Pasteurization of grapefruit juice using a centrifugal ultraviolet light irradiator

Studies are lacking on the nonthermal pasteurization of liquid foods using UV irradiators that centrifugally form very thin films to overcome the problem of limited penetration depth of UV. Grapefruit juice inoculated with Escherichia coli or Saccharomyces cerevisiae was processed at the following conditions: UV dose 4.8–24 mJ/cm²; treatment time 3.2 s, cylinder rotational speed 450–750 rpm, cylinder inclination angle 15–45°, outlet temperature 11 °C, and flow rate 300 ml/min, and was stored for 35 days. Appropriate dilutions of the samples were pour plated with TSA and TSA + 3% NaCl for E. coli and Sabouraud dextrose agar (SDA) and SDA + 5% NaCl for S. cerevisiae. Nonthermal UV processing at 19 mJ/cm², 450 rpm and 15° reduced E. coli in grapefruit juice by 5.1 log₁₀. A dose of 14 mJ/cm² reduced S. cerevisiae by 6.0 log₁₀. Inactivation increased linearly with increasing UV dose. The inactivations at 600 and 750 rpm were similar, and were better than at 450 rpm. The results at 30° and 45° were similar, and were better than at 15°. The occurrence of sublethal injury in either microorganism was not detected. Storing UV processed grapefruit juice at 4 and 10 °C reduced the surviving E. coli to below 1 log₁₀ cfu/ml in 14 days. Processing UV juice reduced the population of S. cerevisiae to less than 1 log₁₀ cfu/ml where it remained for 35 days during refrigerated storage. These results suggest that grapefruit juice may be pasteurized using a nonthermal UV irradiator that centrifugally forms a thin film.     

Synchronous front-face fluorescence spectroscopy as a promising tool for the rapid determination of spoilage bacteria on chicken breast fillet

In this work the potential of synchronous front-face fluorescence spectroscopy along chemometric methods was investigated for the determination of microbial load on chicken breast fillets stored aerobically at 5 °C during 0, 1, 2, 3, 5 and 8 days, and 15 °C for 0, 0.5, 1, 2, 3 and 5 days. Total viable count (TVC), Pseudomonas, Enterobacteriaceae and Brochothrix thermosphacta were determined on chicken breast fillets at each step of the 2 kinetics using culture dependent methods. Initial TVC was 3.4 log cfu/cm² and TVC reached 8.4 log cfu/cm² and 8.3 log cfu/cm² following 8 days at 5 °C and 2 days at 15 °C, respectively. In parallel, synchronous fluorescence spectra were recorded in an excitation wavelength range of 250-500 nm using offsets of 20, 40, 60,…, 180 nm between excitation and emission monochromators. PARAFAC (parallel factor) analysis allowed to capture the changes occurring in the synchronous fluorescence spectral data. The best PARAFAC models showed 3 and 2 components for kinetics recorded at 5 and 15 °C, respectively. PLSDA (partial least square discriminant analysis) was carried out to test the reallocation of the spectra of the individual samples within the six groups corresponding to the six investigated storage times and the results showed that 100% of good classifications were obtained using 4 PLS factors. Finally, N-PLS regression was used to predict the microbial counts for TVC, Pseudomonas, Enterobacteriaceae and B. thermosphacta from the spectral data. Good average recoveries of 100 to 102%, excellent correlations (R² = 0.99) and very small root mean squares errors (between 0.1 and 0.2 log cfu/cm²) of prediction were obtained from the spectral data sets recorded on samples stored at 5 °C and 15 °C for TVC, Pseudomonas, Enterobacteriaceae and B. thermosphacta.     

Inhibition of A. carbonarius growth and reduction of ochratoxin A by bacteria and yeast composites of technological importance in culture media and beverages

Five composites of yeast and six of bacterial isolates from fermented products were studied, in order to assess their ability to inhibit Aspergillus carbonarius growth and reduce OTA concentration in culture media and beverages. The antagonistic effect of the above composites against A. carbonarius growth was studied in synthetic grape medium of pH 3.5 and a_w 0.98, 0.95, 0.92 after incubation at 25 °C. Different combinations of initial inocula of bacteria or yeast composites and fungi were used (10² cfu/mL vs 10⁵ spores/mL; 10⁵ cfu/mL vs 10² spores/mL; and 10⁵ cfu/mL vs 10⁵ spores/mL). Regarding the OTA reduction experiment, 10³ and 10⁷ cfu/mL of the bacteria and yeast composites were inoculated in liquid media of different pH (3.0, 4.0, 5.0, and 6.1 or 6.5) and initial OTA concentration (50 and 100 μg/L) and incubated at 30 °C. Moreover, grape juice, red wine, and beer were supplemented with 100 μg/L of OTA and inoculated with composites of 16 yeasts (16YM) and 29 bacterial (29BM) strains (10⁷ cfu/mL) to estimate the kinetics of OTA reduction at 25 °C for 5 days. Fungal inhibition and OTA reduction were calculated in comparison to control samples. None of the bacterial composites inhibited A. carbonarius growth. The high inoculum of yeast composites (10⁵ cfu/mL) showed more efficient fungal inhibition compared to cell density of 10² cfu/mL. All yeast composites showed higher OTA reduction (up to 65%) compared to bacteria (2-25%), at all studied assays. The maximum OTA reduction was obtained at pH 3.0 by almost all yeast composites. For all studied beverages the decrease in OTA concentration was higher by yeasts (16YM) compared to bacteria (29BM). The highest OTA reduction was observed in grape juice (ca 32%) followed by wine (ca 22%), and beer (ca 12%). The present findings may assist in the control of A. carbonarius growth and OTA production in fermented foodstuffs by the use of proper strains of technological importance.     

Evaluation of kaolinite-based particle films to control Tribolium species (Coleoptera: Tenebrionidae)

Adults of Tribolium castaneum (Herbst), the red flour beetle, and Tribolium confusum (du Val), the confused flour beetle, were exposed to kaolinite-based particle film dusts. When beetles were continuously exposed to the hydrophobic particle film M-96-018 at the rate of 0.1-0.5 mg/cm², all the T. castaneum at 0.1 mg/cm² were dead after 3 days, but 40±13.8% of the exposed T. confusum were still alive after 7 days. At higher concentrations, all the T. castaneum were dead after 2 days, but 5-6 days of exposure were needed to kill all T. confusum. In a subsequent test, adults of both species were exposed for 8-72 h to 0.5 mg/cm² of the particle film M-96-018, removed, then held without food for 1 week. No T. castaneum survived, while survival of the T. confusum ranged from 0 to 55±17.3%, depending on the exposure interval. In a test conducted at controlled conditions of 40%, 57% and 75% r.h., 27°C, T. confusum were exposed for 8-72 h to the particle film M-96-018 and a hydrophilic particle film M-97-009 at the rate of 0.5 mg/cm², then removed and held either with or without wheat flour for 1 week. All the T. confusum exposed to the particle film M-97-009 usually survived, while survival of the T. confusum exposed to the particle film M-97-018 after the 1-week holding period increased with increasing relative humidity and with the presence of food. The particle film M-96-018 was effective against both the Tribolium species, and appears to have a potential for use in management programs to control beetles within storage facilities.     

Microbiological quality and potential public health risks of export meat from springbok (Antidorcas marsupialis) in Namibia

To assess the microbiological quality and safety of export game meat; i) a total of 80 pooled meat samples for aerobic plate count (APC) and Enterobacteriaceae ii) water used in harvesting and processing for microbiological quality and iii) meat and rectal contents for Salmonella spp. and Shiga toxin Escherichia coli (STEC) were evaluated in 2009 and 2010. No differences (p > 0.05) in the APCs were observed between the years, but the mean Enterobacteriaceae count for 2009 was 1.33 ± 0.69 log₁₀ cfu/cm² compared to 2.93 ± 1.50 log₁₀ cfu/cm² for 2010. Insignificant Heterotrophic Plate Count (HPC) levels were detected in 9/23 field water samples, while fecal bacterial (coliforms, Clostridium perfringens and enterococci) were absent in all samples. No Salmonella spp. was isolated and all E. coli isolates from meat were negative for STEC virulence genes (stx1, stx2, eae and hlyA), suggesting a negligible role by springbok in the epidemiology of STEC and Salmonella.     

Assessment of Escherichia coli O157:H7-specific bacteriophages e11/2 and e4/1c in model broth and hide environments

The efficacy of bacteriophages e11/2 and e4/1c as potential biocontrol agents for Escherichia coli O157:H7 in food applications was assessed under conditions relevant to the food chain environment. The stability of each phage was determined following exposure to varying environmental conditions (pH, temperature, water activity, and sodium chloride) and the ability of each phage to infect and reduce E. coli O157:H7 numbers under selected conditions was also examined. Both e11/2 and e4/1c significantly (p < 0.05) reduced numbers of E. coli O157:H7 when exposed to pH values ranging from pH > 4 to pH 9, temperatures from 4 °C to 37 °C, water activity values of 0.87 or 0.91 to 1.00 and NaCl concentrations of 1% to 2.5%. Subsequently, a cocktail of both phages was used (e11/2 and e4/1c) to assess reduction of E. coli O157:H7 on cattle hide pieces. This involved inoculating pieces of hide (20 × 20 cm) with E. coli O157:H7 (approximately 10⁶ cfu/cm²) which were subsequently treated with either a suspension of a phage cocktail, consisting of e11/2 and e4/1c (multiplicity of infection of 1000 and 10,000, respectively) or water or not treated. Two different investigations were carried out; immediately or 1 h after treatment application was performed in different experiments. Swab samples taken immediately after phage treatment showed no significant (p > 0.05) reduction of E. coli O157:H7 numbers compared to the water treated or untreated samples. However, an extended exposure time of 1 h following phage application revealed a significant reduction (p < 0.05) (1.5 log₁₀ cfu/cm² reduction) in E. coli O157:H7 numbers compared to the numbers recovered on samples treated with water only. These findings demonstrate the potential use of e11/2 and e4/1c phages as a biocontrol agent for E. coli O157:H7 within various stages of the food chain, including on cattle hide.     

Control of Listeriamonocytogenes on commercially-produced frankfurters prepared with and without potassium lactate and sodium diacetate and surface treated with lauric arginate using the Sprayed Lethality in Container (SLIC®) delivery method

Viability of Listeriamonocytogenes was monitored on frankfurters formulated with or without potassium lactate and sodium diacetate at a ratio of ca. 7:1 and treated with lauric arginate (LAE; 22 or 44 ppm) using the Sprayed Lethality in Container (SLIC®) delivery method. Without antimicrobials, pathogen numbers remained relatively constant at ca. 3.3 log CFU/package for ca. 30 d, but then increased to ca. 8.4 log CFU/package over 120 d. Regardless of whether or not lactate and diacetate were included, when treated with LAE, pathogen numbers decreased from ca. 3.3 log CFU/package to ca. 1.5 log CFU/package within 2 h, but then increased to 7.3 and 6.7 log CFU/package, respectively, after 120 d. When frankfurters were formulated with lactate and diacetate and treated with LAE, pathogen numbers decreased by ca. 2.0 log CFU/package within 2 h and remained relatively unchanged over the 120 d. These data confirm that LAE provides an initial lethality towards L. monocytogenes and when used in combination with reduced levels/ratio of lactate and diacetate as an ingredient for frankfurters provides inhibition throughout shelf life.     

Insecticidal activity of asarones identified in Acorus gramineus rhizome against three coleopteran stored-product insects

The insecticidal activities of Acorus gramineus rhizome-derived materials against adults of Sitophilus oryzae (L.), Callosobruchus chinensis (L.) and Lasioderma serricorne (F.) were examined using direct contact application and fumigation methods. The biologically active constituents of the Acorus rhizome were characterized as the phenylpropenes (Z)- and (E)-asarones by spectroscopic analysis. Responses varied with insect species, compound and exposure time rather than dose. In a filter paper diffusion test, (Z)-asarone caused 70% and 90% mortality against S. oryzae adults at 0.064 and 0.255 mg/cm² at 4 days after treatment, respectively, with 100% mortality at 7 days after treatment. (E)-Asarone at 0.255 mg/cm² was almost ineffective against S. oryzae adults at 7 days after treatment. Against C. chinensis adults at 0.064 mg/cm², (Z)- and (E)-asarones gave 100% mortality at 3 and 7 days after treatment, respectively. Against L. serricorne adults, (Z)-asarone gave 90% and 83% mortality at 0.255 and 0.064 mg/cm² at 7 days after treatment, respectively, whereas (E)-asarone at 0.255 mg/cm² was almost ineffective at 7 days after treatment. These results indicate that the toxicity of asarones might be due to the cis configuration rather than to the position of the double bond. In a fumigation test, (Z)-asarone at 0.577 mg/cm² was much more effective against adults of all three insect species in sealed containers than in open ones, indicating that the insecticidal activity of the compound was largely attributable to fumigant action.     

The effects of various antifungal additives on the fermentation and aerobic stability of corn silage

In 2 consecutive years, whole plant corn was ensiled in laboratory silos to investigate the effects of various silage additives on fermentation, dry matter (DM) recovery and aerobic stability. In yr 1, chopped forage was treated with 1) no additive (untreated, U), 2) Lactobacillus buchneri40788, 4 × 10⁵ cfu/g of fresh forage (LLB4), 3) L. buchneri 11A44, 1 × 10⁵ cfu/g (PLB), 4) Biomax 5 (Lactobacillus plantarum PA-28 and K-270), 1 × 10⁵ cfu/g (B5), 5) Silo Guard II (sodium metabisulfite and amylase), 0.05% of fresh forage weight (SG), 6) a buffered propionic acid-based additive, 0.1% (Ki-112), 7), sodium benzoate, 0.1% of fresh weight (SB), or 8) potassium sorbate:EDTA (1:1), 0.1% of fresh weight (PSE). Silage treated with LLB4 had the highest concentration of acetic acid compared with other treatments, and yeasts were undetectable in LLB4 (<log₂ cfu/g). Silages treated with SB and PSE had the highest concentrations of water-soluble carbohydrates, the greatest recoveries of DM, and the lowest concentrations of ethanol. Silages treated with B5, SG, and Ki-112 had no effects on fermentation, DM recovery, or aerobic stability. The aerobic stabilities of silages treated with LLB4, SB, and PSE were greatest among all treatments. In yr 2, treatments were: 1) U, 2) LLB4, 3) PLB, 4) PLB at 4 × 10⁵ cfu/g (PLB4), and 5) B5. Silages treated with L. buchneri had greater concentrations of acetic acid but lower concentrations of ethanol than did U- and B5-treated silages. Yeasts were undetected in all silages except in silage treated with B5, which had the poorest aerobic stability of all treatments. Treatments had no effect on DM recovery. Silages treated with PLB, PLB4, and LLB4 remained stable for >210 h.     

Potential of Escherichia coli O157:H7 to persist and form viable but non-culturable cells on a food-contact surface subjected to cycles of soiling and chemical treatment

Our aim was to assess the potential of Escherichia coli O157:H7 to persist in a processing environment. We studied E. coli behaviour under conditions modelling those of meat plants to establish one initial bacterial load that allows persistence and another that does not. Polyurethane coupons (3.5 cm²) were contaminated once with E. coli in meat exudate before being subjected daily to a cleaning product and a disinfectant, both at half the recommended in-use concentrations, and a further soiling with the exudate. This procedure aimed to model what occurs in harbourage sites. Because previous experiments showed that persistence could not be achieved at 15 °C (temperature of slaughter halls), we incubated the coupons at 20 °C. Viable cells were determined by ethidium monoazide-qPCR (EMA-qPCR). When the first chemical treatment (CT) was applied to 24-hour biofilms with 5.4 log CFU/cm², cells were no longer detectable after the first week. However, on 66-hour biofilms with 6.7 log CFU/cm², after initially decreasing, E. coli numbers reached 6.6 log CFU/cm² and 8.3 log viable cells/cm² on the 11th day. When E. coli was cultured with a Comamonas testosteroni previously shown to increase E. coli biofilm formation, and subjected to CT on alternate days, E. coli stabilized at 4.6 log CFU/cm² before the CT, from the 5th day of the experiment. The killing and detachment effects of the CT decreased over time and PCR quantification detected a resumption of growth after 2 days (CT on alternate days) or 3 days (daily CT). Intracellular pH (pHi) of individual cells was determined during an experiment in which the CT was applied on alternate days. The proportion of cells with no proton gradient towards the environment (pHi ≤ 5.4) increased after the CT as expected. But during the first week of the experiment only, a further increase in this proportion occurred 24 h after the CT, suggesting that some of the surviving viable but non-culturable cells finally died.This study shows that conditions leading to E. coli O157:H7 persistence are not likely to arise when good refrigeration and hygiene practices are applied, and highlights the usefulness of EMA or PMA-qPCR as a complement to CFU determination in studying bacterial survival after cleaning and disinfection.     

Effect of applying molasses or inoculants containing homofermentative or heterofermentative bacteria at two rates on the fermentation and aerobic stability of corn silage

This study determined how the fermentation and aerobic stability of corn silage are affected by treatment with molasses or 2 dual-purpose inoculants applied at or above the recommended rate. Corn forage (DeKalb 69-70) was harvested at 39% dry matter (DM) and ensiled after treatment with no additives (control, CON), molasses (MOL), Buchneri 500 inoculant, or Pioneer 11C33 inoculant. Molasses was applied at 3% of forage DM. Buchneri 500 was applied at the recommended rate of 8 mg/kg fresh forage to supply 1 × 10⁵ cfu/g of Pediococcus pentosaceus 12455 and 4 × 10⁵ cfu/g of Lactobacillus buchneri 40788 (BB) or at twice the recommended rate (DBB). Pioneer 11C33 inoculant was applied at the recommended rate of 1.1 mg/kg fresh forage to supply 1 × 10⁵ cfu/g of a mixture of Lactobacillus plantarum, L. buchneri, and Enteroccocus faecium (PN) or at twice the recommended rate (DPN). Each treatment was applied in quadruplicate and the treated forages were ensiled within 20-L mini silos for 135 d at 18 to 35°C. Molasses-treated silages had greater ash and starch concentrations than CON silages and greater lactate and ethanol concentrations than other silages. Like CON silages, MOL silages had high yeast counts (>10⁵ cfu/g); consequently, they deteriorated within 30 h as shown by temperature increase. Inoculant-treated silages had lower lactate to acetate ratios than CON or MOL silages largely because they had greater acetate concentrations. Consequently, all inoculant-treated silages had fewer yeasts (<10⁵ cfu/g) and were more stable (>30 h) than CON and MOL silages. When applied at recommended rates, PN and BB had similar effects on silage chemical composition, fermentation, fungal counts, and aerobic stability, except for a lower lactate concentration in PN silages. Concentrations of VFA, and NH₃-N, pH, and extent of aerobic stability were similar for PN, DPN, BB, and DBB silages. However, lactate concentration was greater in DPN than in PN. In conclusion, MOL application increased ethanol and lactate concentration and did not improve aerobic stability. Both dual-purpose inoculants made the fermentation more heterolactic and thereby improved the aerobic stability of corn silage. Doubling the rate of application of either inoculant did not further improve fermentation or aerobic stability.     

Effects of γ-irradiation on Listeria monocytogenes population,colour, texture and sensory properties of Feta cheese during cold storage

Feta, a white brine cheese, was produced and contaminated with Listeria monocytogenes. Contamination occurred either at the beginning (pre-process contamination) or at the end of Feta manufacturing (post-process contamination). In the first case the milk was contaminated with 10³ cfu/ml, and 2 months later, in the final product, the L. monocytogenes population was approximately 10⁵ cfu/g. In the second case, the brine (NaCl, 7% w/v), in which the Feta was packaged, was contaminated with 10³ cfu/ml. Contaminated Feta samples were vacuum-packaged and exposed to irradiation doses of 1.0, 2.5 and 4.7 kGy and stored at 4 °C for a month. In the pre-process contaminated samples none of the irradiation doses eliminated L. monocytogenes; however the highest dose reduced the viable population to a level which is in compliance with EC regulations. In the post-process contamination, the 2.5 kGy and 4.7 kGy doses reduced L. monocytogenes counts below the detection limit. Irradiation had no effect on the texture of Feta. Irradiation at 4.7 kGy increased Feta's redness and decreased its yellowness and lightness. Sensorial analyses showed that at the 4.7 kGy dose, the aroma profile of Feta was temporarily affected, since it was restored after 30 days of cold storage.     

Fate of Listeria monocytogenes during freezing,thawing and home storage of frankfurters

Little information is available regarding the fate of Listeria monocytogenes during freezing, thawing and home storage of frankfurters even though recent surveys show that consumers regularly store unopened packages in home freezers. This study examined the effects of antimicrobials, refrigerated storage, freezing, thawing method, and post-thawing storage (7 °C) on L. monocytogenes on frankfurters. Inoculated (2.1 log CFU/cm²) frankfurters formulated without (control) or with antimicrobials (1.5% potassium lactate plus 0.1% sodium diacetate) were vacuum-packaged, stored at 4 °C for 6 or 30 d and then frozen (−15 °C) for 10, 30, or 50 d. Packages were thawed under refrigeration (7 °C, 24 h), on a countertop (23 ± 2 °C, 8 h), or in a microwave oven (2450 MHz, 1100 watts, 220 s followed by 120 s holding), and then stored aerobically (7 °C) for 14 d. Bacterial populations were enumerated on PALCAM agar and tryptic soy agar plus 0.6% yeast extract. Antimicrobials completely inhibited (p < 0.05) growth of L. monocytogenes at 4 °C for 30 d under vacuum-packaged conditions, and during post-thawing aerobic storage at 7 °C for 14 d. Different intervals between inoculation and freezing (6 or 30 d) resulted in different pathogen levels on control frankfurters (2.1 or 3.9 log CFU/cm², respectively), while freezing reduced counts by <1.0 log CFU/cm². Thawing treatments had little effect on L. monocytogenes populations (<0.5 log CFU/cm²), and post-thawing fate of L. monocytogenes was not influenced by freezing or by thawing method. Pathogen counts on control samples increased by 1.5 log CFU/cm² at d-7 of aerobic storage, and reached 5.6 log CFU/cm² at d-14. As indicated by these results, consumers should freeze frankfurters immediately after purchase, and discard frankfurters formulated without antimicrobials within 3 d of thawing and/or opening.     

Effect of the ripening time under vacuum and packaging film permeability on processing and quality characteristics of low-fat fermented sausages

The effect of vacuum ripening of low-fat fermented sausages packaged in films with different permeabilities on their microbiological, physicochemical and sensorial characteristics was studied. High-fat control sausages were produced with 30% initial fat and low-fat sausages with 10% initial fat. The low-fat sausages were separated into: (a) non-packaged (control) and (b) packaged under vacuum on 7th, 12th and 17th day of processing, remaining under vacuum during the ripening period for 21, 16 and 11 days, respectively, in three different oxygen (100, 38 and ? 5 cm³/m²/24 h/1 atm) and water vapour (4.5, <2.5 and 1 g/m² 24 h) permeability plastic bags. Vacuum packaging reduced (p < 0.05) the weight loss, the hardness and extent of lipid oxidation in the sausages, increased (p < 0.05) their lightness, but had no effect (p > 0.05) on the redness, compared to the control sausages. Packaging low-fat fermented sausages under vacuum for the last 11 days of ripening in packaging film with high permeability increased (p < 0.05) the lactic acid bacteria count. The same product packaged in film with medium permeability had a higher (p < 0.05) Micrococcaceae count and the same (p > 0.05) hardness and overall acceptability as the high-fat control sausages. A ripening time of 11 days and the medium packaging film permeability were the most appropriate conditions for the vacuum packaging of low-fat fermented sausages.     

Bacterial inactivation in fruit juices using a continuous flow Pulsed Light (PL) system

In this work, the susceptibility to pulsed light (PL) treatments of both a Gram-positive (L. innocua 11288) and a Gram-negative (E. coli DH5-??) bacteria inoculated in apple (pH = 3.49, absorption coefficient 13.9 cm^− 1) and orange juices (pH = 3.78, absorption coefficient 52.4 cm^− 1) was investigated in a range of energy dosages from 1.8 to 5.5 J/cm². A laboratory scale continuous flow PL system was set up for the experiments, using a xenon flash-lamp emitting high intensity light in the range of 100-1100 nm. The flashes lasted 360 ??s at a constant frequency of 3 Hz.The results highlighted how the lethal effect of pulsed light depended on the energy dose supplied, the absorption properties of liquid food as well as the bacterial strain examined. The higher the quantity of the energy delivered to the juice stream, the greater the inactivation level. However, the absorbance of the inoculated juice strongly influenced the dose deliver and, therefore, the efficiency of the PL treatment. Among the bacteria tested, E. coli cells showed a greater susceptibility to the PL treatment than L. innocua cells in both apple and orange juices. Following treatment at 4 J/cm², microbial reductions in apple and orange juices were, respectively, 4.00 and 2.90 Log-cycles for E. coli and 2.98 and 0.93 Log-cycles for L. innocua.Sublethally injured cells were also detected for both bacterial strains, thus confirming that membrane damage is an important event in bacterial inactivation by PL.     

Insecticidal and antifeedant activities of medicinal plant extracts against Attagenus unicolor japonicus (Coleoptera: Dermestidae)

Methanol extracts from 28 medicinal plant species were tested for their insecticidal and antifeedant activities against Attagenus unicolor japonicus larvae by using a fabric-piece bioassay. Responses varied according to plant species, dose, and exposure time. Methanol extract of Allium sativum bulb gave 93% mortality at 5.2 mg/cm² 7 days after treatment (DAT). Eugenia caryophyllata bud extract produced 100% mortality at 2.6 mg/cm² 14 DAT and 90% mortality at 1.3 mg/cm² 21 DAT. Foeniculum vulgare fruit extract gave 67% and 100% mortality at 5.2 mg/cm² 21 and 28 DAT, respectively. Methanol extracts of Angelica dahurica root, Lysimachia davurica whole plant, and Nardostachys chinensis rhizome exhibited complete antifeedant activity at 1.3 mg/cm² over a 30-day period. The plant extracts described merit further study as potential insecticidal or antifeedant agents against A. unicolor japonicus.     

Acaricidal activity of fennel seed oils and their main components against Tyrophagus putrescentiae, a stored-food mite

The acaricidal activities of components derived from Foeniculum vulgare (fennel) seed oils against Tyrophagus putrescentiae adults were examined using direct contact application and compared with those of the compounds benzyl benzoate, dibutyl phthalate and N,N-diethyl-m-toluamide. The biologically active constituent of the F. vulgare seeds was characterized as (+)-carvone by spectroscopic analyses. On the basis of LD₅₀ values, the compound most toxic to T. putrescentiae was naphthalene (4.28 μg/cm²) followed by dihydrocarvone (4.32 μg/cm²), (+)-carvone (4.62 μg/cm²), (−)-carvone (5.23 μg/cm²), eugenol (10.62 μg/cm²), benzyl benzoate (11.24 μg/cm²), thymol (11.42 μg/cm²), dibutyl phthalate (13.11 μg/cm²), N,N-diethyl-m-toluamide (13.53 μg/cm²), methyl eugenol (39.52 μg/cm²), myrcene (39.88 μg/cm²) and acetyleugenol (72.24 μg/cm²). These results indicate that acaricidal activity of the F. vulgare seed oil could be caused by carvone and naphthalene of which the former is likely to be more important because it is 74.7 times more abundant than naphthalene. Carvone and naphthalene merit further study as potential stored-food mite control agents or as lead compounds.     

Efficacy of neutral electrolyzed water for sanitization of cutting boards used in the preparation of foods

The effectiveness of neutral electrolyzed water (NEW) to sanitize cutting boards used for food preparation was investigated. Cutting boards made of hardwood and bamboo were inoculated with Escherichia coli K12 and Listeria innocua, dried for 1 h, washed, rinsed and sanitized with NEW, sodium hypochlorite (NaClO) solution, or tap water (control). After each washing protocol, surviving bacterial populations were determined. Results showed that both NEW and NaClO sanitizing solutions produced similar levels of bacterial reductions. In manual washing, the population reductions by NEW and NaClO were 3.4 and 3.6 log₁₀ CFU/100 cm² for E. coli, and 4.1 and 3.9 log₁₀ CFU/100 cm² for L. innocua, respectively. In the automatic washing, the reductions by NEW and NaClO were 4.0 and 4.0 log₁₀ CFU/100 cm² for E. coli, and 4.2 and 3.6 log₁₀ CFU/100 cm² for L. innocua, respectively. No significant differences (P > 0.05) were observed in surviving bacteria counts when comparing board material types.     

Effects of bactericides and modified atmosphere packaging on shelf-life of Chinese shrimp (Fenneropenaeus chinensis)

Effects of different bactericides and modified atmosphere packaging (MAP) on aerobic plate counts (APCs), total volatile base-nitrogen (TVB-N) and organoleptic evaluation of overall acceptable score (OA score) of Chinese shrimp (Fenneropenaeus chinensis) during cold storage were investigated. Results indicated that APC in MAP(40%CO₂/30%O₂/30%N₂) shrimp treated with compound bactericide reached 10⁷ cfu/g on the 13th day of storage, while that of ozonated water or water control treatments exceed 10⁷ cfu/g on the 9th day. APC in shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide reached close to 10⁷ cfu/g at day 13, while that of air treatment exceed 10⁷ cfu/g. TVB-N value in MAP(40%CO₂/30%O₂/30%N₂) shrimp treated with compound bactericide was slightly higher than the upper threshold of 30 mg/100 g on the 17th day, while that of ozonated water treatment or water control increased to or over the threshold value on the 9th day. TVB-N value in shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide were significantly lower than that of air control on the 17th day (P ≤ 0.01), with a value of 33.6 mg/100 g and 42-47.6 mg/100 g respectively, compared to 78.4-86.8 mg/100 g in air control. The lowest OA score of MAP(40%CO₂/30%O₂/30%N₂) whole and decapitated shrimps treated with compound bactericide appeared on the 17th and 21th day, respectively, compared with the 9th day in whole shrimp and the 13th day in decapitated shrimps treated with ozonated water and water control. The lowest OA score of whole and decapitated shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide appeared on the 17th and 21th day, respectively, compared with the 13th and 17th day in air control. In conclusion, when combined the parameters determined together, the shelf-life of Chinese shrimp at 2 ± 1 °C, either whole or decapitated, treated with MAP (40%CO₂/30%O₂/30%N₂) and 100%CO₂ after soaking with compound bactericide were 13 and 17 days, respectively.     

Impact of Bifidobacterium animalis subsp. lactis BB-12 and, Lactobacillus acidophilus LA-5-containing yoghurt, on fecal bacterial counts of healthy adults

This randomized, placebo-controlled, double blind, parallel dose-response study investigated the impact of 4-week commercial yoghurt consumption supplemented with Bifidobacterium animalis subsp. lactis (BB-12) and Lactobacillus acidophilus (LA-5) on fecal bacterial counts of healthy adults. Fifty-eight volunteers were randomly assigned to three different groups: 1. placebo (no probiotic, no starter and no green tea extract); 2. Yoptimal (10⁹ cfu/100 g of BB-12 and LA-5 and 40 mg of green tea extract) and 3. Yoptimal-10 (10¹⁰ cfu/100 g of BB-12, 10⁹ cfu/100 g of LA-5 and 40 mg of green tea extract). These yoghurt products also contained Lactobacillus delbrueckii subsp. bulgaricus (10⁷ cfu/100 g) and Streptococcus thermophilus (10¹⁰ cfu/100 g). The quantitative PCR (qPCR) results showed that there were significant increases (P = 0.02) in bifidobacteria counts with the Yoptimal treatment as compared to baseline. The fecal numbers of B. animalis subsp. lactis and LA-5 significantly increased in the two probiotic treatments compared to the placebo treatment. Viable counts of fecal lactobacilli were significantly higher (P = 0.05) and those of enterococci were significantly lower (P = 0.04) after the intervention when compared to placebo. No significant difference was observed between treatments in volunteers' weight, waist girth, blood pressure, fasting plasma triglyceride and HDL-C concentrations, as well as cholesterol/HDL-cholesterol ratio. However, a significant increase in plasma cholesterol levels was observed in the placebo group (P = 0.0018) but the levels remained stable in the two probiotic yoghurt groups. These results show that probiotic strains supplemented in the form of yoghurt remain active during gut transit and are associated with an increase in beneficial bacteria and a reduction in potentially pathogenic bacteria. This trial was registered at clinicaltrials.gov as NCT00730626.