Characteristic Flavor Compounds and Functional Components of Fragrant Rice with Different Flavor Types.

Fragrant rice has various flavor types, mainly the popcorn flavor, corn flavor and lotus root flavor. Chinese fragrant rice from China and Thai fragrant rice from Thailand were analyzed. GC-MS was used to determine the volatile compounds of fragrant rice. It was found that there were 28 identical volatile compounds between Chinese and Thai fragrant rice. The key compounds of different flavor types of fragrant rice were obtained by comparing the common volatile compounds. The key compounds of the popcorn flavor were 2-butyl-2-octenal, 4-methylbenzaldehyde, ethyl 4-(ethyloxy)-2-oxobut-3-enoate and methoxy-phenyl-oxime. The key compounds of the corn flavor were 2,2',5,5'-tetramethyl-1,1'-biphenyl, 1-hexadecanol, 5-ethylcyclopent-1-enecarboxaldehyde and cis-muurola-4(14), 5-diene. By using a combination of GC-MS and GC-O, the flavor spectrogram of fragrant rice was constructed, and the characteristic flavor compounds of each flavor type were identified. It was found that the characteristic flavor compounds of the popcorn flavor were 2-butyl-2-octenal, 2-pentadecanone, 2-acetyl-1-pyrroline, 4-methylbenzaldehyde, 6,10,14-trimethyl-2-pentadecanone, phenol and methoxy-phenyl-oxime. The characteristic flavor compounds of the corn flavor were 1-octen-3-ol, 2-acetyl-1-pyrroline, 3-methylbutyl 2-ethylhexanoate, methylcarbamate, phenol, nonanal and cis-muurola-4(14), 5-diene. The characteristic flavor compounds of the lotus root flavor were 2-acetyl-1-pyrroline, 10-undecenal, 1-nonanol, 1-undecanol, phytol and 6,10,14-trimethyl-2-pentadecanone. The resistant starch content of lotus root flavor rice was relatively high (0.8%). The correlation between flavor volatiles and functional components was analyzed. It was found that the fat acidity of fragrant rice was highly correlated (R = 0.86) with the characteristic flavor compounds, such as 1-octen-3-ol, 2-butyl-2-octenal and 3-methylbutyl-2-ethylhexanoate. The characteristic flavor compounds had an interactive contribution to the production of the different flavor types of fragrant rice.

Dynamic Changes in Volatiles, Soluble Sugars, and Fatty Acids in Glutinous Rice during Cooking.

Cooking is an important process before rice is consumed and constitutes the key process for rice flavor formation. In this paper, dynamic changes in aroma- and sweetness-related compounds were tracked during the entire cooking process (including washing with water, presoaking, and hydrothermal cooking). The volatiles, fatty acids, and soluble sugars in raw rice, washed rice, presoaked rice, and cooked rice were compared. After being washed with water, the total volatiles decreased while aldehydes and unsaturated fatty acids increased. Meanwhile, oligosaccharides decreased and monosaccharides increased. The changes in fatty acids and soluble sugars caused by the presoaking process were similar to those in the water-washing process. However, different changes were observed for volatiles, especially aldehydes and ketone. After hydrothermal cooking, furans, aldehydes, alcohols, and esters increased while hydrocarbons and aromatics decreased. Moreover, all fatty acids increased; among these, oleic acids and linoleic acid increased most. Unlike with washing and presoaking, all soluble sugars except fructose increased after hydrothermal cooking. Principal component analysis showed that cooked rice possessed a volatile profile that was quite different from that of uncooked rice, while washed rice and presoaked rice possessed similar volatile profiles. These results indicated that hydrothermal cooking is the pivotal process for rice flavor formation.

Electronic tongue and electronic nose for food quality and safety.

For the needs of food producers and consumers, electronic tongue and electronic nose play many roles for food quality and safety in food production, food supervision and daily life. The principles and progresses of electronic tongue and electronic nose were elaborated. The core hardware namely electronic tongue sensors and electronic nose sensors, and the core software namely intelligent sensory algorithms were summarized. It was found that the proportion of electronic tongue and electronic nose employed in food quality control and monitoring in production was the highest. Electronic tongue and electronic nose with the prediction accuracy of 80-96 % accounted for a large proportion in the applications of food. The superposition operation of two or more intelligent sensory algorithms has become routine. In addition, the combination of electronic tongue and electronic nose was highlighted. It was resulted that the ability of food category recognition and quality prediction of the combined technology of electronic nose and electronic tongue showed an increase of 8-25 % compared with the single technology. The future challenges and expectations of electronic tongue and electronic nose were discussed.

Development of Certified Reference Materials for the Determination of Apparent Amylose Content in Rice.

Apparent amylose content (AAC) is one of the most important parameters in rice quality evaluation. In this study, four rice reference materials used to test rice AAC were developed. The AAC of rice reference materials were measured by a spectrophotometric method with a defatting procedure, calibrated from potato amylose and waxy rice amylopectin at the absorption wavelengths of 620 and 720 nm. Homogeneity test (n = 20) was judged by F-test based on the mean squares of among and within bottles, and short- and long-term stability monitoring was performed by T-test to check if there was significant degradation at the delivery temperature of under 40 °C (14 days) and at 0-4 °C storage condition (18 months), respectively. After joint evaluation by ten laboratories, Dixion and Cochran statistical analyses were presented. The expanded uncertainties were calculated based on the uncertainty of homogeneity, short- and long-term stability, and inter-laboratory validation containing factor k = 2. It found that the four reference materials were homogenous and stable, and had the AAC (g/100 g, k = 2) of 2.96 ± 1.01, 10.68 ± 0.66, 17.18 ± 1.04, and 16.09 ± 1.29, respectively, at 620 nm, and 1.46 ± 0.49, 10.44 ± 0.56, 16.82 ± 0.75, and 24.33 ± 0.52, respectively, at 720 nm. It was indicated that 720 nm was more suitable for the determination of rice AAC with lower uncertainties. The determinations of the AAC of 11 rice varieties were carried out by two methods, the method without defatting and with calibration from the four rice reference materials and the method with a defatting procedure and calibrating from potato amylose and waxy rice amylopectin. It confirmed that the undefatted rice reference materials could achieve satisfactory results to test the rice samples with the AAC ranging from 1 to 25 g/100 g. It would greatly reduce the time cost and improve testing efficiency and applicability, and provide technical support for the high-quality development of the rice industry.

A visualization and quantification method to evaluate the water-absorbing characteristics of rice.

A visualization and quantification image analysis method is developed to evaluate the water-absorbing characteristics of rice. A projected image of soaked rice was obtained by a scanner in real time, the expansion ratio of the soaked rice in the projected image was calculated with computer software, and the change in the internal structure was analyzed. The results showed that water absorption had a positive correlation with expansion and the cracks occurred in the internal structure of rice could accelerate the water absorption. The maximum expansion ratio of Japonica rice gradually increased with increased milling time, but that of Japonica glutinous rice was not significantly different (P > 0.05). A high soaking temperature shortened the time to reach the maximum expansion ratio and resulted in a lower expansion ratio in the Indica and Indica glutinous rice but had no significant effect (P > 0.05) in the Japonica and Japonica glutinous rice.

Isoelectric focusing on microfluidic paper-based chips.

Isoelectric focusing (IEF), a powerful technique for protein separation and enrichment, was successfully integrated into microfluidic paper-based analytical devices (µPADs) in this work. The µPADs for isoelectric focusing were fabricated by octadecyltrichlorosilane (OTS) silanization and subsequent region-selective plasma treatment. The system of IEF on µPADs could be easily assembled. And a series of conditions of the system were investigated, including the suitable concentration of ampholyte to create good pH gradient, the effect of polyvinylpyrrolidone (PVP) on electroosmotic flow (EOF) suppression, and focusing voltage applied on the paper channel. After optimization, simultaneous separation and enrichment of protein sample containing myoglobin and cytochrome C was successfully demonstrated. Besides, parallel IEF on multichannels were also achieved for the separation of multiple protein samples on one single chip, and their performance was compared with that of the conventional gel-IEF system. The developed IEF on µPADs exhibits appealing features such as low cost, simplicity, and disposability and are believed to have great application potentials.

Effects of different extrusion temperatures on extrusion behavior, phenolic acids, antioxidant activity, anthocyanins and phytosterols of black rice.

Different extrusion temperatures (90, 100, 110, and 120 °C) were used to investigate changes in the expansion ratios, die pressures, phytochemical contents and antioxidant activities of extrusion products of black rice. The results showed that the die pressure significantly decreased with the increasing extrusion temperature, and the expansion ratio reached a peak value at 100 °C. The soluble-free and total phenolic acid contents gradually increased, whereas portions of soluble-free and soluble-conjugated phenolic acids transformed into insoluble-bound phenolic acids. The soluble-free (52.45) and insoluble-bound (73.59 mg GAE/100 g DF) total phenolic contents (TPC) reached peak values at 110 °C. The soluble-conjugated TPC values remained similar. Antioxidant activity occurred at higher levels in the range from 100 °C to 120 °C. The anthocyanin content decreased after extrusion possibly because some anthocyanin remained in the residue after extraction and could not be completely extracted. The content of free sterols increased from 90 °C to 110 °C and decreased at 120 °C. However, the content of bound sterols showed an opposite trend and reached a minimum value at 110 °C.

Separation of selenium species and their sensitive determination in rice samples by ion-pairing reversed-phase liquid chromatography with inductively coupled plasma tandem mass spectrometry.

A highly sensitive method was developed for the simultaneous separation and determination of organic and inorganic selenium species in rice by ion-pairing reversed-phase chromatography combined with inductively coupled plasma tandem mass spectrometry. To achieve a good separation of these species, a comparison between anion-exchange chromatography and ion-pairing reversed-phase chromatography was performed. The results indicated that ion-pairing reversed-phase chromatography was more suitable due to better separation and higher sensitivity for all analytes. In this case, a StableBond C18 column proved to be more robust or to have a better resolution than other C18 columns, when 0.5 mM tetrabutylammonium hydroxide and 10 mM ammonium acetate at pH 5.5 were used as the mobile phase. Moreover, an excellent sensitivity was obtained in terms of interferences by means of tandem mass spectrometry in the hydrogen mode. The detection limits were 0.02-0.12 µg/L, and recoveries of five selenium species were 75-114%, with relative standard deviations ≤ 9.4%. This method was successfully applied to the analysis of rice samples. Compared with previous studies, the proposed method not only gave comparable results when used for measuring selenium-enriched rice, but it can provide greater sensitivity for the detection of low concentrations of selenium species in rice.

Determination of soluble sugar profile in rice.

Soluble sugars in rice are the main components affecting sweetness taste of rice. In this paper, an accurate, precise and rapid method for simultaneous determination of multi soluble sugars in rice by using ion chromatography equipped with pulsed amperometric detector was presented. Pretreatment and parameters of ion chromatography and pulsed amperometric detector were optimized. Regression coefficients (R) of 0.9998, 1.0000, 0.9979, 0.9998 and 0.9998 were obtained for glucose, fructose, sucrose, raffinose and maltose, respectively. The recovery ranges of five sugars were 92.9-112.0% for milled rice matrix. Repeatability and reproducibility of the method were 0.8-9.7% and 1.9-7.6%, respectively. Method LODs of 3.1-34.6µgg-1 were obtained for soluble sugars in milled rice matrix.

Visualized attribute analysis approach for characterization and quantification of rice taste flavor using electronic tongue.

This paper deals with a novel visualized attributive analysis approach for characterization and quantification of rice taste flavor attributes (softness, stickiness, sweetness and aroma) employing a multifrequency large-amplitude pulse voltammetric electronic tongue. Data preprocessing methods including Principal Component Analysis (PCA) and Fast Fourier Transform (FFT) were provided. An attribute characterization graph was represented for visualization of the interactive response in which each attribute responded by specific electrodes and frequencies. The model was trained using signal data from electronic tongue and attribute scores from artificial evaluation. The correlation coefficients for all attributes were over 0.9, resulting in good predictive ability of attributive analysis model preprocessed by FFT. This approach extracted more effective information about linear relationship between electronic tongue and taste flavor attribute. Results indicated that this approach can accurately quantify taste flavor attributes, and can be an efficient tool for data processing in a voltammetric electronic tongue system.

Determination of Apparent Amylose Content in Rice by Using Paper-Based Microfluidic Chips.

Determination of apparent amylose content in rice is a key function for rice research and the rice industry. In this paper, a novel approach with paper-based microfluidic chip is reported to determine apparent amylose content in rice. The conventional color reaction between amylose and iodine was employed. Blue color of amylose-iodine complex generated on-chip was converted to gray and measured with Photoshop after the colored chip was scanned. The method for preparation of the paper chip is described. In situ generation of iodine for on-chip color reaction was designed, and factors influencing color reaction were investigated in detail. Elimination of yellow color interference of excess iodine by exploiting color removal function of Photoshop was presented. Under the optimized conditions, apparent amylose content in rice ranging from 1.5 to 26.4% can be determined, and precision was 6.3%. The analytical results obtained with the developed approach were in good agreement with those with the continuous flow analyzer method.

Fabrication of a polystyrene microfluidic chip coupled to electrospray ionization mass spectrometry for protein analysis.

A highly integrated polystyrene (PS) microfluidic chip coupled to electrospray ionization mass spectrometry for on-chip protein digestion and online analysis was developed. The immobilized enzymatic microreactor for on-chip protein digestion was integrated onto microchip via the novel method of region-selective UV-modification combined with glutaraldehyde-based immobilization. The micro film electric contact for applying high voltage was prepared on chips by using UV-directed electroless plating technique. A micro-tip was machined at the end of main channel, serving as the interface between microchip and mass spectrometric detector. On-chip digestion and online detection of protein was carried out by coupling the microchip with mass spectrometry (MS). The influences of methanol flow rate in side channel on the stability of spray and intensity of signals were investigated systematically. Also the influence of sample flow rate on the performance of immobilized enzymatic reactor were investigated. Stable spray was obtained at the spray voltage of 2.8-3.0kV and the methanol flow rate of 500-700nLmin(-1) with the relative standard deviation (RSD) of total ion current (TIC) less than 10%. The influence of sample flow rate on the performance of immobilized enzymatic reactor was also studied. The sequence coverage of protein identification decreased with the increase of flow rate of the sample solution. A sequence coverage of 96% was obtained with immobilized enzymatic reactor at the sample flow rate of 100nLmin(-1) with the reaction time of 8.4min. It could detect cytochrome c as low as 10µgmL(-1) with the developed system. No obvious decrease in protein digestion efficiency was observed after the chip continuously performed for 4h and stored for 15d.

A microfluidic chip capable of switching W/O droplets to vertical laminar flow for electrochemical detection of droplet contents.

Analysis of droplet contents is a key function involved in droplet-based microfluidic systems. Direct electrochemical detection of droplet contents suffers problems such as relatively poor repeatability, interference of capacitive current and relatively poor detectability. This paper presents a novel hybrid polydimethylsiloxane-glass chip for highly sensitive and reproducible amperometric detection of droplet contents. By wettability-patterning of the channel surface of the hybrid chip, water in oil droplets generated in the upstream part of the central channel can be switched to a two-phase vertical laminar flow (i.e., a continuous oil stream flowing atop a continuous aqueous stream) in the downstream part of the channel. The vertical laminar flow keeps the analyte in the underneath-flowing aqueous stream in direct contact with the sensing electrodes located on the bottom surface of the channel. Therefore, steady-state current signals with high sensitivity (1.2AM(-1)cm(-2) for H2O2), low limit of detection (0.12µM, S/N=2), and good reproducibility (RSD 1.1% at 0.3mM H2O2) were obtained. The methods for patterning of the inner channel surface are presented, and the behaviors of the microchip in flow profile switching and amperometric detection are discussed. The application of the developed microchip to enzyme kinetics study is also demonstrated.

Preparation of hybrid soda-lime/quartz glass chips with wettability-patterned channels for manipulation of flow profiles in droplet-based analytical systems.

Profile switching of two-phase flows is often required in microfluidic systems. Manipulation of flow profiles can be realized by control of local surface energy of micro channel through wettability-patterning of channel surface. This article presents a facile approach for wettability-patterning of the micro channels of glass chips. Commercially available octadecyltrichlorosilane (OTS) was used to hydrophobilize the channels via the formation of OTS self-assembly monolayer (SAM), and a UV-source that mainly emits deep UV-light of 254 and 185 nm was employed to degrade the in-channel formed OTS-SAM. The architecture of soda-lime glass/quartz glass hybrid chip was designed to facilitate the deep UV-light effective degrading the OTS-SAM. The established approach, together with the side-by-side laminar-flow patterning technique, was applied to prepare various finely patterned channel networks for different tasks of flow profile switching. The micro device capable of conducting the profile switch from W/O droplets to two separated continuous phases was demonstrated to perform on-chip quick liquid-liquid extraction for the determination of partition coefficients of pharmaceuticals.

GPC-1 may serve as a predictor of perineural invasion and a prognosticator of survival in pancreatic cancer.

OBJECTIVE: The purpose of this study was to investigate the expression of glial cell derived neurotrophic factor (GDNF), glypican-1 (GPC-1), and matrix metalloproteinase-9 (MMP-9), and their association with clinicopathologic characteristics as well as prognostic significance in pancreatic cancer. METHODS: Immunohistochemical assessment of GDNF, GPC-1, and MMP-9 was performed in 62 cases of surgically resected pancreatic cancer. Perineural invasion in pancreatic cancer was observed by marking nerve fiber with S-100, while 16 normal pancreatic tissues were used as normal control. Correlations of GDNF, GPC-1 and MMP-9 expressions with clinicopathologic parameters were analyzed. A survival analysis was performed to find the prognostic significance. RESULTS: The expressions of GDNF, GPC-1 and MMP-9 in pancreatic cancer tissue were significantly higher than of those in normal pancreatic tissues (41/62 vs. 5/16 for GDNF, 35/62 vs. 2/16 for GPC-1, and 37/62 vs. 3/16 for MMP-9; p<0.01, respectively). The overexpression of GDNF, GPC-1, and MMP-9 in pancreatic cancer tissue was significantly related to the perineural invasion (p<0.05). Although the overexpression of these genes was related to poor survival, GPC-1 had an independent prognostic effect on overall survival. CONCLUSION: GPC-1 is significantly related to the perineural invasion of pancreatic cancer, holding some prognostic significance in patients with pancreatic cancer.

Method for fabrication of paper-based microfluidic devices by alkylsilane self-assembling and UV/O3-patterning.

This work presents a novel and facile method for fabricating paper-based microfluidic devices by means of coupling of hydrophobic silane to paper fibers followed by deep UV-lithography. After filter paper being simply immersed in an octadecyltrichlorosilane (OTS) solution in n-hexane for 5 min, the hydrophilic paper became highly hydrophobic (water contact angle of about 125°) due to the hydrophobic OTS molecules were coupled to paper's cellulose fibers. The hydrophobized paper was then exposed to deep UV-lights through a quartz mask that had the pattern of the to-be-prepared channel network. Thus, the UV-exposed regions turned highly hydrophilic whereas the masked regions remained highly hydrophobic, generating hydrophilic channels, reservoirs and reaction zones that were well-defined by the hydrophobic regions. The resolution for hydrophilic channels was 233 ± 30 µm and that for between-channel hydrophobic barrier was 137 ± 21 µm. Contact angle measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform-infrared (ATR-FT-IR) spectroscopy were employed to characterize the surface chemistry of the OTS-coated and UV/O(3)-treated paper, and the related mechanism was discussed. Colorimetric assays of nitrite are demonstrated with the developed paper-based microfluidic devices.

[Clinical trial on pancreatic duct stones caused by chronic pancreatitis].

OBJECTIVE: To determine the possible mechanism for chronic pancreatitis causing pancreatic duct stones. METHODS: A total of 172 patients with chronic pancreatitis (n=67), pancreatic duct stones (n=62), and pancreatic injury (n=43), admitted to from August 2000 to October 2008, preoperatively diagnosed by endoscopic retrograde cholangiopancreatograpby(ERCP) or computed tomography(CT), and intraoperatively confirmed by exploration and biopsy, were divided into 3 groups. Pancreatic fluid was drawn to test the concentrations of pancreatic stone protein (PSP), lactoferrin (LF) and Ca2+. RESULTS: The chronic pancreatitis (the CP group) presented hard consistency, shrinkage and nodular fibrosis of the pancreas; besides the above symptoms, the pancreatic duct stones (the PS group) presented dilatation of the pancreatic ductal system with various stones; pancreatic injury (the PI group) presented broken pancreas of different grades with fluid or blood. Compared with that of the PI group, PSP concentration of both the PS group and the CP group was elevated (P<0.05), and was more apparent in the CP group. Concentrations of LF and Ca2+ were also elevated (P<0.05), which were more obvious in the PS group. CONCLUSION: Decreased concentrations of PSP and increased concentrations of LF and Ca2+ may play very important roles in chronic pancreatitis causing pancreatic duct stones.