Selective determination of thiram residues in fruit and vegetables by hydrophilic interaction LC-MS

Thiram belongs to the most important class of dithiocarbamate (DTC) fungicides including dimethyldithiocarbamates (DMDs), ethylenebis(dithiocarbamtes) (EBDs) and propylenebis(dithiocarbamates) (PBDs). During the surface extraction of fruit and vegetables for the LC-MS determination of residues of DMDs, EBDs and PBDs, thiram is reduced by the penicillamine buffer to the DMD anion, thus resulting in false-positive findings of DMD fungicides like ziram. Therefore, an alkaline sulfite buffer was applied for surface extraction, quantitatively transforming thiram into the DMD anion and a stable DMD–sulfite adduct that was used as a selective marker for thiram. Separation was performed isocratically on a ZIC-pHILIC column with acetonitrile–10 mM ammonium hydroxide solution (85/15). Mass selective detection was carried out on a single-quadrupole mass spectrometer coupled to an electrospray ionisation interface operating in negative mode. Using d₁₂-thiram as the internal standard, recoveries of 80–108% were obtained from apples, tomatoes, grapes and sweet peppers, spiked in the range of 0.02–1 mg kg^?1. Limits of detection and quantification were 0.6 and 2 µg kg^?1, respectively.     

Effect of water activity and temperature on degradation of 5′-inosine monophosphate in a meat model system

The influence of water activity (a_w) (0.7,0.8 and 0.9) and temperature (80° and 120 °C) on the degradation of meat flavor precursor inosine monophosphate (IMP) was studied in a meat fiber model system. Breast and leg muscle from Indian domesticated layer chicken (Gallus gallus) were washed repeatedly with 0.1 mol/l phosphate buffer of pH 6 to obtain pigment free and with minimum content of natural IMP in muscle fiber. The freeze-dried breast and leg meat fiber had a protein content of 86.5±0.48% and 85.6±0.50%, respectively. The IMP contents (mg/100 g) of leg muscle fiber (7.3±0.60) was higher (P?0.05) than in the breast meat fiber (5.1±1.20). The degradation of IMP was temperature-dependent (P?0.05) in both types of meat fiber systems. In the samples of a_w 0.8, the IMP degradation in breast meat fiber system was lower (P?0.05) than in a_w at 0.7 and 0.9 samples, when treated at 80 °C, whereas, there was no significance difference (P>0.05) in the degradation of IMP at a_w 0.7 and 0.9 when heated at 120 °C. The degradation of IMP in leg meat fiber model system at higher a_w (0.9) was more (P?0.05) as compared to lower a_w (0.7 and 0.8) at 80 °C, while the samples treated at 120 °C, the degradation of IMP at a_w 0.8 and 0.9 was more (P?0.05) than at a_w 0.7.     

Creatine and creatinine evolution during the processing of dry-cured ham

Dry-curing of ham involves many biochemical reactions that depend on the processing conditions. The aim of this study was to evaluate the effect of the dry-cured processing on the concentration of creatine, creatinine and the creatinine/creatine ratio. Dry-cured hams under study were salted using three different salt mixtures (100% NaCl; NaCl and KCl at 50% each; and 55% NaCl, 25% KCl, 15% CaCl₂ and 5% MgCl₂) in order to observe its influence on creatinine formation but no significant differences were found between them at any time of processing. However, significant differences between different post-salting times (20, 50 and 80 days) and the ripened hams (7, 9 and 11 months of ripening) were observed. Results showed that creatine and creatinine remain stable once the ripening period is reached. These results were confirmed when analysing dry-cured ham samples submitted to extreme conditions of temperature and time (20, 30, 40 and 70 °C during 0, 20, 40 and 60 min) as well as commercial dry-cured hams with more than 12 months of processing.     

Contents of creatine, creatinine and carnosine in porcine muscles of different metabolic types

Creatine, creatinine and carnosine have been analyzed by hydrophilic interaction chromatography (HILIC) in seven different pork muscles of different metabolic type (Semimembranosus, Biceps femoris, Gluteus maximus, Longissimus dorsi, Gluteus medius, Trapezius and Masseter). As reported in previous literature, carnosine contents are related with the type of metabolism, being higher in those muscles with glycolytic metabolism. Creatine and creatinine also showed significantly higher concentrations in glycolytic muscles such as Semimembranosus, Biceps femoris, Gluteus maximus and Longissimus dorsi. Masseter, a red oxidative muscle, was characterized by the lowest contents of creatine, creatinine and carnosine and, finally, Gluteus medius and Trapezius, both intermediate muscles, had also intermediate contents of these studied compounds. Finally, a correlation between initial content of creatine and creatinine formation after cooking has been verified using pure standards and two different metabolic type muscles, Longissimus dorsi and Masseter, obtaining slightly higher creatinine amounts in Longissimus dorsi, probably due to its higher initial creatine content and its lower pH.     

Relevance of season and nucleotide catabolism on changes in fillet quality during chilled storage of raw Atlantic salmon (Salmo salar L.)

Farmed 5–6 kg Atlantic salmon were pre-rigor filleted, vacuum packed and subsequently analysed after 1, 9 and 13 days of storage at 4 °C. The study was repeated in February, April, August and October. The conversion of hypoxanthine (Hx) showed the highest seasonal variation among the nucleotide metabolites, with an inverse relationship with sea temperature at harvesting (R² = 0.95–0.96). The Hx content was inversely related to fresh odour and flavour (R² = 0.81–0.83), but positively to tenderness (R² = 0.87). Hence, these results suggest that salmon reared in seawater of 11–15 °C (August–October) maintain a superior sensory quality for a longer period post-mortem than salmon reared at 6–8 °C (February–April). The colour intensity increased from days 1 to 9 post-mortem, probably due to rigor contraction. The highest increase in drip loss was observed in October and the lowest in April. It is proposed that seawater temperature significantly influences the storage life of raw salmon, and that Hx is a valuable biomarker for sensory quality.     

Analysis of vitamin B1 in dry-cured sausages by hydrophilic interaction liquid chromatography (HILIC) and diode array detection

A method based on hydrophilic interaction liquid chromatography (HILIC) and diode array detection (DAD) was developed to quantify thiamine (vitamin B1) concentration in Spanish dry-cured sausages (“chorizo,” “fuet,” and “salchichón”). Samples were extracted with diluted acid (HCl 0.1 M) followed by an enzymatic hydrolysis to release vitamin B1 vitamers from food matrix. Crude extracts were purified on a weak cation exchange SPE cartridge and total thiamine concentration was determined by LC-HILIC-DAD with a limit of detection better than 0.01 mg/100 g. The proposed conditions, that do not require the derivatization of the extracts nor the use of fluorescence or MS detectors, are suitable to provide chromatographic separation and identification of vitamin B1 within 8 min. Selectivity, repeatability and accuracy of the method were evaluated with both spiked samples and the reference material Pig Liver BCR^® 487. Quantification of vitamin B1 was also carried out for different kinds of commercial samples of Spanish dry-cured products.     

Synthesis and degradation of adenosine triphosphate in cod (Gadus morhua) at subzero temperatures

This study has demonstrated that the extraction step is very important when analysing ATP and its degradation products. An important factor is whether the sample is fresh, frozen or thawed when homogenised since thawing of the sample will lead to rapid loss of ATP. During frozen storage it was found that ATP in cod (Gadus morhua) was stable at −40 °C in small samples for at least 12 weeks. At −20 °C it was found that ATP content increases initially and thereafter falls. It was demonstrated that degradation of ATP in small samples occurs faster at 0 °C than at −2 and −5 °C. Furthermore, it was found that in whole cod ATP could be synthesised at a significant rate at −7 °C. © 1999 Society of Chemical Industry     

Determination of major phlorotannins in Eisenia bicyclis using hydrophilic interaction chromatography: Seasonal variation and extraction characteristics

In this study, a hydrophilic interaction chromatography (HILIC) condition was developed for the simultaneous determination of five major phlorotannins from an extract of Eisenia bicyclis (Kjellman) Setchell with good linearity (r² > 0.999). Based on this method, the seasonal variations and extraction characteristics, in terms of total extraction yield and the content of the phlorotannins, were investigated under various extraction conditions. In results, the yields and phlorotannins were increased two-to-four times in summer (June–October) and then, were decreased to normal levels in winter (November–March). In the extraction of E. bicyclis, ethanol percentage in water, extraction time and washing time significantly affected the yield of the extract and the phlorotannins, whereas the temperature and the sample/solvent ratio impacted the extraction to a lesser degree. These results will be useful information in the application of this macroalga in the commercial areas related to nutraceuticals, pharmaceuticals, and cosmeceuticals.     

Post-slaughter changes in ATP metabolites,reducing and phosphorylated sugars in chicken meat

The formation of ATP breakdown products in chicken M. pectoralis major post-slaughter is reported. The concentrations of metabolites were followed in chicken breast throughout the carcass processing post-slaughter and during chilled storage. The concentration of glucose remains similar throughout the period whilst that of glucose-6-phosphate decreases linearly. Glucose and glucose-6-phosphate concentrations were inversely related to the pHu of the breast meat throughout chilled storage. Rapid post-mortem glycolysis and high pHu values suggest the occurrence of stress at and pre-slaughter. Whilst ATP, ADP and AMP were rapidly broken down, the concentration of IMP rose rapidly and remained high. Concentrations of inosine, ribose and hypoxanthine increased gradually post-slaughter but an initial increase in ribose phosphate was not sustained. Most of the potential ribose present in chicken meat, believed to be important for flavor formation, remains bound in the form of inosine and IMP. There is evidence that additional breakdown pathways for ribose and ribose-5-phosphate may deplete the concentrations of these precursors.     

加速溶剂萃取结合亲水交互色谱法同时测定油料种子中 多种生育酚及生育三烯酚

该研究建立了一种加速溶剂萃取结合亲水交互作用色谱法同时测定油料种子中4种生育酚及4种生育三烯酚的方法。样品在110 ℃条件下经正己烷萃取180 s后,采用90%正己烷/10%叔丁基甲基醚-四氢呋喃-甲醇（20∶1∶0.1,V/V）流动相体系,经BEH Amide HILIC色谱柱分离,由荧光检测器外标法定量。结果表明,4种生育酚及4种生育三烯酚分别在0.5～80.0 μg/mL、0.5～30.0 μg/mL质量浓度范围内线性关系良好,相关系数R2为0. 995～0.999,检出限为32～70 μg/kg,定量限为96～210 μg/kg,加标回收率为86.3%～99.2%,相对标准偏差（RSD）为2.5%～6.1%。该方法具有操作简单、灵敏度高、回收率和重现性好、结果准确可靠的特点,可以满足油料种子中多种生育酚异构体定性和定量检测的需求。     

Separation of principal component dihydromyricetin from Ampelopsis grossedentata by high-speed counter-current chromatography and its interaction with corn starch

Ampelopsis grossedentata (AG) is an industrial crop in the grape family, which has been used as a dual-purpose plant for medicine and tea with high medicinal values. However, little is reported on the separation technology of active components from AG and processing technology of AG products. High-speed counter-current chromatography (HSCCC) was applied to separate the principal component dihydromyricetin (DMY) from AG. DMY is added to starch-based products to improve food quality. The interaction between corn starch (CS) and DMY was investigated to predict and control the structure and function of starch-based foods. Results show that DMY with 97.13% purity was successfully obtained by HSCCC using a solvent system composed of light petroleum–ethyl acetate–methanol–water–trichloroacetic acid (1:3:1:3:0.01, v/v/v/v/v). Fourier-transform infrared spectroscopy (FT–IR) exhibits that the interactions between CS and DMY included hydrogen bond and noncovalent bond. X-ray diffraction (XRD) shows that DMY could increase the relative crystallinity of CS. Low-field nuclear magnetic resonance results (LF–NMR) imply that DMY decreased the spin relaxation time (T₂) and inhibited the mobility of free water. Atomic force microscopy (AFM) results suggest that DMY changed the surface morphology of CS through hydrogen bond interaction. Moreover, the results of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) indicate that DMY could enlarge the pores and change the microstructure of CS–DMY complexes. The findings promote the development of industrial CS-based products and utilization of corn crop.     

Comparison of matrix solid-phase dispersion and liquid-liquid extraction for the chromatographic determination of fenthion and its metabolites in olives and olive oils

Matrix solid-phase dispersion (MSPD) methodology has been developed to extract fenthion and its metabolites from olives and olive oils, and the technique compared with conventional liquid-liquid extraction (LLE). The method was applied to olives and olive oil samples obtained from olive groves treated with fenthion. Pesticide residues were analysed by gas chromatography (GC) using a nitrogen-phosphorus detector. Both extraction methods gave a linear response over the concentration range assayed (0.03-1 mg kg^-1 for MSPD and 0.1-1 mg kg^-1 for LLE). Recoveries and RSD (n = 6) values in olives were 85-112% and 2-6% for MSPD, and 68-108% and 4-16% for LLE, respectively. In the case of olive oil, recoveries and RSD (n = 6) values were 67-98% and 5-11% for MSPD, and 63-115% and 6-14% for LLE, respectively. When compared to LLE, the newly developed MSPD method was twice as sensitive and required 10 times less sample weight.     

Liquid chromatographic determination of free and total sulphites in fresh sausages

The present work describes a method for the determination of free and total sulphite in fresh sausages and its implementation on 48 samples. The method includes the extraction of sulphite, both free and total, by dissolution of the sample in a suitable solvent and determination by high performance liquid chromatography with electrochemical detection. The method is that previously reported by Kim and Kim (J Food Sci 51 1986 1360–1361) improved by certain modifications the principal of which consists of working atpH 10 for the extraction of total sulphite. Use of this pH permits reversible dissociation of the combined sulphite. In reproducibility assays carried out on sausages, variation coefficients of 3.3 and 5% were obtained for free and total sulphite, respectively. To evaluate recovery, sulphite was added to the samples as hydroxymethylsulphonate. Mean recovery was 86.4% with a variation coefficient of 3.8%. In 62% of the sausages analysed, amounts of total sulphites higher than 450 μ SO₂ g^?1 were found. Among the samples, considerable variation was observed in the distribution of sulphite between the free and combined forms.     

Optimisation of a chromatographic procedure for determining biogenic amine concentrations in meat and meat products employing a cation-exchange column with a post-column system

The aim of this study was to optimise and validate a chromatographic method for determining biogenic amine (BA) in meat and meat products separated by a cation-exchange column with a post-column system, using o-phthalaldehyde as a derivatising reagent. A perfect separation of nine BA (tyramine, histamine, β-phenylethylamine, putrescine, cadaverine, tryptamine, agmatine, spermidine and spermine) was obtained in 22 min. The conditions were: column Tª 40 °C and coil Tª 45 °C, pump flow rate 0.8 mL/min, pH phase A 6.33, B 5.63 and C 13.00. The method was adjusted linearly in a range of 0.10–12 mg/L with a correlation coefficient superior to 0.998. Detection and quantification limits were between 0.03–0.10 mg/L and 0.10–0.20 mg/L, respectively. Precision studies were satisfactory, with RSD less than 2% and meat extracts recovering over 98%. This method showed an appropriate, precise, fast and versatile procedure for determining nine BA simultaneously in different meat product matrices.     

The effect of interaction between genotype CAST/RsaI (calpastatin) and MYOG/MspI (myogenin) on carcass and meat quality in pigs free of RYR1(T) allele

The purpose of the studies was to demonstrate to what degree genotypes of calpastatin (CAST/RsaI) and myogenin (MYOG) genes as well as the interaction between them may affect the carcass and meat quality of pigs. The investigations were conducted on 397 stress resistant pigs (free of RYR1^T allele). It was demonstrated that the favourable effect of the variants of CAST and MYOG genes on carcass quality traits depends on the cut. The gene variant favourably affecting the weight of ham simultaneously had a negative effect on the weight of the loin. It was also shown that the interaction between CAST and MYOG genotypes has a significant effect on backfat thickness. The effect of a given combination of CAST and MYOG genotypes on carcass traits is related to the weight of a substantial cut (ham, loin).Genotypes at loci CAST/RsaI and MYOG have a significant effect on the value of certain traits and parameters of meat quality and its technological value (genotype CAST on pH at 35 min and 2, 3, 24, 48, 96, 144 h post-mortem (pH₃₅, pH₂, pH₃, pH₂₄, pH₄₈, pH₉₆, pH₁₄₄, respectively), R₁ (IMP/ATP), electrical conductivity at 3 and 4 h post-mortem (EC₃, EC₄), technological yield of meat in curing and thermal processing (TY) and protein content in the muscle tissue, while genotype MYOG on pH₄₈, EC₃₅, EC₃, EC₂₄ and dry matter content).     

亲水色谱柱对氨基酸及其美拉德反应初始中间体的分离

采用Xbridge BEH Amide和Atlantis HILIC Silica两亲水色谱柱分离半胱氨酸、甘氨酸及其与木糖形成的美拉德反应初始中间体2-木糖基噻唑烷-4-羧酸、甘氨酸-Amadori和半胱氨酸-Amadori 5 个化合物。通过研究流动相中有机相（乙腈）的比例、缓冲盐浓度、pH值、柱温、流速对容量因子和分离度的影响,分别找到较佳分离条件。在BEH Amide色谱柱上5 个化合物之间的分离度均达到2.28以上,对比可知,采用BEH Amide色谱柱更好。     

Micellar liquid chromatographic determination of arbutin and hydroquinone in medicinal plant extracts and commercial cosmetic products

A simple micellar liquid chromatographic (MLC) procedure for simultaneous determination of arbutin and hydroquinone in medicinal plant extracts and commercial cosmetic products was proposed. This method was developed and validated. The chromatographic conditions were also optimized. All analyses were performed at room temperature in an isocratic mode, using a mixture of 1% (v/v) acetonitrile and 0.006 mol L^?1 Brij 35 (pH 6.0) as a mobile phase. The flow rate was set at 1.0 mL min^?1. The analytical column was a 150 × 3.9 mm Nova‐Pak C‐18 column. The effluent from the analytical column was monitored by UV detection at 280 nm. Under the optimum conditions, arbutin and hydroquinone could be determined within a concentration range of 2–50 μg mL^?1 of arbutin, and hydroquinone was obtained with the regression equations; y = 0.045x + 0.042 (r² = 0.9923) and y = 0.091x + 0.050 (r² = 0.9930) respectively. The limits of detection were found to be 0.51 μg mL^?1 and 0.37 μg mL^?1 for arbutin and hydroquinone respectively. The proposed MLC method was applied for the determination of arbutin and hydroquinone contents in medicinal plant extracts and commercial cosmetic products. This proposed MLC method is thus suitable for routine analysis of arbutin and hydroquinone in the pharmaceutical formulations, cosmetic products and raw medicinal plant extracts.