71A-3

I. Moreno, Tecnolat, Instituto de Tecnologia de Alimentos - ITAL, Avenida Brasil, 2880, Campinas - Sao Paulo, 13070-178, Brazil, V. L. S. Baldini, Centro de Química e Nutrição Aplicada, Instituto de Tecnologia de Alimentos - Ital, Campinas - SP, 13070-178, Brazil, A. G. F. VAN DENDER, Centro de Pesquisa & Desenvolvimento de Laticínios, Instituto de Tecnologia de Alimentos, Av. Brasil, 2880, Campinas, 13070-178, Brazil, A. Vialta, A. L. S. Lerayer, Instituto de Tecnologia de Alimentos - ITAL, Avenida Brasil, 2880, Campinas - Sao Paulo, 13073-001, Brazil, M. T. Destro, Fac. Ciencias Farmaceuticas - USP, Universidade de São Paulo, and S. Lortal, Institut National de la Recherche Agronomique, Rue de Saint Brieuc, 65, Rennes, 35042, France.

This study was aimed at evaluating the interrelationship between autolysis of lactic starter bacteria and the development of proteolysis in Prato cheese. Samples of cheeses from four different regions were ripened under the same conditions (12±2 °C, 4 weeks). Autolysis was detected during ripening by immunoblotting, using antibodies against cell-free extracts from Lac. lactis sp. (Lc-cytosol) and D-lactate dehydrogenase (D-LDH) from Lactobacillus helveticus. Hydrolysis of protein was analyzed by denaturing polyacrilamide gel electrophoresis (urea-PAGE). Amino acid analysis by ion exchange chromatography was carried out using a Dionex DX-300 Amino Acid Analyser. Autolytic activity was influenced by the diversity and variability of the bacterial species contained in the cheeses analyzed, a fact demonstrated by the limited degree of Lac. lactis sp. in all the cheeses and the intense autolysis of Lab. helveticus observed only in the cheeses from origins C and D. The results clearly indicate a positive relationship between autolysis of Lab. helveticus and the development of proteolysis in cheeses C and D. This fact was confirmed by the electrophoretic profile of these cheeses in several stages of the ripening process and which indicated a greater degree of as1-I casein and b-casein degradation as compared to cheeses A and B. The more intense casein degradation in cheeses C and D led to the presence of considerably higher levels of free amino acids from the very early stages of ripening on, particularly in the case of cheese D. However, proteolysis in cheese C evolved at a much slower rate as compared to cheese D, thereby indicating that autolysis in itself is not a determining factor in the acceleration of proteolysis. Variations in the physical-chemical composition (pH, NaCl, and moisture) of the different cheeses had a strong effect on the ripening profile of the cheeses investigated. (Research project funded by FAPESP)

Session 71A, Dairy Foods: General
8:30 AM - 12:00 PM, Tuesday AM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana