Proteolytic activity of Staphylococcus xylosus strains on pork myofibrillar and sarcoplasmic proteins and use of selected strains in the production of 'Naples type' salami

Abstract

Aims: The aim of this study was to determine the proteolytic activities of Staphylococcus xylosus strains on sarcoplasmic and myo®brillar proteins in order to evaluate the suitability of selected strains as starter cultures in the processing of a dry fermented pork sausage. Methods and Results: The proteolytic activity of 27 strains of Staphylococcus xylosus on sarcoplasmic and myo®brillar proteins was determined by agar plate method, o-phtaldialdehyde (OPA) spectrophotometric assay and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Four strains were selected for the formulation of six starter cultures to use in the production of`Naples type' salami. The proteolytic contribution of starters was determined by SDS-PAGE, comparing the protein pro®le of inoculated sausages with that of uninoculated sausages after 0, 15 and 33 days of ripening. The results showed that the proteolytic activity of some strains, determined by the agar plate method, were not con®rmed by electrophoretic and spectrophotometric assays. In fact, of 24 strains of Staphylococcus xylosus able to hydrolyse muscle protein extracts on agar plate, only 12 strains were shown to change SDS-PAGE pro®le of pork proteins. The SDS-PAGE pro®le of sarcoplasmic proteins extracted from all sausages showed that the major changes were produced with starters S3, S4 and S5 after 15 days of ripening. Also myo®brillar proteins undergo major changes after 15 days of ripening and the protein pro®les showed the same pattern in all samples, except for the sausages produced with starter S4. Conclusions: The results of this work showed that the muscle protein extracts hydrolysis test is suitable for preliminary screening of Staphylococcus xylosus strains on the basis of their proteolytic activity. However, evaluation of muscle protein hydrolysis in a food model system could then be more appropriate for selecting micro-organisms for use as starter cultures for fermented sausages. Signi®cance and Impact of the Study: The potential of the ®ndings is discussed with reference to the formulation of starter cultures for the dry fermented sausages production.

Effects of pure starter cultures on physico-chemical and sensory quality of dry fermented Chinese-style sausage

“…Initially, there were no signifi cant differences in a w among all sausages but after 24 days of ripening decrease in a w became signifi cant (p<0.05) in control and in S. xylosus-12 inoculated samples. The fi nal a w found in Chinese-sausage was 0.79-0.83, which is lower than the value reported in Western type of dry fermented sausages (Beriain et al 1993, Lizaso et al 1999, Mauriello et al 2002. The excessive loss in moisture during long ripening resulted in lower a w in such dry sausages.…”

“…LAB are reported to accelerate ripening time, improve colour and fl avour profi le, inhibit pathogenic and spoilage bacteria by producing lactic acid and bacteriocin, thereby improving the overall quality and keeping quality of products (Bacus 1986, Con and Gökalp 2000, Erkkilä et al 2001, Amézquita and Brashears 2002, Fadda et al 2002. Staphylococci, on the other hand, have nitrite reductase, catalase positive, lipolytic, proteolytic and amine oxidase characteristics (Miralles et al 1996, Gardoni et al 2002, Mauriello et al 2002, which could produce important volatiles to generate fl avour components in such dry fermented sausages (Søn-dergaard andStahnke 2002, Olesen et al 2004).…”

Mesophilic and Psychrotrophic Bacteria from Meat and Their Spoilage Potential In Vitro and in Beef

“…After incubation, the agar plates with proteins were removed from petri dishes and stained for 5 min in 0.05% (wt/vol) Brilliant Blue R (Sigma) in methanolacetic acid-distilled water (50:10:40). After destaining in methanol-acetic acidwater (25:5:70), the presence of a clear zone surrounding the inoculated wells indicated proteolytic activity (42).…”

Microbial Ecology of the Soppressata of Vallo di Diano, a Traditional Dry Fermented Sausage from Southern Italy, and In Vitro and In Situ Selection of Autochthonous Starter Cultures

“…The nitrate and nitrite content was expressed in milligrams per kilogram of meat. For the proteolytic activity analyses the sarcoplasmic and myofibrillar proteins were extracted according to the method described by Mauriello et al (35) and the protein concentrations were determined using a Bio-Rad protein assay with bovine serum albumin as the standard. The extracts were diluted to a final concentration of 1.77 mg ml Ϫ1 , and SDS-PAGE was performed as described above.…”

“…The physiological and technological properties of the main groups of bacteria involved in the fermentation of dry curedmeat products (i.e., bacteriocin production, proteolysis, lipolysis, and nitrite and nitrate reductase and probiotic properties) have often been studied (2,8,9,23,24,30,31,35,36,42,43,50,51,52,55,58). However, in most cases the selection and technological characterization of the cultures are based on assays performed in vitro, while more information could be gathered if the same properties were tested in a real meat fermentation system.…”