Microfluidic Device for Coulometric Detection of Organophosphate Pesticides.

A microdevice for coulometric detection of organophosphate pesticides (OPs) was fabricated based on the measurement of the inhibition of an enzyme, acetylcholinesterase (AChE), by OPs. Thiocholine (TCh) produced in the enzymatic reaction of AChE with acetylthiocholine (ATCh) as a substrate was oxidized on a microelectrode array formed in a main flow channel. Volumes of plugs of necessary solutions were measured using a structure consisting of a row of rhombuses formed in an auxiliary flow channel. The plugs were merged and solution components were mixed at a T-junction formed with the main and auxiliary flow channels. A linear relationship was confirmed between the generated charge and the logarithm of the OP (malathion) concentration in a concentration range between 10(-6) and 10(-3) M with a correlation coefficient of 0.951. The lower limit of detection was 412 nM.

Electrochemical microdevice for on-site determination of rice freshness.

An electrochemical microdevice was fabricated for on-site rapid freshness determination of rice. The activity of peroxidase was used as an indicator for freshness. With hydrogen peroxide and hydroquinone as substrates, the enzymatic reaction of peroxidase produced benzoquinone, which was subsequently reduced on a gold working electrode electrochemically. The progress of the enzymatic reaction could clearly be observed in the change of cyclic voltammograms. Distinct differences were observed in the current change between fresh rice and aged rice, reflecting the remaining activity of peroxide. The current also depended on the time at which rice grains were milled. The result agreed well with those obtained by the conventional fluorometric and guaiacol methods. Comparison of results obtained with different numbers of grains showed that even the measurement with a single grain provided fairly consistent data. Furthermore, the existence of grains of different freshness could be identified using a device with multiple sensing sites.

Temporal changes in occurrence frequency of bowel sounds both in fasting state and after eating.

Food evaluation technology that takes into account the constitutional predisposition and health of an individual's digestive system should aid in the development of value-added foods for patients and people who require health care. Based on the assumption that the degree of bowel activity changes depending on each individual's constitutional predisposition, health, and tolerance of the consumed foods, we investigated bowel sounds as an index of bowel activity. We have developed a method for investigating changes in bowel activity by performing long-term continuous recording of bowel sounds and observing changes in the occurrence frequency of bowel sounds per unit of time. In order to obtain basic data, we made recordings of eight healthy adults. We observed that bowel sounds continued even after the most recently consumed food had been nearly completely digested. In addition, we found that the occurrence frequency of bowel sounds of normal intensity (stethoscope audible) did not synchronize with that of minimal intensity (amplifier audible) in the fasting state. In contrast, the former did synchronize with the latter during digestion.

[Measurement of cooking loss and tenderness of fresh pork using visible/near infrared spectroscopy].

Cooking loss and tenderness are important quality characteristics of fresh pork. To find a rapid, non-destructive and non-contaminated method to measure them, visible/near infrared spectroscopy was proposed for measurement of cooking loss and tenderness of vacuum-packed pork loin. The acquired raw spectra were pretreated by Savisky-Golay smoothing, second derivative and MSC, respectively using the software of Unscrambler 9.6. A total of 104 samples were used in the experiment. The samples were divided into calibration set and validation set. The calibration set was used to set up calibration model and then the model was adopted to predict the samples of validation set. The partial least square regression (PLSR) was used to build calibration model. The results show that the correlation coefficient for cooking loss and shear force are 0.81 and 0.78 respectively. It is feasible and effective that measure cooking loss and shear force of vacuum-packed fresh pork loin using visible/near infrared spectroscopy in interactance mode.

[Detection of fatty acid composition in intramuscular fat of packed pork loin by near infrared spectroscopy].

Near infrared spectroscopy as a new method was proposed for rapid and non-destructive measurement of fatty acid composition in intramuscular fat of packed pork loin. Gas chromatography was used as a reference method for the spectral analysis of fatty acid composition. The fiber optic in interactance mode was adopted to measure the spectra of packed pork loins by low density polythene. The original spectra were pretreated by smoothing and 2nd derivative, and then PLS calibration model was builtby using software of Unscrambler 9.6. A total of eighty two samples were used in the experiment. The samples were divided into calibration set and validation set after removing the outliers. The calibration set was used to set up calibration model and then the model was adopted to predict the samples of validation set. The results show that the correlation coefficient for C14 : 0, C15 : 1, C16 : 0, C16 : 1, C18 : 0, C18 : 1, C18 : 2, C18 : 3, C20 : 1, C20 : 4, SFA, MUFA, PUFA is 0.57, 0.76, 0.71, 0.77, 0.62, 0.81, 0.86, 0.91, 0.85, 0.91, 0.67, 0.81 and 0.95, respectively. It means that evaluating fatty acid using near infrared spectroscopy in interactance mode has higher precision. Near infrared spectroscopy technique is a feasible and rapid method for nondestructive detection of fatty acid composition in intramuscular fat of packed pork loin.

[Prediction of water holding capacity of fresh pork using near infrared spectroscopy].

Water holding capacity (WHC) is an important quality characteristic of fresh pork. It is necessary to determinate it by a rapid and nondestructive method in order to reduce the loss of meat. Near infrared spectroscopy as a new method was proposed for rapid and nondestructive measurement of WHC of vacuum-packed pork loin. Two reference methods for measuring water holding capacity were used to evaluate the water holding capacity, i. e. drip loss and press method. The acquired raw spectra were pretreated by Savisky-Golay smoothing and second derivative, respectively. A total of 106 samples were used in the experiment. The samples were divided into calibration set and validation set. The calibration set was used to set up calibration model and then the model was adopted to predict the samples of validation set. The partial least square regression (PLSR) was used to build calibration model. The results show that the correlation coefficient for drip loss and press method is 0.74-0.79. It shows that evaluating the water holding capacity of vacuum-packed fresh pork loin using near infrared spectroscopy in diffuse reflection mode is better than those results with reflectance or transmission.

Rapid measurement and prediction of bacterial contamination in milk using an oxygen electrode.

An oxygen electrode was used to measure oxygen consumption to determine bacterial contamination in milk. Dissolved oxygen (DO) measured at 10-35 degrees C for 2 hours provided a reasonable prediction efficiency (r > or = 0.90) of the amount of bacteria between 1.9 and 7.3 log (CFU/mL). A temperature-dependent predictive model was developed that has the same prediction accuracy like the normal predictive model. The analysis performed with and without stirring provided the same prediction efficiency, with correlation coefficient of 0.90. The measurement of DO is a simple and rapid method for the determination of bacteria in milk.