Shucheng Liu

Physical and chemical analysis of Passiflora seeds and seed oil from China.

The physical and chemical properties of seeds and seed oil from ‘Tainung No. 1’ passion fruit in China have been analyzed in order to evaluate their nutritional value. Proximate analysis shows that the seeds have a high amount of protein (10.8±0.60%) and are rich in oil (23.40±2.50%). The seeds are found to be a good source of minerals. They contain considerable amounts of sodium (2.980±0.002 mg/g), magnesium (1.540±0.001 mg/g), potassium (0.850±0.001 mg/g), and calcium (0.540±0.002 mg/g). The passion fruit seeds contain the 17 amino acids that are found naturally in plant protein (tryptophan is not analyzed). The essential amino acids account for 34% of the 17 amino acids. The amino acid score of passion fruit seeds protein is 74 and the first limiting amino acid is methionine and cystine. The oil extracted by solvent and supercritical dioxide carbon is liquid at room temperature and the color is golden–orange. The specific gravity of the oil is about 0.917. Comparing the chemical properties of the oil extracted by solvent with that by supercritical dioxide carbon, the latter may be suitable as edible oil directly, while the former will be edible after it must be refined to improve on clarity. Fatty acid composition of the seed oil indicates that the oil contains two essential fatty acids (linoleic acid and linolenic acid), but the content of linoleic acid (72.69±0.32%) is by far greater than that of linolenic acid (0.26±0.00%). The present analytical results show the passion fruit seed to be a potentially valuable non-conventional source for high-quality oil.

A simple and sensitive HPLC method based on pre-column fluorescence labelling for multiple classes of plant growth regulator determination in food samples

The determination of trace plant growth regulator (PGR) has received more and more attentions in the field of phytophysiology and food safety. But the simple and sensitive method for simultaneously analysing multiple classes of PGR remains poorly investigated. In this study, a new pre-column fluorescence labelling method using 2-(11H-benzo[a]carbazol-11-yl)-ethyl-4-methylbenzenesulfonate (BCETS) as the labelling reagent has been developed for simultaneous determination of seven PGRs (i.e., indole-3-acetic acid, 3-indolybutyric acid, 3-indolepropionic acid, jasmonic acid, gibberellin A3, 1-naphthylacetic acid and 2-naphthaleneacetic acid) by HPLC with fluorescent detection (FLD). The proposed method offered the LOD of 0.34-0.73 ng/mL for seven PGRs, which were significantly lower than the reported methods. The crude extract without complex pre-treatments and purification was directly labelled by BCETS and analysed by HPLC-FLD, which facilitates the high-throughput sample screening. This method was proven to be inexpensive, simple, selective, sensitive, accurate and reliable for trace PGR determination.

Monitoring the contents of six steroidal and phenolic endocrine disrupting chemicals in chicken, fish and aquaculture pond water samples using pre-column derivatization and dispersive liquid-liquid microextraction with the aid of experimental design methodology.

This research established a sensitive and efficient pre-column derivatization HPLC method based on dispersive liquid-liquid microextraction (DLLME) for the simultaneous determination of six steroidal and phenolic endocrine disrupting chemicals (EDCs). In this study, EDCs were firstly labeled by the derivatization reagent 2-(11H-benzo[a]carbazol-11-yl) ethyl carbonochloridate (BCEC-Cl) and then extracted by DLLME. The response surface methodology was employed to investigate the key parameters of pre-column derivatization and DLLME. Under the optimal conditions, a good linear relationship between the peak area and the concentration of analytes was observed with correlation coefficients of >0.9991. Limits of detection for all EDCs derivatives were achieved within the range of 0.02-0.07 μg L(-1). The proposed method has the advantages of simple operation, low consumption of organic solvent, saving time, low output limit and good selectivity. When applied to several food and water samples analysis, it demonstrated good applicability for the determination of EDCs.

Determination of multiple phytohormones in fruits by high-performance liquid chromatography with fluorescence detection using dispersive liquid–liquid microextraction followed by precolumn fluorescent labeling

Plant hormone determination in food matrices has attracted more and more attention because of their potential risks to human health. However, analytical methods for the analysis of multiple plant hormones remain poorly investigated. In the present study, a convenient, selective, and ultrasensitive high-performance liquid chromatography method for the simultaneous determination of multiple classes of plant hormones has been developed successfully using dispersive liquid-liquid microextraction followed by precolumn fluorescent labeling. Eight plant hormones in fruits including jasmonic acid, 12-oxo-phytodienoic acid, indole-3-acetic acid, 3-indolybutyric acid, 3-indolepropionic acid, gibberellin A3 , 1-naphthylacetic acid, and 2-naphthaleneacetic acid were analyzed by this method. The conditions employed for dispersive liquid-liquid microextraction were optimized systematically. The linearity for all plant hormones was found to be >0.9993 (R(2) values). This method offered low detection limits of 0.19-0.44 ng/mL (at a signal-to-noise ratio of 3), and method accuracies were in the range of 92.32-103.10%. The proposed method was applied to determine plant hormones in five kinds of food samples, and this method can achieve a short analysis time, low threshold levels of detection, and a high specificity for the analysis of targeted plant hormones present at trace level concentrations in complex matrices.

Optimization of microbial inactivation of shrimp by dense phase carbon dioxide

Microbial inactivation of Litopenaeus vannamei by dense phase carbon dioxide (DPCD) treatment was investigated and neural network was used to optimize the process parameters of microbial inactivation. The results showed that DPCD treatment had a remarkable bactericidal effect on microorganism of shrimp. A 3×5×2 three-layer neural network model was established. According to the neural network model, the inactivation effect was enhanced with pressure, temperature and exposure time increasing and temperature was the most important factor affecting microbial inactivation of shrimp. Cooked appearance of shrimp by DPCD treatment was observed and seemed to be more positively acceptable by Chinese diet custom. Therefore, color change of shrimp by DPCD treatment could have a positive effect on quality attributes. Moderate temperature 55 °C with 15 MPa for 26 min treatment time achieved a 3.5-log reduction of total aerobic plate counts (TPC). The parameters combination might be appropriate for shrimp process by DPCD.

Mussel-inspired synthesis of polydopamine-functionalized calcium carbonate as reusable adsorbents for heavy metal ions

A new high-efficiency adsorbent (PDA-CaCO3) is fabricated via simple thermal calcination of ostracean shells and chemical modification with dopamine. The adsorption capacity for Pb(II) and Cd(II) was 336.32 and 175.48 mg g−1, respectively. Importantly, it can be easily regenerated by low-cost reagents, and exhibited a high adsorption capacity after multiple adsorption–desorption cycles.

A GRAPHENE/ENZYME-BASED ELECTROCHEMICAL SENSOR FOR SENSITIVE DETECTION OF ORGANOPHOSPHORUS PESTICIDES

A sensitive and fast sensor for quantitative detection of organophosphorus pesticides (OPs) is obtained using acetylcholinesterase (AChE) biosensor based on graphene oxide (GO)–chitosan (CS) composite film. This new biosensor is prepared via depositing GO–CS composite film on glassy carbon electrode (GCE) and then assembling AChE on the composite film. The GO–CS composite film shows an excellent biocompatibility with AChE and enhances immobilization efficiency of AChE. GO homogeneously disperses in the GO–CS composite films and exhibits excellent electrocatalytic activity to thiocholine oxidation, which is from acetylthiocholine catalyzed by AChE. The results show that the inhibition of carbaryl/trichlorfon on AChE activity is proportional to the concentration of carbaryl/trichlorfon. The detection of linear range for carbaryl is from 10nM to 100nM and the correlation coefficients of 0.993. The detection limit for carbaryl is calculated to be about 2.5nM. In addition, the detection of linear range for trichlorfon is from 10nM to 60nM and the correlation coefficients of 0.994. The detection limit for trichlorfon is calculated to be about 1.2nM. This biosensor provides a new promising tool for trace organophosphorus pesticide detection.

Changes in the myosin secondary structure and shrimp surimi gel strength induced by dense phase carbon dioxide

Dense phase carbon dioxide (DPCD) could induce protein conformation changes. Myosin and shrimp surimi from Litopenaeus vannamei were treated with DPCD at 5-25MPa and 40-60°C for 20min. Myosin secondary structure was investigated by circular dichroism and shrimp surimi gel strength was determined using textural analysis to develop correlations between them. DPCD had a greater effect on secondary structure and gel strength than heating. With increasing pressure and temperature, the α-helix content of DPCD-treated myosin decreased, while the β-sheet, β-turn and random coil contents increased, and the shrimp surimi gel strength increased. The α-helix content was negatively correlated with gel strength, while the β-sheet, β-turn and random coil contents were positively correlated with gel strength. Therefore, when DPCD induced myosin to form a gel, the α-helix of myosin was unfolded and gradually converted to a β-sheet. Such transformations led to protein-protein interactions and cross-linking, which formed a three-dimensional network to enhance the gel strength.

Effects of dense phase carbon dioxide and heat treatment on shrimp (Litopenaeus vannamei) meat qualities

Dense phase carbon dioxide(DPCD) is a promising non-thermal processing technology that affects microorganisms and enzymes through molecular effects of CO2 under pressures below 50MPa and temperature below 60℃. DPCD could affect food physical,nutritional,sensory qualities. In these experiments,compared with fresh shrimp( Litopenaeus vannamei),the effects of dense phase carbon dioxide(DPCD) and heat treatment on the nutrient components,mass loss,pH value,water-holding capacity, texture,protein and flavor components of shrimp meat were investigated. The results were as follows: compared with fresh shrimp,the water and crude fat content of shrimp meat treated by DPCD decreased significantly(P0.05) and the crude protein content of that had no significant change(P0.05),while the crude protein and fat content of shrimp meat treated by heat decreased significantly(P0.05); the mass loss of shrimp meat treated by DPCD was 16.02%±1.90%,but DPCD had no significant effect on pH value of shrimp meat(P 0.05); DPCD and heat treatment could induce shrimp protein denaturation,which caused water holding capacity of shrimp meat decreased significantly(P0.05),from(84.79±5.25)g/100g to(65.18±2.06)g/100g and( 65.58±2.08)g/100g respectively; DPCD treatment has no significant effect on hardness of shrimp meat( P0 05),while heat treatment caused hardness of shrimp meat to increased significantly(P0.05),from(3.48±0.49)N to(7.37±0.76)N; DPCD and heat treatment caused springiness of shrimp meat to decrease significantly(P0.05),from 0.88±0.08 to 0.71±0.03 and 0.78±0.03 respectively; except for betaine,PO3-4 and Cl-,the contents of other taste-active components(free amino acids,ATP related compounds,organic acid,and glycogen etc.) had no significant difference(P0.05) between DPCD treated and fresh shrimp,but heat treatment led to significant loss of shrimp meat taste-active components(P0.05). These results indicated that negative effects of DPCD treatment on shrimp meat qualities were less than those of heat treatment.