Summary. A selective medium for the isolation and enumeration of Microbacterium thermosphactum is described and data is presented on its use in assessing the composition of the flora of meat and meat products.

Bncteriological changes in pork stored a t 16 and 2" under gas permeable and gas impermeable films and 'aerobic' conditions have been studied. The concentrations of CO,, 0, and N, in the atmosphere within the packs were also determined. The groups of bacteria isolated from prepaclred pork were Pseudomonas-Achronaobacter spp., Rzuthia spp., Microbacterium thermosphactum, Enterobacter-Hafnia spp. and lactobacilli. Their importance is discussed in relation t,o storage temperature and gas composition within the packs.

Total microbial growth and chemical changes in aerobically stored bacon lean were found to fall into 2 phases. Phase 1: there was an increase in total microbial load to c. 109/g, during which most of the nitrate was broken down and there was an accumulation of nitrite. Phase 2: the microbial load increased further to c. 1010/g and during this time most of the accumulated nitrite was broken down to unknown products, so that at the end of the experiments most of the nitrate and nitrite had disappeared from the bacon. The most important types of micro‐organisms isolated from the bacons were Micrococcus, yeasts, Vibrio, Acinetobacter, Alcaligenes and Arthrobacter‐Corynebacterium. The latter 3 types appeared to be associated with phase 2 changes.

Changes in the levels of 21 amino compounds, ammonium-N and urea-N. during the storage of fresh beef at various temperatures have been investigated. The meats were also subjected to bacteriological analysis. Glutathione and glutamine were found to decrease in the meats during storage, while most other aniinoacids, notably glutamic acid and tryptophan, increased. The increase in glutamic acid appeared to be related to the microbial numbers in the meats. On the other hand, the increase in tryptophan seemed directly related to the time and temperature of storage. There was an initial increase in urea-N followed by a gradual disappearance of this compound from the stored meats. Ammonium-N did not rise significantly until the stage of incipient spoilage had been reached. lntroduction Studies in the changes of individual free amino-acids in beef during storage have been the subject of numerous investigations,1-8 most of which are concerned with autolytic processes. However, Avshalumova5 examined the changes in the free amino-acids in meat during storage at 18-20' and at the same time observed the microbiological condition of the meat by a direct smear technique.The levels of ammonium N have also been evaluated as an index of microbial proteoly~is.~-~8 The most recent workers16-l* agree that it is an index of advanced rather than incipient putrefaction of flesh foods and is not a good index of spoilage. Recorded values for the ammonium N content of fresh meat show wide variations.5~ 1'J, 18 In this paper the changes in the levels of free amino-acids, ammonia, urea and the number and types of bacteria present in beef during storage have been examined to assess if any of the chemical criteria could be used as an index of incipient spoilage. Experimental Preparation of meatsExperiment 1 .-The source and preparation of the meats stored at 4", 9" and 15" has been described elsewhere by Gardner . @ Experiment 2.-The meats used in this experiment were taken from the foreleg muscles of cows within 3 h post mortem. The preparation of these was similar to that in Experiment I, except that in all cases the storage temperature was 15". Bacteriological analysisThe techniques and media employed in assessing the flora changes of the meats during storage have been previously described.lg Chemical analysisSamples were taken at the time of bacteriological analysis and stored at -20" until required. Protein and fat-free extracts of the meats were preparmed by the method of Awapara.20 +Present address : Ulster Curers' Association, 2 Greenwood Avenue, Belfast 4, N. Ireland. J. Sci. Fd Agric., 1966, Vol. 17,, NovemberAmino-acids.-Amino-acids were separated by the electrochromatographic procedure of Biserte et aL21 and quantitatively estimated by the method of Barrollier.22 Elution of the neutral amino-acids and basic amino-acids after primary separation was carried out by the method of Finkle.23 Glutamine was estimated as glutamic acid after the neutral amino-acid fraction of each sample had been hydrolysed in 2~ sulphuric acid for 60 min. a...

Kurthia zopfii was frequently isolated from meats, especially comminuted meats. Its proportion of the aerobic flora in such products a t the point of production did not generally exceed 10%. It is not known to cause spoilage of refrigerated meats, but there is some evidence to suggest that its presence in the flora is indicative of high ternperatures during the product,ion, distribution, etc., of the product. Morphological and physiological characteristics of K. topfiii wrre examined, and it was found that the species could he divided into two distinct groups. There was no association between the group and the product from which it was isolated.