| GB18186-2000 provides that soy sauce is a liquid flavor seasoning and is micro-brewed through soybean or defatted soybean, wheat or bran, salt and water. Soy sauce is originated in China, it is our country ancient people’s invention and it is one of the four major food. It is deeply loved by ancient and modern people. China is the largest soy sauce production and consumer. It may also be found in Japan, South Korea, Thailand, the United States and Europe’s table. Therefore, soy sauce has been loved by the world people.Soy sauce is deeply loved, because it contains very rich nutrients, such as amino acid, vitamin nutrient composition and it has a very special flavor. In addition, soy sauce also has special functions, such as lower blood pressure, the sterilization, antioxidation, antitumor, lower cholesterol, antianaphylaxis and lower hematic fat action. These nutrients and special function in soy sauce shows that it is fit for the requirements of healthy diet. But soy sauce is various and different sources, which causes nutritional quality of soy sauce is very different. So, it is very necessary that nutrition value of soy sauce is evaluated. The main indicators of evaluation of the nutritional value of foods include general nutrition content, composition and content of amino acid and fatty acid and cholesterol content. The amino acids (especially the essential amino acids) and fragrance are very important to the growth and health. Therefore, the analysis of them and quality assessment of soy sauce are very necessary.This article is divided into two parts, the first part is establishment of the detection method about amino acids and aroma components in soy sauce; the second part is quality evaluation of soy sauce. Details are as follows:This study established high performance liquid chromatography mothod with pre-column derivatization with 2,4-Dinitrochlorobenzene and determinated 20 kinds of amino acids in soy sauce. Sample processing conditions, such as diluted reagent, amino acid derivatization temperature, time, acidity and concentration of derivatization reagent were optimized. Amino acids chromatographic separation and detection conditions were also optimized, especially the acidity of mobile phase. Finally, the Kromat Universil C18 column (4.6mm x 250mm, 5μm) was used; eluent A for acetonitrile, eluent B for acetic acid sodium buffer solution (0.03mol/L sodium acetate buffer comprising 0.15% triethylamine) and the acidity of eluent B was adjusted to pH 5.25±0.05 with acetic acid). The column temperature was 43℃; detected wavelength was 360nm, The flow rate was set at 1 mL /min. 10μL was the injection volume. And gradient mobile phase was used for chromatography. The gradient elution program as follows(%A/min):18/0,18/10,29/15,34/25,55/30,60/37,18/39,18/45. 20 amino acids work curves were set up; the correlation coefficient were 0.99216 ~ 0.99900; the recovery was 82.18% ~ 128.12%; Precision RSD was 0.15% ~ 3.57%; the RSD value of the derivatives stability was 1.61% ~ 5.16%; the detection limit was 0.05~1.25μg/mL. It showed that the method was no interference, easy operation, high sensitivity, and can be used for detection of amino acids in soy sauce.The paper also established the aroma compositions detection of soy sauce with HS-SPME/GC-MS method. Soy sauce aroma extraction condition were optimized, such as extraction fibers, extraction temperature, time; soy sauce aroma separation and detection conditions were also optimized, such as desorption time, heating program and the polarity of chromatographic column. At the same time, soy sauce aroma extraction effect was compared with liquid-liquid extraction, atmospheric distillation extraction, vacuum distillation extraction, microwave extraction, ultrasonic extraction and HS–SPME in the study. The results showed that HS–SPME was superior to other extraction methods. The conditions of soy sauce aroma extraction as follows:55℃water conditions with 50/30μm DVB/CAR/PDMS extraction fiber for 30min. Aroma detection conditions : chromatographic column was HP-INNOWAX 30m x 0.25mm x 0.25μm; the carrier for helium, velocity 0.8mL/min; injector 240℃, diversion ratio 5:1; heating program was: 40℃(5min)with 5℃/min rate to 100℃; then with 3℃/min rate to 150℃; then with 5℃/min rate to 200℃(10min). EI energy 70eV, 230℃, full scan, mass range 30~400amu; the quadrupole mass analyzer 150℃, Transmission lines 250℃; NIST 05 mass spectrometry library. The results showed that the method was no interference, easy operation, high sensitivity, and can be used for detection of aroma in soy sauce.The evaluation of nutritional quality of soy sauce contained amino acids and aroma in the research. Amino acids analysis of soy sauce showed that, (1) the 19 kinds of amino acids in soy sauce were detected except Tau. Amino acids in different soy sauces were same types, but different in the contents. And Asp and Glu were more contents than any other of amino acid. (2) soy sauce quality evaluation with standard model WHO/FAO of amino acid showed that the number of essential amino acids in soy sauce were not consistent, and the percentage content was also different. The quality and level of soy sauce were basically consistent. The result of soy sauce quality evaluation of different raw materials was that seafood soy sauce was higher quality than bean soy sauce. (3) principal component analysis of soy sauce amino acid data results showed that three principal components were elected and the cumulative contribution rate was 85.71%. It indicated that most information of original data can be explained by the three principal components. These included Thr、Val、Met、Ile、Leu、Phe、Lys、His、Asp、Gly、Ser、Ala、Pro and GABA. Through this, different kinds of soy sauce were evaluatd for high and low quality. (4) different sources of soy sauce were analyzed by clustering analysis. The results showed that same sources of soy sauce gathered same classe respectively. The soy sauce quality from stall were the worst. This method can distinguished between the quality of soy sauce. (5) Analysis of sapidity amino acids in soy sauce showed that the umami and sweet taste amino acids had large contribution in soy sauce, and the content of Asp and Glu were higher; umami were stronger. (6) Soy sauce were an important source of the first human body essential amino acid- Lys; at the same time, soy sauce contained abundant functional amino acids-GABA.Soy sauce aroma of different classes, different raw materials and different sources were analyzed in the paper, and the results showed that, (1) the aroma of soy sauce contained organic acids, esters, ethanol, phenols, aldehydes, furan , pyrazine, pyridine and other heterocyclic material. They had different contents, but they maked up the special aroma of soy sauce together. (2) the origin and kinds of aromatic matter were analysed in different levels soy sauce. (3) the aroma of different raw material soy sauce analysis showed that they had main aroma compositions and distinguish between soy sauces with characteristics of aroma compositions. The results showed that the tea soy sauce and seafood soy sauce had complex aroma compositions and better fragrance. (4)the aroma of different sources soy sauce were analyzed, and the results showed that the kinds of aroma from stall were less than that from homemade and supermarket, and benzoic acid in soy sauce from stall content was very high. Thus, qualified and the inferior soy sauce can be distinguished through the aroma type and benzoic acid content. |
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