The microorganisms present determine to a great extent the quality of cured meat. Some of them may have unfavorable effects on the color and flavor, whereas others are known to have beneficial effects on these quality factors. Yeasts, bacilli, and streptococci were found to be predominately present in a cover pickle which had been recently used for curing hams in a commercial meat packing plant. They were isolated and their characteristics studied. All three organisms rapidly reduced resazurin and litmus milk, but failed to reduce nitrates. They were salt-tolerant and grew best at about 21°C. The yeasts did not produce carbon dioxide when grown in lactose or glucose fermentation tubes. The effect of these organisms on the rate of color development during curing of pork was studied. Ham from a freshly slaughtered hog was cut aseptically and ground. It was blended with a sterile curing solution and inoculated with each of the test organisms. It was then incubated at 60°F. for 24 hours and finally heated at 120°F. The color development throughout curing was studied with the Photovolt Spectrophotometer with a reflectance attachment. The pH, oxidation-reduction potentials, and plate counts were determined during curing at 60°F. The results indicated that the organisms tested improved the color of cured meats by reducing the oxidation-reduction potential of the meat during curing. / Graduation date: 1955

Top loin steaks were used to determine the influence of packaging procedure on the microbial growth and succession on the top and bottom surfaces of steaks during a 12 day storage period. The following packaging treatments were used: (1) Gas permeable Resinite film overwrap as a control; (2) gas flush with 1% CO, 40% O₂, 59% N₂ for 2 minutes followed by film overwrap; (3) loose packaging in gas impermeable barrier bags with 100 to 150 cc ambient air; (4) 15% CO₂, 40% O₂, 45% N₂ gas atmosphere; (5) 60% CO₂, 40% O₂ gas atmosphere; and (6) 10% CO₂, 5% O₂, 85% N₂ gas atmosphere. Total psychrotrophic counts obtained from the top and bottom surfaces did not differ significantly for most sampling periods. Similar growth patterns were observed on both steak surfaces, increasing (P <.05) primarily between Day 3 and Day 9 of post-treatment storage. The steaks packaged within the gas atmospheres had lower (P<.05) total growth than the control steaks. Comparing atmospheres, the steaks packaged in relatively low CO₂ and O₂ levels (10% and 5%, respectively) had lower (P<.05) microbial growth than steaks packaged in 15 to 60% CO₂ and 40% O₂ when initial contamination was low. Pseudomonas dominated the microflora on the steak surfaces in all packaging treatments during early storage. Other aerobic organisms which survived gas atmosphere treatments include Coryneforms, Micrococcus, and Microbacterium, although they did not show large increases in growth. Coryneforms were also competitive on the bottom surface of the control steaks despite domination by the pseudomonad organisms. Loose packaging in impermeable barrier bags allowed the growth of Serratia liquifaciens after 6 days of storage. This bacterium also tended to dominate the flora within the gas atmosphere packages, although other facultative organisms (Enterobacter aerogenes and Yersenia enterocolitica) were also identified. When initial contamination was low, the gas atmospheres provided an effective means of prolonging the shelf-life of fresh beef steaks.

Meat Juice Medium (MJM), an aqueous extract of meat, was inoculated with Pseudomonas aeruginosa and incubated for 7 d at 4$ sp circ$C under shaking conditions (100 rev.min$ sp{-1}$). Two predominant compounds produced during spoilage of MJM were detected using HPLC. These compounds with retention times (RT) of 21.48 and 32.04 min were tentatively identified as acetic and butyric acids, respectively. These compounds were also produced when MJM was replaced with Brain Heart Infusion Broth medium. In later experiments, the effect of glucose supplementation on the rate of MJM spoilage was examined. Glucose 0.5% (wt/vol) was added to the MJM, inoculated with P. aeruginosa and incubated at 30$ sp circ$C under shaking conditions (100 rev.min$ sp{-1}$). HPLC of samples after 1d of incubation indicated the presence of 8 predominant compounds including acetic and butyric acids. Their concentrations were, in general, higher in control samples of MJM without added glucose. Using HPLC, TLC, Pyrolysis/GC/MS, FTIR and GC-MS methodologies, the compounds with RT of 8.91, 9.67, 11.96, 13.33, 17.74, 21.48, 26.07 and 32.04 min were tentatively identified as cadaverine, 2-keto gluconic acid, fructose, lactic acid, acetic acid, methanol and butyric acid. In contrast to the results of previous researchers, cadaverine was produced in large amounts while no putrescine was produced by P. aeruginosa. During the spoilage period, the levels of glucose, fructose and total carbohydrate were monitored. Addition of glucose to MJM delayed slime production by 4 days and increase to maximum pH of 8.3 by 7 days. Results suggest that addition of glucose to MJM delays spoilage by P. aeruginosa.

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The broad objective of this study was to determine the effects of natural antioxidants and thermal treatment on quality of meat from Bonsmara and non-descript cattle. A survey was conducted among 222 consumers in Alice (Fort Hare University community), Eastern Cape Province to determine the level of their awareness on application of antioxidants as preservatives in meat and meat products during storage. Representative samples of Muscularis longissimuss thoracis et lumborum and liver were collected from each carcass of Bonsmara (n=40) and non-descript (n=40) cattle reared on natural pasture to determine the effect of natural antioxidants and thermal treatment on their quality. The results from the survey revealed that 51.35 percent of the respondents had not heard about the use of antioxidant as preservatives in meat products. However, among the remaining respondents (48.65 percent) that were aware of antioxidant and its use as preservative, about 19 percent knew of natural antioxidants, 35 percent synthetic antioxidants while 46 percent had knowledge of both. The results further revealed that the majority of the respondents (82 percent) that had knowledge of natural antioxidants were concerned about the use of synthetic antioxidants in meat and meat products due to their health consequences. The in vitro antioxidant and antibacterial analyses of Bidens pilosa and Moringa oleifera leaf extracts revealed that they contain rich bioactive compounds. Furthermore, the addition of leaf extracts from Moringa oleifera (ML, 0.05 and 0.1 percent w/w) and Biden pilosa (BP, 0.05 and 0.1 percent w/w) to ground raw beef as a natural antioxidant were found to improve the physicochemical, oxidative stability and microbiological qualities of meat compared to the control (meat without extract) and BHT treatment (0.02 percent w/w) during 6 days storage at 40 C. Cattle breed did not have much effect on colour parameters. However, the overall pH of ground beef treated with extracts showed lower values than control and BHT treated beef. Also, ground beef samples containing extracts exhibited (P < 0.05) better colour stability, especially higher redness (a* values), than the control. The formation of TBARS in beef samples treated with extracts was significantly (P < 0.05) lower than the control and BHT treatment. The antibacterial assay of the extracts revealed an appreciable broad spectrum activity against the tested bacteria and microbial counts in ground beef samples compared to control and BHT group. Ground beef treated with plant extracts exhibited lower microbial and lactic acid bacterial counts (P < 0.05) at day 0 and 3 than control samples. Moreover, it was observed that application of sous vides thermal method did not significantly affect the fatty acids and mineral loss in beef and liver across the treatments. However, the total concentration of MUFA was lower in raw liver (20.11±2.38 - 21.08±1.23 percent) than in beef (40.22±1.90 - 42.53±1.29 percent), while total PUFA content were higher in liver (30.73±2.60 - 31.11±1.19 percent) than in beef samples (10.13±3.36 - 11.02±2.74 percent) (p < 0.05). The results also revealed that liver samples from Bonsmara and non-descript cattle had a higher percentage of intramuscular fat content of 4.67 ± 0.53 percent and 4.44 ± 0.53 percent respectively, and fat free dry matter of 27.51 ± 1.05 percent and 25.73 ± 1.05 percent, respectively, than the beef samples (p < 0.05). The concentrations of Mg (52.80±0.22 - 53.70±0.02mg/100g) and Zn (8.90±0.15 - 19.60±0.15mg/100g) were higher in beef than liver samples. The level of Ca (17.00±0.17 - 17.50 ± 0.17mg/100g) in liver was higher than that of beef samples. It was concluded that most consumers preferred the use of natural antioxidants in meat products than synthetic antioxidants due to their health risk. The effectiveness of M. oleifera and B. pilosa leaf extracts on meat quality also revealed that these plants are promising candidates as natural preservatives and their application should be considered in the meat industry. Lastly, findings from this study showed that application of the sous vide technique could protect meat products from nutritional loss during thermal treatment.

M.Tech. (Biotechnology) / Please refer to full text to view abstract

Digitized by Kansas Correctional Industries

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.