PERSISTENCE OF LISTERIA IN RAW MILK. E. Fistrovici*,P. Slade and D.L. Collins·Thompson, Department of FoodScience/Environmental Biology, University of Guelph, Guelph,Ontario NIG 2WI.

Thirty-six farm bulk milk samples from across Ontario were foundto contain Listeria. Thirty-four were monitored at 2 month inter­vals over an eight month period. Nineteen of these samples werepositive at the first retest but only seven at the second. Three ofthe seven were positive at the third resampling but negative at thefourth. Positive retest samples often yielded similar strains or spe­cies as originally isolated but on occasion, different serotypes ofL. monocytogenes or listerial species were found. Listerial popula­tions in raw milk did not appear particularly stable or persistent.

PRODUCTION AND CHARACTERIZATION OF ESTERASESAND LIPASES OF LACTOBACILLUS CASE/GROUP. S.Y. Lee,B.H. Lee* and S. Kermasha, Department of Food Science andAgricultural Chemistry, Macdonald College of McGiII University,Ste. Anne de Bellevue, Quebec H9X ICO, and Agriculture CanadaResearch Centre, St. Hyacinthe, Quebec.

Esterases/lipases are known for their function of flavor develop­ment during cheese maturation. However, their utilities and speci­ficities have not been studied in detail. The strains of Lactobacilluscasei which produced strong esterases and lipases were selected byAPIZYM (microenzyme) test. Various methods of cell lysis weretried to obtain maximum disintegration but grinding mill and frenchpress gave the best results. Four strains were compared for theirgrowth and enzyme production at various growth stages. The speci­ficity of the enzymes were determined by chromogenic substratesand by measuring volatile fatty acids from lipid hydrolysis with highresolution GLe. The paper also describes the purification andcharacterization leading to preparations suitable for specific studies.

RADIATION-INDUCED THERMAL SENSITIVITY AND ITSPERSISTENCE IN CLOSTRIDIUM SPOROGENES SPORES.K. Shamsuzzaman*, B. Payne and J. Borsa. Atomic Energy ofCanada Ltd. Research Company, Pinawa, Manitoba ROE ILO.

Combined effects of irradiation (5.5 kGy) and heat treatment(95.5° and 99°C) on Clostridium sporogenes in phosphate buffer(pH 7.0) were higher if irradiation was followed by heat treatmentthan when treated in the reverse sequence, indicating a radiation­induced thermal sensitization of the spores. Freeze-dried spores andthose suspended in phosphate buffer or distilled water, when irradi­ated at O°C maintained this increased thermal sensitivity for at least5 weeks when held at either 4°C or 25°C during the interval betweenirradiation and heating. The possibility of radiation-induced ther­mal sensitization of spores in other suspension media includingselected foods is being investigated. These results have practical impli­cations for the food processing industry.

HYDROPHOBIC BEHAVIOR OF SELECTED BACILLUSSPORES. D. Melnyk, G. Blank* and M.A.H. Ismond, Food ScienceDepartment, University of Manitoba, Winnipeg, Manitoba R3T2N2.

The hydrophobic behavior of B. subtilis, B. licheniformis, B.coagulans and B. stearothermophilus spores was examined usingboth bacterial adherence to hydrocarbons and hydrophobic inter­action chromatography. In water, all species with the exception ofB. licheniformis exhibited low adherence to hexadecane. In addi­tion, no populations exhibited substantial adherence to hydropho­bic Sepharose derivatives when suspended in water. In the presenceof ammonium sulfate or sodium chloride, adherence to hydrocar­bons and to hydrophobic Sepharose derivatives increased. With theexception of B. coagulans, the adherence levels determined usingthe two methods exhibited good correlation for spores suspendedin ammonium suI fate.

CURRENT TRENDS IN FOOD BIOTECHNOLOGY ANDGENETIC ENGINEERING. B.H. Lee, Agriculture Canada FoodResearch Centre, St. Hyacinthe, Quebec, and Department of FoodScience and Agricultural Chemistry, Macdonald College of McGiIlUniversity, Ste. Anne de Bellevue, Quebec H9X ICO.

Much interest has been shown recently in the field of food biotech­nology due to its numerous economic benefits. The paper reviews

Can. Inst. Food Sci. Technol. J. Vo!. 21. No. 4. 1988

the novel developments of biotechnology, as it relates to foodproduction and processing covering food enzymes and other bioin­gredients, various aspects of genetic engineering, bioengineering,biosensors and plant tissue culture techniques. Four main areas ingenetic engineering of much interest to food industry: animal andplant production, food additives, processing aids and starter cul­tures, and single cell protein are briefly discussed. Recent advancesin genetic engineering of lactic acid bacteria, fungi and yeasts toimprove microbial strains for food fermentation and to enhanceproduction of enzymes and food additives are examined. Promisesand limitations of these new technologies are highlighted.

INTESTINAL EFFECTS OF NONABSORBABLE NEOSUGAR.J.V. HilI* and A.V. Rao, Department of Nutritional Sciences.University of Toronto, Toronto, Ontario, M5S IA8.

Neosugar, a mixture of fructooligosaccharides, is being usedincreasingly in food and pharmaceutical products in Japan and otherparts of the world. It is reported to be nondigestible by humans buteffective in improving the intestinal microflora composition. Theobjective of this project was to study the effect of feeding Neosu­gar on intestinal pathology and microbiology in rats, and to com­pare the route of its administration. Male Fisher F344 rats were fedNeosugar at levels of 0.5010, 1.0% and 5.0% for two weeks or givendaily gavages to deliver an amount of Neosugar that is equivalentto a daily consumption by the rats on 1.0%, 5.0% and 15.0% inthe diet. A significant elevation in the counts of Bifidobacteria anda reduction in caecal pH were noted when fed the Neosugar. Strep­tococcus counts did not vary significantly. Upon gavaging the Neosu­gar the magnitude of decrease in the caecal pH was greatly magni­fied. Histo-pathological changes in the ultrastructure were alsoobserved including hyperplasia, vesicular nuclei, mucin depletionand infolding of the lamina propria. These changes followed a doseresponse trend.

A NOVEL MECHANISM FOR THE FORMATION OF EARLYMAILLARD POLYMERS. V.A. Yaylayan*, Department of FoodScience and Agricultural Chemistry, Macdonald College of McGiIlUniversity, Ste. Anne de Bellevue, Quebec H9X lCO; and P. Sporns,Department of Food Science, University of Alberta, Edmonton,Alberta T6G 2M8.

The study of the mechanisms involved in the unimolecular frag­mentations of I-(amino acid)-I-deoxy-D-fructoses (Amadori com­pounds) under electron impact mass spectrometric conditions, indi­cates the prescence of reactive intermediates capable of acting asmonomers in a condensation or addition polymerizations. The reac­tive intermediates have been identified as pyrylium cations havingamino acid moieties as their side chains, thus, in addition to theirpronounced electrophilic reactivity the side chain imparts anucleophilic character to the pyrylium cations, making them suita­ble candidates for monomers. The repeating unit in the early Mail­lard polymers might be attributed, therefore, to the products formedfrom the polymerization of pyrylium cations, known to possess elec­trophilic reactivity at positions 2, 4 and 6, which enables them toadd nucleophiles in these positions, forming pyrans (units of theearly Maillard polymers), the pyrans thus formed are susceptibleto thermally allowed electrocyclic ring opening, giving rise to con­jugated products, which, then can recyclize regiospecifically, lead­ing to new carbocyclic and heterocyclic units, such as furans, pyra­zoles, thiophenes, etc.

EFFECT OF CATECHIN AND ACETALDEHYDE ONCOLOUR OF CYANIDIN 3·GLUCOSIDE IN AQUEOUSMEDIA. R.e. Green* and G. Mazza, Department of Food Science,University of Manitoba, Winnipeg, Manitoba R3T 2N2; and FoodScience and Technology Laboratory, Agriculture Canada ResearchStation, Morden, Manitoba ROJ 110.

The effect of catechin and acetaldehyde on colour intensity andstability of cyanidin 3-glucoside in aqueous media was studied byUV/vis spectrometry and high performance liquid chromatography.Presence of catechin and acetaldehyde in cyanidin 3-glucoside solu­tion of pH 3.5 caused a marked increase in colour intensity duringstorage. Visible spectra of colour intensified solutions displayed abathochromic shift and an increase in absorbance. The colourchanges were attributed to molecular condensation involving cate­chin, acetaldehyde and anthocyanin.

Abstract / 367