Development of an HPLC method for measurements of the stability of Irganox-type polymer antioxidants in fatty food simulants

 A reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed to measure the stability of four Irganox-type polymer antioxidants (Irganox 245, Irganox 1035, Irganox 1098 and Irganox 3114) in an olive oil food simulant and isooctane, which has been proposed as an alternative fatty food simulant. The tests of stability in olive oil were carried out under three different conditions, i.e. 40°C for 10 days, 100°C for 1 h and 175°C for 1 h. The exposure conditions for isooctane were 60°C for 3 h. Results showed that for all additives tested no instability phenomena in olive oil or isooctane simulants were observed under the exposure conditions applied. The analytical methodology developed could eventually be used for stability testing and migration studies of other similarly structured antioxidants in fatty food simulants. Received: 11 September 1997     

Determination of low levels of aziridine in official EU food simulants by capillary gas chromatography

 An analytical method for the determination of the specific migration of aziridine (ethyleneimine) into food simulants at trace levels is described. The method comprises a two-phase (aqueous-organic solvent) derivatization procedure with 4-fluorobenzoyl chloride, using propyleneimine as an internal standard. The derivatization reaction is accomplished very quickly and the organic layer containing the derivatized imine is analysed by capillary gas chromatography using selective nitrogen detection (nitrogen-phosphorus detector). The detection limits of the method were lower than 5 μg/kg in the food simulant. Received: 5 June 1996     

Determination of synthetic phenolic antioxidants in food items using reversed-phase HPLC

A HPLC with gradient elution method for the determination of the synthetic phenolic antioxidants (SPAs) propyl gallate (PG), tertiary butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) in food items is described. A C18 column served as the stationary phase; the gradient elution was formed by acetonitrile and water:acetic acid (1%). The UV detector was set at 280 nm. Under the recommended conditions, separation of the four SPAs was achieved in less than 8 min. Analytical characteristics of the HPLC method such as limit of detection, linear range, and reproducibility were evaluated. Extraction parameters were optimized for the recoveries of the SPAs in different types of food items (cooking oil, margarine and butter, and cheese). Before the HPLC separation, the SPAs were extracted with methanol/acetonitrile (1:1, v/v) and were subjected to vortex/ultrasonic treatment. The extracts were next kept in a freezer (∼2 h) to precipitate co-extracted components. Recoveries of the SPAs when spiked to cooking oil, margarine, butter and cheese at 50 and 200 mg l⁻¹ were in the ranges 93.3–108.3% for PG, 85.3–108.3% for TBHQ, 96.7–101.2% for BHA and 73.9–94.6% for BHT. The method was applied to the determination of SPAs in 38 food items (16 cooking oils, ten margarine, six butter and six cheese samples). The levels of SPAs in positive samples are all below the legal limits of Malaysia.     

Study of the partition coefficients Kp/f of seven model migrants from LDPE polymer in contact with food simulants

This study evaluated the influence of parameters such as temperature and type of low-density polyethylene (LDPE) film on the log K_p/f values of seven model migrants in food simulants. Two different types of LDPE films contaminated by extrusion and immersion were placed in contact with three food simulants including 20% ethanol, 50% ethanol and olive oil under several time–temperature conditions. Results suggest that most log K_p/f values are little affected by these parameters in this study. In addition, the relation between log K_p/f and log P_o/w was established for each food simulant and regression lines, as well as correlation coefficients, were calculated. Correlations were compared with data from real foodstuffs. Data presented in this study could be valuable in assigning certain foods to particular food simulants as well as predicting the mass transfer of potential migrants into different types of food or food simulants, avoiding tedious and expensive laboratory analysis. The results could be especially useful for regulatory agencies as well as for the food industry.     

Comparison of HPLC and GLC methodologies for determination of glucosinolates using reference material

 The reference material rapeseed of known glucosinolate composition, was analysed by HPLC and GLC and two commercially available glucosinolates (glucotropaeolin and sinigrin) were used as internal standards. The HPLC method enabled determination of 11 different glucosinolates (as desulphoglucosinolates) that occur in the rapeseed. Only seven glucosinolates (as trimethylsilylated desulphoglucosinolates) were separated by GLC. The latter method did not allow the determination of methylsulphinylalkyl glucosinolates (glucoiberin, glucoraphanin and glucoallysin) and did not separate optical isomers of 2-hydroxy-3-butenyl glucosinolate (progoitrin and epi-progoitrin). Statistical evaluation of data (t-test, F-test) revealed no significant differences between the tested methods at the 95% confidence level. The advantages and disadvantages of both widely used chromatographic methods are discussed. Received: 26 May 1997 / Revised version: 11 July 1997     

Comparison of HPLC and GLC methodologies for determination of glucosinolates using reference material

 The reference material rapeseed of known glucosinolate composition, was analysed by HPLC and GLC and two commercially available glucosinolates (glucotropaeolin and sinigrin) were used as internal standards. The HPLC method enabled determination of 11 different glucosinolates (as desulphoglucosinolates) that occur in the rapeseed. Only seven glucosinolates (as trimethylsilylated desulphoglucosinolates) were separated by GLC. The latter method did not allow the determination of methylsulphinylalkyl glucosinolates (glucoiberin, glucoraphanin and glucoallysin) and did not separate optical isomers of 2-hydroxy-3-butenyl glucosinolate (progoitrin and epi-progoitrin). Statistical evaluation of data (t-test, F-test) revealed no significant differences between the tested methods at the 95% confidence level. The advantages and disadvantages of both widely used chromatographic methods are discussed. Received: 26 May 1997 / Revised version: 11 July 1997     

Evolution of fatty acid contents in Garnacha and Viura musts during fermentation and the aging of wine

 The evolution of fatty acids during the fermentation of Vitis vinífera var. Garnacha and var. Viura musts as well as during the aging of the rosé and white wines produced from the said musts was studied. In Garnacha must, practically all the fatty acids were consumed, with the exception of the medium-chain fatty acids, by the time that 50% of the sugar was used up. During the second half of fermentation 80.1% of the fatty acids were consumed, with 28.8% of the remaining fatty acids being used up during aging. In Viura must, the total fatty acid concentration declined 46.9% during the first half of fermentation (first 50% of sugar), most noteworthy was the high consumption of unsaturated large-chain fatty acids (72.3%); during the second half of fermentation, 77.2% of the fatty acids were used, with high consumption of the large-chain saturated and unsaturated acids. During the aging of wine, medium-chain fatty acids were excreted and a small amount of unsaturated acids was consumed. Received: 3 March 1997 / Revised version: 21 July 1997     

HPLC analysis of γ-irradiation-induced products of tryptophan in peptides and lysozyme

 The products of γ-irradiation of tripeptides (AWA, LWL, LWM) and lysozyme were determined by HPLC and UV/fluorescence detection. A fast and simple one-step hydrolysis with pronase E (30 – 60 min, 40°C) was developed to release the radiation products, without damage, from the peptide chain. N-Formylkynurenine (NFK), oxindolylalanine (OIA), 4-, 5-, 6- and 7-hydroxytryptophan were the main products of irradiation of peptides and lysozyme. It is possible that the nonphysiological hydroxytryptophan isomers 4-, 6- and 7-hydroxytryptophan could serve as marker substances for irradiated food with a high protein content. Received: 7 April 1997 / Revised version: 10 June 1997     

HPLC analysis of γ-irradiation-induced products of tryptophan in peptides and lysozyme

 The products of γ-irradiation of tripeptides (AWA, LWL, LWM) and lysozyme were determined by HPLC and UV/fluorescence detection. A fast and simple one-step hydrolysis with pronase E (30 – 60 min, 40°C) was developed to release the radiation products, without damage, from the peptide chain. N-Formylkynurenine (NFK), oxindolylalanine (OIA), 4-, 5-, 6- and 7-hydroxytryptophan were the main products of irradiation of peptides and lysozyme. It is possible that the nonphysiological hydroxytryptophan isomers 4-, 6- and 7-hydroxytryptophan could serve as marker substances for irradiated food with a high protein content. Received: 7 April 1997 / Revised version: 10 June 1997     

HPLC determination of polycyclic aromatic hydrocarbons in olive oils

 In this paper, HPLC with spectrofluorimetric detection was applied to the determination of polycyclic aromatic hydrocarbons (PAHs) in olive oils. These compounds may sometimes contaminate vegetable oils because of their specific lipophilic characteristics, which are a significant problem for their extraction and purification from lipid matrices. Some improvements to previously published methods are introduced and satisfactory results for repeatability and recovery were obtained. Data on 51 authentic olive oil samples are reported and it was found that there is usually a limited presence of PAHs in extra virgin olive oils; furthermore, the analysis of some blends of refined and virgin oils shows that the distributions of light and heavy PAHs are different with the content of the former being lower in refined samples. As an example of this fact, two samples of lampante oil were followed throughout the refining step. Received: 23 September 1996 / Revised version: 17 December 1996     

Development and validation of an HPLC method with fluorescence detection for the determination of fluorescent whitening agents migrating from plastic beverage cups

An HPLC method with fluorescence detection has been developed and validated for the quantification of six fluorescent whitening agents (FWA) in plastic beverage cups after extraction and in food simulants after migration at 70°C for 2 h. The sensitivity of the method was high with LODs ranging from 0.053 to 0.251 μg kg^?1 and LOQs from 0.107 to 0.504 μg kg^?1. Accuracy and precision were highly acceptable, with recoveries greater than 82% and RSDs (%) below 16%. The expanded combined uncertainty was found to be less than 23% for the measurements of all studied FWAs. In extracting the analytes from food contact materials (FCM), accelerated solvent extraction (ASE) and Soxhlet extraction were applied using ethanol as the extraction solvent. The results obtained for FWA in 10 different food plastic cups, made from different polymers, were compared. The ASE technique proved to be faster, more effective and efficient than Soxhlet extraction. Migration tests with official food simulants from Regulation (EU) No 10/2011 showed that the substances studied could potentially migrate using the selected migration conditions. The most pronounced effect was observed in case of simulant D1 (50% w/v ethanol in water). The analytical method proved to be a simple, fast, sensitive and reliable tool for the simultaneous quantification of six of the most used FWAs in both FCM extracts and food simulants after migration experiments.     

Development and single-laboratory validation of an HPLC method for the determination of cyclamate sweetener in foodstuffs

A method for the determination of cyclamate has been developed and single-laboratory validated for a range of foodstuffs including carbonated and fruit-juice drinks, fruit preserves, spreads, and dairy desserts. The method uses the peroxide oxidation of cyclamate to cyclohexylamine followed by derivatization with trinitrobenzenesulfonic acid and analysis by a modified reversed-phase high-performance liquid chromatography-ultraviolet light (HPLC-UV). Cycloheptylamine is used as an internal standard. The limits of detection were in the range 1–20 mg kg^?1 and the analysis was linear up to 1300 mg kg^?1 cyclamic acid in foods and up to 67 mg l^?1 in beverages. Analytical recovery was between 82% and 123%, and results were recovery corrected. Precision was within experimentally predicted levels for all of the matrices tested and Horrat values for the combined standard uncertainty associated with the measurement of cyclamate between 0.4 (water-based drinks) and 1.7 (spreads). The method was used successfully to test three soft drink samples for homogeneity before analytical performance assessment. The method is recommended for use in monitoring compliance and for formal testing by collaborative trial.     

Stability testing of selected plastics additives for food contact in EU aqueous, fatty and alternative simulants

Within the framework of the AIR3-CT94-2360 EUproject, the stability of three plastics additives in three EU aqueous and fatty food simulants and in two alternative simulants was studied under various timetemperature conditions. The additives tested were bis(2-ethylhexyl) adipate (DEHA), bis(2-ethylhexyl) phthalate (DEHP) and octadecyl 3-(3,5-di- tert -butyl4-hydroxyphenyl) propionate (Irganox 1076). The various test conditions included exposures of 10 days at 40 o C, 1h at reflux temperature for all aqueous simulants, 10 days at 40 o C and 1h 175 o C for the olive oil and 2 days at 20 o C and 3h at 60 o C for the isooctane simulant. Following the exposure, the additive samples were extracted from aqueous simulants with hexane. A sonication step was necessary to ensure maximum extraction of control samples. In the case of the isooctane simulant, the samples were analysed directly from the simulant. The oil samples were extracted by acetonitrile. The extracts of samples exposed to various heat conditions as well as unexposed spiked controls and blanks were analysed by gas chromatography (GC) on a non-polar (5% -phenyl)-methylpolysiloxane capillary column with high temperature capabilities. The results showed that DEHA, DEHP and Irganox 1076 were stable at 40 o C and at reflux temperature in ethanolic or acidic aqueous simulants. The various additives were also stable in the organic isooctane simulant as well as in the fatty simulant olive oil. Studies on the stability of such additives used in food packaging are designed for regulatory purposes as an aid to decide whether the legislation should regulate limits for plasticizers based on a quantity in the food packaging itself or based on an ingested dose by the consumer.     

Effectiveness of a natural Rosemary (Rosmarinus officinalis) extract on the stability of filleted and minced fish during frozen storage

 The objective of this study was to evaluate the effect of adding a natural Rosemary (Rosmarinus officinalis L.) extract to filleted and minced frozen fish and to compare the fat stability of the samples with that of the controls. Horse mackerel (Trachurus trachurus), a relatively fatty fish, and Mediterranean hake (Merluccius mediterraneus), a low-fat fish, were used. Fat stability evaluation was done by comparing the changes of the malondialdehyde (MDA) content and the percentage of polyunsaturated fatty acid (PUFAs) degradation that occurred during frozen storage at –18°C for 120 days. Total volatile bases-N (TVB-N) were also measured to assess for quality. The results showed that the natural antioxidant extract retarded the oxidation process throughout storage. The control samples of both filleted and minced frozen fish of both species showed a significant reduction (^* P <0.05) of PUFAs until day 50 of storage, while the oxidation was gradual but slower in the treated samples. Fillets and minced samples of both species treated with antioxidant contained significantly (^* P <0.05) less MDA compared with the controls during storage. Received: 2 December 1996     

Effectiveness of a natural Rosemary (Rosmarinus officinalis) extract on the stability of filleted and minced fish during frozen storage

 The objective of this study was to evaluate the effect of adding a natural Rosemary (Rosmarinus officinalis L.) extract to filleted and minced frozen fish and to compare the fat stability of the samples with that of the controls. Horse mackerel (Trachurus trachurus), a relatively fatty fish, and Mediterranean hake (Merluccius mediterraneus), a low-fat fish, were used. Fat stability evaluation was done by comparing the changes of the malondialdehyde (MDA) content and the percentage of polyunsaturated fatty acid (PUFAs) degradation that occurred during frozen storage at –18°C for 120 days. Total volatile bases-N (TVB-N) were also measured to assess for quality. The results showed that the natural antioxidant extract retarded the oxidation process throughout storage. The control samples of both filleted and minced frozen fish of both species showed a significant reduction (^* P <0.05) of PUFAs until day 50 of storage, while the oxidation was gradual but slower in the treated samples. Fillets and minced samples of both species treated with antioxidant contained significantly (^* P <0.05) less MDA compared with the controls during storage. Received: 2 December 1996     

SPE and MSPD as pre-separation techniques for HPLC of tetracyclines in meat, milk and cheese

 Solid phase extraction (SPE) and Matrix solid phase dispersion (MSPD) have been tested as pre-separation procedures for high-performance liquid chromatography (HPLC) determination of tetracycline antibiotics in milk, meat and cheese. The extraction recoveries ranged from 48% to 86% for SPE and from 89% to 93% for MSPD at concentration levels of the maximal residual limits (MRL) recommended by the European Union to be 100 ng/g for the tetracyclines oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC). The detection limits were 15 – 22 ng/g for SPE and 30 ng/g for MSPD. Following the relatively simple SPE procedure we used a Lichrosorb RP-18 column and a diode array detector for HPLC. Results dealing with analysis of tetracyclines HPLC in cheese are published for the first time. Received: 7 March 1997     

On the reaction of L-ascorbic acid with propylamine under various conditions: quantification of the main products by HPLC/DAD

 The reaction of _L-ascorbic acid (AA) with proteins (protein ascorbylation) has a considerable impact on food processing and health. So far four products have been isolated and identified which can be formed from AA and lysine derivatives. Thus, 2-deoxy-2-(propylamino)ascorbic acid, 3-deoxy-3-(propylamino)ascorbic acid, oxalic acid monopropylamide and oxalic acid dipropylamide were synthesized and an HPLC system for their separation and quantification was developed. Then, mixtures of AA and propylamine, as a model compound for lysine derivatives, were reacted under various conditions and product yields were determined in relation to reaction time, temperature, amine concentration and pH value. The results were discussed in detail and can help to evaluate the contribution of the four products to protein and lysine ascorbylation under different conditions. Received: 2 September 1997 / Revised version: 27 November 1997     

On the reaction of L-ascorbic acid with propylamine under various conditions: quantification of the main products by HPLC/DAD

 The reaction of _L-ascorbic acid (AA) with proteins (protein ascorbylation) has a considerable impact on food processing and health. So far four products have been isolated and identified which can be formed from AA and lysine derivatives. Thus, 2-deoxy-2-(propylamino)ascorbic acid, 3-deoxy-3-(propylamino)ascorbic acid, oxalic acid monopropylamide and oxalic acid dipropylamide were synthesized and an HPLC system for their separation and quantification was developed. Then, mixtures of AA and propylamine, as a model compound for lysine derivatives, were reacted under various conditions and product yields were determined in relation to reaction time, temperature, amine concentration and pH value. The results were discussed in detail and can help to evaluate the contribution of the four products to protein and lysine ascorbylation under different conditions. Received: 2 September 1997 / Revised version: 27 November 1997     

高效液相色谱法测定发酵食品中组胺的含量

建立了柱前衍生—高效液相色谱分析食品中组胺含量的方法,通过对广州市售不同品牌的大豆发酵制品、酸奶和啤酒中组胺含量的测定,对各种食品的组胺含量有一个初步的了解,为保障食品安全提供技术依据。检测结果为豆豉中组胺平均浓度为464.28 mg/kg,豆酱为481.50 mg/kg,酱油为461.78 mg/L,三类大豆发酵制品组胺浓度平均值没有明显区别;酸奶样品中组胺平均含量为312.15 mg/kg;啤酒样品中组胺平均含量为2.36 mg/L。广州市售的大豆发酵制品、酸奶和啤酒中均有组胺检出,其中大豆发酵制品中组胺含量普遍较高。