Characterization and classification of Japanese consumer perceptions for beef tenderness using descriptive texture characteristics assessed by a trained sensory panel

Meat Science 96 (2014) 994–1002

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Characterization and classification of Japanese consumer perceptions for beef tenderness using descriptive texture characteristics assessed by a trained sensory panel Keisuke Sasaki a,⁎, Michiyo Motoyama a, Takumi Narita a, Tatsuro Hagi a, Koichi Ojima a, Mika Oe a, Ikuyo Nakajima a, Katsuhiro Kitsunai a, Yosuke Saito b, Hikari Hatori c, Susumu Muroya a, Masaru Nomura a, Yuji Miyaguchi c, Koichi Chikuni a a b c

National Institute of Livestock and Grassland Science, National Agriculture and Food Research Organization (NARO), 2 Ikenodai, Tsukuba, Ibaraki 305-0901, Japan Miyagi Prefectural Animal Experimental Station, 1 Hiwata, Minamizawa, Iwadeyama, Osaki, Miyagi 989-6445, Japan School of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Ibaraki 300-0393, Japan

a r t i c l e

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Article history: Received 13 September 2013 Received in revised form 18 October 2013 Accepted 18 October 2013 Keywords: Beef Tenderness Trained panel Consumer perception Japanese

a b s t r a c t Meat tenderness is an important characteristic in terms of consumer preference and satisfaction. However, each consumer may have his/her own criteria to judge meat tenderness, because consumers are neither selected nor trained like an expert sensory panel. This study aimed to characterize consumer tenderness using descriptive texture profiles such as chewiness and hardness assessed by a trained panel. Longissimus muscles cooked at four different end-point temperatures were subjected to a trained sensory panel (n = 18) and consumer (n = 107) tenderness tests. Multiple regression analysis showed that consumer tenderness was characterized as ‘lowchewiness and low hardness texture.’ Subsequently, consumers were divided into two groups by cluster analysis according to tenderness perceptions in each participant, and the two groups were characterized as ‘tenderness is mainly low-chewiness’ and ‘tenderness is mainly low-hardness’ for tenderness perception, respectively. These results demonstrate objective characteristics and variability of consumer meat tenderness, and provide new information regarding the evaluation and management of meat tenderness for meat manufacturers. © 2013 Elsevier Ltd. All rights reserved.

1. Introduction Texture is an important sensory characteristic for the preference of muscle foods, such as beef, pork, and chicken, rather than flavor when off-flavors are not present. In particular, tenderness is the most important texture attribute along with juiciness to assure consumer preference for meat (Riasvik, 1994). In consumer studies in the United States, improvement of tenderness ratings increased consumer acceptance (Huffman et al., 1996) and overall acceptance of beef (Miller, Carr, Ramsey, Crockett, & Hoover, 2001). It has also been reported that consumers were willing to pay a premium for improved ‘tenderness’ of beef (Boleman et al., 1997). Our previous questionnaire studies on Japanese consumers indicated that there is a segment of consumers which requires tenderness in beef (Sasaki & Mitsumoto, 2004) and that most Japanese consumers intend to purchase beef guaranteed to be ‘tender’ (Sasaki, Mitsumoto, & Aizaki, 2006). Furthermore, the contribution of tenderness to the overall acceptance of beef among Japanese consumers has been estimated at approximately 25%, as assessed by a

⁎ Corresponding author at: 2 Ikenodai, Tsukuba, Ibaraki 305-0901, Japan. Tel.: +81 29 838 8690; fax: +81 29 838 8606. E-mail address: [email protected] (K. Sasaki). 0309-1740/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2013.10.021

consumer sensory survey (Polkinghorne, Nishimura, Neath, & Watson, 2011). Therefore, the measurement and improvement of beef tenderness has been a critical issue for satisfaction of consumer palatability in meat producers and industries from a profit standpoint. On the other hand, there have been various studies to clarify how objective sensory characteristics contribute to consumer preference and satisfaction to develop new products by food manufacturers. In these studies over the past decade, consumers only judge their hedonic ratings, whereas an expert sensory panel provides descriptive sensory characteristics of products (Faye et al., 2006). Strategies in these previous studies were based on the fact that researchers cannot ask consumers their opinion regarding complex sensory attributes because of the limited vocabulary to express sensory perception in untrained consumers (Muñoz, 1998). In contrast, food industries would like to know how consumers perceive sensory characteristics of products (Faye et al., 2006). It was also pointed out that sensory attributes assessed by trained panelists may be irrelevant for consumers (Ares, Deliza, Barriero, Gimenez, & Gambaro, 2010). From that viewpoint, there have been several trials to characterize consumer sensory perception of food as related to descriptive sensory profiles assessed by an expert panel, for example using vegetables (Fillion & Kilcast, 2002), fish meat (Cardello et al., 1982), commercial food samples (Carr, Craig-Petsinger, & Hadlich, 2001), and meat products (Muñoz & Chambers, 1993).

K. Sasaki et al. / Meat Science 96 (2014) 994–1002

Meat scientists are particularly interested in the perceptions of meat tenderness because of its importance for consumer meat satisfaction. There are several studies regarding consumer tenderness perception. For example, previous reports indicated that lower instrumental shear force values in meat were highly related to consumer tenderness and satisfaction (Destefanis, Brugiapaglia, Barge, & Dal Molin, 2008; Miller et al., 2001; Rodas-González, Huerta-Leidenz, Jerez-Timaure, & Miller, 2009). Robbins et al. (2003) indicated consumer attitudes involving tenderness towards enhanced beef to understand what characteristics the consumer desires in beef quality. In these studies, however, consumers were asked about tenderness without any objective definitions or training. According to Destefanis et al. (2008), tenderness is a highly variable characteristic, and this wide variability is a limiting factor when attempting to meet consumer beef requirements. Hence, consumer tenderness regarding meat should be characterized subjectively for managing meat texture. In addressing such problems, we previously characterized beef texture using ISO5492 texture vocabularies (Sasaki et al., 2010), and presented how ‘chewiness’ and ‘hardness’ defined in ISO5492 were perceived separately by a trained sensory panel and changed differently while cooking three portions of beef muscles at increasing end-point temperatures. Our previous study also presented how intramuscular fat, which has been generally considered to cause tenderness, improves both ‘chewiness’ and ‘hardness’ as defined in ISO5492 in longissimus muscles of Japanese Black crossbreed beef cattle (Sasaki, Motoyama, & Narita, 2012). Moreover, we indicated that ‘chewiness’ and ‘hardness’ ratings expressed in ISO11036:1994 were useful for quantitative texture characterization of meat in basic study (Sasaki, Motoyama, Narita, & Chikuni, 2013). However, we still do not know what meaning consumers attach to tenderness. The goal of our study was to characterize “untrained consumer's tenderness” using objective texture words. For this purpose, the present study demonstrated comparisons of consumer perceptions of tenderness evaluated by a Japanese consumer panel with ‘chewiness’ and ‘hardness’ ratings assessed by a trained sensory panel in beef longissimus muscles cooked at four different end-point temperatures.

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92 °C, respectively. The internal temperature of samples and oven temperature were monitored by a data logger, Soft-Thermo E830 (TechnolSeven, Co., Tokyo), equipped with T- and K-type thermocouples, respectively. The internal temperature reached the end point within 10.0 min in each condition, and the temperature was kept for 1 min. To remove any remaining heat, samples were placed in PVC bags, and chilled in ice-cold water immediately after heat treatment, and kept for 10min. These sample pieces were kept in a refrigerator set at 4°C before they were subjected to sensory analysis. Immediately before sensory sessions, samples were re-heated with a steam mode of SSC-5DCNU oven set at 85 °C for 1 min in order to maintain hygiene and to obtain uniform surface color of samples. Afterwards the samples were subjected to sensory evaluation and instrumental texture determination at room temperature. The pH of samples assessed before cooking treatments were 5.57 ± 0.02 (means ± standard deviation) by a pH meter (Type F-12, Horiba, Ltd., Kyoto, Japan) equipped with a glass-electrode. 2.3. Trained sensory panel Research scientists of the animal products division of the National Institute of Livestock and Grassland Science (NILGS) were recruited as the sensory panel in our previous studies (Sasaki et al., 2010, 2012, 2013). Therefore these panelists were highly experienced for meat texture evaluation. Panelists were lectured about the evaluation scales of ‘hardness’ and ‘chewiness’ defined in ISO11036:1994, and were trained using the example foods indicated in the scales as presented in Table 1. The numbers of panelists were 18 (10 males and 8 females). Immediately before the sensory testing sessions, each panelist was informed of the safety of the beef samples and then consented to participate in the experiments as a sensory panelist according to the Japanese guidelines for sensory evaluation of meat (National Livestock Breeding Center, 2005). 2.4. Trained sensory evaluation

2. Materials and methods 2.1. Samples Ribloin and Sirloin cuts, defined in Japanese standards for use in transactions of cut meat (Japan Meat Grading Association, 2005), from three Holstein steers fed at Nasu-Karasuyama City, Tochigi Prefecture, Japan, were obtained from Takizawa Ham Co., Ltd. (Tochigi City, Tochigi Prefecture, Japan). Animals were slaughtered at 15months old and muscles were harvested 5 days after slaughter. Muscle samples were vacuum-packed and stored at −30 °C before sensory experiments. Cut meats were thawed in a refrigerator set at 4 °C before the sensory test. After thawing, longissimus muscles were isolated from cut meats and subjected to cooking treatment. Thus, M. longissimus thoracis et lumborum from rib 7 to lumbar vertebra 5 was obtained through experiments. 2.2. Sample treatment Samples were formed into 2×2× 2cm cubes as described previously (Sasaki et al., 2010, 2012), and subjected to heat treatment. Four endpoint cooking temperatures were used in order to obtain different textures of meat samples. We established the end-point temperatures of 50, 60, 72 and 92 °C, which correspond to ‘blue’, ‘rare’, ‘medium’, and ‘well-done’ steaks, respectively. These cooking conditions provide different sensory texture characteristics as described previously (Sasaki et al., 2010). Heat treatment was carried out as in our previous study (Sasaki et al., 2010) using a steam convection oven SSC-5DCNU (Maruzen, Co., Ltd., Tokyo) for uniform heat treatment, and kept at 50–53, 60–63, 72–75 and 92–95 °C for the end-point 50, 60, 72 and

A sensory test was performed in the sensory test room of NILGS using an individual booth illuminated by red lighting. Test room temperature was maintained by air-conditioner set at 22 °C, the sensory trials were carried out at 3–4 p.m. and the time of each trial was approximately 20 min. Evaluation scales of ‘hardness’ (1=soft to 7=hard) and ‘chewiness’ (1=low-intensity chewiness to 9=high-intensity chewiness) presented in ISO11036:1994 were used for evaluation the same as in our previous study (Sasaki et al., 2013). For sensory test, two samples each were presented to each panelist at each end-point temperature. Thus, each panelist received a total of eight samples in each trial session. A Latin square design was used to avoid effects of serving order. Panelists tested each sample and evaluated ‘hardness’ and ‘chewiness’ as described above. Evaluation guidelines including definition and examples of each evaluation scale and reference product were also presented to panelists in each sensory test session. The sensory trial was conducted three times with muscles from different carcasses used in each trial.

Table 1 Age and gender characteristics of consumer panel. Age

20–29 30–39 40–49 50–59 60–

Gender Female

Male

12 11 10 10 10

11 12 10 11 10

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2.5. Instrumental texture measurements Warner–Bratzler shear force value (WBSFV) measurement and Texture Profile Analysis (TPA) were performed in cooked samples subjected to the sensory test as described previously (Sasaki et al., 2013). For WBSFV measurements, cores 1.27 cm (half inch) in diameter were prepared from cooked muscle cubes and sheared perpendicularly to the muscle fiber orientation using a Warner–Bratzler V-blade attached to an Instron Universal Testing Machine (Model 5542; Instron Corp., Canton, MA, USA) fitted with a 500N compression load cell with a crosshead speed of 250 mm/min. The peak force values that were measures of the shearing through the centers of the cores were used to determine WBSFV of the samples. TPA measurements were conducted as described previously (Caine, Aalhus, Best, Dugan, & Jeremiah, 2003). For TPA, cylindrical samples with 1.27 cm in diameter and 1.0 cm in height were prepared from cooked muscle cubes. The samples were compressed parallel to the muscle fiber orientation using 4.0cm diameter disc type probe attached to an Instron 5542 testing machine as described above. Each sample underwent two cycles of 80% compression using Texture Profile Analysis Test Method Templates (version 3.0; Instron Corp., Canton, MA, USA) for Instron Testing Machine, and then TPA ‘hardness,’ ‘springiness,’ and ‘gumminess’ were calculated. Both WBSFV and TPA measurements were done at room temperature. For each machinery measurement, 10 replications were done for each cooking temperature of each muscle for each carcass. 2.6. Consumer panel recruiting Consumer panelists were recruited around Tsukuba City, Ibaraki Prefecture, Japan. Recruiting was performed by Do House Inc. (Tokyo, Japan). The number of applicants, 169, was limited to those who eat beef at least once a week. One-hundred and seven consumers were chosen as consumer panelists from among the 169 applicants to make for the same numbers of each gender and each age group as presented in Table 1. 2.7. Consumer panel test and questionnaire The consumer panel test was carried out in the sensory test room of NILGS using desks equipped with partitions. The test room was illuminated by red lighting and maintained at room temperature by an airconditioner set at 22 °C. Sensory trials were carried out for 2 days at 10:30a.m., 1:30p.m. and 3:30p.m. and the time of each trial was approximately 1 h. Panelists evaluated beef samples cooked at four cooking end-point temperatures prepared as described above (Section 2.2.). For the sensory test, two sample pieces each were presented to each panelist at each end-point temperature. Thus, each panelist received a total of eight sample pieces in each trial session. A Latin square design was used to avoid effects of serving order the same as for trained panel sessions. Panelists tested and graded tenderness and texture preference of each sample using 7-point scales from −3 = not tender to 3 = tender for tenderness and from −3 = greatly liked to 3 = greatly disliked for texture preference according to their own criteria. Oral rinsing using bottled purified water (Yasashii-Akachan-No-Mizu, Morinaga Milk Industry Co., Ltd., Tokyo, Japan) was done at each interval (at least 1 min between each sample testing). Following the sensory test, a questionnaire regarding demographic characteristics of panelists, preferences for several beef dishes, and requirements for beef characteristics were conducted. Preferences for several beef dishes as presented in Table 2 were evaluated on a scale from −3 = greatly disliked to +3 = greatly liked. Requirements for beef characteristics as presented in Table 3 were also ascertained on a scale from −3 = completely unrequired to +3 = absolutely required.

Table 2 Questions regarding preferences for each beef dish. Beef dishes Beef steak Yakiniku (Japanese/Korean-style barbecue) Sukiyaki (cooking of sliced beef in stocks with soy source and sugar) Shabu-shabu (swirled beef in hot water) Beef stew Gyu-don (a bowl of rice topped with beef) Hamburg steak Roasted beef Consumer panelists were asked regarding their preferences for each beef dish presented in this table using 7-point scale (−3 = greatly disliked; +3 = greatly liked) following the sensory test.

2.8. Statistical analysis All statistical analysis was performed using the SAS system (version 9.12, SAS Institute, Cary, NC, United States). 2.8.1. Trained sensory analysis Ratings for ‘chewiness’ and ‘hardness’ were analyzed by MIXED procedure of the SAS system. Cooking end-point temperature, serving order and testing session were used as fixed effect, and panelists were used for the random effect. Multiple comparisons in sensory ratings between cooking end-point temperatures were analyzed by Tukey– Kramer test of the MIXED procedure. Values were expressed as least square means ± standard error means (SEM). 2.8.2. Instrumental measurements Instrumental texture measurements such as WBSFV and TPA indices were analyzed using MIXED procedure of the SAS system; cooking endpoint temperature was used as the fixed effect and individual carcass was used as the random effect. Multiple comparisons between cooking end-point temperatures were conducted using Tukey test. 2.8.3. Consumer sensory analysis and questionnaire First, tenderness ratings of all participants were analyzed by MIXED procedure of the SAS system. Cooking end-point temperature, day of experiment, and testing order were used for the fixed effect, and panelists were used for the random effect. Subsequently, panelists were classified into two segments according to tenderness ratings for four samples in individuals by Ward method cluster analysis using the cluster (CLU) procedure of the SAS system. The effects of consumer segment and cooking end-point temperature on tenderness and texture preference ratings were also analyzed using the MIXED procedure. Cooking end-point temperature, segment of

Table 3 Questions regarding requirements for each beef characteristic. Beef characteristics

In Japanese

Exclusive-feeling Building up my stamina Nutrient/nourishment Feeling of fullness Heaviness Feeling of chewing with tasting well Chewiness Tastefulness Smoothness Lightness Feeling of melting Sense of fulfilment Happiness

Koukyu-kan Sutamina Eiyou/jiyou Manpuku-kan Kotteri-kan Kamishimeru-kanji Hagotae Jimi-afureru Kime-komayakasa Assari-kan Torokeru-kanji Jujitsu-kan Kofuku-kan

Consumer panelists were asked regarding their requirements for each beef characteristic presented in this table using 7-point scale (−3 = completely unrequired; +3 = absolutely required).

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participants, and serving order were designated as the fixed effect, and panelists were used as the random effect. Multiple comparisons were conducted using Tukey–Kramer test of the MIXED procedure. To characterize tenderness perception in each consumer group, multiple regression analysis using the REG procedure of the SAS system was conducted using consumer tenderness ratings as dependent and trained sensory ‘chewiness’ and ‘hardness’ ratings as regressors. Comparisons of questionnaire data between consumer groups were conducted by Welch's t-test using the analysis of variance (ANOVA) procedure of the SAS system. Differences in demographic characteristics such as age group and gender between consumer groups were analyzed by chi-square analysis using the TABLE procedure of the SAS system.

(N)

3. Results

100

30

First, we assessed how tenderness of meat was defined by a trained panel using two factors, ‘chewiness’ and ‘hardness’, as our previous studies showed that tenderness mainly consists of ‘chewiness’ and ‘hardness’ (Sasaki et al., 2010). To address this, cooked meat specimens at four different cooking temperatures were evaluated by the trained panel using ‘chewiness’ and ‘hardness’ which were proposed in ISO11036:1994. We showed that ‘chewiness’ ratings were the highest at 50 °C of the cooking end-point temperature, and significantly decreased between 50 and 60 °C (P b .05) (Fig. 1(A)). ‘Hardness’ ratings were significantly increased between 60 and 72 °C of the cooking endpoint temperature (P b .05) (Fig. 1(B)). Fig. 2 presents changes in WBSFV and TPA indices by increasing the cooking end-point temperature of beef samples. These instrumental texture parameters changed independently of each other during heating. As shown in Fig. 2(A), WBSFV was the lowest at 60 °C and increased to 92 °C. Hardness (Fig. 2(A)), gumminess (Fig. 2 (B)), and springiness (Fig. 2 (C)) by TPA increased along with cooking endpoint temperature increase.

7 6

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Fig. 2. Instrumental texture measurements in beef longissimus muscles cooked at four different end-point temperatures. (A) Warner–Bratzler shear force, (B) hardness of Texture Profile Analysis (TPA), (C) Springiness of TPA, and (D) Gumminess of TPA. Values with different superscripts mean differ significantly (P b .05) within each texture index.

b

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Cooking end-point temperature (oC)

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Cooking end-point temperature (oC) Fig. 1. ‘Chewiness’ and ‘hardness’ ratings in beef longissimus muscles cooked at four different end-point temperatures assessed by a trained sensory panel using ISO11036:1994 examples. Values with different superscripts mean differ significantly (P b .05) within each sensory attribute.

Correlations between trained sensory texture ratings and instrumental measurements were also analyzed. Sensory ‘chewiness’ ratings were not significantly correlated to WBSFV (r = .460, P = .13) nor TPA texture indices (P N .05), whereas sensory ‘hardness’ ratings correlated to WBSFV (r = .753, P b .01), TPA hardness (r = .842, P b .001), springiness (r = .836, P b .001), and gumminess (r = .869, P b .001). Cooking temperature is reportedly the important factor for texture characteristics of meat, and cooking time does not affect it (Combes, Lepetit, Darche, & Lebas, 2003). We found that trained panel ‘chewiness’ and ‘hardness’ changed independently between 50 and 60°C of cooking

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temperature. Heat denaturation of protein is the main contributor on texture formation of meat. In particular, both denaturation of connective tissues and muscle fiber proteins correspond to texture changes below and above 60 °C, respectively (Christensen, Purslow, & Larsen, 2000). Different changes between ‘chewiness’ and ‘hardness’ presented in this study are probably due to the differences in heat denaturation properties among meat proteins. Further work should be conducted on how each protein denaturation results in sensory texture descriptors while cooking meat.

3.2. Overall consumer panel ratings Following trained sensory and instrumental texture characteristics, we measured consumer panel tenderness and texture likings for meat samples cooked at four different end-point temperatures. Fig. 3 shows tenderness ratings assessed by the consumer panel test. Fig. 3(A) indicated least squares means of tenderness ratings of all participants.

Consumer tenderness increased significantly between 50 and 60 °C of the cooking end-point temperature (P b .05). In contrast, consumer tenderness decreased significantly above 60 °C (P b .05). We also found that texture liking increased between 50 and 60 °C of end-point temperature, then decreased along to the end-point temperature above 60 °C similar to consumer tenderness in all participants (Fig. 4(A)). Previous studies have indicated that customer ratings of tenderness are the highest for steaks cooked to lower degrees of doneness such as medium–rare, approximately 60–65 °C, or less (Lorenzen et al., 1999). Consumer tenderness above 60 °C in the present study was in good agreement with the above-mentioned study (Lorenzen et al., 1999). In contrast, changes in texture measurements and consumer ratings between 50 and 60 °C, such as trained panel ‘chewiness’ decreasing and consumer tenderness increasing, were the interesting findings of our study. Texture formation and consumer ratings below 60 °C, and rare

3 3

A) All panelists (N=107)

2

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-1

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B) Group 1 (N=56)

2

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1

y 0

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C) Group 2 (N=51)

2

Consumer texture liking ratings

Consumer 'Tenderness' ratings

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B) Group 1 (N=56)

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C) Group 2 (N=51)

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Cooking end-point temperature (oC) Fig. 3. Tenderness ratings assessed by a consumer panel in beef longissimus muscles cooked at four different end-point temperatures. Panel A indicates least squares means of all panelists. Panels B and C indicate least squares means of consumer groups 1 and 2 classified by a cluster analysis, respectively. Values with different superscript mean differ significantly (P b .05) within each panel. Asterisk means that the value is significantly different (P b .05) between consumer groups 1 and 2 at the same cooking end-point temperature.

-3

50

60

72

92

Cooking end-point temperature (oC) Fig. 4. Texture liking ratings assessed by a consumer panel in beef longissimus muscles cooked at four different end-point temperatures. Panel A indicates least squares means of all panelists. Panels B and C indicate least squares means of consumer groups 1 and 2 classified by a cluster analysis, respectively. Values with different superscript mean differ significantly (P b .05) within each panel. Asterisk means that the value is significantly different (P b .05) between consumer groups 1 and 2 at the same cooking end-point temperature.

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or even lower degrees of doneness, should be investigated in more detail.

3.3. Consumer segmentation and linking with trained sensory data One of the aims of this study is to investigate how consumer tenderness varied. For this purpose, we divided participants into two groups, 1 and 2, by tenderness ratings of each participant using a cluster analysis. The numbers of participants were 56 and 51 for groups 1 and 2, respectively. Fig. 3 (B) and (C) indicate tenderness ratings in groups 1 and 2, respectively. In group 1, the tenderness rating was the highest at 60 °C of end-point temperature, and decreased along the end-point temperature above 60°C (Fig. 3(B)). In contrast, group 2 consumer tenderness at 50 °C was lowest in the four end-point temperatures and was significantly different from the rating in group 1 at the same end-point temperature (P b .05) (Fig. 3(C)). The consumer tenderness in group 2 did not differ from those of group 1 at each end-point temperature above 60 °C (P N .05) (Fig. 3(C)). We also assessed texture likings in groups 1 (Fig. 4(B) and 2 (C)). The tendency of changes in texture liking seemed similar to those in consumer tenderness in each consumer group. In particular, texture liking decreased above 60 °C of end-point temperature in both groups, while texture liking in group 2 at 50 °C was the lowest in the four end-point temperatures (P b .05) and was significantly different from that in group 1 (P b .05). The results of multiple regression analysis between consumer tenderness perception with ‘chewiness’ and ‘hardness’ ratings assessed by a trained panel are presented in Fig. 5(A). This figure indicates the multiple regressions of all participants. Consumer tenderness was significantly related with both ‘chewiness’ and ‘hardness’ (P b .001), and the regression coefficients for both descriptors were significantly negative (P b .001). Using all participants' data, consumer tenderness is explained as ‘low chewiness and low hardness.’ On the other hand, we also presented the explanation of consumer tenderness in each consumer group. As shown in Fig. 5(B), group 1 consumer tenderness was significantly related with ‘chewiness’ (P b .001) while the coefficient of ‘hardness’ was not statistically significant (P N .05). In contrast, ‘hardness’ was strongly related to group 2 consumer tenderness (P b .001) rather than ‘chewiness,’ whose coefficient was also statistically significant (P b .05) (Fig. 5(C)). According to these results, we characterized consumer groups 1 and 2 as ‘tenderness is mainly low-chewiness’ and ‘tenderness is mainly low-hardness’ in terms of tenderness perception, respectively.

3.4. Demographic characteristics and questionnaire study in consumer In order to understand what affects the variability of consumer tenderness, we analyzed differences of demographic and attitudinal characteristics between consumer groups. Consumer characteristics such as age and gender in groups 1 and 2 did not differ from each other (P N .05, data not shown) under chi-square analysis. Preferences for beef dishes in the two groups also did not differ from the other group in all questions (P N .05, data not shown). Fig. 6 indicates the questionnaire results of requirements for beef characteristics in two consumer groups. Only ‘feeling of chewing with tasting well’ (in Japanese ‘Kamishimeru-kanji’) differed significantly between the two groups (P b .001). We also analyzed preliminarily the effects of gender and age of panelists on tenderness ratings using MIXED procedure, and found that gender and age group did not affect the tenderness ratings by consumer panelists (data not shown). These findings suggested that texture expectation, rather than demographic characteristics and preferences of beef dishes, is a potent contributor in consumer perception of meat tenderness.

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4. Discussion In this study, we tried to characterize Japanese consumer's perception of tenderness using subjective sensory items such as ‘chewiness’ and ‘hardness’ expressed in ISO11036:1994 assessed by a trained sensory panel. Our results indicated that the overall Japanese consumer tendency regarding meat tenderness was ‘low-chewiness and low-hardness,’ suggesting that sensory chewiness and hardness are useful descriptors to improve the consumer-preferred tenderness of meat. Furthermore, consumer sensory expressions may include variable meanings as described above regarding tenderness (Destefanis et al., 2008). However, sufficient investigation has not been conducted regarding the various meanings of consumer sensory terminology. In the current study, we divided consumers into two groups, and presented the meanings of beef tenderness in both groups using subjective texture descriptors such as ‘chewiness’ and ‘hardness’. To the consumer mind, ‘tenderness’ includes ‘hardness’ only in group 1, although ‘chewiness’ contributed to tenderness meanings in both consumer groups investigated. Fillion and Kilcast (2002) demonstrated that the use of ‘crispness’ by consumers varied, although they did not discuss detailed differences in its meaning among consumers. There have been several reports which pointed out differences in sensory tenderness perceptions among subjects. Some of these works indicated the varieties of time–response of tenderness perception using time–intensity method (e.g. Brown, Gérault, & Wakeling, 1996; Zimoch & Gullett, 1997). In contrast, a few studies were conducted regarding consumer sensory terminology and descriptive sensory texture characteristics. For example, Muñoz and Chambers (1993) reported that consumer ‘firmness’ was related to descriptive ‘firm skin’, dense, and springy. However, variations among consumers' perception for meat tenderness have not been well investigated using subjective sensory descriptors. In contrast, our study was the first to present the differences in the meanings of sensory terminology, in particular ‘tenderness,’ among consumers using internationally established texture descriptors. It is very intriguing how consumer tenderness perception varies. Questionnaire results in this study provide a key to understand this problem. The ‘feeling of chewing to taste well’ (in Japanese, ‘Kamishimeru-Kanji’), for example, was different between groups 1 and 2 in this study (Fig. 6); it involves the meaning of ‘satisfaction by chewing,’ according to a Japanese questionnaire study (Yamaguchi, 2005). Attitudinal characteristics affect customer preferences for food. For example, characteristics that Italian consumer disliked or avoided in fresh tomatoes were different among consumer segments with different preferences (Sinesio et al., 2010). In our study, expectations for chewing characteristics affected consumer tenderness perception in beef. These findings suggested that attitude and expectation in consumers are important factors for sensory perceptions in untrained consumer assessors. Further investigation to determine how such attitudes and expectations develop in consumers will provide valuable suggestions to understand the variation in consumer tenderness perception. Another key is the cultural ambiguity of the Japanese language, as reflected in the use of ‘yawaraka-i’ (adjective) or ‘yawaraka-sa’ (noun) for ‘tenderness’; however, ‘yawaraka-i’ means both tender and soft, which can be defined as low-chewiness and low-hardness, respectively. In other words, native Japanese do not really distinguish between ‘tenderness’ and ‘softness’ because they do not receive any training regarding sensory descriptors. The problem is compounded by our lack of sufficient data to evaluate how such linguistic problems affect the consumer's perception of ‘tenderness.’ As described above, Muñoz and Chambers (1993) indicated the relationship between consumer perceptions for ‘firmness’ and descriptive sensory traits assessed by a trained panel in English. Nevertheless, it is unclear whether such previous work and our findings could be applied to different cultures and languages. Cross-cultural studies should also be conducted on whether linguistic factors contribute to the variability of tenderness perception in consumers other than Japanese speakers.

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A) All participants Tenderness = 8.11 + (-1.13)***chewiness + (-0.63)***hardness R2=0.193***

2 1 0 -1 -2

Consumer 'tenderness'

3

-3 3 4

3 4 5 Train ed 'chew panel iness '

6

l ne a p 5 s' ed nes n i d a Tr 'har

B) Group 1 Tenderness = 8.21 + (-1.79)***chewiness R2=0.389***

2 1 0 -1 -2

Consumer 'tenderness'

3

-3 3 4

3 5

4 5 Train ed p a ne 'chew iness l '

6

l ne pa s' ed es ain rdn r T 'ha

C) Group 2 Tenderness = 8.00 + (-0.41)*chewiness + (-1.42)***hardness R2=0.251***

3

1 0 -1 -2

Consumer 'tenderness'

2

-3 3 4

3 4 5 Train ed 'chew panel iness '

6

l ne a p 5 s' ed nes n i d a Tr 'har

Fig. 5. Relationship of consumer tenderness ratings with trained panel ‘chewiness’ and ‘hardness’ ratings in beef longissimus muscles. Panel A indicates the relationship in all participants. Panels B and C indicate the relationships in consumer groups 1 and 2, respectively. Factors with asterisk in each eq. in panels A, B, and C were statistically significant (*, P b .05; ***, P b .001). Correlation coefficients with asterisk in panels A, B, and C were also statistically significant (***, P b .001).

Oral biology also may well be a strong tool to understand the variability of tenderness perception in consumers. For example, Mathonière, Mioche, Dransfield, and Culioli (2000) investigated the relationship between chewing patterns measured using electromyography and sensory tenderness, and concluded that tenderness assessment requires

structural disintegration of meat. Our results also suggested that the ease with which morsels can be broken into pieces for swallowing is an essential characteristic for consumer perception of tenderness, because ‘chewiness’ contributed to tenderness perception in both consumer groups (Fig. 5(B) and (C)). In addition, chewing efficiency determined

K. Sasaki et al. / Meat Science 96 (2014) 994–1002

(not required) -3 -2 -1

0

+1

(required) +2 +3

high-class building up of stamina nutrient / nourishment fullness

(Group 2)

heaviness feeling of chewing with tasting well chewiness

* (Group 1)

tastefulness

1001

5. Conclusion In the present study, we demonstrated a subjective explanation of consumers' beef tenderness using internationally defined texture descriptors. Overall, Japanese consumers' understanding of tenderness was in terms of ‘low-chewiness and low-hardness.’ Our study also presented descriptive differences of tenderness perceptions in Japanese consumers, such as ‘tenderness is mainly low-chewiness’ and ‘tenderness is mainly low-hardness’. These results provide useful information for beef suppliers on how to improve the beef quality so as to assure greater consumer satisfaction.

smoothness lightness melting feeling sense of fulfillment happiness Fig. 6. Requirements for beef characteristics assessed by a questionnaire survey in two consumer groups classified according to tenderness perceptions. Circles and triangles were values of groups 1 and 2, respectively, expressed as means ± SD. Values with asterisk differed significantly between consumer groups within each question (P b .05).

using the time–intensity method and electromyography divided human subjects into four groups, and their tenderness perceptions differed between the groups (Braxton, Dauchel, & Brown, 1996). Oral biological techniques such as monitoring and analysis of chewing patterns should provide more useful information regarding the variability and its expression of consumer perception for meat tenderness. Moreover, this study employed a linear model for regression analysis between consumer tenderness and trained panel texture ratings because the consumer and trained panel tested four kinds of samples. Muñoz and Chambers (1993) reported that correlations between consumer perception and descriptive sensory results were not always linear in meat products. Chen and Opara (2013) also pointed out limitations of sensory perception because of non-linear sensory response to food mechanical stimulus. According to these problems, our results could not be applied to meat samples with texture deviated from the range of the sample in this study. More samples with various texture characteristics and other than a linear regression model must be used to examine wider relationships between consumer tenderness and subjective sensory words. Meat manufacturers need an instrumental texture monitoring system other than sensory evaluation because it is time-consuming and expensive. Hence, although most of the instrumental texture measurements have been developed as reviewed by Chen and Opara (2013), on the other hand, our results suggested the usefulness of sensory ‘chewiness’ and ‘hardness’ as objective texture descriptors to manage meat tenderness. For applications of these findings to meat producers, instrumental monitoring techniques for sensory ‘chewiness’ and ‘hardness’ must be developed. WBSFV has been most widely used to assess meat texture characteristics as related to consumer tenderness and satisfaction (e.g. Destefanis et al., 2008; Rodas-González et al., 2009). Moreover, WBSFV does not provide detailed descriptive texture characteristics such as chewiness and hardness. According to this study, TPA hardness is one of the potential candidates for monitoring sensory chewiness and/or hardness, whereas WBSFV did not significantly correlate with instrumental texture characteristics. In contrast, our previous results also suggested the relationship between sensory chewiness and WBSFV (Sasaki et al., 2010). Our findings including this and previous studies were insufficient to develop instrumental measurements for sensory chewiness and hardness. Detailed relationships of instrumental measurements with sensory chewiness and hardness should be clarified to develop a new texture monitoring system for management of meat tenderness and consumer satisfaction in meat producers and manufacturers.

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