A new measure of uptake: desorption of unreacted phosphine from susceptible and resistant strains of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Previous studies of phosphine (PH₃) uptake by insects have concentrated on the process as a whole (“gross uptake”), without distinguishing between absorption of the gas and oxidation to non-volatile products. The lower gross uptake by phosphine-resistant (R) strains of stored product pests has given some insights into resistance mechanism(s). In this study, a recently described method of fumigant residue analysis in grains (microwave irradiation followed by headspace gas chromatography) was adapted to measure absorbed unreacted PH₃ (“reversible uptake”) in a susceptible (S) and an R strain of the rust red flour beetle Tribolium castaneum. At a concentration of 0.9 mg l⁻¹, S insects contained 20 ng g⁻¹ after 15 min exposure, rising slowly to 50 ng g⁻¹ after 5 h. The R strain yielded 190 ng g⁻¹ after 15 min, falling to 50 ng g⁻¹ over 5 h. Falling PH₃ content corresponded with increasing mortality in the R strain, while all except the shortest exposure killed 97% or more of the S strain. Insects of either strain, killed prior to PH₃ exposure by freezing in liquid nitrogen, contained 130–140 ng g⁻¹ after 30 min, rising to 190–200 ng g⁻¹ after 5 h. Gross uptake under the same conditions was 50 μg g⁻¹ (S) and 8 μg g⁻¹ (R) after 5 h, which accords with the literature. Reversible uptake by living insects of either strain under anoxia was 40–50 ng g⁻¹ over 30 min to 2 h. By examining the time-course of reversible PH₃ uptake, a new hypothesis of phosphine action and uptake, in which PH₃ oxidation in vivo is a consequence of reactive oxygen species generation, rather than a direct cause of toxicity, is discussed.     

Evaluation of S-residues in grains and grain fractions fumigated with S-labelled carbonyl sulfide

³⁵S-labelled carbonyl sulfide (CO³⁵S) was used to measure the amount of sorbed ³⁵S residues and converted ³⁵S residues in grains and grain fractions after fumigation with CO³⁵S. Hard wheat, soft wheat, paddy rice, brown rice, polished rice, sorghum, maize, canola, barley, oats and peas were exposed for 4 days to 50 mg L⁻¹ of CO³⁵S with a total radioactivity of 20 mCi. After exposure, the samples were aired. The levels of ³⁵S residues varied with extraction solvent, e.g. 0.003–0.02 mg (COS equivalents) kg⁻¹ (grain) in chloroform extractions and 0.09–0.38 mg kg⁻¹ in water extractions. More than 90% of ³⁵S (COS equivalents) residues were in the water extractions. The total radioactivity determined by scanning radiation images (fluorescent image) of extractions and sectioned commodities ranged from 0.1 to 0.4 mg kg⁻¹. The radiation image shows that more than 90% of ³⁵S residues were located or distributed in the embryo, testa, pericarp and husk, and that the ³⁵S was still slowly desorbing from grains after 2 days aeration.     

Influence of feed properties on membrane fouling in crossflow microfiltration of particulate suspensions

The effects of the feed concentration (C_feed) and particle size distribution (PSD) on the crossflow microfiltration (CFMF) of suspensions containing lactalbumin particles were investigated. Experiments were carried out in constant transmembrane pressure (TMP) mode using tubular ceramic membrane modules. All the important parameters: permeate flux, internal and surface fouling, cake mass, height, porosity, and PSD were estimated. The steady-state flux (J_ss) decreased, and internal as well surface fouling and cake mass and height all increased with an increase in C_feed from 0.65 to 2.5 gL⁻¹. This was due to the availability of more particles to foul the membrane at higher C_feed. However, above 2.5 gL⁻¹ there was no significant effect of C_feed on any of these parameters. The overall observed behaviour is attributed to steady-state membrane fouling resulting from the availability of sufficient particles for maximum possible deposition under the experimental conditions reached at 2.5 gL⁻¹. The larger the feed particles, the higher was the J_ss. However, the cake mass, height and porosity were not affected by the feed PSD. Significantly, addition of larger feed particles at the steady state increased the flux by about 6%. This behaviour is attributed to the scouring effect of the large particles on the cake surface. There is scope for looking at the possibility of using the scouring effect of large particles to improve the CFMF process performance.     

Effect of nitric oxide on ethylene production in strawberry fruit during storage

Strawberry is a non-climacteric fruit, with low ethylene production rate after harvest. Its response to nitric oxide (NO), which can be released from sodium nitroprusside (SNP), was studied. We have examined the effect of 1.0, 5.0 and 10.0 μmol l⁻¹ SNP aqueous solution on ethylene production, respiration rate, 1-aminocyclopropane-1-carboxylic acid (ACC) content and the activities of ACC synthase and ACC oxidase in post-harvest strawberry (“Fengxiang”). The most remarkable effect was obtained with 5 μmol l⁻¹ SNP aqueous solution, which significantly inhibited ethylene production, respiration rate, the activity of ACC synthase and reduced the content of ACC, but did not significantly affect the activity of ACC oxidase. SNP at 10 μmol l⁻¹ harmed the fruits; 1 μmol l⁻¹ SNP was too low to significantly extend strawberry storage life. It was suggested that NO could decrease ethylene output, through inhibiting ACC synthase activity reducing ACC content.     

Effect of β-cyclodextrin on antioxidant activity of coumaric acids

Inclusion complexes of o-, m- and p-coumaric acid (CA) with β-cyclodextrin (βCD) were prepared in stoichiometric ratios (1:1) and stability constants and antioxidant activity of the complexes were studied. The apparent stability constants in aqueous solution of 0.39 × 10³ M⁻¹, 2.81 × 10³ M⁻¹ and 49 × 10³ M⁻¹ for o-, m- and p-CA complexes, respectively, were determined by phase solubility tests. Different analytical techniques (IR, MS) in combination with different solvent washing procedures, were used for confirmation of the nature of the inclusion complexes. Dioxan was a suitable solvent for removal of only free CA and CA adsorbed on the surface of the βCD, while methanol removed absorbed, included and free CA from the complexes. In the case of o- and m-CA–βCD complexes, antioxidant activity was significantly increased while, in p-CA–βCD, it remained unchanged. The impact of complex structure on antioxidant activity of CA isomers was clarified.     

Metals and organochlorine compounds in eel (Anguilla anguilla) from the Lesina lagoon, Adriatic Sea (Italy)

The muscle tissue of eels was analysed for metals (Hg, Cd, Cu and Zn), polychlorinated biphenyls (PCBs) and organochlorine pesticides (DDTs) to ascertain whether the concentrations exceeded the maximum levels fixed by the European Commission. Zinc showed the highest concentrations (mean: 20.2 μg g⁻¹ wet wt), followed by copper (mean: 0.58 μg g⁻¹ wet wt), mercury (mean: 0.18 μg g⁻¹ wet wt) and cadmium (mean: 0.03 μg g⁻¹ wet wt). None of the fish samples analysed presented metal concentrations exceeding the proposed limits. Among the organochlorine pesticides, only p,p′-DDE and p,p′-DDT were found with mean values of 19.2 and 3.0 ng g⁻¹ wet wt, respectively, while mean concentrations of PCBs were 94.0 ng g⁻¹ wet wt. With regard to DDT and its metabolites the concentrations were well below the maximum residue limit (MRL), while the mean PCB concentrations, calculated as the sum of the seven “target” congeners indicated by the European Union, exceeded the established limit. From an ecotoxicological point of view, the concentrations of metals and organochlorine compounds reflect a comparatively clean and pollution-free environment. These concentrations may be, thus, considered as useful background levels to which to refer for comparison within the Adriatic Sea.     

Use of isotope analysis to characterize meat fromIberian-breed swine

We describe a method based on isotope analysis (δ¹³C) for characterization and differentiation of Iberian pork meat as a function of the diet of the animal. Using adipose tissue, it is possible to classify unknown samples in group of animals designated “acorn-fed”, “recebo=mixed-fed” and “feed raised” according the δ¹³C value obtained, from the calibration straight line of y=−22.12–0.35x, with a correlation coefficient r=0.982 and s=0.1‰; where y=δ¹³C and x=arrobas of acorn and range forage received by the animals during the fattening period. Stress should be placed on the economic and industrial importance of Iberian-breed swine because the market prices of Iberian swine products depends on the classification of the animals according to the type of feeding regimen which they are subjected to.     

Quantification of Plesiomonas shigelloides in Pure Culture and Clams by Competitive PCR

A quantitative assay for Plesiomonas shigelloides in pure culture and clams based on the competitive polymerase chain reaction was developed. This is the first report for quantitative detection of P. shigelloides by competitive PCR. Forward (PS-F), reverse (PS23RV3), and hybrid primers were designed, and the specificity of the forward and reverse primer for P. shigelloides was proven. An internal standard DNA sequence was synthesized by PCR, with the hybrid primer as the forward primers and PS23RV3 as the reverse primer. A single concentration (0.588 pg/PCR) of internal standard (IS) was used for competitive PCR. The lowest level of detection of P. shigelloides was 80 CFU per PCR in pure culture, 240 CFU/g of clam tissue without enrichment, and 40 CFU/g of clam tissue after 7 hrs. nonselective enrichment at 37°C. There was a linear relationship between the log of the ratio of the relative fluorescent intensities of amplified target DNA bands to the internal standard DNA bands (IS) and the log of the CFU within a certain range in pure cultures and in clam tissue either with or without enrichment. The linear range with cells from a pure culture was the DNA derived from 8.0 × 10¹ to 8.0 × 10⁴ CFU per PCR while with clam tissue, the linear range was the DNA derived from 2.4 × 10² to 2.4 × 10⁵ CFU/g of tissue (1.2 × 10¹ to 1.2 × 10⁴ CFU per PCR) without enrichment, and 4.0 × 10¹ to 1.2 × 10⁴ CFU/g of clam tissue with enrichment, respectively.     

Innovative Methods for Removal of PCR Inhibitors for Quantitative Detection of Plesiomonas shigelloides in Oysters by Real-Time PCR

A quantitative assay for Plesiomonas shigelloides in pure culture and oysters based on the real-time polymerase chain reaction (Rti-PCR) was developed. The methodology involved the treatment of oyster tissue homogenates with formaldehyde, differential centrifugation, and treatment of samples with activated charcoal coated with Pseudomonas fluorescens. With seeded oyster tissue homogenates, without formaldehyde or coated charcoal treatments, the lowest level of detection for P. shigelloides was 1 × 10⁷ genomic targets per gram of tissue, equivalent to 2.5 × 10⁵ genomic targets per Rti-PCR. The addition of 4% formaldehyde to tissue homogenates reduced the minimum level of detection of P. shigelloides to 1 × 10⁵ genomic targets per gram of tissue, equivalent to 2.5 × 10³ genomic targets per real-time PCR. The treatment of tissue homogenates with only activated charcoal coated with P. fluorescens reduced the minimum level of detection of P. shigelloides to 1 × 10⁴ genomic targets per gram, equivalent to 2.5 × 10² genomic targets per real-time PCR, without DNA purification or enrichment. The combination of adding 4.0% formaldehyde to oyster tissue homogenates and treating with coated charcoal reduced the level of detection of P. shigelloides to 1 × 10³ genomic targets per gram, equivalent to 25 genomic targets per real-time PCR. The linear range of detection was from 1 × 10³ to 1 × 10⁶ genomic targets per gram without enrichment.     

Sorption of chloroanisole vapors by raisin packaging material

The behavior and concentration of 2,4,6-trichloroanisole (TCA) vapors migrating into low-density polyethylene film (PE) of 0.39 μm at various temperatures and desorption of TCA from PE were determined. After 12 h exposure, 1642 μg g⁻¹ TCA was sorbed at 30 °C compared with 675 μg g⁻¹ at 20 °C. For PE to reach equilibrium of 4200 μg g⁻¹ at 30 °C took 48 h, but 120 h at 20 °C. The transmission of TCA through PE occurred after 12 h at 30 °C (8.9 μg kg⁻¹ m⁻² h⁻¹) and after 36 h at 20 °C (5.0 μg kg⁻¹ m⁻² h⁻¹). Desorption of TCA from PE increased with temperature. At 80 °C, 99% TCA was desorbed in 1 h compared to 51% at 40 °C, 31% at 30 °C and 17% at 20 °C. The rate of sorption, desorption and transmission of TCA vapors by PE is highly temperature-dependent.     

REVERSE OSMOSIS OF COTTAGE CHEESE WHEY. 1. Influence of Composition of the Feed

SUMMARY– Permeation rate, retention, and solute flux during reverse osmosis of whey and whey fractions were compared using two types of cellulose acetate membranes. When the feed solutions contained no molecules larger than lactose, concentration polarization had little influence on performance except at the highest available driving force (applied pressure minus difference between osmotic pressures of the feed and permeate = 37.8 atm). With the more complex feeds (whey and deproteinized whey), both concentration polarization and fouling of the membrane occurred. Concentration polarization decreased both permeation rate and retention. Fouling decreased permeation rate, but its influence on retention was variable and depended principally on the feed, the solute, and the available driving force. Proteins and other macromolecules in whey had a greater influence on performance during reverse osmosis than smaller solute molecules. With whey as feed, maximum permeation rates were achieved at low available driving forces (10-12 atm), and were similar for the two types of membranes (about 1 ml/cm²*sec). Increasing the available driving force increased retention and therefore reduced solute flux. Choice between the two membranes requires a compromise between extent of desalting and loss of lactose in the permeate.     

Inactivation of Enterobacter sakazakii by pulsed electric field in buffered peptone water and infant formula milk

The effect of high-intensity pulsed electric field (PEF) treatment on the survival of Enterobacter sakazakii suspended in buffered peptone water (BPW) and powdered infant formula milk (IFM) was evaluated. Reference medium and IFM samples were treated with PEF. Electric field intensity and treatment time were varied from 10 to 40 kV cm⁻¹ and from 60 to 3895 μs, respectively. Samples of buffered peptone water (3 g L⁻¹) and IFM were inoculated with E. sakazakii (CECT 858) (10⁹ cfu mL⁻¹) and then treated with PEF. The inactivation data were adjusted to the Weibull frequency distribution function and Bigelow model, and constants were calculated for both substrates. A maximum 2.7 log (cfu mL⁻¹) reduction was achieved in BPW after exposure of E. sakazakii to PEF for 360 μs (2.5 μs pulse width) at 40 kV cm⁻¹. In IFM, exposure of E. sakazakii to PEF, with the same conditions, led to a 1.2 log (cfu mL⁻¹) reduction. The greater the field strength and treatment time, the greater the inactivation achieved in both substrates. Even though further research will be necessary, according to the results, there are good prospects for the use of PEF in hospitals to achieve safe reconstituted infant formula before storage at refrigerated temperatures.     

Antioxidant activity of Caryocar brasiliense (pequi) and characterization of components by electrospray ionization mass spectrometry

The Caryocar brasiliense known commonly as pequi is a tropical fruit of Brazilian Cerrado and is considered an important option of income and food for the populations living in this biome. Our previous study indicated that C. brasiliense had high total phenol content (209 g as gallic acid equivalent kg⁻¹) and excellent scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical (IC₅₀ of 9.44 μg ml⁻¹). In this study, we evaluated the highly efficient antioxidant activity of C. brasiliense using the biological relevant method of chemically induced lipid peroxidation. The half inhibition concentration did not exceed 0.8 μg ml⁻¹. In addition, polar components of pequi ethanolic extract were investigated by direct infusion electrospray ionization mass spectrometry (ESI-MS). The technique revealed the presence of important bioactive components widely reported as potent antioxidants such as gallic acid, quinic acid, quercetin, and quercetin 3-O-arabinose possibly explaining its higher antioxidant activity. This is the first report on the composition by ESI-MS of pequi extract demonstrating excellent antioxidant activity.     

Levels of heavy metals in candy packages and candies likely to be consumed by small children

Ninety two samples of child-consumed candies and candy packages were analyzed for seven heavy metals. Lead (Pb) was detected at concentrations of 110.3–6394.1 mg kg⁻¹ in ten of 92 candy packages. The directive factor of Pb contamination had originated in the lead-based ink of the outer cover. Particularly, Pb was detected at high concentrations in case of green- or yellow-colored packages. Chromium (Cr) was detected at high concentrations in cases where Pb was also detected at high concentrations, and the Cr levels ranged from 136.9 mg kg⁻¹ to 1429.3 mg kg⁻¹ in seven of the 92 candy packages. Hexavalent chromium [Cr(VI)] was detected at 87–105.0% of the total Cr in polypropylene-coated wrappers with printed outer covers. The migration of Cr(VI) increased with elution time up to 0.20 μg (cm²)⁻¹ for 30 days in basic (pH 10.0) solution; however, there were no migrations in acidic (pH 4.0) and neutral (pH 7.0) solutions. The migration of Pb increased with elution time up to 0.65 μg (cm²)⁻¹ and 0.28 μg (cm²)⁻¹ in basic (pH 10.0) and acidic (pH 4.0) solutions, respectively. However, any migration was hardly observed in neutral (pH 7.0) solution.     

The effect of air temperature, velocity and visual lean (VL) composition on the tempering times of frozen boneless beef blocks

Beef blocks of two compositions, 100% and 50% visual lean (VL), in standard commercial packaging with nominal dimensions of 510 × 390 × 150 mm were tempered from −18 °C to −3 °C using air at temperatures from 3 °C to −3 °C and velocities of 0.5 and 5 ms⁻¹. These conditions were then modelled using a finite difference mathematical model and the accuracy of the model assessed by comparison with the experimental results. An extended range of conditions (including an intermediate air velocity of 2 ms⁻¹ and an intermediate composition of 75% VL) was then modelled to produce data that can be used to design tempering processes.

The results show that single stage air tempering of even single blocks within their cartons needs to be a long process. In air at 3 °C and 5 ms⁻¹, blocks of 50% VL rose to deep temperatures of −10 °C and −3 °C after 4.0 and 22.5 h, respectively, while with 100% VL 4.6 and 27.3 h were required. Under these conditions, the surface layers of the meat would have spent many hours in a thawed condition that would be detrimental to both drip and optimal processing. Using lower temperatures avoids thawing and at the same time produces an optimum temperature difference for subsequent processing. However, tempering times are substantially extended. For example, times to the above temperatures using air at −1 °C and 5 ms⁻¹ were 4.8 and 37.5 h for 50% VL and 5.1 and 44.5 h for 100% VL.     

Growth and toxigenesis of C. botulinum type E in fishes packaged under modified atmospheres

Modified atmosphere packaging of fresh fish is used to market high quality products in some European countries. The potential risk of C. botulinum growth in these extended shelf-life foods is still a concern; especially since toxigenesis may precede organoleptic spoilage. This paper will present toxigenic data from rockfish, salmon and sole muscle tissues which were inoculated with a pool of non-proteolytic C. botulinum type E at seven levels (10⁻² −10⁴ spores/sample), and stored under vacuum and 100% CO₂, at incubation temperatures between 30 and 4°C, for up to 60 days. Factorial experimental design allowed predictive formulae to be developed able to describe the lag time prior to C. botulinum toxigenesis and the probability of one spore to initiate toxigenesis based upon the storage conditions. Accurate characterization of the microbial ecology of C. botulinum in modified atmosphere-packaged fish, will support safe exploitation of these packaging systems in the market place, and identify critical control points for potential product or process abuses.     

Thermal inactivation of lectins (PHA) isolated from Phaseolus vulgaris

The influence of the thermal process on the loss of ability to bind a carbohydrate target was studied on lectins (PHA) purified from Phaseolus vulgaris seeds. Thermal inactivation of aqueous solutions of pure PHA occurred according to a biphasic first-order mechanism, the thermodynamic parameters, at pH 7·3, being as follows: ΔH*₁ = ΔH*₂ = 86·2 kcal mole⁻¹, ΔS*₁ = − 54·04 cal deg⁻¹ and ΔS*₂ = − 56·71 cal deg⁻¹. The first-order rate constants appeared to be dependent on pH (minimal around 7) and divalent cations. All different subunits constituting the whole PHA were inactivated at the same rate. The biphasic nature of this process is independent of the presence of 10 m Ca⁺⁺ or Mg⁺⁺ and appeared to indicate a discrete aggregation of PHA molecules.     

Diffusion of thiocyanate and hypothiocyanite in whey protein films incorporating the lactoperoxidase system

The diffusion of the thiocyanate (SCN⁻) and hypothiocyanite (OSCN⁻) components of a lactoperoxidase system (LPOS) in whey protein isolate (WPI) films was investigated. Diffusion coefficients for these molecules were measured for the LPOS-incorporated WPI films prepared with different WPI:glycerol ratios (1:1, 3:1, and 5:1). WPI film disks were coated on the surfaces of smoked salmon samples, and the samples were stored at 4, 10 and 22 °C. The diffusion coefficients were determined by fitting a mathematical model to the amounts of SCN⁻ and OSCN⁻ released from the disks during a period of time. The diffusion coefficients for SCN⁻ (D₁) and OSCN⁻ (D₂) in the films were 0.19–5.2 × 10⁻¹² m² s⁻¹ and 0.13–6.5 × 10⁻¹³ m² s⁻¹, respectively. The D₁ and D₂ decreased as the WPI:glycerol ratio increased and the storage temperature decreased. The E_a values for diffusion in 1:1, 3:1, and 5:1 WPI:glycerol films were 13.3, 29.5, and 35.6 kJmol⁻¹, respectively, for SCN⁻ and 15.8, 30.1, and 39.9 kJmol⁻¹, respectively, for OSCN⁻.     

The fracture toughness of pea testa in relation to temperature abuse during frozen storage

Obtaining information on the textural quality of food materials in SI units is desirable for objective quality control. Adapting standard materials testing methods to biological specimens has the potential of providing such objective measurements. Based on the approach of linear elastic fracture mechanics, a tear test was used to measure the fracture toughness of the testa of frozen peas. The mean fracture toughness obtained for an extension rate of 0.13 mm s⁻¹ was 212 J m⁻². The effect of extension rate was investigated and showed that fracture toughness increased with increasing extension rate. Measurement of fracture toughness was applied to identify the effect of “temperature abuse” in the pea testa. Following three thaw-freeze cycles, the specimen became more fragile and fracture toughness of pea testa decreased by about 18%. Brightfield microscopy and low temperature scanning electron microscopy were used to observe tissue changes resulting from temperature abuse. Cell rupture in the osteosclereids and parenchyma layers was associated with temperature-abused tissue. Slow freezing during the thaw-freeze cycles caused formation of large ice crystals which disrupted the pea testa tissue.     

Chemical attributes characterizing sticky post-mortem ageing in beef

Reports in literature on post-mortem sticky ageing are rare and data about chemical metabolites that occur particularly during sticky ageing are partly contradictory. In the present study different chemicals (pH, NH₃, TVB-N, H₂S, R value, IMP, pyruvate and various volatile acids such as lactic acid, acetic acid, butyric acid, uric acid and pyroglutamic acid) were tested for their suitability to serve as parameters to characterize sticky post-mortem ageing in beef muscle samples. Results show that a high butyric acid concentration (0.46 μMol g⁻¹) seems to be typical for sticky post-mortem ageing in beef. A distinction from onset of spoilage is possible due to the high butyric acid concentration, a low ammonia content (10.5 mg 100 g⁻¹) and a low pH value. From meat with normal ageing it can be differentiated by sensory, colour, smell, consistency, a high butyric and pyroglutamic acid content and a low IMP concentration (0.04 μMol g⁻¹).