1976). Sometimes "shear" is used to describe any cutting action that causes the product to be divided

MS 20120367 Submitted 3/8/2012, Accepted 6/20/2012. Author Aussanasuwannakul is with Inst. of Food Research and Product Development, Kasetsart Univ., Bangkok 10900, Thailand. Authors Slider, Salem, Yao, and Kenney are with Div. of Animal and Nutritional Sciences, West Virginia Univ., Morgantown, WV 26506-6108, U.S.A. Direct inquiries to author Kenney (E-mail: [email protected]). R C 2012 Institute of Food Technologists Journal of Food Science No claim to original US government works doi: 10.1111/j.1750-3841.2012.02879.x

Further reproduction without permission is prohibited

into 2 pieces. Dunajski (1979) suggested that a shear test using thin blades is appropriate for the thin and short muscle fibers in fish. Fish musculature is comprised of myotomes (flakes) connected to each other through heat-labile connective tissue of the myosepta. Collagen is a major protein of connective tissue, constituting 3% to 10% of the protein in fish muscle, and it plays a key role in maintaining fillet integrity (Sikorski and others 1984). Hydroxyproline (HYP) and hydroxylysine contribute to the formation and stabilization of the collagen triple helix (Ramachandran 1988). During maturation, nonreducible, mature intermolecular cross-links form between collagen fibers (Bailey 2001). Collagen cross-links increase thermal stability of fish collagen (Ramachandran 1988). Hydroxylysylpyridinoline (PYD) crosslinks maintain the physical structure and rigidity of the collagen matrix (Bailey and others 1998) and positively correlate with texture of raw and cold smoked Atlantic salmon (Salmosalar L.) fillets (Li and others 2005; Johnston and others 2006) and texture of Atlantic halibut fillets (Hagen and others 2006). An increase in HYP insolubility reflects an increase in PYD concentration (Haugen and others 2006). In terrestrial animals, Purslow (1987) and Damez and Clerjon (2008) pointed out that variation in muscle fiber direction contributes to toughness anisotropy, and precautions have to be taken in orienting the probe to manage variation associated with shear direction. In fish, Taylor and others (2002) sheared (5-blade Kramer shear cell) the fillet perpendicular to the longitudinal axis to demonstrate detachment of myofibers from connective tissue in salmon muscle after 1- and 5-d storage on ice. Vol. 77, Nr. 9, 2012 r Journal of Food Science S335

S: Sensory & Food Quality

Practical Application:

Shear texture analysis of trout fillets . . .


Aussanasuwannakul and others (2010) demonstrated that shearcutting action imposed by the VB attachment is less destructive and correlates with sensory hardness (r = 0.423) of trout fillets. Although the VB attachment resulted in a lower shear value compared to AK, the VB attachment could reduce a substantial source of error associated with bulk shearing or compression, and thus improve accuracy of the texture measurement. A less destructive approach, using a VB shear-cutting method, was designed to overcome the limitation of (1) weak correlations between instrumental and sensory texture measurements and (2) insensitivity in determining contributions of collagen and myofibrillar proteins to fillet texture. This paper related instrumental texture to quality and quantity of the connective tissue protein, collagen. Fillet HYP concentration (quantity) and solubility (quality) were considered from 2 separate experiments that investigated the effect of attachment configuration, storage regimen, and cooking temperature. Treatment effects included attachment configuration, storage regimen, cooking temperature, and their interactions; the level of attachment configuration and storage regimen were different between the 2 experiments. VB was compared to AK in terms of (1) sensitivity in discriminating texture variation and (2) predictability in relating texture parameters to HYP content. To determine the relationship between texture and HYP quantity and quality, we related shear force and area under force-deformation curves to alkaline-soluble (a-s), alkaline-insoluble (a-i), and total HYP content of the fillet. For comparison to the AK, multiblade method, a VB attachment was designed with 2 key features for measuring fish texture. First, a thin blade (0.635 mm thick) allows shearing of muscle fibers without destroying fillet structure compared to thicker AK blades (3.0 mm thick). Second, twelve, 12.7 × 25.4 mm blades, arranged in 2 rows on the attachment, allow an incision width and depth that captures a wide range of texture variation within the fillet sample.

Materials and Methods Source of fish and fillet processing Experiment 1. Kamaloop rainbow trout, Oncorhynchus mykiss, (347 ± 35 g) were obtained from a local West Virginia producer. At harvest, fish were netted, mechanically stunned, and stored on ice for delivery to Morgantown, W.Va., an approximate 3.5 h trip. Fish were subsequently stored in coolers with ice overnight before filleting, approximately 18 h after harvest. Fish were filleted in rigor; we have observed deep rigor at 24 h in our lab and Skjervold and others have addressed the time course of rigor development in salmon (1999, 2001; 6 to 24 h after slaughter). In the fillet operation, vertebral column and ribs were removed manually, and skin remained intact. Following removal of the vertebral column and ribs, visible fat and skin were also separated from the musculature, and pin bones remained in the musculature. Whole-fish and fillet weights were collected. Subsequently, fillet halves were placed on Styrofoam trays, and the trays were then kept in polyethylene bags. Bags were sealed without vacuum and stored at 4 ◦ C according to the assigned refrigerated storage treatment. After each storage treatment, fillet half was cut equally into cranial and caudal portions. Using the lateral line as the reference, a 40 × 80 mm section, consisting of approximately the same amount of dorsal and ventral muscle, was removed from each portion. Average thickness of a fillet section was 15.7 mm (SD = 2.8, N = 56). Experiment 2. Fish sourcing, harvesting, and processing are described in Aussanasuwannakul and others (2010). Fish for this exS336 Journal of Food Science r Vol. 77, Nr. 9, 2012

periment were filleted at 4 h postharvest, and thus, were processed while in a prerigor state. For cooked evaluation, fillet sections were thermally processed in a microprocessor-controlled smoke oven (Model CVU-490; Enviro-Pak, Clackamas, Oreg., U.S.A.) set at 82 ◦ C, and the cooking process was stopped when internal fillet temperature reached 65.5 ◦ C. This cooking temperature was selected according to the USDA-recommended, minimum internal temperature for fish to achieve a safe temperature without overcooking (Nilsson and Ekstrand 1995). Cooking time was approximately 45 min.

Instrumental texture analyses Texture of raw and cooked fillet sections was measured at room temperature (25 ◦ C) using a variable, 12-blade (VB) and a 5-blade, Allo-Kramer (AK) shear attachment mounted to the TA-HDiR Texture Analyzer (Texture Technologies Corp., Scarsdale, N.Y., U.S.A.), equipped with a 50-kg load cell, at a crosshead speed of 127 mm/min. Muscle sections were sheared perpendicular to the long axis of the muscle. Force-deformation graphs were recorded and analyzed using the Texture Expert Exceed software (version 2.60; Stable Micro Systems Ltd., Surrey, U.K.). Parameters, determined from the graph, included (1) maximum shear force (g/g sample) and (2) area under the curve (g × mm) from 0 g force to maximum force. Following texture measurement, these samples were collected and pulverized with liquid nitrogen in a stainless steel, Waring Blender (Waring, New Hartford, Conn., U.S.A.). They were stored at –25 ◦ C for HYP analyses. In variable-blade (VK) shear evaluations, a fillet section was placed on a flat base (plastic cutting board). The fillet was adjusted in the blade holder frame (30 × 80 mm) so that the cutting area aligned consistently with the sample surface area. Five attachment configurations were Allo-Kramer (AKPER), VK with all 12 blades in perpendicular (12-VBPER) and parallel (12-VBPAR) orientations, and VK with 6 blades in perpendicular (6-VBPER) and parallel (6-VBPAR) orientations. In experiment 1, texture evaluation included all 5 attachment configurations; only AKPER and 12-VBPER configurations were selected for experiment 2 because these configurations could detect variation in fillet texture associated with cooking and storage condition (Aussanasuwannakul and others 2010). Test settings and acquired responses of the VB attachment were the same as AK evaluations, except the VB attachment was programmed to return to the starting point before the blades touched the base. Depth of penetration was standardized; average (N = 94) blade penetration into raw and cooked fillets was 15.7 ± 2.5 and 16.7 ± 2.7 mm, respectively. Five-blade, AK evaluations consisted of 5 blades passing through the fillet section and the slotted plate that is a part of the sample holder. After testing, the AK attachment returned to the starting point. Key features of VB and AK attachment and testing conditions are provided in Table 1. Muscle fat and moisture content Crude fat and moisture content of raw and cooked muscle was determined using AOAC (1990) approved methods. Crude fat was analyzed using the Soxhlet solvent extractor, and moisture was determined according to the oven-drying method (100 ◦ C for 18 h). Muscle HYP content HYP content was determined following the method of Li and others (2005). Sodium hydroxide (0.2 M) was used to separate HYP into a-s and a-i fractions. A 2-μL aliquot of hydrolysate was mixed with 200 μL of water and dried in an Eppendorf tube


Experimental design and statistical analysis The 1st experiment was conducted in the context of a 5 × 2 × 2 factorial, split-split-plot design. Attachment configuration (wholeplot factor; AKPER, 12-VBPER, 12-VBPAR, 6-VBPER, and 6-VBPAR), storage time (subplot factor; 0 and 14 d), and cooking temperature (sub-sub-plot factor; raw and 65.5 ◦ C) were randomly assigned to fish, fillet halves, and fillet sections (experimental units), respectively. A total of 63 fish used in the experiment rendered 272 fillet sections; texture and composition data were the average of 22 to 24 replicates (fillet sections). The 2nd experiment was conducted in the context of a 4 × 2 completely randomized design. Treatment effects were storage regimen and cooking temperature (raw and 65.5 ◦ C). The 4 storage regimens were (1) refrigerated, aerobic storage for 3 d, R3; (2) refrigerated aerobic storage for 7 d, R7; (3) refrigerated aerobic storage for 3 d followed by vacuum-packaged, frozen storage for 30 d; and (4) refrigerated storage for 7 d followed by vacuum-packaged, frozen storage for 30 d. For both experiments, treatment effects and their interaction on HYP concentration and instrumental texture were determined. Data were analyzed by analysis of variance (ANOVA) using the Mixed Model (MIXED) procedure of SASR system for Windows, version 9.1 (SAS Inst. Inc. 2004). Pearson product–moment correlation between fillet texture and composition was analyzed using CORR procedures of SASR system for Windows, version 9.1 (SAS Inst. Inc. 2004), respectively. Significance was defined at P < 0.05.

Table 1– Comparison of features of variable-blade and AlloKramer shear method for testing fillet firmness using the TA.HDi Texture Analyzer.a Method Test principle Fixture

Crosshead speed (mm/min) Parameter calculated from force-deformation curve Property measured a

Variable-blade

Allo-Kramer

Shear-cutting Twelve, 0.635-mm-thick, 12.7-mm-wide blades arranged in 2 rows 127

Shear Five, 3.0-mm-thick, 70-mm-wide blades

127

Maximum force (g/g), area under positive curve (g × mm)b

Maximum force (g/g), area under positive curve (g × mm)b

Firmness

Firmness

TA.HDi Setting: mode: measure force in compression; option: return to start; pre-test speed: 5 mm/s; test speed: 2 mm/s; post-test speed: 10 mm/s; distance: 45 mm; trigger type: button; data acquisition rate: 200 pps. b The area data was recorded starting when the blade touched sample (force = 0 g) until the maximum force was achieved. For both attachments, area under force-deformation curve after maximum force was excluded.

Results and Discussion Separating texture differences In experiment 1, storage time-by-attachment configuration and storage regimen-by-attachment configuration interactions affected shear force (P < 0.05; Figure 1 and 2). The VB attachment with all 12 blades attached (12-VBPER and 12-VBPAR) yielded a higher response than half the blades (6-VBPER and 6-VBPAR) in a similar orientation (P < 0.05). The perpendicular orientation yielded the highest (P < 0.05) response compared to those in a parallel orientation with the same number of blades. The AK attachment detected differences in texture between fresh and refrigerated fillets (P < 0.05; Figure 1), and between raw and cooked fillets (P < 0.05; Figure 2). Fresh fillets were firmer than fillets stored for 14 d (337.36 compared with 275.90 g/g; Figure 1). Softer fillets at 14 d were likely associated with autolytic changes that occurred throughout refrigerated storage. Raw fillets were firmer than cooked fillet (333.79 compared with 279.46 g/g; Figure 2). In experiment 2, the VB attachment detected an effect of storage regimen × cooking temperature on shear force (P = 0.0019); whereas, AK detected an effect of storage regimen × cooking temperature on energy of shear (P = 0.0001; Table 2). In the storage regimen study, frozen storage at –25 ◦ C for 30 d (F30) decreased VB shear force of raw fillets by 1.5-fold (P = 0.0019) and AK energy of shear (P = 0.0001) by 2-fold. Cooking increased VB shear force and AK energy of shear at all levels of storage regimen (P < 0.05) due to increased protein–protein interactions and concomitant decreases in protein–water and protein–lipid interactions associated with thermally induced protein denaturation. There is no general agreement about the exact mechanisms involved in the texture changes observed during ice storage of fish (Nollet and others 2007). Fish muscle generally becomes softer during chilled storage (Sato and others 1991; Ando and others 1992a, 1992b). During storage on ice, some myofibrillar proteins degrade; however, no changes had been observed in the structure of the contractile elements (Busconi and others 1989; Verrez-Bagnis 1997). Ando and others (1992b) found that differences in firmness among 3 fish species were related to density and arrangement of collagen fibrils in the connective tissue. Softening of rainbow trout postmortem is caused by a disintegration of collagen fibers (Ando and others 1992a, 1992b). During frozen storage, myofibrillar proteins and collagens aggregate, contributing to muscle toughening (Montero and others 1990; Montero and Border´ıas 1992). Disintegration of collagen fibrils and cleavage of cross-links are responsible for a decrease in firmness of frozen stored fillets (Ando and others 1992b; Bremner 1992, 1993; Ando and others 1999). Relationship of instrumental texture to HYP analysis In experiment 1, total HYP increased by 123.80% after cooking (P < 0.0001), and it was comprised of 97.35% a-s and 2.68% a-i HYP fractions. The increase in total HYP associated with cooking was likely due to a “concentrating” effect caused by water and fat loss during cooking (moisture loss = 6.35%; fat loss = 0.95%). In addition, cooking would have denatured (hydrolyzed) some collagen; increasing a-i HYP. Variation in muscle cellularity and associated changes in connective tissue matrix are important determinants of texture (Montero and others 1990; Johnston and others 1999; Hagen and others 2007). Texture determined by AKPER negatively correlated with fillet fat content (P = 0.0167; Table 3). Our previous findings suggest that muscle fat may dilute and lubricate structural elements of muscle and decrease fillet firmness Vol. 77, Nr. 9, 2012 r Journal of Food Science S337


using a centrifugal vacuum concentrator (EppendorfR 5301, ColeParmer, Ill., U.S.A.). This dried sample was resuspended in 200 μL of 0.1 M boric buffer, pH 11.4, containing 11.2 μM homoarginine as an internal standard. The fluorenylmethoxycarbonyl (FMOC) derivatized amino acids were separated using a ternary gradient described by Bank and others (1996). The eluate was monitored for fluorescence at λex = 254 nm and λem = 630 nm. The Varian Star Chromatograph Workstation software (version 6; Varian Inc., Calif., U.S.A.) was used to identify and quantify homoarginine and HYP peaks. Sample HYP concentration was quantified based on the relative signal areas of sample and internal standard (Harris 2007).

Shear texture analysis of trout fillets . . . in maturing trout females (Aussanasuwannakul and others 2011). Fillets with a high fat content (3.4% to 7.3% wet weight) were described as juicier than fillets with a low fat content (2.9% to 4.6% wet weight; Nortvedt and Tuene 1998). The intramuscular lipid fraction, through its rheological properties and its dilution of the collagen network in particular, has improved tenderness of meat from terrestrial animals (Koch and others 1989). Li and others (2005) showed that fast muscle fibers of salmon are covered with a continuous sheet of connective tissue and lipid droplets, particularly in the region of the myosepta. Therefore, it is possible that muscle fat (8% to 10%) offsets connective tissue’s effect on texture by diluting the connective tissue framework and providing lubrication. In experiment 2, cooking increased soluble HYP (cooking temperature effect; P = 0.0198) and total HYP (P = 0.0223; Table 2); a-s HYP and total HYP content increased by 1.4-fold after cooking. There was no effect of cooking temperature on a-i HYP content (P > 0.05). It is likely that storage regimen did not affect HYP content (P > 0.05) because other sources of variation (that is, moisture, fat, and so on) in HYP content were more important. Instrumental texture did not correlate with any HYP fraction (P > 0.05). However, we found that VB shear force correlated with sensory hardness (r = 0.423, P = 0.0394)

and cook loss (r = 0.412, P = 0.0450; Aussanasuwannakul and others 2011). Taylor and others (2002) demonstrated that distinct structural changes in ice-stored fillets, up to 14 d, were associated with breaks in myofiber-to-myofiber attachments, and later with breaks in myofiber-to-myocommata attachments. Limited variation in instrumental texture and fillet composition existed for fish in the experiment 2 data set; these fish were collected at the same age and were produced on the same nutritional regimen. Consequently, this limited variation in the sample set reduced our ability to establish a relationship between instrumental texture and HYP content. According to Hyldig and Nielsen (2007), fish muscle cells are very short (≤1 cm in large species), and they contain, primarily, stromal proteins of the myocommata and the myofibrillar protein, actomyosin; these proteins have very different effects on overall texture. A contribution of collagen to texture variation was seen in the aforementioned maturation study (Aussanasuwannakul and others 2011) and was detected by AK; whereas, results from this study suggested a greater contribution of myofibrillar protein and composition to fillet texture. With heating, collagen shrinks then softens; whereas, the actomyosin complex changes from a soft gel to a firmer gel (Dunajski 1979) as protein–protein interactions increase. Consequently, the contribution of stromal and myofibrillar


Figure 1–Shear force (g/g) determined by Allo-Kramer (AKPER) and variable-blade (VB) attachment. The nr. of blades and their orientation were changed to provide all 12 blades in perpendicular (12-VBPER) and parallel (12-VBPAR) orientation; the half nr. of blades in perpendicular (6-VBPER) and parallel (6-VBPAR) orientation. Fillets were refrigerated (4 ◦ C) for 0 and 14 d. Values are arithmetic mean averaged from 22 to 24 fillet sections. Error bar represents standard deviation. a–g Different letters are different (P < 0.05).

Figure 2–Shear force (g/g) determined by Allo-Kramer (AKPER) and variable-blade (VB) attachment. The nr. of blades and their orientation were changed to provide all 12 blades in perpendicular (12-VBPER) and parallel (12-VBPAR) orientation; the half nr. of blades in perpendicular (6-VBPER) and parallel (6-VBPAR) orientation. Texture was determined on raw and cooked fillets. Values are arithmetic mean averaged from 22 to 24 fillet sections. Error bar represents standard deviation. a–e Different letters are different (P < 0.05).

S338 Journal of Food Science r Vol. 77, Nr. 9, 2012


Possible use of VB shear-cutting method in fillet texture analysis The term “shear” implies that stresses are applied parallel to the direction of force and in the same plane as deformation (Voisey 1976); in “cutting-shear failure,” cutting action causes the product to be divided into 2 pieces (Bourne 2002). Clarifying the term “shear” reduces confusion regarding the deformation mechanism and therefore improves the accuracy of texture data interpretation. Using AK, deformation involves compression force that causes slippage at myotomes and includes contributions from various sources to overall texture (Aussanasuwannakul and others 2011). This study found that muscle fat content is a key contributor to texture variation when texture was evaluated with the AK attachment. Furthermore, due to greater sample involvement, AK efficiently evaluated fillet texture through assessment of the myofibrillar component. This study indicates that compression mechanics introduced by thicker blades of the AK compared to the VB attachment, influence texture evaluation of fillets with highly variable fat content. Robb and others (2002) reported that lipid content affected sensory perception of softness; however, this trend

was not found when using a flat-ended probe and a texture analyzer (Young and others 2005). The type of probe and texture test in the case of this study were knife probe and shear test, respectively. It can be concluded that blade thickness is important in observing effect of lubrication; therefore, type of probe and texture test must be clearly defined. Observations by Veland and Torrissen (1999) are consistent with our findings. These authors found that a shear test, using the 3-mm-thick Warner–Brazler blade, was more sensitive in separating texture differences between recently killed salmon and salmon stored on ice for up to 24 d than the compression test using a 25-mm spherical probe; Warner–Brazler probably applied large deformation with semisharp edges. However, these authors noted that the shear test is less effective than TPA in terms of imitating mastication. The shear test could not describe muscle elasticity because shear tests apply only one deformation to the sample and thus gives no measure of how much of the applied work is absorbed as elastic deformation, or how much work is required in successive chewing (Veland and Torrissen 1999). Shear, using a sharpened blade, was able to demonstrate effect of muscle location; the Warner–Bratzler method has a greater sensitivity over an unsharpened knife blade and over a cylinder method in discriminating fillet firmness from head to tail (Ashton and others 2010). In addition, these authors stated that collagen’s contribution to texture in salmon muscle could be detected by a shear method

Table 3–Pearson correlation coefficient (r) between instrumental texture measurements and fillet chemical composition. Instrumental texturea AKPER 12-VBPER

Hydroxyproline contentb Moisture

Fat

0.055 −0.165

−0.363 −0.057

∗

a-s

a-i

Total

0.235 0.155

−0.235 −0.155

−0.042 0.246

a

AKPER: Allo-Kramer; 12-VBPER: variable blade with all 12 blades arrangement in perpendicular direction to muscle fiber. Hydroxyproline was separated by 0.2 NaOH into alkaline-soluble (a-s) and alkalineinsoluble (a-i) fractions. ∗ P = 0.0167. N = 44 (AKPER) and 47 (12-VBPER). b

Table 2– Maximum shear force (g/g) and energy of shear (area; g × mm) determined by variable blade with all 12 blades in perpendicular orientation (12-VBPER) and Allo-Kramer (AKPER) attachment, and alkaline-soluble (a-s), alkaline-insoluble (a-i), and total hydroxyproline content (HYP; µmole/g) of raw and cooked fillets received different storage regimens. Storage regimen∗ / cooking temperature† Shear force (g/g) 12-VBPER AKPER Area (g × mm) 12-VBPER AKPER HYP Content (μmole/g) a-s a-i Total

R3

R7

R3F30

R7F30

Raw

Cooked

Raw

Cooked

Raw

Cooked

Raw

Cooked

123.64a (38.85) 210.69 (72.63)

230.82b (24.46) 399.67 (32.71)

129.53a (38.56) 208.69 (83.35)

246.11b (34.44) 450.84 (70.39)

79.94a (28.15) 163.8 (71.17)

329.12c (57.61) 520.54 (110.03)

90.89a (21.48) 133.77 (36.17)

279.54bc (92.65) 471.81 (52.81)

44008 (5.16E+03) 104421b (1.53E+04)

86788 (1.87E+04) 142805c (1.30E+04)

44752 (1.27E+04) 109137b (2.57E+04)

86329 (2.56E+04) 159112c (3.24E+04)

24283 (3.93E+03) 62167a (1.41E+04)

101350 (1.52E+04) 168122c (3.25E+04)

25975 (8.43E+03) 52739a (6.67E+03)

89536 (1.47E+04) 139789c (1.62E+04)

1455.86 (572.78) 93 (61.59) 1548.86 (595.73)

1919.79 (1050.1) 85.61 (90.42) 2005.39 (1024.51)

1361.11 (677.93) 89.09 (83.85) 1450.19 (715.83)

1929.36 (1173.59) 106.71 (82.91) 2036.07 (1168.27)

1541.01 (543.98) 131.5 (64.08) 1672.52 (577.38)

3318.6 (1790.9) 90.55 (59.59) 3409.15 (1802.09)

2401.43 (2012.48) 92.69 (79.63) 2494.12 (2035.8)

2645.58 (1969.75) 80.57 (61.43) 2726.15 (1967.28)

∗

R3: refrigeration at 4 ◦ C for 3 d; R7: refrigeration for 7 d; R3F30: refrigeration for 3 d followed by frozen storage at –25 ◦ C for 30 d; R7F30: refrigeration for 7 d followed by frozen storage for 30 d. samples were fresh (raw) fillets cooked until their internal temperature reached 65.5 ◦ C. Both raw and cooked fillets were analyzed at room temperature. Different superscripts of the same response denote significant differences (P < 0.05). Values are arithmetic mean (standard deviation) calculated from 6 fish for texture data and 9 fish for HYP data. † Cooked a,b,c

Vol. 77, Nr. 9, 2012 r Journal of Food Science S339


proteins to texture or their relative effect on fracture mechanism changes following cooking. Therefore, it is very difficult to relate textural attributes of raw fillets to attributes following cooking. When tenderness differences in meat are due to intrinsic determinants (that is, concentration of connective tissue, connective tissue cross-linking, intramuscular fat, and so on) that have similar effects on cooked and raw meat, measures of tenderness on raw meat will be particularly useful (Purchas 2004). In addition to cooking temperature, choice of instrumental method and test parameters determines how well instrumental muscle texture relates to intrinsic determinants. Ashton and others (2010) found that Warner–Bratzler shear data best predict texture of cold-smoked salmon fillet (r = 0.811, P < 0.001) compared to data from tensile tests and texture profile analyses (TPA), using a flat-ended cylinder.



using cutting probes that pass directly through any connective tissue in their path. Because cooking hydrolyzes collagen and causes fish muscle myotomes to separate easily and thereby affect sample fragility, lessdestructive analysis is the best approach to determine texture of a cooked fillet. In the AK shear tests using rounded blades, tensile and compression stresses as well as shear stresses contribute to the texture response; the thin blade of the VB attachment appears to be affected less by compression and tensile forces. The VB blade passes through muscle bundles and pin bones and, in cooked fillets, it was able to pass through the pellicle that formed on the surface of the cooked fillet. Consequently, this texture measurement appears to exclude tensile and compression components and improves correlation with sensory texture (Aussanasuwannakul and others 2010). In addition, comparing VB to AK texture will allow us to determine whether shear action needs a compression component. We found that the VB was able to discriminate between raw and cooked texture, and refrigerated and frozen-storage; however, VB texture could not be related to variation in muscle composition. VB is potentially the best approach to determine contributions of muscle fiber proteins to texture and to relate cooked to raw texture. In both experiments, the VB did not generate texture data that were related to HYP content. To reiterate, this inability to establish a relationship between HYP content and texture may be due to the narrow range in texture and collagen content present in these data sets. Moreover, the relatively high muscle fat content likely explained more texture variation than did collagen content and quality and myofibrillar tenderness. In muscle of females on a high plane of nutrition, fat content negatively correlated with shear force (r = –0.35, P = 0.0005), explaining 12% of the total variation (Aussanasuwannakul and others 2011). Future research needs to address the effect of fat on VB texture and compare texture determined by thin, sharp blades (VB) with thick, blunt (Warner–Bratzler) blades.

Conclusion The VB attachment exhibited a comparable sensitivity to the AK shear attachment in detecting variation in fillet texture. VB attachment was less destructive and could discriminate differences in fillet texture due to cooking and storage regimen. Collagen solubility was not related to fillet texture.

Acknowledgments This study was funded by USDA/CSREES#2007-3520517914 Natl. Research Initiative Competitive Grants Program, and supported by USDA/ARS CRIS Project 1930-32000-007 and Hatch funds (WVA00643) of the West Virginia University, Agriculture and Forestry Experiment Station. It is published with the approval of the West Virginia Univ. Director of the Agricultural Station as scientific paper nr. 3134. Mention of trade names of commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Dept. of Agriculture.

References Ando M, Toyohara H, Sakaguchi M. 1992a. Three-dimensional structure of collagen fibrillar network of pericellular connective tissue in association with firmness of fish muscle. Nippon Suisan Gakkaishi 58:1361–4. Ando M, Toyohara H, Sakaguchi M. 1992b. Post-mortem tenderization of rainbow trout muscle caused by disintegration of collagen fibers in the pericellular connective tissue. Bull Jpn Soc Sci Fish 58:567–70. Ando M, Toyohara H, Shimizu Y, Sakaguchi M. 1993. Post-mortem tenderization of fish muscle due to weakening of pericellular connective tissue. Nippon Suisan Gakkaishi 59:1073–6.

S340 Journal of Food Science r Vol. 77, Nr. 9, 2012

Ando M, Nishiyabu A, Tsukamasa Y, Makinodan Y. 1999. Post-mortem softening of fish muscle during chilled storage as affected by bleeding. J Food Sci 64:423–8. AOAC. 1990. Official methods of analysis. 15th ed. Washington, D.C.: Assn. of Official Analytical Chemists. Ashton TJ, Michie I, Johnston IA. 2010. A novel tensile test method to assess texture and gaping in salmon fillets. J Food Sci 75(4):S182–90. Aussanasuwannakul A, Kenney PB, Brannan RG, Slider SD, Salem M, Yao J. 2010. Relating instrumental texture, determined by variable-blade and Allo-Kramer shear attachments, to sensory analysis of rainbow trout, Oncorhynchusmykiss, fillets. J Food Sci 75(7): S365–74. Aussanasuwannakul A, Kenney PB, Weber GM, Yao J, Slider SD, Salem M. 2011. Effect of sexual maturation on growth, fillet composition, and texture of rainbow trout (Oncorhynchus mykiss) on a high nutritional plane. Aquaculture 317:79–88. Bailey AJ. 2001. Molecular mechanisms of ageing in connective tissues. Mech Ageing Dev 122:735–55. Bailey AJ, Paul RG, Knott L. 1998. Mechanisms of maturation and ageing of collagen. Mech Ageing Dev 106:1–56. Bank RA, Jansen EJ, Beekman B, te Koppele JM. 1996. Amino acid analysis by reverse-phase high-performance liquid chromatography: improved derivatization and detection conditions with 9-fluorenylmethyl chloroformate. Analytical Biochem 240:167–76. Bourne MC. 1975. Texture measurements in vegetables. In: Rha C, editor. Theory, determination and control of physical properties of food materials. Dordrecht, Netherlands: Reidel Publ. p 131–162. Bourne M. 2002. Food texture and viscosity: concept and measurement. 2nd ed. New York: Academic Press. 445 p. Bremner HA. 1992. Fish flesh structure and the role of collagen: its post mortem aspects and implication for fish processing. In: Huss HH, editor, Quality assurance in the fish industry. Amsterdam: Elsevier. p 39–62. Busconi L, Folco EJ, Martone CB, Sanchez JJ. 1989. Postmortem changes in cytoskeletal elements of fish muscle. J Food Biochem 13:443–51. Damez JL, Clerjon S. 2008. Meat quality assessment using biophysical methods related to meat structure. Meat Sci 80:132–49. Dunajski E. 1979. Texture of fish muscle. J Texture Stud 10:301–18. Guinard J-X, Mazzucchelli R. 1996. The sensory perception of texture and mouth-feel. Trends Food Sci Technol 7:213–9. Hagen ø, Solberg C, Johnston IA. 2006. Sexual dimorphism in fast muscle fibre recruitment in farmed Atlantic halibut (Hippoglossus hippoglossus L.). Aquaculture 261:1222–9. Hagen ø, Solberg C, Sirnes E, Johnston IA. 2007. Biochemical and structural factors contributing to seasonal variation in the texture of farmed Atlantic halibut (Hippoglossushippoglossus L.) flesh. J Agric Food Chem 55:5803–8. Harris DC. 2007. Quantitative chemical analysis. 7th ed. New York: W.H. Freeman and Co. Haugen T, Kiessling A, Olsen RE, Røra MB, Slinde E, Nortvedt R. 2006. Seasonal variation in muscle growth dynamics and selected quality attributes in Atlantic halibut (Hippoglossushippoglossus L.) fed dietary lipids containing soybean and/or herring oil under different rearing regimes. Aquaculture 261:565–79. Hultin HO. 1985. Characteristics of muscle tissue. In: Fennema OR, editor. Food chemistry. New York: Marcel Dekker. p 725–789. Hyldig G, Nielsen D. 2007. Texture of fish, fish products, and shellfish. In: Nollet LM editor. Handbook of meat, poultry and seafood quality.1st ed. Ames, Iowa: Blackwell Publishing. p 549–561. Johnston IA, Strugnell G, McCracken ML, Johnstone R. 1999. Muscle growth and development in normal-sex-ratio and all-female diploid and triploid Atlantic salmon. J Exp Biol 202:1991–2016. Johnston IA, Li X, Vieira VLA, Nickell D, Dingwall A, Alderson R, Campbell P, Bickerdike R. 2006. Muscle and flesh quality traits in wild and farmed Atlantic salmon. Aquaculture 256:323–36. Koch RM, Crouse JD, Dikeman ME, Cundiff LV, Gregory, KE. 1989. Effects of marbling on sensory panel tenderness in Bos taurus and Bos indicus crosses. J Anim Sci 66(Suppl.):305(Abstr.). Li X, Bickerdike R, Lindsay E, Campbell P, Nickell D, Dingwall A, Johnston IA. 2005. Hydroxylysylpyridinoline cross-link concentration affects the textural properties of fresh and smoked Atlantic salmon (Salmosalar L.) flesh. J Agric Food Chem 53:6844–50. Montero P, Border´ıas J. 1992. Influence of myofibrillar proteins and collagen aggregation on the texture of frozen hake muscle. In: Huss HH, Jakobsen M, Liston J, editors. Quality assurance in the fish industry. Amsterdam: Elsevier Science Publisher BV. p 149–167. Montero P, Border´ıas J, Turnay J, Leyzarbe MA. 1990. Characterization of hake (Merluccius merluccius L.) and trout (Salmo irideus) collagen. J Agric Food Chem 38:604–9. Nilsson K, Ekstrand B. 1995. Sensory and chemically measured effects of different freeze treatments on the quality of farmed rainbow trout. J Food Qual 18:177–91. Nollet LML, Boylston T, Chen F, Coggins PC, Gloria MB, Hyldig G, Kerth CR, McKee LH, Hui YH. 2007. Handbook of meat, poultry and seafood quality. Ames, Iowa: Blackwell Publishing. 744 p. Nortvedt R, Tuene S. 1998. Body composition and sensory assessment of three weight groups of Atlantic halibut (Hippoglossushippoglossus) fed three pellet sizes and three dietary fat levels. Aquaculture 161:295–313. Purchas RW. 2004. Tenderness measurement. In: Jensen WK, editor. Encyclopedia of meat sciences. Oxford: Elsevier Ltd. p 1370–1377. Purslow PP. 1987. The fracture properties and thermal analysis of collagenous tissues. Adv Meat Res 4:187–208. Ramachandran GN. 1988. Stereochemistry of collagen. J Peptide Prot Res 31:1–16. Robb DHF, Kestin SC, Warriss PD, Nute GR. 2002. Muscle lipid content determines the eating quality of smoked and cooked Atlantic salmon (Salmosalar). Aquaculture 205:345–58. R 9.1 user’s guide. 1st ed. SAS Publishing, N.C. SAS Inst. Inc. 2004. SAS/STAT Sato K, Ohashi C, Ohtsuki K, Kawabata M. 1991. Type V collagen in trout (Salmogairdneri) muscle and its solubility change during chilled storage of muscle. J Agric Food Chem 39:1222–5. Sikorski ZE, Scott DN, Buisson DH. 1984. The role of collagen in the quality and processing of fish. CRC Crit Rev Food Sci Nutr 20:301–43. Skjervold PO, Fjæra SO, Østby PB. 1999. Rigor in Atlantic salmon as affected by crowding stress prior to chilling before slaughter. Aquaculture 175:93–101. Skjervold PO, Fjæra SO, Østby PB, Einen O. 2001. Live chilling and crowding in Atlantic salmon before slaughter. Aquaculture 192:265–80.

Shear texture analysis of trout fillets . . . gaard P, Careche M, Verrez-Bagnis V, Martinsd´ottir E, Heia K, editors. Methods to determine the freshness of fish in research and industry. Paris: Intl. Inst. of Refrigeration. p 229–237. Voisey PW. 1976. Engineering assessment and critique of instruments used for meat tenderness evaluation. J Text Stud 7:11–48. Young A, Morris PC, Hungerford FA, Sinnott R. 2005. The effects of diet, feeding regime and catch-up growth on flesh quality attributes of large (1+ sea winter) Atlantic salmon, Salmosalar. Aquaculture 248:59–73.


Solomon MB, Eastridge JS, Paroczay EW, Bowker BC. 2008. Measuring meat texture. In: Nollet LML, Toldra F, editors. Handbook of muscle foods analysis. Boca Raton, Fla.: CRC Press. p 479–502. Taylor RG, Fjaera S, Skjervold PO. 2002. Salmon fillet texture is determined by myofibermyofiber and myofiber-myocommata attachment. J Food Sci 67:2067–71. Veland JO, Torrissen OJ. 1999. The texture of Atlantic salmon (Salmosalar) muscle as measured instrumentally using TPA and Warner-Bratzler shear test. J Sci Food Agric 79:1737–46. Verrez-Bagnis V. 1997. Post mortem denaturation of fish muscle proteins: changes in some myofibrillar, intermediate filament and costameric proteins. In: Olafsd´ottir G, Luten J, Dal-

Vol. 77, Nr. 9, 2012 r Journal of Food Science S341