A COMPARATIVE ANALYSIS OF A QUALITY AND UTILITY OF LL AND BF MUSCLES OF PORKERS OF DIFFERENT GENOTYPE TO MASSAGED PRODUCTS

Małgorzata Sobczak¹, Kazimierz Lachowicz², Joanna Żochowska-Kujawska², Leszek Gajowiecki³, Andrzej Klemke^4
1 Department of Meat Technology, Faculty of Food Technology and Fisheries,
West Pomeranian University of Technology, Szczecin, Poland
² Department of Meat Technology, West Pomeranian University of Technology, Szczecin, Poland
³ Department of Meat Technology, Agricultural University of Szczecin, Poland
⁴ Department of Meat Technology, Faculty of Food Sciences and Fisheries, Agricultural University of Szczecin, Poland

ABSTRACT

Structure, texture and rheological properties of LL and BF muscles of porkers of different genotype (PLW×PL) × (L990×Pi) oraz (PLW×PL) × (D×Pi) were compared. No significant differences (P>0.05) in structural elements, texture parameters and utility to massaged products of muscles between compared groups of animals were found. Higher differences in parameters tested was found between muscles within an each group of porkers. Of the muscles tested, the lower values of shear and compression forces as well as the lower viscous and elasticity modules were found in LL, which at the same time was a muscle with the fibres with the lower cross sectional area and thinner connective tissue than BF. Muscles with the most delicate histological structure were more useful to massaged because of their higher structural and textural parameters changes during massaging.

Key words: muscles, porks, structure, texture, massaging.

INTRODUCTION

In meat industry massaging, due to mechanical effects on brine-injected meat, is the one of the widely known ways of massaged meat production. As a result of chemical (brine components) and mechanical interaction, massaging causes some muscle histological changes [20, 24, 26, 32]. As a result of damaging muscle fibres, massaging causes an increase in brine sorption and myofibrils and muscle fibres swelling at the same time [4, 7, 17, 28]. The consequences include, i.a., an increase in meat juiciness and tenderness as well as a decrease in meat hardness and thermal drip losses [12, 13, 21, 26, 28, 24]. Final effects of massaging is connected with the both raw material and with the massaging parameters. The muscles were shown to differ in their susceptibility to tenderization [12, 13, 17, 24]. The differences in susceptibility to massaging could be probably connected with the differences in muscle structure elements [5, 11, 15, 16]. One of the reason of differentiation of structure elements of muscles could be the i.a., origin of raw material. In organism some different function were served by muscle so they were differ in both a chemical composition and histology [14, 23]. A hard working muscles (e.g. leg muscles) compared to muscles saddled with lower work (e.g. lumbar muscle), were characterized by higher amount and thicker connective tissue as well as fibres with bigger cross sectional area. It is widely known, that the some muscles from animals of different ages or genotypes were shown to differ in their structure [3, 22, 24, 30, 33, 34], and it can be thus assumed that the muscles will also to differ in their susceptibility to tenderization.

AIM OF THE STUDY

The study presented here was aimed at comparing selected muscles of two groups of cross-bred porkers in terms of their texture, structure and thermal drip losses as well as the utility to massaged products.

MATERIAL AND METHODS

Animals and meat samples

The study involved 2 groups of porkers from Experimental Institute of Animal Husbandry of Kołbacz and 20 animals of each group were examined (10 sows and 10 barrows). The porkers were crossbreds of Polish Large White and ×Polish Landrace (PLW×PL) sows and boars from crossing between porkers line 990 (L990) and Pietrain (Pi) as well as Duroc (D) and Pietrain (Pi).

Sow genotype	Boar genotype	Porkers genotype
PLW×PL	Linia 990×Pi	(PLW×PL) × (L990×Pi)
PLW×PL	D×Pi	(PLW×PL) × (D×Pi)

During the fattening period the porkers were allowed a fattening diet (a fullportion mixture), two times a day. Animals were slaughtered at the mass of 100±2 kg at the experimental station, cut into two half carcass and kept at the cold room at 4°C for 24 h. The half carcasses were transported to the Mas-AR Food Industry Research and Production Plant, Agricultural University of Szczecin for dissection. Analyses were made on the following two muscles excised from the right half-carcass of each porker: m. longissimus lumborum (LL) and m. biceps femoris (BF).

Following the pH₂₄ measurement, muscles were halved. Both halves were weighed and one was injected with curing brine (11% NaCl, 1.5% curing mixture Almonat Super Combi of A. Mittermayr&Söhne GmbH, 87.5% water) in the amount of 25% by weight, and massaged in a vacuum massaging apparatus (-0.8 atm, 6 rpm drum speed) for 8 hours (the 0.5 h massaging to 0.5 h rest cycle). The effective massaging time was 4 h. The unmassaged half of the muscle was a control sample.

Structure

Histological assays were made on samples cut from the mid-part of both massaged and unmassaged muscles. The samples about 5×5×15 mm were fixed in Sannomiya solution, dehydrated in alcohol and benzene and embedded in paraffin blocks [1]. The blocks were sectioned into 10±1µm slices perpendicularly to muscle fibres with a microtome MPS-2. The sections were placed on slides and contrast-stained with hematoxylin and eosin and sealed with Canada balsam.

Histological analyses of the slides, involving measurements of the muscle fibre cross sectional area and connective tissue (perimysium and endomysium) thickness were carried out with the MultiScan v. 6.02 computer image analysis software. The structural elements were measured in an area of 4 muscle sections, and more than 150 muscle fibre and 100 connective tissue thickness/samples were analyzed per each sample.

Thermal drip

The remaining two parts after sampling for structural analyses, were weighed, brought together so that their cut surfaces touched and were placed individually in thermoresistant plastic bags, and cooked in water at 75°C until the geometric centre of a sample was heated to 68°C. The cooked samples were cooled, cold stored for 12 h at 4°C, re-weighed, and thermal drip loss (%) was calculated from the difference in weight before and after thermal treatment.

Texture and rheological properties

Subsequently, after weighing, the muscles were cut across the fibre length to produce 20+1 mm thick slices and then samples about 20×20×100mm. Texture and rheological measurements were performed in an Instron 1140 apparatus by applying the compression test, Warner-Bratzlera (WB) shear test, and relaxation test, at a crosshead rate of 50 mm/min.

The compression test involved driving a 9,6 mm diameter shaft once, in parallel to muscle fibre into a sample down to 80% of their original height (16 mm). It allowed calculating the value of compression force (N).

The shear force (N) was evaluated using the Warner-Bratzlera (WB) shear test which involved cutting a muscle sample with a triangular knife, in parallel to muscle fibre.

Rheological properties were assessed by applying a relaxation test during which a sample was compressed down to 10% its height (2 mm) by 12.6 mm diameter shaft and allowed to remain in this state for 120 s. The generalised Maxwell model, consisting of the Hook body interlinked in parallel with two Maxwell bodies, was used to calculate elasticity and viscosity moduli. The model’s relaxation equation is as follows:

where: σ, stress; ε, strain; E₀, E₁, E₂, elasticity moduli of Hook’s body and of the first and second Maxwell’s bodies, respectively; μ₁, μ₂, viscosity moduli of the first and second Maxwell’s bodies, respectively; t, time.

Calculated values of the three elastic moduli are summarised in the figures as their sum; similarly, the values of the two viscous moduli are presented as their sum.

Statistical analyses

Statistical analyses of the data involved the calculation of the mean values for an each animals as well as mean values for each groups of different genotype as a mean from each individual porkers. The differences in values of parameters tested between the muscles within a group of porkers as well as between the groups of animals of different genotype for each muscle, both massaged and non-massaged (control), were studied using the t-Student’s test. Treatment differences were tested for significance at the 5% level. All the calculations were performed with Statistica® v.5.5A software.

RESULTS AND DISCUSSION

A comparison between textural parameters of muscles tested (table 1) showed a higher values of shear and compression forces as well as viscosity moduli and lower value of elasticity moduli of (PLW×PL) × (L990× Pi) hog muscles compared to (PLW×PL) × (D×Pi) muscles. The differences were dependent on muscle type tested. A higher compression and shear forces (by about 15 and 9% respectively), a higher (by about 14%) viscosity moduli and lower (by about 24%) elasticity moduli were typical of LL muscle of cross-bred with L990×Pi showed compared to LL muscle of (PLW×PL) × (D×Pi) porkers. No significant differences (9, 10, 6 and 14% respectively) in textural parameters of BF muscle between animal groups were found. It can be concluded that, LL compared to BF was the muscle that the most differentiated the animal groups in respect of textural parameters. Other authors [8, 31] who also compared different pig pure-breeds in terms of muscle quality (i.a. hardness, thermal drip losses) also reported inter-breed differences in muscle texture. No differences in meat quality of porkers of different genotype was reported also by Suzuki et al. [25] and Channon et al. [2], however cross-breds with higher share of Duroc gene showed, similarly to our findings, lower hardness and thermal drip losses.

The differences in textural parameters between two muscles tested were also found within an each porkers group (table 1), however it was dependent on their genotype. The (PLW×PL) × (L990×Pi) porkers LL muscle was characterized by about 43% higher compression force, by about 57% higher shear force and higher elasticity and viscosity moduli (by about 27 and 30%, respectively) than the BF muscle. The corresponding differences in textural parameters of (PLW×PL) × (D×Pi) muscles were about 46, 57, 17 and 34%, respectively. Thus, it can be concluded that the differences in textural parameters between the muscles within an each animal group were about the same, however the higher differences were found between a porkers groups. This conclusion is supported by data reported by other authors i.a. Jukna et al. [8] and Wood et al. [31] who found significant higher differences in meat quality within than among groups of porkers.

Table 1. Mean values of textural parameters of the LL and BF muscles of porkers of different genotype

Sow genotype	PLW×PL		PLW×PL		Significance of differences between animal groups
Boar genotype	Linia 990×Pietrain		Duroc×Pietrain
Muscle	LL	BF	LL	BF	LL	BF
Control samples
Compression force [N]	60.5a	106.2b	52.8a	97.8b	NS	NS
Shear force [N]	74.2a	172.6b	67.9a	157.0b	NS	NS
Elasticity moduli [kPa]	220a	300b	290a	350b	*	NS
Viscous moduli [kPa×s]	80800a	115100b	71200a	108350b	*	NS
Massaged samples
Compression force [N]	39.2a	85.3b	27.9a	65.4b	*	*
Shear force [N]	58.8a	144.4b	49.9a	122.7b	*	*
Elasticity moduli [kPa]	280a	330bx	360a	400b	*	*
Viscous moduli [kPa×s]	55700a	98800b	50600a	91500b	NS	NS

a, b – samples in a row, denoted by different letters, were significantly different within an animal group (P<0.05); * – samples in a row were significantly different between animal groups (P<0.05); x – difference between massaged sample and the control was not-significant (P>0.05); NS – not significant differences (P>0.05).

The differences in meat texture can be resulted in muscle structure. A muscle became harder as its fibres cross-section area grew higher [9, 24, 33], peri- and endomysium grew thicker [6, 15, 16, 24] and as the amount of its connective tissue increased [19, 29]. These correlations was evidence also by the data presented here. Of the porkers muscles tested, the highest shear and compression forces as well as viscous and elasticity moduli were found in muscles which, at the same time, showed higher pH_24, the highest thermal drip losses (table 2) and the highest fibre cross sectional area and diameter as well as the thickest peri- and endomysium. The differences in physico-chemical properties and muscle structure, as in texture, were dependent on both muscle type and porker genotype. The (PLW×PL) × (L990×Pi) LL and BF muscles showed higher by about 14 and 12% thermal drip losses, higher by about 33 and 24% fibre cross sectional area and thicker by about 22 and 7% perimysium than those in the (PLW×PL) × (D×Pi) porkers muscles. Similarly to textural parameters, LL was the muscle that the most differentiated the animal groups in respect of structural elements. No significant differences in pH₂₄, fibre diameter and endomysium thickness of corresponding muscles between groups of animal of different genotype were found. Of the each porker group tested, higher differences in thermal drip losses as well as structural elements were found, similarly to data conneted with meat texture, betwen LL and BF muscles. The LL muscle of (PLW×PL) × (L990×Pi) porkers compared to BF muscle showed lower (by about 14%) thermal drip, lower (by about 24 and 12%) fibre cross sectional area and fibre diameter, and thinner (by about 30 and 18%) perimysium and endomysium. Those differences between LL and BF muscle within a (PLW×PL) × (D×Pi) porkers group were by about 16, 29, 15, 38 and 17%, respectively. The differences in structure of the muscles studied was evidence by different function in mammal organism [14, 23].

Table 2. Physico-chemical properties of the LL and BF muscles of porkers of different genotype

Sow genotype	PLW×PL		PLW×PL		Differences between animal groups
Boar genotype	Linia 990×Pietrain		Duroc×Pietrain
Muscle	LL	BF	LL	BF	LL	BF
pH24	5.61a	5.70a	5.60a	5.68a	NS	NS
Thermal drip losses [%]	17.5a	20.3b	15.3a	18.1b	*	*
Thermal drip after massaging [%]	11.1a	14.4b	8.9a	11.3b	*	*

a, b – samples in a row, denoted by different letters, were significantly different within an animal group (P<0.05); * – samples in a row were significantly different between animal groups (P<0.05); NS – not significant differences (P>0.05).

Table 3. Mean values of structural elements of the LL and BF muscles of porkers of different genotype

Sow genotype	PLW×PL		PLW×PL		Differences between animal groups
Boar genotype	Linia 990×Pietrain		Duroc×Pietrain
Muscle	LL	BF	LL	BF	LL	BF
Control samples
Fibre cross sectional area [µm2]	1600a	2100b	1200a	1700b	*	*
Fibre diameter [µm]	47.4a	54.0b	43.9a	51.6b	NS	NS
Perimysium thickness [µm]	12.1a	17.2b	9.9a	16.1b	*	NS
Endomysium thickness [µm]	1.31ax	1.59bx	1.25ax	1.51bx	NS	NS
Massaged samples
Fibre cross sectional area [µm2]	2200a	2400a	1700a	2100b	*	*
Fibre diameter [µm]	58.3a	60.0a	55.6a	58.0a	NS	NS
Perimysium thickness [µm]	14.5a	18.8b	13.2a	17.9b	NS	NS
Endomysium thickness [µm]	1.27ax	1.55bx	1.20ax	1.46bx	NS	NS

a, b – samples in a row, denoted by different letters, were significantly different within an animal group (P<0.05); * – samples in a row were significantly different between animal groups (P<0.05); x – difference between massaged sample and the control was not-significant (P>0.05) NS – not significant differences (P>0.05).

Massaging resulted in an augmentation of elasticity moduli and in reduction of shear and compression forces as well as viscosity moduli (table 1) and thermal drip losses (table2), however the massaging-dependent changes differed both between the porkers genotype and muscle type. Of the (PLW×PL) × (L990×Pi) LL and BF muscles massaging caused a reduction of compression force by about 35 and 20% (fig. 1A), shear force by about 21 and 16% (fig. 1B), viscosity moduli by about 31 and 14% (fig. 1D) and thermal drip losses by about 37 and 29% (fig. 2A) and at the same time an increase in elasticity moduli by about 27 and 10% (fig. 1C), respectively. Massaging of (PLW×PL) × (D×Pi) LL and BF resulted in decrease in compression force (by about 47 and 33%, respectively) (fig. 1A), shear force (by about 26 and 22%) (fig. 1B), viscosity moduli (by about 29 and 16%) (fig. 1D) and thermal drip losses (by about 42 and 38%) (fig. 2A) as well as an increase in elasticity moduli (by about 19 and 14%) (fig. 1D). The analysis of textural parameters changes during massaging showed, both muscles of (PLW×PL) × (D×Pi) porkers, as well as LL muscle were more susceptible to massaging than other group of animal and BF muscle. This findings is supported by data reported by other authors i.a. Motycka&Bechtel [18], Lachowicz et al. [12, 13], Sobczak et al. [24] who found muscles were shown to differ in their susceptibility to tenderisation. Massaging, due to mechanical effects on brine-injected meat, induces histological changes in it, involving, i.a. swelling of myofibrils and muscle fibres and increased collagen solubility. The differences in the susceptibility of various muscles can be conditioning by the differences in the histological structure of the muscles. Katsaras&Budras [10] are of the opinion that connective tissue forms a barrier to brine penetration, thereby limiting muscle fibre swelling. On the other hand, Sobczak et al. [24] fund that massaging in muscles consisted with fibres of smaller diameter compared to bigger one’s, caused a larger increase in the mean fibre cross-sectional area. As shown in this work, massaging of LL and BF muscles of (PLW×PL) × (L990×Pi) porkers resulted in an increase in muscle fibre cross sectional area by about 38 and 14% (fig. 2B) and in perimysium thickness by about 20 and 9% (fig. 2C) as well as in decrease in endomysium thickness by about 4 and 3% (fig. 2D). Of the (PLW×PL) × (D×Pi) porkers LL and BF muscles massaging caused an increase in fibre area by about 42 and 24% (fig. 2B), and perimysium thickness by about 33 and 11% (fig. 2C) and insignificant (by about 3 and 2%) decrease in endomysium thickness (fig. 2D). A comparison of muscle structure changes between the breeds and between the muscles revealed that the LL muscle was the most responsive to massaging than BF and on the ther side the most susceptible were the muscles of (PLW×PL)× (D×Pi) porkers compared to (PLW×PL) × (L990×Pi) porkers. The present work shows that the pigs muscles regardless f animal group – LL muscle or all the muscles tested of (PLW×PL) × (D×Pi) porkers) were characterised by a structure with the most susceptible to massaging, were more susceptible to massage-induced changes in textural parameters. To sum up, it cuold be concluded that LL among the muscles tested as well as muscles of (PLW×PL) × (D×Pi) porkers were more preferable to massaged product production.

Figure 1. The effects of massaging on changes, expressed as percentages, in: (A) compression force; (B) shear force; (C) elasticity moduli; and (D) viscosity moduli in the LL and BF muscles of porkers of different genotype

a, b – values, denoted by different letters, were significantly different within a animal group (P<0.05); 1, 2 – values, denoted by different numbers, were significantly different between animal groups (P<0.05)

Figure 2. The effects of massaging on changes, expressed as percentages, in: (A) thermal drip losses; (B) muscle fibre cross sectional area; (C) perimysium thickness; and (D) endomysium thickness in the LL and BF muscles of porkers of different genotype

a, b – values, denoted by different letters, were significantly different within a animal group (P<0.05); 1, 2 – values, denoted by different numbers, were significantly different between animal groups (P<0.05)

CONCLUSIONS

No significant differences in structural elements and textural parameters between muscles of two groups of porkers were found. Higher differences in meat quality within an animal breed were found compared to those differences between porkers of different genotype. Regardless of an animal group, LL – muscle with a most delicate histological structure than the BF muscle showed lower values of texture parameters. At the same time, LL muscle was the most responsive to structural and textural changes during massaging, and was the muscle with the better utility to massaged product. Of the porkers gropus tested, (PLW×PL) × (D×Pi) muscles were more susceptible to mechanical tenderisation and were preferable to massaged product production.

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Accepted for print: 16.10.2006

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Małgorzata Sobczak
Department of Meat Technology, Faculty of Food Technology and Fisheries,
West Pomeranian University of Technology, Szczecin, Poland
K. Królewicza 4, 71-550, Szczecin, Poland
phone: (+48 91) 423 10 61 ext. 332
email: msobczak@zut.edu.pl

Kazimierz Lachowicz
Department of Meat Technology,
West Pomeranian University of Technology, Szczecin, Poland
K. Królewicza 4, 71-550, Szczecin, Poland
phone: (+48 91) 423 10 61 ext. 332


Joanna Żochowska-Kujawska
Department of Meat Technology,
West Pomeranian University of Technology, Szczecin, Poland
K. Królewicza 4, 71-550, Szczecin, Poland
phone: (+48 91) 423 10 61 ext. 332
email: joanna.zochowska-kujawska@fish.ar.szczecin.pl

Leszek Gajowiecki
Department of Meat Technology,
Agricultural University of Szczecin, Poland
K. Królewicza 4, 71-550, Szczecin, Poland
phone: (+48 91) 423 10 61 ext. 332


Andrzej Klemke
Department of Meat Technology,
Faculty of Food Sciences and Fisheries,
Agricultural University of Szczecin, Poland
K. Krolewicza 4, 71-550, Szczecin, Poland
phone: (+48 91) 423 10 61 ext. 332

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