Consumer and trained panel evaluation of beef strip steaks of varying marbling and enhancement levels cooked to three degrees of doneness

Meat Science 122 (2016) 145–154

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Consumer and trained panel evaluation of beef strip steaks of varying marbling and enhancement levels cooked to three degrees of doneness L.W. Lucherk a, T.G. O'Quinn b,⁎, J.F. Legako c, R.J. Rathmann a, J.C. Brooks a, M.F. Miller a a b c

Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX 79409, USA Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS 66506, USA Department of Nutrition, Dietetics & Food Sciences, Utah State University, Logan, UT 84322, USA

a r t i c l e

i n f o

Article history: Received 28 August 2015 Received in revised form 11 August 2016 Accepted 12 August 2016 Available online 14 August 2016 Keywords: Beef Consumer Degree of doneness Enhancement Marbling Palatability

a b s t r a c t The palatability of USDA graded beef strip loins of seven treatments [High Enhanced (HE: 112% of raw weight) Select, Low Enhanced (LE: 107% of raw weight) Select, Prime, upper 2/3 Choice (Top Choice), lower 1/3 Choice (Low Choice), Select, and Standard] cooked to three degrees of doneness [DOD; rare (60 °C), medium (71 °C), or well-done (77 °C)] was evaluated by consumer and trained sensory panelists. For consumers, Select HE steaks rated higher (P b 0.05) for juiciness, tenderness, flavor identity, flavor liking, and overall liking than all nonenhanced treatments other than Prime. No differences (P N 0.05) were observed between Select LE and Prime samples for most traits evaluated. The effect of USDA grade and enhancement on trained panel palatability scores was independent of DOD for all traits other than juiciness, with the role of marbling in juiciness increasing as DOD increased from rare to well-done. These results indicate enhancement as an effective method to improve the palatability of lower grading beef. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction Increased marbling (intramuscular fat) level and USDA quality grade have repeatedly been shown to be associated with increased beef eating quality (O'Quinn et al., 2012; Savell et al., 1987; Smith et al., 1985). Thus, higher marbled USDA Choice and Prime beef from the loin and rib is marketed at premiums ranging from 5 to 48% higher than USDA Select product (USDA, 2015a). Additionally, USDA Select beef has been shown to fail to meet consumer eating expectations more than 33% of the time (Corbin et al., 2015). Currently, more than 24% of young, U.S. grain-finished cattle grade USDA Select or lower (USDA, 2015c). With increasing beef prices and consumer quality demands, the need for improving the palatability of this lower quality beef is greater than ever before. For the past decade, the pork and poultry industries in the U.S. have used enhancement technology extensively as a means to improve product quality and reduce variation in eating experience (National Cattlemen's Beef Association, National Pork Board,, & Sealed Air Corporation, 2010). Numerous studies have demonstrated increased tenderness, juiciness, and flavor traits for enhanced pork products (Cannon, McKeith, Martin, Novakofski, & Carr, 1993; Detienne &

⁎ Corresponding author. E-mail address: [email protected] (T.G. O'Quinn).

http://dx.doi.org/10.1016/j.meatsci.2016.08.005 0309-1740/© 2016 Elsevier Ltd. All rights reserved.

Wicker, 1999; Sheard, Nute, Richardson, Perry, & Taylor, 1999; Sutton, Brewer, & McKeith, 1997) as well as increased cooking yields (Cannon et al., 1993; Detienne & Wicker, 1999). Moreover, similar reports have shown beef injected with salt and sodium phosphate solutions exhibit noteworthy improvements in water binding ability, shear force, and sensory panel juiciness, flavor, and tenderness scores (Brooks et al., 2010; Robbins et al., 2003; Trout & Schmidt, 1986; Vote et al., 2000). Additionally, beef injected with CaCl2 solutions have also been shown to improve beef palatability (Carr, Crockett, Ramsey, & Miller, 2004; Kerth, Miller, & Ramsey, 1995; Miller, Huffman, Gilbert, Hamman, & Ramsey, 1995). However, much of this previous work has focused on comparing enhanced beef products to a limited number of USDA quality grades or treatments. Consumer perception of beef palatability is highly influenced by degree of doneness (DOD) preference, with close to 40% of consumers reporting they prefer beef steaks cooked to at least a “medium-well” DOD (Cox, Thompson, Cunial, Winter, & Gordon, 1997; Reicks et al., 2011). It is well established that cooking to elevated DOD often results in reduced beef palatability (Cross, Stanfield, & Koch, 1976; Lorenzen et al., 1999; Luchak et al., 1998). However, published reports evaluating the effects of enhancement and USDA quality grade on beef palatability across a wide range of DOD are limited. It was therefore the objective of this study to compare the palatability traits of enhanced USDA Select strip loin steaks to steaks from other USDA quality grades when cooked to three DOD.

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2. Materials and methods 2.1. Product Beef strip loins (Institutional Beef Purchase Specifications #180; NAMP, 2010) were selected to equally represent seven quality treatments for use in this study. Treatments included five USDA quality grades [Prime, upper 2/3 Choice (Top Choice), lower 1/3 Choice (Low Choice), Select, and Standard], as well as two enhanced USDA Select treatments [Select High Enhanced (HE): 112% of initial product weight and Select Low Enhanced (LE): 107% of raw product weight]. Strip loins (n = 12/treatment) were selected by Texas Tech University (TTU) personnel at a commercial beef processing plant in Nebraska, USA. All strip loins were vacuum-packaged and transported, under refrigeration (2 °C), to the TTU Gordon W. Davis Meat Science Laboratory. Strip loins not intended for enhancement were aged 21 d postmortem under vacuum at 2 to 4 °C in the absence of light. At day seven of the aging period, USDA Select strip loins in the HE and LE treatment groups (n = 12/level) were enhanced with a water, salt (Morton Coarse Kosher Salt, Morton, Inc., Chicago, IL), and sodium tripolyphosphate (Brifisol 916, ICL Food Specialties, Simi Valley, CA) solution to an average of 112% (±2.2%) and 107% (±1.6%) of raw weight. Each solution was formulated to contain 0.3% salt and 0.45% sodium tripolyphosphate on a finished weight basis, with a target pump level of 15% (HE) and 8% (LE). Pump solutions were mixed with a commercial mixer (Model RS-02, Admix, Manchester, NH) until all solutes were dissolved and chilled (2 to 4 °C) for 24 h prior to pumping. Pump solution (HE: pH = 7.52; LE: pH = 7.23) was injected into strip loins using a multi-needle injector system (Schroder Model IMAX 350, Wolf-Tec Inc., Kingston, NY). Strip loins were weighed before and after enhancement to determine solution uptake. Injected loins were allowed to rest for 30 min at 2 to 4 °C before recording final weights. Injected strip loins were vacuum-packaged and stored at 2 to 4 °C in the absence of light for the remainder of the 21-d aging period. After completion of the 21-d aging period, all strip loins were fabricated into 2.5-cm thick steaks. The most anterior “wedge” steak was cut by hand and used for proximate analyses. The remaining strip loin was fabricated into nine 2.5-cm thick steaks from anterior to posterior. Groups of three consecutively cut steaks (steaks 1, 2, and 3; steaks 4, 5, and 6; steaks 7, 8, and 9) were assigned to one of three DOD [rare (60 °C), medium (71 °C), or well-done (77 °C)]. One of the three steaks from each DOD group was assigned to consumer panel, trained panel, and slice shear force (SSF) testing. All steaks were individually labelled, vacuum-packaged, and frozen (−20 °C). 2.2. Proximate analysis Steaks for proximate analysis were thawed for 24 h at 2 to 4 °C. Proximate analysis was tested using the wedge steak from each strip loin that was ground through a 4-mm plate. Prior to grinding, all external fat, heavy connective tissue, and multifidus dorsi were removed, leaving only the longissimus lumborum for analysis. Proximate analysis of raw steaks was conducted by an AOAC official method (Anderson, 2007) using a near infrared spectrophotometer (FoodScan, FOSS NIRSystems, Inc., Laurel, MD). Chemical percentages of fat, moisture, and protein were determined for each strip loin. 2.3. Slice shear force analysis Before cooking, steaks were thawed at 2 to 4 °C for 24 h and were trimmed to remove external fat. Thawed weight and raw initial temperature (Digital Meat Thermometer Model SH66A, Cooper Instruments, Middlefield, CT) were recorded. The steaks were cooked on a belt grill (model TBG- 60 Magigrill, Magi-Kitch'n Inc., Quakertown, PA) to achieve a final internal temperature of 60 °C (rare), 71 °C (medium), or 77 °C (well-done). Steak weights and peak internal temperatures

were recorded following cooking for calculation of cook loss (data not reported) and endpoint temperature. Tenderness was evaluated by SSF as described by Shackelford et al. (1999). In brief, three min after cooking, a 1–2 cm slice was removed across the width of the steak from the lateral end to square off the steak and expose the muscle fibers. Using a cutting guide, a 5-cm long × 1-cm thick section was obtained from the lateral end by cutting at a 45° angle parallel to the muscle fiber orientation. The sample was center-sheared perpendicular to the muscle fiber orientation using a United Force Analyzer (Model #SSTM-500 with tension attachment, United Calibration Corp., Huntington Beach, CA) with a cross head speed of 500 mm/min with a load cell of 490.33 N. 2.4. Consumer sensory evaluation The TTU Institutional Review Board approved procedures for use of human subjects for sensory panel evaluations (IRB 503992). Consumer panels were conducted at the TTU Animal and Food Science Building in a large banquet room under florescent lighting. Panelists (N = 252) were recruited from communities in and around Lubbock, TX and paid cash to participate in the study. Consumers were screened during recruiting for DOD preference and served only samples cooked to their preferred DOD. Panel sessions were conducted with 28 consumers seated in individual sensory booths and lasted about 1 h. Panels took place on three separate nights with three sessions conducted each night. Each set of three sessions in a night represented one of the three predetermined DOD and consisted of only consumers who were prescreened and preferred the DOD used. Consumers were provided with a ballot, plastic fork, toothpick, napkin, expectorant cup, cup of water, and palate cleansers (unsalted crackers and apple juice) to use between samples. Each paper ballot packet contained an information sheet, demographic questionnaire, beef steak purchasing behavior sheet, and seven sample ballots. Before the start of each panel, panelists were given verbal instructions regarding the ballot and usage of the palate cleansers. Steaks for consumer evaluation were prepared as previously described in Section 2.3. Four steaks were placed on the belt grill every 5 min approximately 2.5 cm away from each other. Following the rest period, 14 1.27-cm2 × 2.5-cm pieces were cut from each steak and two pieces were served immediately to each of seven predetermined consumers. No consumer was seated adjacent to another consumer evaluating the same steak sample. Consumers were served one sample from each of the quality grades (USDA Prime to Standard), a HE Select and LE Select in a predetermined, random order. Attributes for each sample were ranked on a paper ballot with 100-mm continuous-line scales labelled only at end-points for juiciness, tenderness, flavor identity, flavor liking, and overall liking. The zero anchors were labelled as not juicy, not tender, extremely unbeef-like, dislike flavor extremely, and dislike overall extremely; the 100-mm anchors were labelled as very juicy, very tender, extremely beef-like, like flavor extremely, and like overall extremely. Additionally, consumers were asked if each palatability trait was acceptable (yes or no). Furthermore, consumers classified each sample as either unsatisfactory, everyday quality, better-thaneveryday quality, or premium quality. 2.5. Trained sensory evaluation Panelists were trained according to the Research Guidelines for Cookery, Sensory Evaluation, and Instrumental Tenderness Measurements of Meat (AMSA, 2015). Panelists were trained in a total of six to eight, 1 h training sessions in the 10 days immediately preceding testing. In each training session, panelists evaluated beef steak samples representing a wide range of juiciness, tenderness, and flavor traits and included steaks from various muscles (psoas major, semitendinosus, gluteus medius, and longissimus lumborum), degrees of doneness [rare (60 °C) , medium (71 °C), and well-done (77 °C)]

L.W. Lucherk et al. / Meat Science 122 (2016) 145–154

and enhancement levels (0%, 7%, and 12%). Following training, 36 (12/ DOD) panel sessions consisting of a 7 to 10-member trained panel were conducted. In each session, panelists evaluated one sample from each of the seven quality treatments, with all samples evaluated within each session cooked to the same DOD. Steaks for trained sensory evaluation were prepared as previously described in Section 2.3. Steaks were cut into 1.27-cm2 × 2.5-cm pieces and held in poaching pans filled with sand at approximately 49 °C in a warming oven (Alto-shaam Halo heat, Menomonee Falls, WI) for no more than 10 min prior to serving to panelists. Each panelist received two pieces from each treatment in a random order. During testing, panelists were seated in individual sensory booths within a clean sensory panel room. Samples were served under low intensity (b107.64 lm) red incandescent light to mask color variation among samples. Panelists were provided with a ballot, plastic fork, toothpick, napkin, expectorant cup, cup of water, and palate cleansers (unsalted crackers and apple juice) to use between samples. Attributes for each sample were ranked on a paper ballot with 100mm continuous-line scales for initial juiciness, sustained juiciness, initial tenderness, sustained tenderness, and beef flavor intensity (Table 1). The zero anchors were labelled as not juicy, not tender, and extremely bland beef-like flavor; the 100-mm anchors were labelled as very juicy, very tender, and extremely intense beef flavor. Each scale was unstructured, with no additional line marks provided other than end-points. Panel sessions were conducted once or twice per day, with at least 3 h between panel sessions, and lasted approximately 30 min, with approximately 4–5 min between each sample served. 2.6. Statistical analysis Statistical analyses were conducted using the procedures of SAS (Version 9.3; SAS Inst. Inc., Cary, NC). Treatment comparisons were tested for significance using PROC GLIMMIX with α = 0.05. Proximate composition data was analyzed with a model that included the fixed effect of quality treatment. Consumer panel data was analyzed within each DOD panel with a model that included the fixed effect of quality treatment and the random effects of panel session number and sample order. Acceptability data for each palatability trait was analyzed with a model that included a binomial error distribution. Trained sensory data were analyzed with a split-plot arrangement of factors, with the whole-plot factor of DOD and the sub-plot factors of quality treatment

Table 1 Definitions and selected references for beef palatability traits evaluated by trained sensory panelists. Attribute

Definition

Initial Tenderness level of the sample within tenderness the first 1–3 chews

Sustained Tenderness level of the sample tenderness throughout the entire chewing process Initial juiciness

Juiciness level within the first 1–3 chews

Sustained juiciness

Juiciness level maintained by the sample throughout the entire chewing process

Beef flavor intensitya a

Amount of beef flavor identity in the sample

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and the DOD × quality treatment interaction according to the methods described by Steel, Torrie, and Dickey (1997) and Federer and King (2007) with panel session number and sample order included in the model as random effects. For all analyses, the Kenward–Roger approximation was used for estimating denominator degrees of freedom and the PDIFF option was used to separate treatment means when the Ftest on the main effect or effect interaction was significant (P b 0.05). Consumer demographic information was summarized for each DOD panel using PROC FREQ. PROC CORR was used for calculating and determining significance (P b 0.05) of all Pearson correlation coefficients. 3. Results 3.1. Product characteristics The percentage of fat, moisture, and protein for raw samples from each treatment are presented in Table 2. Due to treatment differences in USDA quality grade, fat percentage differed (P b 0.05) widely among treatments, ranging from 1.82% in Standard to 11.26% in Prime. However, no difference (P N 0.05) in fat percentage was observed among Select, Select HE, and Select LE samples. The fat percentages observed in the current study were similar to those reported by previous authors for longissimus lumborum steaks from the same USDA quality grades (Emerson, Woerner, Belk, & Tatum, 2013; O'Quinn et al., 2012; Savell, Cross, & Smith, 1986). Moisture content decreased (P b 0.05) in non-enhanced samples as USDA quality grade increased from Standard (73.54%) to Prime (65.84%). However, enhancement resulted in a 2% increase (P b 0.05) in moisture content for Select HE samples compared to non-enhanced Select samples. Despite a 0.5% mean increase, Select LE samples were similar (P N 0.05) to non-enhanced Select samples for moisture content. Protein percentage differed (P b 0.05) among treatments, however, the difference was minimal, with the two most varied treatments (Prime and Low Choice) differing by less than 2%. 3.2. Slice shear force A quality treatment × DOD interaction was found for SSF (P b 0.05; Table 3). When cooked to rare, Prime, Top Choice, Select, and Standard steaks were similar (P N 0.05) for SSF. However, when steaks were cooked to well-done, SSF values decreased (P b 0.05) with increased quality grade in non-enhanced samples. Enhanced treatments (HE and LE) had the lowest numerical SSF values at each DOD and were found more tender (P b 0.05) than Top Choice, Select, and Standard steaks at each DOD. Additionally, at well-done, Select HE steaks were more tender (P b 0.05) than all treatments other than Select LE.

Reference Beef tenderloin cooked to 71 °C = 95–100 Beef strip loin steak cooked to 71 °C = 60–65 Beef tenderloin cooked to 71 °C = 95–100 Beef strip loin steak cooked to 71 °C = 55–60 Beef strip loin steak cooked to 71 °C = 50–55 Enhanced (12%) beef strip loin cooked to 71 °C = 65–70 Beef strip loin steak cooked to 71 °C = 45–50 Enhanced (12%) beef strip loin cooked to 71 °C = 60–65 Swanson's beef broth = 31 80% lean ground beef = 44 Beef brisket = 69

Adapted from beef identity described by Adhikari et al. (2011).

Table 2 Least squares means for proximate analysis of raw beef strip loin steaks of varying quality treatments. Quality treatment

Prime Top choice1 Low choice Select Standard Select HE2 Select LE2 SEM3 P-value

% Fat

Moisture

Protein

11.26a 7.54b 4.79c 3.17d 1.82e 2.97d 3.49d 0.35 b0.0001

65.84e 68.35d 70.45c 71.73b 73.54a 73.77a 72.26b 0.34 b0.0001

21.85c 22.81b 23.77a 23.54a 23.50a 21.86c 22.35bc 0.18 b0.0001

abcde Least squares means in the same column without a common superscript differ (P b 0.05). 1 USDA marbling score of modest00–moderate100. 2 HE = High Enhanced (112% of raw weight), LE = Low Enhanced (107% of raw weight) with a salt, alkaline phosphate and water solution. 3 SE (largest) of the least squares mean.

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Table 3 Least squares means for slice shear force interaction (P = 0.0406) of degree of doneness and quality treatment for beef strip loin steaks. Degree of doneness/quality treatment Rare (60 °C) Prime Top Choice1 Low Choice Select Standard Select HE2 Select LE2 SEM3 P-value Medium (71 °C) Prime Top Choice1 Low Choice Select Standard Select HE2 Select LE2 SEM3 P-value Well-done (77 °C) Prime Top Choice1 Low Choice Select Standard Select HE2 Select LE2 SEM3 P-value

Slice shear force, N 114.44abc 125.13a 99.24bc 122.09ab 121.80ab 89.83c 92.08c 8.92 0.0095 93.26cd 108.85abc 103.66bcd 131.80a 128.07ab 79.43d 82.18d 8.92 b 0.0001 100.22cd 123.56bc 113.27cd 146.71ab 167.11a 71.69e 88.65de 8.92 b 0.0001

Table 4 Demographic characteristics of consumers (N = 252; 84/degree of doneness) who participated in consumer sensory panels. Characteristic

Medium (71 °C)

Well-done (77 °C)

% of % of % of consumers consumers consumers Gender Household size

Marital status Age

Ethnic origin

Annual household income

Education level

Weekly beef consumption

3.3. Consumer demographics and motivators when purchasing beef Table 4 contains demographic results obtained from the 252 consumers that participated in consumer sensory testing. For all DOD panels, sensory analysis was performed by majority Caucasian/White (92.8%, 91.5%, 73.8%) and married (72.6%, 65.1%, 59.5%) consumers for the rare, medium, and well-dome panels, respectively. Most consumers (N53%) within each DOD panel had an annual household income of $50,000 or more, had some college/technical school education (N20%) or were college graduates (N24%). Additionally, in each DOD panel, close to half (rare = 51.2%; medium = 47.6%; well-done = 48.8%) of panelists consumed beef at least 4 times a week, with the remainder of panelists consuming beef 1 to 3 times a week. The large majority (N 66% in each DOD panel) of consumers in this study identified beef as the product they preferred for flavor, followed by chicken (b16%), and pork (b8.5%). For both the medium and well-done panels, consumers identified tenderness as the most important palatability trait when eating beef. However, in rare panels, flavor (50%) was identified as most important by more consumer than tenderness (39.3%) or juiciness (10.7%). It is noteworthy that in the current study, despite differences in DOD preference, consumer demographic profiles were similar

Degree of doneness panela Rare (60 °C)

abcde Least squares means in the same section without a common superscript differ (P b 0.05). 1 USDA marbling score of modest00–moderate100. 2 HE = High Enhanced (112% of raw weight), LE = Low Enhanced (107% of raw weight) with a salt, alkaline phosphate and water solution. 3 SE (largest) of the least squares means.

Overall, well-done steaks were tougher (P b 0.05) than steaks cooked to medium, with rare steaks having SSF values similar (P N 0.05) to both. All treatments used in the current study produced steaks that had low SSF values at each DOD. Even the highest mean SSF of 167.11 N (Standard steaks cooked to well-done) was below the current USDA tenderness threshold of 196.1 N for USDA “Certified Tender” and most were below the 150.0 N required for USDA “Certified Very Tender” (ASTM, 2011).

Response

Most important palatability trait when eating beef Meat product preferred for flavor

Male Female 1 person 2 people 3 people 4 people 5 people 6 people N 6 people Single Married Under 20 20–29 30–39 40–49 50–59 Over 60 African-American Asian Caucasian/White Hispanic Native American Other Under $25,000 $25,000 $34,999 $35,000 $49,999 $50,000 $74,999 $75,000 $100,000 N$100,000 Non-high school graduate High school graduate Some College/Technical School College graduate Post graduate None 1 to 3 times 4 to 6 times 7 or more times Flavor Juiciness Tenderness Beef Chicken Fish Lamb Mutton Pork Shellfish Turkey Veal Venison

63.9 36.1 13.1 28.6 21.4 23.8 8.3 3.6 1.2 27.4 72.6 4.8 28.6 14.3 19.1 22.6 10.7 0.0 1.2 92.8 6.0 0.0 0.0 8.4 10.8

47.6 52.4 13.1 33.3 17.9 25.0 6.0 2.4 2.4 34.9 65.1 6.0 15.5 11.9 21.4 17.9 27.4 0.0 2.4 91.5 4.9 1.2 0.0 15.5 4.8

50.0 50.0 10.7 28.6 16.7 21.4 14.3 6.0 2.4 40.5 59.5 7.1 32.1 8.3 25.0 13.1 14.3 2.4 1.2 73.8 19.1 2.4 1.2 20.5 15.7

8.4

17.9

10.8

20.5

26.2

20.5

18.1

8.3

14.5

33.7 0.0

27.4 4.9

18.1 2.4

9.6

11.0

18.1

20.5

34.2

42.2

51.8 18.1 0.0 48.8 41.7 9.5 50.0 10.7 39.3 66.7 9.5 6.0 2.4 0.0 2.4 4.8 1.2 3.6 3.6

29.3 20.7 0.0 52.4 36.9 10.7 43.4 6.0 50.6 68.7 10.8 2.4 0.0 0.0 8.4 4.8 0.0 1.2 3.6

24.1 13.3 0.0 51.2 36.9 11.9 40.5 10.7 48.8 76.8 15.9 2.4 0.0 0.0 3.7 0.0 0.0 1.2 0.0

a Consumers were screened for degree of doneness preference and only evaluated samples of their preferred degree of doneness.

across all three DOD panels. The demographic profiles of consumers used in all three DOD panels this study were similar to previous beef consumer work in Lubbock, TX (Corbin et al., 2015; Hunt et al., 2014; O'Quinn et al., 2012), a city which has previously been shown to have comparable beef preferences to consumers in multiple U.S. geographic

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regions (Mehaffey et al., 2009; Miller, Carr, Ramsey, Crockett, & Hoover, 2001). When asked to rate a list of motivators important when purchasing fresh beef steaks, consumers in all three DOD panels rated “steak color”, “price”, “size, weight, and thickness”, and “USDA grade” as similar (P N 0.05) in importance and more important (P b 0.05) than all traits other than “familiarity with cut”, “marbling level”, and “eating satisfaction claims (ex. guaranteed tender” (Table 5). Many of the animal production-claims including “animal welfare”, “growth promotant use in the animal”, “antibiotic use in the animal”, and “natural and organic claims” as well as “brand of the product” and “packaging type” ranked among the least important traits to consumers in each DOD panel when purchasing fresh beef steaks. 3.4. Consumer panel evaluation Least squares means for consumer ratings for each DOD panel are presented in Table 6. In non-enhanced samples cooked to medium and well-done, tenderness and juiciness ratings increased (P b 0.05) with increased marbling level (Standard = Select b Low Choice = Top Choice b Prime). In rare samples, however, Top Choice steaks were juicier (P b 0.05) and more tender (P b 0.05) than Low Choice samples, which were similar (P N 0.05) to both Select and Standard for tenderness and juiciness. Within well-done panels, flavor identity and flavor liking, ratings were higher (P b 0.05) for Prime samples than all other nonenhanced treatments. But for medium panels, Prime was only greater (P b 0.05) for flavor identity than Select and Standard steaks and was similar (P N 0.05) to all other non-enhanced treatments in rare panels for the same trait. Similarly, Prime samples were found no different (P N 0.05) than Top Choice and Low Choice samples for flavor liking when cooked to rare and medium. Flavor liking scores were greater (P b 0.05) for Top Choice steaks than Select and Standard steaks in all three DOD panels. Overall liking ratings improved (P b 0.05) with increased marbling level (Prime N Top Choice = Low Choice N Select = Standard) in well-done panels. In medium panels, Prime samples had similar (P N 0.05) overall liking ratings to Top Choice. Additionally, in rare panels, Low Choice samples were similar (P N 0.05) to all other Table 5 Fresh beef steak purchasing motivators1 of consumers (N = 252; 84/degree of doneness) who participated in consumer sensory panels. Trait

Steak color Price Size, weight, and thickness USDA grade Familiarity with cut Marbling level Eating satisfaction claims (ex: guaranteed tender) Nutrient content Country of origin Growth promotant use in the animal Antibiotic use in the animal Animal welfare Packaging type Natural or organic claims Brand of product SEM3 P-value

Degree of doneness panel2 Rare (60 Medium (71 °C) °C)

Well-done (77 °C)

71.4ab 72.7a 73.5a 69.2ab 64.0bc 60.3c 56.8cd

75.9a 73.0a 71.6ab 70.9ab 65.5bc 64.9bcd 63.3cde

77.1a 72.7abc 73.1ab 77.4a 66.7bcd 63.8d 65.3cd

50.9de 46.4ef 45.0ef 41.7fg 36.9g 42.3fg 41.5fg 34.9g 2.9 b0.0001

57.4ef 60.1cdef 57.7def 57.3ef 55.9f 48.0g 45.4gh 39.0h 2.6 b0.0001

61.2de 60.8de 55.4ef 55.6ef 55.7ef 49.9f 50.5f 51.2f 2.7 b0.0001

abcdefgh Least squares means in the same column without a common superscript differ (P b 0.05). 1 Purchasing motivators: 0 = extremely unimportant, 100 = extremely important. 2 Consumers were screened for degree of doneness preference and only evaluated samples of their preferred degree of doneness. 3 SE (largest) of the least squares means.

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Table 6 Least squares means for consumer (N = 252; 84 / degree of doneness) ratings1 of the palatability traits of grilled beef strip loin steaks of varying quality treatments cooked to three degrees of doneness.2 Treatment Rare (60 °C) panels Prime Top Choice3 Low Choice Select Standard Select HE4 Select LE4 SEM5 P-value Medium (71 °C) panels Prime Top Choice3 Low Choice Select Standard Select HE4 Select LE4 SEM5 P-value Well-done (77 °C) panels Prime Top Choice3 Low Choice Select Standard Select HE4 Select LE4 SEM5 P-value

Juiciness

Tenderness

Flavor identity

Flavor liking

Overall liking

78ab 74b 64c 60c 59c 81a 77ab 3 b0.0001

69b 68b 55c 47c 50c 84a 71b 4 b0.0001

66cde 70bc 67cd 61de 61e 78a 74ab 2 b0.0001

63c 64bc 57cd 53d 50d 76a 72ab 3 b0.0001

64bc 64bc 60cd 49d 49d 78a 70ab 3 b0.0001

75a 66b 63b 53c 49c 81a 75a 3 b0.0001

77ab 64c 63c 46d 49d 85a 76b 3 b0.0001

73bc 71c 68cd 61e 63de 81a 78ab 2 b0.0001

68b 64b 63b 53c 53c 79a 75a 3 b0.0001

69bc 64cd 61d 48e 50e 80a 75ab 3 b0.0001

74a 61bc 57c 44d 42d 69a 66ab 3 b0.0001

77a 66b 63b 47c 48c 77a 69ab 3 b0.0001

73a 67b 64b 58c 61bc 77a 74a 2 b0.0001

70a 61bc 58cd 48e 52de 73a 68ab 3 b0.0001

70ab 61cd 58d 44e 47e 75a 67bc 3 b0.0001

abcde Least squares means in the same column within the same degree of doneness without a common superscript differ (P b 0.05). 1 Sensory scores: 0 = extremely dry/tough/unbeef-like, dislike extremely; 100 = extremely juicy/tender/beef-like, like extremely. 2 Consumers were screened for degree of doneness preference and only evaluated samples of their preferred degree of doneness. 3 USDA marbling score of modest00–moderate100. 4 HE = High Enhanced (112% of raw weight), LE = Low Enhanced (107% of raw weight) with a salt, alkaline phosphate and water solution. 5 SE (largest) of the least squares means.

non-enhanced treatments for overall liking, with Top Choice and Prime samples rating higher (P b 0.05) than both Select and Standard. For enhanced treatments, Select HE samples were rated higher (P b 0.05) than all non-enhanced treatments other than Prime for tenderness, juiciness, flavor identity, and flavor liking in all three DOD panels. Moreover, Select HE samples were rated higher (P b 0.05) for overall liking than all treatments other than Select LE in both rare and medium panels and higher than all treatments other than Prime in well-done panels. In medium panels, Select LE steaks were rated higher (P b 0.05) than all non-enhanced treatments other than Prime, for all palatability traits. However, in rare panels, Select LE samples were similar (P N 0.05) to Top Choice samples for all traits. Additionally, in welldone panels Select LE steaks were similar (P b 0.05) to both Prime and Top Choice steaks for juiciness, tenderness, flavor liking and overall liking ratings and similar (P b 0.05) to Low Choice samples for tenderness. The percentage of samples rated as acceptable for each palatability trait by consumers is presented in Table 7. Within each DOD panel, Select and Standard had a similar (P N 0.05) percentage of samples rated acceptable for all palatability traits, which was lower (P b 0.05) than Prime, Top Choice, and both enhanced treatments for juiciness, tenderness, and overall acceptability and lower than Top Choice and both enhanced treatments for flavor acceptability. No difference (P N 0.05) was found in the percentage of samples rated acceptable for flavor among the top three quality grades evaluated (Prime, Top Choice, and Low

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Table 7 Percentage of beef strip steaks of varying quality treatments cooked to three degrees of doneness1 rated as acceptable (yes/no) for juiciness, tenderness, flavor, and overall liking by consumers (N = 252; 84/degree of doneness). Treatment Rare (60 °C) panels Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value Medium (71 °C) panels Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P - value Well-done (77 °C) panels Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value

Juiciness

Tenderness

Flavor

Overall liking

98.8a 94.0ab 86.9bc 81.9c 74.7c 95.2ab 96.4a 4.8 0.0002

93.1ab 90.8b 73.0c 64.6c 68.2c 98.9a 92.0ab 5.4 b0.0001

80.1bc 84.8ab 80.1bc 68.1cd 65.7d 94.2a 89.5ab 5.5 0.0002

85.2ab 87.5ab 79.0bc 62.3d 67.9cd 94.4a 89.9ab 5.8 b0.0001

92.2ab 89.9b 85.3bc 73.4cd 68.6d 97.8a 93.4ab 5.8 b0.0001

97.8a 87.6b 80.5b 61.1c 63.6c 98.9a 96.7a 6.0 b0.0001

88.9bc 87.8bc 82.9cd 71.2de 63.8e 97.8a 93.4ab 6.2 b0.0001

91.7abc 85.8bc 82.2c 63.9d 66.3d 96.5a 94.1ab 5.3 b0.0001

91.9a 77.8bc 69.4c 52.4d 50.0d 88.4ab 82.5abc 5.9 b0.0001

94.3ab 84.9b 84.9b 54.9c 57.3c 98.9a 86.1b 5.9 b0.0001

84.5ab 77.4b 76.2b 54.8c 59.5c 91.7a 86.9ab 5.4 b0.0001

91.8a 78.8b 80.0b 56.0c 50.0c 95.3a 88.3ab 5.7 b0.0001

abcde Least squares means in the same column within the same degree of doneness without a common superscript differ (P b 0.05). 1 Consumers were screened for degree of doneness preference and only evaluated samples of their preferred degree of doneness. 2 USDA marbling score of modest00–moderate100. 3 HE = High Enhanced (112% of raw weight), LE = Low Enhanced (107% of raw weight) with a salt, alkaline phosphate and water solution. 4 SE (largest) of the least squares means.

Choice) in each DOD panel. In the well-done panel, the percentage of samples rated acceptable overall increased with increased quality grade (Prime N Top Choice = Low Choice N Select = Standard). However, in both medium and rare panels, no difference (P N 0.05) was found among Prime, Top Choice, and Low Choice treatments for overall acceptability. In all DOD panels, Select HE had a greater (P b 0.05) percentage of samples rated acceptable than all non-enhanced treatments other than Prime, except for flavor acceptability in rare panels in which it was similar (P N 0.05) to Top Choice. More than 91% of Select HE samples were rated acceptable for all traits in each panel, with the exception of juiciness in well-done panels (88.4%). More than 27% of Select and Standard samples alike in the well-done panels were classified as “unsatisfactory” (Table 8) which was more often (P b 0.05) than all other treatments. Similar results were found for rare panels, in which Select and Standard were rated “unsatisfactory” more than often (P b 0.05) than all treatments other than Low Choice. A higher (P b 0.05) percentage of Select HE samples were rated as “premium quality” than all non-enhanced treatments in both rare and medium panels. In well-done panels, a similar (P N 0.05) percentage of Select HE samples were classified as “premium quality” as Select LE, Prime, and Top Choice. Fewer (P b 0.05) Select and Standard samples were classified as “premium quality” than all other treatments in well-done panels, and all treatments except Low Choice in medium panels. A similar (P N 0.05) percentage of Prime, Top Choice, Select HE, and Select LE samples were classified as “better than everyday quality” in each DOD panel, which was a higher (P b 0.05) percentage than both Select and Standard.

Table 8 Percentage of beef strip steaks of varying quality treatments and degrees of doneness1 rated at different perceived quality levels by consumer panelists (N = 252; 84/degree of doneness). Treatment

Rare (60 °C) panels Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value Medium (71 °C) panels Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value Well-done (77 °C) panels Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value

Unsatisfactory Everyday Better than quality everyday quality

Premium quality

7.7cd 4.4d 14.6bc 24.1ab 27.8a 2.2d 4.4d 5.6 b0.0001

44.1abc 42.9bc 58.3a 54.8ab 53.6ab 25.0d 36.9cd 5.4 0.0008

37.9a 40.4a 21.2b 16.4b 16.4b 36.7a 37.9a 5.6 0.0006

9.5bc 11.9bc 4.8cd 3.6cd 1.2d 35.7a 20.2b 5.2 b0.0001

3.5de 11.8bcd 13.0abc 23.7ab 24.9a 2.4e 4.7cde 4.8 0.0001

32.1bc 40.5bc 42.9b 59.5a 59.5a 16.7d 27.4cd 5.4 b0.0001

40.5a 27.4a 36.9a 14.3b 13.1b 39.3a 36.9a 5.4 0.0002

23.7b 20.1b 7.1c 2.3c 2.3c 41.6a 30.8ab 5.5 b0.0001

5.5bc 8.9bc 10.0b 27.8a 27.8a 2.2c 7.8bc 5.6 0.0001

25.0b 51.2a 54.8a 54.8a 53.6a 25.0b 34.5b 5.5 b0.0001

46.4a 26.2bc 23.8bc 15.5c 15.5c 47.6a 36.9ab 5.4 0.0002

22.6a 13.1ab 10.7b 1.2c 2.4c 25.0a 20.2ab 4.7 0.0009

abcde Least squares means in the same column within the same degree of doneness without a common superscript differ (P b 0.05). 1 Consumers were screened for degree of doneness preference and only evaluated samples of their preferred degree of doneness. 2 USDA marbling score of modest00–moderate100. 3 HE = High Enhanced (112% of raw weight), LE = Low Enhanced (107% of raw weight) with a salt, alkaline phosphate and water solution. 4 SE (largest) of the least squares means.

3.5. Trained sensory panel evaluation A treatment × DOD interaction was found for initial and sustained juiciness (P b 0.05; Table 9). For both initial and sustained juiciness, the effect of marbling level increased with increased DOD. At rare, no difference (P N 0.05) in initial juiciness was found among Top Choice, Low Choice, Select, and Standard samples in addition to no difference (P N 0.05) among Low Choice, Select, and Standard samples for sustained juiciness. However, when cooked to well-done, Prime was initially and sustained juicier (P b 0.05) than all non-enhanced treatments. Also, at well-done, Top Choice and Low Choice samples had higher (P b 0.05) initial juiciness scores than Standard samples. Furthermore, well-done Top Choice steaks were initially juicier (P b 0.05) than Select steaks and had higher sustained juiciness (P b 0.05) than Low Choice, Select, and Standard samples. A similar trend was observed for the two enhanced treatments. At rare, Select HE and Select LE samples were similar (P N 0.05) to Top Choice for both initial and sustained juiciness. But, when cooked to medium or well-done, Select HE and Select LE were rated higher (P b 0.05) for both juiciness traits than all treatments except Prime. Regardless of quality treatment, both initial and sustained juiciness decreased (P b 0.05) with increased DOD (rare N medium N well-done). Prime samples were more tender (P b 0.05) both initially and sustained than all lower grading, non-enhanced samples (Table 10).

L.W. Lucherk et al. / Meat Science 122 (2016) 145–154 Table 9 Least squares means for the interaction (initial juiciness: P = 0.0018; sustained juiciness: P = 0.0273) of degree of doneness and quality treatment for trained sensory panel ratings1 of grilled beef strip loin steaks. Degree of doneness/quality treatment Rare (60 °C) Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value Medium (71 °C) Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value Well-done (77 °C) Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value

Initial juiciness

Sustained juiciness

74ab 69abc 62c 62c 67bc 75a 74ab 3 0.0010

70a 64ab 55c 54c 59bc 72a 70a 4 b0.0001

64a 50b 45bc 38c 38c 67a 63a 3 b0.0001

61a 43b 37bc 30c 30c 61a 56a 4 b0.0001

54a 43b 35bc 31cd 23d 56a 53a 3 b0.0001

49a 37b 28c 25cd 19d 51a 47a 4 b0.0001

151

Additionally, Top Choice and Low Choice samples were similar (P N 0.05) for initial and sustained tenderness, but were both more tender (P b 0.05) initially and sustained than Select and Standard samples. Moreover, Prime and Top Choice samples were rated higher (P b 0.05) than Low Choice, Select, and Standard for beef flavor intensity. Select HE samples were the most tender (P b 0.05) initially and sustained compared to all treatments. Select LE steaks were similar (P N 0.05) to Prime for initial and sustained tenderness, but were higher (P b 0.05) than all other non-enhanced treatments for the same traits. Select HE samples were rated lower (P b 0.05) than all non-enhanced treatments for beef flavor intensity. Differences in DOD had only minimal effects on trained sensory panel ratings presented in Table 10. Rare samples were found to be more tender (P b 0.05) initially and sustained than steaks cooked to medium and well-done, with no tenderness differences (P N 0.05) observed between the two higher DOD. Additionally, no differences (P N 0.05) were found among DOD for beef flavor intensity. 3.6. Relationships among sensory traits

abcd Least squares means in the same section without a common superscript differ (P b 0.05). 1 Sensory scores: 0 = extremely dry, 100 = extremely juicy. 2 USDA marbling score of modest00–moderate100. 3 HE = High Enhanced (112% of raw weight), LE = Low Enhanced (107% of raw weight) with a salt, alkaline phosphate and water solution. 4 SE (largest) of the least squares means.

Correlation coefficients used to identify and quantify relationships among sensory traits are presented in Table 11. Consumer overall like rating was highly correlated (P b 0.01) with the consumer evaluated traits of flavor liking (r = 0.95), flavor ID (r = 0.90), tenderness (r = 0.89) and juiciness (r = 0.81). Additionally, consumer overall like was correlated (P b 0.01) with trained panel sustained tenderness (r = 0.65), initial tenderness (r = 0.64), sustained juiciness (r = 0.43), and initial juiciness (r = 0.42). Moreover, consumer evaluations of specific palatability traits were similar to trained panel evaluations of the same traits. Consumer tenderness rating was correlated (P b 0.01) with trained panel initial tenderness (r = 0.69) and trained panel sustained tenderness (r = 0.70). Furthermore, consumer juiciness rating was associated (P b 0.01) with trained panel initial juiciness (r = 0.62) and trained panel sustained juiciness (r = 0.63). However, trained panel beef flavor intensity was not related (P N 0.05) to consumer overall like or flavor liking scores. 4. Discussion

Table 10 Least squares means for trained sensory panel ratings1 of the palatability traits of grilled beef strip loin steaks of varying quality treatments and degrees of doneness. Treatment Quality treatment Prime Top Choice2 Low Choice Select Standard Select HE3 Select LE3 SEM4 P-value Degree of doneness Rare (60 °C) Medium (71 °C) Well-done (77 °C) SEM4 P-value QT × DOD P-value abcde

Initial tenderness

Sustained tenderness

Beef flavor intensity

68b 55c 53c 42d 41d 76a 67b 2 b0.0001

62b 47c 45c 33d 32d 72a 61b 2 b0.0001

62a 58b 53cd 54c 52cd 48e 51de 1 b0.0001

63a 56b 53b 2 0.0002

56a 49b 46b 2 0.0005

56 53 53 1 0.1628

0.1260

0.1219

0.9174

Least squares means in the same section of the same column without a common superscript differ (P b 0.05). 1 Sensory scores: 0 = extremely tough/bland; 100 = extremely tender/intense. 2 USDA marbling score of modest00–moderate100. 3 HE = High Enhanced (112% of raw weight), LE = Low Enhanced (107% of raw weight) with a salt, alkaline phosphate and water solution. 4 SE (largest) of the least squares means.

4.1. Consumer purchasing motivators Results for consumer purchasing motivators in the current study are similar to those of Reicks et al. (2011) and O'Quinn (2012), who found that consumers rank factors related to taste as the most important motivators for purchasing fresh beef steaks. In agreement with our results, previous research also reported nutritional content was of moderate importance and that various animal production traits, including natural and organic claims, were least important to consumers when making beef purchase decisions (Reicks et al., 2011; O'Quinn, 2012). In the present study, visual characteristics of the fresh product and price ranked among the top four factors considered when purchasing beef in all DOD panels, which is in agreement with Robbins et al. (2003) where consumers ranked “cut”, “color”, “amount of visible fat”, “price”, and “amount of liquid in the package” as the most important considerations when purchasing beef. It is notable that in the current study and O'Quinn (2012), consumers rated beef quality attributes (color, marbling level, eating satisfaction claims, and visual appearance) as more important purchasing motivators than nutrient content, product brand, and animal production claims. These results underscore the premium placed on eating quality and visual appearance by beef consumers. Additionally, these results indicate that consumer purchasing decisions are more directly driven by inherent properties of the meat in the retail package as opposed to claims and information that would be provided on labels or at the point of sale.

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Table 11 Pearson correlation coefficients for sensory scores of beef strip steaks varying in quality treatment and degree of doneness. Measurement

Consumer Panel rating Juiciness Flavor ID Flavor Liking Overall like Trained panel rating Initial tenderness Sustained tenderness Initial juiciness Sustained juiciness Beef flavor intensity

Consumer panel rating

Trained panel rating

Tenderness

Juiciness

Flavor ID

Flavor liking

0.80⁎⁎ 0.77⁎⁎ 0.82⁎⁎ 0.89⁎⁎

0.70⁎⁎ 0.72⁎⁎ 0.81⁎⁎

0.92⁎⁎ 0.90⁎⁎

0.95⁎⁎

0.69⁎⁎ 0.70⁎⁎ 0.44⁎⁎ 0.46⁎⁎ 0.02

0.66⁎⁎ 0.66⁎⁎ 0.62⁎⁎ 0.63⁎⁎ 0.15⁎

0.53⁎⁎ 0.54⁎⁎ 0.33⁎⁎ 0.34⁎⁎ −0.03

0.56⁎⁎ 0.58⁎⁎ 0.35⁎⁎ 0.36⁎⁎ −0.03

Overall like

Initial tenderness

Sustained tenderness

Initial juiciness

Sustained juiciness

0.64⁎⁎ 0.65⁎⁎ 0.42⁎⁎ 0.43⁎⁎ −0.01

0.98⁎⁎ 0.76⁎⁎ 0.77⁎⁎ −0.03

0.73⁎⁎ 0.76⁎⁎ −0.02

0.98⁎⁎ 0.13⁎

0.13⁎

⁎⁎ Correlation coefficient differs from 0 (P b 0.01). ⁎ Correlation coefficient differs from 0 (P b 0.05).

4.2. Quality treatment and degree of doneness The “insurance theory” of marbling states that increased marbling level counteracts the negative palatability-effects of increased DOD (Savell & Cross, 1988; Smith & Carpenter, 1974). However, to date, literature evaluating this theory has produced mixed results. A study by Wheeler, Shackelford, and Koohmaraie (1999b) tested this theory using “tender” (Warner–Bratzler shear force values of b49 N at 3-d of aging) Top Choice and USDA Low Select longissimus thoracis steaks cooked to well-done. These authors found that trained panelists rated Top Choice steaks higher for tenderness, juiciness, and flavor intensity than Low Select steaks, supporting the “insurance theory”, though differences were very small, leaving the authors to speculate as to whether these differences would be detectable by consumers (Wheeler et al., 1999b). Moreover, it has been reported that DOD plays the largest role in consumer perception of beef palatability (Cox et al., 1997). Nevertheless, most previous work evaluating the effects of marbling on palatability has included only a single DOD. Multiple studies have demonstrated increased beef palatability with increased marbling when steaks were cooked to medium (Corbin et al., 2015; Guelker et al., 2013; O'Quinn et al., 2012). However, in the current study, the effect of marbling level was assessed across multiple DOD to determine if marblingrelated palatability effects were DOD dependent and test the strength of the “insurance theory”. Our results indicate the “insurance theory” of marbling is dependent on the trait evaluated and the technique (consumer panel, trained sensory or SSF) used. For example, our consumer panel results indicated only minor differences in the relationships among steaks from different quality grades within each DOD panel. In general, within the nonenhanced samples, tenderness, juiciness, flavor, and overall liking scores tended to increase with increased marbling level. Consumer ratings for these traits decreased as DOD increased, but the relationship among samples of varying quality grades remained relatively constant. Based on the “insurance theory”, we would have expected the effects of increased DOD more severe in lower marbled (USDA Standard and Select) samples. However, our results do not indicate lower marbled steaks rate differently for juiciness, tenderness, flavor, or overall liking across DOD, compared to higher marbled samples when consumers sample beef at their preferred DOD. Our results revealed no interaction of DOD and quality treatment for all trained panel tenderness and flavor ratings, indicating an independence of marbling level and DOD for these traits. However, the effect of marbling on trained panel juiciness scores was dependent upon DOD. As DOD increased from rare to well-done, the role marbling played in juiciness perception greatly increased. When cooked to rare, the mean difference between the two most extreme samples (Prime and Select) was less than 19% for initial juiciness and 30% for sustained

juiciness. But, when cooked to well-done, the mean difference between the two most extreme samples (Prime and Standard) increased to more than 133% for initial and 161% for sustained juiciness. This indicates the importance of not only fat (marbling) in juiciness perception, but also the importance of moisture. Juiciness decreased for both trained and consumer panel measures of juiciness as DOD increased as a result of moisture loss through the cooking process. The effect of marbling on SSF values was also dependent on DOD. Previous research has shown an increase in shear force value and decrease in sensory panel tenderness and juiciness scores with increased DOD (Cross et al., 1976; Lorenzen, Davuluri, Adhikari, & Grün, 2005; Luchak et al., 1998; Wheeler, Shackelford, & Koohmaraie, 1999a). However, many of these reports used only a single or limited number of quality grades and most commonly used Warner-Bratzler shear force testing as opposed to the SSF used in the current study. Present results support the “insurance theory” for the effect of marbling for SSF; however, neither trained nor consumer sensory panel measures of tenderness produced similar results. Results of the current study provide only limited support for the “insurance theory” of marbling effects on beef palatability. Only the effects of marbling on SSF and trained sensory panel juiciness scores were dependent on DOD. Effects for all other trained panel sensory ratings were found to be independent. This demonstrates the improvement in beef palatability observed with increased marbling level and USDA quality grade is consistent across DOD, providing no evidence for increased significance of higher marbled steaks to consumers who prefer well-done. 4.3. Enhancement Enhancement of USDA Select strip loins in the current study resulted in very large improvements in all beef palatability traits. Select HE samples were rated 35%, 53% and 57% higher for juiciness, 79%, 85%, and 64% higher for tenderness, 43%, 49%, and 52% higher for flavor liking, and 59%, 67%, and 70% higher for overall liking than non-enhanced Select samples by consumers in the rare, medium, and well-done panels, respectively. Likewise, Select LE samples resulted in increases of 28%, 42%, and 50% for juiciness, 51%, 65%, and 47% for tenderness, 36%, 42%, and 42% for flavor liking, and 43%, 56%, and 52% for overall liking compared to non-enhanced Select for the rare, medium, and well-done panels, respectively. Additionally, non-enhanced Select samples were rated unacceptable for overall liking in approximately 38% of rare, 36% of medium, and 44% of well-done samples. This percentage was reduced to less than 6% for Select HE and less than 12% for Select LE steaks in each DOD panel. The use of enhancement increased the percentage of Select steaks rated acceptable overall by 32–39% (Select HE) and 27–32% (Select LE), with both treatments rated acceptable in more than 88% of samples in each DOD panel.

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This improvement in beef palatability through enhancement has been demonstrated by multiple authors by both consumer panelists (Brooks et al., 2010; Robbins et al., 2003) and trained panelists (Grobbel, Dikeman, Hunt, & Milliken, 2008; Vote et al., 2000; Wicklund et al., 2005). However, most previous work has used only a single quality grade for comparison. In the current study, Select HE steaks were rated higher for tenderness, juiciness, flavor and overall liking than all other quality grades, by consumers and trained panelists, with many traits being found similar to Prime. Additionally, Select LE samples were rated similar or superior to Prime and Top Choice samples for all traits evaluated and higher than all other non-enhanced treatments for most traits. Similar to marbling, the effect of enhancement was independent of DOD for all palatability traits except juiciness, with the advantage of enhanced product over non-enhanced products increasing as DOD was increased. However, it is noteworthy that non-enhanced samples in the current study received no added salt, whereas the two enhanced treatments were formulated to contain 0.3% NaCl. Salt is a well-known flavor enhancer and is commonly added to beef steaks by consumers prior to cooking. It is unclear how the added salt of the enhanced treatments, even at this low level, may have influenced consumer perception of samples in the current study. Consistent with our study, previous work evaluating beef enhancement has included only non-salted beef for comparison (Brooks et al., 2010; Robbins et al., 2003; Vote et al., 2000; Wicklund et al., 2005). Additional work evaluating salt and phosphate enhancement of beef comparing enhanced samples to nonenhanced samples with salt added prior to cooking is needed to determine the role salt plays in the increased sensory panel traits typically observed with enhancement. The USDA quality grading system was established to segregate beef into categories of expected eating experience. The palatability advantage of higher quality grading beef is well known (Emerson et al., 2013; O'Quinn et al., 2012; Smith et al., 1987). Currently, Prime strip loins are marketed at a 94% premium price over Select (USDA, 2015a, 2015b). Data from our study indicates retail and foodservice establishments may purchase and enhance lower grading Select product and produce a similar or superior eating experience to USDA Prime. These results indicate a large opportunity for value creation for the beef industry for USDA Select product that will help meet current consumer demands for beef eating quality.

Acknowledgements This project was funded by the Beef Checkoff. The funding agency had no involvement in study design, collection, analysis, or interpretation of data nor in the writing of the report. Additionally, this report is contribution number 16-064-J from the Kansas Agricultural Experiment Station.

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