Role of orthophosphate in growth and extracellular proteinase production in the psychotroph, pseudomonas fluorescens

Les bacteries sont pre-incubees a 36° C pour 24 heures. Les bacteries sont ensuite diluees dans la peptone, et incubees a 36° e. Des echantillons sont preleves a des temps variables. La concentration de catalase est determinee par la methode de flottaison du disque a l'aide du catalasemetre et la concentration de bacteries est faite par une evaluation des comptes totaux (CFu/ml). Il existe une correlation entre la concentration de bacteries et la concentration de catalase exprimee en temps de flottaison. THE SHELF-LIFE OF VACUUM OR NITROGEN-PACKAGED PASTRAMI. Laleye, L.e., R.E. Simard, B.H. Lee, L. Carmichael and R. Holley, Departement de Sciences et technologie des aliments, Universite Laval, Quebec GIK 7P4, Centre de recherche en nutrition et Agriculture Canada. The effects of packaging and storage conditions on the microflora, sensory and organoleptic analysis of pastrami packaged in vacuum or nitrogen atmosphere were determined by subjecting it to four storage temperatures ( - 4,0,3 and 7° C) over7 weeks. Numbers oflactobacilli, psychotrophic and anaerobic bacteria in vacuum or nitrogen-packaged samples subjected to the various treatments were seldom significantly (P >0,05) different. Growth ofyeasts and molds was retarded by nitrogenpackaging in samples stored at 3 and T C as compared with similarly treated vacuum-packaged samples. The sensory changes became prominent as the storage or temperature was increased and this was closely related to the increased number of lactobacilli and a drop of pH. Few significant differences were found in discoloration and exudate losses between vacuum or nitrogen-packaged samples. SOURCE OF KLEBSIELLA PNEUMONIAE IN ALFALFA AND BEAN SPROUTS. Park*, e.E., Z.K. Stankiewicz and K. Weiss, Bureau of Microbial Hazards, Food Directorate, Health Protection Branch, Health and Welfare Canada, Ottawa, Ontario KIA OL2. All market sprouts examined were contaminated with K. pneumoniae (l03-106 /g). This may constitute a health hazard because strains of the species can cause enteritis. The source of contamination was determined as follows: I) All of 4 brands of alfalfa seeds and 7/10 mung beans were positive for K. pneumoniae (10'-10 3/100 g). 2) In developed sprouts, the counts were 104 _106 /g, while surface counts of crocks and metal plates in contact with the sprouts were 105 -10 7/100 cm 2 . 3) No K. pneumoniae were found in tap water. 4) Chlorination of seeds (100 ppm Cl z for 24 h) and heat sterilization of containers resulted in Klebsellia-free products but had no effect on growth and organoleptic quality of the sprouts. PRODUCTION OF BUTANOL FROM ACID WHEY. Welsh*, Frank W., and Ivan A. Veliky, Division of Biological Sciences, National Research Council, 100 Sussex Drive, Ottawa, Ontario KIA OR6. Experiments were conducted to determine if Clostridium acetobutylicum strain 824 could produce butanol and acetone from the lactose present in the acid whey. Comparisons were made using either autoc1aved whey or non-autoclaved whey as the substrate in completely mixed or static fermenters. Results showed that maximum production occurred with autoclaved whey, when pH was adjusted to 6.0, in a static fermenter. Solvent production was: 0.626% wlv butanol, 0.044% w/v acetone and 0.217% w/v ethanol after 120 h of fermentation at 3T C under anaerobic conditions. Fifty percent of the available lactose was utilized during the fermentation. PRODUCTION D' ACIDE LACTIQUE A PARTIR DE PERMEAT DE LACTOSERUM PAR L. HELVETlCUS. Roy, D.', J. Goulee et A. LeDuyz, Departement de Sciences et technologie des aliments " Departement de Genie chimique Z , Universite Laval; et Agriculture Canada, Saint-Jean-sur-Richelieu, Quebec. L'effet de certaines conditions de culture a ete etudie au cours de la fermentation du permeat de lactoserum supplemente en ETM (0,5%) par Lacto bacillus helveticus var. milano ensemence a 1% (ViV). Nous avons observe que la production d'acide lactique apres 24 h etait de 3, I% pour une fermentation ensemencee avec un inoculum cultive dans du lait ecreme (12%) et de 1,6% pour une culture ensemencee avec un inoculum cultive dans du permeat de lactoserum (6,5% MiV). Ces resultats suggerent que le passage d'un milieu pauvre comme le permeat de lactoserum est responsable d'une reaction de decouplage provoquant une stimulation importante de la production d'acide lactique. Subventionne par le Conseil des recherches et services agricoles du Quebec.

xvi / Affaires de I'Institut

SCANDINAVIAN ROPY MILK - CULTURE IDENTIFICATION AND SLIME CHARACTERIZATION. Macura*, D., and P.M. Townsley, Department of Food Science, Faculty of Agricultural Science, University of British Columbia, Vancouver, British Columbia V6T 3A2. The lactic acid bacteria which characterize Scandinavian Ropy Milk were classified and identified as strains of both Streptococcus Lactis and Streptococcus cremoris. The viscous exudate produced by these organisms was identified as a glycoprotein with the following composition: 46.7% protein, 9.25% protein bound hexoses, 19.8% fucose and trace amounts «1%) sialic acid. The amino acid composition of the glycoprotein showed similarities to the protein found in the whey growth medium. In addition to the above sugars, the carbohydrate fraction revealed the presence of rhamnose, xylose, xylitol, mannose, galactose and glucose. MYCOLOGICAL QUALITY OF COWPEAS DURING LONG-TERM ST-0RAGE. Beuchat*, L.R., Department of Food Science, University of Georgia Agricultural Experiment Station, Experiment GA 30212 USA. The survival of mycoflora naturally present on cowpeas (Vigna unguiculata) as well as Apergillus flavus inoculated on cowpeas and cowpea flour was monitored over a long-term storage period. The combined effects of water activity (a w), temperature and atmospheric gas content were evaluated. The a w (0.6S and 0.44) did not influence the survival ofA.flavus at 4 and 21 ° C, where remarkably high viability was observed after 20 months of storage. At 37° C, loss of viability was greaterthan at 4 or 2r C; a more rapid reduction in viable conidiospores was noted at aw 0.66 than at a w 0.44, regardless of the form of the cowpeas, when storage was at 37° C under atmsopheric gas or vacuum. When packaged under an atmosphere of nitrogen, total mycoflora and A. flavus populations maintained highest viability. The influence of a wand temperature on survival of these populations was minimal when cowpeas were stored under a nitrogen atmosphere. EVOLUTION MICROBIOLOGIQUE EN FONCTlON DE L' Aw DE SAUCISSES DE TYPE FRANKFURTERS EMBALLES SOUS VIDE. Lacroix*, C., et F. Castaigne, Departement de sciences et technologie des aliments, Universite Laval, Quebec. Le comportement microbiologique d'echantillons de saucisses frankfurters dont les a w, adjustees en incorporant du glycerol dans la recette de fabrication, variaient de 0,976 a 0,871, a ete etudie pendant une periode d'entreposage de 9 semaines a 9-10° e. Une baisse de l' aw dans I'intervalle de 0,976 a 0,927 a entraine un fort ralentissement du developpement bacterien et une modification de la flore predominante. Pour des a w inferieures a 0,906, nous avons observe une dimunition du nombre de bacteries. Seuls, les echantillons ayant des a w de 0,959 a 0,927 ont supporte une croissance des staphylocoques. Cette etude a demontre qu'une faible dimunition de l'aw, agissant en synergie avec les facteurs intrinseques et extrinseques du produit, augmente fortement la duree de vie de celui-ci. L'exploitation de ce concept permettrait le developpement de techniques de conservation basees sur des conditions moins intensives (parexemple la dimunition ou l'elimination des nitrites de la fabrication), tout en conservant la meme securite vis-a-vis du controle des microorganismes pathogenes de I'aliment. ROLE OF ORTHOPHOSPHATE IN GROWTH AND EXTRACELLULAR PROTEINASE PRODUCTION IN THE PSYCHOTROPH, PSEUDOMONAS FLUORESCENS. Cholette*, H. and R.e. McKellar, Food Research Institute, Agriculture Canada, Ottawa, Ontario KIA OC6. Phosphate is an important component of milk, therefore it was of interest to examine the ability of this compound to regulate growth and extracellular proteinase production by a common psychotroph, Pseudomonasfluorescens. In mineral salts medium containing an inducer, 1-2 mM orthophosphate was essential for maximum growth and proteinase production. Sodium ammonium phosphate, ring and straight chain polyphosphates could not substitute as phosphate sources. Dialysis of a crude, acid soluble supematant from skim milk removed phosphate but reduced the proteinase inducing capability. Proteinase production was strongly inhibited by excess orthophosphate with 50% inhibition being achieved at a concentration of 28 mM. These results suggest that orthophosphate stimulates and inhibits extracellular proteinase production. J. InS1. Can. Sei. Teehnol. Aliment. Vol. 16. No. 3. 1983