Showing papers in "Food Technology and Biotechnology in 2005"

Physico-Chemical Properties, Composition and Oxidative Stability of Camelina sativa Oil

Abstract: Summary Camelina sativa is a cruciferous oilseed plant. With the aim of describing the general characteristics of the oil obtained from the seeds of plants grown in Slovenia and of comparing it to camelina oil from other countries we determined some physico-chemical properties, fatty acid composition, iodine and saponification value and followed its oxidative stability under different storage conditions. The density at 20 °C was (0.927 0.0001) g/cm 3 and the refractive index reached 1.4756 0.0001 at 25 °C. The analysis of fatty acids showed 10.3 % of saturated and 55.8 % of polyunsaturated acids, with 16.9 % of linoleic (C18:2), 35.2 % of -linolenic (C18:33) and 1.6 % of erucic acid (C22:1). Determination of oxidative stability of this highly unsaturated oil revealed that the formation of primary oxidation products was affected by photooxidation. The peroxide value, PV, of fresh oil was (2.38 0.01) meq O2/kg, while after 1 month in daylight at room temperature PV reached (21.0 0.1) meq O2/kg. When stored in darkness PV was (8.12 0.08) meq O2/kg. In the fresh oil, the p-anisidine value, AV, was 6.2 0.1, after 11 months at room temperature 10.4 0.1, and after the same time at 8 °C in darkness 7.1 0.1. Susceptibility to oxidation of camelina oil was measured by the Rancimat test and expressed as the induction period. In fresh camelina oil the induction period was 4.8 h.

Potential Antimicrobial Activity of Red and White Wine Phenolic Extracts against Strains of Staphylococcus aureus, Escherichia coli and Candida albicans

Abstract: Summary The aim of this study was to assess antimicrobial activities of wine phenolic extracts. The potential antimicrobial activity of alcohol-free red and white wine extracts against pathogenic strains of Staphylococcus aureus, Escherichia coli and Candida albicans was studied using the agar well diffusion method. Total phenolic content of wine extracts was determined by the Folin-Ciocalteu method, while their phenolic composition was specified by high performance liquid chromatography and diode array detector (HPLC-DAD). The antimicrobial activity of the tested extracts was related to their total phenolic content. Antimicrobial activity of the tested wine extracts was more effective against S. aureus and less effective against E. coli and C. albicans. Also, C. albicans was resistant to more wine extracts than the two bacterial species studied. The antimicrobial activity and the phenolic composition of the tested white and red wine extracts indicate that some phenolic acids have the potential to inhibit growth of certain pathogens such as S. aureus, E. coli and C. albicans strains.

Coimmobilization of Azospirillum lipoferum and Bacillus megaterium for Successful Phosphorus and Nitrogen Nutrition of Wheat Plants

Abstract: Summary The efficacy of strains of Pseudomonas fluorescens, Bacillus megaterium and Azospirillum spp. in in vitro solubilization of Ca3PO4 was studied. Pseudomonas fluorescens and Bacillus megaterium strains were the most powerful phosphate solubilizers on Pikovskaya (PVK) plates and liquid medium. Azospirillum lipoferum strains showed weak zones of solubilization on the PVK plates. Phosphate solubilization by the tested organisms was accompanied with pH reduction of the culture medium. Maximum pH reduction was 2.8, 1.2 and 0.5 units for Pseudomonas fluorescens, Bacillus megaterium and Azospirillum lipoferum strain 137, respectively. Alginate and agar immobilization of the tested bacteria or coimmobilization of A. lipoferum 137 and B. megaterium significantly enhanced phosphorus solubilization for four consecutive 4-day cycles. In a pot experiment, phosphorus mobilization in wheat (Triticum aestivum L. cv. Beni Swif 1) inoculated with B. megaterium or A. lipoferum 137 as single or mixed inocula (as free or alginate immobilized beads) was studied in presence of Ca3PO4. Wheat inoculated with mixed inocula exhibited high shoot dry weight, total nitrogen (N) yield and the shoot phosphorus content increased by 37 and 53 % compared to the plants inoculated with A. lipoferum and uninoculated ones, used as control, respectively. Maximum nitrogenase activity (measured by acetylene reduction assay) was observed in mixed inoculum treatment, and was increased by 500 and 32 % compared to uninoculated and A. lipoferum inoculated plants. Results demonstrate the beneficial influence of coinoculation of A. lipoferum and B. megaterium for providing balanced N and P nutrition of wheat plants.

Lipase Secretion and Citric Acid Production in Yarrowia lipolytica Yeast Grown on Animal and Vegetable Fat

Abstract: Svetlana V. Kamzolova1*, Igor G. Morgunov1, Andreas Aurich2, Oksana A. Perevoznikova1, Nadezda V. Shishkanova1, Ulrich Stottmeister2 and Tatiana V. Finogenova1 G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, p-t Nauki 5, Pushchino, Moscow region, 142290 Russia UFZ Centre for Environmental Research Leipzig-Halle, Department of Environmental Biotechnology, Permoserstrasse 15, D-04318 Leipzig, Germany

Effect of Growth Medium on Bacteriocin Production by Lactobacillus plantarum ST194BZ, a Strain Isolated from Boza**

Abstract: Summary The cell-free supernatant containing bacteriocin ST194BZ, produced by Lactobacillus plantarum ST194BZ, inhibits the growth of Lactobacillus casei, Lactobacillus sakei, Lactobacillus delbrueckii subsp. bulgaricus, Enterococcus faecalis, Escherichia coli, Enterobacter cloacae and Pseudomonas aeruginosa. Strain ST194BZ produces two bacteriocins, viz. ST194BZ(a) of 3.3 kDa and ST194BZ(b) of 14.0 kDa, based on tricine-SDS-PAGE. Reduction in bacteriocin activity was observed after treatment with proteinase K, trypsin and pronase, but not with catalase and a-amylase. A maximum total bacteriocin activity of 12 800 AU/mL was recorded after 14 h in MRS broth. In MRS broth adjusted to pH=5.5, 6.0 or 6.5, an equal level of bacteriocin production of 12 800 AU/mL was recorded. Optimal production (12 800 AU/ mL) was recorded in the presence of tryptone (20 g/L), a combination of tryptone and meat extract (1:0.6), or tryptone and yeast extract (1:0.6). Growth of strain ST194BZ in the presence of 10 or 20 g/L of D-mannose yielded bacteriocin levels of 12 800 AU/mL. In the presence of 30 or 40 g/L of mannose the activity levels doubled to 25 600 AU/mL. No difference in antibacterial activity was recorded when strain ST194BZ was grown in the presence of 2 g/L of K2HPO4 and 2 g/L of KH2PO4. Concentrations of 10, 20 and 50 g/L of KH2PO4 yielded double activity (25 600 AU/mL). Supplementing MRS with 1 g/L or more glycerol inhibited the production of bacteriocin. Growth in the presence of vitamins did not stimulate bacteriocin production. No plasmids were recorded for strain ST194BZ, suggesting that the genes encoding bacteriocin production are located on the genome.

Purification and Characterization of Tannin Acyl Hydrolase from Aspergillus niger ATCC 16620

Abstract: Summary Tannin acyl hydrolase produced extracellularly by the fungal strain Aspergillus niger ATTC 16620 in solid state fermentation was purified from the cell free culture broth by ammonium sulphate fractionation followed by DEAE–Sephadex A-50 chromatography. SDS-PAGE analysis indicated that the enzyme protein molecular mass was 168 kDa. Enzyme activity was stable up to the temperature of 40 °C and the enzyme activity was optimal at pH=6. Tannase activity was maximal at 0.01 M concentration of the substrate. The addition of metal ions like Zn 2+ ,M n 2+ ,C u 2+ ,C a 2+ ,M g 2+ and Fe 2+ inhibited the enzyme activity. Only K + ions enhanced tannase activity, and an activity of 4.31 U/mL was reported here. Enzyme activity was maximal after 15–20 min of incubation time, with an activity of 3.9 U/mL. Km was found to be 1.03 mM and Vmax=4.25 mmol/min. Since the enzyme is active over a wide range of pH and temperature it could find potential use in the food-processing industry.

New Approach to Inactivation of Harmful and Pathogenic Microorganisms by Photosensitization

Abstract: s of 23rd Congress of Czechoslovak Society for Microbiology, Brno, Slovakia (2004). 31. P.J. Tolstykh, E.F. Stranadko, U.M. Korabaev, A.J. Urinov, M.P. Tolstykh, R.P. Terekhova, M.N. Volkova, V.A. Duvanskii, Experimental study of photodynamic effect on bacterial wound microflora, Zh. Mikrobiol. Epidemiol. Immunobiol. 2 (2001) 85–87. 32. T. Burnst, M. Wilson, G.J. Pearson, Effect of dentine and collagen on the lethal photosensitization of Streptococcus mutans, Caries Res. 29 (1995) 192–197. 33. B. Zeina, J. Greenman, W.M. Purcell, B. Das, Killing of cutaneous microbiology spiecies by photodynamic therapy, Br. J. Dermatol. 144 (2001) 274–278. 34. C.E. Millson, M. Wilson, A.J. MacRobert, G. Bedwell, S.G. Bown, The killing of Helicobacter pylori by low-power laser light in the presence of a photosensitizer, J. Med. Microbiol. 44 (1996) 245–252. 35. P. Gottlieb, H. Margolis-Nunno, R. Robinson, L.G. Shen, E. Chimezie, B. Horowitz, H.E. Benhur, Inactivation of Trypanosoma cruzi forms in blood components with a psoralen and ultraviolet A light, J. Photochem. Photobiol. 63 (1996) 562–565. 36. S. Lustigman, E. Benhur, Photosensitized inactivation of Plasmodium falciparum in human red cells by phthalocyanines, Transfusion, 36 (1996) 543–546. 37. M. Wilson, T. Burns, J. Pratten, Killing of Streptococcus sanguis in biofilms using a light-activated antimicrobial agent, J. Antimicrob. Chemother. 37 (1996) 377–381. 38. M. Wilson, J. Pratten, Lethal photosensitization of Staphylococcus aureus in vitro: Effect of growth phase, serum and pre-irradiation time, Lasers Surg. Med. 16 (1995) 272–276. 39. S. Packer, M. Bhatti, T. Burns, M. Wilson, Inactivation of proteolytic enzymes from Porphyromonas gingivalis using light-activated agents, Lasers Med. Sci. 15 (2000) 24–30. 40. M. Egyeki, G. Turoczy, Z. Majer, K. Toth, A. Fekete, P. Maillard, G. Csik, Photosensitized inactivation of T7 phage as surrogate of non-enveloped DNA viruses: Efficiency and mechanism of action, Biochim. Biophys. Acta, 1624 (2003) 115–124. 41. K. Kassaab, D. Dei, G. Roncucci, G. Jori, O. Coppellotti, Phthalocyanine – photosensitized inactivation of a pathogenic protozoan, Acanthamoeba palestinensis, Photochem. Photobiol. 2 (2003) 668–672. 42. V. Carre, O. Gaud, I. Sylvain, O. Bourdon, M. Spiro, J. Balis, R. Granet, P. Krausz, M. Guilloton, Fungicidal properties of meso-arylglycosylporphyrins: Influence of sugar substituants on photoinduced damage in the yeast Saccharomyces cerevisiae, J. Photochem. Photobiol. 48 (1999) 57–62. 43. T.G. Threes, H.J. Schuitmaker, Photodynamic inactivation of Trichophyton rubrum, J. Photochem. Photobiol. 77 (2003) 556–560. 44. G. Jori, S.B. Brown, Photosensitized inactivation of microorganisms, Photochem. Photobiol. Sci. 3 (2004) 403–405. 45. M. Merchat, G. Bertolini, P. Giacomini, A. Villanueva, G. Jori, Meso-substituted cationic porphyrins as efficient photosensitizers of Gram-positive and Gram-negative bacteria, J. Photochem. Photobiol. 32 (1996) 153–157. 46. N. Komerik, M.Wilson, S. Poole, The effect of photodynamic action on two virulence factors of Gram-negative bacteria, Photochem. Photobiol. 72 (2000) 676–680. 47. Y. Nitzan, A. Balzam-Sudakevitz, H. Ashkenazi, Eradication of Acinetobacter baumannii by photosensitized agents in vitro, J. Photochem. Photobiol. 42 (1998) 211–218. 48. C. Wallis, J.L. Melnick, Photodynamic inactivation of animal viruses: A review, Photochem. Photobiol. 4 (1965) 159– 170. 417 @. LUK[IENE . : Photosensitization: An Overview, Food Technol. Biotechnol. 43 (4) 411–418 (2005)

Production and Partial Purification of a Neutral Metalloprotease by Fungal Mixed Substrate Fermentation

Abstract: Summary Five strains of fungi belonging to Aspergillus sp. were evaluated by casein agar plate assay and a wheat bran-based solid-state fermentation for selecting a neutral protease-producing culture. Based on the results, A. oryzae NRRL 2217 was selected for further studies. Sixteen different agro-industrial residues were evaluated for their potential to serve as a substrate for neutral protease production by this fungal strain. Results showed that a combination of coconut oil cake and wheat bran in the mass ratio of 1:3 was the best substrate for enzyme production. Various process parameters influencing protease production including fermentation time, initial moisture content, and fermentation temperature were optimised. The medium was supplemented with different nutrients in the form of organic and inorganic nitrogen and carbon sources. Supplementation of chitin increased the enzyme production significantly. Ammonium nitrate as inorganic nitrogen supplement slightly enhanced enzyme production. No organic nitrogen supplement was effective enhancer of enzyme production. Fermentation was performed under optimised conditions (initial moisture content V/m = 50 %, temperature 30 °C, 48 h). Partial purification of the enzyme resulted in a 3-fold increase in the specific activity of the enzyme. The partially purified enzyme was characterised by various features that govern the enzyme activity such as assay temperature, assay pH and substrate concentration. The effect of various metal ions and known protease inhibitors on the enzyme activity was also studied. The enzyme was found to be stable in pH range 7.0–7.5, and at temperature of 50 °C for 35 min. By the activating effect of divalent cations (Mg 2+ ,C a 2+ ,F e 2+ ) and inhibiting effect of certain chelating agents (EGTA, EDTA), the enzyme was found to be a metalloprotease.

A shortcut to the production of high ethanol concentration from Jerusalem artichoke tubers.

Abstract: Aspergillus niger SL-09, a newly isolated exoinulinase-hyperproducing strain, and Saccharomyces cerevisiae Z-06, with high ethanol tolerance, were used in a fed-batch process for simultaneous saccharification and fermentation of Jerusalem artichoke tuber mash and flour. S. cerevisiae Z-06 utilized 98 % of the total sugar and produced 19.6 % of ethanol in 48 h. In this process the conversion efficiency of the fermentation of Jerusalem artichoke and the production of ethanol were 90 % of the theoretical ethanol yield and the cost of the production of flour was cut nearly into half.

Microbial Adhesion to Processing Lines for Fish Fillets and Cooked Shrimp: Influence of Stainless Steel Surface Finish and Presence of Gram-Negative Bacteria on the Attachment of Listeria monocytogenes**

Abstract: Summary Microflora adhering to surfaces of processing lines in a shrimp factory and a fish processing plant was identified in situ and adhesion of mixed culture of Listeria monocytogenes and Gram-negative bacteria on stainless steel surfaces (untreated, polished and glass beaded) was studied ex situ. The predominant genus attached to the surfaces was Pseudomonas spp. (66 %) in the shrimp factory and Enterobacteriaceae (27 %) in the fish factory. Shrimp juice was used as an enrichment broth during the study of adhered bacteria. Three different Gram-negative strains and a mixture of Pseudomonas spp. were selected to study their attachment together with L. monocytogenes to stainless steel surfaces. Highest numbers of the attached bacteria were obtained after the contamination with a mixed culture of L. monocytogenes and Serratia liquefaciens. A lower number of bacteria adhered to stainless steel surfaces when mixed cultures of L. monocytogenes and Pseudomonas fluorescens or Aeromonas spp. were tested. No significant differences (p<0.05) were observed in the bacteria attached to differently treated steel surfaces with different roughness (Ra=0.1–0.8 m). Bacterial adhesion increased with longer contact time. Colonisation of L. monocytogenes on stainless steel surfaces was significantly enhanced only in the presence of mixed Pseudomonas spp. These results indicate that smooth surfaces do not necessarily provide hygiene benefits over rougher surfaces.

Detection of adulteration in italian mozzarella cheese using mitochondrial DNA templates as biomarkers

Abstract: Summary Considering the importance of monitoring adulterations of genuine cheeses in the dairy industry, a polymerase chain reaction–based method was developed to detect bovine-specific mitochondrial DNA sequence in Italian water buffalo Mozzarella cheese. DNA was isolated from cheese matrix and governing liquid by organic extractions and kit purifications. Amplifications of a 134-bp fragment were performed with a bovine–specific set of primers designed on the sequence alignment of bovine and buffalo mitochondrial cytochrome oxidase subunit I. The specificity of the primers was tested using DNA from the blood of two species (water buffalo and bovine), which are present together in adulterated Italian Mozzarella cheese. This method reliably detected a content of 0.5 % of bovine milk, making it suitable for routine fraud monitoring.

Antioxidant Activities of Total Pigment Extract from Blackberries

Abstract: Summary Total pigment has been extracted from blackberries and its antioxidant activity against lipid peroxidation and scavenging capacities towards superoxide anion radicals, hydroxyl radicals and nitrite in different in vitro systems have been investigated. The total pigment extract from blackberries (TPEB) exhibited strong antioxidant activity against lipid peroxidation in a linoleic acid model system and scavenging capacities towards superoxide anion radicals, generated by a pyrogallol autoxidation system or by an illuminating riboflavin system, hydroxyl radicals generated by Fenton reaction, and nitrite. Furthermore, the antioxidant activities were correlated with the concentrations of the TPEB. In the test concentration range, the maximum inhibition percentage against linoleic acid peroxidation was 98.32 % after one week’s incubation, and the maximum scavenging percentages for the free radicals and nitrite inhibition in the above reactive systems reached 90.48, 96.48, 93.58 and 98.94 %, respectively. The TPEB is a natural, edible colorant with excellent antioxidant activities and health benefits and it seems to be applicable in both healthy food and medicine.

Influence of Growth Medium on Hydrogen Peroxide and Bacteriocin Production of Lactobacillus Strains

Abstract: Summary This study was conducted to investigate the inhibitory effect of bacteriocin and the production of hydrogen peroxide by four non-starter lactic acid bacteria, Lactobacillus plantarum 2142, Lactobacillus curvatus 2770, Lactobacillus curvatus 2775, Lactobacillus casei subsp. pseudoplantarum 2750 and the probiotic strain Lactobacillus casei Shirota, propagated in de Man Rogosa Sharpe (MRS) and tomato juice (TJ) broth. The methods were a commonly used agar diffusion technique and a microtiter assay method. The best peroxide-producing Lactobacillus strain was selected for screening the inhibitory activity against Listeria monocytogenes, Bacillus cereus, Escherichia coli and the activity of bacteriocins against Lactobacillus sakei and Candida glabrata. All of the investigated lactic acid bacteria (LAB) strains grown in MRS broth produced the highest concentration of hydrogen peroxide ranging from 2–6 g/mL after 72 h of storage. L. plantarum 2142 produced enough hydrogen peroxide already after 24 h at 5 °C in phosphate buffer to inhibit the growth of L. monocytogenes and B. cereus. Crude bacteriocin suspension from the investigated LAB inhibited only slightly the growth of L. sakei, however, the same suspension from MRS completely inhibited the 6-fold diluted yeast suspension. The concentrated bacteriocin suspensions from the both broths inhibited the growth of L. sakei completely. Among the strains, L. plantarum 2142 seemed to be the best peroxide and bacteriocin producer, and the antimicrobial metabolite production was better in MRS than in TJ broth.

Microbial Characterization of Table Olives Processed According to Spanish and Natural Styles

Abstract: Summary A study on the microflora of table olives »Bella di Cerignola«, produced according to Spanish style and natural processing, is presented. The samples (olives and brines) were taken at different fermentation phases; olives, before treatments, were analyzed too. pH was monitored and microbial populations were assessed by standard plate count. Determination of the following microbial groups was carried out: mesophilic bacteria, lactic acid bacteria, Enterobacteriaceae, Pseudomonadaceae, staphylococci, Micrococcaceae and yeasts. In the second phase, the identification of mesophilic bacteria, lactic acid bacteria and yeasts was performed. The amount of lactic acid bacteria and yeasts increased during the storage in all the samples, but no significant differences were observed between the two styles. At the end of fermentation an increase of Pseudomonadaceae cell load was observed, which was absent in the first phase of fermentation. The samples analyzed were extremely unsteady, therefore the addition of starter lactic acid bacteria could standardize olive processing. Lactobacillus plantarum, Bacillus spp. (mainly B. subtilis) and Candida spp. were the predominant species at the end of the processing.

Screening of inexpensive nitrogen sources for production of L(+) lactic acid from starch by amylolytic Lactobacillus amylophilus GV6 in single step fermentation

Abstract: L. amylophilus GV6 was studied for production of L(+) lactic acid in single step fermentation using starchy substrates. Seven types of inexpensive organic nitrogen supplements (flour of pigeon pea, red lentil gram, black gram, bengal gram, green gram, soya bean and baker’s yeast) were evaluated for their potential to replace more expensive commercial nitrogen sources, peptone and yeast extract. Red lentil and baker’s yeast cells were found to be the best alternative nutrient sources of peptone and yeast extract for lactic acid production. L(+) lactic acid yield was about 92 % m(lactic acid)/m(starch) utilized in this study.

Effects of Pure Oxygen on the Rate of Skin Browning and Energy Status in Longan Fruit

Abstract: Summary Postharvest pericarp browning is one of the main problems resulting in reduced shelf life of longan fruit. Experiments were conducted to examine the changes in concentrations of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP), energy charge levels and activities of polyphenol oxidase (PPO) and peroxidase (POD) in relation to pericarp browning of longan fruit. Fruit kept for 6 days in pure oxygen atmosphere at 28 C showed lower browning indices and higher ATP concentrations but lower AMP concentrations and higher respiratory rates, compared to those kept in air. While energy charge decreased during storage, the decrease was delayed markedly by exposure to pure oxygen. There was a lower energy charge in the browned fruit, which was associated with rapid increase in malondialdehyde concentration. Enhanced respiration of longan fruit exposed to pure oxygen can result in the production of ATP. However, fruit exposed to pure oxygen exhibited higher activities of PPO and POD, which was not associated with reduced skin browning inhibition. These results supported the hypothesis that skin browning of postharvest longan fruit may be a consequence of membrane injury caused by the lack of maintenance energy.

Inactivation of Possible Fungal Food Contaminants by Photosensitization

Abstract: Summary Photosensitization is based on the interaction of two nontoxic, nonmutagenic and noncarcinogenic agents – photosensitizer, accumulated in the microorganism, and visible light. This interaction in the presence of oxygen induces radical-based citotoxic events. The study has been carried out to define a new tool to improve microbial food safety by photosensitization for inactivation of several fungi, which are harmful for food industry and sometimes resistant to other treatments. The obtained data indicate that several microfungi such as Alternaria alternata, Fusarium avenaceum, Acremonium strictum and Rhizopus oryzae might be effectively inactivated by this new technology. Clear correlation was observed between the efficiency of inhibition of germination and the amount of photosensitizer, accumulated by the fungus.

An Alternative Approach to Non-Log-Linear Thermal Microbial Inactivation: Modelling the Number of Log Cycles Reduction with Respect to Temperature**

Abstract: Summary A mathematical approach incorporating the shoulder effect during the quantification of microbial heat inactivation is being developed based on »the number of log cycles of reduction« concept. Hereto, the heat resistance of Escherichia coli K12 in BHI broth has been quantitatively determined in a generic and accurate way by defining the time t for x log reductions in the microbial population, i.e. txD, as a function of the treatment temperature T. Survival data of the examined microorganism are collected in a range of temperatures between 52–60.6 °C. Shoulder length Sl and specific inactivation rate kmax are derived from a mathematical expression that describes a non-log-linear behaviour. The temperature dependencies of Sl and kmax are used for structuring the txD(T) function. Estimation of the txD(T) parameters through a global identification procedure permits reliable predictions of the time to achieve a pre-decided microbial reduction. One of the parameters of the txD(T) function is proposed as »the reference minimum temperature for inactivation«. For the case study considered, a value of 51.80 °C (with a standard error, SE, of 3.47) was identified. Finally, the time to achieve commercial sterilization and pasteurization for the product at hand, i.e. BHI broth, was found to be 11.70 s (SE=5.22), and 5.10 min (SE=1.22), respectively. Accounting for the uncertainty (based on the 90 % confidence intervals, CI) a fail-safe treatment of these two processes takes 20.36 s and 7.12 min, respectively.

The Prevalence of Multiple Antibiotic Resistance in Campylobacter spp. From Retail Poultry Meat

Abstract: Summary Macrolides and fluoroquinolones are regarded as drugs of choice for the treatment of human Campylobacter infections. The use of antimicrobials for this purpose as well as in food animal production has resulted in the resistance of Campylobacter spp. to selected antibiotics. Since poultry is one of the most important sources of human Campylobacter infections the use of antibiotics in animal production can shorten the effective therapeutic life of antibiotics for human use. During 2001–2003, over 220 strains of C. jejuni and C. coli were isolated from 60 poultry meat samples from the retail market in Slovenia and further characterized by phenotypic and molecular methods. In this study, 55 sample-representative strains were tested for susceptibility to eight different antibiotics (ampicillin, amoxycillin/clavulanic acid, ciprofloxacin, erythromycin, gentamicin, nalidixic acid, pefloxacin and tetracycline). Phenotypic procedures (disc diffusion test, E-test) as well as molecular detection of mutations (mismatch amplification mutation assay (MAMA) polymerase chain reaction (PCR)) in case of ciprofloxacin resistance were used. When assuming the results about antibiotic resistance, only 38.2 % of strains tested were susceptible to all antibiotics tested. Regarding ciprofloxacin, 58.2 % of tested strains were found to be resistant (minimal inhibitory concentration, MIC>4 mg/mL). The occurrence of resistance was much higher in C. coli (75.9 %) than in C. jejuni (38.5 %) isolates. The resistance rates to pefloxacin, nalidixic acid, erythromycin and tetracycline were 58.2, 49.1, 14.5 and 12.7 %, respectively. Eleven percent of strains were resistant to erythromycin and ciprofloxacin and 12.7 % of strains were resistant to tetracycline and quinolones. The results show the need for monitoring the prevalence and antibiotic resistance of zoonotic bacteria such as Campylobacter as well as the multiresistance phenomenon of Campylobacter isolates from food in our country.

Caprine αs1-Casein Polymorphism: Characterisation of A, B, E and F Variants by Means of Various Biochemical and Molecular Techniques

Abstract: Summary Considering a wide interest for the characterisation of caprine as1-casein variants and a large number of differently equipped laboratories, the objective of this study was to analyse and compare characteristics of caprine as1-casein variants by means of various biochemical and molecular techniques. The most frequent caprine as1-casein variants (A, B, E and F) were characterized by employing electrophoretic protein separation analyses (capillary zone electrophoresis, isoelectric focusing, and sodium dodecylsulfate polyacrylamide gel electrophoresis), chromatographic analysis (reversed phase-high performance liquid chromatography) as well as DNA analyses (ASA and real-time polymerase chain reaction approach). Further, we stressed weak and strong points for each method applied and provided information for the optimal and complementary use of those methods with respect to time, resolution and costs.

Hot Air Drying of Green Table Olives

Abstract: Summary The characteristics of hot air-drying of green table olives (Domat variety) by using a tray dryer were studied. Air temperature varied from 40 to 70 °C with an air velocity of 1 m/s. Drying rate curves were determined and quality of dried green olives was evaluated by instrumental analysis (bulk density, particle density, porosity, shrinkage, moisture content, water activity, colour value, protein content, oil content, peroxide value and acidity). Consumers’ acceptance test and microbiological analysis were also applied.

Monitoring of Genotoxicity in Drinking Water Using in vitro Comet Assay and Ames Test

Abstract: Summary A screening strategy for evaluation of genotoxic potential of drinking water has been proposed in the present work. Genotoxicity assays with tap water collected at three different sampling points in Ljubljana drinking water region are presented here. In vitro alkaline version of the comet assay was performed with human HepG2 and Caco2 cell lines and protozoa (Tetrahymena thermophila) cells. Parallel genotoxicity evaluation on the same samples was carried out by the Ames test (with/without exogenous metabolic activation) using Salmonella typhimurium TA97a, TA100 and TA1535 strains. Nonconcentrated and concentrated water samples were tested in both bioassays, and chemical analyses were performed to check the contents of pesticides and nitrates. There was no indication of genotoxic activity in any of the drinking water samples according to the Ames test. The results of the comet assays showed differences and possible genotoxic potential among the water samples tested on different cell types, which were, however, statistically not significant, except in two cases. Statistical analyses showed the comet assay was more sensitive than the Ames test for genotoxicity detection in drinking water samples.

Influence of tarhana herb (Echinophora sibthorpiana) on fermentation of tarhana, Turkish traditional fermented food

Abstract: Summary Tarhana herb (Echinophora sibthorpiana) (TH) is used as a spice in tarhana It has a pleasant flavour and stimulates some microorganisms In this study, the fermentation activity of tarhana was investigated by monitoring the lactic acid bacteria (LAB) and yeast populations when TH was used as additive It can be said that tarhana herb (Echinophora sibthorpiana) prevented the decrease in the counts of LAB and yeast below the initial number during tarhana fermentation

Influence of Saccharomyces cerevisiae Strains on General Composition and Sensorial Properties of White Wines Made from Vitis vinifera cv. Albariño

Abstract: Summary Yeast strains contribute to the oenological and sensorial characteristics of the wines they produce. The present study was performed to determine the influence of Saccharomyces cerevisiae strains on the composition and sensorial properties of Albarino wine. The must obtained from Albarino grapes was inoculated with 12 different yeast strains isolated from a single winery in Galicia, Spain. Chemical and sensorial analyses were performed on the final wines, which differed depending on the yeast strain used.

A Comparison of Methods Used to Define the Phenolic Content and Antioxidant Activity of Croatian Wines

Abstract: The concentrations of phenolic antioxidants and antioxidant activities were determined for three different vintages of red varietal Plavac mali wines (Grgich), white varietal Posip wines (Grgich) and white varietal Žlahtina wines (Grskovic). All three mentioned cultivars (Vitis vinifera L.) are well exploited in vineyards along the Croatian coast. Two different tests, the spectrophotometric Folin-Ciocalteau test and redox derivative potentiometric titration with electrogenerated chlorine, were used to quantify phenolic antioxidants and express them in gallic acid equivalents. The sequence of wines obtained by the two methods, ranked according to the increasing phenolic content, was comparable. Among all the tested wines, Plavac mali 2003 vintage showed the highest phenol content of  5 g/L. As expected, due to lack of anthocyanins and other pigments present in red wines, all six white wines showed approximately ten times smaller phenolic levels in comparison to the red wines, averaging between 190-380 mg/L. This study demonstrates the utilization of quick and reliable analytical techniques, spectrophotometry and derivative potentiometric titration, in quantification of wine phenolics. The change in free radical scavenging ability of the same set of wines was evaluated according to the Brand-Williams assay. The results showed, on the average, eight times greater free radical scavenging ability of red wines. Also, a slight decrease was observed in the free radical scavenging ability of the older vintage white wines, while the antioxidant activities of the older vintage red wines (Plavac mali) were slightly greater, due to formation of condensed tannins with time.

Scavenging Capacities of Some Wines and Wine Phenolic Extracts

Abstract: The aim of this study was to assess the ability of different wines – a sweet red, a dry red, a sweet white, and a dry white – to scavenge the stable 1,1’-diphenyl-2-picryl-hydrazyl radical (DPPH.) and to determine their phenolic composition. Both red wines contained, apart from anthocyanins, also higher concentration of total phenolics, tartaric esters, and flavonols than the two white wines. All wines exhibited scavenging activity analogous to their total phenolic content. However, their phenolics differed in antiradical potency, which was visible in their EC50 values. The dry red wine, Xinomavro, had a lower EC50 value, indicating the higher antiradical potency of its phenolics. The scavenging capacities of phenolic extracts from Xinomavro red wine on hydroxyl radicals, superoxide radicals, and singlet oxygen were also assessed. Wine total extract was fractionated by extraction, and each of the three fractions was then subfractionated by column chromatography into two subfractions. Wine total extract, and its fractions and subfractions exhibited scavenging capacity on hydroxyl radicals, superoxide radicals, and singlet oxygen, indicating the activity of many wine phenolics. The most active wine extracts towards hydroxyl radicals were characterized by the high peaks of flavanols, anthocyanins and flavonols in their HPLC-DAD chromatograms. The most active extract towards superoxide radicals was rich in flavanols and anthocyanins. The characteristic phenolics of the most active wine extracts towards singlet oxygen were flavanols, flavonols and phenolic acids. The ability of all red wine phenolic extracts to scavenge singlet oxygen, along with hydroxyl and superoxide radicals, emphasizes its health functionality.

Comparison of Selective Media for the Enumeration of Probiotic Enterococci from Animal Feed

Abstract: The project »Methods for the Official Control of Probiotics Used as Feed Additives« has been undertaken to develop and validate methods for the selective enumeration and strain identification of six probiotic microorganism genera (enterococci, lactobacilli, bifidobacteria, pediococci, bacilli and yeast). A diversity of media has been used for the detection, isolation and enumeration of enterococci. Aiming at the selective enumeration of enterococci (mainly Enterococcus faecium) present in probiotic animal feeds, either as a single component or in combination with other microorganisms, an extensive screening of published methods for culturing and enumerating enterococci was carried out. A collection of enterococcal strains used as probiotics in animal feeds and of isolates as well as reference strains from culture collections was established. Moreover, selected strains of lactobacilli, pediococci and streptococci were included for reference purposes. Based on a multitude of publications, twelve commercially available media were selected for testing and then compared with regard to their usefulness and selectivity. Bile esculin azide (BEA) agar showed good selectivity and pronounced growth of most enterococcal strains. Good reproducibility and electivity (esculin hydrolysis) as well as no influence of the feed matrix on the colony counts and a simple preparation procedure formed the basis for the proposed enumeration protocol. This work formed the basis for the enumeration protocol that was adapted to ISO format and validated in a collaborative study involving twenty laboratories from twelve European countries.

Comparison of Three RT-PCR Based Methods for Relative Quantification of mRNA

Abstract: Comparison of three RT-PCR based methods: semi-quantitative, competitive and real-time RT-PCR for relative quantification of mRNA is presented. Aminopeptidase N expressed on human promyeloid HL-60 cell line, at basal and activated state, served as a model for comparison. HL-60 cells were stimulated with IFN-gamma (6 ng/mL) for 72 h at 37 oC, total cellular RNA was isolated, reverse transcribed to cDNA and semi-quantitative, competitive and real-time RT-PCR were performed to obtain the relative levels of mRNA for aminopeptidase N. The data obtained showed that all three RT-PCR based methods give reliable and comparable results, i.e. approximately two-fold increase of aminopeptidase N mRNA on IFN-gamma stimulated HL-60 cells. Thus, in spite of rapid advances made in the area of real-time RT-PCR, end-point RT-PCR such as competitive and semi-quantitative RT-PCR, although laborious and time consuming, may still remain useful techniques for relative mRNA quantification when small number of samples are to be analyzed.

Differences in Bacterial Population in Rainbow Trout (Oncorhynchus mykiss Walbaum) Fry after Transfer from Incubator to Pools

Abstract: The microflora of rainbow trout (Oncorhynchus mykiss Walbaum) fry from a commercial freshwater hatchery, along with important water quality parameters such as temperature, dissolved oxygen and pH was analysed. Samples for bacteriological analysis were taken from gill, heart and kidney, from third to eigth week after hatching. Pure bacterial colonies were examined macroscopically, with Gram staining and biochemical tests. For final identification, the APILAB Plus programme (Bio Merieux, France) was used. The bacterial populations of rainbow trout fry changed depending on age. Most of the bacterial colonies were cultured from the gills (64.4 %), rather than the heart (21.8 %) and kidney (13.8 %). The bacterial community of fry gills from an incubator was composed mostly of Gram-positive bacteria such as Renibacterium salmoninarum, Lactobacillus spp., Staphylococcus spp. and Corynebacterium aquaticum. After the transfer of fry from incubator into the pools the Gram-negative bacteria increased in number and became the dominant microflora of rainbow trout fry and comprised more than 95 % of the bacterial flora of rainbow trout fry. Flavibacterium, Acinetobacter and Yersinia were the predominant Gram-negative genera in fry in the incubator, whereas Aeromonas and Pseudomonas were the main isolates from rainbow trout fry until the end of the experiment.

Study of Dynamics of Polyphenol Extraction During Traditional and Advanced Maceration Processes of the Babić Grape Variety

Abstract: Summary The influence of different maceration techniques on the dynamics of polyphenol extraction during the maceration of the autochthonous Croatian grape Babi} has been investigated. The process of wine production by maceration in traditional procedure and by maceration with advanced technique has been compared. During maceration, the dynamics of extraction of total anthocyanins, total phenols, low-molecular proanthocyanidins and high-molecular proanthocyanidins was determined. Mathematical models are proposed for each above mentioned and determined parameter. The models present the values under observation depending on treatment – traditional or modern. Time expressed in days is the input variable for both monitored models. Presented models indicate a significant positive correlation and strongly sustain the concept that the duration and procedure of maceration have considerable influence on the measured variables (R=0.83–0.98).