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Effects of season and distance during transport on broiler chicken meat
Effects of season and distance during transport on broiler chicken meat ˆ P. Santana,† and F. E. M. Bernal† V. M. dos Santos,∗,1 B. S. L. Dallago,† A. M. C. Racanicci,† A. ∗
Federal Institute of Bras´ılia, 70730-521, Planaltina, Bras´ılia, DF, Brazil; and † University of Bras´ılia, 70910–970, Asa Norte, Bras´ılia, DF, Brazil
ABSTRACT This research aims to evaluate the microclimate of commercial loads of broiler chickens at different distances in the summer (rainy) and winter (dry) seasons and their effects on meat quality. Twelve broiler loads were monitored with a total of 24 crates per load. Data loggers were used to record temperature and relative humidity. The experiment followed a completely randomized design with 48 treatments in a factorial scheme (2 seasons: rainy and dry) x 2 (distances: short and long) x 12 (positions), with 3 replicates per experimental group. In the rainy season, meat quality was influenced by transport distance. For longer distances, it recorded the highest enthalpy comfort index (ECI), suggesting a tendency of
dark, firm, and dry meat (DFD-like) and lower cooking losses (CL). The lowest ECI was recorded during the transport in dry season. Broiler chickens transported and slaughtered in the winter presented meat pH and L∗ (lightness) classified as “normal,” but with higher cooking losses. For the shear force (SF), the seasons and distances had no significant influence on tenderness of the meat. Regarding the crate positioning in the load, no effect was observed during transport on this variable, given the meat quality characteristics of pH, L∗ , CL, and SF. These results suggest that the distance and the seasons present more influence on broiler meat quality than crate position in the truck.
Key words: broiler, microenvironment, pH, texture, water cook loss 2017 Poultry Science 0:1–10 http://dx.doi.org/10.3382/ps/pex282
INTRODUCTION
(Voslarova et al., 2007; Vosmerova et al., 2010), resulting in body weight and carcass yield losses (Barbosa Filho et al., 2014). Under stress, muscle glycogen reserves are consumed, promoting significant changes in the final meat pH. Stress intensity and duration give the meat certain characteristics, such as pale, soft, exudative (PSE) meat and dark, firm, dry (DFD) meat. Stress in a short pre-slaughter period reportedly results in PSE meat, whereas long periods of stress lead to DFD meat (Adzitey and Nurul, 2011). Postmortem pH changes also result in structural changes in muscle fibers, affecting the meat waterholding capacity (WHC) and tenderness. Under stress conditions, PSE meat has higher exudate and lower texture quality due to protein denaturation, which is a problem for both fresh meat trading and cold meat processing (Lesi´ow and Kijowski, 2003). Conversely, DFD meat has a dry appearance because the water inside the muscle is strongly adhered to proteins, preventing water dripping from the meat surface (Swatland, 1995). Meat color is noticeable on supermarket shelves. Consumers can detect specific changes and then reject products (Droval et al., 2012). However, other characteristics, such as meat tenderness and water loss during cooking, can be tested only after preparation and cooking. Texture is related to the quantity of intramuscular water and, therefore, the WHC. Thus, as the muscle
Pre-slaughter management of broiler chickens accounts for significant economic losses in the poultry industry. Transport is the stage with the greatest impact on animal welfare (Mitchell and Kettlewell, 1998; Weeks, 2014) and meat quality (Barbut, 2015). During transport, poultry are exposed to stress factors including transport microclimates, which may compromise thermal comfort and, ultimately, culminate in impaired carcass quality and yield, with visible endproduct changes (Dadgar et al., 2010). Stress begins at catching, continues during transport, and ends only with the slaughter (Ristic and Damme, 2013). The climate and the distance between farm and slaughterhouse determine unfavorable conditions during broiler transport (Warriss et al., 1992; Warriss et al., 2005). Poultry has difficulty with heat exchange with the environment when exposed to high temperatures and humidity in long-distance transport
C 2017 Poultry Science Association Inc. Received March 26, 2017. Accepted September 14, 2017. 1 Corresponding author: [email protected]
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DOS SANTOS ET AL. Table 1. Shipment data conditions (mean ± SD). Season Distance Rainy Rainy Dry Dry
Long Short Long Short
TEMP (◦ C)1 25.7 24.8 19 19.1
± ± ± ±
RU (%)2
1.4 67 ± 3.7 67 ± 3.0 43.5 ± 1.4 45 ±
14.9 13.6 10.6 8
Loading3 (min) 33 31 45 35
± ± ± ±
2 1 3 4
Distance (km) 84 14 96 17
± ± ± ±
Transport4 Feed withdrawal in (h:min) the barn (h:min)
25,55 2:14 ± 38 2,65 37 ± 13 26,78 2:04 ± 40 1,53 48 ± 14
8:15 8:42 7:54 8:49
± ± ± ±
48 36 53 37
Lairage (h:min)5 1:02 59 1:35 1:47
± ± ± ±
44 33 27 38
Total feed withdrawal (h:min)6 12:04 10:49 12:18 11:59
± ± ± ±
42 35 35 37
Dry bulb temperature (◦ C). Relative humidity (%). 3 Loading time. 4 Transport duration (h:min). 5 Lairage time (h:min). 6 Length of feed withdrawal (h:min). 1 2
water content increases, the tenderness increases (Silva et al., 2011). Trends in the poultry industry are established by the consumer demand for improved products. In this way, product standardization at a high-quality level is a basic requirement. Therefore, appropriate pre-slaughter management practices that ensure animal welfare and focus on food quality and safety should meet such requirements. The present study assessed the effects of transport during rainy and dry seasons for long and short distances and the effects of crate position in the truck on broiler meat quality.
MATERIALS AND METHODS Ethical Statement The procedures used in this research were approved by the Ethics Committee on Animal Use of the University of Bras´ılia (University of Bras´ılia; UnB Document Number 130,177/2015).
Experimental Period, Animals, Management, and Transport Condition The experiment was conducted in the Federal District—Brazil, 15.7939◦ South, 47.8828◦ West (Geographic Coordinate System, Latitude/Longitude, Datum WGS84) at an average altitude of 1,130 m and an Aw (Tropical wet and dry) high-altitude tropical climate (according to the K¨oppen-Geiger climate classification), which has dry winters and hot and humid summers. The average annual temperature is 22◦ C, and the relative humidity ranges from 20 to 75%. The data collection period covered both the dry and R rainy seasons. Cobb broilers (2.895 ± 0.20 kg average live weight at 48 d of age at slaughter), consisting of male, female, or mixed broilers, were reared in commercial poultry facilities and fed ad libitum water and a corn- and soybean-meal-based balanced mash diet. The lighting program was 24 h on the first d and 23 h from the second d until slaughter. All shipments occurred in the morning, and detailed information about the shipment conditions (loading time, transport duration, feed withdrawal in the barn, lairage time, and total length
of feed withdrawal) is in Table 1. Each load had 3,640 birds distributed into 520 crates (7 birds per crate).
Experimental Procedures A total of 12 shipments was monitored from catching to slaughter during the daytime when a progressive increase of the temperature was typically observed. This period was the most critical period for the broilers due to their sensitivity to high temperatures. Shipments were classified as short-distance or longdistance, approximately a 15 km route and a 90 km route between the farm and slaughterhouse (Table 1), respectively. The broilers were caught and carried using both hands to hold the wings against the body according to Japanese method. Then, they were transported in R crates (Ref. LN77572822, GRANJTEC , Monte Santo de Minas, MG, Brazil) measuring 73.5 × 53.0 × 21.0 cm (length × width × height). At the slaughterhouse, the trucks were parked in acclimatizing lairage with fans and foggers set in 23.5 ± 1.5◦ C and 84.6 ± 5.3% (humidity). However, the data logger’s information at this time was not taken into account for data analysis from microenvironment assessment. Dry bulb temperature, relative humidity, and barometric pressure data during the trial were collected from records of the National Institute of Meteorology (Instituto Nacional de Meteorologia; INMET, 2015), from an automatic weather station in Bras´ılia-DF, Brazil. Transport microclimate assessment and enthalpy comfort index. Each truck body had 4 rows of crates, measuring 13 crates horizontally and 10 crates vertically, totaling 520 crates. Twenty-four crates were R fitted with data loggers (AK170, Akso , S˜ ao Leopoldo, RS, Brazil). Temperature and humidity were monitored for each crate every 5 min during transport. The data loggers were equally distributed so that each section of the truck body (i.e., front, center, and rear) had 8 data loggers and each half (i.e., top and bottom) had 12 data loggers (Figure 1). The temperature and relative humidity data collected from the 24 data loggers were used to calculate the enthalpy comfort index (ECI). Rodrigues et al. (2011) reformulated the ECI equation to consider barometric
BROILER CHICKENS TRANSPORT AND MEAT QUALITY
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Figure 1. (A) Arrangement of the 24 data loggers. (B) Rear view, highlighting the center rows. Legend of colors: Gray: right and left ends; Blue: center right row; and Yellow: center left row (adapted from Barbosa Filho et al., 2009).
pressure as stated below. The average barometric pressure during the study was 890 mm Hg.
h = 1.006t +
RH (7. 5t/ 237. 3+t ) 10 pb
×(71.28 + 0.053t) Where: h = Enthalpy index (kJ/kg of dry air); t = Dry bulb temperature (◦ C); RH = Relative humidity (%); pb = Local barometric pressure (mmHg). The enthalpy comfort indices were categorized into comfort (35.0 to 48.0 kJ/kg), warning (48.1 to 57.6 kJ/kg), critical (57.7 to 66.1 kJ/kg), and lethal (66.2 to 90.6 kJ/kg) zones for broilers from the sixth wk of age based on Queiroz et al. (2012).
Evaluation of Meat Characteristics pH and objective color measurements. The initial pH (pHi ) measured 15 min postmortem from the Pectoralis major muscle was taken in triplicate usR ing a pHmeter (206–pH2, Testo , Lenzkirch, BadenW¨ urttemberg, Germany) in 24 breast samples per load. After the pH analyses, the samples were kept at 4◦ C until the final pH (pHf ) measurement in triplicate 24 h after slaughter.
Objective color was performed using a colorimeR , ter (CR–400 Model Chroma Meter, Konica Minolta ∗ ∗ Chiyoda, Tokyo, Japan). The luminosity (L ), a (positive is red, negative is green) and b∗ (positive is yellow, negative is blue) values were recorded based on the International Commission on Illumination (CIE) system. The samples were then classified as: normal (pH: 5.70 to 6.00 and L∗ : 44.0 to 53.0); DFD (pH > 6.00 and L∗ < 44.0) or PSE (pH < 5.69 and L∗ > 53.0) according Qiao et al. (2001) and Oda et al. (2003). Water loss measurement. Rectangle-shaped cuts (2.5 × 2.5 × 5.0 cm) of 24 Pectoralis major muscle samples were prepared, in duplicate, totaling 48 samples per load. The samples were placed in aluminum trays and weighed. They were cooked in an electric oven. The samples were turned over at 40◦ C of internal temperature. At 70◦ C, the trays were removed from the oven and weighed, and the cooking loss (CL) was calculated by before and after cooking and expressed in percentage (%). Then, the samples were refrigerated for subsequent tenderness measurements. Meat tenderness (shear force). After CL measurements, the samples were used for shear force (SF) analysis. Three cylindrical samples of 1.27 cm diameter were removed from each meat cube using a stainless steel sampler inserted into each cube along the direction of the muscle fibers. Samples were sheared perpendicularly to the direction of the muscle fibers using a V-shaped cutting blade at a 60◦ angle, a 1.016mm thickness, and at a fixed rate of 20 cm/minute.
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DOS SANTOS ET AL.
Figure 2. Effect of the interaction between position and distance on: (A) enthalpy comfort index (ECI; kJ/kg) during the transport, (B) final pH (24 h postmortem), (C) luminosity (L∗ ), and (D) red content (a∗ ).
The samples were assessed using a texturometer (GR , Manhattan, KS), and the R Eletric, Warner-Bratzler results were expressed as kgf/cm2 (Froning and Uijttenboogaart, 1988).
Experimental Design The experiment followed a completely randomized design with 48 treatments in 2 seasons (dry and rainy) × 2 distances (short and long) × 12 positions (referring to combinations between load sections, halves, and areas) factorial scheme with 3 replicates. In each shipment, 24 meat samples (one broiler chicken per sampled crate) were used in a total of 3 repetitions/ treatment. Statistical analysis. The collected data were subjected to analyses of variance using the general linear model procedure (PROC GLM) of the statistical analR ysis software SAS (v.9.3, Cary, NC) with subsequent comparisons of means using Tukey’s test (5% significance). Correlation among all meat quality variables (pH, L∗ , a∗ , b∗ , CL, and SF) was done using PROC CORR.
RESULTS The average temperature and relative humidity were 25.2 ◦ C and 67%, respectively, in the rainy season and 19 ◦ C and 44.2% in the dry season (Table 1).
Enthalpy Comfort Index The interaction (P < 0.0001; CV = 12.47%) between the season and distance factors showed that the rainy season ECI was significantly higher for long-distance loads (70.6 ± 6.5 kJ/kg; Figure 2A). In the dry season, higher ECI were noticed in short-distance loads (50.5 ± 4.5 kJ/kg). During the rainy season, even higher ECI were observed in long (70.6 kJ/kg) and shortdistance (57.9 ± 9.7 kJ/kg) loads.
Meat Characteristics There was interaction (P = 0.0097; CV = 2.69%) between the season and distance factors on the meat pHf values (24 h postmortem). Thus, higher values (Figure 2B) for this parameter in the rainy season (6.08 ± 0.20) were observed for the long-distance
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BROILER CHICKENS TRANSPORT AND MEAT QUALITY Table 2. Correlation between meat characteristic variables: initial pH (pHi ), final pH (pHf ), luminosity (L∗ ), redness (a∗ ), yellowness (b∗ ), water holding-capacity (WHC), cooking loss (CL), and shear force (kgf/cm2 ). Variables pHf L∗ a∗ b∗ WHC CL SF
pHi
pHf
L∗
a∗
b∗
WHC (%)
CL
−0.182∗∗ −0.052 ns −0.150∗∗ 0.063 ns 0.086 ns 0.043 ns 0.151∗∗
−0.268∗∗ 0.025 ns −0.124∗ −0.132∗ −0.115∗ −0.193∗∗
−0.016 ns 0.322∗∗ 0.051 ns 0.105 ns −0.038 ns
0.367∗∗ −0.130∗ 0.008 ns −0.134∗
0.303∗∗ 0.193∗∗ 0.205∗∗
0.570∗∗ 0.526∗∗
0.042∗∗
∗
P < 0,05. P < 0,01. ns = No significance. ∗∗
loads than that measured for the short-distance loads (5.94 ± 0.14). In the dry season, there was no significant difference between distances, with the final pH average of 5.93. For luminosity (L∗ ), the interaction (P = 0.01; CV = 6.23%) showed that in the rainy season there was a significantly higher mean for short-distance loads (44.37 ± 2.51) compared to long-distance loads (43.40 ± 2.27) (Figure 2C). In the dry season, no significant difference in the mean L∗ was observed between the distances (43.70). Between the rainy and dry seasons, trucks traveling long distances had the same L∗ values. However, trucks traveling short distances in the rainy season had a slightly higher mean L∗ value (44.37 ± 2.51) than in the dry season (43.68 ± 2.71). A pHf of 5.95 ± 0.14 (Figure 2B) and a 43.73 ± 3.04 ∗ L (Figure 2C) were observed for broiler meat in the dry season and in a long-distance load. For a short-distance load in the same season, the values were 5.91 ± 0.14 and 43.68 ± 2.71, respectively. In this study, a negative correlation was detected (r = −0.2677, P < 0.001; Table 2) between pHf and L∗ . The interaction (P < 0.0001; CV = 46.61%) between season and distance on a∗ (red content) showed a significant difference between distances in the rainy season (Figure 2D). The redness was higher in the long distance (3.42 ± 1.47) than in the short distance (2.54 ± 1.11). However, no difference was observed between distances in the dry season. The pHi (Figure 3D) in the dry season (6.72 ± 0.19) was significantly different (P < 0.0001; CV = 2.44%) from that measured in the rainy season (6.64 ± 0.13). A similar trend (P = 0.02) was observed when comparing short- and long-distance loads (Figure 4E), with a higher pHi in the short-distance load (6.71 ± 0.16 vs. 6.66 ± 0.17). In the dry season, the mean drip loss (2.66 ± 1.53%; CV = 17.30%) and CL (14.37 ± 2.71%; CV = 18.09%) were significantly higher (P < 0.0001) than those observed in the rainy season (2.07 ± 0.89% and 12.68 ± 2.17%, correspondingly) (Figure 3A and C, respectively). Higher drip losses (2.57 ± 1.36%; P < 0.0001) and CL (14.18 ± 2.69%; P = 0.005) were noted (Figure 4A and C) in the short-distance loads than in the longdistance loads (2.16 ± 1.17% and 12.86 ± 2.21%. re-
spectively). The CL was negatively correlated (r = −0.115, P < 0.05; Table 2) with pHf , which may have explained the CL. A higher breast muscle SF (P < 0.0001; CV = 29.90%) was observed in broilers transported in the dry season (2.06 ± 0.60 kgf/cm2 ) than in the rainy season (1.75 ± 0.54 kgf/cm2 ; Figure 3B). The meat from the dry season had higher drip and CL, which resulted in decreased degrees of meat tenderness. Conversely, the different distances tested showed no significant SF difference, with average of 1.90 kgf/cm2 . However, the highest muscle water loss was observed when studying the short-distance loads (2.04 ± 0.48 kgf/cm2 ). No significant difference in b∗ values (yellow-blue content) was observed between seasons, whereas a higher b∗ content (P = 0.0003; CV = 43.22%) was recorded in the short-distance loads (3.47 ± 1.09) than in the long-distance loads (2.90 ± 1.65; Figure 4D). No crate position effects were observed on meat characteristics.
DISCUSSION The ECI indicates the degree of comfort provided to animals in a specific rearing environment. During the rainy season, although no broiler deaths were recorded due to transport, the ECI of long-distance loads (70.6 kJ/kg) can be considered lethal, as they were beyond the limits of the comfort zone for broilers over 6 wk old, according to Queiroz et al. (2012). In the same way, during the rainy season, the short-distance loads had a 57.9 kJ/kg ECI and could be classified as within the critical zone. On the other hand, during the dry season, the ECI for long- (46.9 kJ/kg) and short(50.5 kJ/kg) distance loads were in the comfort and warning zones, respectively. Transport operations in the rainy season and longdistance loads (90 km) resulted in a high ECI (70.6 kJ/kg). High temperatures (31.1 ± 3.4◦ C) and the relative humidity (65.4 ± 2.7%) inside the cargo contributed to the high ECI. Increased poultry respiratory activity contributed toward heat loss to the environment and also likely contributed to the increased temperatures and relative humidity inside the loads. The comfort zone of broilers, from the sixth wk of age, reportedly ranges from 21 to 23◦ C and from 60 to 70%
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DOS SANTOS ET AL.
Figure 3. (A) Relationship of initial pH, (B) drip loss (DRIP; %), (C) cooking loss (CL; %), and (D) shear force (SF; kgf/cm2 ) of the Pectoralis major muscle with season.
relative humidity (Furlan and Macari, 2002). In adverse environments, heat exchange through panting is impaired, resulting in heat stress. Conversely, in the dry season, an improved ECI was observed for long-distance loads (46.9 kJ/kg) when compared with short-distance loads (50.5 kJ/kg). The low relative humidity (44.2%; Table 1) in the dry season may favor poultry heat exchange with the environment. Wind also may help with heat dissipation from the poultry body to the environment, especially for longer distances traveled; wind may enable the animals to arrive under better conditions (P´erez et al., 2002). Conversely, short-distance transports were unlikely to decrease the poultry body temperature to homeostasis (Vosmerova et al., 2010). Increased poultry body temperature is a result of stress caused during catching management, crate stacking in the truck body (Queiroz et al., 2015), and subsequent transport. Air conditioning systems in poultry sheds may facilitate poultry heat loss during the catching and caging stages, thereby decreasing panting and body temperature before transport. For loads carried during the rainy season for long distances, the pHf and L∗ values were 6.08 (Fig-
ure 2B) and 43.40 (Figure 2C), respectively, and then the broiler meats were classified as DFD (Qiao et al., 2001; Oda et al., 2003). Conversely, when transported for short distances in the rainy season, the meats had a pH of 5.94 and an L∗ value of 44.37, typical of normal meat. Based on those results, the transport distance had a key effect on the final quality, causing significant changes in the breast muscles of broilers. The combination of rainy season and long-distance loads tended to develop meat with DFD characteristics. DFD meat is typically associated with long periods of stress before slaughter, beginning of catching and crate stacking, and remaining during transport (Ristic and Damme, 2013). In this study, for the rainy season and long-distance loads, the poultry were exposed to high temperatures and relative humidity, hindering poultry body heat loss by evaporation. The energy expenditure with panting reduces muscle glycogen reserves, which further worsens during prolonged travel. Therefore, after slaughter, the muscle pH increases due to the lack energy for lactic acid production, resulting in DFD meat (Scheffler et al., 2011; Barbut, 2014).
BROILER CHICKENS TRANSPORT AND MEAT QUALITY
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Figure 4. (A) Relationship of initial pH, (B) drip loss (DRIP; %), (C) cooking loss (CL, %), (D) shear force (SF; kgf/cm2 ), and (E) yellow content of the Pectoralis major muscle with distance.
Due to altered colorations in DFD quality meat, marketed poultry breast meat is often discarded or considered unfit for consumption (BRASIL, 1998). Consumers avoid purchasing this meat (Rosa et al., 2016) because they tend to prefer meat with a natural appearance, with a pH and color within normal classification parameters (Viljoen et al., 2002). Furthermore, the biochemical changes in DFD quality meat may pose a risk to human health. The high final pH favors bacterial growth, which compromises its shelf life and food safety. Such microbiologically unstable meats must be quickly subjected to heat treatment and used to prepare industrial by-products (Lesi´ ow and Kijowski, 2003). Broilers transported in the dry season had normal standard meat in long- and short-distance loads. The pHf values were within the normal classification range
from 5.70 to 6.00 (Qiao et al., 2001; Oda et al., 2003), and the L∗ values were numerically close to the lower limit (44.0) of the same classification. Therefore, results suggest that broiler transport in the dry season, for both distances, was less critical in terms of changes in meat quality (pHf and L∗ ). According to Qiao et al. (2001), the limits for detecting changes in broiler breast muscles have not yet been well established. Thus, the L∗ value may still be considered a good indicator to classify meat quality deviations. However, a combined analysis of both variables (pHf and L∗ ) may render a safer evaluation, as both parameters may change during the industrial processing, either by excessive scalding or by cooling in the chiller despite a low correlation (Barbut, 2014; Bowker et al., 2014).
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DOS SANTOS ET AL.
The CIE L∗ a∗ b∗ (or Hunter) system defines a∗ and b values to measure red or green and yellow or blue reflectance, respectively. These values corroborated the pHf and L∗ results observed in this study. DFD meat, as observed in the rainy season and long-distance loads, may have higher a∗ values, suggesting that the meat has a more intense red color and retains more water with increased pH (Zapata et al., 2006). The higher redness intensity in DFD meat is due to the higher concentration and rapid oxidation of muscle hemoglobin under higher pH (Boulianne and King, 1998). Despite the slight numerical difference in pHi values, these values are close to 7.0, the physiological pH of muscle according to Lawrie (1998), and thus considered normal for broiler muscle tissue after slaughter. The difference between mean drip loss and CL indicated that the meat of the poultry transported in the dry season had a lower WHC when baked, given the higher muscle water loss. The short-distance transport resulted in higher water losses from the meat after cooking, increasing by approximately 1.32%. The formation of exudate occurred due to the postmortem shrinkage of myofibrils in reduced muscle pH, and this contributes to decreasing the quality in processed meat products (Jensen et al., 1998). Water loss can be used to assess WHC because poultry meat with decreased WHC has been associated with high CL (Northcutt et al., 1994). During 30-minute summer transport loads of broiler chickens, Xing et al. (2016) observed a 15.59% CL and a 13.41% decrease for a pre-slaughter 10-minute water shower spray on meat quality. In regard to our outcomes, short distance presented a similar CL value (14.18 ± 2.69%), and the time of transport to the slaughterhouse was 42 min, on average. However, the dry season resulted in a 14.37 ± 2.71% loss, 1.70% higher than that in the rainy season, which may account for the recommendation to use a water shower spray before poultry transport in the dry season. The inverse relationship between pHf and CL indicates that as the pHf of meat decreased, the CL increased (Caldara et al., 2012). The more acidic pH on meat, the more denatured muscle proteins, which subsequently impaired ability to retain water due to structural changes and higher water drips at the muscle surface (Zhang and Barbut, 2005). The pHf values measured in the dry season (5.93) and for short-distance loads (5.92) were slightly lower than those observed in the rainy season (6.01) and for long-distance loads (6.02). However, the pH values may have caused higher CL. The SF ranged from 4.51 to 6.97 kgf/cm2 in various chicken breast samples sheared with cuts perpendicular to the muscle fiber and at a final cooking temperature of 70 ◦ C, as recommended by Wheeler et al. (1996). These authors also report difficulties in comparing the SF values among research studies due to different analysis methods used. The SF of broiler breast muscles aged for 24 h before freezing ranged from 2.37 to 2.43 kgf/cm2 according to Thielke et al. (2005). ∗
Conversely, Komiyama et al. (2010) measured an average of 4.94 kgf/cm2 , claiming this meat to be slightly less tender than chicken meat. Therefore, the results from this study did not indicate significant differences in meat tenderness for the long- and short-distance loads, with an overall average SF of 1.90 kgf/cm2 . Enzyme activity during the meat maturation process may be correlated with the SF. The activity of enzymes, including cathepsins and calpains, in postmortem proteolysis contributed to the weakening of the muscle fibers and improvements in the meat texture (Barbut, 2014). Furthermore, the aging period and meat preservation method established in this study, i.e., 24 h of cooling to 2 to 5◦ C, may have contributed to the activity of those enzymes, resulting in meat with better tenderness (Zapata et al., 2006). Meat tenderness may be considered one of the most important factors attributed to consumer acceptance (Hong and Lee, 2012). Furthermore, meat texture may contribute toward the assessment of pre- and postslaughter management conditions because both field and postmortem stages may affect variables linked to meat quality. Considering b∗ value results, PSE meat has a more acidic pH and higher yellow component intensity (b∗ ) due to its pale color (Warriss, 2010). In relation to crate position, few studies have reported significant correlations between truck body areas of highest thermal discomfort and incidence of meat quality deviations. When analyzing microenvironment effects on the occurrence of PSE and DFD meat in broilers, Langer et al. (2010) observed that the rear of the vehicle, which has the highest temperature and relative humidity, resulted in a higher percentage of PSE meat. This incidence decreased in broilers located upon moving from the middle to the front of the cargo bay. Concluding, in the rainy season, the transport distance caused significant changes in meat quality. The highest ECIs were recorded for the long-distance loads, suggesting DFD meat with decreased water losses from cooking. Conversely, the dry season had lower ECIs during transport, which was better in terms of poultry comfort. Broilers transported and slaughtered in that season had meat with pH and L∗ values classified as normal and with high CL and drip losses. The CL observed (14.37%) was inherent in the cooking process and was within the normal range of loss. The season and distance factors had no significant effects on the SF tenderness of the meat. The crate position in the truck had no effects on pH, L∗ , CL, or SF. These results show that distance and season, rather than crate location, had stronger effects on the quality of broiler meat.
ACKNOWLEDGMENTS The authors thank Bonasa Alimentos S.A (Bras´ılia, Brazil) for making this study possible.
BROILER CHICKENS TRANSPORT AND MEAT QUALITY
REFERENCES Adzitey, F., and H. Nurul. 2011. Pale soft exudative (PSE) and dark firm dry (DFD) meats: Causes and measures to reduce these incidences-a mini review. Int. Food Res. J. 18:11–20. Barbosa Filho, J. A. D., F. M. C. Vieira, I. J. O. D. Silva, D. D. B. Garcia, M. A. N. D. Silva, and B. H. F. Fonseca. 2009. Poultry transport: Microclimate characterization of the truck during the winter. Rev. Bras. Zootec. 38:2442–2446. Barbosa Filho, J. A. D., M. L. V. Queiroz, D. F. Brasil, F. M. C. Vieira, and I. J. O. Silva. 2014. Transport of broilers: load microclimate during Brazilian summer. Eng. Agr. 4:405–412. Barbut, S. 2014. Review: Automation and meat quality-global challenges. Meat Sci. 96:335–345. Barbut, S. 2015. Live bird handling. Pages 1–24 in The Science of Poultry and Meat Processing. Chapter 4. S. Barbut, ed. University of Guelph, Guelph, Ontario, Canada. Boulianne, M., and A. J. King. 1998. Meat color and biochemical characteristics of unacceptable dark-colored broiler chicken carcasses. J. Food Sci. 63:759–762. Bowker, B. C., H. Zhuang, and R. J. Buhr. 2014. Impact of carcass scalding and chilling on muscle proteins and meat quality of broiler breast fillets. LWT - Food Sci. Technol. 59:156–162. BRASIL. Minist´erio da Agricultura e Pecu´ aria e Abastecimento. Portaria n◦ 210, de. 1998. Pages 1–7 in Regulamento T´ecnico da Inspe¸c˜ao Tecnol´ogica e Higiˆenico Sanit´ aria de Carne de Aves. Rep´ ublica Federativa do Brasil, Bras´ılia, DF. Caldara, F. R., V. M. O. Santos, J. C. Santiago, and I. A. N¨ aa¨s. 2012. Physical and sensory properties of PSE pork. Rev. Bras. Saude Prod. Anim. 13:815–824. Dadgar, S., E.S. Lee, T.G. Crowe, H.L. Classen, and P.J. Shand. 2010. Characteristics of cold-induced dark, firm, dry broiler chicken breast meat. Poult. Sci. 53:351–359. Droval, A., V. Benassi, A. Rossa, S. Prudencio, F. Paiao, and M. Shimokomaki. 2012. Consumer attitudes and preferences regarding pale, soft, and exudative broiler breast meat. J. Appl. Poult. Res. 21:502–507. Froning, G., and T. Uijttenboogaart. 1988. Effect of post-mortem electrical stimulation on color, texture, pH, and cooking losses of hot and cold deboned chicken broiler breast meat. Poult. Sci. 67:1536–1544. Furlan, R. L., and M. Macari. 2002. Termorregula¸c˜ao. Pages 209– 230 in Fisiologia Avi´ aria Aplicada a Frangos de Corte. M. Macari, L. R. Furlan, and E. Gonzales, eds. Funep/Unesp, Jaboticabal. Hong, I. K., and Y. S. Lee. 2012. Textural properties and waterholding capacity of broiler breast meat cooked to various internal endpoint temperatures. Food Sci. Biotechnol. 21:1497–1499. Instituto Nacional de Meteorologia (INMET). 2015. Banco de dados meteorol´ogicos para enisno e pesquisa. Accessed Apr. 2015. http://www.inmet.gov.br/portal/index.php?r=bdmep/bdmep. Jensen, C., C. Lauridsen, and G. Bertelsen. 1998. Dietary vitamin E: Quality and storage stability of pork and poultry. Trends Food Sci. Technol. 9:62–72. Komiyama, C. M., A. A. Mendes, C. Sanfelice, M. C. Ca˜ nizares, R. D. O. Ro¸ca, S. E. Takahashi, L. Rodrigues, G. I. L. Ca˜ nizares, I. C. D. L. A. Paz, and K. F. D. G. Cardoso. 2010. Physical, chemical and sensorial breast meat quality of spent breeder hens. Ciˆenc. Rural 40:1623–1629. Langer, R. O. D. S., G. S. Sim˜ oes, A. L. Soares, A. Oba, A. Rossa, M. Shimokomaki, and E. I. Ida. 2010. Broiler transportation conditions in a Brazilian commercial line and the occurrence of breast PSE (Pale, Soft, Exudative) meat and DFD-like (Dark, Firm, Dry) meat. Braz. Arch. Biol. Technol. 53:1161–1167. Lawrie, R. A. 1998. Lawrie‘s Meat Science. 6th rev. ed. Technomic, Lancaster-Basel. Lesi´ow, T., and J. Kijowski. 2003. Impact of PSE and DFD meat on poultry processing –A review. Pol. J. Food Nutr. Sci. 12/53:3–8. Mitchell, M. A., and P. J. Kettlewell. 1998. Physiological stress and welfare of broiler chickens in transit: solutions not problems! Poult. Sci. 77:1803–1814. Northcutt, J. K., E. A. Foegeding, and F. W. Edens. 1994. Waterholding properties of thermally preconditioned chicken breast and leg meat. Poult. Sci. 73:308–316. Oda, S., J. Schneider, A. Soares, D. Barbosa, E. Ida, R. Olivo, and M. Shimokomaki. 2003. Detec¸c˜ao de cor em
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fil´es de peito de frango. Revista Nacional da Carne. 27:30– 34. P´erez, M. P., J. Palacio, M. P. Santolaria, M. C. Ace˜ na, G. Chac´ on, M. Gasc´ on, J. H. Calvo, P. Zaragoza, J. A. Beltran, and S. Garc´ıaBelenguer. 2002. Effect of transport time on welfare and meat quality in pigs. Meat Sci. 61:425–433. Qiao, M., D. L. Fletcher, D. P. Smith, and J. K. Northcutt. 2001. The effect of broiler breast meat color on pH, moisture, water-holding capacity, and emulsification capacity. Poult. Sci. 80:676–680. Queiroz, M., J. Barbosa Filho, and F. Vieira. 2012. Evaluation of the thermal comfort of broilers in a direct and practical way. Revista Produ¸c˜ao Animal-Avicultura. 66:21–24. Queiroz, M. D. V., J. Barbosa Filho, L. Duarte, D. D. F. Brasil, and C. Gadelha. 2015. Environmental and physiological variables during the catching of broilers. Rev. Bras. Cienc. Avic. 17:37–44. Ristic, M., and K. Damme. 2013. Significance of pH-value for meat quality of broilers-influence of breed lines. Veterinarski Glasnik. 67:67–73. Rodrigues, V. C., I. J. D. Silva, F. M. Vieira, and S. T. Nascimento. 2011. A correct enthalpy relationship as thermal comfort index for livestock. Int. J. Biometeorol. 55:455–459. Rosa, A., R. Fonseca, J. C. Balieiro, M. D. Poleti, K. DomenechP´erez, B. Farnetani, and J. Eler. 2016. Incidence of DFD meat on Brazilian beef cuts. Meat Sci. 112:132–133. Scheffler, T. L., S. Park, and D. E. Gerrard. 2011. Lessons to learn about post-mortem metabolism using the AMPKgamma3(R200Q) mutation in the pig. Meat Sci. 89:244–250. Silva, L. B. D. J., L. D. G. Gaya, A. P. Madureira, G. Tarˆ oco, J. B. S. Ferraz, G. B. Mour˜ ao, E. C. D. Mattos, and T. Michelan Filho. 2011. Phenotypic correlations among meat quality traits in broilers. Cienc. Rural. 41:1475–1481. Swatland, H. J. 1995. On-line Evaluation of Meat. Technomic, Lancaster. Thielke, S., S. K. Lhafi, and M. Kuhne. 2005. Effects of aging prior to freezing on poultry meat tenderness. Poult. Sci. 84:607–612. Viljoen, H. F., H. L. D. Kock, and E. C. Webb. 2002. Consumer acceptability of dark, firm and dry (DFD) and normal pH beef steaks. Meat Sci. 61:181–185. Voslarova, E., B. Janackova, F. Vitula, A. Kozak, and V. Vecerek. 2007. Effects of transport distance and the season of the year on death rates among hens and roosters in transport to poultry processing plants in the Czech Republic in the period from 1997 to 2004. Vet. Med. 52:262–266. Vosmerova, P., J. Chloupek, I. Bedanova, P. Chloupek, K. Kruzikova, J. Blahova, and V. Vecerek. 2010. Changes in selected biochemical indices related to transport of broilers to slaughterhouse under different ambient temperatures. Poult. Sci. 89:2719–2725. Warriss, P. D. 2010. Meat quality. Pages 77–84 in Meat Science: An Introductory Text. P. D. Warriss, ed. CABI, Cambridge, United Kingdom. Warriss, P. D., E. A. Bevis, S. N. Brown, and J. E. Edwards. 1992. Longer journeys to processing plants are associated with higher mortality in broiler chickens. Br. Poult. Sci. 33:201–206. Warriss, P. D., A. Pagazaurtundua, and S. N. Brown. 2005. Relationship between maximum daily temperature and mortality of broiler chickens during transport and lairage. Br. Poult. Sci. 46:647–651. Weeks, C. A. 2014. Poultry handling and transport. Pages 174–192 in Livestock Handling and Transport, 4th ed. T. Grandin, ed. CABI, Fort Colins, Colorado. Wheeler, T. L., S. D. Shackelford, and M. Koohmaraie. 1996. Standardizing collection and interpretation of Warner-Bratzler shear force and sensory tenderness data. Accessed Mar. 2016. http:// www.ars.usda.gov/sp2userfiles/place/30400510/1997500068.pdf. Xing, T., X. Xu, N. Jiang, and S. Deng. 2016. Effect of transportation and pre-slaughter water shower spray with resting on AMPactivated protein kinase, glycolysis and meat quality of broilers during summer. Anim. Sci. J. 87:299–307. Zapata, J., A. De Andrade, G. Assun¸c˜ao, S. Barreto, and V. Abreu. 2006. Preliminary evaluation of the effect of frozen storage on the quality of breast meat from two genetic groups of chickens. Braz. J. Food. Technol. 9:185–191. Zhang, L., and S. Barbut. 2005. Rheological characteristics of fresh and frozen PSE, normal and DFD chicken breast meat. Br. Poult. Sci. 46:687–693.
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APPENDIX Abbreviations: a∗ : Red content (redness) b∗ : Yellow content (yellowness) CL: Cooking loss DFD: Dark, firm and dry
ECI Enthalpy comfort index L∗ : Luminosity pHi : Initial pH (15 min postmortem) pHf : Final pH (24 h postmortem) PSE: Pale, soft and exudative SF: Shear force WHC: Water-holding capacity
Federal Institute of Bras´ılia, 70730-521, Planaltina, Bras´ılia, DF, Brazil; and † University of Bras´ılia, 70910–970, Asa Norte, Bras´ılia, DF, Brazil
ABSTRACT This research aims to evaluate the microclimate of commercial loads of broiler chickens at different distances in the summer (rainy) and winter (dry) seasons and their effects on meat quality. Twelve broiler loads were monitored with a total of 24 crates per load. Data loggers were used to record temperature and relative humidity. The experiment followed a completely randomized design with 48 treatments in a factorial scheme (2 seasons: rainy and dry) x 2 (distances: short and long) x 12 (positions), with 3 replicates per experimental group. In the rainy season, meat quality was influenced by transport distance. For longer distances, it recorded the highest enthalpy comfort index (ECI), suggesting a tendency of
dark, firm, and dry meat (DFD-like) and lower cooking losses (CL). The lowest ECI was recorded during the transport in dry season. Broiler chickens transported and slaughtered in the winter presented meat pH and L∗ (lightness) classified as “normal,” but with higher cooking losses. For the shear force (SF), the seasons and distances had no significant influence on tenderness of the meat. Regarding the crate positioning in the load, no effect was observed during transport on this variable, given the meat quality characteristics of pH, L∗ , CL, and SF. These results suggest that the distance and the seasons present more influence on broiler meat quality than crate position in the truck.
Key words: broiler, microenvironment, pH, texture, water cook loss 2017 Poultry Science 0:1–10 http://dx.doi.org/10.3382/ps/pex282
INTRODUCTION
(Voslarova et al., 2007; Vosmerova et al., 2010), resulting in body weight and carcass yield losses (Barbosa Filho et al., 2014). Under stress, muscle glycogen reserves are consumed, promoting significant changes in the final meat pH. Stress intensity and duration give the meat certain characteristics, such as pale, soft, exudative (PSE) meat and dark, firm, dry (DFD) meat. Stress in a short pre-slaughter period reportedly results in PSE meat, whereas long periods of stress lead to DFD meat (Adzitey and Nurul, 2011). Postmortem pH changes also result in structural changes in muscle fibers, affecting the meat waterholding capacity (WHC) and tenderness. Under stress conditions, PSE meat has higher exudate and lower texture quality due to protein denaturation, which is a problem for both fresh meat trading and cold meat processing (Lesi´ow and Kijowski, 2003). Conversely, DFD meat has a dry appearance because the water inside the muscle is strongly adhered to proteins, preventing water dripping from the meat surface (Swatland, 1995). Meat color is noticeable on supermarket shelves. Consumers can detect specific changes and then reject products (Droval et al., 2012). However, other characteristics, such as meat tenderness and water loss during cooking, can be tested only after preparation and cooking. Texture is related to the quantity of intramuscular water and, therefore, the WHC. Thus, as the muscle
Pre-slaughter management of broiler chickens accounts for significant economic losses in the poultry industry. Transport is the stage with the greatest impact on animal welfare (Mitchell and Kettlewell, 1998; Weeks, 2014) and meat quality (Barbut, 2015). During transport, poultry are exposed to stress factors including transport microclimates, which may compromise thermal comfort and, ultimately, culminate in impaired carcass quality and yield, with visible endproduct changes (Dadgar et al., 2010). Stress begins at catching, continues during transport, and ends only with the slaughter (Ristic and Damme, 2013). The climate and the distance between farm and slaughterhouse determine unfavorable conditions during broiler transport (Warriss et al., 1992; Warriss et al., 2005). Poultry has difficulty with heat exchange with the environment when exposed to high temperatures and humidity in long-distance transport
C 2017 Poultry Science Association Inc. Received March 26, 2017. Accepted September 14, 2017. 1 Corresponding author: [email protected]
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DOS SANTOS ET AL. Table 1. Shipment data conditions (mean ± SD). Season Distance Rainy Rainy Dry Dry
Long Short Long Short
TEMP (◦ C)1 25.7 24.8 19 19.1
± ± ± ±
RU (%)2
1.4 67 ± 3.7 67 ± 3.0 43.5 ± 1.4 45 ±
14.9 13.6 10.6 8
Loading3 (min) 33 31 45 35
± ± ± ±
2 1 3 4
Distance (km) 84 14 96 17
± ± ± ±
Transport4 Feed withdrawal in (h:min) the barn (h:min)
25,55 2:14 ± 38 2,65 37 ± 13 26,78 2:04 ± 40 1,53 48 ± 14
8:15 8:42 7:54 8:49
± ± ± ±
48 36 53 37
Lairage (h:min)5 1:02 59 1:35 1:47
± ± ± ±
44 33 27 38
Total feed withdrawal (h:min)6 12:04 10:49 12:18 11:59
± ± ± ±
42 35 35 37
Dry bulb temperature (◦ C). Relative humidity (%). 3 Loading time. 4 Transport duration (h:min). 5 Lairage time (h:min). 6 Length of feed withdrawal (h:min). 1 2
water content increases, the tenderness increases (Silva et al., 2011). Trends in the poultry industry are established by the consumer demand for improved products. In this way, product standardization at a high-quality level is a basic requirement. Therefore, appropriate pre-slaughter management practices that ensure animal welfare and focus on food quality and safety should meet such requirements. The present study assessed the effects of transport during rainy and dry seasons for long and short distances and the effects of crate position in the truck on broiler meat quality.
MATERIALS AND METHODS Ethical Statement The procedures used in this research were approved by the Ethics Committee on Animal Use of the University of Bras´ılia (University of Bras´ılia; UnB Document Number 130,177/2015).
Experimental Period, Animals, Management, and Transport Condition The experiment was conducted in the Federal District—Brazil, 15.7939◦ South, 47.8828◦ West (Geographic Coordinate System, Latitude/Longitude, Datum WGS84) at an average altitude of 1,130 m and an Aw (Tropical wet and dry) high-altitude tropical climate (according to the K¨oppen-Geiger climate classification), which has dry winters and hot and humid summers. The average annual temperature is 22◦ C, and the relative humidity ranges from 20 to 75%. The data collection period covered both the dry and R rainy seasons. Cobb broilers (2.895 ± 0.20 kg average live weight at 48 d of age at slaughter), consisting of male, female, or mixed broilers, were reared in commercial poultry facilities and fed ad libitum water and a corn- and soybean-meal-based balanced mash diet. The lighting program was 24 h on the first d and 23 h from the second d until slaughter. All shipments occurred in the morning, and detailed information about the shipment conditions (loading time, transport duration, feed withdrawal in the barn, lairage time, and total length
of feed withdrawal) is in Table 1. Each load had 3,640 birds distributed into 520 crates (7 birds per crate).
Experimental Procedures A total of 12 shipments was monitored from catching to slaughter during the daytime when a progressive increase of the temperature was typically observed. This period was the most critical period for the broilers due to their sensitivity to high temperatures. Shipments were classified as short-distance or longdistance, approximately a 15 km route and a 90 km route between the farm and slaughterhouse (Table 1), respectively. The broilers were caught and carried using both hands to hold the wings against the body according to Japanese method. Then, they were transported in R crates (Ref. LN77572822, GRANJTEC , Monte Santo de Minas, MG, Brazil) measuring 73.5 × 53.0 × 21.0 cm (length × width × height). At the slaughterhouse, the trucks were parked in acclimatizing lairage with fans and foggers set in 23.5 ± 1.5◦ C and 84.6 ± 5.3% (humidity). However, the data logger’s information at this time was not taken into account for data analysis from microenvironment assessment. Dry bulb temperature, relative humidity, and barometric pressure data during the trial were collected from records of the National Institute of Meteorology (Instituto Nacional de Meteorologia; INMET, 2015), from an automatic weather station in Bras´ılia-DF, Brazil. Transport microclimate assessment and enthalpy comfort index. Each truck body had 4 rows of crates, measuring 13 crates horizontally and 10 crates vertically, totaling 520 crates. Twenty-four crates were R fitted with data loggers (AK170, Akso , S˜ ao Leopoldo, RS, Brazil). Temperature and humidity were monitored for each crate every 5 min during transport. The data loggers were equally distributed so that each section of the truck body (i.e., front, center, and rear) had 8 data loggers and each half (i.e., top and bottom) had 12 data loggers (Figure 1). The temperature and relative humidity data collected from the 24 data loggers were used to calculate the enthalpy comfort index (ECI). Rodrigues et al. (2011) reformulated the ECI equation to consider barometric
BROILER CHICKENS TRANSPORT AND MEAT QUALITY
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Figure 1. (A) Arrangement of the 24 data loggers. (B) Rear view, highlighting the center rows. Legend of colors: Gray: right and left ends; Blue: center right row; and Yellow: center left row (adapted from Barbosa Filho et al., 2009).
pressure as stated below. The average barometric pressure during the study was 890 mm Hg.
h = 1.006t +
RH (7. 5t/ 237. 3+t ) 10 pb
×(71.28 + 0.053t) Where: h = Enthalpy index (kJ/kg of dry air); t = Dry bulb temperature (◦ C); RH = Relative humidity (%); pb = Local barometric pressure (mmHg). The enthalpy comfort indices were categorized into comfort (35.0 to 48.0 kJ/kg), warning (48.1 to 57.6 kJ/kg), critical (57.7 to 66.1 kJ/kg), and lethal (66.2 to 90.6 kJ/kg) zones for broilers from the sixth wk of age based on Queiroz et al. (2012).
Evaluation of Meat Characteristics pH and objective color measurements. The initial pH (pHi ) measured 15 min postmortem from the Pectoralis major muscle was taken in triplicate usR ing a pHmeter (206–pH2, Testo , Lenzkirch, BadenW¨ urttemberg, Germany) in 24 breast samples per load. After the pH analyses, the samples were kept at 4◦ C until the final pH (pHf ) measurement in triplicate 24 h after slaughter.
Objective color was performed using a colorimeR , ter (CR–400 Model Chroma Meter, Konica Minolta ∗ ∗ Chiyoda, Tokyo, Japan). The luminosity (L ), a (positive is red, negative is green) and b∗ (positive is yellow, negative is blue) values were recorded based on the International Commission on Illumination (CIE) system. The samples were then classified as: normal (pH: 5.70 to 6.00 and L∗ : 44.0 to 53.0); DFD (pH > 6.00 and L∗ < 44.0) or PSE (pH < 5.69 and L∗ > 53.0) according Qiao et al. (2001) and Oda et al. (2003). Water loss measurement. Rectangle-shaped cuts (2.5 × 2.5 × 5.0 cm) of 24 Pectoralis major muscle samples were prepared, in duplicate, totaling 48 samples per load. The samples were placed in aluminum trays and weighed. They were cooked in an electric oven. The samples were turned over at 40◦ C of internal temperature. At 70◦ C, the trays were removed from the oven and weighed, and the cooking loss (CL) was calculated by before and after cooking and expressed in percentage (%). Then, the samples were refrigerated for subsequent tenderness measurements. Meat tenderness (shear force). After CL measurements, the samples were used for shear force (SF) analysis. Three cylindrical samples of 1.27 cm diameter were removed from each meat cube using a stainless steel sampler inserted into each cube along the direction of the muscle fibers. Samples were sheared perpendicularly to the direction of the muscle fibers using a V-shaped cutting blade at a 60◦ angle, a 1.016mm thickness, and at a fixed rate of 20 cm/minute.
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DOS SANTOS ET AL.
Figure 2. Effect of the interaction between position and distance on: (A) enthalpy comfort index (ECI; kJ/kg) during the transport, (B) final pH (24 h postmortem), (C) luminosity (L∗ ), and (D) red content (a∗ ).
The samples were assessed using a texturometer (GR , Manhattan, KS), and the R Eletric, Warner-Bratzler results were expressed as kgf/cm2 (Froning and Uijttenboogaart, 1988).
Experimental Design The experiment followed a completely randomized design with 48 treatments in 2 seasons (dry and rainy) × 2 distances (short and long) × 12 positions (referring to combinations between load sections, halves, and areas) factorial scheme with 3 replicates. In each shipment, 24 meat samples (one broiler chicken per sampled crate) were used in a total of 3 repetitions/ treatment. Statistical analysis. The collected data were subjected to analyses of variance using the general linear model procedure (PROC GLM) of the statistical analR ysis software SAS (v.9.3, Cary, NC) with subsequent comparisons of means using Tukey’s test (5% significance). Correlation among all meat quality variables (pH, L∗ , a∗ , b∗ , CL, and SF) was done using PROC CORR.
RESULTS The average temperature and relative humidity were 25.2 ◦ C and 67%, respectively, in the rainy season and 19 ◦ C and 44.2% in the dry season (Table 1).
Enthalpy Comfort Index The interaction (P < 0.0001; CV = 12.47%) between the season and distance factors showed that the rainy season ECI was significantly higher for long-distance loads (70.6 ± 6.5 kJ/kg; Figure 2A). In the dry season, higher ECI were noticed in short-distance loads (50.5 ± 4.5 kJ/kg). During the rainy season, even higher ECI were observed in long (70.6 kJ/kg) and shortdistance (57.9 ± 9.7 kJ/kg) loads.
Meat Characteristics There was interaction (P = 0.0097; CV = 2.69%) between the season and distance factors on the meat pHf values (24 h postmortem). Thus, higher values (Figure 2B) for this parameter in the rainy season (6.08 ± 0.20) were observed for the long-distance
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BROILER CHICKENS TRANSPORT AND MEAT QUALITY Table 2. Correlation between meat characteristic variables: initial pH (pHi ), final pH (pHf ), luminosity (L∗ ), redness (a∗ ), yellowness (b∗ ), water holding-capacity (WHC), cooking loss (CL), and shear force (kgf/cm2 ). Variables pHf L∗ a∗ b∗ WHC CL SF
pHi
pHf
L∗
a∗
b∗
WHC (%)
CL
−0.182∗∗ −0.052 ns −0.150∗∗ 0.063 ns 0.086 ns 0.043 ns 0.151∗∗
−0.268∗∗ 0.025 ns −0.124∗ −0.132∗ −0.115∗ −0.193∗∗
−0.016 ns 0.322∗∗ 0.051 ns 0.105 ns −0.038 ns
0.367∗∗ −0.130∗ 0.008 ns −0.134∗
0.303∗∗ 0.193∗∗ 0.205∗∗
0.570∗∗ 0.526∗∗
0.042∗∗
∗
P < 0,05. P < 0,01. ns = No significance. ∗∗
loads than that measured for the short-distance loads (5.94 ± 0.14). In the dry season, there was no significant difference between distances, with the final pH average of 5.93. For luminosity (L∗ ), the interaction (P = 0.01; CV = 6.23%) showed that in the rainy season there was a significantly higher mean for short-distance loads (44.37 ± 2.51) compared to long-distance loads (43.40 ± 2.27) (Figure 2C). In the dry season, no significant difference in the mean L∗ was observed between the distances (43.70). Between the rainy and dry seasons, trucks traveling long distances had the same L∗ values. However, trucks traveling short distances in the rainy season had a slightly higher mean L∗ value (44.37 ± 2.51) than in the dry season (43.68 ± 2.71). A pHf of 5.95 ± 0.14 (Figure 2B) and a 43.73 ± 3.04 ∗ L (Figure 2C) were observed for broiler meat in the dry season and in a long-distance load. For a short-distance load in the same season, the values were 5.91 ± 0.14 and 43.68 ± 2.71, respectively. In this study, a negative correlation was detected (r = −0.2677, P < 0.001; Table 2) between pHf and L∗ . The interaction (P < 0.0001; CV = 46.61%) between season and distance on a∗ (red content) showed a significant difference between distances in the rainy season (Figure 2D). The redness was higher in the long distance (3.42 ± 1.47) than in the short distance (2.54 ± 1.11). However, no difference was observed between distances in the dry season. The pHi (Figure 3D) in the dry season (6.72 ± 0.19) was significantly different (P < 0.0001; CV = 2.44%) from that measured in the rainy season (6.64 ± 0.13). A similar trend (P = 0.02) was observed when comparing short- and long-distance loads (Figure 4E), with a higher pHi in the short-distance load (6.71 ± 0.16 vs. 6.66 ± 0.17). In the dry season, the mean drip loss (2.66 ± 1.53%; CV = 17.30%) and CL (14.37 ± 2.71%; CV = 18.09%) were significantly higher (P < 0.0001) than those observed in the rainy season (2.07 ± 0.89% and 12.68 ± 2.17%, correspondingly) (Figure 3A and C, respectively). Higher drip losses (2.57 ± 1.36%; P < 0.0001) and CL (14.18 ± 2.69%; P = 0.005) were noted (Figure 4A and C) in the short-distance loads than in the longdistance loads (2.16 ± 1.17% and 12.86 ± 2.21%. re-
spectively). The CL was negatively correlated (r = −0.115, P < 0.05; Table 2) with pHf , which may have explained the CL. A higher breast muscle SF (P < 0.0001; CV = 29.90%) was observed in broilers transported in the dry season (2.06 ± 0.60 kgf/cm2 ) than in the rainy season (1.75 ± 0.54 kgf/cm2 ; Figure 3B). The meat from the dry season had higher drip and CL, which resulted in decreased degrees of meat tenderness. Conversely, the different distances tested showed no significant SF difference, with average of 1.90 kgf/cm2 . However, the highest muscle water loss was observed when studying the short-distance loads (2.04 ± 0.48 kgf/cm2 ). No significant difference in b∗ values (yellow-blue content) was observed between seasons, whereas a higher b∗ content (P = 0.0003; CV = 43.22%) was recorded in the short-distance loads (3.47 ± 1.09) than in the long-distance loads (2.90 ± 1.65; Figure 4D). No crate position effects were observed on meat characteristics.
DISCUSSION The ECI indicates the degree of comfort provided to animals in a specific rearing environment. During the rainy season, although no broiler deaths were recorded due to transport, the ECI of long-distance loads (70.6 kJ/kg) can be considered lethal, as they were beyond the limits of the comfort zone for broilers over 6 wk old, according to Queiroz et al. (2012). In the same way, during the rainy season, the short-distance loads had a 57.9 kJ/kg ECI and could be classified as within the critical zone. On the other hand, during the dry season, the ECI for long- (46.9 kJ/kg) and short(50.5 kJ/kg) distance loads were in the comfort and warning zones, respectively. Transport operations in the rainy season and longdistance loads (90 km) resulted in a high ECI (70.6 kJ/kg). High temperatures (31.1 ± 3.4◦ C) and the relative humidity (65.4 ± 2.7%) inside the cargo contributed to the high ECI. Increased poultry respiratory activity contributed toward heat loss to the environment and also likely contributed to the increased temperatures and relative humidity inside the loads. The comfort zone of broilers, from the sixth wk of age, reportedly ranges from 21 to 23◦ C and from 60 to 70%
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Figure 3. (A) Relationship of initial pH, (B) drip loss (DRIP; %), (C) cooking loss (CL; %), and (D) shear force (SF; kgf/cm2 ) of the Pectoralis major muscle with season.
relative humidity (Furlan and Macari, 2002). In adverse environments, heat exchange through panting is impaired, resulting in heat stress. Conversely, in the dry season, an improved ECI was observed for long-distance loads (46.9 kJ/kg) when compared with short-distance loads (50.5 kJ/kg). The low relative humidity (44.2%; Table 1) in the dry season may favor poultry heat exchange with the environment. Wind also may help with heat dissipation from the poultry body to the environment, especially for longer distances traveled; wind may enable the animals to arrive under better conditions (P´erez et al., 2002). Conversely, short-distance transports were unlikely to decrease the poultry body temperature to homeostasis (Vosmerova et al., 2010). Increased poultry body temperature is a result of stress caused during catching management, crate stacking in the truck body (Queiroz et al., 2015), and subsequent transport. Air conditioning systems in poultry sheds may facilitate poultry heat loss during the catching and caging stages, thereby decreasing panting and body temperature before transport. For loads carried during the rainy season for long distances, the pHf and L∗ values were 6.08 (Fig-
ure 2B) and 43.40 (Figure 2C), respectively, and then the broiler meats were classified as DFD (Qiao et al., 2001; Oda et al., 2003). Conversely, when transported for short distances in the rainy season, the meats had a pH of 5.94 and an L∗ value of 44.37, typical of normal meat. Based on those results, the transport distance had a key effect on the final quality, causing significant changes in the breast muscles of broilers. The combination of rainy season and long-distance loads tended to develop meat with DFD characteristics. DFD meat is typically associated with long periods of stress before slaughter, beginning of catching and crate stacking, and remaining during transport (Ristic and Damme, 2013). In this study, for the rainy season and long-distance loads, the poultry were exposed to high temperatures and relative humidity, hindering poultry body heat loss by evaporation. The energy expenditure with panting reduces muscle glycogen reserves, which further worsens during prolonged travel. Therefore, after slaughter, the muscle pH increases due to the lack energy for lactic acid production, resulting in DFD meat (Scheffler et al., 2011; Barbut, 2014).
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Figure 4. (A) Relationship of initial pH, (B) drip loss (DRIP; %), (C) cooking loss (CL, %), (D) shear force (SF; kgf/cm2 ), and (E) yellow content of the Pectoralis major muscle with distance.
Due to altered colorations in DFD quality meat, marketed poultry breast meat is often discarded or considered unfit for consumption (BRASIL, 1998). Consumers avoid purchasing this meat (Rosa et al., 2016) because they tend to prefer meat with a natural appearance, with a pH and color within normal classification parameters (Viljoen et al., 2002). Furthermore, the biochemical changes in DFD quality meat may pose a risk to human health. The high final pH favors bacterial growth, which compromises its shelf life and food safety. Such microbiologically unstable meats must be quickly subjected to heat treatment and used to prepare industrial by-products (Lesi´ ow and Kijowski, 2003). Broilers transported in the dry season had normal standard meat in long- and short-distance loads. The pHf values were within the normal classification range
from 5.70 to 6.00 (Qiao et al., 2001; Oda et al., 2003), and the L∗ values were numerically close to the lower limit (44.0) of the same classification. Therefore, results suggest that broiler transport in the dry season, for both distances, was less critical in terms of changes in meat quality (pHf and L∗ ). According to Qiao et al. (2001), the limits for detecting changes in broiler breast muscles have not yet been well established. Thus, the L∗ value may still be considered a good indicator to classify meat quality deviations. However, a combined analysis of both variables (pHf and L∗ ) may render a safer evaluation, as both parameters may change during the industrial processing, either by excessive scalding or by cooling in the chiller despite a low correlation (Barbut, 2014; Bowker et al., 2014).
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The CIE L∗ a∗ b∗ (or Hunter) system defines a∗ and b values to measure red or green and yellow or blue reflectance, respectively. These values corroborated the pHf and L∗ results observed in this study. DFD meat, as observed in the rainy season and long-distance loads, may have higher a∗ values, suggesting that the meat has a more intense red color and retains more water with increased pH (Zapata et al., 2006). The higher redness intensity in DFD meat is due to the higher concentration and rapid oxidation of muscle hemoglobin under higher pH (Boulianne and King, 1998). Despite the slight numerical difference in pHi values, these values are close to 7.0, the physiological pH of muscle according to Lawrie (1998), and thus considered normal for broiler muscle tissue after slaughter. The difference between mean drip loss and CL indicated that the meat of the poultry transported in the dry season had a lower WHC when baked, given the higher muscle water loss. The short-distance transport resulted in higher water losses from the meat after cooking, increasing by approximately 1.32%. The formation of exudate occurred due to the postmortem shrinkage of myofibrils in reduced muscle pH, and this contributes to decreasing the quality in processed meat products (Jensen et al., 1998). Water loss can be used to assess WHC because poultry meat with decreased WHC has been associated with high CL (Northcutt et al., 1994). During 30-minute summer transport loads of broiler chickens, Xing et al. (2016) observed a 15.59% CL and a 13.41% decrease for a pre-slaughter 10-minute water shower spray on meat quality. In regard to our outcomes, short distance presented a similar CL value (14.18 ± 2.69%), and the time of transport to the slaughterhouse was 42 min, on average. However, the dry season resulted in a 14.37 ± 2.71% loss, 1.70% higher than that in the rainy season, which may account for the recommendation to use a water shower spray before poultry transport in the dry season. The inverse relationship between pHf and CL indicates that as the pHf of meat decreased, the CL increased (Caldara et al., 2012). The more acidic pH on meat, the more denatured muscle proteins, which subsequently impaired ability to retain water due to structural changes and higher water drips at the muscle surface (Zhang and Barbut, 2005). The pHf values measured in the dry season (5.93) and for short-distance loads (5.92) were slightly lower than those observed in the rainy season (6.01) and for long-distance loads (6.02). However, the pH values may have caused higher CL. The SF ranged from 4.51 to 6.97 kgf/cm2 in various chicken breast samples sheared with cuts perpendicular to the muscle fiber and at a final cooking temperature of 70 ◦ C, as recommended by Wheeler et al. (1996). These authors also report difficulties in comparing the SF values among research studies due to different analysis methods used. The SF of broiler breast muscles aged for 24 h before freezing ranged from 2.37 to 2.43 kgf/cm2 according to Thielke et al. (2005). ∗
Conversely, Komiyama et al. (2010) measured an average of 4.94 kgf/cm2 , claiming this meat to be slightly less tender than chicken meat. Therefore, the results from this study did not indicate significant differences in meat tenderness for the long- and short-distance loads, with an overall average SF of 1.90 kgf/cm2 . Enzyme activity during the meat maturation process may be correlated with the SF. The activity of enzymes, including cathepsins and calpains, in postmortem proteolysis contributed to the weakening of the muscle fibers and improvements in the meat texture (Barbut, 2014). Furthermore, the aging period and meat preservation method established in this study, i.e., 24 h of cooling to 2 to 5◦ C, may have contributed to the activity of those enzymes, resulting in meat with better tenderness (Zapata et al., 2006). Meat tenderness may be considered one of the most important factors attributed to consumer acceptance (Hong and Lee, 2012). Furthermore, meat texture may contribute toward the assessment of pre- and postslaughter management conditions because both field and postmortem stages may affect variables linked to meat quality. Considering b∗ value results, PSE meat has a more acidic pH and higher yellow component intensity (b∗ ) due to its pale color (Warriss, 2010). In relation to crate position, few studies have reported significant correlations between truck body areas of highest thermal discomfort and incidence of meat quality deviations. When analyzing microenvironment effects on the occurrence of PSE and DFD meat in broilers, Langer et al. (2010) observed that the rear of the vehicle, which has the highest temperature and relative humidity, resulted in a higher percentage of PSE meat. This incidence decreased in broilers located upon moving from the middle to the front of the cargo bay. Concluding, in the rainy season, the transport distance caused significant changes in meat quality. The highest ECIs were recorded for the long-distance loads, suggesting DFD meat with decreased water losses from cooking. Conversely, the dry season had lower ECIs during transport, which was better in terms of poultry comfort. Broilers transported and slaughtered in that season had meat with pH and L∗ values classified as normal and with high CL and drip losses. The CL observed (14.37%) was inherent in the cooking process and was within the normal range of loss. The season and distance factors had no significant effects on the SF tenderness of the meat. The crate position in the truck had no effects on pH, L∗ , CL, or SF. These results show that distance and season, rather than crate location, had stronger effects on the quality of broiler meat.
ACKNOWLEDGMENTS The authors thank Bonasa Alimentos S.A (Bras´ılia, Brazil) for making this study possible.
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APPENDIX Abbreviations: a∗ : Red content (redness) b∗ : Yellow content (yellowness) CL: Cooking loss DFD: Dark, firm and dry
ECI Enthalpy comfort index L∗ : Luminosity pHi : Initial pH (15 min postmortem) pHf : Final pH (24 h postmortem) PSE: Pale, soft and exudative SF: Shear force WHC: Water-holding capacity