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αs1-, αs2-, β- and κ-caseins from Somali camels (Camelus dromedarius) were purified by acid precipitation at pH 4·4, crudely separated into an α-CN and a β-CN fraction and further purified by reversed-phase HPLC. Fragments of tryptic digests were sequenced. Amino acid patterns obtained were used to screen a cDNA library constructed from mRNA from lactating udder tissue. Full length clones corresponding to the four caseins were sequenced. The numbers of residues in the sequences deduced were αs1-CN 207, αs2-CN 178, β-CN 217, κ-CN 162. Percentage similarity to bovine proteins was αs1-CN A 39, αs2-CN 56, β-CN 64, κ-CN 56. Acid-precipitated casein of pooled milk was separated by reversed-phase HPLC and monitored at 220 nm, and its composition, estimated from peak integration, was (g/kg total casein) αs1-CN 220, αs2-CN 95, β-CN 650, κ-CN 35. Degrees of phosphorylation and glycosylation were determined by laser ionization mass spectrometry and sequence pattern analysis. Molecular masses determined were (kDa) αs1-CN A, 24·755 and 24·668; αs1-CN B, 25·293; αs2-CN 21·993; β-CN, 24·900; κ-CN 22·294–22·987. The pH values of the most probable isoelectric points were: αs1-CN A 6P 4·41, αs1-CN B 6P 4·40, αs2-CN 9P 4·58, β-CN 4P 4·66, κ-CN 1P, with ten sialic acid residues bound, 4·10.

Introduction Present distribution and milk production Main components Gross composition Overall protein composition Casein fractions Size distribution of casein Whey protein fractions Lipids Fatty acid composition CONTENTS PAGE 603 604 605 605 606 607 609 611 612 612 Phospholipids Physical state and properties of fat globules Lactose Minerals and vitamins Enzymic coagulation Effects of heat on milk Antibacterial activity Conclusions References INTRODUCTION PAGE 613 614 616 616 617 620 623 623 624 Camels belong to the family Camelidae and thereby to the suborder Tylopoda. The tylopoda themselves belong to the order Artiodactyla or cloven-footed animals. The family of Camelidae contains the genera Camelus (old world camel) and Lama (new world camel). The Camelidae originated in North America where the earliest fossil remains of Camelidae have been found. The genus Camelus migrated from North America in the late Tertiary across the then existing land bridge to Asia and Africa. The llamas on the other hand reached South America in the ice age across the Central American land bridge. Included in the genus Camelus are the one-humped dromedary (Camelus dromedarius) and the two-humped bactrian (Camelus bactrianus). The term dromedary is derived from the Greek 'dromados' (run) and in the strict sense is used for riding camels. The name 'Bactrian' for the two-humped camel refers to the area ' Baktria' in North Afghanistan where this type of camel is thought to have originated. The dromedary is slim, long-legged, short-haired and has its habitat in warm arid and semi-arid areas. The bactrian is stockier, short-legged and has a thicker and longer coat than the dromedary. It mainly occurs in cold and mountainous areas (Simpson, 1945; Zeuner, 1963). This review is concerned entirely with the one-humped camel; the term ' camel' should therefore be taken to refer to Camelus dromedarius unless specifically stated otherwise. The majority of the studies conducted on camels concentrate on anatomical features, traditional management and physiological adaptation to desert conditions (Cauvet,

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