Contamination of game carcasses during harvesting and slaughter operations at a South African abattoir

Shange, Nompumelelo (2015-12)

Thesis (MSc Food Sc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: The consumption of game meat and its by-products is increasing locally and internationally. The increase in consumption requires research that is focused on the microbiological quality of game meat. The harvesting and slaughter process of springbok carcasses revealed the presence of bacterial contamination. Swab samples taken after skinning portrayed a presence of Escherichia coli (E. coli) and Enterobacteriaceae. Springbok carcasses swabbed after chilling indicated aerobic bacteria, Clostridium spp. and lactic acid bacteria. In contrast, swab samples taken at the evisceration’s incision area tend to be lower in counts when compared to swab samples taken after skinning and after chilling. Bacterial contamination was linked to poor hygienic practices during the harvesting and slaughter process. Results showed a need for the investigation of the slaughter process. To evaluate the slaughter process’s impact on the microbial quality of game carcasses, black wildebeest (Connochaetes gnou) carcasses were sampled throughout the slaughter process. Before skinning, aerobic bacteria, Enterobacteriaceae, and E. coli were enumerated from hide samples, counts ranged from 0.92 to 7.84 log cfu/g. after skinning, bacterial counts ranged from 0.93 to 6.12 log cfu/g and further decreased after chilling. Clostridium spp. counts increased after skinning, however, statistical analysis detected no significant differences between counts. Salmonella spp. was not detected. The results indicate that bacterial contamination does occur during the slaughter process. Hygienic status during the production of game meat products was also determined. Bacterial counts from raw game meat ranged from 2.37 to 5.37 log cfu/g. Counts as high as 6.16 log cfu/g were enumerated from retail products. Aerobic plate counts (APC) from ≤ 2.62 log cfu/cm2 to ≤ 6.3log cfu/cm2 were enumerated from surfaces, hands and equipment during production. Results highlighted the inefficiency of cleaning procedures and revealed that contaminated meat can allow for bacterial contamination. To determine if muscle pH influences colour stability and microbial spoilage of game meat, normal (n=6) and dark, firm and dry (DFD) (n=6) black wildebeest Longissimus thoracis et lumborum (LTL) muscles were studied. pH affected colour, as initial (day 0) L*,a*,b*,C* and Hab values from Normal pH samples were significantly higher than values reported for DFD samples. Initial APC and Enterobacteriaceae counts from samples with Normal pH were not significantly different from counts reported for DFD samples. Initial contamination was linked to the harvesting and slaughter process. Further refrigeration (5±1ºC) for 12 days in an aerobic environment and analyses of samples every third day revealed that pH did not affect lightness and brownness as L* and b* values for DFD samples did not significantly differ overtime, the same trend was seen for samples with Normal pH. Normal pH samples showed a significant increase in a* and C* values until day 12, whilst Hab values decreased until the 12th day. The same trend was seen for a* and C* values for DFD samples until the 9th day as on the 12th day values increased. Similarly, Hab values for DFD samples decreased until the 9th day, then increased on the 12th day. Using the microbial spoilage limit of 6 log cfu/g, it was seen that DFD meat reached this limit earlier than samples with Normal pH. Overall, the study provides baseline information on the microbiological quality of game meat harvested in South Africa and slaughtered at a South African abattoir.

AFRIKAANSE OPSOMMING: Die plaaslike en internasionale verbruik van wildsvleis en wildsvleisprodukte is aan’t toeneem. Hierdie toename in verbuik vereis navorsing wat gefokus is op die mikrobiese kwaliteit van wildsvleis. Die oes-en slagproses van springbok karkasse het die teenwoordigheid van bakteriese kontaminasie aan die lig gebring. Monsters geneem met ʼn depper na afslag van karkasse het ʼn teenwoordigheid van Escherichia coli (E. coli) getoon. Springbok karkasse wat getoets is na verkoeling het hoë vlakke van die aërobiese bakterium Clostridium spp. en van melksuurbakterieë getoon. In teenstelling hiermee is getalle laer rondom die ontweidings insnyding. Bakteriese kontaminasie was gekoppel aan swak higiëne gedurende die oes- en slagproses. Hierdie resultate het ʼn ondersoek van die slagproses aangemoedig. Om die impak van die slagproses op die mikrobiese kwaliteit van wildskarkasse te evalueer, is monsters regdeur geneem van swartwildebees (Connochaetes gnou). Getalle van aërobiese bakterieë, Enterobacteriaceae, en E. coli was bepaal op vel monsters voor afslag; getalle het gewissel tussen 0.92 en 7.84 log cve/g. Getalle van bakterieë na afslag het gewissel tussen 0.93 en 6.12 log cfu/g, en het verder afgeneem na verkoeling. Clostridum spp. het toegeneem na afslag, maar statistiese analises het geen beduidende verskille getoon nie. Monsters het negatief getoets vir Salmonella spp. Die resultate toon aan dat bakteriese kontaminasie wel plaasvind gedurende die slagproses. Die higiëniese status gedurende die produksie van wildsvleis is ook vasgestel. Bakteriegetalle van rou wildsvleis het gewissel tussen 2.37 log cve/g en 5.37 log cve/g. Getalle van handelsprodukte het getalle getoon van soveel as 6.16 log cve/g. Aërobiese plaat telling tussen ≤2.62 cve/cm2 en ≤ 6.3log cve/cm2 is vasgestel vanaf oppervlakte, hande en toerusting gedurende produksie. Resultate beklemtoon die ondoeltreffendheid van skoonmaakprosedures en wys dat aangetaste vleis bakteriese kontaminasie kan toelaat. Om te bepaal of die kleurstabiliteit en mikrobiese bederf van wildsvleis geaffekteer word deur spiere se pH, is normale (n=6) en donker, ferm, en droë (DFD) (n=6) Longissimus thoracis et lumborum (LTL) spiere van die swartwildebees bestudeer. Kleur was geaffekteer deur vleis pH, siende dat die aanvanklike waardes (dag 0) vir L*, a*, b*, C* en Hab aansienlik hoër was vir monsters met normale pH as DFD monsters. Aanvanklike getalle van aërobiese plaat telling en Enterobacteriaceae telling van monsters met Normale pH het nie beduidend verskil van DFD monsters nie. Aanvanklike besmetting was gekoppel aan die oes- en slagproses. Verdere verkoeling (5±1ºC) vir 12 dae in ʼn aërobiese omgewing en analise van monsters wys dat pH nie ligtheid en bruinheid affekteer nie; waardes vir L* en b* vir DFD monsters het nie beduidend verskil oor tyd nie. Dieselfde geld vir monsters met Normale pH. Monsters met Normale pH het ʼn beduidende toename in a* en C* getoon tot en met dag 12, terwyl waardes vir Hab afgeneem het tot en met dag 12. Dieselfde patroon is waargeneem by waardes vir a* en C* vir DFD monsters tot en met dag 9, terwyl dit toegeneem het op die 12de dag. Soortgelyk het Hab waardes vir DFD monsters afgeneem tot n met dag 9, en toegeneem op die 12de dag. Dit is ook gevind dat DFD vleis die limiet vir mikrobiese bederf (6 log cve/g) vroeër bereik as monsters met Normale pH. Die studie voorsien basis inligting oor die mikrobiese kwaliteit van wildsvleis wat geoes is in Suid Afrika, en geslag is by Suid Afrikaanse slagpale.

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