The Effects of Residual Blood of Carcasses on Poultry Technological Quality ()
1. Introduction
The objective of this work is to show the effect of residual blood on the quality of chicken meat, when cattle are slaughtered, up 4.5% of body weight is removed with bleeding [1,2]. Even with effective bleeding only 50% of whole blood is removed. The different muscles preserve the blood more or less depending on their nature [3]. Chickens are losing between 35% and 50% of total body blood during the bleeding phase [4]. 60% of total blood volume is lost during bleeding of animals and from 20% to 25% in the viscera and the remaining 15% to 20% remaining in the bones and not more than 10% remains in the muscles [5].
This residual blood in the carcass is often associated with a meaty flavour and decreased shelf life [6]. Therefore excessive haemorrhaging caused by different stunning and slaughter techniques can increase haemoglobin content in the muscle that can decrease shelf life by increasing oxidation [6].
As the water retention capacity of the pectoral muscle and thigh significantly increased with the pH of the meat (Dunn et al., 1993 [7], Cornforth, 1994 [8,9] Northcutt et al., 1994 and [10] Allen et al., 1997 in chicken; [11] Barbut & Mittal, 1993 in turkey): the case of meat Imperfectly grooves that have a high pH and high losses of technological quality parameters with significant correlations in accordance with work (Barbut, 1993 and 1996 [12]; Fletcher, 1999 [13]; Van Laack et al., 2000 [14]).
From these observations postulated by different authors, we formulated our hypothesis, based on the fact that the presence of residual blood in the carcasses would result in an increase of microorganisms and pH in carcasses imperfectly bled over carcasses perfectly bleeding leading to quality degradation. The work is based on the assumption that increasing the concentration of residual blood would explain the quality degradation observed by several authors [15-17,19,23].
2. Materials and Methods
2.1. Choice of Chicken as Material
The study uses poultry as biological material. The number of the muscle samples of chicken carcasses from the group designated for analysis of pH is 220; the number of the muscle samples of chicken carcasses from the group designated for analysis of color is 100.
2.2. Conditions of Pre-Slaughter and Slaughter
The carcasses used to derive lots having lived the same characteristics and conditions before and after slaughter to prevent the intervention of some intrinsic factors (muscle metabolic type of the animal, genetics, age, race, sex, eating habits, etc.) and extrinsic (type of farming, housing, treatment ante-mortem handling by the farmer etc.) and other physic-chemical factors such as temperature, oxygen availability, mode of storage, and the type of lighting.
2.3. Description of the Method of Slaughter
Lots of chickens are slaughtered in two different ways: first, slaughter without stunning for a maximum discharge of blood, that is perfectly bled (PB) is done through an incision in the neck by hand and involves using a sharp knife to make a profound and rapid incision from the front of the throat, which at the same time cutting the carotid arteries, the trachea and jugular veins, but leaves spinal cord intact. Issued a funnel of bleeding, and plucked as soon as the animals have stopped moving. This allows a large evacuation bleeding blood.
However the second method of slaughter that we used is to kill chickens derived from lead ball on the head of the bird using a rifle with small ball of lead; this second method only allows the evacuation of very small amount of blood. The discharge of blood is done automatically without any experimental protocol.
The plucking is made by soaking the chicken in a bowl with hot water (about 50˚C).
2.4. Data Analysis
Data were statistically analysed using means and standard error of means, the effects of residual blood of carcasses on pHu was determined by student t-test and correlation coefficient matrix of meat quality by Pearson coefficient correlation, all analysis was performed by using SYSTAT 10.2.
Version 7600.LSD values at P < 0.01 were obtained for comparison of mean values [16].
2.4.1. Colorimetric Analyses
In the first experiment (n = 100, 50 per treatment) samples are used to study the effect of residual blood on the color (P < 0.1), according to the experimental plan Table 1.
Poultry colour is determined with Minolta CR 300. The Instrumental is set to measure CIE LAB* colour values that represent lightness (L*), redness (A*), and yellowness (B*). All measurements are carried out on the surface of the scallop, in an area free of obvious colour defects (over scalding, bruises, blood spots, and haemorrhages), and are often used to determine breast meat quality [19].
2.4.2. Analysis of pHu
In the second (n = 260, 130 per treatment) samples are used to study this effect on pHu, according to two experimental designs (Table 2).
2.5. Measurement Site
The pH measurement is made inside the muscles of the chest and thigh to reflect the heterogeneity of the pHu carcasses. We evaluated the effects of residual blood of carcasses on the technological quality (pHu) meat by four experiments. These experiments are based on treatment formulated in terms of method of slaughter. We performed each experiment with meat perfectly bled and bled meat imperfectly. The carcasses are stored at 3˚C or 7˚C before each measurement.
In the first experiment, before evaluation, the samples were stored at 3˚C; we evaluated the growth of pHu of the perfectly bled poultry with the imperfectly bled one, for the comparison between the changes of pHu in the two substrates.
In the second experiment, we realized the same comparison but the samples were stored at 7˚C. Increases in the average summer pHu led us to see the effect of season on the results, that’s why we made the same comparisons in the summer (Experiment 3, and Experiment 4). In the 4th experiment we increase the number of sample to 100 to see the influence of the change in the number of samples, according to experimental plan (Table 2).
pH measurements are made by pH meter HI 99163;
Table 1. Experimental general plan.
Table 2. Analysis of pHu experimental general plan.
Portable pH probe with penetration/temperature was used to measure the pH of 260 samples of carcasses by inserting depth of the muscle approximately 2.5 cm, at 24 h post-mortem.
3. Results and Discussion
3.1. Colorimetric Analyses
The effect of residual blood of carcasses on colour is reported in (Table 3). The samples that are imperfectly bled show a high value of A* = 12.68; and B* = 16.85; with a pale colour L* (54.09).
The results of excessive bleeding caused by different stunning techniques and by imperfect slaughter increase the haemoglobin concentration in the muscle and decrease the organoleptic quality. The increase in red and yellow colour causes the pink colouration which is due to the imperfectly bleeding and which may lead to a downgrading of the carcasses. Samples from imperfectly bled carcasses also show a high value of L* (54.09) which produce a pale colour. These results are consistent with the observations of many authors [6,20-23] in addition to biological factors reported by several authors [23-26] (genetic type of chicken) and the evolution time postmortem [27], the amount of residual blood is among the key factors affecting the quality of the poultry colour. Bruises, hemorrhages, and poor exsanguination efficiency can negatively affect colour of the meat and skin; these are major quality defects and are associated with undesirable discoloration and reduced shelf life [6].
3.2. Analysis of pHu
The effect of residual blood of carcasses on pHu is reported in (Table 4). At 3˚C storage temperature, the average pHu of perfectly bled poultry was (5.7) which was significantly (P < 0.01) lower than the average pHu of imperfectly bled poultry (6.08).
According to the work of (Gigaud V. et al., 2010) [28], variability of pH standards for meat chickens are between 5.7 to 6.20 (Figure 1). Normal values of ultimate pH ranged from 5.7 as minimum normal value and 6.25 as maximum normal value (Gigaud V., et al., 2010) [28], outside this range, and lower values to 5.7 meats have
Figure 1. The variability standards pHu (Gigaud V. et al., 2010); DFD: dark, firm and dry.
defects and are called PSE (pale, soft, exudative), for higher values to 6.25 meats have defects and are called DFD (dark, firm and dry) .
At 7˚C storage temperature, the average pHu of perfectly bled poultry was (6.07) which was significantly (P < 0.05) lower than the average pHu of imperfectly bled one (6.27).
Effect of Season on meat quality: the values for pHu were significantly (P < 0.01) higher in summer than winter in two types of slaughter (perfectly bled: PB and imperfectly bled: IB) (Table 4).
These experimental results confirm the observations and assumptions made by some authors. [19,23]. A rise in the storage temperature increases the pHu in the two types of poultry. But the pHu of the perfectly bled meat is still minimal. The comparison of the results (Table 2) shows not only the strong relationship between carcass residual blood and the growth of the degree of pHu, but also indicates the season effect. The lowest level of pHu is recorded during the winter. After this period the values increase to reach the highest rate in the summer, especially at 7˚C storage.
4. Conclusions
After determining the quality of chicken meat by analysing the colour of different lots of chickens slaughtered at two different levels: perfect slaughter without stunning
Table 3. Descriptive statistics of poultry colour with paired samples t test.
Table 4. The effects of residual blood of carcasses on pHu, results with paired samples t test.
for a maximum discharge of blood and imperfect bleeding to keep most of the blood in the carcass. In accordance with the observations of several authors, we can see that these two tests can show a difference between the quality of the colour of perfectly bled poultry and that of imperfectly bled one.
Residual blood in poultry carcasses is responsible for high values of the colour parameters (L* A* B*) compared with the perfectly bled samples and therefore the deterioration of the quality of poultry.
This justifies that excessive bleeding caused by different techniques of stunning and non-perfect slaughtering increase haemoglobin, and increases the pHu level of carcasses especially in case of increasing the storage temperature and in the hot season. Reducing the pHu level of carcasses would be absolutely possible by applying good slaughter practices without stunning and with storage below.
Carcasses with less residual blood have lower values of the colour parameters (L* A* B*) and lower values of the pHu compared with the imperfectly bled samples and therefore a better quality.
NOTES