International Dairy Journal 15 (2005) 563–569 Effect of the use of three different lamb paste rennets on lipolysis of the PDO Pecorino Romano Cheese M. Addis à , G. Piredda, M. Pes, R. Di Salvo, M.F. Scintu, A. Pirisi Istituto Zootecnico e Caseario per la Sardegna, Loc. Bonassai, 07040 Olmedo, Italy Received 15 April 2004; accepted 9 July 2004 Abstract Two rennet pastes were prepared from lambs on different diets, and then, together with a commercial lamb rennet paste, were used to produce protected designation of origin (PDO) Pecorino Romano cheeses. Chymosin activity and lipolytic activity were higher in the prepared rennets than in the commercial rennet. Lipolysis was greatest in cheese produced with one of the prepared rennets. Both quantitative and qualitative differences in free fatty acids were found in the cheeses. The taste of cheeses made with the prepared rennets was preferred by an expert sensory panel and also considered more piquant than that of cheese made with commercial rennet. The results indicate that both the diet of the lambs and slaughtering conditions should be regulated to produce rennet that preserves the traditional characteristics of PDO Pecorino Romano cheese. Both lipolytic and proteolytic properties of rennet pastes should be standardised for the preparation of such cheeses. r 2005 Elsevier Ltd. All rights reserved. Keywords: Lamb paste rennet; PDO Pecorino Romano; Lipolysis 1. Introduction Pecorino Romano is a protected designation of origin (PDO) cheese that must be made exclusively from whole sheep milk and lamb paste rennet. By law it can only be produced in Sardinia, Latium and the province of Grossetto. This cheese has a particular flavour, which has been attributed to the use of lamb rennet paste. Rennet paste contains various lipases that release free fatty acids (FFAs) during cheese ripening; these acids directly and indirectly influence the taste and the aroma of the cheese (Harper, 1957; Woo & Lindsay, 1984; Na´jera, Barro´n, & Barcina, 1994; Cha´varri et al., 1999; Larra´yoz, Martı´nez, Barro´n, Torre, & Barcina, 1999). The most important lipolytic enzymes in this kind of rennet are pre-gastric lipase (PGL) and gastric lipase (GL) (Richardson, Nelson, & Farnham, 1971; Nelson, Jensen, & Pitas, 1977). The typical characteristics of Pecorino Romano cheese are probably due to the use of lamb rennet paste containing a balanced amount of milk clotting and milk fat-hydrolysing enzymes. The amount of rennet is usually regulated in order to obtain a fixed milk-clotting time, and so using lamb rennet pastes of different enzymatic composition could alter the optimal clotting to lipolytic activity ratio. In recent years there has been a great increase in production of rennet paste in specialised industrial plants. This kind of rennet is used to produce Pecorino Romano and other cheeses (Calandrelli et al., 1997). Nowadays the lambs are weaned earlier (aged 30 days) to deliver more milk to the dairies and this increases the pepsin content in the lambs’ stomachs and simulta- neously reduces the quantity of chymosin and pre- gastric lipase (Manunta, Naitana, Spada, & Calaresu, 1981; Piredda & Addis, 1998). In addition, due to health regulations, lambs are usually slaughtered in large, ARTICLE IN PRESS www.elsevier.com/locate/idairyj 0958-6946/$-see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.idairyj.2004.07.018 à Corresponding author. Tel.: +39079387228; fax: +39079389450. E-mail address: izcscas@tin.it (M. Addis).