Main Organic Acids in Rice Wine and Beer Determined by Capillary Electrophoresis with Indirect UV Detection Using 2, 4-Dihydroxybenzoic Acid as Chromophore

A rapid and sensitive analytical method for the determination of main organic acids in wines was developed by capillary electrophoresis (CE) with indirect UV detection. Separation parameters including the pH of electrolyte, chromophore, and its concentration were optimized. The results showed that the optimal electrolyte for the separation of organic acids consisted of 10 mmol L^?1 2, 4-dihydroxybenzoic acid (DHBA) at pH 3.6 containing 0.4 mmol L^?1 cetyltrimethlammonium bromide (CTAB). DHBA as chromphore was selected based on the close mobility to the analyte and relatively large molar extinction coefficient. The method showed good linearity with limits of detection (LOD), ranging from 0.5 to 7.5 mg L^?1. The relative standard deviation (RSD) of interday precisions for the peak area and the migration time were less than 7.2 and 0.8 %, respectively. The recoveries of the analyte in Chinese rice wine sample were between 90.3 and 106.9 % with RSD ranging from 1.4 to 8.9 %. The method was successfully applied to the commercial rice wine and beer samples with dilution and filtration.     

Aflatoxin M1 in raw,UHT milk and dairy products in Sicily (Italy)

A survey on 73 milk samples from different animal breeds and 24 dairy products samples from Sicily, Italy, was carried out for the presence of aflatoxin M₁ (AFM1) by LC-fluorescence detection after immunoaffinity cleanup. AFM1 was detected in 48% and 42% of the milk and dairy samples at concentration ranges between <5.0–16.0 and <5.0–18.0 ng L^?1, respectively. Within the raw milk samples, 92% had an AFM1 content below 5.0 ng L^?1, in 7% of the cases it was in the range 5.0–10.0 ng L^?1 and 1% was contaminated between 10.0 and 20.0 ng L^?1. For the dairy products, ultra-high-temperature treated (UHT) milk, milk cream and cheese, the incidence was 42%, of which 83% contained less than 5.0 ng L^?1 and 17% contained 10.0–20.0 ng L^?1 AFM1. The levels of contamination found justify continuous monitoring for public health and to reduce consumer exposure.     

Use of a Core-Shell Column for the Development of a Green LC Method for Thiol Determination in Fresh Fruits Following Derivatization with Methyl Propiolate

A novel HPLC method has been established for the determination of thiols in fruit samples, introducing, for the first time, methyl propiolate as an advantageous precolumn derivatization reagent for cysteine (CYS), glutathione (GSH), and N-acetylcysteine (NAC). The formed derivatives were detected at 285 nm, following isocratic separation on a core-shell column (Ascentis Express C18, 50?×?2.1 mm i.d., 2.7 μm) with a mobile phase of 15 mmol L^?1 (ΝΗ₄)₂ΗPO₄/H₃PO₄ (pH?=?2.2)/methanol (92:8?v/v), containing 1 mmol L^?1 EDTA, at a flow rate of 0.2 mL min^?1. Derivatization parameters were optimized including pH and concentration of buffering medium, amount concentration of methyl propiolate, derivatization time, and temperature, by the univariate approach. Under optimal conditions, the developed analytical scheme offers a total analysis time of less than 10 min, limits of detection in the range 0.1–0.5 μmol L^?1, and satisfactory linearity up to 100 μmol L^?1 for all analytes. The method proved also to be equally selective and robust. Endogenous thiols were determined in melon, watermelon, and avocado, using the standards addition approach, after minimal sample preparation, with no use of organic solvents. The accuracy was evaluated by recovery experiments resulting in the range of 86.4–118.5 %.     

The nutritional role of free sialic acid,a human milk monosaccharide,and its application as a functional food ingredient

N-Acetyl-d-neuraminic acid (NANA), more commonly known by its trivial name sialic acid, is an endogenous human and ubiquitous nutritional monosaccharide. As a bound sugar at the terminal positions of glycans NANA is known to play important roles in many biological events. The data that exist on the occurrence of the free monosaccharide in breast milk and nutrition, however, are less commonly discussed. In most foods of animal origin, sialic acid occurs as a mixture of NANA and N-glycolyl-d-neuraminic acid (NGNA), a hydroxylated derivative of NANA that is not found in humans. The dietary intake of NGNA has been identified as a risk factor for long-term adverse health effects. Therefore, we present summaries on the biochemistry, metabolism, bioavailability, and the data on NANA and NGNA levels that occur in diverse foods. Finally, we discuss the emerging data demonstrating that free NANA is linked to positive nutritional effects including pronounced antioxidative properties. These data and the extremely high safety profile of NANA justify dietary enrichment at levels that correspond to the dietary intake of NANA in infants through breast milk.     

Large-Volume Sample Staking of Rice Polyphenols Prior to Their Determination by Non-aqueous Capillary Electrophoresis

A rapid non-aqueous capillary electrophoretic (NACE) method for the separation of (?)-epicatechin (EPI), (+)-catechin (?CAT), kaempferol (KAE), quercetin (QUR), naringanin (NAR), ferulic acid (FA), and p-coumaric acid (p-CA) has been developed and applied to the determination of these compounds in different rice varieties. All seven compounds were separated on capillary of 50 μm?×?68 cm (60-cm effective length) using 20 mmol L^?1 borate buffer of pH 9.0 and 5 % acetonitrile in methanol. Large-volume sample stacking (LVSS) technique was optimized and used to preconcentrate non-detectable polyphenols of white polished rice. Rice extracts were concentrated on-line by LVSS prior to separation by non-aqueous capillary electrophoresis. An improvement of 10–55 times in detectability was achieved with injection at 50 mbar for 30 s followed by voltage inversion (?20 kV) for 5 s. Linear calibration range of 1–300 μg L^?1 and 0.01–60 μg L^?1 was observed for NACE and NACE-LVSS method respectively, with the detection limit of 0.33–2.0 and 0.006–0.19 μg L^?1. Good reproducibility with standard deviations of less than 5 % was achieved. Polyphenol contents of different rice varieties were determined using developed method.     

Simultaneous Detection of Azodicarbonamide and the Metabolic Product Semicarbazide in Flour by Capillary Electrophoresis

In the present work, capillary electrophoresis (CE) was used for the first time for the simultaneous analysis of azodicarbonamide (ADA) and semicarbazide (SEM), and the capillary electrophoresis separation conditions, extraction agents, and derivatization conditions were investigated. In 20 mmol L^?1 sodium tetraborate, 30 mmol L^?1 β-cyclodextrin (β-CD), 17 % isopropanol (v/v), and 25 mmol L^?1 sodium dodecyl sulfate (SDS) running buffer, ADA and SEM previously derivatized with 9-fluorenylmethyl chloroformate (FMOC) were separated in less than 25 min with good sensitivity. The linear ranges were 8.3?×?10^?4～6.6?×?10^?2 mmol L^?1 and 1.9?×?10^?3～3.4?×?10^?2 mmol L^?1, and detection limits (S/N?=?10) were 0.5 and 0.15 mg kg^?1 for ADA and SEM, respectively. The proposed method was successfully applied for the simultaneous analysis of ADA and SEM in five flour samples with satisfactory recovery data from 88.0 to 93.0 % for ADA and 98.0 to 106.0 % for SEM, indicating the valuable potential application of this method for food analysis.     

Development of an ELISA and Immunochromatographic Assay for Tetracycline,Oxytetracycline, and Chlortetracycline Residues in Milk and Honey Based on the Class-Specific Monoclonal Antibody

A sensitive class-specific monoclonal antibody against tetracyclines (TCs) was generated and used to develop an enzyme-linked immunosorbent assay (ELISA) and an immunochromatographic assay for TC, oxytetracycline (OTC), and chlortetracycline (CTC) detection in milk and honey samples. The dynamic range of detection for TC in ELISA was 0.26–2.00 μg L^?1 with an IC₅₀ of 0.72 μg L^?1. The IC₅₀ value of OTC and CTC was 3.2 and 6.4 μg L^?1, respectively. The recovery of TC, OTC, and CTC in milk samples was 82–102, 91–105, and 90–101 %, respectively, and 88–101, 89–101, and 89–95 % in honey samples, respectively. In the immunochromatographic assay, the cutoff values for TC, OTC, and CTC were 15, 15, and 50 μg L^?1 in milk, respectively, and 40, 40, and 40 μg L^?1 in honey, respectively. The results revealed that ELISA and the immunochromatographic assay can be applied for the rapid and sensitive detection of TC, OTC, and CTC in milk and honey samples.     

Influence of sulfur fertilization on S-containing, phenolic, and carbohydrate metabolites in rosy garlic (Allium roseum L.): a wild edible species in North Africa

Allium roseum L., a North African endemic species, is a rich source of many important nutrients and bioactive compounds responsible for many promising beneficial health physiological effects. The influence of sulfur fertilization (S fertilization) on the flavor, total polyphenols, and carbohydrates content in A. roseum was studied, using three sulfur concentrations (0.01, 1.50 and 4.50 mmol L^?1) under controlled conditions. S fertilization showed a significant increase in the allicin concentration of A. roseum bulbs with an average of 0.859–2.285 g kg^?1 FW for bulbs grown at 0.01 and 1.50 mmol L^?1 SO₄ ^2?, respectively. The same trend was observed for total polyphenol content. On the contrary, the highest level of S decreased the content of reduced carbohydrates. These results provide evidence that the concentrations of allicin and polyphenols in A. roseum are increased by S fertilization, potentially amplifying its beneficial impacts on health.     

Simultaneous Determination of Nitrate and Nitrite in Fish Products with Improved Sensitivity by Sample Stacking-Capillary Electrophoresis

A fast and reproducible method for the simultaneous determination of nitrate and nitrite ions in canned fish samples by capillary zone electrophoresis has been developed. The sensitivity of the method was increased by applying a sample stacking technique. Optimal separation conditions were selected as 30 mmol L^?1 formic acid and 30 mmol L^?1 sodium sulfate at a pH of 4.0. The separation of nitrate and nitrite ions was achieved within 2.5 min. The limits of detection obtained at a signal-to-noise ratio of 3 for nitrate and nitrite were 0.55 and 0.82 μmol L^?1, while the relative standard deviations of intra-day corrected peak areas were 0.99 and 2.74 %, respectively. Recovery values ranged between 88.7 and 104 % for both ions. The method was successfully applied to canned fish samples, namely tuna, mackerel and sardine.     

Determination of Quercetin, Gallic Acid, Resveratrol, Catechin and Malvidin in Brazilian Wines Elaborated in the Vale do São Francisco Using Liquid–Liquid Extraction Assisted by Ultrasound and GC-MS

In this work, a fast and simple methodology has been applied for the determination of gallic acid, resveratrol, catechin and malvidin in Brazilian wines by gas chromatography–mass spectrometry. The procedure included a stage of ultrasound-assisted liquid–liquid extraction and subsequent derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and GC-MS analysis. The limit of detection varied from 0.41 to 1.18 mg?L^?1 in all the analytes. The relative standard deviations calculated for 8.0 and 20 mg?L^?1 were 1.90 and 0.82 % for gallic acid, 3.08 and 1.22 % for catechin, 1.30 and 0.44 % for malvidin, 1.50 and 0.53 % for resveratrol, and 1.41 and 0.61 % for quercetin. The developed methodology was applied for the analysis of red wine samples collected in the São Francisco region, Bahia state, Brazil. Quercetin concentration varied from 2.4 to 3.0 mg?L^?1, gallic acid 21.4–56.3 mg?L^?1, resveratrol 1.5–5.9 mg?L^?1, malvidin 15.3–32.2 mg?L^?1, and catechin 11.71–18.2 mg?L^?1. The obtained concentrations are in agreement with those reported in the literature.