No description available.

The adhesion of seven meat spoilage bacteria to model meat surfaces (thin fat and tendon slices) was studied in a specially designed flow chamber. In general, adhesion was not influenced by the physiological age of the cells and was not correlated with the cell surface characteristics (electrical charge, hydrophobicity) of the organisms. Also, adhesion data did not corroborate the predictions based on changes in the free energy of adhesion, calculated from contact angles and surface tension measurements. A more detailed study of the adhesion of Pseudomonas fluorescens to tendon was subsequently undertaken. Neither physiological activity nor the presence of flagella was found to be essential for adhesion. Selective chemical alterations of the cell surface pointed to no direct implication of carboxyl or amino groups in an adhesive bond with tendon. These groups may participate in adhesion, however, through electrostatic interactions as suggested from the variations of adhesion with ionic strength.

Beef tendons were sectioned into 60 mum-thick slices (1cm 2) and deposited onto glass cover slips. These meat slices were flooded with a cell suspension of either Pseudomonas fluorescens, Enterobacter agglomerans, or Moraxella osloensis in distilled water and adhesion allowed to occur. The adhesion experiments were also conducted on agar-covered slides to evaluate the effect of the nature of the substratum on adhesion. The non-adherent organisms found on either surface tested (meat or agar) were removed by flushing liquid over the slide. The slides were then incubated in a moist atmosphere at 30°C. Once the presence of microcolonies had been established microscopically, the slides were mounted into flow chambers and the surface flushed with distilled water to ascertain the effects of bacterial proliferation on adhesion. In other experiments, the influence of acetic, citric, and lactic acid rinses on cell adhesion and subsequent cell proliferation was evaluated. Microcolony formation was shown to reduce the adhesion strength of Enterobacter agglomerans and, to a lesser extent, that of Moraxella osloensis while increasing that of Pseudomonas fluorescens. The probable determinant of adhesion strengths of microcolonies is exopolymer synthesis. A minimal decrease in bacterial adhesion and microcolony formation was observed with the use of organic acid rinses. The bactericidal activity and effect on bacterial proliferation increased with increasing concentration and rinse times of the organic acids. The extent of the adhesion reductions suggests that the preservation action of organic acids is due to cell death and not adhesion inhibition.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The purpose of this study was to describe the nature of springbok (Antidorcas marsupialis) muscle and the changes that take place in the longissimus thoracis et lumborum (LTL) and biceps femoris (BF) muscles post-mortem (PM); thereby providing recommendations for the handling of the meat. Springbok muscle contained 64 - 78% type IIX fibres, suggesting that it is considerably more glycolytic than bovine muscle. In males the BF contained more type I and fewer type IIA fibres than the LTL and it appeared that female springbok contained a greater proportion of type IIX fibres than males. The cross-sectional areas (CSA’s) of the fibres were low but within the range reported for domestic species. There was an increase in the CSA with the glycolytic capacity of the fibres in males (I < IIA < IIAX < IIX) but no difference between fibre-types in females. Springbok muscle cooled rapidly and acidified slowly relative to recommended set points for domestic species, with this being most evident in the female LTL. Differences in cathepsin and calpain activity between the genders and muscles were evident, with the higher calpain activity in the BF and male springbok likely a reflection of the fibre-type composition of these samples. The cathepsin BL activity increased PM, possibly due to the degradation of the lysosomal membranes. Calpain and calpastatin activity declined PM, with correlations (r = -0.64; p < 0.01) between the pH decline rate and the change in calpastatin activity indicating that more rapid acidification results in a greater decrease in calpastatin activity. No further improvement in the Warner Bratzler shear force (WBSF) of springbok LTL or BF took place from five to 21 days of ageing. The cathepsin activity increased during the ageing period, with the high activity in the absence of a decline in WBSF suggesting that the cathepsins did not contribute to tenderization. The calpain and calpastatin activity declined to negligible levels by five days PM, suggesting that they were activated in situ and were involved in tenderization. Higher WBSF values were found for the BF throughout the ageing period. Springbok LTL increased in sensorial tenderness and sustained juiciness and decreased in residue from three to eight days PM; however ageing to 28 days increased a number of undesirable aroma and flavour attributes and decreased beef-like aroma. This was most likely due to oxidative and proteolytic changes. The WBSF was low for all ageing periods, with no significant change being found. Gender did not have a large influence on the sensory quality of the meat. The results of this study indicate that springbok meat tenderizes rapidly PM, with ageing periods of five to eight days being recommended to avoid detrimental flavour changes. The chilling rate appears to have a greater effect on the meat than any differences in the fibre-type composition, with the temperature and pH declines PM indicating a risk of cold-shortening. However the WBSF values found question the necessity of specialized handling techniques being used. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die aard van springbokvleis en die veranderinge wat plaasvind na dood in die Longissimus thoracis et lumborum (LTL) en biceps femoris (BF) spiere te omskryf. Sodoende word voorstelle vir die korrekte hantering van springbok vleis voorsien. Die springbokspiere bevat 64 - 77% tipe IIX vesels wat aandui dat dit aansienlik meer glikolities van aard is in vergelyking met die van bees. In die manlike diere het die BF meer tipe I en minder tipe IIA vesels gehad as die LTL. Daarmee saam het die vroulike springbokke ‘n hoër hoeveelheid tipe IIX vesels gehad as die manlike. Die opeervlakte van die springbok vesels was klein, maar steeds binne die omvang van wat gemeld is vir gedomestiseerde diere. Tesame met ‘n toename in die glikolities kapasiteit was daar ‘n toename in die vesel oppervlakte van die manlike diere (I < IIA < IIAX < IIX), maar geen verskil is egter gevind vir die vroulike diere. Die springbok spiere het snel verkoel en redelik stadig versuur, relatief tot die van gedomestiseerde spesies. Dit was die mees voor die hand liggend in die vroulike LTL spier. Verskille in die katepsien en kalpaïen aktiwiteit tussen die geslagte was duidelik en die hoër kalpaïen aktiwiteit in die BF van die manlike diere is waarskynlik as gevolg van die samestelling van die veseltipes. Die katepsien BL aktiwiteit het toegeneem na-dood wat moontlik te wyte is aan die afbraak van die lisosomale membrane. Kalpaïen en kalpastatien aktiwiteit het verlaag na-dood en korrelasies (r = -0.64; p < 0.01) tussen die tempo van die pH daling en die verandering in die kalpastatien aktiwiteit het aangedui dat ‘n snel versuring lui tot ‘n groter afname in kalpastatien aktiwiteit. Daar was geen verbetering in die instrumentele sagtheid van die springbok LTL of BF vanaf vyf dae veroudering tot en met 21 dae. Die katepsien aktiwiteit het toegeneem tydens die verouderings tydperk. As gevolg van die hoë aktiwiteit tesame met die afwesigheid van ‘n afname in instrumentele sagtheid wil dit voorkom of die katepsiene geen bydrae gelewer het tot versagting. Beide die kalpaïen en kalpastatien aktiwiteit het weglaatbaar afgeneem teen vyf dae van veroudering wat aandui dat hierdie ensieme moontlik geaktiveer is in-situ en daarom betrokke was by versagting. Die BF spier het hoër instrumentele taaiheid waardes getoon reg deur die verouderings tydperk. Die springbok LTL het ‘n toename in sensoriese sagtheid en verlangde sappigheid tesame met ‘n afname in residu getoon vanaf drie tot ag dae veroudering. Die veroudering tot en met 28 dae het egter verskeie ongewensde aroma en geur eienskappe na vore gebring. Die paneel het ook ‘n afname in die bees aroma opgetel. Die voorkoms van hierdie ongewensde sensoriese eienskappe is heel waarskynlik as gevolg van oksidatiewe en proteolitiese veranderinge tydens veroudering. Die instrumentele sagtheid was redelik laag reg oor die verouderingstydperk en geen beduidende verskille is gevind. Geslag het geen verskil gehad op die sensoriese kwaliteit van die vleis nie. In geheel toon die resultate van hierdie studie dat springbokvleis snel verouder. Die aanbevole verouderingstydperk is tussen vyf en agt dae om sodoende nadelige aroma en geur veranderinge te vermy. Dit wil blyk of die verkoelingstempo ‘n groter invloed op die vleis het as enige verskil in die samestelling van die vesel tipes. Die temperatuur en pH dalings na-dood dui wel op die risiko van kouekrimping maar die resultate rondom die instrumentele sagtheid bevraagteken wel die noodsaaklikheid van gespesialiseerde hanteringstegnieke.

Visible and near infrared (NIR) reflectance and transmission spectra (400 - 2500 nm) of various flesh foods in various presentations were examined for qualitative and quantitative analysis. Discriminant functions for muscle types and animal species were included. Lamb muscles (n: 306), chicken breast and thigh muscles (n: 48), bull and steer muscles (n: 103), raw fish (n: 80), fish meal (n: 700) and fish oil (n: 160) samples were examined in the experiments. INTACT and MINCED presentation to the instrument were compared, as well as type of muscle (<I>longissimus dorsi, infra spinatus, supra spinatus, semimembranosus, semitendinosus, rectus femoris</I>), effect of sex and both longitudinal (LS) and transverse section (TS) of the muscle on the optical properties and Partial Least Squares (PLS) calibrations for gross composition. MINCED presentation to the instrument gave the best results for the NIRS calibrations in all the muscle tissues utilized, while, INTACT presentation showed poorer calibrations. Muscle type and sex affect the calibrations. Raw fish and fish by-products, both fish meal and oil had good NIRS calibrations for the twelve parameters analyzed. The results show that NIRS is acceptable as a method for determining gross composition in a wide variety of flesh foods in MINCED presentation. Principal component analyses (PCA) and Soft Independent Modelling of Class Analogy (SIMCA) were used for the authentication and classification between muscles and among animal species. The conclusions of this work are that NIRS can successfully predict chemical composition in different muscles in MINCED rather than INTACT presentation. Classifications using PCA and SIMCA were excellent tools to authenticate flesh foods.

This thesis describes the results of three studies that used different measures of bacterial numbers in retail ground beef (n=309) collected across different locations in Saskatchewan within a one-year period (May 2011 – May 2012). The measurements were compared among three sample categories: 1 - ground beef displaying government inspection information on the label legend (n=126), 2 - originating from facilities licensed by local health regions and thus not subjected to government inspection (n=80), or 3 - processed and repackaged at the retail level thus carrying no government inspection information on the label (n=103). The first study reports baseline levels of bacteria in Saskatchewan retail ground beef as measured by traditional (total aerobic plate count (TAPC) and total E. coli plate count (TEPC)) and culture-independent methods (estimate of total bacterial load (TBL) by real-time quantitative polymerase chain reaction). After accounting for season and whether the samples were fresh or frozen at purchase, the lowest TAPC (log10 4.9 culture forming units per gram (cfu/g); 95% CI log10 4.7 to log10 5.1 cfu/g), TEPC (log10 0.58 cfu/g; 95% CI log10 0.39 to log10 0.77 cfu/g), and TBL in frozen ground beef (log10 4.5 target copies per gram (tc/g); 95% CI log10 4.0 to log10 4.9 tc/g) were observed in samples originating from federally regulated or provincially licensed facilities. In the second study, presence of known Enterobacteriaceae virulence factors (stx1, stx2, and eae) was detected by polymerase chain reaction (PCR) and compared between samples originating from three different regulatory and inspection environments as well as collected during different seasons of the year, and purchased fresh or frozen. One hundred and twelve out of all tested samples (n=308) were positive for the presence of at least one virulence marker with stx1 identified in 107 samples, stx2 - in 8, and eae - in 26. No significant associations were found between the virulence markers presence and sample category, state or season of purchase. The third study investigates the presence and diversity of Campylobacter spp. organisms in the same pool of 309 retail beef samples as detected by molecular methods. Fifty samples (16.2%) tested positive for Campylobacter genus-specific DNA in conventional PCR and 49 samples (15.9%) tested positive for at least one Campylobacter species DNA presence in real-time qPCR, but the crude agreement between the two methods was less than 50%. C. coli DNA presence was observed in 14 samples (4.5%), C. curvus – in 11 (3.6%), C. fetus – in 6 (1.9%), C. hyointestinalis – in 24 (7.8%), C. jejuni – in 12 (3.9%), C. rectus – in 6 (1.9%), and C. upsaliensis – in 9 (2.9%). There was no difference in the frequency of Campylobacter identified among the three sample categories, fresh and frozen, or samples purchased during the cold or warm season. These studies provide data on prevalence of bacteria in retail ground beef offered for sale in Saskatchewan and compare differences between samples presented to the consumer as originating from federally regulated or provincially licensed facilities, locally licensed facilities, or repackaged and processed directly at a retail outlet. The information on baseline levels of bacteria in retail ground beef and the comparisons among different categories can be used in prioritising food safety improvement efforts in Saskatchewan.

No description available.

Four meat spoilage organisms were grown at 4$ sp circ$C for 7 d, in an aqueous extract of meat (Meat Juice Medium), and the levels of various nutrients in the extracts were measured. At an agitation rate of 50 rev$ cdot$min$ sp{-1},$ the four species reached viable counts of 10$ sp8$ Colony Forming Units (CFU)$ cdot$ml$ sp{-1},$ and the order of nutrient utilization was as follows: (1) glucose, (2) gluconate and urea, (3) glycerol, (4) glucose-6-phosphate. Several substrates were still present in the growth medium at the end of the growth period, namely lactate, glucose-6-phosphate and the two unknowns. At a higher agitation rate (100 rev$ cdot$min$ sp{-1}),$ the non-fluorescent pseudomonad reached final counts of ca. 10$ sp{10}$ CFU$ cdot$ml$ sp{-1},$ 2 logs higher than those of the other three organisms present in the mixed culture. The order of nutrient utilization was: (1) glucose, (2) gluconate, urea and glycerol, (3) lactate and glucose-6-phosphate, (4) unknowns 1 and 2. At day 7, none of the nine substrates studied remained in the growth medium.

Meat characteristics and physiological stress measurements in bison exposed to different ante-mortem treatment groups and reasons behind the rapid discolouration of fresh bison meat (compared to beef) were examined. It was hypothesized that bison slaughtered on farm (dispatched in pen, MLAPEN, or confined then dispatched MLACON) through a mobile location abattoir (MLA), would have favourable meat characteristics and lower stress levels than those transported to a stationary abattoir (LAND). It was also hypothesized that differences in fatty acid profile, vitamin E levels, and oxidative properties of bison meat compared to beef, are related to the observed difference in retail shelf life. A higher incidence of carcasses graded as “dark” were observed in the LAND group. Improved tenderness measured through shear force (MLACON 7.28 kg and MLAPEN 7.40 kg vs. LAND 9.43kg) and initial tenderness sensory scores (MLACON 4.95, MLAPEN 4.55, vs. LAND 3.93; where 8= extremely tender and 1= extremely tough) was seen in the MLA groups. The lowest blood cortisol level was found in MLAPEN group compared to the MLACON or LAND groups (71.16 nmol/L, 124.17 nmol/L and 139.50 nmol/L respectively; P<0.01). Bruising was found in all treatment groups, however less was found on the MLA groups compared to the LAND group. Fatty acid composition was significantly different between bison and beef for all the fatty acids measured. The inherent tissue traits of bison were linked to poorer performance in the retail environment when compared to beef. Bison meat had higher polyunsaturated fatty acid levels, and a lower omega 6:omega 3 ratio than beef. Bison also had a lower total fat and higher pigment and vitamin E levels. Stepwise regression models included some of these traits and accounted for a significant proportion of the variation in metmyoglobin (R2 = .689), % discolouration (R2 = .737) and appearance (R2 = 0.676) between d 0 and d 3 in retail. An improved understanding of the effects of ante mortem handling and the inherent characteristics of bison meat will improve animal welfare and help create an improved eating experience for the consumer. / Animal Science

Graduation date: 1961