It was demonstrated that the sound wood of two stems of living western hemlock, Tsuga heterophylla (Raf.) Sarg., was colonized by microorganisms, which were isolated by shaking samples of the wood in sterile distilled water. The microfloras inhibited the growth of Fomes annosus, (Fr.) Cke., and Poria monticola Murr. when added to one per cent malt agar. The test fungi were also inhibited on untreated surface sterilized wood incubated at one hundred per cent relative humidity at room temperature. Significant variation was observed, in the rate of inhibition between the sapwood and heartwood and between the various sections of the two stems investigated. A drier environment (higher agar concentration of malt agar media, and lower relative humidity with wood) resulted in a significant decrease in inhibition rate of F. annosus and P. monticola. Autoclaving the experimental material led to the loss of inhibition with both malt agar media and wood. Removal of the microorganisms from the shake solutions by Millipore filtration also resulted in loss of the inhibiting factor. The relatively drier environment did not effect the rate of growth of the test fungi on autoclaved wood and in malt agar containing the autoclaved portion of the shake solutions. Results of the experiment provide evidence that the microfloras inhabiting the sound wood were responsible for inhibition of F. annosus and. P. monticola. Furthermore, sufficient moisture level appeared necessary for maintaining the inhibiting power of these microorganisms. / Forestry, Faculty of / Graduate

Ninety-four presumptive Micrococcus and Staphylococcus strains isolated from both commercial beef biltong and game biltong, were identified using a scheme based on the system used by Baird-Parker. The changes occurring in both the aerobic, saprophytic microbial flora and the environmental factors, during conversion of beef to biltong, were examined. The predominantly Gram-negative, halo-sensitive flora initially present on the meat, was replaced by Gram-positive, halo-tolerant staphylococci and micrococci, which form the dominant component of the microflora of the final product. This replacement was attributed to changing environmental factors, principally to the increasing sodium chloride concentration and associated decline in water activity. The presence of the antifungal antibiotic, pimaricin, during processing did not influence the bacterial flora of the product. However, the addition of potassium sorbate altered the microbial profile of the product significantly. The presence of these two preservatives, at the concentrations used, could not be detected organoleptically. The importance of the saprophytic microflora of the product ln relation to the environmental factors during processing, is also discussed.

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Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2006. / Härtill 6 uppsatser.