Massimiliano Petracci

Muscle growth and poultry meat quality issues.

Over the past 50 years the worldwide growing demand of poultry meat has resulted in pressure on breeders, nutritionists and growers to increase the growth rate of birds, feed efficiency, size of breast muscle and reduction in abdominal fatness. Moreover, the shift toward further processed products has emphasized the necessity for higher standards in poultry meat to improve sensory characteristics and functional properties. It is believed that genetic progress has put more stress on the growing bird and it has resulted in histological and biochemical modifications of the muscle tissue by impairing some meat quality traits. The most current poultry meat quality concerns are associated with deep pectoral muscle disease and white striping which impair product appearance, and increased occurrence of problems related with the meat’s poor ability to hold water during processing and storage (PSE-like condition) as well as poor toughness and cohesiveness related to immaturity of intramuscular connective tissue. This paper is aimed at making a general statement of recent studies focusing on the relationship between muscle growth and meat quality issues in poultry.

Meat quality in fast-growing broiler chickens

During the past few decades there has been a notable increase in the demand for poultry meat due to its low cost, good nutritional profile and suitability for further processing. Moreover, current forecasts and projection studies have predicted that the expansion of the poultry market will continue in the future. This growing demand has led to progressive improvements in genetic selection to produce fast-growing broilers, inducing the appearance of several spontaneous, idiopathic muscle abnormalities along with an increased susceptibility to stress-induced myopathy. Such muscle abnormalities have several implications for the quality of fresh and processed products, as breast meat that is affected by deep pectoral myopathy is usually rejected due to its unacceptable appearance. In addition, pale, soft and exudative like meat has a low processing ability due to its reduced water holding capacity, soft texture and pale colour. Finally, the high incidence of abnormalities observed in chicken breast muscles such as white striping (characterised by superficial white striations) and wooden breast (characterised by pale and bulging areas of substantial hardness) impair both the appearance and technological traits of breast meat. This review evaluates the consequences of genetic selection on muscle traits and describes the relevance of major breast abnormalities on nutritional, technological, sensorial and microbial characteristics of raw and processed meat.

Implications of white striping and wooden breast abnormalities on quality traits of raw and marinated chicken meat

One of the consequences of intense genetic selection for growth of poultry is the recent appearance of abnormalities in chicken breast muscles, such as white striping (characterised by superficial white striations) and wooden breast (characterised by pale and bulged areas with substantial hardness). The aim of this study was to evaluate the quality traits of chicken fillets affected by white striping and wooden breast abnormalities. In two replications, 192 fillets were divided into the following four classes: normal (n=48; absence of any visual defects), white striping (n=48, presence of white striations), wooden breast (n=48; diffusely presence of hardened areas) and white striping/wooden breast (n=48; fillets affected by both abnormalities). Morphology, raw meat texture and technological properties were assessed in both unprocessed (pH, colour, drip loss, cooking loss and cooked meat shear force) and marinated meat (marinade uptake, purge loss, cooking loss and cooked meat shear force). Fillets affected by white striping, wooden breast or both abnormalities exhibited higher breast weights compared with normal fillets (305.5, 298.7, 318.3 and 244.7 g, respectively; P<0.001). Wooden breast, either alone or in combination with white striping, was associated with a significant (P<0.001) increase of fillet thickness in the caudal area and raw meat hardness compared with both normal and the white striping abnormality, for which there was no difference. Overall, the occurrence of the individual and combined white striping and wooden breast abnormalities resulted in substantial reduction in the quality of breast meat, although these abnormalities are associated with distinct characteristics. Wooden breast fillets showed lower marinade uptake and higher cooking losses than white-striped fillets for both unprocessed and marinated meats. On the other hand, white-striped fillets showed a moderate decline in marinade and cooking yield. Fillets affected by both abnormalities had the highest (P<0.001) ultimate pH values. In contrast, the effects on colour of raw and cooked meat, drip loss, purge loss and cooked meat shear force were negligible or relatively low and of little practical importance. Thus, the presence of white striping and wooden breast abnormalities impair not only breast meat appearance but also the quality of both raw and marinated meats mainly by reducing water holding/binding abilities.

Occurrence of white striping under commercial conditions and its impact on breast meat quality in broiler chickens

The aims of this study were to evaluate the incidence of white striping (WS) under commercial conditions and assess its effect on some quality traits in broiler breast fillets. In the first experiment, occurrence of WS (absence = normal; presence classified in 2 levels as moderate or severe) was assessed in a major commercial processing plant on 28,000 breast fillets (pectoralis major muscles) chosen at random from 56 flocks of broilers processed at 45 to 54 d of age. In the second experiment, 153 fillets were selected based on WS degree (normal, moderate, or severe) and used to assess ultimate pH, color, drip loss, cook loss, and Allo-Kramer-shear force on raw meat as well to determine marinade uptake, purge loss, cook loss, total yield, and Allo-Kramer-shear force after tumbling with a 15% (wt/wt) solution containing sodium tripolyphosphate (2.3%) and sodium chloride (7.6%). The total incidence of white striped breast fillets was 12.0% (8.9 and 3.1% in moderate and severe degree, respectively). Considering the effect of genotype, high-breast yield hybrids exhibited a higher overall incidence of WS compared with standard breast yield birds (15.2 vs. 10.0%; P ≤ 0.001). Severe fillets showed higher pH than moderate and normal groups (5.95 vs. 5.88 and 5.86; P ≤ 0.05). Fillets with severe and moderate WS also exhibited lower marinade uptake compared with normal fillets (7.92 vs. 10.97 vs. 12.67%; P ≤ 0.05). Moreover, cook losses increased as the degree of WS increased from normal to severe groups in both raw (21.27 vs. 23.20 vs. 26.74%; P ≤ 0.05) and marinated meat (14.59 and 14.84 vs. 15.93%; P ≤ 0.05). Finally, nonmarinated fillets with severe striping had lower Allo-Kramer-shear force compared with moderate and normal ones (3.69 vs. 4.41 and 4.91 kg/g; P ≤ 0.05). In conclusion, this study revealed the importance achieved by WS defects in the production of broiler meat as well as its very negative impact on water holding and binding capacity of breast meat.

The European perspective on pale, soft, exudative conditions in poultry

Over the past 15 yr, the European poultry processing industry has gradually increased the availability of poultry meat in a large variety of processed ready meals following what occurred a few years before in North America. This shift toward further processed products has emphasized the necessity for higher standards in poultry meat to improve sensory characteristics and functional properties. In parallel to this market change, the consciousness of the pale, soft, and exudative (PSE)-like meat issue has extensively grown. In poultry, PSE-like meat can be generally considered meat having low ultimate pH, pale color, and poor functional properties (i.e., low water-holding capacity). In the last 10 yr, some studies have been undertaken in Europe to both characterize and evaluate the overall incidence of PSE-like chicken and turkey breast meat. According to these studies, the occurrence of PSE-like meat can be up to 40% within a flock during hot climate. Several key factors have been identified and their effects have been analyzed, including genetics, season, antemortem factors, and slaughtering conditions.

Advances in research on poultry and rabbit meat quality

Abstract – Main force and weakness points of poultry and rabbit production chains are presented and meat quality discussed in relation to nutritional and technological issues. An analysis of the most important poultry and rabbit meat quality traits and their major relationships with production factors (genotype, feeding, housing, pre-slaughter handling, slaughtering, and processing) is provided. Most recent research advancements are presented in view of the consumer’s demand for healthy and safe products obtained respecting animal welfare.

Histology, composition, and quality traits of chicken Pectoralis major muscle affected by wooden breast abnormality

Only a few years ago, the poultry industry began to face a recent abnormality in breast meat, known as wooden breast, which frequently overlaps with white striping. This study aimed to assess the impact of wooden breast abnormality on quality traits of meat. For this purpose, 32 normal (NRM), 32 wooden (WB), and 32 wooden and white-striped (WB/WS) Pectoralis major muscles were selected from the same flock of heavy broilers (males, Ross 708, weighing around 3.7 kg) in the deboning area of a commercial processing plant at 3 h postmortem and used to assess histology, proximate (moisture, protein, fat, ash, and collagen) and mineral composition (Mg, K, P, Na and Ca), sarcoplasmic and myofibrillar protein patterns, and technological traits of breast meat. Compared to the normal group, WB/WS fillets showed more severe histological lesions characterized by fiber degeneration, fibrosis, and lipidosis, coupled with a significantly harder texture. With regard to proximate and mineral composition, abnormal samples exhibited significantly (P < 0.001) higher moisture, fat, and collagen contents coupled with lower (P < 0.001) amounts of protein and ash. Furthermore, increased calcium (131 vs. 84 mg kg(-1); P < 0.05) and sodium (741 vs. 393 mg kg(-1); P < 0.001) levels were found in WB/WS meat samples. The SDS-PAGE analysis revealed a significantly lower amount of calcium-ATPase (SERCA, 114 kDa), responsible for the translocation of Ca ions across the membrane, in normal breasts compared to abnormal ones. As for meat quality traits, fillets affected by wooden abnormality exhibited significantly (P < 0.001) higher ultimate pH and lower water-holding/water-binding capacity. In particular, compared to normal, abnormal samples showed reduced marinade uptake coupled with increased drip loss and cooking losses as well. In conclusion, this study revealed that meat affected by wooden breast or both wooden breast and white striping abnormalities exhibit poorer nutritional value, harder texture, and impaired water-holding capacity.

Effect of fast-, medium- and slow-growing strains on meat quality of chickens reared under the organic farming method

The characteristics of meat quality, chemical and fatty acid composition, from fast-growing (FG) and medium-growing (MG) meat-type and slow-growing (SG) egg-type chickens reared under organic conditions were compared. Three-hundred and sixty 1-day-old male chicks, equally divided into three experimental groups represented by strains (FG: Cobb 700, MG: Naked neck Kabir and SG: Brown Classic Lohman) were housed into three poultry houses with outdoor pasture availability of 10 m(2)/bird located in the same Research Centre of the University of Perugia. All the birds were fed ad libitum the same diets formulated according to the European Union (EU) Regulations by using organic raw materials. Birds from the FG and MG groups were raised until 81 days, whereas birds from the SG group were raised until 96 days in order to achieve an acceptable market live weight. SG birds showed significantly (P < 0.01) higher breast meat drip and cook losses, Allo-Kramer shear values and collagen content. In comparison with FG and SG, MG exhibited a higher breast meat pH (5.86% v. 5.79% and 5.78%, respectively; P < 0.01) and a lower lightness (54.88% v. 57.81% and 56.98%, respectively; P < 0.05). Genotype dramatically affected the lipid content as well as the fatty acid composition of both breast and thigh meat. SG exhibited the lowest content of lipid, both in breast and in thigh meat, the lowest proportions of monounsaturated fatty acids (MUFA) and the highest proportions of polyunsaturated fatty acids (PUFA). The total n-3 PUFA of SG breast meat was double that of FG meat and intermediate with respect to MG birds (8.07% v. 4.07% v. 5.14% total fatty acids; P < 0.01). The fatty acid composition of thigh meat is similar to that of breast meat, but the differences among genotypes are less pronounced. Total saturated fatty acids were not affected by the genotype. In conclusion, meat functional properties of FG and MG strains appeared much more attractive both for industry and consumer (lower drip and cook losses and higher tenderness), whereas from a nutritional point of view, meat from SG appeared healthier (less fat and higher content of n-3 PUFA) and thus might better fit with the consumers expectations of organic products.

Relationship between pectoralis major muscle histology and quality traits of chicken meat

A trial was conducted to evaluate the influence of myodegeneration of pectoralis major muscle on quality traits and chemical composition of breast meat of heavy-size male broilers. For this purpose, a total of 72 pectoralis major muscles were randomly collected from broilers farmed under homogeneous conditions and graded into three categories (mild, n=22; moderate, n=33; and severe, n=17) based on the presence of abnormal fibers (giant fibers, fibers with hyaline degeneration, and damaged and/or necrotic fibers) evaluated by histological and immunohistochemical analysis. Color, pH, drip loss, Allo-Kramer shear values, and chemical composition (moisture, proteins, total lipids, ashes, and collagen) were determined on nonmarinated breast meat. Purge loss and cook loss, total yield, and Allo-Kramer shear values were measured on vacuum-tumbled samples. Samples showing moderate myodegeneration had the highest mean cross-sectional area of the fibers, while samples with severe myodegeneration had myofibers of different diameter and without the characteristic polygonal shape, multifocal degeneration and necrosis, as well as infiltration of CD3-immunoreactive cells. Cooking losses of nonmarinated meat were lower in the mild group with respect to moderate and severe groups (21.4 vs. 24.7 and 24.7%; P<0.001). Breast muscles with severe damage, in comparison with mild degenerated samples, showed higher moisture (75.4 vs. 74.4%; P<0.05) and lower protein percentages (21.1 vs. 22.6%; P<0.001). The lipid percentage of severely degenerated samples was higher than that from moderate group (2.94 vs. 2.36; P<0.05), while collagen content was not modified by histological lesion levels. Marinated meat from the mild group had higher uptake and total marinade yield after cooking. In conclusion, almost all breast fillets of heavy broiler chickens produced under intensive farming systems had histological lesions, which reflected on the chemical composition of the meat and the impaired water holding/binding capacities of the meat.

Quantity and functionality of protein fractions in chicken breast fillets affected by white striping

Recently, white striations parallel to muscle fibers direction have been observed on the surface of chicken breast, which could be ascribed to intensive growth selection. The aim of this study was to evaluate the effect of white striping on chemical composition with special emphasis on myofibrillar and sarcoplasmic protein fractions that are relevant to the processing features of chicken breast meat. During this study, a total of 12 pectoralis major muscles from both normal and white striped fillets were used to evaluate chemical composition, protein solubility (sarcoplasmic, myofibrillar, and total protein solubility), protein quantity (sarcoplasmic, myofibrillar, and stromal proteins), water holding capacity, and protein profile by SDS-PAGE analysis. White-striped fillets exhibited a higher percentage of moisture (75.4 vs. 73.8%; P < 0.01), intramuscular fat (2.15 vs. 0.98%; P < 0.01), and collagen (1.36 vs. 1.22%; P < 0.01), and lower content of protein (18.7 vs. 22.8%; P < 0.01) and ash (1.14 vs. 1.34%; P < 0.01), in comparison with normal fillets. There was a great decline in myofibrillar (14.0 vs. 8.7%; P < 0.01) and sarcoplasmic (3.2 vs. 2.6%; P < 0.01) content and solubility as well as an increase in cooking loss (33.7 vs. 27.4%; P < 0.05) due to white striping defects. Moreover, gel electrophoresis showed that the concentration of 3 myofibrillar proteins corresponding to actin (42 kDa); LC1, slow-twitch light chain myosin (27.5 kDa); and LC3, fast-twitch light chain myosin (16 kDa), and almost all sarcoplasmic proteins were lower than normal. In conclusion, the findings of this study revealed that chicken breast meat with white striping defect had different chemical composition (more fat and less protein) and protein quality and quantity (low content of myofibrillar proteins and high content of stromal proteins) with respect to normal meat. Furthermore, white striped fillets had lower protein functionality (higher cooking loss). All the former changes indicate that white striping has great impact on quality characteristics of chicken breast meat.