Effect of proteolytic starter cultures as leavening agents of pizza dough O. Pepe, F. Villani, D. Oliviero, T. Greco, S. Coppola * Dipartimento di Scienza degli Alimenti, Universita` degli Studi di Napoli Federico II, I-80055 Portici, Italy Received 27 July 2001; received in revised form 16 September 2002; accepted 5 October 2002 Abstract Lactic acid bacteria (LAB) and yeasts were selected on the basis of in vitro proteolytic activity against wheat gluten protein and then assayed as leavening agents for pizza dough. Trials were carried out to compare a proteolytic starter (Prt + ), consisting of Lactobacillus sakei T56, Weissella paramesenteroides A51 and Candida krusei G271, and a non-proteolytic starter (Prt À ), consisting of Lb. sakei T58, W. paramesenteroides A58 and Saccharomyces cerevisiae T22. The proteolytic activity of the starter cultures was monitored immediately after mixing of the dough and throughout the fermentation process. The proteolytic activity was assessed by analysing the salt-soluble protein (SSP) and the dioxane-soluble protein (DSP) fractions of the pizza dough by discontinuous SDS-PAGE. Only the Prt + starter exhibited considerable qualitative and quantitative changes in the electrophoretic patterns of the protein fractions extracted. After the fermentation, the Prt + and Prt À doughs were tested to evaluate the influence of the proteolytic activity on the mechanical properties of the dough before and after baking. Indications emerged suggesting an influence of the proteolytic activity on the viscoelasticity of pizza dough. The pizza dough with Prt + strains showed an increase in viscous properties during the fermentation as compared with the Prt À dough. Moreover, an increase in the firmness of the crumb was observed in Prt + baked pizza dough. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Pizza dough; Starter cultures; Leavening; Microbial proteolysis 1. Introduction Microbial activities during leavening of bakery products, essentially involving volume rising, acid- ification and hydrolysis of proteins, have been shown to have extensive technological and sensory implica- tions (Lo¨nner and Preve-A ˚ kesson, 1989; Torner et al., 1992; Stoltz et al., 1993; Martı ´nez-Anaya et al., 1994; Antun˜a and Martinez-Anaya, 1993; Ro¨cken and Voy- sey, 1995; Gobbetti et al., 1995a,b,c; Ro¨cken, 1996; Hammes et al., 1996). Sensorial attributes of bread may be enhanced by the release of nitrogen com- pounds that represent important flavour precursors influencing the overall aroma of the final product (Spicher and Nierle, 1988; Damiani et al., 1996; Schieberle, 1996; Stam et al., 1998). Amino acids released during dough fermentation can also promote growth and metabolic activities of microorganisms (Collar Esteve et al., 1992). Moreover, the proteolysis 0168-1605/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-1605(02)00473-7 * Corresponding author. Tel.: +39-81-2539017; fax: +39-81- 2539407. E-mail address: sacoppol@unina.it (S. Coppola). www.elsevier.com/locate/ijfoodmicro International Journal of Food Microbiology 84 (2003) 319 – 326