Recently, a number of consumers have begun to appreciate more natural ingredients and have become less willing to consume monosodium glutamate (MSG) as a seasoning. By measuring stable isotope ratios (δ13C and δ15N) of glutamic acid contained in foodstuffs and MSG used as seasoning, we attempted to distinguish between both using elemental analyzer-isotope-ratio mass spectrometry (EA/IRMS) and gas chromatography/combustion/IRMS (GC/C/IRMS). As a result, seasoning MSG was observed to have a lower δ15N value than glutamic acid in foodstuffs. We statistically analyzed the stable isotope ratio data using canonical discriminant analysis, thereby differentiating seasoning MSG from foodstuff-derived glutamic acid at an accuracy of 96.7%. This method is effective for distinguishing glutamic acid in foodstuffs from seasoning MSG.

Recent growing health awareness is leading to increasingly conscious decisions by consumers regarding the production and traceability of food. Stable isotopic compositions provide useful information for tracing the origin of foodstuffs and processes of food production. Plants exhibit different ratios of stable carbon isotopes (δC) because they utilized different photosynthetic (carbon fixation) pathways and grow in various environments. The origins of glutamic acid in foodstuffs can be differentiated on the basis of these photosynthetic characteristics. Here, we have developed a method to isolate glutamic acid in foodstuffs for determining the δC value by elemental analyzer-isotope-ratio mass spectrometry (EA/IRMS) without unintended isotopic fractionation. Briefly, following acid-hydrolysis, samples were defatted and passed through activated carbon and a cation-exchange column. Then, glutamic acid was isolated using preparative HPLC. This method is applicable to measuring, with a low standard deviation, the δC values of glutamic acid from foodstuffs derived from C3 and C4 plants and marine algae.

New automatic pretreatment equipment FASVED; Food Automatic Analytical Systems for Veterinary Drugs was developed. FASVED consists of ten main units: reagent dispenser, homogenizer, transfer hand, lid opening/closing device, centrifugal separator, pipette, shaker, column purification device, centrifugal evaporator and cooling device, and it is capable of freely combining operations by these units. A validation study was performed on two methods for determination of 178 veterinary drugs in livestock products, swine muscle, egg and shrimp, according to the method validation guideline of the Ministry of Health, Labour and Welfare of Japan. The numbers of analytes that satisfied the criteria of the guideline were 148 in swine muscle, 160 in egg and 151 in shrimp.

We developed a discriminant method based on the stable isotope ratio of carbon and nitrogen (δ13C and δ15N) to evaluate whether monosodium glutamate (MSG) is used in processed food samples. δ13C measurements were performed by elemental analyzer/isotope-ratio mass spectrometry (EA/IRMS) for on glutamic acid isolated from samples at high purity, and δ15N measurements were performed by gas chromatography/combustion/IRMS (GC/C/IRMS) following the purification and derivatization steps. By applying these methods, the δ13C and δ15N values for glutamic acid present in a wide variety of processed foods were obtained. Subsequently, discriminant analysis, which is a statistical analysis method, was performed by using the δ13C and δ15N values from seasoning MSG and glutamic acid from foodstuffs of known origin, and the discriminant function was derived. By substituting the measured δ13C and δ15N values of processed food samples into this discriminant function and classifying samples into two groups, seasoning MSG (the seasoning group) and glutamic acid in foodstuffs (the foodstuff group), we determined whether seasoning MSG had been used in the processed food samples. As a result, the accuracy of distinguishing between the seasoning group and the foodstuff group was very high, i.e., 96.2%, indicating that the proposed method is a highly robust and accurate method for determining whether seasoning MSG has been used in for processed foods.