Effect of ionising radiation treatment on the specific migration characteristics of packaging-food simulant combinations: effect of type and dose of radiation

Migration levels of acetyl tributyl citrate (ATBC) plasticiser from polyvinyl chloride (PVC) film into the European Union specified aqueous food simulants (distilled water, 3% w/v acetic acid and 10% v/v ethanol) were monitored as a function of time. Migration testing was carried out at 40°C for 10 days. Determination of the analyte was performed by applying an analytical methodology based on surfactant (Triton X-114) mediated extraction prior to gas chromatographic-flame ionisation detection. PVC cling film used was subjected to ionising treatment with a [(60)Co] source, as well as to electron-beam irradiation at doses equal to 5, 15 and 25 kGy, with the aim to compare the effect of type and dose of radiation on the specific migration behaviour of PVC. Equilibrium concentrations of acetyl tributyl citrate into the aqueous solvents covered the ranges 173-422 μg l(-1) and 296-513 μg l(-1) for gamma- and electron-irradiated PVC, respectively. Hence, e-beam irradiation resulted in significantly higher ATBC migration compared with gamma treatment. The highest extraction efficiency of the 10% ethanol solution was common in both gamma and e-beam treatments; distilled water demonstrated the lowest migration. Gamma-irradiation at intermediate doses up to 5 kGy produced no statistically significant (p > 0.05) effect on ATBC migration into all three aqueous simulants; however, this does not apply for high-energy electrons. Both ionising treatments were similar in that they resulted in statistically significant (p < 0.05) differences in plasticiser migrating amounts between non-irradiated and irradiated at doses of 15 and 25 kGy samples. Gamma-radiation did not affect the kinetics of plasticiser migration. On the contrary, electron-beam radiation produced shorter equilibration times for all food-simulating solvents tested at 40°C. The above values regarding ATBC migration into aqueous food simulants are far below the European Union restriction (1 mg kg(-1) body weight) for both types of ionising radiation. Thus, PVC cling film may be used in food irradiation applications in contact with aqueous foodstuffs.     

Effect of ionising radiation treatment on the specific migration characteristics of packaging–food simulant combinations: effect of type and dose of radiation

Migration levels of acetyl tributyl citrate (ATBC) plasticiser from polyvinyl chloride (PVC) film into the European Union specified aqueous food simulants (distilled water, 3% w/v acetic acid and 10% v/v ethanol) were monitored as a function of time. Migration testing was carried out at 40°C for 10 days. Determination of the analyte was performed by applying an analytical methodology based on surfactant (Triton X-114) mediated extraction prior to gas chromatographic-flame ionisation detection. PVC cling film used was subjected to ionising treatment with a [⁶⁰Co] source, as well as to electron-beam irradiation at doses equal to 5, 15 and 25 kGy, with the aim to compare the effect of type and dose of radiation on the specific migration behaviour of PVC. Equilibrium concentrations of acetyl tributyl citrate into the aqueous solvents covered the ranges 173–422?µg?l^?1 and 296–513?µg?l^?1 for gamma- and electron-irradiated PVC, respectively. Hence, e-beam irradiation resulted in significantly higher ATBC migration compared with gamma treatment. The highest extraction efficiency of the 10% ethanol solution was common in both gamma and e-beam treatments; distilled water demonstrated the lowest migration. Gamma-irradiation at intermediate doses up to 5 kGy produced no statistically significant (p?>?0.05) effect on ATBC migration into all three aqueous simulants; however, this does not apply for high-energy electrons. Both ionising treatments were similar in that they resulted in statistically significant (p?<?0.05) differences in plasticiser migrating amounts between non-irradiated and irradiated at doses of 15 and 25 kGy samples. Gamma-radiation did not affect the kinetics of plasticiser migration. On the contrary, electron-beam radiation produced shorter equilibration times for all food-simulating solvents tested at 40°C. The above values regarding ATBC migration into aqueous food simulants are far below the European Union restriction (1?mg?kg^?1 body weight) for both types of ionising radiation. Thus, PVC cling film may be used in food irradiation applications in contact with aqueous foodstuffs.     

Migration of antimony from PET containers into regulated EU food simulants

Antimony migration from polyethylene terephthalate (PET) containers into aqueous (distilled water, 3% acetic acid, 10% and 20% ethanol) and fatty food simulants (vegetable oil), as well as into vinegar, was studied. Test conditions were according to the recent European Regulation 10/2011 (EU, 2011). Sb migration was assayed by ICP-MS and HG-AFS. The results showed that Sb migration values ranged from 0.5 to 1.2 μg Sb/l, which are far below the maximum permissible migration value for Sb, 40 μg Sb/kg, (EU, Regulation 10/2011). Parameters as temperature and bottle re-use influence were studied. To assess toxicity, antimony speciation was performed by HPLC-ICP-MS and HG-AFS. While Sb(V) was the only species detected in aqueous simulants, an additional species (Sb–acetate complex) was measured in wine vinegar. Unlike most of the studies reported in the literature, migration tests were based on the application of the EU directive, which enables comparison and harmonisation of results.     

Antioxidants and their migration into food simulants on irradiated LLDPE film

Effects of γ-irradiation on residual and migration levels of antioxidants, tris-(2,4-di-tert-butylphenyl) phosphite (Irgafos 168) and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (Irganox 1076), and their radiolysis products were investigated in the linear low density polyethylene (LLDPE) packaging samples treated at doses from 0 to 200 kGy. The content of Irgafos 168 was not detected in 5 kGy treated samples and the content of Irganox 1076 decreased by 34.9% from the initial level in 10 kGy treated samples. The radiolysis products, 2,4-di-tert-butylphenol (2,4-DTBP), 1,3-di-tert-butylbenzene (1,3-DTBB), and toluene were identified and their concentrations gradually increased as the irradiation dose increased. Migration of Irgafos 168 from the LLDPE pouch into food simulants, distilled water, acetic acid (4 ml/100 ml distilled water) or ethanol (20 ml/100 ml distilled water), was not detected at dose levels up to 200 kGy while that of the Irganox 1076 was detected in a decreasing mode with increasing dose.     

Overall migration from commercial coextruded food packaging multilayer films and plastics containers into official EU food simulants

The overall migration from a wide range of commercial five-layer coextruded packaging films into aqueous food simulants (distilled water, 3% aqueous acetic acid) and alternative fatty food simulant (iso-octane) was studied. The overall migration from commercial plastics cups (PS, HIPS, and PP) used for ice-cream or yogurt packaging into distilled water and 3% aqueous acetic acid was also studied. Test conditions for packaging material/food simulant contact and method of overall migration analysis were according to the EU directives and CEN-standards. The results showed that for all tested five-layer films and plastics (PS, HIPS, and PP) cups values of overall migration into aqueous simulants (0.11-0.79 mg/dm², 2.3-15.9 mg/l) and (<0.10-0.41 mg/dm², <0.80-3.1 mg/l) were significantly lower than the upper limit (10 mg/dm²) for overall migration from plastic packaging materials and articles into food and food simulants set by the EU Directive 90/128/EEC and their revisions. The overall migration values from five-layer materials into iso-octane were significantly higher (0.94-8.23 mg/dm², 18.8-164.7 mg/l) than the above values but are still lower than the upper limit for overall migration. Global migration values of five-layer films into aqueous food simulants seems to be independent of material thickness. In contrast, overall migration into iso-octane increases with film thickness.     

Effect of microwave heating on the migration of dioctyladipate and acetyltributylcitrate plasticizers from food-grade PVC and PVDC/PVC films into olive oil and water

Migration of dioctyladipate (DOA) and acetyltributylcitrate (ATBC) plasticizers from plasticized Polyvinylchloride (PVC) and polyvinylidene chloride (PVDC/PVC (Saran) films into both olive oil and distilled water during microwave heating has been studied. The plasticizer migrating into olive oil and water was determined using an indirect GC method after saponification of the ester-type plasticizer (DOA or ATBC) and subsequent collection of the alcohol component of the ester, namely: 2-ethyl-1-hexanol and 1-butanol, respectively. Migration was dependent on heating time, microwave power setting, the nature of the food simulant and the initial concentration of the plasticizer in the film. Migration of DOA into olive oil reached equilibrium after heating for 10 min at full power (604.6 mg DOA/1). Migration into distilled water was 74.1 mg/1 after 8 min of microwave cooking at full power. The amount of ATBC migrating into olive oil reached equilibrium after heating for 10 min at full power (73.9 mg ATBC/1). Migration into distilled water was 4.1 mg/1 after heating at full power for 8 min. Control samples containing olive oil gave DOA migration values which were significantly higher than the upper limit for global migration (60 mg/1) set by the European Community. It is proposed that PVC should not be used in direct contact with food in the microwave oven, while Saran may be used with caution in microwave heating and reheating applications, avoiding its direct contact with high fat foodstuffs.     

Migration of 2-butoxyethyl acetate from polycarbonate infant feeding bottles

An enforcement campaign was carried out to assess the migration of 2-butoxyethyl acetate (2-BEA) from polycarbonate infant feeding bottles intended for repeated use. Migration was measured by three successive migration tests into two of the European Union official food simulants: distilled water and 3% acetic acid testing at 40°C for 10 days. The Danish Veterinary and Food Administration (DVFA) has assessed that a migration above 0.33 mg for 2-BEA and a group of eight related substances kg^-1 foodstuff from plastics articles used exclusively for infants is unacceptable. Migration of 2-BEA was found from eight of 12 bottles. However, migration above the target value of 0.33 mg kg^-1 was not observed in the third decisive test from any of the 12 different brands of polycarbonate feeding bottles. A migration of between 0.05 and 0.26 mg kg^-1 from seven of 12 bottles was measured to 3% acetic acid in the third test, whereas no migration to distilled water was observed in the third test. The average recovery of 2-BEA after the 10-day exposure at the target value of 0.33 mg kg^-1 was 77% into distilled water and 36% into 3% acetic acid. The limited recovery was understandable as 2-BEA was partly hydrolysed in the aqueous food simulants and 2-butoxyethanol, a hydrolysis product and one of the related substances was identified. Quantification was carried out using gas chromatography after liquid/liquid extraction of the food simulant.     

Migration of 4-nonylphenol from polyvinyl chloride food packaging films into food simulants and foods.

Migration of 4-nonylphenol (NP) from polyvinyl chloride (PVC) films for food packaging into food simulants and foods has been studied in domestic applications such as wrapping of food and reheating in a microwave oven. The migration of NP from the PVC films was determined by high-performance liquid chromatography with electrochemical coulometric-array detection (LC/ED). Twelve PVC films intended for commercial use and ten for domestic applications (total: 22 samples) were analysed. Some of the PVC films (two home-use and ten retail-use) contained NP at concentrations of between 500 and 3300 microg/g. Migration of NP from the films was influenced by the test conditions (n-heptane at 25 degrees C for 60 min, distilled water at 60 degrees C for 30 min and 4% acetic acid at 60 degrees C for 30 min). The amount of NP migrating from the PVC films into n-heptane (0.33-1.6 microg/cm2) was higher than the amount migrating into distilled water or 4% acetic acid (up to 9.7 ng/cm2) for the 11 films in which NP was detected. Up to 0.23% of the NP migrated into distilled water and 4% acetic acid and up to 62.5% into n-heptane. In addition, we investigated NP migration into cooked rice samples wrapped in PVC film. Using spiked samples the method gave an average recovery of 83.7% (n = 5) with a standard deviation of 2.5%. Migration of NP ranged from not detectable (< 1.0 ng/g) to 410.0 ng/g by reheating samples in a microwave oven for 1 min and from not detectable to 76.5 ng/g by keeping samples at room temperature for 30 min.     

Target and non-target analysis of migrants from PVC-coated cans using UHPLC-Q-Orbitrap MS: evaluation of long-term migration testing

A simple, rapid and sensitive method for analyzing multi-target and non-target additives in polyvinyl chloride (PVC) food can coatings using ultra-high-performance liquid chromatography coupled to quadrupole-orbital ion-trap mass spectrometry was developed. This procedure was used to study the behaviour of a cross-linking agent, benzoguanamine (BGA), two slip agents, oleamide and erucamide, and 18 other commonly used plasticisers including phthalates, adipates, sebacates, acetyl tributyl citrate and epoxidised soybean or linseed oils. This optimised method was used to detect these analytes in food simulants (water and 3% acetic acid) in a long-term migration test of PVC-coated food cans for a period ranging from 1 day to 1.5 years at 40°C. Although very low detection limits (5 ng ml^–1) were obtained for the majority of compounds, none of the monitored plasticisers and slip agents was detected in simulants extracted from cans over the period of the test. However, the presence of BGA in both aqueous food simulants was confirmed based on high-resolution mass spectrometry, product ion spectra and analysis of a reference standard. The BGA concentration in both simulants continued to increase with storage time: after 1.5 years storage in aqueous food simulants at 40°C, BGA was detected at concentrations up to 84 µg dm^–2. We believe this is the first study describing the long-term migration capacity of BGA from any vinyl coating material intended for use in PVC-coated food cans. Our results may have implications for migration test protocols for food cans that will be stored for extended time periods.     

Effect of γ-radiation on migration behaviour of dioctyladipate and acetyltributylcitrate plasticizers from food-grade PVC and PVDC/PVC films into olive oil

Food-grade PVC and PVDC/PVC films containing 28.3% dioctyladipate (DOA) and 5.0% acetyltributylcitrate (ATBC) plasticizers, respectively, were brought into contact with olive oil and were irradiated with γ-radiation [⁶⁰Co] at doses equal to 4 kGy and 9 kGy corresponding to “cold pasteurization”. Irradiation was carried out at 8–10 °C and samples were subsequently stored at 4–5 °C. Contaminated oil samples were analysed for DOA and ATBC at intervals between 7 h and 97 h of contact, using an indirect GC method. Identical nonirradiated (control) samples were also analysed for DOA and ATBC content. Results showed no statistically significant differences in migrated amounts of DOA and ATBC between irradiated and non-irradiated samples. Neither were differences observed between samples irradiated at 4 kGy and 9 kGy. This was supported by identical IR spectra recorded for irradiated and non-irradiated samples and leads to the conclusion that at such intermediate radiation doses (≤9 kGy) the migration characteristics of both PVC and PVDC/PVC films are not affected. The amount of DOA that migrated into olive oil was dependent on time, reaching equilibrium after approximately 47 h of contact (302.8 mg/l). The amount of ATBC that migrated into olive oil was non-detectable (<1 mg/1) for all samples stored at 4–5 °C after 97 h. In non-irradiated samples (PVDC/PVC in contact with oil) stored at 20 °C, small amounts of migrated ATBC were determined (3.3 and 5.1 mg/l after 29 h and 94 h of contact respectively). Furthermore, in thermally treated samples heated to 80 °C for 30 min and 60 min, the respective amounts of migrated ATBC determined were 2.9 mg/l and 19.3 mg/l.     

Di(2-ethylhexyl) adipate migration from PVC-cling film into packaged sea bream (Sparus aurata) and rainbow trout (Oncorhynchus mykiss) fillets: kinetic study and control of compliance with EU specifications

Polyvinyl chloride (PVC) film containing di(2-ethylhexyl) adipate (DEHA) plasticizer was used to wrap sea bream (Sparus aurata) and rainbow trout (Oncorhynchus mykiss) fillet samples with and without skin. After wrapping the samples were stored at 2 ± 0.5 °C and analyzed for DEHA content at time intervals between 5 and 360 h of contact (kinetic study). Determination of DEHA was performed using a direct gas chromatography (GC) method. Statistically significant differences (p < 0.05) in migration of DEHA were observed between the two fish fillet samples: the mean equilibrium migration amount of DEHA in sea bream was 2.93 mg/dm² film (91.9 mg/kg fillet) corresponding to a loss of 19.0% (w/w) DEHA from PVC film; while the mean equilibrium amount of DEHA in rainbow trout was 3.74 mg/dm² (117.6 mg/kg) corresponding to a loss of 23.9% (w/w) DEHA. The above values for DEHA in sea bream are very close to the limit of 3 mg/dm² of film surface set by the EU for DEHA while the corresponding migration values for rainbow trout exceeded this limit. Diffusion coefficients for DEHA in the PVC film during contact with both fish fillets were calculated and found significantly different between two fish samples. Furthermore, the presence of skin on the fillet decreased migration of DEHA into the fish flesh by a factor of 2.4–2.8. Based on equilibrium migration values of DEHA it is concluded that for a 60-kg adult, a daily consumption of 150 g rainbow trout or 200 g sea bream fillet packaged in PVC film would result in a daily intake of DEHA close to the tolerable daily intake (TDI) of 0.3 mg/kg body weight set by the EU.     

纳米二氧化钛改性LDPE薄膜中纳米钛粒子在食品模拟物中的迁移研究

为探究纳米改性LDPE薄膜中纳米钛粒子在食品模拟物中的迁移规律,根据欧盟法规(EU)NO.10/2011,分别采用蒸馏水、3%乙酸溶液(m/V)、10%乙醇溶液(V/V)、95%乙醇溶液(V/V)作为中性、酸性、脂肪性和酒精性食品模拟物,研究在不同温度条件下(40℃和70℃)纳米钛粒子的迁移情况,并研究了微波和紫外处理对迁移结果的影响。研究发现,纳米钛粒子在四种食品模拟物中的迁移量从高到低依次为:酸性食品模拟物、中性食品模拟物、酒精性食品模拟物和脂肪性食品模拟物,并且温度的升高能够促进纳米钛粒子的迁移。纳米钛粒子的迁移量范围为0.0046 mg/kg~0.61 mg/kg。此外,微波处理也能够促进纳米钛粒子的迁移,紫外处理则没有这样的促进作用。根据欧盟规定所允许的最大迁移量5 mg/kg,迁移实验表明纳米二氧化钛改性LDPE薄膜能够作为一种安全的食品包装膜。     

Migration of di-(2-ethylhexylexyl)adipate plasticizer from food-grade polyvinyl chloride film into hard and soft cheeses

Food-grade polyvinyl chloride (PVC) film containing 28.3% di-(2-ethylhexylexyl)adipate (DEHA) plasticizer was used to wrap three different types of cheese (Kefalotyri, Edam, and Feta). Samples were split into two groups and stored at 5+/-0.5 degrees C. One group was analyzed for DEHA content at intervals between 1 and 240 h of contact (kinetic study), and a second group was cut into slices (1.2 mm thick) after 240 h of cheese/PVC contact and was analyzed for DEHA content (penetration study). The DEHA was determined by indirect gas chromatography. Statistically significant differences in migration of DEHA were observed between the cheese types. Migration of DEHA depended on contact time, fat, and moisture contents, and consistency of cheese samples. Equilibrium conditions were approached after approximately 100 h of contact for Edam and 150 h for Kefalotyri cheese. Equilibrium conditions were not reached for Feta cheese, even after 240 h of contact. After 240 h of contact under refrigeration, the migration of DEHA was approximately 345.4 mg/kg (18.9 mg/dm2) for Kefalotyri, 222.5 mg/kg (12.2 mg/dm2) for Edam, and 133.9 mg/kg (7.3 mg/dm2) for Feta. The loss of DEHA from the PVC film into the three cheese types was 37.8, 24.3, and 14.6%, respectively. These values, with the exception of Feta, were higher than the upper limit for global migration from plastic packaging materials into food and food stimulants set by the European Union (EU) (10 mg/dm2 or 60 mg/kg). After 240 h of cheese/film contact, DEHA was detected in the first three slices beneath the cheese surface (3.6 mm total depth) of Edam cheese and in the first two slices (2.4 mm total depth) of Kefalotryi and Feta cheeses. DEHA was not detected in subsequent layers. The effect of cheese rind on migration of DEHA was studied in Edam and Kefalotyri cheeses. The DEHA migration after 240 h into the first 1 mm beneath the surface of Kefalotyri cheese was 22.4 mg/kg, while DEHA was not detected in Edam cheese.     

Study of the migration behavior of acetyl tributyl citrate from PVDC/PVC film into fish fillets as affected by intermediate doses of electron beam radiation

Food-grade plasticized polyvinylidene chloride/polyvinyl chloride (PVDC/PVC) film (saran wrap) containing acetyl tributyl citrate (ATBC) plasticizer was used to wrap cod and herring fillets. The ratio of film surface to weight of food was ca. 89:1, in contrast to the generally agreed relationship of 6 dm² to 1 kg food (6:1). Wrapped fish samples were subjected to electron beam irradiation at doses equal to 5 and 10 kGy, stored at 4 °C and analyzed for ATBC content at time intervals between 12 and 240 h of contact. Determination of the analyte was performed by ultrasonic-assisted solvent extraction followed by analysis on a gas chromatograph coupled with flame ionization detector. Final ATBC concentrations in cod fillets ranged from 11.1 to 12.8 mg/kg, while the corresponding values for herring samples were between 32.4 and 33.4 mg/kg. Data showed that e-beam radiation at pasteurizing doses did not significantly affect the copolymer’s specific migration characteristics. On the contrary, fat content of the packaged fish fillets substantially affected the diffusion coefficient (D) values, as well as the extent to which migration of ATBC occurred. No violations of the tolerable daily intake (TDI) of 1.0 mg/kg body weight set by the EU for ATBC were found in the present study. However, food overwrapping or rewrapping with flexible films is often applied in household applications. Since in such cases unrealistically high plasticizer concentrations are determined experimentally, present specific migration limits (SML) should be redefined on a different basis.     

Migration of silver from nanosilver–polyethylene composite packaging into food simulants

An analytical method for the determination of silver in food simulants (3% (w/v) aqueous acetic acid or 95% (v/v) aqueous ethanol) was developed based on inductively coupled plasma mass spectrometry (ICP-MS). Recoveries ranged from 87% to 109% and RSDs ranged from 0.7% to 7.8%. The procedure was applied to determine the migration of silver from nanosilver–polyethylene food packaging film into food simulants at different temperatures and migration times. Results indicated that the maximum migration ratios were 1.70%, 3.00% and 5.60% for 3% (w/v) aqueous acetic acid at 20, 40 and 70°C, respectively, while for 95% (v/v) aqueous ethanol the maximum migration ratios were 0.24%, 0.23% and 0.22% at 20, 40 and 70°C.     

Migration of silver from nanosilver-polyethylene composite packaging into food simulants

An analytical method for the determination of silver in food simulants (3% (w/v) aqueous acetic acid or 95% (v/v) aqueous ethanol) was developed based on inductively coupled plasma mass spectrometry (ICP-MS). Recoveries ranged from 87% to 109% and RSDs ranged from 0.7% to 7.8%. The procedure was applied to determine the migration of silver from nanosilver-polyethylene food packaging film into food simulants at different temperatures and migration times. Results indicated that the maximum migration ratios were 1.70%, 3.00% and 5.60% for 3% (w/v) aqueous acetic acid at 20, 40 and 70 °C, respectively, while for 95% (v/v) aqueous ethanol the maximum migration ratios were 0.24%, 0.23% and 0.22% at 20, 40 and 70 °C.     

Long-term wear effects on nanosilver release from commercially available food contact materials

ABSTRACT

Potential consumer exposure to nanoparticles (NPs) from nanoenabled food contact materials (FCMs) has been a driving force for migration studies of NPs from FCMs. Although NP migration from fresh, unused FCMs was not previously observed, conditions that result in significant changes to the surface of FCMs have not been investigated for NP migration into food. Therefore, a quantitative assessment of nanoparticle release from commercially available nanosilver-enabled FCMs was performed using an abrasion protocol to simulate cleaning, cutting, scraping and other stressful use conditions. Laser scanning confocal microscopy (LSCM) analysis showed a general increase in root mean square (RMS) roughness after FCM abrasion, and particle count (for particle sizes from 80 nm to 960 nm) at the surface was 4 orders of magnitude higher for the abraded FCMs. Migration was evaluated using both water and 3% (v/v, volume fraction) acetic acid as food simulants. Low concentrations of total Ag were detected in water simulants with a small portion (<10 ng dm^?2) in the form of silver nanoparticles (AgNPs). Median particle diameter ranged from 39 nm to 50 nm with particle number concentrations on the order of 10⁶ particles dm^{? 2}. Total Ag migration into 3% (v/v) acetic acid was significantly higher than in water; however, 3% (v/v) acetic acid was not suitable for evaluation of NP release due to dissolution of AgNPs to Ag⁺ under acidic solution chemistries.     

Gamma irradiation of cowpea (Vigna unguiculata L. Walp) flours and pastes: Effects on functional,thermal and molecular properties of isolated proteins

In a previous study irradiation of cowpea flours and pastes at medium (10 kGy) and high (50 kGy) doses resulted in significant changes in protein-related functional properties. To understand some of the effects of gamma irradiation on cowpea proteins in particular, we isolated proteins from cowpea flours (FPC) and pastes (PPC) treated with gamma irradiation at 2, 10, and 50 kGy and analyzed their functional, thermal and molecular properties. Nitrogen solubility index of both FPC and PPC decreased, whereas oil absorption and emulsion capacities increased significantly with increasing irradiation dose. Differential scanning calorimetry showed decreases in transition temperatures (T_d) and enthalpies (ΔH), indicating a progressive denaturation of cowpea proteins with increasing irradiation. Size exclusion HPLC revealed increases in protein molecular weights, probably due to protein–protein cross-linking with irradiation in a dose-dependent manner. Reducing SDS-PAGE of FPC and PPC samples seems to suggest that the contribution of disulphide bonds to irradiation-induced cowpea protein–protein cross-linking is small.     

Retention of antioxidant activity in gamma irradiated argentinian sage and oregano

The effect of 30 kGy of gamma radiation on the antioxidant activity of methanolic and aqueous extracts prepared from dry gamma irradiated sage and oregano were analysed. The antioxidant activity was characterised by DPPH radical test and by reducing power assay within an extract concentration range of 0–40 mg/ml of methanol or water. In addition, the total phenolic content in the extracts was determined. From the EC₅₀ estimated values, it was established that, by both methods, oregano extracts showed a higher antioxidant activity than sage extracts. Oregano extracts also showed a phenolic content significantly higher than sage extracts. A good correlation between the phenolic content and the antioxidant activity was also observed. The 30 kGy dose applied to dry sage and oregano for sanitization did not significantly affect the capacity to inhibit the DPPH radical or the reducing power, nor did it affect the total phenolic content of the methanolic and aqueous extract.