The effects of hot-deboning on the physical meat quality and microbial quality and safety of ostrich (Struthio camelus) meat

Pretorius, Karla (2019-04)

Thesis (MScFoodSc)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: The aim of this study was to investigate hot-deboning as an alternative excising method for the South African ostrich industry. The majority of research conducted on hot-deboning is on beef (pre-rigor meat), whilst research on the hot-deboning of ostrich meat (post-rigor meat) remains within a limited scope. Fifteen ostriches were used for the study with the muscles hot-deboned (within 90 min post-mortem) from the left leg and cold-deboned (<4°C, 24 h post-mortem) from the right leg. Half of the sixteen hot-deboned muscles’ weights were heavier (p ≤ 0.05) than those cold-deboned. Five ostrich muscles: fan fillet (M. iliofibularis); rump steak (M. iliotibialis lateralis); big drum (M. gastrocnemius, pars interna); moon steak (M. femorotibialis medius) and triangle steak (M. flexor cruris lateralis) were used to establish meat quality at day three post-mortem. The varying ultimate pH (pHu) values between muscles (p = 0.01) were still within the expected range for ostrich meat with the big drum having the highest pHu (means ± standard deviation; 5.95 ± 0.16) linking with its low drip loss percentage (0.90% ± 0.30). The fan fillet had amore red (a* = 13.43 ± 1.21), saturated (Chroma = 16.58 ± 1.61) colour whereas the big drum was more blue (b* = 9.68 ± 1.52), with the lowest colour intensity (hue angle = 35.64 ± 3.79). Concerning Warner-Bratzler shear force values, the fan fillet was the most tender (35.34 N ± 8.26) in contrast with the moon steak (72.23 N ± 15.81) which can be linked to the high cooking loss percentage (37.05% ± 1.90) of the latter muscle. A vacuum packaged ageing trial for 28 d post-mortem (0 - 4°C) was conducted on the above-mentioned five muscles. Hot-deboning did not have an effect on the pHu (p = 0.50). Although a few significant differences in the colour coordinates (CIEL*a*b*, hue angle and Chroma) were found. Neither the cumulative moisture loss nor the cooking loss percentages showed significant differences between the hot- and cold-deboned muscles (p > 0.05). Concerning Warner-Bratzler shear force (WBSF) values, only the hot-deboned rump steak was tougher (p ≤ 0.05) at day 28 post-mortem as compared to cold-deboned with a value that is still considered within the tender meat range (34.74 N vs. 26.55 N). Microbiological analysis conducted on the aforementioned five muscles showed an absence of Salmonella spp. in all hot- and cold-deboned samples. Hot-deboning did not have an effect on the mean Aerobic Counts (AC) nor the Enterobacteriaceae counts over the 28 d ageing period (p ≤ 0.05). Aerobic and Enterobacteriaceae counts for hot- and cold-deboned muscles were however higher in comparison with fresh meat standards used by the ostrich industry; whether this is standard or due to the specific execution of the experiment per se is unclear. Regarding these findings, hot-deboning is deemed a suitable alternative to cold-deboning for the ostrich industry of South Africa.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om warmontbening as alternatiewe ontbeningsmetode vir die Suid-Afrikaanse volstruisindustrie te ondersoek. Die meerderhied van bestaande navorsing rakende warmontbening is gedoen op beesvleis (pre-rigor vleis), terwyl die omvang van navorsing oor die warmontbening van volstruisvleis (post-rigor vleis), steeds beperk is. Fyftien volstruise is gebruik vir hierdie studie, met die spiere warm-ontbeen (binne 90 min post-mortem) van die linkerbeen en koud-ontbeen (<4°C, 24 h post-mortem) van die regterbeen. Die helfte van die sestien warm-ontbeende spiergewigte was swaarder (p ≤ 0.05) as dié van die koud-ontbeende spiergewigte. Vyf volstruispiere: die M. iliofibularis; M. iliotibialis lateralis; M. gastrocnemius, pars interna; M. femorotibialis medius en M. flexor cruris lateralis is gebruik om die fisiese vleiskwaliteit op dag drie post-mortem vas te stel. Die varieërende uiteindelike pH (pHu) waardes tussen spiere (p = 0.01) was steeds binne die verwagte reeks vir volstruisvleis met die M. Gastrocnemius, pars interna wat die hoogste pHu gehad het (5.95 ± 0.16) en ooreenstem met sy lae dripverlies persentasie (0.90 ± 0.30). Die M. iliofibularis het ‘n meer rooi (a* = 13.43 ± 1.21), versadigde (16.58 ± 1.61) kleur gehad teenoor die M. Gastrocnemius, pars interna wat meer blou was (b* = 9.68 ± 1.52), met die laagste kleurintensiteit (35.64 ± 3.79). Rakende die Warner-Bratzler skeurkrag, was die M. iliofibularis die sagste (35.34 N ± 8.26) in kontras met die M. femorotibialis medius (72.23 N ± 15.81) wat toegeskryf kan word aan laasgenoemde se hoë kookverlies persentasie (37.05% ± 1.90). ‘n Verouderingsproef oor 28 d post-mortem (0 - 4°C) is uitgevoer op dieselfde vyf vakuumverpakte spiere. Warmontbening het nie ‘n effek op die pHu (p = 0.50) gehad nie. Alhoewel ‘n paar beduidende verskille in die kleur-koördinate teenwoordig was, het warmontbening geen negatiewe effek gehad nie (p > 0.05). Nie die kumulatiewe vogverlies of die kookververlies persentasies het beduidende verskille tussen die warm- en koud-ontbeende spiere getoon nie (p > 0.05). Rakende Warner-Bratzler skeurkrag waardes was slegs die M. iliotibialis lateralis (34.74 N vs. 26.55) taaier (p ≤ 0.05) op dag 28 post-mortem met ‘n waarde wat steeds beskou word binne die reeks vir sagte vleis. Mikrobiologiese analise wat uitgevoer is op bogenoemde vyf spiere het ‘n afwesigheid van Salmonella spp. in alle warm- en koud-ontbeende monsters getoon. Warmontbening het nie ‘n effek op die gemiddelde Aërobiese Tellings of Enterobacteriaceae tellings oor die 28 d verouderingstydperk (p ≤ 0.05) gehad nie. Aërobiese en Enterobacteriaceae tellings vir warm- en koud-ontbeende spiere was wel hoër in vergelyking met vars vleis standaarde wat gebruik word deur die volstruisindustrie. Rakende hierdie bevindinge word warmontbening beskou as ‘n geskikte alternatief vir koue-ontbening vir die volstruisindustrie van Suid-Afrika.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106103
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