Suitability of recombinant camel (Camelus dromedarius) chymosin as a coagulant for Cheddar cheese N. Bansal a , M.A. Drake b , P. Piraino c , M.L. Broe d , M. Harboe d , P.F.Fox a , P.L.H.McSweeney a , * a Department of Food and Nutritional Sciences, University College Cork, College Road, Cork,Ireland b Department of Food Science, North Carolina State University, Raleigh,NC 27695, USA c Dr P.Piraino Statistical Consulting, Via Verdi 110, 87036,Rende,CS,Italy d Chr.Hansen A/S, DK-2970 Hoersholm, Denmark a r t i c l e i n f o Article history: Received 15 January 2008 Received in revised form 31 March 2009 Accepted 31 March 2009 a b s t r a c t Cheddar-type cheeses were manufactured using fermentation-produced camel or calf chymosin. There were no significant differences in the composition and pH between the cheeses made with either coagulant.The extent of primary proteolysis was significantly lower in cheeses made with camel chy- mosin than in cheeses made with calf chymosin. There were large quantitative differences between the peptide profiles of cheeses;however,the levels of amino acids were similar exceptfor isoleucine, histidine and lysine. The cheeses made with camel chymosin were characterized by lower intensities of sulphur and brothy flavours and showed less bitter taste; however, the cheeses made with calf chymosin had greater breakdown of texture, higher smoothness and mouthcoating and were more cohesive and adhesive.The results of this study suggestthat camel chymosin appears to be suitable for making Cheddar cheese with lower levels of proteolysis but with good flavour. Ó 2009 Elsevier Ltd.All rights reserved. 1. Introduction Rennet is the generic name for an enzyme preparation used to coagulate milk in the production of rennet-coagulated cheese and rennet casein.The principalrole of the enzymes in rennet is to coagulate milk,but they also contribute to proteolysis during the ripening of most cheeses,particularly in low/medium-cooked varieties.Proteolysis by residual rennet influences the texture and flavour of cheese (Fox and McSweeney, 1997).Originally,rennet was extracted from the abomasum of the dairy animal (most commonly,the calf) which contains aspartic proteinases. Rennets extracted from calf, kid or lamb abomasa were the principal commercial coagulants until recently. In addition to animal rennets, natural coagulants from vegetable sources such as Cynara cardun- culus, Ficus carica, Arctium minus and Solanum dobium are also used traditionally in some parts of the world (Robinson and Wilbey, 1998). With an increase in cheese production, it became necessary to find sources of rennets other than from the abomasa of young dairy mammals. Although many, perhaps most, proteinases can coagulate milk, only a few can be used successfully as rennet substitutes. For production of good quality cheese, it is necessary that the rennet substitute should have weak general proteolytic activity, narrow specificity at or near the Phe 105 –Met 106 bond of k -casein and be easily denatured in whey. Otherwise,excessive proteolysis by the enzyme during cheesemaking may cause yield losses during manufacture and the development of a bitter flavour in the final product ( Fox and McSweeney, 1997). Aspartic proteinases used for milk coagulation have a narrow specificity with a preference for peptide bonds to which a bulky hydrophobic residue supplies the carboxyl group. With developments in recombinant DNA technology, the gene for calf chymosin has been cloned into microorganisms, permitting the production of chymosin by fermentation. Such ‘‘fermentation- produced chymosins’’ are now widely used for cheese manufacture in many countries and give excellentresults.The literature on rennets and rennet substituteshas been reviewed extensively (Ernstrom and Wong, 1974; Fox and McSweeney, 1997; Green, 1977; Nelson, 1975; Phelan, 1985; Sardinas, 1972; Sternberg, 1976). Recently, Kappeler et al.(2006) expressed the gene for camel (Camelus dromedarius) chymosin in Aspergillus niger and produced camel chymosin by fermentation. The properties of fermentation- produced camel chymosin were compared with those of calf chy- mosin; camel chymosin has a 70% higher clotting activity per mol * Corresponding author. Tel.: þ353 21 4902011; fax: þ353 21 4270001. E-mail address: p.mcsweeney@ucc.ie (P.L.H. McSweeney). Contents lists available at ScienceDirect International Dairy Journal j o u r n a l homepa ge: w w w . e l s e v i e r . c o m / l o c a t e / i d a i r y j 0958-6946/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.idairyj.2009.03.010 International Dairy Journal 19 (2009) 510–517