Production of Extracellular Enzymes by a Pyoverdine-Deficient Mutant of Pseudomonas Fluorescens

plate pasteurizer unit. Fifteen strains of Y. enterocolitica and Y. enterocolitica-like species were suspended in whole milk to a final concentration of 105 cells/ml. The inoculated milk equilibrated overnight at 4°C was processed at temperatures ranging from 60°C to noc at a mean holding time of 17.6 s. Triplicated trials failed to show survival of Yersinia at or above 63°C. Mixtures of both Y. enterocolitica and Y. enterocolitica-like species showed a 3 10glO reduction at 60°C. SEQUENTIAL USE OF STREPTOCOCCI AND LACTOBACILLI TO CONTROL THE QUALITY OF EXPERIMENTAL CHEDDAR CHEESE. L.e. Laleye*, R.E. Simard and R.E. Holley, Departement de Science et Technologie des alimentaires, Centre de recherche en nutrition, Quebec et Centre de recherche sur les aliments, Ottawa, Ontario. Various strains of homo- and heterofermentative lactobacilli isolated from Cheddar cheese were added to milk with a commercial Streptococcus culture to produce Cheddar cheese. The heterofermentative lactobacilli L. brevis and L. jermentum led almost always to the development of fruity flavors, openness and late-gassing within 10 months of aging. Cheddar cheese produced using combined cultures of heterofermentative lactobacilli and L. casei-casei or L. caseipseudoplantarum did not exhibit gas formation and openness. The overall grading scores were not higher than for the control cheese without lactobacilli. A definite correlation was found to exist between the lactobacilli used and the flavors of the cheese. The controlled acidity development during cheese making, the fat, the salt in moisture content of the cheeses were not affected. PRODUCTION OF EXTRACELLULAR ENZYMES BY A PYOVERDINE-DEFICIENT MUTANT OF PSEUDOMONAS FLUORESCENS. R.e. McKellar* and H. Cholette, Food Research Centre, Research Branch, Agriculture Canada, Ottawa KIA OC6. Synthesis of extracellular proteinase and lipase by a mutant of P. jluorescens deficient in the ability to produce the iron-chelating pigment, pyoverdine, was examined. Proteinase production by the mutant on several laboratory media was similar to that of the parent. Lipase secretion by the mutant in mineral medium was < 10070 of that found with the parent strain. Addition of partially purified pyoverdine resulted in a 2.5- and 5-fold stimulation of lipase production on mineral medium and Nutrient Broth, respectively. The results suggest that pyoverdine is necessary for maximum lipase synthesis by psychrotrophs. REACTIV ATION OF ALKALINE PHOSPHATASE IN CREAM AND BUTTER. R.C. McKellar* and H. Cholette, Food Research Centre Research Branch, Agriculture Canada, Ottawa KIA OC6. Reactivation of alkaline phosphatase was noted in 32% cream treated at 70-90°C for 16 s after incubation at 34°C for I h in the presence of magnesium ions. Reactivation was apparant at noc, and increased in proportion to increased temperature. EDTA (0.5 mM) effectively prevented reactivation, but had little effect on alkaline phosphatase activity. When butter manufactured from cream heated at 85°C for 16 s was melted at 40°C, reactivation increased with time. Reactivation was not observed when a solid butter sample was added to pre-warmed assay buffer.

GROWTH PHASE AND CULTURE MEDIUM AFFECTING EXTRACELLULAR PROTEINASE PRODUCTION FROM PSEUDOMONAS FRAGI ATCC 4973. R. Myhara* and B.J. Skura, Department of Food Science, University of British Columbia, V:>ncouver, British Columbia V6T 2A2. Pseudomonas jragi ATCC 4973 was cultured in liquid and on solid growth medium. Extracellular proteolytic enzyme production and cellular growth were monitored. Results showed that in liquid medium exponential growth began at 8h while on solid medium exponential growth commenced at 4h. Proteolytic enzyme in liquid first appeared at 26h while on solid enzyme was detected at 4h. Scanning and transmission electron microscopy showed extracellular particles shed by cells grown on solid medium but not from cells grown in liquid medium. Extracellular particle numbers correlated with enzyme production. 324 / Abstract

FOOD BIOTECHNOLOGY RESEARCH & DEVELOPMENT; THE ROLE OF ST-HYACINTHE FOOD RESEARCH CENTRE (AGRICULTURE CANADA). B.H. Lee, Agriculture Canada Food Research Centre, St-Hyacinthe, Quebec J2S 8E3 and Department of Food Science & Agriculture Chemistry, Macdonald College of McGill University, Ste. Anne de Bellevue, Quebec H9X ICO. Agriculture Canada has recently opened its new $36 million (12,000 square metre) Food Research facility at St-Hyacinthe in Quebec. The main function of the research centre will be to carry out basic research in conjunction with the Canadian food industry and to develop new products and technologies for domestic and international markets. Currently, basic research is being done on enzyme technology, biotechnology, food formulation, irradiation, thermal extrusion, freezing, canning and packaging. Among the initial biotechnology projects under investigation are traditional food fermentations as well as novel biotechnology research in enzymology, genetic engineering, tissue culture and bioengineering. This paper will review important priorities of the research centre in the area of food biotechnology. Results on cloning of glucoamylase (Saccharomyces diastaticus) and of lactase (Streptococcus thermophiIus) in Saccharomyces cerevisiae will be presented.

QUANTITATIVE DETERMINATION OF VOLATILE FLAVOUR COMPOUNDS IN BEER. E.C.-H. Chen* and G. Hu, Technical Centre, Molson Breweries of Canada Limited, Mississauga, Ontario L5L 119. With the aim to ultimately establish some objective means for defining and measuring beer flavour quality, a semiautomatic method has been developed to quantify the major volatile compounds in beer. The method involves a dynamic headspace (purgeand-trap) sampling technique, cryogenic focusing the enriched volatiles and high resolution gas chromatography. Prior to purging, beer sample is highly diluted to reduce the possible matrix effect and foaming problem. 2-Butanol and hexyl acetate are used as internal standards to properly reflect the whole range of volatility of compounds interested. The method is rather sensitive and its precision is generally better than 5%.

STUDIES OF IRAQI TRUFFLES. II. PROTEIN EXTRACTABILITY. S.J. Toma*, A.K. Aziz and M.M.A. Al-Shabibi, Department of Food Science, University of Baghdad, College of Agriculture, Abu-Ghraib, Baghdad, Iraq. Total nitrogen and non-protein nitrogen in both varieties of Iraqi truffles were determined. Several attempts were made to extract total nitrogen at different pH levels of 2,7 and II and the higher extractability was obtained at alkaline pH (2N NaOH). Different concentrations of sodium chloride solution were also used and the result showed the highest extractability at 1% NaCI level. Also different concentrations of Na-hexametaphosphate solutions were used and it was found that the best concentration used was 1%. Protein solution of truffle was concentrated by ultrafiltration using Amicon membrane. Samples of the ultrafiltrate were analyzed by gel filtration method using Sephadex G-100 and two major peaks were obtained. These peaks were electrophoretically analyzed.

CONTINUOUS PEPTIDES PRODUCTION FROM MILK PROTEINS HYDROLYSIS. J.e. Vuillemard*l, S. Terrel, M.A. Vijayalakshmi3, J. Goulet l and 1. Amiot l , 1Departement de Sciences et Technologie des Aliments, Universite Laval, Quebec GIK 7P4; 2I.N.R.A., 65 rue de Saint-Brieuc, 35 042 Rennes, France. The continuous peptides production from butter milk proteins hydrolysis by extracellular proteases from free and immobilized growing Serratia marcescens cells was carried out in a bioreactor. The results showed the cell population was stable, even at high dilution rates. The hydrolysis varied as a function of the residence time and decreased as the dilution rate increased. The large residues were hydrolysed extensively. We obtained the most important production of interesting peptides (from 2 to 10 amino acid residues) in the free cell system when the dilution rate was 0.25 h- I (57% small peptides in the hydrolysate). J. Insr. CUll. 5.;6. Tecl1llol. Aliment. Vol. 20, No.5. ]I}H7