No abstract

Lean ground round beef was slurried with water liquid-liquid ether extraction, yielded extracts and cooked in a sealed stainless steel vessel at which, after concentration, were analyzed by gas-163 and 182". Atmospheric distillation, followed liquid chromatography (glc) and glc coupled with by, in the case of the lower temperature product, mass spectrometry (glc-ms). Forty-six sulfur-concontinuous countercurrent ether extraction or, for taining chemicals were identified. the 182" material, salt saturation and continuous Recent interest in improved meat flavors and the desirability of employing flavors comprised of naturally occurring components have led to the current investigations of the flavor volatiles in beef. Beef flavor, as well as that of other meats, has been shown to be the product of the heating of a complex system of flavor precursors. In this respect, the chemistry of meat flavors is different from that of fruit, dairy, or fermented flavors. In fact, it is this very difference which has determined to a great extent the approach to their study by many investigators.A glycoprotein isolated by Batzer e t al. (1960, 1962) produced an odor reminiscent of broiled steak when heated in fat with the coisolated nucleotide, inosinic acid. Subsequent investigations of aqueous extracts of raw and/ or cooked beef by numerous groups have lead many (Flament and Ohloff, 1971;Hornstein and Crowe, 1960; Mabrouk e t ul., 1969; Macy e t ul., 1964a,b; Schutte and Koenders, 1972; Tonsbeek e t al., 1969;Wasserman, 1972; Wasserman and Spinelli, 1972) to conclude that the development of meat flavor and aroma is, at least in part, associated with a Maillard-type reaction. As a result, there has been extensive study of model browning systems in attempts to duplicate or simulate meat flavors (Arroyo and Lillard

The quantity and character of the microbial lipid isolated from rumen digesta are interpreted as indicating that significant quantities of milk fat acids originate from rmnen microbial synthesis of long chain acids from volatile fatty acids. Component fatty acid patterns are presented of rumen bacterial lipid, crude tureen protozoal lipid, blood serum lipid, and milk lipid isolated from samples taken from a lactating Holstein. Certain tureen bacterial lipid fractions are shown to be very rich sources of odd carbon acids and branched acids, and it is suggested that the major source of these acids in ruminant fats is from bacterial synthesis rather than animal synthesis.

KATZ, AND M. KEENEY. Metabolic function of branched-chain volatile fatty acids, growth factors for ruminococci. II. Biosynthesis of higher branched-chain fatty acids and aldehydes. J. Bacteriol. 83:1084-1093. 1962.-A number of strains of rumen bacteria require branched-chain volatile fatty acids for growth. A strain of Ruminococcus flavefaciens that requires either isovalerate or isobutyrate incorporates radioactive carbon from isovalerate-1-C04 and isovalerate-3-C14 into leucine and into the lipid fraction of the cells. Evidence obtained by both paper and gas chromatography indicated that most of the label in the lipid of cells grown in isovalerate-1-C14 was in a branched-chain 15-carbon fatty acid, with some in a 17-carbon acid; about 7.5% of the C14 was recovered in a branched-chain 15-carbon aldehyde. The aldehydes were in the phospholipid fraction and were presumably present as plasmalogen. A strain of R. albus was shown to require isobutyrate, 2-methyl-n-butyrate, or 2-ketoisovalerate for growth. This strain did not incorporate appreciable C14 from isovalerate-1-C14 or isovalerate-3-C14. When grown in a medium containing isobutyrate-1-C14, most of the cellular C'4 was found in the lipid fraction. Analysis of the lipid demonstrated that the label was present mainly as branched-chain 14-carbon and 16carbon fatty acids, with 11% of the C'4 present in 14-and 16-carbon carbonyl compounds, presumably branched-chain aldehydes. Branched-chain 14-, 15-, and 16-carbon fatty acids are major components of the lipids of these rumen bacteria. The possibility that these acids and aldehydes, which are found in ruminant body and milk lipids, may be of microbial origin is discussed. 1 Ruminococcus flavefaciens, not recognized in the seventh edition of Bergey's Manual of Determinative Bacteriology, was described by: Sijpesteijn, A. K. 1951. On Ruminococcus flavefaciens, a cellulose-decomposing bacterium from the rumen of sheep and cattle.