Assessment of Juiciness Intensity of Cooked Chicken Pectoralis Major

The objectives were to assess sensory descriptive juiciness of cooked chicken breast meat (pectoralis major) during the entire process of consumption and to determine the relationship between sensory juiciness intensity scores during eating and raw meat characteristics. Chicken breast fillets were collected from a commercial processing plant and deboned at three different postmortem times (0, 2, and 8 h). Fillets were ground and made into 90-g patties. The patties were stored in a -20oC freezer and were cooked to 78oC directly from the frozen state. The raw meat characteristics were indicated with color, pH, moisture content, and water-holding capacity. Sensory assessment for juiciness was made by a 7-member, trained descriptive panel using a TimeIntensity (TI) method followed by an overall juiciness perception (or sustained juiciness). TI score curves for cooked chicken fillets followed a similar pattern regardless of deboning time. There was no interaction between deboning time and chewing time and no significant effect of deboning time on juiciness (P > 0.05) regardless of chewing time. During chewing, the highest scores were noticed between 15 and 25 sec, overall. The intensity scores were lower (P < 0.05) at the beginning of consumption and also near swallowing. Juiciness intensity scores in the early evaluation (initial juiciness) were strongly correlated to each other (P < 0.01 and r ≥ 0.79). However, for the intensity scores collected between 20 and 40 bites during chewing, correlations were neither significant (P > 0.01) nor strong (r < 0.70). Sustained juiciness was strongly correlated (P > 0.70) with initial juiciness (< 15 sec). The best linear relationship between juiciness intensity scores and raw meat characteristics measurements was found between the early juiciness scores (< 15 sec) and thaw-cook yield (r > 0.6). Using the TI method for descriptive sensory analysis, these results indicated that the sensation of chicken breast meat juiciness changes during chewing but is not affected by deboning times. Any measurement of the initial juiciness provides intensity scores similar to each other and is a good indicator for sustained juiciness in cooked chicken breast meat regardless of deboning time. Furthermore, thaw-cook yield can potentially be used as an indicator of juiciness in cooked chicken breast meat.


Introduction
Juiciness is one of the most important quality attributes during meat consumption [1]. Meat juiciness is typically measured by sensory evaluation [1], and its definition often varies by study. The term juiciness can refer to the overall impression of moisture perceived in the mouth during chewing (also called sustained juiciness), in which saliva formation could be a factor [2]. Juiciness can also refer to the amount of moisture released from the food after the initial few chews (also called initial juiciness or moisture release), in which juiciness more relies on moisture in products and saliva formation is not involved [3]. The relationship between these two-evaluation results is not well established in meat. The number of initial chews that should be used before the juiciness score is determined is not well defined and inconsistent in the literature [4][5][6]. Boneless skinless chicken breast (pectoralis major) is the most popular poultry meat product in the U.S. market. Texture is the major quality concern associated with boneless skinless chicken breast [7][8][9] and is commonly measured in breast meat quality assessments [ 1 0 -1 3 ] . Juiciness is one of the texture attributes included in sensory evaluation of cooked poultry breast meat. Published data have shown that juiciness is typically unaffected by chicken production and processing conditions [ 6 , 1 0 , 1 4 , 1 5 ] . DOI: 10.29011/2575-7091.100052 However, the methods used to measure the juiciness of cooked chicken breast meat have been limited to the sensory perception at a particular moment or based on a static method [ 1 6 , 1 7 ] even though most processes involved in eating, e.g. mastication and salivation, are dynamic processes. Thus, methods acknowledging dynamic properties of eating are likely to produce results more valid than static methods. Time-Intensity (TI) is a technique for recording changes in the intensity of sensory perceptions with respect to time [18]. In meats research, TI has been used to record temporal changes in perception of texture. Duizer et al. (1993) [19] used TI method to measure tenderness of different beef muscles and found that the TI curves could be used to successfully separate muscles and group trained panelists into two clusters based on their TI perception patterns. Bulter et al. (1996) [20] used the TI method to assess the meat texture attribute of tenderness. They concluded that compared with single point assessments by trained panelists (static method), TI results not only were comparable in discriminating the effects of breeds and sample types on the perception of pork tenderness, but also provided a clearer illustration of the nature of the differences. Lorido et al. (2014) [21] found that TI was a suitable technique to assess the impact of composition and structure on both flavor and texture perceptions in a variety of pork meat products and concluded that TI data provided additional insight on sensory perception compared to quantitative descriptive analysis. An evaluation of poultry meat using the TI method has not been reported and may provide new insights into the sensory quality traits of cooked poultry meat products. The objective of the present study was to investigate the juiciness intensity scores during chewing using the TI method and their relationship to moisture release during initial juiciness evaluation, sustained juiciness, and raw meat characteristics in cooked chicken pectoralis major. Because Postmortem (PM) deboning time significantly affects texture properties of breast meat, the breast meat used in this experiment were deboned at three different PM times.

Broiler Breast Fillet Samples
During each of 4 replications, commercially processed and eviscerated pre-chill carcasses from broilers (approximately 42 d old) were obtained from a local processing plant (Athens, GA). Carcasses were placed in coolers and transported to the laboratory within 20 min. Breast fillets from three carcasses were removed from bones pre-chill (about 45 min PM). Carcasses used for 2 and 8h samples were chilled in a pre-chill water tank at 14 o C for 0.25 h followed by submersion in water immersion chill tanks at 0-4 o C for 60 min. Three immersion-chilled carcasses were deboned at 2 h PM and three chilled carcasses were placed in ziploc freezer bags (1 carcass/bag) and held at 1-2 o C in a refrigerator for 6 h before being deboned 8 h PM.

Meat Quality Characteristics (Color, pH, Moisture, and Water-Holding Capacity)
Surface color (CIE L*a*b*) of skinless boneless broiler breast were measured with a Minolta spectrophotometer CM-2600d (Konica Minolta, Ramsey, NJ) with settings of illuminant 10°C observer, specular component excluded, and an 8-mm aperture. Surface measurement areas were selected to avoid obvious defects (bruises, discolorations, hemorrhages, or any other conditions that might have prevented uniform color readings). Three measurements were taken on the bone or medial side of the fillet. Each measurement was the result of 3 averaged readings by the spectrophotometer. The pH of the fillets was determined at the cranial end with a Sentron model 2001 pH meter and a Lance FET piercing probe (Sentron, Gig Harbor, WA). Moisture content was measured by the AOAC method [22]. Breast meat (25 g) was minced with a one-touch chopper (The Black & Decker Corporation, Towson, Maryland, USA) for one minute. Five grams of minced meat was dried in an aluminum pan at 100°C for 18 h. The sample was weighed after being cooled to room temperature in a desiccator. Water-Holding Capacity (WHC) was estimated in the fillets using the filter paper press method, a swelling/ centrifugation method, and a cooking method. The filter papers method described by Honikel and Hamm (1994) [23] was used to determine the amount of expressible fluid. Three hundred mg of meat tissue from the cranial end of fillets was placed on filter paper (11 cm diameter Whatman No. 1 filter paper) and pressed at 50 kg (a 50 kg-load cell) for 5 min by a TA-XTPlus Texture Analyzer (Stable Micro Systems, Surrey, UK). The wet filter paper was then scanned into a computer using Canon scanner (Model: CanoScan LIDE 60, Canon USA, Inc. Lake Success, NY 11042). The meat area and the total fluid area were measured using the computer with Adobe Photoshop software (CS3 Extended, San Jose, CA 95110). The results were expressed as a ratio of fluid area over total fluid area (Kauffman et al., 1986) [24] to estimate amount of expressible fluid (fpWHC) in meat. A swelling/centrifugation method similar to that developed by Wardlaw et al. (1973) [25] was used for estimation of water uptake by the fresh meat. Ten grams of the minced meat sample (from the meat chopped for moisture analysis) and 15 mL of 0.6 M NaCl solution were added into a 50-mL centrifuge tube and mixed with a Vortex mixer for 1 min. The tube was then refrigerated at 4oC for 15 min before being centrifuged at 4oC at 3,000 g for 15 min. The water uptake (% scWHC) was determined by the formula: % salt-induced water uptake = 100 x (Wpellet -Wsample)/Wsample Where Wsample represents initial muscle sample weight and Wpellet refers to the solid material at the bottom of the tube after centrifugation. For the cooking method, the patties were cooked in individual vacuum-sealed bags. Cook yield included both thaw yield and cook yield and was calculated by 100 x (Wcooked/ Wfresh), where Wcooked represents sample weight after cooking and Wfresh refers to the initial sample weight before freezing at -20 o C.

Sample Preparation and Cooking
Composite patties (3 patties/deboning time/rep) were prepared by grinding the remaining portions of the breast fillets with a Megaforce 3000 series TM air cooled electric meat grinder with a chopper plate of 1/4" square hole. After grinding, the meat was manually homogenized and circular 90-gram composite patties (9 cm in diameter and 0.5 cm thick) were formed using a round Ateco cutter (August Thomsen Corp, Glen Cove, N.Y. N.Y. 11542). Patties were then individually placed in polymeric cooking bags (Seal-a-Meal, The Holmes Group, El Paso, Tex., U.S.A.) and stored at -20°C before use. All samples were cooked directly from the frozen state to an internal temperature of 78-80°C in a Henny Penny MCS-6 combi oven (Henny Penny Corp. Eaton, OH 45320) set at 85 o C on the tender steam setting. Internal temperatures were checked with a hand-held Digi-Sense digital thermometer fitted with a Physitemp hypodermic needle microprobe. The purpose to use chicken breast patties in this study was to reduce variations in sensory juiciness intensity evaluation.

Sensory Evaluation
Samples were analyzed by a 7-member trained panel with more than 100-h training and more than 2-years experience in sensory evaluation of cooked chicken meat. Cooked patties were portioned using an apple wedge cutter. Each panelist received one wedge. TI-juiciness of the meat samples was assessed for 40 seconds on 0-15 point line scale using a Spectrum ™ like approach. Trained assessors chewed at a rate of one chew/sec and selected zero when samples were ready to swallow. Overall juiciness, as a sustained juiciness assessment [26], was scored following TI assessments.

Statistics
Statistical analyses were conducted using SAS (SAS version 9.4, SAS Institute Inc., 2013, Cary, NC). Meat quality characteristics were analyzed as a one-way ANOVA (deboning time) using PROC GLM. For sensory data, the means of intensity scores collected from individual panelists were first calculated for each patty. Then they subjected to a two-way ANOVA with PROC GLM procedure with deboning (hot-boned, 2h, or 8h), chewing time (overall, 1, 2, 5, 10, 15, 20, 25, 30, 35, or 40sec), and their interaction as main effects in addition to replication. Means were separated with the Tukey option at a significance level of 0.05. Pearson's correlations between measurements were determined via PROC CORR with a determinant of significance at P < 0.01.

Results and Discussion
Tables 1 and 2 show the broiler carcass weights and the meat quality characteristics of the chicken breast fillets used in this study. Average carcass weight was 1521 g and L* and pH values of broiler breast meat were 50.9 and 5.96 (Table 1). There were no significant differences (P > 0.05) in carcass weight, thaw-cook yields, or fpWHC between the three deboning times. However, significant differences (P < 0.05) were noted for CIE L*a*b* values, pH, moisture content, and scWHC among the three deboning times. L* values of 2h and 8h samples were significantly higher than hot-boned fillets and pH values of 8h samples were significantly lower than hot-boned and 2h samples. It has been well documented that there are a positive relationship between L* values of chicken breast fillet surfaces and aging time and negative relationships between pH values and aging time and between pH and L* values during the early postmortem period [27][28][29][30][31].

DEBONING TIME Carcass weight (g) CHICKEN BREAST FILLET L* (lightness) a* (redness) b*(yellowness) pH
Hot-boned 1497 a ± 51 47.2 b ± 0.4 -0.26 b ± 0.23 8.7 b ± 0.4 6.14 a ± 0.04 2 h 1497 a ± 49 51.6 a ± 0.7 0.55 a ± 0.22 10.8 a ±0.6 6.01 a ± 0.04 8 h 1570 a ± 38 53.9 a ± 1.1 0.04a b ± 0.22 9.5a b ± 0.5 5.73 b ± 0.06 a,b Mean values with no common superscript in the same column are significantly different (P < 0.05).  These relationships are generally attributed to glycolysis and the formation of lactic acid in muscles after slaughter [32]. The results in the current study are well in line with published data, indicating that there were differences in the fillet properties between the three PM deboning times. Average TI-curves for the three deboning treatments and the TI juiciness intensity scores extracted from the TI curves are shown in Figure 1 and Table 3, respectively. The perception of juiciness in cooked breast meat deboned at the three different PM times followed similar patterns throughout the duration of eating (Figure 1). The average intensity scores reached 3.3-3.7 after the first second of bites. After that, only slight increases were noticed in the intensity scores and the changes varied with PM deboning time.
After 30 sec of chewing, however, the intensity scores dropped rapidly from > 3.7 to 1.4 regardless of deboning time. Although the specific patterns might differ from panelist to panelist [33,34], a similar overall pattern in the juiciness intensity scores has also been found during chewing of different meat samples [21,35,36]. In the literature, the sudden drop in the intensity juiciness score at the end of the evaluation of a meat sample has been called a 'ski jump' effect and attributed to the fact that juiciness, unlike tenderness, persisted throughout the mastication to the point of swallowing and thus terminated abruptly [34].

JUICINESS ASSESSMENT/SECOND DEBONING TIME OVERALL Hot-boned 2 h 8 h
One (initial juiciness) 3.3 3.3 3.7 3.4d Two (initial juiciness) 3.6 3.6 3.9 3.6cd Five (initial juiciness) 3.8 3.9 4.2 3.9abc Intensities with a higher number are stronger (16-point scales). SE = standard error. Error mean square (EMS) was 0.1 for deboning time X chewing time means and 0.2 for overall means. Table 3: Average intensity scores of descriptive sensory texture attribute juiciness of broiler breast muscle meat (pectoralis major) deboned at different postmortem times (mean ± SE, n = 12) 1 . There were no significant differences in average juiciness intensity scores between the three deboning times regardless of chewing time (Table 3). However, there were significant differences in the scores during chewing (Table 3). Overall, the highest intensity score was after 10 sec (or bites), which was significantly higher than the score at the first and second sec and the scores after 30 sec. There were also no differences (P > 0.05) between the overall juiciness (sustained juiciness) intensity scores and the juiciness intensity scores after 2 sec and before 30 sec. However, there were differences (P < 0.05) between the sustained juiciness scores and the scores before 2 sec and after 30 sec. Juiciness has been one of the most commonly evaluated sensory attributes for cooked chicken breast meat. However, it is hardly affected by chicken production practices [14,15] or primary processing techniques [37,38]. Zhuang et al. (2007) [6] randomly collected 6 different brands of boneless skinless chicken breast products (without additives), which could have been processed and handled very differently, from local grocery stores in Athens, GA, and did not find any significant difference in average intensity scores of juiciness between the brands. Cavitt et al. (2005) and Xiong et al. (2006) [10,12] measured juiciness intensity scores of cooked broiler breast fillets deboned at 9 different times within 24 h PM and found no differences between those deboning times. Our re-sults, in agreement with those data, further demonstrate that PM deboning time does not significantly alter the juiciness perception of cooked chicken breast meat at any evaluation point throughout mastication. However, average values of juiciness intensity scores for cooked chicken breast meat could differ depending upon the time during chewing at which juiciness is recorded. For cooked chicken breast fillets, the perception between 5 sec and 30 sec for juiciness intensity were similar to each other and sustained juiciness scores are similar to these juiciness scores. Table 4 shows the descriptive statistics for the variables measured in this study. For juiciness intensity scores, relatively more variation (coefficient of variation was greater than 12%) was observed at the beginning (fewer than 10 sec or bites) and end (more than 30 sec or bites) of mastication compared with those between 20 and 25 sec (coefficient of variation was less than 8%) of TI evaluation. In a study on the sensory perceptions of tenderness and juiciness of cooked beef and pork using TI methodology, Brown et al. (1996) [33] made the comparison of the perceptions of juiciness by seven individual panelists during mastication. Their data showed more variations in the juiciness perception at the beginning (less than 10 sec of chewing) and end (more than 20 sec) of mastication among the panelists. Zimoch and Gullett (1997) [34] attributed the variability in TI perception of juiciness among trained sensory panelists to different chewing behavior. Our data here also indicate that it could reduce the variability in juiciness intensity scores if trained sensory panelists were asked to record their perception after more than 10 sec of chewing or to use sustained juiciness in the evaluation of cooked chicken breast meat. Table 5 shows significant (P < 0.01) and strong (r ≥ 0.79) correlations between the juiciness intensity scores evaluated before 15 sec. Scores given at 20 sec were significantly correlated with those at 2 through 15 sec of chewing (P < 0.005) but the correlation coefficients were less than 0.70. Strong correlations (P < 0.01) were observed between TI juiciness scores that were recorded close to each other. There were no significant correlations between juiciness scores collected after 20 sec of mastication and scores before 15 sec of mastication, with the exception of 15 versus 25 sec. There were significant (P < 0.0001) and strong (r > 0.70) correlations between initial juiciness scores (collected before 15 sec) and sustained juiciness scores. There were significant (P < 0.01) but not strong correlations (r < 0.7) between sustained juiciness and juiciness scores collected between the 20 and 25 sec of chewing. However, no significant correlations were found between sustained juiciness and TI scores from greater than 25 sec.   In sensory evaluation, juiciness is typically assessed by one of two criteria: initial juiciness/wetness release or sustained juiciness. Initial juiciness is the wetness during the first few chews produced by a rapid release of meat juices and sustained juiciness is caused by fat in the sample that causes a slow release of saliva after continued mastication [39]. For cooked beef, the principle sources of juiciness reside in the water and intramuscular lipids. When heated and masticated, the broth then promotes saliva production. Therefore, juiciness has been attributed to the flow of juices from the actual meat and the moisture produced by saliva in the mouth during mastication [1,40]. Because of its low fat content (less than 3%), saliva formation stimulated by intramuscular lipids may not play a role in sustained juiciness in chicken breast meat. In the current study, this assertion is supported by the observations that there were no great increases in juiciness intensity scores after the first few bites (Figure 1). These results also demonstrate that the perceptions of both initial and sustained juiciness are similar in cooked chicken breast meat. For cooked chicken breast meat, the juiciness or moisture release intensity scores collected from the initial 15 bites or within TI 15 sec during chewing can be used to predict each other as well as sustained juiciness scores. Thus, any of the scores within 15 sec can be used as meat juiciness measurements without affecting the results. Overall, the initial moisture release (≤ 15 bites) has more impact on the panel's overall juiciness perception than those after 20 sec of chewing. Table 6 shows that there were no significant linear relationships between any of the juiciness intensity score (regardless of TI time) and the measurement of color, moisture content, pH, carcass weight, or fpWHC. However, initial juiciness scores (1-15 sec) and sustained juiciness were significantly correlated with thaw-cook yield (P < 0.01, r > 0.60) and scWHC (P < 0.01, r > 0.50). Despite the fact that juiciness is one of the most commonly evaluated sensory attributes for cooked meat products, standard instrumental methods for measuring juiciness have not been established like they have for tenderness. Although raw breast meat characteristics are often measured, these parameters are rarely related to sample juiciness in cooked meat, especially to sensory juiciness intensity scores. Liu et al. (2004) [32] carried out a principal component analysis of meat characteristics (pH, color, cook loss, and shear force) and sensory measurements of cooked chicken breast deboned at different PM times and found that among the quality characteristics, the highest r value (although it was very weak) existed between cook yield and juiciness intensity scores. With beef steak, Lucherk et al. (2017) [41] assessed the relationships between objective measurements and sensory juiciness ratings and found that of the 21 objective measurements (such as marbling score, CIE L*a*b*, pH, free water, bound water, protein swelling, drip loss, expressible moisture, fpWHC, and water activity) in raw meat, only cook loss was strongly associated with initial and sustained juiciness intensity scores (r > 0.70) followed by fpWHC (r < 0.30). The correlation coefficients for pH, color, drip loss, and expressible moisture were less than 0.22. Our data are consistent with these findings and demonstrate that cook yield may be used to indicate juiciness intensity perception of cooked chicken breast meat. The effect of cook yield/loss on sensory juiciness perception has been attributed to the water loss in raw meat resulting from cooking [4,41]. 12 0 *** P < 0.0001; ** P ≤ 0.001; * P ≤ 0.01. Table 6: Pearson's correlation coefficients between sensory juiciness intensity scores of broiler breast meat and instrumental measurements in broiler breast fillets (n = 36).

Conclusions
Although juiciness in cooked chicken breast meat has been reported frequently in conjunction with tenderness, an in-depth understanding of this sensory attribute and its assessment has been previously lacking. In the present study, sensory juiciness intensity of cooked chicken breast meat was targeted specifically using TI methodology and its relationships with raw meat characteristics were assessed. Results demonstrated that juiciness intensity perception of cooked chicken breast meat follows a similar pattern during mastication regardless of deboning time. Average juiciness intensity scores depend upon the time during mastication at which juiciness is determined, but are not affected by postmortem deboning time regardless of the TI evaluation time. Juiciness intensity perception is not always linearly correlated between different chewing moments. However, there are strong relationships amongst initial juiciness scores and between initial juiciness scores and sustained juiciness scores indicating that they provide similar juiciness attribute assessments in cooked chicken breast meat. Our data also provide evidence that cook yield/loss of raw chicken breast meat could be an indicator for the juiciness perception in sensory evaluation.