Determination of patulin in apple and quince products by GC–MS using C5–7 patulin as internal standard

A reliable gas chromatographic mass spectrometric method has been validated for the determination of trace levels (<10 μgL⁻¹) of patulin in apple products and quince jam. The method was based on extraction of patulin with ethyl acetate-hexane, alkalinisation and silylation with N,O-bis-trimethylsilyltrifluoroacetamide with 1% of trimethylchloro-silane. The accurate determination of patulin was achieved by employing commercial ¹³C_5–7 patulin labelled as an internal standard, which allowed compensating target analyte losses and enhancement or suppression matrix effects. Limits of detection and quantification of method using real samples were 0.4 and 1.6 μgkg⁻¹, respectively. Recoveries of patulin from samples spiked at 8–50 μgkg⁻¹ levels ranged between 71% and 89%. The repeatability of measurements (expressed as relative standard deviation) was lower than 16%. The method was successfully applied to the determination of patulin in apple fruit and apple products including juice, cider and baby food, and also in quince fruit and quince jam. A new PCR system for the detection of Penicillium expansum in samples containing highly degraded DNA was developed which permitted the detection of the mould in 2/3 of the samples containing patulin, including juices and jams.     

Nutrient contents of kale (Brassica oleraceae L. var. acephala DC.)

Fructose, glucose and sucrose, as the major soluble sugars and citric and malic acids, as the major organic acids, were identified and determined in kale (Brassica oleraceae L. var. acephala DC., black cabbage) leaves. Fructose was the predominant sugar (2011 mg 100 g⁻¹ dry wt) identified, followed by glucose (1056 mg 100 g⁻¹ dry wt) and sucrose (894 mg 100 g⁻¹ dry wt). The contents of citric and malic acids were at 2213 and 151 mg 100 g⁻¹ dry wt in the leaves. The 16:0, 18:2n − 6 and 18:3n − 3 fatty acids were the most abundant fatty acids in the leaves. Considering the level of these fatty acids, 18:3n − 3 was found to be the highest (85.3 μg g⁻¹ dry wt), contributing 54.0% of the total fatty acid content. Linoleic acid (18:2n − 6), being the second most abundant fatty acid was present at 18.6 μg g⁻¹ dry wt, contributing 11.8% of the total fatty acid content. In the seed oil of kale, 22:1n − 9 was the most abundant fatty acid (4198 μg g⁻¹ dry wt, 45.7%), with 18:2n − 6 (1199 μg g⁻¹ dry wt, 12.3%) and 18:1n − 9 (1408 μg g⁻¹ dry wt, 14.8%) being the second next most abundant fatty acids. The most abundant amino acid was glutamic acid (Glu) which was present at 33.2 mg g⁻¹ dry wt. Aspartic acid, which was the second most abundant amino acid, was present at 27.6 mg g⁻¹ dry wt and accounted for 10.2% of the total amino acid content of kale leaf. The amino acid content was assessed by comparing the percentages of the essential amino acids in kale leaf versus those of a World Health Organization (WHO) standard protein. The protein of kale leaf compares well with that of the WHO standard. Only one amino acid, lysine, had a score that fell below 100%; the lysine score of kale leaf was 95%. This study attempts to contribute to knowledge of the nutritional properties of the plant. These results may be useful for the evaluation of dietary information.     

Comparison of the cell wall composition for flesh and skin from five different plums

Cell walls were isolated from flesh and skin of five plum varieties corresponding to three species (Prunus domestica L., Prunus salicina Lindl. and Prunus insititia Lindl.) using the alcohol-insoluble solids (AIS) procedure. Yields varied from 83 to 114 g kg⁻¹ dry weight in the flesh and from 192 to 361 g kg⁻¹ dry weight in the skins. Their main sugars were uronic acid (224–322 mg g⁻¹ AIS), cellulosic glucose (139–170 mg g⁻¹ AIS), galactose and arabinose. Galactose and arabinose ratio were variable between the varieties. The degrees of methylation were high (62–84).     

Flow injection chemiluminescent detection of gallic acid in olive fruits

One economic and environment friendly flow injection chemiluminescent method for the determination of gallic acid was developed. It was based on the inhibited chemiluminescent emission of alkaline luminol–KMnO₄ system by gallic acid. The logarithm of the difference of chemiluminesent intensity of the alkaline luminol–KMnO₄ system in the absence of gallic acid from that in the presence of gallic acid was linear with the logarithm of the concentration of gallic acid in the range from 1.0 × 10⁻⁹ to 5.0 × 10⁻⁵ g ml⁻¹ with a detection limit of 2.2 × 10⁻¹⁰ g ml⁻¹. The relative standard deviation of eleven determinations of 1.0 × 10⁻⁶ g ml⁻¹ gallic acid was 1.7%. The method was successfully applied to the determination of gallic acid in olive fruits.     

The reduction of Cu(II)/neocuproine complexes by some polyphenols: Total polyphenols determination in wine samples

A new method is presented for spectrophotometric determination of total polyphenols content in wine. The procedure is a modified CUPRAC method based on the reduction of Cu(II), in hydroethanolic medium (pH 7.0) in the presence of neocuproine (2,9-dimethyl-1,10-phenanthroline), by polyphenols, yielding a Cu(I) complexes with maximum absorption peak at 450 nm. The absorbance values are linear (r = 0.998, n = 6) with tannic acid concentrations from 0.4 to 3.6 μmol L⁻¹. The limit of detection obtained was 0.41 μmol L⁻¹ and relative standard deviation 1.2% (1 μmol L⁻¹; n = 8). Recoveries between 80% and 110% (mean value of 95%) were calculated for total polyphenols determination in 14 commercials and 2 synthetic wine samples (with and without sulphite). The proposed procedure is about 1.5 more sensitive than the official Folin–Ciocalteu method. The sensitivities of both methods were compared by the analytical responses of several polyphenols tested in each method.     

Spectrophotometric determination of zinc in foods using N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone: Evaluation of a new analytical reagent

N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone (ECCT) is proposed as a new sensitive reagent for the extractive spectrophotometric determination of zinc(II). The ECCT forms yellow colored species of zinc(II) at pH range 3.0–5.5 and the complex was extracted into benzene. The Zn(II)–ECCT complex shows maximum absorbance at 420 nm with molar absorptivity and Sandell’s sensitivity being 1.55 × 10⁴ lit mol⁻¹ cm⁻¹ and 4.212 × 10⁻³ μg cm⁻², respectively. The system obeys Beer’s law in the range of 0.4–6.0 mg/l, with an excellent linearity in terms of correlation coefficient value of 0.999. Most of the common metal ions generally found associated with zinc do not interfere. The repeatability of the method was checked by finding relative standard deviation (RSD). The developed method has been successfully employed for the determination of zinc(II) in foods. Various certified reference materials (NIST 1573, NBS 1572 and NIST SRM 8435) have been tested for the determination of zinc for the purpose of validation of the present method.     

Chemical composition of cultivated seaweed Ulva clathrata (Roth) C. Agardh

Samples of cultivated Ulva clathrata were collected from a medium scale system (MSS, 1.5 × 1.5 m tank), or from a large scale system (LSS, 0.8 ha earthen pond). MSS samples were dried directly while the LSS sample was washed in freshwater and pressed before drying. Crude protein content ranged 20–26%, essential amino acids accounting for 32–36% of crude protein. The main analysed monosaccharides were rhamnose (36–40%), uronic acids (27–29%), xylose (10–13%) and glucose (10–16%). Some notable variations between MSS and LSS samples were observed for total dietary fibre (26% vs 41%), saturated fatty acids (31% vs 51%), PUFAS (33% vs 13%), carotenoids (358 vs 169 mg kg⁻¹ dw) and for Ca (9 vs 19 g kg⁻¹), Fe (0.6 vs 4.2 g kg⁻¹), Cu (44 vs 14 mg kg⁻¹), Zn (93 vs 17 mg kg⁻¹) and As (2 vs 9 mg kg⁻¹). The chemical composition of U. clathrata indicates that it has a good potential for its use in human and animal food.     

Studies on seed characteristics and chemical composition of three morphotypes of Mucuna urens (L.) Medikus – Fabaceae

Seed characteristics and nutrient composition of three morphotypes of big-grained Mucuna urens (L.) Medikus were studied. Results showed that 100-seed weight ranged from 3200.2 to 4700.9 g, cotyledon weight per seed (23.2–26.6 g) and testa weight per seed (9.0–21.2 g). The testa constituted 43.7%, 28.1% and 44.7% of the average seed weight for morphotypes 1, 2 and 3, respectively. The cotyledon also constituted 56.3%, 71.9% and 55.3% of the average seed weight for morphotypes 1, 2 and 3, respectively. Nutrient composition analyses showed that the three morphotypes of M. urens are good sources of crude protein (19.97–20.57 g 100 g⁻¹), carbohydrate (72.39–75.49 g 100 g⁻¹) and fat (1.84–5.05 g 100 g⁻¹). Other nutritional components, including ascorbic acid, calcium and phosphorus are present in the three morphotypes in moderate amounts. The iron content of the M. urens is low. The three morphotypes contain appreciable amounts of essential amino acid. The oxalate content is low. The variations observed in the seed characteristics and nutrient compositions are suspected to be due to genotype. Genetic improvement of this plant is recommended to remove the itching hair trait so as to encourage its cultivation.     

Flow injection analysis of nitrate-N determination in root vegetables: Study of the effects of cooking

Vegetables are the major vehicles for the entry of nitrate into the human system. Ever-increasing concern over nitrate toxicity has directed a number of countries to lay down maximum allowable threshold concentrations with regards to nitrate-N in vegetables. Fiji is an independent island nation, located in the southern Pacific Ocean, has a tropical oceanic climate and hence expected to have high nitrate-N levels in vegetables. Thus, the present study was devoted to establish a flow injection analysis (FIA) technique for nitrate-N determination in Fiji’s commonly consumed fresh and cooked root vegetables such as potato (Solanum tuberosum), dalo (Colocasia esculenta), sweet potato (Ipomoea batatas) and carrot (Daucus carota L.). Activated carbon extraction technique was applied to extract nitrate-N. FIA with colorimetric detection technique having linear dynamic range of determination 1.0–20.0 mg L⁻¹ and detection limit of 0.042 mg L⁻¹ (0.34 mg kg⁻¹), using sulphanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride as colour reagents, was used to determine nitrate-N contents in selected fresh and cooked root vegetables. The samples throughput was 38 h⁻¹. The effects of various cooking (boiling, baking and frying) methods on nitrate-N contents in root vegetables have also been studied. The study shows that the nitrate content of fresh root vegetables ranges from 53.76–258.00 mg kg⁻¹ whereas boiling reduces nitrate content by 23.30–42.62%. The frying in soya bean oil elevates nitrate contents from 204.53–299.12% but after baking nitrate contents remains almost constant with slight increasing trend from 2.80–8.43%. A comparison of the nitrate obtained by standardised method and the nitrate contents in vegetables of other countries are also presented.     

Selected arsenic species: As(III), As(V) and dimethylarsenic acid (DMAA) in Xerocomus badius fruiting bodies

The aim of the study was to determine the content of As(III), As(V) and DMAA (dimethylarsinic acid) in Xerocomus badius fruiting bodies collected from selected Polish forests from areas subjected to very low or high anthropopressure and some commercially available samples obtained from the Polish Sanitary Inspectorate. The arsenic species determination was provided by two independent HPLC–HG-AAS hyphenated systems. The results show high levels (up to 27.1, 40.5 and 88.3 mg kg⁻¹ for As(III), As(V) and DMAA, respectively) of arsenic and occurrence of different species in mushrooms collected from areas subjected to high anthropopressure and two commercially available samples. For mushroom samples collected from areas not subjected to high anthropopressure and two commercially available samples the arsenic species level was below 0.5 mg kg⁻¹ for each arsenic form. Therefore, the accumulation of arsenic by mushrooms may lead to high (toxic for humans) arsenic concentrations, and arsenic species levels should be monitored in mushroom foodstuffs.     

Comparison of free amino acid,carbohydrates concentrations in Korean edible and medicinal mushrooms

Ten popular species of both edible and medicinal Korean mushrooms were analysed for their free amino acids and disaccharides. The average total free amino acid concentration was 120.79 mg g⁻¹ in edible mushrooms and 61.47 mg g⁻¹ in medicinal mushrooms, respectively. The average total of free amino acids for all mushrooms, edible mushrooms and medicinal mushrooms was 91.13 mg g⁻¹. Agaricus blazei (227.00 mg g⁻¹) showed the highest concentration of total free amino acids; on the other hand, Inonotus obliquus (2.00 mg g⁻¹) showed the lowest concentration among the 10 species of mushrooms. The average total carbohydrates concentration was 46.67 mg g⁻¹ in the 10 species of mushrooms, where the edible mushrooms contained 66.68 mg g⁻¹ and the medicinal mushrooms contained 26.65 mg g⁻¹. The carbohydrates constituents of the 10 mushroom species were mainly mannose (36.23%), glucose (34.70%), and xylose (16.83%).     

Determination of minor carbohydrates in carrot (Daucus carota L.) by GC–MS

Minor carbohydrates present in carrot (Daucus carota L.) have been studied by GC–MS analysis of their trimethylsilyl derivatives because of their remarkable role in a variety of biological functions. Scyllo-inositol and sedoheptulose (d-altro-2-heptulose), identified for the first time in this paper were present in all the carrots analysed in concentrations ranging 1.5–5.8 and 1.4–24.6 mg g⁻¹ dried weight, respectively. Other minor carbohydrates detected in carrot were myo- inositol (2.2–9.8 mg g⁻¹) and mannitol (traces-1.3 mg g⁻¹). Whereas small amounts (close to 2 mg g⁻¹) of scyllo-inositol were experimentally determined in other vegetables from the Apiaceae family (parsley, coriander and fennel), sedoheptulose was only detected at trace levels.     

Monitoring of fatty acid composition in virgin olive oil by Fourier transformed infrared spectroscopy coupled with partial least squares

A rapid Fourier transformed infrared (FTIR) attenuated total reflectance (ATR) spectroscopic method was applied to the determination of fatty acid (FA) profile and peroxide value (PV) of virgin olive oil. Calibration models were constructed using partial least squares (PLS) regression. A FA calibration model was constructed in the spectral range from 3033 to 700 cm⁻¹. Oleic acid (62.0–80.0%), linoleic acid (5.3–15.0%), saturated fatty acids (SFA, 12.6–19.7%), mono-unsaturated fatty acids (MUFA, 64.4–81.0%) and poly-unsaturated fatty acids (PUFA, 6.0–15.9%) were considered for chemometric analysis. PV (5.7–15.7 meq O₂ kg⁻¹) was calibrated using the signal of the full spectral range 4000–700 cm⁻¹ with first derivative pre-treatment. The LODs of the FTIR-chemometric methods were: 3.0% for oleic acid, 0.5% for linoleic acid, 1.3% for SFA, 3.0% for MUFA, 0.3% for PUFA and 1.0 meq O₂ kg⁻¹ for PV. Analytical methods were evaluated by use of validation samples (n = 25 for all the FA related parameters and n = 10 for PV) with nearly quantitative recovery rates (98–103%). The proposed method provided results comparable to official procedures, with the advantages of being less expensive and more rapid.     

Milk β-lactoglobulin complexes with tea polyphenols

The effect of milk on the antioxidant capacity of tea polyphenols is not fully understood. The complexation of tea polyphenols with milk proteins can alter the antioxidant activity of tea compounds and the protein secondary structure. This study was designed to examine the interaction of β-lactogolobulin (β-LG) with tea polyphenols (+)-catechin (C), (−)-epicatechin (EC), (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG) at molecular level, using FTIR, CD and fluorescence spectroscopic methods as well as molecular modelling. The polyphenol binding mode, the binding constant and the effects of polyphenol complexation on β-LG stability and secondary structure were determined. Structural analysis showed that polyphenols bind β-LG via both hydrophilic and hydrophobic interactions with overall binding constants of K_C–β-LG = 2.2 (±0.8) × 10³ M⁻¹, K_EC–β-LG = 3.2 (±1) × 10³ M⁻¹, K_ECG–β-LG = 1.1 (±0.6) × 10⁴ M⁻¹ and K_EGCG–β-LG = 1.3 (±0.8) × 10⁴ M⁻¹. The number of polyphenols bound per protein molecule (n) was 1.1 (C), 0.9 (EC), 0.9 (ECG) and 1.3 (EGCG). Molecular modelling showed the participation of several amino acid residues in polyphenol–protein complexation with extended H-bonding network. The β-LG conformation was altered in the presence of polyphenols with an increase in β-sheet and α-helix suggesting protein structural stabilisation. These data can be used to explain the mechanism by which the antioxidant activity of tea compounds is affected by the addition of milk.     

Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea

A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al³⁺ to form reddish complexes which had maximum absorption wavelength at 499.0 nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1-1.0 mg L⁻¹, with detection limit of 0.05 mg L⁻¹ was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6 mg L⁻¹ Al³⁺ (n = 11). Sample throughput of 35 h⁻¹ was achieved with the consumption of 3 mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method.     

Determination of molybdenum by adsorptive anodic stripping voltammetry of molybdenum–alizarin violet complex at an acetylene black paste electrode

A reliable and sensitive procedure for the determination of trace levels of molybdenum by adsorptive anodic stripping voltammetry is proposed. The method is based on adsorptive accumulation of the molybdenum (Mo)–alizarin violet (AV) complex onto an acetylene black paste electrode (ABPE), followed by oxidation of the adsorbed species by voltammetric scan using a second-order derivative modulation. For voltammetric determination of molybdenum, the parameters influencing the peak current have been optimized. Under the selected conditions, the electrode demonstrated linear response over a wide range of Mo(VI) concentration (6.0 × 10⁻⁹–1.0 × 10⁻⁵ mol/L), the detection limit was 2.0 × 10⁻⁹ mol/L (S/N = 3) for 120 s accumulation. The effects of potential interfering ions were studied, and it was found that the proposed procedure was free from most interferences. The method has been applied to the determination of molybdenum in plant foodstuffs, and satisfied results were obtained.     

Effect of phosphorus on the fruit yield and food value of two landraces of Trichosanthes cucumerina L.- Cucurbitaceae

Studies were conducted in the early season of 2002 and 2003 at the Teaching and Research Farm, Obafemi Awolowo University, Ile-Ife, Nigeria to evaluate the effect of phosphorus (P) on fruit yield and chemical composition of two landraces of Trichosanthes cucumerina L. For the purpose of the study, two landraces of T. cucumerina named Landrace I and Landrace II were used. The five levels of phosphorus evaluated were 0, 30, 60, 90 and 120 kg P₂O₅ ha⁻¹ using single super phosphate fertilizer (8% P). Statistical analysis showed that 90 kg P₂O₅ ha⁻¹ gave statistically significant higher fruit yield (16.4 tons ha⁻¹) compared to other P levels. The fruit yield of the two Landraces did not differ significantly. Except for crude protein content, the 90 kg P₂O₅ ha⁻¹ produced significantly higher ether extract (1.22 g 100 g⁻¹), crude fibre (1.93 g 100 g⁻¹), moisture content (90.5 g 100 g⁻¹), ash (0.90 g 100 g⁻¹), total sugars (0.81 g 100 g⁻¹) and ascorbic acid (28.7 mg 100 g⁻¹) than other P levels. The essential amino acids compositions were also significantly higher at 90 g 100 g⁻¹ compared to other lower P levels. Landrace I had significantly higher ether extract (0.90 g 100 g⁻¹) content than Landrace II (0.62 g 100 g⁻¹) while Landrace II in turn had significantly higher total sugar (0.76 g 100 g⁻¹) compared to Landrace I (0.61 g 100 g⁻¹). The essential amino acids composition is high and the oxalate composition is low. The high ascorbic acid and amino acid content together with a low oxalate composition suggested a strong basis for encouraging the cultivation of this indigenous fruit vegetable to augment nutrient requirement, improve diet and consequently alleviate poverty, preserve the biodiversity and increase the gene bank of neglected wild species of high quality nutrient sources.     

Determination of selenium in garlic (Allium sativum) and onion (Allium cepa) by electro thermal atomic absorption spectrometry

A separation/enrichment procedure has been developed for the determination of selenium in garlic and onion samples by electrothermal atomic absorption spectrometry (ET-AAS) as a slurry sampling after preconcentration with 3,3-diaminobenzidine (DAB) reagent on the activated carbon. The influences of pH, time, amount of carbon and complexing reagent were outlined. The effect of acids used in the digestion of samples was also studied and compared. Selenium level was found to be 0.024 μg g⁻¹ for onion (n = 5; LOD – 0.5 μg L⁻¹; LOQ – 1.7 μg L⁻¹) and 0.015 μg g⁻¹ for garlic (n = 5; LOD – 1.3 μg L⁻¹; LOQ – 3.3 μg L⁻¹). Three different samples of garlic were analyzed by k₀-instrumental neutron activation analysis (k₀-INAA) at the Jozef Stefan Institute (JSI). The data obtained by k₀-INAA show that the content of selenium overlapped the results obtained by ET-AAS.     

Folic acid complexes with human and bovine serum albumins

The interaction of folic acid with human serum (HSA) and bovine serum albumins (BSA) at physiological conditions, using constant protein concentration and various folic acid contents was investigated. FTIR, UV–visible and fluorescence spectroscopic methods as well as molecular modelling were used to analyse folic acid binding sites, the binding constant and the effect on HSA and BSA stability and conformations. Structural analysis showed that folic acid binds HSA and BSA via both hydrophilic and hydrophobic contacts with overall binding constants of K_{folic acid–HSA} = 8.1 (±0.5) × 10⁴ M⁻¹ and K_{folic acid–BSA} = 1.0 (±0.3) × 10⁵ M⁻¹. The number of bound acid molecules per protein was 1.7 (±0.4) for HSA and 1.5 (±0.3) for BSA complexes. Molecular modelling showed participation of several amino acids in folic acid–protein complexes stabilised by hydrogen bonding network. Folic acid complexation altered protein secondary structure by major reduction of α-helix from 59% (free HSA) to 35% (acid-complex) and 62% (free BSA) to 25% (acid-complex) with an increase in random coil, turn and β-sheet structures indicating protein unfolding. The results suggest that serum albumins might act as carrier proteins for folic acid in delivering it to target molecules.     

Use of Fourier transform infrared spectroscopy for rapid comparative analysis of Bacillus and Micrococcus isolates

The identification of foodborne microorganisms and their endospores in food products are important for food safety. The present work compares Bacillus (Bacillus licheniformis, Bacillus circulans and Bacillus subtilis) and Micrococcus (Micrococcus luteus) species with Fourier transform infrared (FTIR) spectroscopy. Our results show that there are several characteristic peaks belonging to both the Micrococcus and Bacillus species which can be used for the identification of these foodborne bacteria and their endospores. For Micrococcus species, a new band was observed at 1338 cm⁻¹ which may be due to acetate oxidation via the carboxylic acid cycle. The bands at 1313 cm⁻¹ and 1256 cm⁻¹ can be explained by an exopolymer formation and the other bands at 1074 cm⁻¹ and 550 cm⁻¹, may be due to the glycogen-like storage material in Micrococcus spp. There are also characteristic peaks at 993 cm⁻¹ and 801 cm⁻¹ for these bacterial species. Different Bacillus species also showed characteristic peaks at 1000–500 cm⁻¹ region. Dipicolinic acid (DPA) bands at ∼728 cm⁻¹ and ∼703 cm⁻¹ seen only in B. circulans were the marker of an endospore formation.