Publications

  • Marta Mikš-Krajnik, Yong-Jin Yoon, Hyun-Gyun Yuk
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    ABSTRACT: Volatile organic compounds (VOCs) of naturally aerobically spoiled chicken breast at ambient temperature were analyzed to identify volatiles that can be used as spoilage markers. The headspace solid-phase micro-extraction (HS-SPME) technique coupled with gas GC/MS running in Fast Automated Scan/SIM Type (FASST) mode was applied using 4 SPME fibers of different polarity. All of fibers were able to detect the sulfides methanethiol (MeSH), dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS), the alcohols ethanol (EtOH), 1- and 2-butanol, and 1-butanol isomers, and free fatty acids (FFAs) in the range of C2 to C5. Principal component analysis (PCA) revealed that spoilage in chicken meat is 2-step process. Initially, an increase in amounts of alcohols and FFAs was observed (primary spoilage), followed by an increase in the sulfide content (secondary spoilage). The most promising volatile spoilage markers for chicken breast were EtOH and 3-methyl-1-butanol, followed by acetic acid (C2) and sulfides.
    Food science and biotechnology 02/2015; 24(1). · 0.66 Impact Factor
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    ABSTRACT: Conventional culture detection methods are time consuming and labor-intensive. For this reason, an alternative rapid method combining real-time PCR and immunomagnetic separation (IMS) was investigated in this study to detect both healthy and heat-injured Salmonella Typhimurium on raw duck wings. Firstly, the IMS method was optimized by determining the capture efficiency of Dynabeads(®) on Salmonella cells on raw duck wings with different bead incubation (10, 30 and 60min) and magnetic separation (3, 10 and 30min) times. Secondly, three Taqman primer sets, Sal, invA and ttr, were evaluated to optimize the real-time PCR protocol by comparing five parameters: inclusivity, exclusivity, PCR efficiency, detection probability and limit of detection (LOD). Thirdly, the optimized real-time PCR, in combination with IMS (PCR-IMS) assay, was compared with a standard ISO and a real-time PCR (PCR) method by analyzing artificially inoculated raw duck wings with healthy and heat-injured Salmonella cells at 10(1) and 10(0)CFU/25g. Finally, the optimized PCR-IMS assay was validated for Salmonella detection in naturally contaminated raw duck wing samples. Under optimal IMS conditions (30min bead incubation and 3min magnetic separation times), approximately 85 and 64% of S. Typhimurium cells were captured by Dynabeads® from pure culture and inoculated raw duck wings, respectively. Although Sal and ttr primers exhibited 100% inclusivity and exclusivity for 16 Salmonella spp. and 36 non-Salmonella strains, the Sal primer showed lower LOD (10(3)CFU/ml) and higher PCR efficiency (94.1%) than the invA and ttr primers. Moreover, for Sal and invA primers, 100% detection probability on raw duck wings suspension was observed at 10(3) and 10(4)CFU/ml with and without IMS, respectively. Thus, the Sal primer was chosen for further experiments. The optimized PCR-IMS method was significantly (P=0.0011) better at detecting healthy Salmonella cells after 7-h enrichment than traditional PCR method. However there was no significant difference between the two methods with longer enrichment time (14h). The diagnostic accuracy of PCR-IMS was shown to be 98.3% through the validation study. These results indicate that the optimized PCR-IMS method in this study could provide a sensitive, specific and rapid detection method for Salmonella on raw duck wings, enabling 10-h detection. However, a longer enrichment time could be needed for resuscitation and reliable detection of heat-injured cells.
    International Journal of Food Microbiology 06/2014; 186C:6-13. · 3.16 Impact Factor
  • Marta Mikš‐Krajnik, Andrzej Babuchowski
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    ABSTRACT: Multicolor fluorescence in situ hybridization (FISH) has been applied to detect Lactococcus lactis and Propionibacterium freudenreichii cells in mixed populations in medium and skimmed milk, using epifluorescent microscopy. The 16S rRNA-targeted 18-mer oligonucleotide probes, specific for P. freudenreichii were designed and evaluated. Based on multiple alignments of designed sequences, eight 16S rRNA probes were selected for in vitro studies. The permeabilization protocol was optimized for simultaneous hybridization of propionibacteria and lactococci cells. The probes GLO62 (62-80), PEU64 (64-82) and PFX311 (311-329) were found specific for P. freudenreichii in analysis in vitro. L. lactis cells were labeled with LactV5 (822-840), (S-S-L.lact-0821-a-A-18) probe. The following combinations of oligonucleotide probes: LactV5/GLO62, LactV5/PEU64 and LactV5/PFX311, enabled differentiation of L. lactis and P. freudenreichii cells in culture media and in skimmed milk.This article is protected by copyright. All rights reserved.
    Letters in Applied Microbiology 05/2014; · 1.63 Impact Factor
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    International Journal of Food Science & Technology 01/2014; · 1.35 Impact Factor
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    ABSTRACT: Conventional culture detection methods are time consuming and labor-intensive. For this reason, an alternative rapid method combining real-time PCR and immunomagnetic separation (IMS) was investigated in this study to detect both healthy and heat-injured Salmonella Typhimurium on raw duck wings. Firstly, the IMS method was optimized by determining the capture efficiency of Dynabeads® on Salmonella cells on raw duck wings with different bead incubation (10, 30 and 60 min) and magnetic separation (3, 10 and 30 min) times. Secondly, three Taqman primer sets, Sal, invA and ttr, were evaluated to optimize the real-time PCR protocol by comparing five parameters: inclusivity, exclusivity, PCR efficiency, detection probability and limit of detection (LOD). Thirdly, the optimized real-time PCR, in combination with IMS (PCR–IMS) assay, was compared with a standard ISO and a real-time PCR (PCR) method by analyzing artificially inoculated raw duck wings with healthy and heat-injured Salmonella cells at 101 and 100 CFU/25 g. Finally, the optimized PCR–IMS assay was validated for Salmonella detection in naturally contaminated raw duck wing samples. Under optimal IMS conditions (30 min bead incubation and 3 min magnetic separation times), approximately 85 and 64% of S. Typhimurium cells were captured by Dynabeads® from pure culture and inoculated raw duck wings, respectively. Although Sal and ttr primers exhibited 100% inclusivity and exclusivity for 16 Salmonella spp. and 36 non-Salmonella strains, the Sal primer showed lower LOD (103 CFU/ml) and higher PCR efficiency (94.1%) than the invA and ttr primers. Moreover, for Sal and invA primers, 100% detection probability on raw duck wings suspension was observed at 103 and 104 CFU/ml with and without IMS, respectively. Thus, the Sal primer was chosen for further experiments. The optimized PCR–IMS method was significantly (P = 0.0011) better at detecting healthy Salmonella cells after 7-h enrichment than traditional PCR method. However there was no significant difference between the two methods with longer enrichment time (14 h). The diagnostic accuracy of PCR–IMS was shown to be 98.3% through the validation study. These results indicate that the optimized PCR–IMS method in this study could provide a sensitive, specific and rapid detection method for Salmonella on raw duck wings, enabling 10-h detection. However, a longer enrichment time could be needed for resuscitation and reliable detection of heat-injured cells.
    International Journal of Food Microbiology. 01/2014; 186:6–13.
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    Justyna Borawska, Marta Miks-Krajnik, Małgorzata Darewicz
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    ABSTRACT: The bacterial physiological state, type of interactions and changes in metabolism of Lactococcus lactis and Propionibacterium freudenreichii strains in co-culture were studied in skimmed milk in response to osmotic [3% (w/v) NaCl] and low temperature (10°C) stress during long-term incubation. Changes in the integrity of cell membrane were examined by LIVE/DEAD® BacLight™ staining, and culture viability and bacterial interactions studies were performed with the use of the plate count technique. The profiles of volatile organic compounds were assessed by static headspace-gas chromatography. During the stationary growth phase, the number of LIVE cells with intact membranes was reduced in the presence of NaCl in comparison with control conditions, and a longer adaptation phase was observed at 10°C.The viability of starter cultures was high at ~108 to 109 CFU/ml at the end of the experiment in all tested conditions. Our results point to the possibility of commensalisms interactions between lactic acid and propionic acid bacteria. Prolonged culture incubation contributed to the accumulation of acetoin, and it enhanced acetic acid and propionic acid synthesis during the stationary growth phase of propionic acid bacteria.
    African journal of microbiology research 07/2013; 7(29):3794-3801. · 0.54 Impact Factor
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    ABSTRACT: The changes in the physiological state and metabolism of starter culture in 15kg Swiss–Dutch-type cheese blocks during two-stage ripening were studied. The analyses were performed on samples from three layers of cheese between the rind and the core. Cell membrane integrity, intracellular esterase activity and bacteria culturability were chosen as physiological state indicators. Cheese flavour development was determined by static headspace gas chromatography. During warm room ripening, the number of cells with intact cell membranes and displaying intracellular esterase activity increased. Lactic acid bacteria underwent resuscitation and regained their culturability. A lack of homogeneity within the cheese was noticed in relation to bacterial activity and the volatiles concentration.
    International Journal of Dairy Technology 06/2013; 66(4):562-569. · 1.18 Impact Factor
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    Mikš-Krajnik M.
    Zywnosc: Nauka, Technologia, Jakosc 01/2012; 80(1):45-59. · 0.31 Impact Factor
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    ABSTRACT: The focus of this study was to monitor the survival of populations and the volatile compound profiles of selected Lactobacillus strains during long-term incubation in milk. The enumeration of cells was determined by both the Direct Epifluorescent Filter Technique using carboxyfluorescein diacetate (CFDA) staining and the plate method. Volatile compounds were analysed by the gas-chromatography technique. All strains exhibited good survival in cultured milks, but Lactobacillus crispatus L800 was the only strain with comparable growth and viability in milk, assessed by plate and epifluorescence methods. The significant differences in cell numbers between plate and microscopic counts were obtained for L. acidophilus strains. The investigated strains exhibited different metabolic profiles. Depending on the strain used, 3 to 8 compounds were produced. The strains produced significantly higher concentrations of acetic acid, compared to other volatiles. Lactobacillus strains differed from one another in number and contents of the volatile compounds.
    The Journal of Microbiology 08/2010; 48(4):445-51. · 1.28 Impact Factor
  • Warmińska-Radyko I., Sielawa H., Mikš-Krajnik M.
    Polish Journal of Food and Nutrition Sciences 01/2010; 60(4):363-368.
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    ABSTRACT: The growth and metabolism of Lactococcus strains were studied in milk with an NaCl presence and at 10oC. The viability of bacteria was assessed by the LIVE/DEAD® BacLight™ assey and by plate counts. The gas-chromatography technique for the determination of volatile-free fatty acid profiles in milk was used. It was calculated that depending on the strain, conditions performed and incubation time, plate counts were from 0,5 to 6 log units lower than LIVE/DEAD counts. The LIVE/DEAD method allowed to exhibit a slight influence of selected factors on the growth of Lactococcus, providing delicate differences between live and dead cell counts at investigated conditions. It was shown that each strain contributed to the specific profile of volatiles of milk. Depending on the strain and conditions, from 3 to 9 acids were established. Production of acetic acid occurred early in the fermentation, whereas other acids were formed between day 28 and 42 of incubation.
    Milchwissenschaft 01/2010; 65(1):32-35. · 0.23 Impact Factor
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    Mikš-Krajnik M., Warmińska-Radyko I.
    Medycyna weterynaryjna 05/2008; 64(4):623 – 628. · 0.20 Impact Factor
  • Polish Journal of Natural Science 12/2007; 22(4):733-741.
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    Marta Miks-Krajnik, Wioleta Chajęcka-Wierzchowska
    Zeszyty Naukowe Akademii Rolniczej im. Hugona Kołłątaja w Krakowie. 01/2007; 444(93):513-518.

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