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Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.

Volume 9
Issue 4
Topic:
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
. , EJPAU 9(4), #25.
Available Online: http://www.ejpau.media.pl/volume9/issue4/art-25.html


 

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: .

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.


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Accepted for print: 17.11.2006



Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.


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