In vitro evaluation of antibacterial and antioxidant activities of the essential oil and methanol extract of endemic Zataria multiflora Boiss

The present study was conducted to evaluate in vitro antibacterial and antioxidant properties of essential oil and methanol extracts from a unique and endemic plant, Zataria multiflora Boiss. The antibacterial test results showed that the essential oil of the plant strongly inhibited the growth of all of the microorganisms studied especially the Gram-negative strains. The polar fraction of methanol extract has been effective against Gram-positive strains, while the non-polar fraction has shown activity similar to essential oil. The antioxidant potential of the samples was evaluated using two separate methods, inhibition of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ammonium thiocyanate systems. Sub fractions of the methanol extract were able to reduce the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) with an IC₅₀ of 11.7 ± 1.58 and 16.2 ± 1.61 μg/ml, respectively for non-polar and polar ones, which the activity of the latter almost is equal to synthetic antioxidant BHA (18.2 ± 1.94 μg/ml). Inhibition values of linoleic oxidation were calculated to be 82.4% and 80.3% for the polar and non-polar fractions, respectively. The essential oil to be showed more inhibition (89.7 ± 2.5), similar to the synthetic antioxidants BHA (97.8 ± 2.94) and ascorbic acid (93.2 ± 2.1). The chemical composition of hydrodistilled essential oils of Z. multiflora was analyzed by GC/MS. A total of 25 compounds representing 99.78% of the oil were identified: thymol (37.59%), carvacrol (33.65%); para-cymene (7.72%), γ-terpinene (3.88%) and β-caryophyllene (2.06%) were the main components comprising 84.9% of the oil. Results here show that the essential oil and methanol extract of Z. multiflora possess antioxidant and antibacterial activity, and therefore it could be used as a natural preservative ingredient in food and/or pharmaceutical industries.     

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.     

Curcuma longa L. essential oil composition,antioxidant effect,and effect on Fusarium verticillioides and fumonisin production

Essential oils may be an alternative to the use of synthetic fungicides for the control of fungi involved in agricultural product deterioration. The aim of the present study was to evaluate the composition and antioxidant effect of turmeric essential oil and its antifungal and antimycotoxigenic action on Fusarium verticillioides (Sacc.) Nirenberg. The essential oil major components were α-turmerone (42.6%), β-turmerone (16.0%) and ar-turmerone (12.9%). The half-maximal inhibitory concentration (IC₅₀) for the radical scavenging capacities of 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were 0.54 and 10.03 mg/ml, respectively, indicating good antioxidant activity. The application of 17.9 and 294.9 μg/ml of turmeric essential oil decreased the development of F. verticillioides by 56.0 and 79.3%, respectively, when compared with the fungal control. The scanning electron microscopy demonstrated that the oil decreased the thickness and the length of the microconidia. Ergosterol production significantly decreased (p < 0.05) in groups treated with the essential oil relative to the control, indicating an effect of the oil on fungal biomass. The production of B₁ and B₂ fumonisins was significantly inhibited (p < 0.05) in groups treated with the essential oil. The results suggest that turmeric essential oil has antioxidant, antifungal and antimycotoxigenic activities.     

Characteristics of Bacillus cereus isolates from legume-based Indian fermented foods

An antibiogram of 48 strains of Bacillus cereus isolated from 6 different kinds of legume-based Indian fermented foods (amriti, dhokla, dosa, idli, papad and wadi) was generated against 18 different antibiotics that are commonly used against foodborne diseases, mainly gastroenteritis. Each of the isolates was found to be resistant against at least nine different antibiotics. Production of extracellular enzymes, namely protease, lipase and amylase by 33%, 27% and 46%, respectively, of the isolates indicates their potentiality for food spoilage. In brain–heart infusion broth supplemented with glucose, the D_100 °C-values for the tested 12 strains ranged from 3.0 to 9.2 min. In nutrient broth, the minimum and maximum pHs permitting growth of B. cereus were 5.3 and 11.6, respectively. The minimum inhibitory concentrations of sodium chloride, benzoic acid and sorbic acid for the growth of the isolates were 65–85 mg ml⁻¹, 400–700 μg ml⁻¹ (pH 5.0–4.2) and 500–600 μg ml⁻¹ (pH 5.0–4.8), respectively. Of the tested 10 strains, eight were resistant to 300 μg nisin ml⁻¹ (pH 5.0). While studying the combined effect of selected hurdles on the growth of an isolate, the judicious combination considered was 20 mg sodium chloride, 300 μg benzoic acid and 25 μg nisin ml⁻¹ at pH 5.6. The whole-cell protein fingerprinting (WCPF) analysis using SDS–PAGE revealed a high level of diversity among the isolates. At 60% similarity level, the WCPF profiles could be grouped into four major clusters which were divided into 34 subclusters. Most of the subclusters were source-wise homogeneous.     

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.     

Antifungal activity of thyme, summer savory and clove essential oils against Aspergillus flavus in liquid medium and tomato paste

Antifungal activity of essential oils of thyme, summer savory and clove were evaluated in culture medium and tomato paste. Aspergillus flavus were inoculated in Sabouraud Dextrose Broth and tomato paste and then 0, 50, 200, 350 and 500 ppm of essential oils were added to each sample and then kept at 25 ± 0.5 °C for 2 months. Results showed that all essential oils could inhibit the growth of A. flavus and the thyme oil and summer savory, showed the strongest inhibition at 350 ppm and 500 ppm, respectively. Taste panel evaluations were carried out in a tomato ketchup base, and the percent of inhibition of each essential oil in tomato paste was lower than culture medium. Taste panel was carried out and sample with 500 ppm thyme oil was accepted by panelists.     

Reducing nitrite content in hot dogs by hurdle technology

The objective of the present study was to reduce nitrite content in hot dogs using hurdle technology without sacrificing product safety and quality. In the present study, the water activity of the hot dog was adjusted to 0.95 by the addition of humectants. Although the pH at the hot dog was adjusted with Glocono-delta-lacton to 5.4, the product had (p > 0.05) the least acceptance on account of the organoleptic changes (sour taste). Moreover, the temperature of 80 ± 1 °C for an hour with the aim of achieving an internal temperature of 75 °C was applied. Subsequently, the temperature of the hot dog samples reduced to around 5–6 °C within 40–45 min, and afterwards the sausages were kept at chilled temperature (>3 °C but 10 °C) throughout their shelf life. There was a decrease in total aerobic counts in hurdle treated hot dogs (with 50 ppm nitrite), compared to the control (with 120 ppm nitrite), whereas Clostridium perfringens counts and Clostridium botulinum detection were the same (p < 0.05) in both hurdle treated and control samples. The obtained results of present study clearly showed that both hurdle treated sample and control had the same (p < 0.05) overall acceptability and sensory attributes.     

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.     

Oxidative Dehydrogenation of Methanol on Chromium Oxide/Montmorillonite K10 Catalysts

Methanol conversion was carried out on a mesoporous material—chromia/montmorillonite K10 (MK10)—in a pulse microcatalytic system. Methanol was converted to formaldehyde and ethylene by two different mechanisms. Methanol dehydrogenation increases by increasing reaction temperature (300-400°C) and as chromia loading decrease. On the other hand, the dehydration of methanol occurs at a higher temperature (400-500°C) and as chromia loading increase, 3-18% Cr. Redox and exposed nonredox Cr³⁺ are responsible for formaldehyde formation. There is a relationship between increased C₂H₄ production and the increase of Cr⁶⁺ phase according to the acidity of chromia catalysts 34 and 76 μL tert-Butylamine/g catalyst for 3% Cr and 18% Cr, respectively. Formaldehyde formation is diffusionally controlled at high temperatures (400-500°C) and kinetically controlled at a lower reaction temperature (300-400°C), while methanol dehydration to ethylene is surface reaction controlled at 400-500°C.     

Essential oils composition,antioxidant and antimicrobial activity of the leaves and flowers of Chaerophyllum macropodum Boiss

This study reports the essential oils chemical composition and in vitro antioxidant and antimicrobial potentials of the leaves and flowers of Chaerophyllum macropodum. GC and GC/MS analysis of the plant essential oils led to the identification of 49 components making 98.3–99.4% of its oils. The main constituents of the essential oils were trans-β-farnesene, trans-β-ocimene, β-pinene, limonene, spathulenol and myrcene constituting 49.6–73.1% of the oils. The extracts from the leaves and flowers showed moderate antioxidant activities in 1,1-diphenyl-2-picrylhydrazyl (DPPH) test (IC₅₀ values = 196.8 and 167.1 μg/ml respectively) and β-carotene/linoleic acid assay (inhibitions percentages = 69.9% and 62.7% respectively), but the essential oils were almost inactive in these tests. On the other hand, only the essential oils of the plant showed considerable antimicrobial activity against most of the tested microorganisms.     

Comparative control of the bioactivity of some frequently consumed vegetables subjected to different processing conditions

The main aim of this investigation was to find processing conditions and to control them, which maximally preserve bioactive compounds and antioxidant activity of garlic and onions. Garlic, white and red onions were subjected to bleaching and boiling. The contents of polyphenols, flavonoids, flavanols, tannins, corresponding antioxidant activities and their correlation coefficients were determined in various methanol and acetone extracts. The antioxidant activity was determined by 2, 2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH), Ferric-reducing/antioxidant power (FRAP) and Cupric reducing antioxidant capacity (CUPRAC) antioxidant assays. It was found that bleaching for 90″ most fully preserves polyphenols (8.25, 9.75 and 11.98 vs. 9.00, 10.52 and 15.87 mg GAE/g DW and the level of antioxidant activity – 8.82, 22.50 and 23.90 vs. 9.00, 23.05 and 24.30 μM TE/g DW of DPPH in extracts of treated samples with 100% of methanol vs. raw garlic, white and red onions, respectively. In conclusion, comparative control shows that bleaching for 90″ of all studied vegetables most fully preserves contents of bioactive compounds and the level of antioxidant activity. Extraction of bioactive compounds with 100% methanol was more effective than with 50% methanol and 100% acetone.     

Analysis of 140 pesticides from conventional farming foodstuff samples after extraction with the modified QuECheRS method

Pesticides in foodstuff are becoming a major issue due to their intensive use in agriculture. Thus an appropriate control of their residues in food samples has to be operated. In this study we analysed 105 pesticides with GC/SQ-MS and 46 pesticides with HPLC/IT-MS after extraction with the QuECheRS method in four matrices (grape, lemon, onion and tomatoes). For GC-amenable substances, the LOD and LOQ ranged from 0.4 to 48.2 μg/kg and from 1.2 to161 μg/kg, respectively. For HPLC-amenable substances, they varied from 1.0 to 115 μg/kg and from 3.3 to 382 μg/kg, respectively. With GC/MS, 61–82% of the substances showed a recovery in the range of 70–110% and 6–30 % presented a recovery higher than 110% at the 500 μg/kg fortification level. With HPLC/MS, 87–93% of the substances presented recoveries in the range of 70–110% at the 500 μg/kg fortification level compared to 78–85% at the 50 μg/kg fortification level. Lemon and onion showed poor recoveries but are known to be difficult matrices (high acidic and high sulfur content, respectively). The method was proved to be repeatable with RSD lower than 20% at 500 μg/kg and lower than 15% at 50 μg/kg with both devices.     

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).     

ON THE DETERMINATION OF SURFACE FREE ENERGY OF COAL BY MEANS OF THE DERIVATOGRAPH

The calculations of the dispersion γC^d and nondispersion (polar γC^p components of surface free energy of coal on the basis of adsorption measurements of nonpolar (n-heptane) and polar (methanol, propanol, water) liquid vapours a 20°C are presented. Average values ( γC^d = 45.1 mJ/m² and γC^p = 13.2 mJ/m²) are in good agreement with literature data calculated on the basis of separate and independent measurements. The heterogeneous nature of coal surface has been confirmed from derivatographic measurements.     

Effect of nisin on the storage of sous vide processed Korean seasoned beef

Seasoned beef called Jangzorim in Korea is produced by boiling in soy sauce, and is a popular food in Korea. The aim of this study is to evaluate the microbial safety and physical qualities of sous vide processed seasoned beef, and the effect of nisin during storage. Sous vide processed packages with or without nisin (100 IU or 500 IU) were stored at 4 °C or 25 °C for 60 days, and samples measured for quality at regular intervals throughout this storage period. In the case of 25 °C storage, the number of mesophilic microorganisms in seasoned beef packages without nisin increased markedly, but with nisin there was no observed increase. Psychrotrophic microorganisms, anaerobic microorganisms, and B. cereus cells showed similar trends, although C. perfringens was not detected in all samples. At 25 °C storage, changes in the cutting force of packages containing nisin showed no significant change, packages without nisin decreased markedly. The colour of packages without nisin showed a drastic decrease in lightness (‘L’) while no changes were observed in packages with nisin.     

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.     

Antioxidant and antimicrobial activities of leafy green vegetable extracts and their applications to meat product preservation

Leafy green vegetables (LGV) are rich in phenolic compounds that have a wide range of biological functions, including antioxidant and antimicrobial activities. Our first goal was to evaluate the antioxidant and antimicrobial activities of 70% ethanolic extracts of ten LGV commonly consumed in East Asia. To determine antioxidant activity, we measured total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2-azinobis-3 ethyl benxothiazoline-6-sulphonic acid (ABTS) cation decolorization activity, and reducing power. For the analysis of antimicrobial activity, the inhibitory effects of the extracts against Escherichia coli, Salmonella enterica, Shigella flexneri, Listeria monocytogenes, Staphylococcus aureus, and Bacillus subtilis were evaluated using agar well diffusion and broth-microdilution tests. Among all LGV, extracts of chamnamul (Pimpinella brachycarpa) and fatsia (Aralia elata) exhibited outstanding antioxidant and antimicrobial properties, and we thus investigated the influences of these extracts on lipid oxidation and microbial criteria in raw beef patties. The extracts and butylated hydroxytoluene (BHT, a positive control) were individually added to patties at both 0.1% and 0.5% (w/w) concentrations and the patties were stored at 4 °C for 12 days. The color parameters and thiobarbituric acid reactive substances (TBARS) values were monitored periodically, and a microbial analysis was performed. The addition of extracts and BHT resulted in concentration-dependent decreases in TBARS values and in the number of microorganisms in the beef patties and also improved meat color stability. The fatsia extract had more effective antioxidant and antimicrobial activities than the chamnamul. We conclude that extracts of LGV, especially fatsia, have potential as natural preservatives for meat products.     

Neural network modelling of the fate of Salmonella enterica serovar Enteritidis PT4 in home-made mayonnaise prepared with citric acid

Fifty-four mayonnaise recipes were generated by the central composite design and tested for microbiological safety at two temperatures (5 and 22 °C). The content of oil: (150–350 ml), egg yolk (10–35 g), citric acid (4.98% w/v) (10–40 g), salt (0–3 g), mustard (0–2 g), sugar (0–1 g) and white pepper (0.25 g) varied among the different recipes. The fate of Salmonella enterica serovar Enteritidis PT4 in mayonnaise products was investigated by both viable count and presence/absence tests and modelled by neural networks. This study demonstrated that feed-forward neural networks were incapable of modelling the survival/growth curves of S. Enteritidis PT4 as a one-step-procedure model, but were capable of modelling the presence/absence of the organism.     

Antimicrobial and antioxidant activities of Chinese sumac (Rhus typhina L.) fruit extract

Sumac plant (Rhus typhina) is mainly used for forestation and gardening, whereas its fruit can be used to prepare a kind of beverage called “sumac-ade” and to treat gastrointestinal disorders. This study aimed at assaying the antimicrobial and antioxidant activities of R. typhina growing in China. The antimicrobial activity of R. typhina fruit extract was tested against twelve strains including Gram-positive and Gram-negative bacteria as well as yeasts. The extract showed a strong antimicrobial activity with a concentration-dependence and a broad antimicrobial spectrum for all tested bacteria species. Bacillus cereus and Helicobacter pylori were found to be the most sensitive Gram-positive and Gram-negative bacteria respectively, with a minimum inhibitory concentration (MIC) of 0.10%. However, yeasts exhibited much lower sensitivity, with MICs of 0.60–0.75%. Furthermore, the antioxidant activity of the extract was investigated, including scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (0.016 mg/ml as IC₅₀ value) and reducing power (IC₅₀ value of 0.041 mg/ml). To our knowledge, this is the first report on the biological activities of R. typhina fruit extract and our findings suggest the possibility of using the fruit of R. typhina as a novel source of natural antimicrobial and antioxidant agents for the food and pharmaceutical industries.     

Occurrence of contaminants in foods commonly consumed in Bahrain

The occurrence of mycotoxins (aflatoxins, zearalenone, deoxynivalenol), heavy metals and pesticide residues in 198 susceptible food commodities available in Bahrain was determined. Aflatoxins were found in many of the foods tested and three samples of red chili powder (35.9, 52.6 and 69.2 ng/g), one sample of black pepper powder (27.7 ng/g) and one sample of unshelled pistachio nuts (81.6 ng/g) exceeded the maximum allowable limit of aflatoxins. Zearalenone was present in some samples including cornflakes (3.1 ng/g) and crushed wheat (0.3 ng/g). Although many samples contained heavy metals, one sample of cinnamon powder (13.0 μg/g) and one sample of black pepper powder (11.2 μg/g) exceeded the maximum allowable limit for lead. The average levels of cadmium were highest in cinnamon powder (0.3 μg/g) and ginger powder (0.3 μg/g). Some amount of pesticides was found in cumin powder (0.06 μg/g of lindane), turmeric power (0.04 μg/g heptachlor) and coriander powder (0.4 μg/g permethrin). Almonds, peanuts, cashew nuts infant formulas were free of contaminants. Although the contamination of most foods in Bahrain was within the limit, strengthening of the food control systems is important.