Ryuji Matsunaga

Flavor Volatiles of Rice During Cooking Analyzed by Modified Headspace SPME/GC-MS

ABSTRACT The flavor volatiles in three Japanese rice cultivars, Nihonbare, Koshihikari, and Akitakomachi, during cooking were directly extracted by using a modified headspace solid-phase microextraction (SPME) method and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 46 components were identified, including aldehydes, ketones, alcohols, and heterocyclic compounds, as well as fatty acids and esters, phenolic compounds, hydrocarbons, etc. The amount of key odorant compounds increased with cooking, while the amount of low-boiling volatiles decreased. The similarities and differences of the three rice cultivars were determined through a comparison of their volatile components. Nihonbare was characterized by a higher amount of indole but an absence of the chemical class of fatty acid esters. In contrast, both Koshihikari and Akitakomachi had a higher amount of 4-vinylphenol and an abundance of those esters. Koshihikari and Akitakomachi were quite similar in regard to those flavor volatile...

Direct Extraction of Volatiles of Rice During Cooking Using Solid-Phase Microextraction

ABSTRACT An apparatus that allows extraction and enrichment of flavor volatiles of rice during cooking using solid-phase microextraction (SPME) was designed and tested in the Japanese rice cultivar Akitakomachi. Because it is a solvent-free technique, no solvent contaminants were extracted during sampling. This technique enables one to place the fiber of SPME in the effluent of the flavor volatiles of the rice during cooking and it can also be used for simultaneous extraction of those volatiles in the course of the cooking process. Therefore, variations in the composition and amount of volatile compounds of rice during cooking can be determined. The overall flavor volatiles of rice during cooking have been analyzed by using this SPME method. Compounds that have been previously highlighted as flavor volatile markers, such as volatiles from oxidative degradation of lipids, products from thermal decomposition, and fatty acids existing in rice, were extracted directly by SPME in conjunction with this apparatus.

Non-Destructive Determination of Carbohydrate Content in Potatoes Using near Infrared Spectroscopy

The performance of near infrared spectroscopy as a simple technique for the non-destructive determination of carbohydrate content in potatoes was examined. An interactance method was adopted to measure near infrared spectra (700–1100 nm). A good calibration model with reasonable accuracy (correlation coefficient of 0.93 and standard error of prediction of 0.98%) was developed using partial least square (PLS) regression. The PLS calibration model utilised effectively two characteristic absorption bands of 990 nm and 916 nm, assigned to potato starch. The plots of the regression coefficients were thought to be useful for understanding the calibration model structure.

Main Inorganic Component Measurement of Seawater Using Near-Infrared Spectroscopy

The potential of near-infrared (NIR) spectroscopy to measure the main inorganic components of seawater as salt-manufacturing materials was investigated. A total of 72 seawater samples collected from six locations was used, and spectra (1100–1800 nm) were acquired by a NIR spectrophotometer with a 1-mm path length. Principal component analysis (PCA), canonical correlation analysis (CCA), and partial least-squares (PLS) regression were performed based on the reference inorganic components. As a result, the principal component analysis and canonical correlation analysis showed that the near-infrared spectra could be related to the inorganic components of seawater. The partial least-squares regression analysis showed that the inorganic components (ion concentration of Cl−, Na+, K+, SO42−, and Ca2+) could be predicted with good accuracy using NIR spectra and their second derivatives. For Cl− ion and K+ ion concentrations, the accuracy was high.

Thermal Properties and Inorganic Composition of silk Fiber

The thermal properties of Bombyx mori silk fibers subjected to heat-treatment were examined by thermogravimetry-differential thermal analysis-Fourier transform infrared absorption spectrometry (TG-DTA-FTIR). Only 1% of the original silk fiber weight remains as cocoon ash after treatment at 550 °C. Inorganic components, such as calcium, potassium, sulfur, magnesium etc., were detected in the cocoon ash by energy dispersion fluorescent X-ray spectrometry. A sharp decrease in weight was observed in the TG data to begin around 280 °C, and an endothermic peak appears at 308 °C as evidenced by DTA curves. The IR bands observed at 2380 cm-1, 1760 cm-1, 1503, 1085 cm-1 and 965 cm-1 become stronger as an exothermic reaction beginning at 280 °C takes place. This is probably due to cleavage of the main chain and the accompanying decomposition of the silk fibers.

Component measurement of seawater as salt-manufacturing materials using near infrared spectroscopy

A potential of near infrared spectroscopy to measure inorganic components of seawater as salt-manufacturing materials was investigated. A total of 72 seawater samples collected from six spots were used and spectra (1100-1800nm) were acquired by a NIRSystem 6500 spectrophotometer with 1-mm sample thickness. Principal component analysis (PCA) and partial least squares (PLS) regression were performed. As results, the principal component analysis showed that the near infrared spectra could be related to the inorganic component of seawater. And partial least squares regression analysis showed that the inorganic components (ion concentration of Cl, Na, K, SO4 and Ca) could be predicted in good accuracy using original near infrared spectra or second derivative spectra. Especially, the high measurement accuracy was provided for Cl-ion and K-ion concentration.