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Indulis SiliņšTHE SURVIVAL <strong>OF</strong> LISTERIA MONOCYTOGENES IN COLD-SMOKED SAUSAGES WITH AND WITHOUT STARTER CULTUREInoculation was prepared from persistent L.monocytogenes strains (serotypes 1/2a and 4b)originally isolated from surfaces and meat products ofthe mother factory (Bērziņš et al., 2007) in Latvia. L.monocytogenes strains were incubated in half-Fraserbase medium for 18 h at 37 °C. The fresh concentratedculture of the selected strains was measured by opticaldensities (densitometer DEN-1B, UK) and preparedwith sterile half Fraser broth (CM0895, SR0166E,Oxoid) to obtain approximately 8.0 lg (cfu mL -1 ), andthen samples of dry sausages inoculated portionally (1mL of inoculate in 100 g of sample) randomly leadingto beginning concentration of 6.0 lg (cfu g -1 ) in thesausage.Ingredients of a 100-kg-cold-smoked-sausageraw material were: pork - 30 kg, beef - 10 kg, bacon35 - kg, structural emulsion - 25 kg. Salt and speciessummary was 3.25 kg and starter culture - 0.02kg (‘Optistart Plus’, prepared by Raps GmbH andCo.KG, Germany). The fermentation and ripeningprocess were carried out in climatic chambers (modelsHR-6000 and HR-9000 ‘Sorgo’ Austria) at 28 °C witha relative humidity of 95% on first 3 days, down to75% RH and 14-15 °C on 4 th to 21 st day.The determination of L. monocytogenes count,cfu g -1 , was done according to Standard ISO 11290-2:1198 A:2005 ‘Microbiology of food and animalfeeding stuffs. Horizontal method for the detectionand enumeration of Listeria monocytogenes. Part 2:Enumeration method’. Each experimental batch wasfree of L. monocytogenes before culture inoculation,detected with standard method. The samples wereanalyzed by numbering L. monocytogenes on 0, 1 st ,3 rd , 5 th , 7 th , 14 th and 21 st days of maturation with thenine-tube most-probable-number (MPN) method.For analysis, 10 g of a carefully mixed cold smokedsausage sample were blended with 90 mL of sterilebuffered peptone water in a laboratory blender(Stomacher 400, Interscience, France) for 1 min.Decimal dilutions were made to obtain samples of 1,0.1, 0.01, 0.001, and 0.0001 g. To determine the MPN,three consecutive dilutions were used. Afterwards, 0.1mL of each target dilution was spread on two LMselectiveplates (PALCAM, Oxoid) and incubated for48 h at 37 °C. For confirmation of L. monocytogenes,five typical colonies from two selective plates at eachsampling time were streaked on sheep blood agarplates and incubated for 24 h at 37 °C. Catalasepositive,gram-positive rods, produced hemolysison sheep blood agar (CAMP-test), were consideredL. monocytogenes (McKellar, 1994). Total count(cfu g -1 ) of L. monocytogenes in cold smoked sausagesamples were calculated with classical formula givenin Enumeration method standard.The determination of LAB count, cfu g -1 , was doneaccording to standard ISO 15214:1998 ‘Microbiologyof food and animal feeding stuffs - Horizontal methodfor the enumeration of mesophilic lactic acid bacteria- Colony-count technique at 30 °C’.pH was measured at the same time as othermeasurements. Three individual pieces of sausageswere measured each time, and then mean pH valuewas calculated. The pH-meter Testo 205 (Testo AGGermany), with automatic temperature compensation,was applied. Meter calibration was done according to2 point method with pH standard solutions 4.01 and7.00.Water activity was measured with PawKit(Decagon) water activity meter. Calibration of devicewas done with saturated NaCl (sodium chloride) 6.0molal standard solution (0.760 a wat 20 °C). Samplesfor water activity measurement were collected inoriginal polyethylene vessels with caps and measuredimmediately after collecting.Statistical analysis. All experiments werereiterated three times, and tests were triplicated. Theresults represent the mean ± standard deviations (SD).Means were compared by Student’s t-test. Differenceswere considered statistically significant when p
THE SURVIVAL <strong>OF</strong> LISTERIA MONOCYTOGENES IN COLD-SMOKED SAUSAGES WITH AND WITHOUT STARTER CULTUREIndulis SiliņšThe measured parameters values on start 0 th day (S) and finishing 21 st day (F)Table 1ParametersL. monocytogenes,lg (cfu g -1 )Total count of lacticbacteria, lg (cfu g -1 )Mean sausage weight, gTime:start (S),finish (F)Samples withstarter cultureSamples withoutstarter cultureS 6.57 ± 0.26 6.83 ± 0.12F 1.42 ± 0.43 2.86 ± 0.36S 5.72 ± 0.18 3.35 ± 0.15F 9.41 ± 0.32 6.95 ± 0.27S 396 ± 0.5 397 ± 0.5F 286 ± 0.5 280 ± 0.5S 347.8 ± 0.40 394.3 ± 0.38Moisture content, g kg -1 F 251.2 ± 0.38 258.8 ± 0.36pH valuesS 5.80 ± 0.018 5.76 ± 0.016F 4.67 ± 0.016 4.59 ± 0.015a wvaluesS 0.963 ± 0.002 0.956 ± 0.002F 0.817 ± 0.003 0.800 ± 0.003S 29.4 ± 0.85 28.4 ± 0.64Salt (NaCl) content, g kg -1 F 39.8 ± 0.75 40.2 ± 0.82Nitrite (NO 2-) concentration, S 14 ± 0.4 14 ± 0.4mg kg -1 F 9 ± 0.3 9 ± 0.3culture accordingly. Losses movement significantly(p
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Volume No. 1Annual 18th Internation
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Research for Rural Development 2012
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ContentsFOOD SCIENCESVETERINARYMEDI
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AGRICULTURAL SCIENCES (CROP SCIENCE
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Mihails Vilcāns, Jūlija Volkova,
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Mihails Vilcāns, Jūlija Volkova,
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Berit TeinEFFECT OF ORGANIC AND CON
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Methane producing bacteria use only
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according to calculations the metha
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CHANGES IN SUGAR CONTENT OF WINTERO
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PERENNIAL GRASSES FOR BIOENERGY PRO
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IMPACT OF SLURRY APPLICATION METHOD
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IMPACT OF SLURRY APPLICATION METHOD
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IMPACT OF ORGANIC PRODUCT EXTRACTS
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IMPACT OF ORGANIC PRODUCT EXTRACTS
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COMBUSTION ABILITY OF ENERGY CROP P
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COMBUSTION ABILITY OF ENERGY CROP P
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RESEARCH OF OREGANO (ORIGANUMVULGAR
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RESEARCH OF OREGANO (ORIGANUMVULGAR
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INFLUENCE OF SOIL MODIFICATION ON C
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INCIDENCE OF POSTHARVEST ROT OF CRA
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INCIDENCE OF POSTHARVEST ROT OF CRA
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PERSPECTIVES ON TRUFFLE CULTIVATION
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FACTORS AFFECTING GOAT MILK YIELDAN
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MILK UREA CONTENT AS INDICATOR FEED
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REHYDRATION KINETICS OF DRIED LATVI
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FOOD SCIENCESPreliminary RESULTS of
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PRELIMINARY RESULTS OF 1-METHYLCYCL
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FOOD SCIENCESSensory PROPERTIES and
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SENSORY PROPERTIES AND CHEMICAL COM
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THE SUITABILITY OF DIFFERENT ROWANB
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CHEMICAL COMPOSITION OF NEW TYPE AG
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FOOD SCIENCESINFLUENCE OF GENOTYPE
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INFLUENCE OF GENOTYPE AND HARVEST T
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ROOT VEGETABLES FROM LATVIA:QUANTIT
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Page 167 and 168: INVESTIGATIONS INTO THE ENHANCEMENT
Page 173 and 174: INFLUENCE OF PACKAGING CONDITIONSON
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Page 177 and 178: FOOD SCIENCESFATTY ACID COMPOSITION
Page 179 and 180: FATTY ACID COMPOSITION OF THE MEAT
Page 181 and 182: FATTY ACID COMPOSITION OF THE MEAT
Page 183 and 184: ANTIMICROBIAL RESISTANCE OFANIMAL P
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Page 197 and 198: VETERINARY MEDICINEMicrobiological
Page 199 and 200: MICROBIOLOGICAL QUALITY OF COWS’
Page 205 and 206: PORCINE CIRCOVIRUS-2 IMPACT ON THEM
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CHILDREN WITH SPECIAL NEEDS FAMILY
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