COMPARISON OF THE MICROBIOLOGICAL QUALITIES OF TURKEY MYOFIBRILLAR PROTEIN ISOLATE, MECHANICALLY RECOVERED TURKEY MEAT AND TURKEY BREAST

Adam Malicki¹, Szymon Brużewicz², Alicja Żechałko-Czajkowska³, Krystyna Szybiga⁴, Wiesław Kopeć⁵, Tadeusz Trziszka^6
1 Department of Food Hygiene and Consumer Safety, Agricultural University of Wrocław, Poland
² Institute of Social Problems of Health and Education, Warsaw School of Social Psychology, Poland
³ Department of Food Storage and Technology, Agricultural University of Wrocław, Poland
⁴ Department of Economics and Organization of Agriculture, Agricultural University of Wrocław, Poland
⁵ Department of Animal Products Technology, Agricultural University of Wrocław, Poland
⁶ Department of Animal Products Technology and Quality Management, Wrocław University of Environmental and Life Sciences, Poland

ABSTRACT

The results of previous studies revealed that the nutritive value of myofibrillar protein isolate (MPI) is very high and significantly predominates over that of mechanically recovered meat (MRM). Little, however, is known on the post-production contamination of MPI. Consequently, the purpose of our study was to evaluate the microbiological quality of MPI and to compare it with those of raw turkey breast and MRM. The samples of MPI, MRM and turkey breast (30 of each assortment), manufactured under industrial conditions by one of the poultry plants, were subjected to the experiment. The counts of psychrotrophic and mesophilic bacteria as well as the numbers of Enterobacteriaceae, proteolytic bacteria, lactic acid bacteria, coagulase-positive staphylococci, Pseudomonas spp. and saprophytic fungi were determined in material studied. Moreover, the samples were tested for Salmonella spp. and anaerobic sporogenic bacilli. The latter two groups of microorganisms were not found in any of the samples analyzed. Additionally, coagulase-positive staphylococci and saprophytic fungi were not detected in MRM, whilst neither saprophytic fungi nor proteolytic bacteria were isolated from the samples of turkey breast. The average counts of psychrotrophic and mesophilic bacteria, proteolytic bacteria, lactic acid bacteria and Pseudomonas spp. in MPI and MRM were significantly higher compared to raw turkey breast. Consequently, our study revealed that the microbiological quality of MPI manufactured of turkey meat is relatively low. Accordingly, efficient reduction of the post-production contamination of MPI is necessary for the safe use of this valuable product in food industry.

Key words: myofibrillar protein isolate, mechanically recovered meat, microbiological quality, post-production contamination.

INTRODUCTION

In the consumption of poultry meats the priority is given to breasts and legs. The other parts of a carcass, most often after mechanical deboning, are used in the production of sausages of lower value.

The development of technology for the production of myofibrillar protein isolate from the mechanically recovered meat (MRM) of turkey made the utilization of this low-value raw material possible and quantitatively better. The idea of the process is MRM fractionation, which consist of the following stages: 1) washing MRM with salt solutions, 2) sedimentation and skimming off “hard” fat, 3) centrifugation with horizontal centrifuge and separation of collagen-rich meat fraction, 4) sedimentation and skimming off “soft” fat, and 5) centrifugation with vertical centrifuge and separation of myofibrillar protein fractions [19]. Literature provides the detailed technical descriptions of lines for the manufacturing of myofibrillar protein isolate [1, 3, 20].

The product called myofibrillar protein isolate (MPI) is highly wet, homogenous, light pink and odorless paste. According to our previous studies, its nutritive value was very high and significantly predominated over that of MRM [23]. The content of cholesterol in MPI was similar as in turkey breast, as well as the composition of amino acids. Iron concentration in MPI was however more than 1.5-times higher compared to turkey breast.

Hence, in the view of aforementioned results, the application of MPI for the purposes of food industry and dietetics seems highly promising. Microbiological quality and resulting shelf-life are however crucial for the technological and consumption use of certain raw material or semi-product. The results of our previous study suggest that the microbiological quality of MRM is low and places the latter in the group of easily-decaying raw materials [23]. The literature, however, lacks the information on the post-production contamination level of MPI. Consequently, the purpose of our study was to evaluate the microbiological quality of MPI and to compare it with those of raw turkey breast and MRM.

MATERIAL AND METHODS

The samples of MPI, MRM and turkey breast (30 of each assortment), manufactured under industrial conditions by one of the poultry plants, were subjected to the experiment. The material, chilled to +4°C, was sent to our laboratory within 12 hours after production was completed. The counts of psychrotrophic and mesophilic bacteria as well as the numbers of Enterobacteriaceae, proteolytic bacteria, lactic acid bacteria, coagulase-positive staphylococci, Pseudomonas spp. and saprophytic fungi were determined in material studied. Moreover, the samples were tested for Salmonella spp. and anaerobic sporogenic bacilli. All microbiological determinations were performed in accordance with compulsory standards [7-16].

Statistica 5, Version 97 (StatSoft^®) package was used for the statistical analysis of results. Microbiological counts were transformed into logarithms and compared between the groups of assortments by means of t Student test (p<0.05).

RESULTS

The results of microbiological determinations of particular product categories are summarized in Table 1. Either Salmonella spp. or anaerobic sporogenic bacilli were not found in any of the samples analyzed. Additionally, coagulase-positive staphylococci and saprophytic fungi were not detected in MRM, whilst neither saprophytic fungi nor proteolytic bacteria were isolated from the samples of turkey breast. The average counts of psychrotrophic and mesophilic bacteria, proteolytic bacteria, lactic acid bacteria and Pseudomonas spp. in MPI and MRM were significantly higher compared to raw turkey breast.

Table 1. Microbiological characteristics (mean ± standard deviation, CFU x g-1) of turkey myofibrillar protein isolate (MPI), mechanically recovered turkey meat (MRM) and turkey breast

Parameter	MPI	MRM	Turkey breast
Psychrotrophic bacteria	6.08 ± 0.51	5.54 ± 0.16	3.79 ± 0.52*
Mesophilic bacteria	5.45 ± 0.16	4.54 ± 0.87	3.79 ± 0.73*
Enterobacteriaceae	3.62 ± 1.24	3.51 ± 0.54	2.58 ± 0.54
Proteolytic bacteria	4.93 ± 0.70	4.02 ± 0.47	NF*
Lactic acid bacteria	4.88 ± 0.53	3.99 ± 0.54	0.89 ± 1.55*
Coagulase-positive staphylococci	1.21 ± 2.09	NF	0.77 ± 1.33
Salmonella spp.	NF	NF	NF
Pseudomonas spp.	4.56 ± 0.30	4.20 ± 0.64	2.26 ± 0.31*
Anaerobe sporogenic bacilli	NF	NF	NF
Saprophytic fungi	1.13 ± 1.95	NF	NF

* – significant differences (p≤0.05) NF – not found

DISCUSSION

Our study revealed that the microbiological quality of MPI is similar to that of MRM, and consequently – it is significantly lower compared to raw turkey breast.

Microbiological status of raw material or semi-product applied to food industry reflects to its primary and secondary contamination with microflora. Saprophytic or pathogenic microorganisms, present in the tissues of animals before slaughter, constitute the primary contamination of animal origin foods. Secondary contaminants in turn get into food products during manufacturing, storage and distribution [22].

The microbiological qualities of MPI and MRM – significantly worse compared to turkey breast – have probably complex etiology. Both breasts and the parts of turkey carcass which were used for MPI and MRM manufacturing originated from the same batch. Nevertheless, we cannot exclude that the primary microbiological contamination of the latter was higher, since some authors claimed on inhomogeneous quantitative distribution of microflora throughout the carcass [17]. The differences in post-production contamination, however, might be also related to the technological processes, the lower-value parts of turkey carcass were exposed to. It is widely known that the microbiological status of food products reflects to the number of technological operations performed on raw material during manufacturing [4, 5, 21]. Ecological environment of MRM is more favorable for microorganisms than that of intact meats. The natural structure of muscular tissue is damaged and its continuity is broken in course of MRM manufacturing. Moreover, during the mechanical recovery of meat, its microflora is mixed and aerated. The aforementioned factors in turn create favorable conditions for the microbial growth in meats [18].

The application of myofibrillar protein isolate to food technology is highly advisable, due to its high nutritive value and the relatively low cost of production [23]. Consequently, there is a need for further efforts oriented on the improvement of the microbiological quality of MPI. This goal might be achieved by the upgrading of the microbiological status of raw material. Nevertheless, as already mentioned, the increase of secondary contamination with microflora is unavoidable in case of products requiring numerous technological processes, such as MPI. Consequently, the possibility of secondary decontamination of that product with non-thermal techniques should be considered. Both high hydrostatic pressures and pulsed electric fields seem attractively in that matter since they were successfully used for the impr ovement of the microbiological quality of raw meats [2, 6].

CONCLUSIONS

1. The microbiological quality of MPI manufactured of turkey meat is relatively low.

2. The efficient reduction of the post-production contamination of MPI is necessary for its safe application to food industry.

REFERENCES

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4. Malicki A., Brużewicz S., 2004. Ocena zmian aktywnosci wodnej, pH oraz trwałosci mikrobiologicznej przetworów ze sledzi o różnym stopniu rozdrobnienia [Comparison of microbiological stability of herring products with variable cut-up degree]. Acta Sci. Pol., Med. Vet., 3(2), 25-33 [in Polish].

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6. Malicki A., Sysak Z., Suder E., Brużewicz S., 2004. Application of high hydrostatic pressures for non-thermal reduction of Salmonella and Escherichia coli and their effect on microscopic structure of poultry meat. Pol. J. Environ. Stud., 13, suppl. II, 318-321.

7. Polish Standard PN-A-82055-12: 1997. Mięso i przetwory mięsne. Badania mikrobiologiczne. Wykrywanie obecnosci beztlenowych bakterii przetrwalnikujšcych i beztlenowych bakterii przetrwalnikujšcych redukujšcych siarczyny (IV) [Meat and meat products. Microbiological examinations. Detection of anaerobic spore forming bacteria and anaerobic spore forming bacteria of sulphite (IV) reducing] [in Polish].

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12. Polish Standard PN-EN ISO 6888-1: 2001. Mikrobiologia żywnosci i pasz. Horyzontalna metoda oznaczania liczby gronkowców koagulazo-dodatnich (Staphylococcus aureus i innych gatunków) [Microbiology of food and animal feeding stuffs. Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species). Part 1: Technique using Baird-Parker agar medium [in Polish].

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16. Polish Standard PN-ISO 7954: 1999. Mikrobiologia. Ogólne zasady oznaczania drożdży i pleœni. Metoda płytkowa w 25°C [Microbiology. General guidance for enumeration of yeasts and moulds. Colony count technique at 25°C] [in Polish].

17. Stopforth J.D., Lopes M., Shultz J.E., Miksch R.R., Samadpour M., 2006. Microbiological status of fresh beef cuts. J. Food Prot., 69, 1456-1459

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19. Trziszka T., Kopeć W., Busko J., 1994. Mechanically recovered meat (MRM) and the possibilities of its processing. International Conference “Meat Protein Isolates”, Œwiebodzin-Przełazy, 18-24.

20. Trziszka T., Uijttenboogaart T.G., Schreurs F.J., 1993. Isolierte myofibrilläre Proteine aus mechanisch separierten Geflügelfleisch. Produktmerkmale bei unterscheidlichen Verfahren [Isolated myofibrillar proteins from mechanically recovered poultry meat. Product features by various technologies]. Fleischwirt., 73, 1069-1071 [in German].

21. Uyttendaele M., De Troy P., Debevere J., 1999. Incidence of Listeria monocytogenes in different types of meat products on the Belgian retail market. Int. J. Food Microbiol., 53, 75-80.

22. Zaleski S.J., 1985. Mikrobiologia żywnosci pochodzenia zwierzęcego [Microbiology of animal origin food. Wydawnictwa Naukowo-Techniczne]. Wydawnictwa Naukowo-Techniczne. Warszawa [in Polish].

23. Żechałko-Czajkowska A., Malicki A., Szybiga K., Kopeć W., Trziszka T., 1994. Nutritive value and hygienic evaluation of ISOPROM and preliminary cost analysis of its production. International Conference “Meat Protein Isolates”, Swiebodzin-Przełazy, 75-86.

 

Accepted for print: 17.11.2006

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Adam Malicki
Department of Food Hygiene and Consumer Safety,
Agricultural University of Wrocław, Poland
C.K. Norwida 31, 50-375 Wrocław, Poland
tel. (0-71) 320 53 99
email: malicki@ozi.ar.wroc.pl

Szymon Brużewicz
Institute of Social Problems of Health and Education,
Warsaw School of Social Psychology, Poland


Alicja Żechałko-Czajkowska
Department of Food Storage and Technology,
Agricultural University of Wrocław, Poland
C.K. Norwida 25, 50-375 Wrocław, Poland

Krystyna Szybiga
Department of Economics and Organization of Agriculture,
Agricultural University of Wrocław, Poland
M. Skłodowskiej-Curie 42, 50-369 Wrocław, Poland
email: szybiga@ekonom.ar.wroc.pl

Wiesław Kopeć
Department of Animal Products Technology,
Agricultural University of Wrocław, Poland
C.K. Norwida 25/27, 50-375 Wrocław, Poland

Tadeusz Trziszka
Department of Animal Products Technology and Quality Management,
Wrocław University of Environmental and Life Sciences, Poland
C.K. Norwida 25, 51-630 Wrocław, Poland
Phone: (+48 71) 32 05 121
email: trziszka@ozi.ar.wroc.pl

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