Microbiological profile of helva sold at retail markets in Izmir city and the survival of Staphylococcus aureus in this product

The objective of this research was to determine the microbiological profile of tahin helva, a low moisture confectionery. A total of 63 tahin helva samples were collected from the retail markets in Izmir, Turkey. These samples were examined by standard procedures for aerobic plate count (APC) and counts of moulds and yeasts, Enterobacteriaceae, Staphylococcus aureus and Salmonella spp. APC of samples ranged from <10 to 1.6 × 10⁵ cfu/g. The counts for moulds, yeasts and Enterobacteriaceae ranged from <10 to 1.8 × 10³, <10 to 7 × 10², <10 to 8.5 × 10² cfu/g, respectively. None of the samples contained S. aureus or Salmonella. The potential for survival of S. aureus in the product stored at refrigeration (4 °C) and room (20 °C) temperatures was evaluated by artificial contamination. S. aureus cells were still recovered after 9 months of storage at both temperatures. The results of this investigation indicate that S. aureus contamination of tahin helva, (a_w of 0.172) may constitute a potential public health hazard, depending on the extent of contamination and mishandled exercise at the sale area and the kitchen.     

Microbiological safety and quality of commercial sufu – a Chinese fermented soybean food

In this study, the microbiological safety and quality of commercial sufu were investigated. Twenty-three samples of three different types of sufu were obtained, mainly in China and some in The Netherlands. Chemical parameters analysed included moisture, pH, free amino N, NaCl, ethanol, sucrose, glucose, and fructose. Concentrations of NaCl, ethanol, glucose and fructose varied from 6.2%, 0.5%, 0% and 0% to 14.8%, 6.3%, 6.2% and 4.8%, respectively. Microbiological analyses were done for total count of mesophilic aerobic bacteria (TMAB), bacterial endospores, total count of halotolerant bacteria at 10% (THB10) and at 17.5% NaCl (THB17.5), lactic acid bacteria (LAB), fungi, Enterobacteriaceae, and the following pathogens: Bacillus cereus, Clostridium perfringens, Staphylococcus aureus and Listeria monocytogenes. High levels (>10⁵ CFU/g) of TMAB and bacterial endospores were found in most samples, and 85% of TMAB was identified as Gram-positive. Considerable levels (10⁵ and 10⁷ CFU/g) of LAB were detected in two samples of white sufu, and isolates of LAB were identified as most probably Lb. casei. One-third of the samples contained less then 10³ CFU/g B. cereus, but three samples had over 10⁵ CFU/g indicating potential hazard to consumers. All samples had less than 10³ CFU/g C. perfringens, except sample R11 (10⁵ CFU/g). S. aureus could not be detected in any of the samples tested since the competitive microflora (usually bacilli) disturbed typical features on the selective medium used; however S. aureus enterotoxin A was detected in some of the white and grey sufu samples. Fungi, Enterobacteriaceae, and L. monocytogenes were not detected in any of the samples. Based on these results, a microbiological guideline for safe commercial sufu is proposed.     

An evaluation of the effect of storage and processing temperatures on the microbiological status of sous vide extended shelf-life products

The microbiological and organoleptic quality of selected sous vide products was monitored over a storage period of up to five weeks at 3°C and 8°C, respectively. Sous vide products stored at the recommended temperature of 3°C showed negligible microbial growth and were found to be organoleptically acceptable throughout the storage period. Total plate counts at the end of the fourth week of storage were in the range <10–7×10³ CFU/g for all 19 products under study. Listeria monocytogenes, Salmonella, Clostridium perfringens, Bacillus cereus and Enterobacteriaceae were not detected in any of the processed samples. At 8°C, under temperature abuse conditions, while some products had acceptable microbial levels of 10²–10⁴ CFU/g after three weeks, others such as chicken chasseur had counts above 10⁶ CFU/g by the second week of storage. Lactic acid bacteria and Pseudomonas species were dominant in the microbial flora of spoilt samples and B. cereus (>3×10⁴ CFU/g) was isolated from spoilt chicken chasseur samples in the fourth week of storage at 8°C. Critical factors affecting sous vide product safety are discussed.     

Microbiological quality of fruit juices sold in Tripoli–Libya

Fruit juices are becoming an important part of the modern diet in many communities. Data regarding the microbiological quality of foods, particularly fruit juices, sold in Libya and the neighboring North African countries are few if not lacking. Using standard microbiological procedures, 146 fruit juice samples sold in Tripoli were examined. Total bacterial counts (TBC) of samples examined ranged between <1 and 3 × 10⁵ CFU/ml (mean = 5 × 10⁴). Almond juice showed the highest TBC ranging between 1.8 × 10³ and 3 × 10⁵ (mean = 1.7 × 10⁵). Staphylococcus aureus was detected in 8 (5.5%) samples, Streptococcus spp. in 4 (2.7%), coliforms in 33 (22.6%), Escherichia coli (none were of serogroup O157) in 3 (2.1%), Klebsiella pneumonia in 17 (11.6%), Aeromonas spp. in 3 (2.1%), Pseudomonas aeruginosa in 6 (4.1%), Candida albicans in 18 (12.3%), Candida spp. in 109 (74.7%) and other yeasts in 85 (58.2%). Many of these organisms can cause disease in humans, which indicates that a large number of juices tested did not fulfill the Libyan guidelines for the microbiological quality of juices. Application of the HACCP system should be introduced into the food industry sector to improve the quality of fruit juices and other foods manufactured in Libya.     

Microbiological quality assessment of garri with reference to thermonuclease activity

The microbiological quality of garri obtained from open markets and traditional processing industry in Benin City with reference to staphylococcal contamination was investigated. Enumeration of the total heterotrophic bacteria, total fungal propagules and Staphylococcus aureus in food samples was carried out using appropriate media. The staphylococcal thermonuclease activity determination was used as an indicator of previous (substantial) growth of S. aureus and possible presence of staphylococcal enterotoxins. The total heterotrophic bacterial count of the open markets’ samples was 7.75±2.87×10³ cfu/g with corresponding staphylococcal count of 1.65±0.82×10³ and fungal propagule count of 2.50±1.14×10² cfu/g. Samples obtained immediately after processing from the traditional garri industry revealed total heterotrophic bacterial count of 5.00×10¹ cfu/g; staphylococcal count of 5.00×10⁰ cfu/g and no fungal count. The zone diameter of thermonuclease activity was 8.13±0.52 mm for open markets’ samples while traditional processing industry samples have 7.83±0.54 mm. From the study, it was found that there was contamination and growth of S. aureus and possibly the presence of staphylococcal enterotoxin in the product. The public health significance of the microorganisms with the production of thermonuclease and enterotoxins by S. aureus are discussed.     

Microbiological safety of kinema, a fermented soya bean food

Kinema is a fermented soya bean food of Nepal and the hilly regions of North-eastern States of India. Generally, the fermentation is dominated by Bacillus spp. that often cause alkalinity and desirable stickiness in the product. The present study was undertaken in a limited number of commercial (market) kinema samples to test for the presence of foodborne pathogens and their properties. Bacillus cereus was present in numbers exceeding 10⁴ cfu/g product in five of the tested 15 market samples. Enterobacteriaceae and coliform bacteria exceeded 10⁵ cfu/g in 10 of the 15 samples. Escherichia coli exceeding 10⁵ cfu/g was found in two samples. Staphylococcus aureus was not detected in any of the tested samples. Of 31 isolated typical and atypical strains of B. cereus, 18 representative strains were tested qualitatively for the ability to produce diarrhoeal type enterotoxin (BCET) using an Oxoid BCET-RPLA test kit. Overall, BCET was formed by 12 strains in BHIG (brain heart infusion broth +1% glucose), by seven strains on sterilized cooked rice, and by five strains on sterilized cooked soya beans. Semi-quantitative tests on BCET revealed that levels exceeding 256 ng/g soya beans, produced by single pure culture inoculation with the isolated B. cereus strains, were reduced to ≤ 8 ng/g by frying kinema in oil, a common procedure when making kinema curry. It was also shown in a mixed pure culture experiment that a kinema strain B. Subtilis DK-W1, is able to suppress growth and BCET formation by a selected toxin producing strain (BC7-5) of B. cereus. It is concluded that the traditional way of making kinema and its culinary use in curries is safe. However, for novel applications of kinema, safety precautions are advisable.     

Antibacterial activities of the surface microflora of Kefalograviera cheese

The microflora developed on the surface of Kefalograviera, a hard cheese, during ripening in the warm room was studied. The microbial total counts and yeasts decreased (P < 0.05) and the same was observed with the pH on ripening for 15 days. Bacilli dominated at day 4 while at 15 days Micrococcaceae and enterococci occurred frequently. A great number (38 out of 56) of the isolates exhibited narrow spectrum of antibacterial activities against Gram-positive indicator strains, while ten of the Bacillus isolates (Bacillus pumilus) inhibited the growth of Listeria monocytogenes. The extracellular antilisterial substances were sensitive to proteinase K and heat labile (at 100 °C).     

Application of electrolyzed oxidizing water on the reduction of bacterial contamination for seafood

For reducing bacterial contamination, electrolyzed oxidizing water (EO water) has been used to reduce microbial population on seafood and platform of fish retailer. The specimens of tilapia were inoculated with Escherichia coli and Vibrio parahaemolyticus, and then soaked into EO water for up to 10 min. EO water achieved additional 0.7 log CFU/cm² reduction than tap water on E. coli after 1 min treatment and additional treatment time did not achieved additional reduction. EO water treatment also reduced V. parahaemolyticus, by 1.5 log CFU/cm² after 5 min treatment and achieved 2.6 log CFU/cm² reduction after 10 min. The pathogenic bacteria were not detected in EO water after soaking treatment. In addition, EO water could effectively disinfect the platform of fish retailer in traditional markets and fish markets.     

Occurrence of pathogenic bacteria in raw milk, cultured pasteurised milk and naturally soured milk produced at small-scale dairies in Zimbabwe

The presence of selected pathogenic bacteria in raw milk (RM), cultured pasteurised milk (CPM), and naturally soured raw milk (NSRM) sold at three small-scale dairies in Zimbabwe was determined. Mean levels of Escherichia coli in RM, CPM and NSRM were 4.5, 7.1 and 7.8 log₁₀ CFU ml⁻¹, respectively. Enterotoxigenic E. coli (ETEC), producing heat-stable enterotoxin (ST1) was found in 16 of the samples. Presumptive Staphylococcus aureus was identified in 7 of 12 RM, 15 of 27 CPM and 20 of 21 NSRM samples at mean levels of 5.2, 7.3 and 7.8 log₁₀ CFU ml⁻¹, respectively. Klebsiella pneumonia spp., Enterobacter cloacae, Proteus mirabilis, Hafnia alvei, Citrobacter spp., Serratia marcescens and Aeromonas hydrophilia were found in 27 samples. The high number of S. aureus, E. coli, identification of ETEC-ST1 and the other pathogenic microorganisms found in pasteurised and unpasteurised milk products represent a health hazard to the consumers and emphasises the need for improved hygiene practice at all levels in the dairy.     

Microbial and quality evaluation of green peppers stored in biodegradable film packaging

The effects of polylactic acid (PLA) based biodegradable film packaging on the microbial and physicochemical quality of green peppers (Capsicum annuum L.) were compared to the effects of low-density polyethylene (LDPE) film packaging, and perforated LDPE film packaging. Each package containing green peppers was heat-sealed and stored for 7 days at 10 °C. The microbial levels (aerobic bacteria, coliform bacteria, and yeast and moulds) and physicochemical properties such as colour, weight loss, hardness, ascorbic acid concentration, O₂ and CO₂ concentrations, were monitored during storage. Results indicated that the physicochemical properties of colour, hardness, ascorbic acid concentration, and microbial levels (total aerobic bacteria, and moulds and yeasts) did not show remarkable changes during storage period. The microbial levels in coliform bacteria were increased by less than 1 log CFU/g (0.2 log CFU/g) in the biodegradable film packaging, 2.3 log CFU/g in LDPE film package, and less than 1 log CFU/g (0.9 log CFU/g) in the perforated LDPE film package, after 7 days storage period. The results suggest that the biodegradable film with higher water vapor permeability can be used to maintain the quality and sanitary conditions (protection from microbial and insect contamination) of freshly harvested green peppers in modified atmosphere packaging.     

Inhibition of food poisoning and pathogenic bacteria by Lactobacillus plantarum strain 2.9 isolated from ben saalga, both in a culture medium and in food

The bacteriocinogenic strain Lactobacillus plantarum 2.9 isolated from the traditional pearl millet-based African fermented food ben saalga was tested for inhibition of food poisoning and pathogenic bacteria in MRS broth and in a malted millet flour slurry. In MRS broth, strain 2.9 completely eliminated Bacillus cereus, Escherichia coli O157:H7 and Salmonella enterica cells within 48 h incubation at 22–30 °C. A much lower inhibition was observed at 15 °C. The inhibitory effect of strain 2.9 on the above-mentioned target bacteria was corroborated in the malted millet flour slurry, reducing viable cell counts below detection levels after 8 h storage for B. cereus or after 24 h for S. enterica and 48 h for E. coli. An Enterobacter aerogenes strain was only moderately inhibited in the slurry. Results from the present study suggest that strain 2.9 could be used as starter culture to improve the microbiological safety of fermented ben saalga.     

Survival and growth of Listeria monocytogenes on sausage formulated with inoculated and stored rework product

To assess the effect of including contaminated rework on survival and growth of Listeria monocytogenes, two sausage formulations (one American, Bologna sausage; and one Bulgarian, Stranja sausage) were inoculated with the pathogen and stored for 4 days at 10 °C plus 15 h at 30 °C. After storage, both rework types were included (at 20% and 40%) in corresponding fresh sausage emulsions and heated to 68, 70 and 71.7 °C; fresh Bologna and Stranja emulsions served as controls and were inoculated with 24 h broth cultures of the same 10-strain mixture of L. monocytogenes and thermally treated to the same temperatures. The results showed that heating to 68 and 70 °C inactivated 3–4 log CFU/g of the initial concentration of L. monocytogenes cells (>7 log CFU/g), while heat treatment to 71.7 °C in the center of experimental samples reduced counts by 6 log CFU/g. Survival of L. monocytogenes in samples heated to 68 and 70 °C was higher in controls. Control samples of Stranja emulsion heated to 71.7 °C allowed higher growth (P < 0.05) during storage (5 days at 10 °C) as compared to other control and experimental rework samples. The Stranja emulsion had a higher fat content (20.2%) compared to the Bologna emulsion (11%). This study provides evidence about the possible danger when potentially contaminated rework is stored and then introduced into fresh product formulations.     

Survival of Campylobacter jejuni on vacuum or carbon dioxide packaged primal beef cuts stored at −1.5 °C

The ability of two Campylobacter jejuni strains (MOO3, a cattle isolate, and MOO8, a sheep isolate) to survive on chilled, preservatively packaged primal beef cuts was examined. Each of the strains was inoculated separately (10⁵ cfu g⁻¹) onto 500 g beef steaks, packaged under vacuum or 100% carbon dioxide, and stored, with uninoculated controls, for 41 days at −1.5 °C. Bacterial numbers were determined at 0, 1, 3, 6, 13, 20, 27, 34 and 41 days by dilution, plating on both Columbia Sheep Blood Agar and Campylobacter Blood-Free Selective Agar and incubation at 42 °C for 48 h under microaerophilic conditions. In addition, an aerobic count on all samples was determined by dilution, plating on Plate Count Agar and incubation at 25 °C for 72 h. No significant changes in numbers of the C. jejuni strains or aerobic bacteria occurred during storage at −1.5 °C on steaks packaged under either vacuum or carbon dioxide. The ability of these pathogens to survive standard preservative packaging conditions is different from that reported in the literature and therefore a cause for concern. Strict hygienic practice or the implementation of decontamination technologies are recommended as mechanisms to assure safety of meat with respect to this pathogen.     

Potential application of low dose gamma irradiation to improve the microbiological safety of fresh coriander leaves

A local market survey of fresh, raw coriander leaves, which is a component of many ready-to-eat, Indian dishes showed large variation in their bacterial load (7.0×10⁶–1.36×10⁸ cfu/gm) and mold and fungi (3.0×10³–1.0×10⁴ cfu/gm) and presence of potentially pathogenic bacteria such as faecal coliforms, Listeria and Yersinia. Conventional chlorination treatment affected the structural integrity of leaves leading to enhancement of rotting. Exposure to a low dose of 1 kGy was efficient for bacterial decontamination and elimination of potential pathogens without affecting the keeping quality of coriander leaves upto two weeks storage at 8–10 °C, measured visually in terms of degree of yellowing and rotting. Irradiation at higher doses led to the increased rotting during storage. The total chlorophyll contents as well its components, chlorophyll a and b did not change significantly on irradiation and subsequent storage. Similarly, the total carotenoid levels remained unaffected by exposure to 1 kGy dose, however, a dose dependent enhancement in their extractability was observed in irradiated leaves. No qualitative differences were observed in the GLC profile of volatile oils of control and irradiated (1 kGy) samples. There were no significant quantitative changes in the constituents of the major aroma compounds obtained from these two samples. Effects of irradiation on storage of the seasoning were also assessed.     

Quality deterioration of phane, the edible caterpillar of an emperor moth Imbrasia belina

The cause for the deterioration of quality in phane, the edible larva of the emperor moth, Imbrasia belina (Westwood) was investigated. Samples were subjected to bacteriological and mycological analyses. In addition insect pests which affect storage life of the product were also assessed. 70% of the bacterial isolates associated with phane were proteolytic and 75% were either chitinolytic, lipolytic or both. Most isolates were sporeformers. But, other Gram-positive and negative isolates were also present in significant numbers. The most frequent fungal isolates were species of Aspergillus, Penicillium, Fusarium, Cladosporium and phycomycetes. Some of the fungal isolates are known to be mycotoxin producers. The insect which were associated with phane were Dermestes maculatus, Sitophilus zeamais, Corcyra cephalonica, Tribolium confusum, Tribolium casteneum, Oryzaephilus surinamensis, Bracon hebetor, Anisopteromalus cavandrae, and Stathmopoda species. Mites were also found infesting stored phane. The postharvest deterioration of phane appeared to be a concerted effort by the bacteria, moulds and insects.     

Elimination of Yersinia enterocolitica on carrots (Daucus carota L.) by using household sanitisers

In this study, the effects of lemon juice, the mixture of lemon juice–vinegar (1:1) and lemon dressing against Yersinia enterocolitica on carrot were investigated. Carrots inoculated with Y. enterocolitica cells (approximately 10⁶ cfu/ml) were treated with 100%, 75% and 50% lemon juice, a mixture of lemon juice–vinegar, and lemon dressing for 0, 15, 30 and 60 min. Enumeration of Y. enterocolitica populations on CIN agar beside TSA agar by using two methods as then performed. One hundred percent lemon juice was the most effective agent used, completely inhibiting viable cells of Y. enterocolitica on carrot after 15 min exposure. Although no growth was observed on carrots treated with 100% lemon juice for 15 min, there was no statistical difference between the antibacterial effects of 100% lemon juice, 75% lemon juice, the mixture of lemon juice–vinegar and lemon dressing whilst the effect of 50% lemon juice was statistically different from those solutions (P < 0.05) and its definite inhibitive activity was seen after 60 min treatment.     

Effects of some Chinese medicinal plant extracts on five different fungi

Chinese medicinal plant extracts were screened against some fungal strains, such as Aspergillus niger, Botrytis cinerea, Fusarium moniliforme, Glomerella cingulata, and Phyllosticta caricae. Plants were extracted with hot water, 80% methanol or acetone. Aliquots of the extracts at variable concentrations were then incubated with different fungal strains, and the minimum inhibitory concentrations (MICs) of each plant extract determined. In this study, the methanol extracts of Cinnamomum cassia had MIC values of 13.3 mg ml⁻¹, when tested against F. moniliforme and P. caricae. The acetone extracts of C. cassia had MIC values of 8.3 mg ml⁻¹ and 10 mg ml⁻¹ respectively, when tested against B. cinerea and G. cingulata. The hot water extracts of C. cassia inhibited significantly the growth of A. niger, B. cinerea, F. moniliforme, and P. caricae with MIC values at 10, 11.7, 5, and 6.7 mg ml⁻¹ respectively. The acetone extracts of Curcuma longa inhibited effectively P. caricae with the MIC value at 6.7 mg ml⁻¹. To determine the stability, various plant extracts were stored at 4 and 25 °C over a period of one month and their effects on fungal growth examined. Results show that the acetone extracts of Cu. longa and Coptidis rhizoma maintained their activity against fungal strains when stored at 4 °C, but not at 25 °C. The methanol extracts of C. cassia lost a great portion of inhibitory activities but not all, after stored at 4 °C and 25 °C for one month. The effect of various combinations of these extracts on antimicrobial activity has also been examined. The combinations of herb extracts showed higher inhibitory effect towards tested fungi than that of individual extract. Results from these findings suggest that these herbal extracts may be used as natural antifungal agents to inhibit growth of foodborne pathogen.     

An assessment of the microbial quality of the air within a pork processing plant

The aim of this study was to assess microbial quality of the air in a pork processing plant and from visual inspection to identify factors which may contribute to increase/decrease air-borne contamination. Total viable count (TVC), total coliform count (TCC) and the presence of Staphylococcus, Listeria and Salmonella species were used to evaluate the microbial quality of the air at five locations in the plant, at five time points during production. A visual inspection was used to identify risk factors which may increase the micro flora of the air in the plant. The highest TVC (133 cfu m⁻³), coliform counts (8 cfu m⁻³) and Staphylococcus aureus counts (8 cfu m⁻³) were found in the cooking area, blast chill and raw areas respectively. The higher levels of TVC, coliforms and Staphylococcus could most likely be attributed to people in the area, condensation and mechanically generated aerosol respectively although factors such as psychrometric properties of air and building ventilation factors which were outside of the scope of the current investigation would also need to be considered before a definite conclusion could be made in this regard. Listeria and Salmonella were not detected in the air in the plant. However, the inspection suggested the air in the raw area to be most at risk of microbial contamination, due to higher levels of microbial sources. Overall, microbial levels in the air were low, which suggests that the current control measures such as the positive air pressures from high-risk to low-risk, internal separators and closed drains were effective in reducing the microbial contamination in the air of the plant.     

Disinfection efficacy of slightly acidic electrolyzed water on fresh cut cabbage

A chlorine sanitizer that gives high disinfection efficacy with minimal available chlorine has a potential to be an environmentally-friendly method for disinfection of vegetables. In the present study, disinfection efficacy of slightly acidic electrolyzed water (SlAEW: pH 6.1, 20 mg/L available chlorine) produced by electrolysis for fresh cut cabbage was compared to that of sodium hypochlorite solution (NaOCl solution: pH 9.6, about 150 mg/L available chlorine). SlAEW reduced about by 1.5 log CFU/g for total aerobic bacteria and 1.3 log CFU/g for moulds and yeasts, compared to fresh cut cabbage before dipping. Statistical analysis of the results showed that the disinfectant efficacy of SlAEW was equivalent to or higher than that of NaOCl solution. Results also indicated that SlAEW under shaded and sealed conditions could keep its available chlorine during storage.     

Haematoporphyrin- and sodium chlorophyllin-induced phototoxicity towards bacteria and yeasts – a new approach for safe foods

Alternative methods for the decontamination of foods and surfaces in the food processing industry are under research. We introduce a new approach: the use of visible light plus photosensitizers, the photodynamic effect. First, we established an experimental model to examine the photosensitivity of immobilized micro-organisms. We tested subsequently several Gram-positive bacteria and yeasts for their photosensitivity after incubation with haematoporphyrin (HP) and sodium chlorophyllin (CHL). The survival levels of the bacteria fixed on solid media ranged from 0.0006% to 0.08% (3–5 log10 inactivations), and those of the yeasts from <0.1% to 50% (0.3–3 log10 inactivations) under the experimental conditions chosen.