Jie Yu Chen

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.

Determination of the degree of degradation of frying rapeseed oil using fourier-transform infrared spectroscopy combined with partial least-squares regression.

This rapid method for determining the degree of degradation of frying rapeseed oils uses Fourier-transform infrared (FTIR) spectroscopy combined with partial least-squares (PLS) regression. One hundred and fifty-six frying oil samples that degraded to different degrees by frying potatoes were scanned by an FTIR spectrometer using attenuated total reflectance (ATR). PLS regression with full cross validation was used for the prediction of acid value (AV) and total polar compounds (TPC) based on raw, first, and second derivative FTIR spectra (4000–650 cm−1). The precise calibration model based on the second derivative FTIR spectra shows that the coefficients of determination for calibration (R 2) and standard errors of cross validation (SECV) were 0.99 and 0.16 mg KOH/g and 0.98 and 1.17% for AV and TPC, respectively. The accuracy of the calibration model, tested using the validation set, yielded standard errors of prediction (SEP) of 0.16 mg KOH/g and 1.10% for AV and TPC, respectively. Therefore, the degradation of frying oils can be accurately measured using FTIR spectroscopy combined with PLS regression.

Screening for γ-Nonalactone in the Headspace of Freshly Cooked Non-Scented Rice Using SPME/GC-O and SPME/GC-MS

The determination of γ-nonalactone as one of the important odor-active compounds in freshly cooked non-scented rice is reported. It was evaluated by gas chromatography-olfactometry (GC-O) analysis and identified by gas chromatography-mass spectrometry (GC-MS) analysis in the headspace above the freshly cooked non-scented rice samples extracted by using a modified headspace solid-phase microextraction (SPME) method. This component had a mass spectrum with a characteristic ion peak at m/z 85 (100%) and a linear retention index (RI) of 2,023 on a DB Wax column, consistent with those of an authentic sample of γ-nonalactone. The odor characterization of a strong, sweet, coconut-like aroma of this compound was also validated by GC-O comparison with the authentic compound.

Analysis of Carbonyl Value of Frying Oil by Fourier Transform Infrared Spectroscopy

A rapid method for determining the carbonyl value of frying oils has been developed using Fourier-transform infrared (FTIR) spectroscopy and chemometrics. One hundred and fifty-six frying oils with different carbonyl values were collected from an actual potato frying process. FTIR spectra in the range of 4000-650 cm(-1) were scanned with a FTIR spectroscopy apparatus using the attenuated total reflectance (ATR) method. A good calibration model was obtained using the partial least-squares (PLS) regression method with full cross validation for predicting the carbonyl value of frying oils. For the model, the coefficients of determination (R(2)), standard errors of cross validation (SECV) and standard errors of prediction (SEP) were 0.99, 1.87 μmol g(-1) and 1.93 μmol g(-1), respectively. Moreover, standard deviation ratios of reference data in the validation sample set to the SEP were higher than 3. This study shows that the carbonyl value of frying oils can be successfully determined to a high accuracy using FTIR spectroscopy combined with PLS regression.

Flavor Volatiles in Three Rice Cultivars with Low Levels of Digestible Protein During Cooking

ABSTRACT A modified headspace solid-phase microextraction (SPME) method in conjunction with gas chromatography-mass spectrometry (GC-MS) has been used for the analysis of the flavor volatiles in three rice cultivars with low levels of digestible protein during cooking. Altogether, 77 volatile compounds were identified, of which 13 components were not previously reported in rice. A total of 61, 71, and 74 peaks, respectively, were assigned to Shunyou, LGC-katsu, and LGC-soft. Compounds that have been highlighted previously as flavor molecular markers in rice, including indole, vanillin, (E,E)-2,4-decadienal, (E)-2-nonenal, 2-pentylfuran, and 2-methoxy-4-vinylphenol, etc., were on the list of those identified components. Furthermore, similarities and differences of the flavor volatiles among the three rice cultivars were observed. Shunyou was characterized by a relatively higher amount of indole and LGC-katsu had a very high amount of 4-vinylphenol while both rice cultivars displayed an absence of vanillin,...

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.