Biodiversity,dynamics and antimicrobial activity of lactic acid bacteria involved in the fermentation of maize flour for doklu production in Côte d'Ivoire

Doklu is a maize-based spontaneously fermented dough produced and consumed in parts of West Africa, particularly in Côte d'Ivoire. The characterization of the microbial ecosystem of doklu was carried out using a polyphasic approach. First, culture-dependent methods were used for bacterial enumeration and the phenotypic and molecular identification of 250 lactic acid bacteria (LAB) isolates. Then, culture-independent methods, including PCR-TTGE (V3 region of the 16S rRNA gene), provided a fingerprinting of bacterial DNA directly extracted from doklu. Bio preservative abilities were also tested and strains producing antimicrobial compounds were genotyped using PFGE. During maize dough fermentation, LAB became dominant and their load increased from 4.2 ± 0.2 log CFU/g to 9.0 ± 0.7 log CFU/g only after 48 h. Culture-dependent methods highlighted the presence of five LAB groups with the species Lactobacillus plantarum (28%), Lactobacillus fermentum (41.6%), Pediococcus acidilactici (6.8%), Pediococcus pentosaceus (18%) et Weissella cibaria (5.6%), succeeding during the fermentation. Lb. fermentum being practically the only species present at the end of fermentation, is with Lb. plantarum, the predominant species of fermenting dough. Culture-independent analysis underlined the undoubted role of Lb. fermentum, actively involved in the dough fermentation. These Lb. fermentum species, with a diversity of strains also showed important antimicrobial activity, due to production of bacteriocins. Being able to produce antimicrobial compounds, Lb. fermentum species may act as both bio protective culture as well as fermenting agent in cereal products and could be exploited to create functional starter cultures.     

Starter culture fermentation of Chinese sauerkraut: Growth,acidification and metabolic analyses

Chinese sauerkraut is a kind of traditional and typical fermented food. Four lactic acid bacteria (LAB) strains, Leuconostoc mesenteroides NCU1426, Lactococcus lactis NCU1315, Lactobacillus plantarum NCU1121 and Lactobacillus casei NCU1222 isolated from Chinese sauerkraut, were used in single starter cultures. Microbiological changes and pH values were monitored during fermentation. Metabolic substrates and products during the fermentation were examined using high performance liquid chromatography (HPLC) technology. Results have shown that Leu. mesenteroides and Lc. lactis grew faster, produced lactic acid earlier and were poorly acid-resistant, whereas Lb. plantarum and Lb. casei produced much more lactic acid throughout fermentation and showed better acid-tolerance. Two Lactococcus had outstanding performance in sucrose utilization while the other two Lactobacillus were likely to use glucose and fructose during fermentation. Unexpectedly, Leu. mesenteroides and Lc. lactis showed weak citric acid metabolism in fermentation. All the four LAB strains were able to utilize malic acid in early fermentation. In conclusion, these LAB strains have shown notable differences in growth and fermentative properties during starter culture fermentation of Chinese sauerkraut, probably resulting from LAB fermentative function and a mixture of complex substrates.     

Development of a multiplexed PCR assay combined with propidium monoazide treatment for rapid and accurate detection and identification of three viable Salmonella enterica serovars

Salmonella is the leading pathogenic bacteria in food and contaminated water. The aim of this study was to develop a rapid and reliable technique for simultaneous detection of the main three serotypes (Salmonella enterica serovars Typhimurium, Paratyphi B and Typhi) of Salmonella. Primers were designed to amplify the genes specific to each of these three serotypes for simultaneous detection using polymerase chain reaction (PCR). To ensure the detection of only viable cells, propidium monoazide (PMA) was applied to selectively suppress the DNA signal from dead cells. Results showed that the PMA-multiplexed PCR (PMA-mPCR) assay always gave negative results for heat-killed Salmonella at concentrations up to 1 × 10⁶ CFU/ml in pure culture or 1 × 10⁶ CFU/g in spiked food products (tomato, chicken, beef and ham). Results showed that the detection limits of the PMA-mPCR assay were approximately 10² CFU/ml (4.3 × 10² CFU/ml for S. Typhimurium, 3.7 × 10² CFU/ml for S. Paratyphi B, 7.2 × 10² CFU/ml for S. Typhi) in pure culture and 10³ CFU/g (4.3 × 10³ CFU/g for S. Typhimurium, 3.7 × 10³ CFU/g for S. Paratyphi B, 7.2 × 10³ CFU/g for S. Typhi) in food produce. These results demonstrated that the PMA-mPCR assay can simultaneously detect and identify viable S. Typhimurium, Paratyphi B and Typhi in a short period of time, even in food produce.     

Antimicrobial efficacy of a spice ferment in emulsion type sausages and restructured ham

The antimicrobial efficacy of a fermented spice preparation was assessed in emulsion type sausages and restructured hams and compared to that of two commercially-used antimicrobials; sodium lactate and lauric arginate. Restructured hams and emulsion type sausages were formulated with either sodium lactate (15 × 10³ μg/g), lauric arginate (N^α-lauroyl-l-arginine ethyl ester; LAE; 0.2 × 10³ μg/g) or a fermented spice preparation (20 × 10³ μg/g), and effect on microbial growth and sensory properties determined. The spice ferment retarded the growth of Listeria innocua on the surface of emulsion type sausages by about 16 days, while sodium lactate and lauric arginate retarded the growth for 6 and less than 1 days, respectively. On restructured hams, antimicrobial efficacy was lower with growth retardations being 10, 4 and 1 days for the spice ferment, sodium lactate and lauric arginate, respectively. Little activity of all three antimicrobials was found against contamination with Lactobacillus curvatus. No significant deviation in the sensory properties occurred upon addition of antimicrobials to either sausages or hams. Considering that growth of Listeria is one of the key problems in ready to eat meat products, the results are quite promising. Moreover, results suggest that consumers' demands for products without chemical additives may be addressed by exchanging lactate or acetate with fermented spices.     

Inhibition of Fusarium culmorum by carboxylic acids released from lactic acid bacteria in a barley malt substrate

The effect of carboxylic acids, composed by both organic and phenolic acids, released in a barley malt substrate fermented by lactic acid bacteria was tested against Fusarium culmorum macroconidia and compared under different fermentation conditions. Phenolic acids released by Lactobacillus plantarum FST1.7 and Lactobacillus brevis R2Δ were quantified using a QuEChERS method coupled with a HPLC-UV/PDA system. Their concentration improved with increasing extract content of the barley malt-based substrate and reached maximal concentrations after 48 h of fermentation performed at optimum growth temperature. Generally, phenolic acids were produced at levels far below their minimal inhibitory concentration (MIC), and limited synergistic effects were observed when mixed with organic acids. The fungal growth suppression by the wort fermented by Lb. brevis R2Δ (95 ± 9 h total inhibition) could be fully explained by the presence of antifungal carboxylic acids, whereas only partially accounted for Lb. plantarum FST1.7 (198 ± 19 h). Organic acids were mainly responsible for the ability of LAB fermented wort to cause fungal inhibition, whereas phenolic acids took only a secondary role at the low concentrations released. Longer fermentation times favoured primarily organic acid release, whereas fermentation of higher malt extract substrates encouraged both organic and phenolic acids production. The understanding on how synergy works between antifungal compounds could help to identify strategies to further increase their concentration in wort, with potential to replace synthetic broths and for direct application in food application.     

Safety of a street vended traditional maize beverage,ice-kenkey,in Ghana

Ice-kenkey is a chilled cereal beverage sold as street food in some open markets in Ghana. It is produced by mashing and sweetening kenkey, a stiff dumpling produced from fermented maize meal. The safety of street vended ice-kenkey was assessed by microbiological, elemental and myco-toxicological analysis of ice-kenkey and intermediary products obtained from 16 producers in four open markets in the Accra and Tema metropolis. A tenfold increase in counts of aerobic mesophiles, and yeast and moulds were recorded during the production of ice-kenkey. Coliform bacteria, E. coli and Staphylococcus aureus which were not detected in the starting materials were found partway through production or in the final product. The mean microbial counts in the packaged ice-kenkey were 10⁶–10⁷ CFU/g for aerobic mesophiles, 10⁴–10⁵ CFU/g for yeast and moulds, 10–1000 CFU/g for total coliforms and 10–100 CFU/g for S. aureus. E. coli counts of 10 CFU/g were recorded in samples from three out of the four markets. The microbial load could be eliminated by pasteurizing ice-kenkey at 80 °C for 15 min. The mean concentration in mg/kg of Fe was between 15.97 and 29.48, Cu, 0.57 to 1.41, Mn, 0 to 2.55, Pb 0 to 1.25 and Zn 0.47 to 6.17. Total aflatoxins content in samples ranged from 7.04 to 22.17 μg/kg and included a range of 7.01–20.54 for aflatoxin B₁, 0.51 to 1.63 for aflatoxin B₂ and 0–0.47 μg/kg for aflatoxin G_I. Aflatoxin G₂ was not detected in any of the samples. A simplified training module based GMP, GHP and a HACCP plan was developed and used to train ice-kenkey producers in Accra in collaboration with municipal authorities.     

Lactic acid bacteria bioprotection applied to the malting process. Part I: Strain characterization and identification of antifungal compounds

Lactic acid bacteria (LAB) are of interest to cereal and beverage industry due to their contribution to the microbial safety and quality of fermented food/beverages. The main objectives of this study were to optimize the production of an antifungal cell-free-supernatant (cfs), based on lactic acid bacteria, using a wort-base substrate; and the subsequent identification of its active acid-base antifungal compounds. Two antifungal strains (Lactobacillus amylovorus DSM19280 and Lactobacillus reuteri R29) and a negative control strain (L. amylovorus DSM20552) were used. Barley based malt extract (wort) was produced and used as a fermentation substrate. Worts fermented with LAB were characterized in detail (total cell counts, pH, and total titratable acids (TTA) over time (0–120 h). A microtiter plate and an overlay agar based assay were used to evaluate the antifungal activity of the LAB cfs. Sugars, organic acids of the fermented and non-fermented wort (control) were analysed by HPLC. LAB antifungal metabolites were quantified using a QuEChERS method and an HPLC-UV/PDA system. Results show that wort produced from barley malt is a suitable substrate for LAB and dependent on the species and the fermentation time. The type of antifungal compounds can vary significantly. L. amylovorus DSM19280 cfs inhibited Fusarium culmorum spores at levels of 10⁴ spores.mL⁻¹, for 7 days, whereas L. reuteri R29 cfs inhibited up to 10⁵ spores.mL⁻¹ for the same time. Thirteen acid-base antifungal compounds were identified in L. reuteri R29 cfs and twelve in L. amylovorus DSM19280. Among them, phenyllactic, OH-phenylactic and benzoic acids were present at a significant concentration. This study demonstrates that the LAB wort-base cfs exhibits potent antifungal activity and is the ideal substrate for applications in a wide range of cereal products.     

Effect of autochthonous starter cultures on microbiological and physico-chemical characteristics of Suan yu,a traditional Chinese low salt fermented fish

In this study, three groups of mixed starter cultures (S1: Lactobacillus plantarum 120, Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31; S2: L. plantarum 145, S. xylosus 135 and S. cerevisiae 22; S3: Pediococcus pentosaceus 220; S. xylosus 135 and S. cerevisiae 22), isolated from Suan yu, were inoculated to produce the traditional fermented fish. After 42 days fermentation at 24 °C, Suan yu inoculated with different mixed starter cultures underwent rapid growth of lactic acid bacteria (LAB), declined pH, suppressed increase of thiobarbituric acid (TBARS) and total volatile base nitrogen (TVB-N) as well as growth of spoilage bacteria and pathogens. Besides, Suan yu had higher contents of non-protein nitrogen (NPN) and total free amino acids (FAA) compared to the control (P < 0.05). The muscle proteins were severely hydrolyzed during fermentation (SDS-PAGE). Moreover, the sensory evaluation indicates the fermented fish was more widely accepted than the control. The results suggest that the inoculation with S1, S2 and S3 reduced the lag time that fermentation began and improved the quality of Suan yu.     

Comparative studies on antibiotic resistance in Lactobacillus casei and Lactobacillus plantarum

The levels of resistance in 17 Lactobacillus casei isolates and 15 Lactobacillus plantarum isolates to 10 antibiotics were determined using a standardized macrodilution method and the presence/absence of 20 genes implicated in antibiotic resistance in these isolates was determined by polymerase chain reaction (PCR) using gene-specific primers; 11 isolates possessed one or more of these genes but they were not always associated with phenotypic resistance. L. plantarum isolates had the widest spectrum of MIC values for streptomycin ranging from 16 to 512 μg/mL. In particular, two isolates of L. plantarum IMAU60045 and IMAU80091 both possessed aadA and ant(6) genes implicated in resistance to streptomycin but varied in their tolerance to streptomycin as evidenced by their minimum inhibitory concentration (MIC) of 16 and 256 μg/mL, respectively. Selection of high streptomycin resistance of L. plantarum IMAU60045 was performed over a 30 day period using serial passage with regular increases in streptomycin concentration to reflect the changes in resistance levels. Final MIC value of 16,384 μg/mL was recorded which was 1024-fold higher than the original parental isolate. Furthermore, associated variable degrees of increase in the MIC value for gentamicin, kanamycin and neomycin illustrated that, under the challenge of streptomycin, cross-resistance to other structurally related antibiotics of the same class developed. The relative quantity of gene expression (RQ) for the streptomycin resistance gene aadA was 3.35 times greater after passage in increasing concentrations of streptomycin than the original parental isolate. This was greater than the increase in the RQ value for the streptomycin resistance gene ant(6) after passage.     

Evaluation of functional properties of lactobacilli isolated from Korean white kimchi

Kimchi, probably Korea's most famous traditional fermented food, is well known for its beneficial properties. Among several hundred different types of kimchi in Korea, white (baek) kimchi is prepared without chilli and is widely appreciated also by non-Koreans because of its unique mild flavour. In an approach to identify the bacteriological basis for proposed health benefits, we isolated 11 Lactobacillus strains from six samples of white kimchi, and investigated their safety and functional features. These strains represented the species Lactobacillus brevis, Lactobacillus plantarum and Lactobacillus sakei that dominated the populations within a range of 3 × 10⁶ to 4 × 10⁸ CFU/mL. Following safety assessment based on antibiotic resistance and biogenic amine production, 7 different strains were selected for further studies including evaluation of their adaptation to cabbage juice and resistance to phenol. Growth in and adaptation to the cabbage juice was favourably influenced by addition of 2% salt. Final selection was based on in vitro passage of simulated stomach duodenum conditions (SSDP model). The strains L. plantarum HAC01 and L. sakei HAC10 were administered to a diet-induced obese (DIO) mouse model receiving a high-fat (HF) diet to assess their functionality in-vivo. Animal groups receiving the viable strains showed significantly lower body weight and total weight gain during 8 weeks compared to the high-fat control group. This study provides preliminary information on the use of in-vitro and in-vivo features for safety and functionality evaluation of Lactobacillus strains from white kimchi. These “first-level” criteria for strain selection may serve as model, thereby facilitating potentially new probiotic developments.     

Development of a rapid and sensitive quantum dot-based immunochromatographic strip by double labeling PCR products for detection of Staphylococcus aureus in food

Staphylococcus aureus was listed as the 2nd common food-borne pathogens, resulting in diseases such as pneumonia, pseudomembranous colitis, pericarditis and even sepsis. A rapid, simple and sensitive detection method is required to monitor food in cases of contamination by S. aureus. Hence, a novel immunochromatographic test strip (ICTS), based on the two-component reaction (i.e. digoxigenin and anti-digoxigenin, quantum dots-conjugated streptavidin and biotin) in test line with QDs as indicator, was developed for the rapid and sensitive detection of S. aureus. Genomic DNA from bacteria lysis by boiling was extracted easily and rapidly with silica-coated magnetic nanoparticles, and a species-specific gene was amplified by PCR using digoxigenin/biotin-labeled primers. The fluorescence of captured QD labels on the test line and control line served as signals was observed by UV light. The sensitivity and specificity of the ICTS were estimated using bacteria spiked food samples (artificially mixed with cell counts (10⁸ CFU/mL for each bacterium) of Escherichia coli, Listeria monocytogenes and Lactobacillus plantarum). The limit of detection for S. aureus was 3 × 10⁰ CFU/mL and 3 × 10¹ CFU/g in spiked milk powder and meat samples, respectively, which was not affected by those non-S. aureus strains. Our results showed that QDs-based ICTS was promising for rapid and sensitive detection of S. aureus within 2 h. Hence, this protocol might be useful for screening and monitoring the contamination of S. aureus in food products, and helpful for promoting the prevention and control of communicable disease caused by food-borne pathogen.     

Preservation of viability and anti-Listeria activity of lactic acid bacteria,Lactococcus lactis and Lactobacillus paracasei,entrapped in gelling matrices of alginate or alginate/caseinate

In order to control undesirable microorganisms growth in foods, the performance of alginate and alginate–caseinate (an aqueous two-phase system) matrices entrapping lactic acid bacteria (LAB) (Lactobacillus paracasei LAB1 and Lactococcus lactis LAB3) was investigated. Polymeric matrices were initially loaded with LAB cells at ∼10⁸⁻¹⁰ or ∼10⁴⁻⁶ CFU mL⁻¹, and were monitored, in liquid and gelled form (beads), for 12 days at 30 °C. In the liquid form, maximum cell density (∼10⁹ CFU mL⁻¹) was reached after 24 h whatever the matrix. Then, the LAB population decreased but remained higher in alginate–caseinate matrices: 10⁷ and 10⁶ CFU mL⁻¹ of LAB3 cells were enumerated after 12 days in alginate–caseinate and in alginate matrices, respectively. Anti-Listeria activity (assayed by agar well diffusion method) did not vary much over 12 days and was also higher for cells entrapped in alginate–caseinate matrices. When matrices were gelled, similar trends were observed: at “Day 12”, LAB3 population was 10⁴⁻⁵ and 10²⁻³ CFU/bead, and, LAB1 population was 10⁵⁻⁶ and 10³⁻⁴ CFU/bead, in alginate–caseinate and alginate beads, respectively. Antimicrobial activity of alginate–caseinate beads containing LAB1 cells was quite constant over 12 days. The anti-Listeria activity of LAB cell-free supernatants incorporated in matrices with caseinate was also higher. In fact, the presence of caseinate was shown to promote both the survival of LAB cells and the release of their antimicrobial metabolites. Observation of liquid and gelled matrices by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) revealed a preferential localization of LAB cells in casein-rich microdomains which could affect favorably the efficiency of bipolymeric matrices.     

Bacteriocin-producing Lactobacillus sakei C2 as starter culture in fermented sausages

Lactobacillus sakei C2, which could produce a bacteriocin with a broad inhibitory spectrum, have been proven to have certain probiotic potential. The practical application of L. sakei C2 as starter culture in the production of fermented sausage was investigated. During the sausage fermentation, L. sakei C2 established its prominent position in the microbial ecosystem, and, over 62.5% and 87.5% isolates were detected at each sampling point, when respectively inoculated with 5 and 7 log CFU/g. Moreover, L. sakei C2 as starter culture played an important role in the control of harmful microorganisms presented in the fermentation. Malondialdehyde (MDA) content and nitrite content in the samples of fermented sausages decreased with the increase of the inoculation concentration of L. sakei C2. Inoculation with L. sakei C2 significantly increased the color values of L* (lightness), and a* (redness), and magnitude of absorbance, which indicated that L. sakei C2 might increase the amount of nitrosylmyoglobin (NO-Mb) in the fermented sausages. By the evaluation of the panel, flavor and overall acceptability of the fermented sausage processed with 7 log CFU/g of L. sakei C2 was significantly superior to those processed with lower inocula (5 log CFU/g) and the control. All these results indicted that L. sakei C2 had good potential to be used as starter culture in the production of fermented sausages.     

Reduction in vitro of the minor Fusarium mycotoxin beauvericin employing different strains of probiotic bacteria

The interaction between the minor Fusarium mycotoxins BEA and 13 bacterial strains characteristic of the gastrointestinal tract as Bifidobacterium longum, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium adolescentes, Lactobacillus rhamnosus, Lactobacillus casei-casei, Lactobacillus plantarum, Eubacterium crispatus, Salmonella fecalis, Salmonella termofilus, Lactobacillus ruminis, Lactobacillus casei and Lactobacillus animalis was studied.The fermentations were carried out in the liquid medium of MRS during 4, 12, 16, 24 and 48 h at 37 °C, under anaerobic conditions.Levels of BEA in the fermentation liquid, on the cell walls and on the internal part of the cells were determined using liquid chromatography coupled to the mass spectrometry detector (LC-MS/MS). Results showed that the bacteria reduced the concentration of the BEA present in the medium, part of the mycotoxin was adsorbed by cell wall and part internalized by the bacteria. All the bacteria analyzed in this study showed a significant BEA reduction during the fermentation process, in particular the mean diminution resulted variable from 66 to the 83%.     

Screening of lactobacilli with antagonistic activity against enteroinvasive Escherichia coli

In the present study, 339 lactic acid bacteria (LAB) strains, isolated from fermented dough, pickles, salted meat, baby feces and fermented dairy products, were screened for the antagonistic activity against enteroinvasive Escherichia coli (EIEC). Through the analysis of the inhibition zone of the lactobacilli spent culture supernatant on the growth of EIEC, 22 LAB strains were selected for further analysis. Using the in vitro assays of adhesion to HT-29 cell lines and tolerance to gastrointestinal conditions (acid and bile), two isolates, Lactobacillus plantarum CCFM 233 and L. plantarum CCFM 231 were shown not only to inhibit the growth of EIEC significantly, but also to have high adhesion to HT-29 cell lines and good tolerance to low acid and high bile. Furthermore, the two strains could strongly antagonize the adhesion and invasion of EIEC to the HT-29 cell lines. This study suggests that L. plantarum CCFM 233 and L. plantarum CCFM 231 could be used as potential probiotics in food applications against EIEC.     

Mycological quality and mycotoxin contamination of Sri Lankan peppers (Piper nigrum L.) and subsequent exposure assessment

The aim of the study was to characterize the toxigenic moulds and to screen different mycotoxins in peppers (Piper nigrum L.) of Sri Lankan origin. Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger and Penicillium spp. were found to be the most dominant fungi. Characterization of the moulds was carried out in A. flavus and parasiticus agar (AFPA) and malt extract agar (MEA) in 77 black pepper (BP) and 11 white pepper (WP) samples. In total, 73% of the BP and 64% of the WP samples were contaminated with A. flavus and/or A. parasiticus (AfAp). A BP sample with water activity (a_w) 0.70 recorded the highest count of AfAp (4.3*10⁴ CFU/g). Moreover, 75% of the BP samples exceeded the safe a_w limit (0.65) set by the European Spice Association (ESA). The frequency of occurrence of A. niger in BP was 62% with counts up to 1.3*10³ CFU/g. Penicillium spp. were found in 61% and 55% of the BP and WP samples, respectively. In BP 94% of the samples had a Penicillium contamination below 10³ CFU/g. Other Aspergillus spp, found in peppers included, Aspergillus terrus, Aspergillus tamarii, Aspergillus candidus, Aspergillus penicilloides, Aspergillus sydowii and Aspergillus fumigatus. Mould counts in BP (10²–10⁴ CFU/g) were significantly higher than that of WP (<10² CFU/g). Apart from the occurrence of “classical mycotoxins” of spices, aflatoxins (<LOQ-18 μg/kg) and ochratoxin A (<LOQ-79 μg/kg), other toxins including fumonisin B1 (<LOQ-135 μg/kg), sterigmatocystin (<LOQ-49 μg/kg) and citrinin (<LOQ-112 μg/kg) were detected in peppers. In total, 63% of the BP samples were contaminated with at least one mycotoxin. Mycotoxin contamination in WP was significantly less compared to BP. The exposure to aflatoxins and ochratoxin A by consuming pepper remains harmless considering the existing pepper dietary intake data of the Sri Lankan population.     

Control of Fusarium moulds and fumonisin B1 in seeds by gamma-irradiation

The distribution of naturally occurring Fusarium moulds producing fumonisin B₁ in seeds was determined. Fusarium infection of seed samples ranged from 10% to 60%, Fusarium moniliforme was the predominant species. Fusarium counts in wheat seeds were 8.1 × 10⁴ CFU/g, 6.3 × 10⁶ CFU/g in maize and 4.8 × 10³ CFU/g in barley. Wheat, maize and barley seeds naturally contaminated with varying levels of fumonisin B₁ 1.4–5.8, 8.0–13.8 and 0.1–0.5 μg/g, respectively. F. moniliforme and Fusarium proliferatum were major Fusarium contaminants producing fumonisin B₁. The effect of gamma irradiation on Fusarium moulds and levels of fumonisin B₁ was also determined. The viable counts of Fusarium in seeds decreased by increasing the radiation dose levels and the growth of Fusarium spp. was inhibited at 4.0 kGy for barley and 6.0 kGy for wheat and maize. Application of radiation dose at 5 kGy inactivated fumonisin B₁ by 96.6%, 87.1% and 100% for wheat, maize and barley, respectively, and a dose of 7 kGy was sufficient for complete destruction of fumonisin B₁ in wheat and maize.     

General patterns of background microbiota and selected bacterial pathogens during production of fermented sausages in Serbia

The presence of Salmonella spp. or Escherichia coli O157 and background microbiota, pH and a_w were determined in raw fermented sausages produced from pork or beef and without lactic acid bacteria starters. The investigation was conducted at five meat processing plants, and the sampling was done at five steps of the production process at each plant. In meat trimmings, total viable count (TVC) ranged around 6 log CFU/g and around 5–6 log CFU/g in the pork and the beef sausages, respectively. Enterobacteriaceae count (EBC) ranged in the vicinity of 3–4 log CFU/g, whilst E. coli count (ECC) ranges were comparably lower (by 1–2 logs). During chopping of both the pork and the beef trimmings, the levels of TVC, EBC and ECC increased by 1–1.5 logs. After the additives and the spices were added, background microbiota tended to slightly decrease, generally more noticeably in pork sausages and with ECC. During the fermentation-drying stage, in both pork and beef sausages, initial TVC levels (6–7 log CFU/g) increased by the mid-process (by approximately 1.5–2 logs) and remained at those levels in finished products. During the same period, lactic acid bacteria (LAB) increased from initial levels of 5.5–6 log CFU/g to around 7–8 log CFU/g in pork and around 8–9 log CFU/g in beef sausages, and became the predominant microbial group. Salmonella spp. was found in the first three stages of the production process (trimmings, trimmings chopping, mixing with additives/spices), in two of three meat processing plants, but not at later stages of the production process. E. coli O157 was found only in one sample of chopped trimmings in one meat processing plant. The background microbiota patterns and levels were, generally, similar to those commonly reported for raw fermented sausages in other published studies. The initial presence of foodborne pathogens in raw fermented sausage production may be considered as a potential meat safety risk, because in the case of high initial pathogen counts, their total elimination cannot be assumed.     

Microflora of traditional starter made from cassava for “attiéké” production in Dabou (Côte d’Ivoire)

Attiéké is a food made from cassava in Côte d’Ivoire by fermentation. The process uses a traditional starter. Studies on 81 starter samples from 3 villages showed that the dominant microflora consists of lactic acid bacteria (5.7 × 10⁷ cfu/g), yeasts (5.5 × 10⁷ cfu/g), Bacillus (3.8 × 10⁷ cfu/g), Enterococcus (3.0 × 10⁶ cfu/g), total coliforms (3.0 × 10⁶ cfu/g), thermotolerant coliforms (8.0 × 10³ cfu/g) and mould (2.0 × 10⁶ cfu/g). Lactic acid bacteria, Bacillus spp, yeasts, faecal Enterococci and moulds are organisms which could play a role in the cassava fermentation. Coliforms may indicate contamination from the environment during production.     

Lactic acid bacteria in cooked hams – Sources of contamination and chances of survival in the product

The aim of this study is microbiological analysis of individual technological operations during the industrial production of cooked hams, focusing on lactic acid bacteria (LAB). Samples were during the course of the entire cooked ham production cycle in May–June (Experiment I) and November–December (Experiment II). A total of 215 samples were taken and subsequently tested. The difference in the occurrence of LAB in meat before thermal processing resulted from the initial level of contamination of the raw material. A reduction to the number of LAB from 4.0 to 5.0 log CFU/g of meat to a value of practically zero occurred during the thermal processing. The LAB population increased during storage of the finished products. A level of 7.0 log CFU/g was reached in slices of ham in the modified atmosphere after three (Experiment I) or two (Experiment II) weeks of storage, respectively. LAB of the genera Leuconostoc (Leuc. carnosum, Leuc. mesenteroides and Leuc. gelidum) occurred most frequently in samples of cooked ham after thermal processing. These species were also isolated from the production environment. Lactobacillus sakei, Lbc. curvatus and Weissella viridescens were other species of LAB that were isolated from samples after thermal processing.