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The lipids of six strains of Bacteroides ruminicola were characterized. The nonpolar lipid accounted for 6 to 24% of the total lipid and was composed of diglycerides, triglycerides, and free fatty acids. The phospholipid fraction contained phosphatidylethanolamine, phosphosphingolipids, and trace quantities of phosphatidic acid. In three strains the phosphosphingolipid fraction made up more than half of the total lipid. The fatty acids in the nonpolar, acyland phosphosphingolipid consisted of a homologous series of branched and normal chains from 12 to 19 carbons. The long-chain base isolated from the phosphosphingolipids consisted of a homologous series of branched and normal chains from 14 to 24 carbons. Abraham (Ph.D. thesis, Univ. of Maryland, College Park, 1965) investigated the lipids isolated from a mixed population of rumen bacteria and found an unusual sphingolipid which contained ethanolamine. This ethanolamine-containing sphingolipid was later isolated from Bacteroides ruminicola strain 23 grown on a chemically defined lipid-free medium (J.

Mechanically deboned meat (MDM) from flat bones and neck bones of cattle was tested against ground beef for differences in rate of lipid oxidation. To measure the oxidative changes in MDM and ground beef, the fatty acid disappearance from the polar and nonpolar lipids and the production of monocarbonyls during storage were monitored. The meat was tested under two separate temperatures; 2-3°C and analyzed at intervals on days 0, 2, 4, 6, 9 and 13; -35°C and analyzed at intervals on days 0, 30 and 90. Two additional flat bone samples were stored (aged) for 5-6 days and then deboned and analyzed. Differences in the slopes of regression lines for oxidation of each polyunsaturated fatty acid showed no major differences between the disappearance of the fatty acids in MDM when compared to ground beef. Little change occurred in the polar and nonpolar fatty acids during storage at 2-3°C or at -35°C. Monocarbonyls were a better indicator of oxidation rate. than total carbonyls. Increases in monocarbonyls during storage reached a peak on the sixth day of storage at 2-3" C and then declined. No significant differences were found in monocarbonyl content of MDM when compared to monocarbonyl content of ground beef. Polyunsaturated fatty acid/hemoprotein molar ratios of all samples analyzed were in the area where hemoproteins act as antioxidants. Overall, lipids in MDM from beef bones (aged or fresh) oxidized at about the same rate as lipids in ground beef.

Hemopoietic marrow from the cervical and lumbar vertebrae and muscle adjacent to the vertebrae of four veal, four steers, and four cows were analyzed for total pigment, hemoglobin, myoglobin, and iron. Total pigment, hemoglobin, and iron were higher in marrow than in muscle. Hemoglobin and iron content of marrow remained relatively constant with increasing age while myoglobin and iron content of muscle doubled in steers and tripled in cows when the values were compared to those of veal. Pigment and iron interactions for age times location occurred because marrow from the lumbar vertebrae became fatter sooner than marrow from cervical verte brae. Storing muscle or marrow 1-wk at 2°C or freezing muscle or marrow at -29°C for 60 days prior to analyses did not change total pigment concentration or hemoglobin and myoglobin percentages in tissue. Mechanically processed beef product (MPP) is a mixture of muscle and marrow and the amount of total pigment increases as the amount of hemoglobin from marrow increases. Therefore, total pigment determination offers a simple method for estimating marrow content of MPP provided constant total pigment values for muscle and marrow by age of animals and by anatomical location can be established.

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