Migration measurement and modelling from poly(ethylene terephthalate) (PET) into soft drinks and fruit juices in comparison with food simulants

Poly(ethylene terephthalate) (PET) bottles are widely used for beverages. Knowledge about the migration of organic compounds from the PET bottle wall into contact media is of interest especially when post-consumer recyclates are introduced into new PET bottles. Using migration theory, the migration of a compound can be calculated if the concentration in the bottle wall is known. On the other hand, for any given specific migration limit or maximum target concentration for organic chemical compounds in the bottled foodstuffs, the maximum allowable concentrations in the polymer CP,0 can be calculated. Since a food simulant cannot exactly simulate the real migration into the foodstuff or beverages, a worse-case simulation behaviour is the intention. However, if the migration calculation should not be too overestimative, the polymer-specific kinetic parameter for migration modelling, the so-called AP value, should be established appropriately. One objective of the study was the kinetic determination of the specific migration behaviour of low molecular weight compounds such as solvents with relatively high diffusion rates and, therefore, with high migration potential from the PET bottle wall into food simulants in comparison with real beverages. For this purpose, model contaminants were introduced into the bottle wall during pre-form production. The volatile compounds toluene and chlorobenzene were established at concentrations from about 20-30 mg kg(-1) to 300-350 mg kg(-1). Phenyl cyclohexane was present at concentrations of 35, 262 and 782 mg kg(-1), respectively. The low volatile compounds benzophenone and methyl stearate have bottle wall concentrations of about 100 mg kg(-1) in the low spiking level up to about 1000 mg kg(-1) in the highly spiked test bottle. From these experimental data, the polymer specific parameters (AP values) from mathematical migration modelling were derived. The experimental determined diffusing coefficients were determined, calculated and compared with literature data and an AP' value of 1.0 was derived thereof for non-swelling food simulants like 3% acetic acid, 10% ethanol or iso-octane. For more swelling condition, e.g. 95% ethanol as food simulant, an AP' value of 3.1 seems to be suitable for migration calculation. In relation to PET recycling safety aspects, maximum concentrations in the bottle wall were established for migrants/contaminants with different molecular weights, which correspond with a migration limit of 10 microg kg(-1). From the experimental data obtained using food simulants and in comparison with beverages, the most appropriate food simulant for PET packed foods with a sufficient but not too overestimative worse-case character was found to be 50% ethanol. In addition, it can be shown that mass transport from PET is generally controlled by the very low diffusion in the polymer and, as a consequence, partitioning coefficients (KP/F values) of migrants between the polymer material and the foodstuff do not influence the migration levels significantly. An important consequence is that migration levels from PET food-contact materials are largely independent from the nature of the packed food, which on the other hand simplifies exposure estimations from PET.     

Migration measurement and modelling from poly(ethylene terephthalate) (PET) into soft drinks and fruit juices in comparison with food simulants

Poly(ethylene terephthalate) (PET) bottles are widely used for beverages. Knowledge about the migration of organic compounds from the PET bottle wall into contact media is of interest especially when post-consumer recyclates are introduced into new PET bottles. Using migration theory, the migration of a compound can be calculated if the concentration in the bottle wall is known. On the other hand, for any given specific migration limit or maximum target concentration for organic chemical compounds in the bottled foodstuffs, the maximum allowable concentrations in the polymer C _P,0 can be calculated. Since a food simulant cannot exactly simulate the real migration into the foodstuff or beverages, a worse-case simulation behaviour is the intention. However, if the migration calculation should not be too overestimative, the polymer-specific kinetic parameter for migration modelling, the so-called A _P value, should be established appropriately. One objective of the study was the kinetic determination of the specific migration behaviour of low molecular weight compounds such as solvents with relatively high diffusion rates and, therefore, with high migration potential from the PET bottle wall into food simulants in comparison with real beverages. For this purpose, model contaminants were introduced into the bottle wall during pre-form production. The volatile compounds toluene and chlorobenzene were established at concentrations from about 20–30 mg kg^?1 to 300–350 mg kg^?1. Phenyl cyclohexane was present at concentrations of 35, 262 and 782 mg kg^?1, respectively. The low volatile compounds benzophenone and methyl stearate have bottle wall concentrations of about 100 mg kg^?1 in the low spiking level up to about 1000 mg kg^?1 in the highly spiked test bottle. From these experimental data, the polymer specific parameters (A _P values) from mathematical migration modelling were derived. The experimental determined diffusing coefficients were determined, calculated and compared with literature data and an A _P′ value of 1.0 was derived thereof for non-swelling food simulants like 3% acetic acid, 10% ethanol or iso-octane. For more swelling condition, e.g. 95% ethanol as food simulant, an A _P′ value of 3.1 seems to be suitable for migration calculation. In relation to PET recycling safety aspects, maximum concentrations in the bottle wall were established for migrants/contaminants with different molecular weights, which correspond with a migration limit of 10 μg kg^?1. From the experimental data obtained using food simulants and in comparison with beverages, the most appropriate food simulant for PET packed foods with a sufficient but not too overestimative worse-case character was found to be 50% ethanol. In addition, it can be shown that mass transport from PET is generally controlled by the very low diffusion in the polymer and, as a consequence, partitioning coefficients (K _P/F values) of migrants between the polymer material and the foodstuff do not influence the migration levels significantly. An important consequence is that migration levels from PET food-contact materials are largely independent from the nature of the packed food, which on the other hand simplifies exposure estimations from PET.     

Ascorbate oxidase from starfruit (Averrhoa carambola): preparation and its application in the determination of ascorbic acid from fruit juices

A study was conducted to utilize ascorbate oxidase (AAO) from very immature starfruit for the enzymatic determination of ascorbic acid (AsA) in colored samples. The enzyme preparation was carried out by a combination of (NH₄)₂SO₄ fractionation, DEAE-Toyopearl 650 M and ultrafiltration. A calibration curve for AsA was constructed by plotting the amount of AsA oxidized by the enzyme at a specified reaction time against the absorbance. The curve showed a linear relationship in the range of 0–100 μg ml⁻¹ AsA used. Using the plot, the values of AsA in juice samples were determined and compared with the conventional 2,6-dichloroindophenol method.     

Pregnancy-induced changes in substance P and neurokinin 1 receptor (NK1-R) expression in the rat uterus

Adrenergic nerve fibres of the mammalian uterus degenerate during pregnancy. The behaviour of peptidergic fibres, such as substance P-positive fibres and of its preferred neurokinin 1 receptor (NK1-R), is poorly studied in the pregnant rat uterus. The present study analysed the changes in substance P immunoreactivity and in the expression of NK1-R protein in the uterus of non-pregnant, pregnant (days 7, 14 and 21) and postpartum rats (days 1, 8 and 22) by immunohistology, dot blot analysis and western blot analysis. In non-pregnant rats, substance P-positive fibres were localized to the myometrium; these fibres progressively disappeared during gestation and were almost absent at term (day 21). At day 22 post partum, substance P-positive fibres had recovered to numbers comparable with those in the non-pregnant uterus. Dot blot analysis revealed a significant decrease in the immunoreactivity of substance P in the uterus at mid-pregnancy (day 14) and especially at term. Expression of the NK1-R protein showed a progressive increase throughout pregnancy reaching a peak on day 1 post partum; downregulation of NK1-R protein occurred on day 8 post partum. The low and high expressions of NK1-R protein were coincident with a large number of eosinophils and almost no eosinophils in the uterus at oestrus and at term, respectively. It was concluded that substance P immunoreactivity is inversely correlated with NK1-R protein expression in the pregnant and postpartum uterus. The marked upregulation of NK1-R protein at term and after birth indicates that the NK1-R may be involved in the complex regulation of labour and postpartum physiology. However, it is likely that the NK1-protein is not involved in the recruitment of eosinophils into the uterus at oestrus.     

Antimicrobial efficacy of UV radiation on Escherichia coli O157:H7 (EDL 933) in fruit juices of different absorptivities

The efficacy of UV light for inactivating E. coli (ATCC 25922) and E. coli O157:H7 (EDL 933) was examined in fruit juices (orange, apple, and multifruit) with different absorptivities under several operating conditions (liquid film thickness and agitation rate). The juices were inoculated with two bacterial concentrations (10(5) and 10(7) CFU/ml) and were treated using a UV desinfection unit at 254 nm; UV doses ranged from 0 to 6 J/cm2. The effect of the culture medium, tryptone soy agar (TSA) and sorbitol MacConkey agar (SMAC), on the recovery of E. coli strains exposed to UV radiation was also analyzed. The most suitable culture medium for recovery of E. coli strains in juices exposed to UV radiation was TSA. Values of D (radiation dose [joules per square centimeter] necessary to decrease the microbial population by 90%) obtained in all juices assessed were higher in TSA than in SMAC. In the juices analyzed, stirring of the medium exposed to UV radiation and reducing liquid film thickness (to 0.7 mm) produced the highest bactericidal effect. A linear relationship was found between the D-values obtained and the absorptivity coefficients for all the juices. The higher the absorbance of the medium, the greater the values of D required to inactivate E. coli strains by UV radiation. An equation was developed to describe the relationship of the fraction of energy absorbed by the system (absorbed energy factor [AEF]), the thickness of the film exposed to UV radiation, and the absorptivity coefficient of the juices. A linear relationship was found between D and AEF in the different juices tested.     

Variability of the plasma proteome in healthy people (report 1)

The last decade has seen intense development of proteomic technologies have opened new perspectives for rapid large-scale screening of biological samples in order to find biomarkers of various diseases or conditions. However, in order to adequately evaluate the possibility of using protein as a biomarker, it is necessary to know how much its concentration varies widely in healthy people. This project aims to explore the limits of the concentration of protein components of plasma in healthy people.     

A new selective liquid membrane extraction method for the determination of basic herbicides in agro-processed fruit juices and Ethiopian honey wine (Tej) samples

Supported liquid membrane (SLM) extraction was optimised for trace extraction and enrichment of selected triazine herbicides from a variety of agro-processed fruit juices and Ethiopian honey wine (Tej) samples. In the extraction process, a 1:1 mixture of n-undecane and di-n-hexylether was immobilised in a thin porous PTFE membrane that forms a barrier between two aqueous phases (the donor and acceptor phases) in a flow system. The extracts constitute the selectively enriched analytes collected from the acceptor phase and were analysed by transferring to a HPLC-UV system using a diode array detector at 235?nm. High enrichment factors were obtained with very good repeatability of results, and the detection limit was lower than 3.00?μg l?1 for ametryn in apple juice. The optimised method showed very good linearity of over 50-500?μg l?1 with a correlation coefficient of >0.990 or better for triplicate analysis. All chromatograms gave well resolved peaks with no interfering peaks at the retention times of the selected triazines, showing high selectivity of the SLM extraction method in combination with HPLC-UV for the selected matrices. The optimised method can be used as an alternative solventless extraction method for microgram-level extraction of other triazine herbicides and a variety of pesticides from liquid and semi-liquid environmental, biological and food matrices.     

A new selective liquid membrane extraction method for the determination of basic herbicides in agro-processed fruit juices and Ethiopian honey wine (Tej) samples

Supported liquid membrane (SLM) extraction was optimised for trace extraction and enrichment of selected triazine herbicides from a variety of agro-processed fruit juices and Ethiopian honey wine (Tej) samples. In the extraction process, a 1:1 mixture of n-undecane and di-n-hexylether was immobilised in a thin porous PTFE membrane that forms a barrier between two aqueous phases (the donor and acceptor phases) in a flow system. The extracts constitute the selectively enriched analytes collected from the acceptor phase and were analysed by transferring to a HPLC-UV system using a diode array detector at 235?nm. High enrichment factors were obtained with very good repeatability of results, and the detection limit was lower than 3.00?µg l^?1 for ametryn in apple juice. The optimised method showed very good linearity of over 50–500?µg l^?1 with a correlation coefficient of >0.990 or better for triplicate analysis. All chromatograms gave well resolved peaks with no interfering peaks at the retention times of the selected triazines, showing high selectivity of the SLM extraction method in combination with HPLC-UV for the selected matrices. The optimised method can be used as an alternative solventless extraction method for microgram-level extraction of other triazine herbicides and a variety of pesticides from liquid and semi-liquid environmental, biological and food matrices.     

Proteome Comparison of Grains from Two Maize Genotypes,with Colorless Kernel Pericarp (P1-ww) and Red Kernel Pericarp (P1-rr)

Maize genotypes P1-rr (R) and P1-ww (W) have high and low flavonoid content, respectively. Grain proteome profiles of these maize genotypes were compared. Two-dimensional gel electrophoresis (2-DE) was performed from three soluble protein extracts of each maize genotype and 55 proteins spots were differentially expressed using univariate analysis. Differentially expressed protein spots were analyzed by mass spectrometry-peptide mass fingerprint (MS-PMF) and eight of them were identified on the Zea mays L. database. Additionally, grouping of proteomic data was evaluated by principal component analysis (PCA) using 135 matched spots in all six analyzed gels. First component (PC1) represented 46.5% of total variation and second component (PC2) referred to 22.5%. This multivariate analysis showed the separation of the two maize genotypes proteome profiles using 2-DE data. The data presented in this study shows that 2-DE complemented with PCA is applicable to food analysis.     

Effect of glutamine on heat-shock protein beta 1 (HSPB1) expression during myogenic differentiation in bovine embryonic fibroblast cells

Food Science and Biotechnology - The objective of this study was to examine the effects of glutamine on heat-shock protein beta 1 (HSPB1) expression in bovine embryonic fibroblast cells during...     

Purification and characterization of an antioxidant protein (∼16 kDa) from Terminalia chebula fruit

Terminalia chebula fruit is used as folk medicine in India and Southeast Asia. An antioxidant protein was isolated by bioassay guided fractionation of T.chebula fruit by homogenizing in the citrate phosphate buffer. The isolated protein (TCP-III) obtained from fruit was purified by gel chromatography and preparative HPLC, showed apparent molecular weight of 16 kDa by SDS-PAGE and MALDI-TOF/MS analyses. Amino acid sequence obtained by LC-MS^E analysis showed homology with the predicted protein fragments of Populus trichocarpa, putative uncharacterized protein fragments from Oryza sativa and with fragments of 17 kDa thylakoid lumenal protein from Spinacia oleracea. TCP-III exhibited significant radical scavenging in DPPH, NO, H₂O₂ and ABTS assays. In addition, TCP-III inhibited oxidation of linoleic acid in β-carotene bleaching assay, reduced ferric ions and chelated ferrous ions. The present finding demonstrates uniquely, for the first time, characterization of an antioxidant protein from T. chebula fruit.     

Purification and characterisation of β‐mannanase from Lactobacillus plantarum (M24) and its applications in some fruit juices

β‐Mannanase was purified 2619.05‐fold from the Lactobacillus plantarum (M24) bacterium by ammonium sulphate precipitation and ion exchange chromatography (DEAE‐Sephadex). The purified enzyme gave two protein bands at a level of approximately 36.4 and 55.3 kDa in the SDS‐PAGE. The purified mannanase enzyme has shown its maximum activity at 50 °C and pH 8, and it has been also determined that the enzyme was stable at 5–11 pH range and over 50 °C. The V_max and K_m values have been identified as 82 mg mannan mL^?1 and 0.178 mm , respectively. The effects of some metal ions such as Fe²⁺, Ca²⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺ and Zn²⁺ on the mannanase enzyme have been also investigated, and it has been determined that all metal ions had significant effects on the activation of the mannanase enzyme. In addition, the effectiveness of the purified mannanase enzyme on the clarification of some fruit juices such as orange, apricot, grape and apple has been investigated. During the clarification processes, the enzyme was more effective than crude extracts on the clarification of the peach juice with a ratio of 223.1% at most.     

Modeling the diffusion-adsorption kinetics of 1-methylcyclopropene (1-MCP) in apple fruit and non-target materials in storage rooms

The purpose of this research was to model the kinetics of adsorption of 1-methylcyclopropene (1-MCP) in apple fruit and non-target solid materials found in apple storage rooms. The process was described by Fick’s second law of diffusion of the gas through the pores of the material coupled with adsorption kinetics of the gas on the material’s binding sites. A finite element formulation of the model, describing the diffusion and adsorption mechanisms separately, was first developed. The values of the relevant parameters were estimated based on headspace measurements of the decrease of 1-MCP in jars containing the different materials. The headspace concentration of 1-MCP was measured using gas chromatography. Apple fruit (Golden Delicious and Jonagold) and the following bin construction materials were investigated: high density polyethylene (HDPE), oak, poplar wood and card lining. The range in the magnitude of the diffusion coefficient, adsorption coefficient, and concentration of active sites in the various solids was 10,000-, 8-, and 30-fold, respectively.     

Effect of Ethrel and 1-methylcyclopropene (1-MCP) on antioxidants in mango (Mangifera indica var. Dashehari) during fruit ripening

Ripening affects the quality and nutritional contents of fleshy fruits. Mango, a climacteric fruit, is very susceptible to post-harvest losses, due to fast softening. In the present paper we report the effect of 1-methylcyclopropene (1-MCP) and Ethrel on antioxidant levels in mango fruit during ripening. Use of 1-MCP is applied commercially to delay ripening while Ethrel is used to accelerate ripening of climacteric fruits. 1-MCP treatment led to decreased levels of H₂O₂ and lipid peroxidation, concomitant with increased activities and isozymes of catalase (CAT) and superoxide dismutase (SOD), as compared to respective controls. On the other hand, Ethrel treatment led to an increase in H₂O₂ and lipid peroxidation, concomitant with a decrease in the activities and isozymes of catalase and SOD. Guaiacol peroxidase (GPX) could not be detected in the control or in treated fruits. Activity of ascorbate peroxidase (APX) was found to drastically increase in the presence of Ethrel while 1-MCP treatment led to only a marginal increase in APX.     

The aliphatic isothiocyanates erucin and sulforaphane do not effectively up‐regulate NAD(P)H:quinone oxidoreductase (NQO1) in human liver compared with rat

Isothiocyanate up‐regulation of hepatic NAD(P)H:quinone oxidoreductase (NQO1) and glutathione S‐transferases (GSTs) is an integral mechanism of their chemoprevention. In this paper, for the first time, the potential of the isothiocyanates erucin and sulforaphane to modulate these enzymes was investigated in two human livers and compared to rat liver. Precision‐cut liver slices were incubated with erucin or sulforaphane (1–50 μM). Both isothiocyanates elevated NQO1 activity in rat slices that was paralleled by a fourfold rise in protein levels. No change in activity was noted in human slices, and only a weak rise in protein levels, < 10% of that in rat, was observed in only one of the human livers, whereas the other was refractive. GST activity, assessed with three substrates, was elevated in rat slices treated with either isothiocyanate, and was accompanied by a rise in GSTα and GSTμ, but not GSTπ, protein levels. A rise in activity and in GSTα and GSTμ protein levels was also noted in one of the human livers. It appears that erucin and sulforaphane elevate GST expression in isoform‐specific manner in both rat and human liver, whereas NQO1 is inducible by these compounds only in rat liver and very poorly in human liver.     

Purification and characterization of an alkaline pectin lyase produced by a newly isolated Brevibacillus borstelensis (P35) and its applications in fruit juice and oil extraction

An alkaline pectin lyase (PNL) (EC 4.2.2.10) secreted by Brevibacillus borstelensis P35 (GenBank Number: FJ417406) was purified using ammonium sulfate fractionation, anion exchange chromatography on DEAE-cellulose and gel filtration chromatography on Sephadex G-150. The pH and temperature optima of the enzyme were found to be 8.0 and 60 °C. The enzyme does not loose activity up to 60 °C if exposed for 1 h. The values of K _m and V _max of the enzyme were 0.625 mg/mL and 126.32 s^?1, respectively. The molecular weight was found to be 36 ± 01 kDa. The presence of 10 mM concentration of Ca²⁺, Cu²⁺, Mn²⁺, Mg²⁺, Zn²⁺, Hg²⁺, Fe²⁺ and EDTA, l-cystein, ascorbic acid significantly enhanced the PNL of the purified enzyme. In the course of the laboratory trials, it was demonstrated that PNL from B. borstelensis (P35) could be successfully applied to the production and clarification of fruit juice and oil extraction.