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The aim of this study is to transform milk of camel, raised in an extensive system, into kefir. The pasteurization (63°C for 30 min) of the milk, the incubation with three rates of kefir grains (2,5 and 10%) and different incubation times (18; 20 and 24 h) were evaluated during the transformation. The physicochemical characteristics of milk, kefir grains, camel kefirs and the chemical composition of the diet of the camels were measured. The results showed that camel milk is characterized by a neutral pH value (6.9 ± 0.11) and a high dry matter (DM) content of 114.2 ± 0.11g/l. Kefir grains have an acid pH (3.9) and their fat content is very low (0.02 g/kg). The chemical composition of pastoral species showed an NDF content of 33.9 to 81.1% and an ADF content of 22.5% to 61.7%. Varying the rate of kefir grains from 2,5 to 10% had a significant effect on the pH, acidity and viscosity of the kefir obtained for the different incubation times (18, 20 and 24 h). Consequently, camel milk was suitable for transformation into kefir in accordance with legislative standards. Keywords: Camel milk, kefir grains, pastoral plants and chemical characteristics, L’objectif de ce travail est de transformer le lait de chamelle élevée dans un système extensif en Kéfir. La pasteurisation (63°C pendant 30 min) du lait, l’incubation avec trois doses des grains de kéfir (2, 5 et 10%) et à différents temps d’incubations (18; 20 et 24 h) ont été évalués lors de la transformation. Les caractéristiques physico-chimiques des laits, grains du kéfir, kéfirs camelins et la composition chimique de l’alimentation des chamelles rencontrée sur parcours ont été mesurées. Les résultats ont montré que le lait camelin se caractérise par une valeur neutre du pH (6,9 ± 0,11) et une teneur en matière sèche importante (114 ± 0,11 g/l). Les grains des kéfirs ont un pH acide (3,9) et leur teneur en matières grasses est négligeable (0,02 g/kg). La composition chimique des espèces pastorales a montré que la teneur en NDF a été de 33,9 à 81,1% et la teneur en ADF a été de 22,5% à 61,7%. La dose des grains du kéfir (2,5 et 10 %) a eu un effet significatif sur le pH, l’acidité et la viscosité du kéfir obtenu pour les différents temps d’incubation (18, 20 et 24 h). Par conséquent, le lait camelin a une aptitude à la transformation au kéfir conforme aux normes législatives.  Mots clés: Lait camelin, grains de kéfir, plantes pastorales et les caractéristiques chimiques

Cilj ovog istraživanja bio je utvrditi fizikalno-kemijska svojstva i antioksidativnu aktivnost devinog obranog kolostruma i mlijeka u prahu obrađenog postupkom liofilizacije. Dobiveni rezultati pokazali su da je obrani prah kolostruma imao veći udio proteina u usporedbi s mlijekom u prahu, koje je s druge strane imalo veći udio laktoze i pepela. Analiza mineralnog sastava pokazala je da su koncentracije kalcija i magnezija veće u obrađenom prahu kolostruma, dok se koncentracija željeza nije bitno razlikovala između obranog kolostruma i mlijeka u prahu. Mjerenja parametara boje pokazala su da je devin kolostrum u prahu crveniji, ali manje žut i bijel od obranog devinog mlijeka u prahu. Nadalje, obrano devino mlijeko u prahu imalo je veću gustoću i veću nasipnu gustoću. Topljivost proteina u obranom kolostrumu u prahu bila je znatno veća nego u obranom mlijeku u prahu, i to u širokom rasponu pH (3-8). Antioksidacijska aktivnosti određivana je korištenjem različitih in vitro testova, uključujući 2,2-difenil-l-pikrilhidrazil (DPPH) i 2,2’azino-bis (3-etilbenztiazolin-6-sulfonska kiselina) (ABTS) reducirajuću aktivnost radikala, kao i FRAP metodu te kapacitet keliranja željeza. Antioksidacijska aktivnost obje vrste ispitivanih uzoraka pokazala se ovisnom o ispitivanoj količini uzorka. Aktivnosti redukcije radikala DPPH i ABTS metodama bile su slične za obrani kolostrum i mlijeko u prahu, dok je aktivnost dobivena FRAP metodom te sposobnost keliranja željeza bila izraženija u obranom devinom kolostrumu, bez obzira na ispitivanu koncentraciju. Stoga se postupak liofilizacije može upotrijebiti kao djelotvoran način proizvodnje praha iz obranog devinog kolostruma i mlijeka u prahu s očuvanom hranjivom vrijednosti i antioksidacijskim svojstvima., This study aimed to determine the physicochemical properties and antioxidant activities of dromedary skim colostrum and milk powder produced by freeze-drying. Results of the study showed that skim colostrum powder possessed higher protein content compared to milk powder whereas this latter had greater lactose and ash content. The analysis of mineral content revealed that calcium and magnesium levels were higher in skim colostrum powder while the iron level did not differ significantly between skim colostrum and milk powder. The measurements of colour characteristics indicated that dromedary skim colostrum powder was redder, but less yellow and white than dromedary skim milk powder. Further, dromedary skim milk powder had higher bulk density and tapped bulk density. Protein solubility of skim colostrum powder exceeded that of skim milk powder over a wide range of pH (3-8). The antioxidant activities were evaluated using various in vitro tests, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, ferric reducing power assay and ferrous chelating activity. Both dromedary skim colostrum and milk powder exhibited antioxidant activities in a dose dependent manner. DPPH and ABTS radical scavenging activities were almost similar for skim colostrum and milk powder whereas ferric reducing power and ferrous chelating activity were more pronounced in dromedary skim colostrum powder whatever the concentration tested. Hence, freeze-drying process could be used as an effective tool for producing powder from dromedary skim colostrum and milk with nutritional and antioxidant properties.