| Chili peppers (Capsicum frutescens L.) are one of the most important spices, widely cultivated and used all over the world. Chili peppers, with more than 1000 species, are among the largest consumed vegetables in the world during the past several decades. Because chili peppers contain rich nutritional and the functional constituents, development of chili pepper products is not limited to food industry, but expanded to various areas, such as medicine, military, and chemical industry.Capsaicinoids are components that can provide hot sensation and various biological functions. The content of capsaicinoids is of significant importance, and is usually served as quality index of chili pepper and its products. Therefore it is necessary to establish a reliable analysis method for determining capsaicinoids content. Because chili pepper's pungency degree with chili pepper's market selling price and the food processing quality are closely interrelated, on the international, already had the unified standard to reflect pungency degree, such as ISO 3513 (Second edition 1995-05-01)Chillies-Determination of Scoville index. But our country has not some related standard until now, thus stop our country's chili pepper industry from further development. Therefore it is necessary to establish a scientific representation method of pungency degree. This is an important and urgent link too in standardization process of chili pepper and its products.The objectives of this study include: (a) applying HPLC-UV method for the determination of capsaicinoids content of chili peppers and their products, and what methods was used evaluate their pungency; (b) identifying capsaicinoids and related compounds in different species of chili pepper with HPLC-APCI-MS; (c) comparing the Scoville sensory evaluation method with the HPLC-UV for the pungency determination; (d) evaluating the stability of capsaicinoids and pungency as affected by temperature, acid, salt, sugar, monosodium glutamate and oil. The main conclusion were as followed:For HPLC analysis, an Agilent Zorbax SB-C18 colume ( 4.6mm×250mm i.d., 5 urn) was used.The mobile phase consisted of methyl alcohol and water (65:35, v/v). The injection volume was 10μL. All capsaicinoids were monitored at 280 nm at a flow rate of 1 mL/min and 30℃. The returns-ratio of capsaicin and the dihydrocapsaicin in sample was 95.6% and 94.7%, Respectively. The good linearity was obtained in the range of 0.05 mg/L to 150.0 mg/L for both capsaicin and dihydrocapsaicinis. The limit of detection is 100 ng for both capsaicin and dihydrocapsaicinis. The detection limit in sample was 0.75 mg/kg for both capsaicin and dihydrocapsaicinis. Compared with other ways, this method is more rapid, exact, simple and convenient.This study had initially identified 15 capsaicinoids and their derivatives, including three major capsaicinoids such as capsaicin, dihydrocapsaicin and nordihydrocapsaicin, and minor capsaicinoids such as homocapsaicin and homodihydrocapsaicin using HPLC-APCI-MS method. Results indicated that wild chili peppers contains richer capsaicinoids compared to the farm grown chili peppers, and the same variety of chili pepper from different areas contains different type and content of capsaicinoids.Temperature, acid, table salt, sucrose and storage conditions affect the stability of capsaicinoids. Heated processing (>190℃)caused significant lost of capsaicinoids, and excessive heating should be avoided during processing. The stability of capsaicinoids gradually decreased with the increase of acidity or alkalinity. Low salinity has little effect on the capsaicinstable stability, but when the salt concentration is higher than 12%, it caused lost of capsaicinoids. Especially in the chili pepper product, with the lengthening of storage time, the destructive effect of salt enhanced. Therefore, it is unsuitable to add high amount of salt in the chili pepper product if needs to preserve capsaicinoids and spiceness. Capsaicinoids was very stable in oil, and the more content of oil was, the more advantageous it was to capsaicinoids preservation. The orthogonal experimental study result indicated that, in the chili pepper product, the table salt(0%～12%), the citric acid(0%～0.45%), the oil (0%～120%)and the sucrose(0%～6%)four kind of seasonings under the general addition level, does not have no significant difference (P=0.165, 0.567, 0.667, 0.593>0.05) to capsaicinoids stability. The results also indicated that capsaicinoids contents in chili pepper decreased gradually during 9 months of storage, and crushing chili pepper during processing speed up the lost of capsaicinoids. It is beneficial to preserve capsaicinoids under the low temperature condition (0～4℃) .This research proposed the use of DU (or degree) to measure the strength of pungency, since people are used to apply DU to quantify some sensory properties or ingredients, such as sweetness, and alcohol content in liquor. The higher content of capsaicinoids the bigger the DU. 1 DU is defined as 150 Scoville Heat Units (SHU).The strength of pungency of chili peppers determined with the HPLC methods was basically in consistence with the Scoville sensory evaluation. The Scoville sensory evaluation method does not require expensive equipment such as HPLC, but it requires highly trained subjects, and is time-consuming and very costly to conduct this sensory evaluation method.The influence of addition different spices and the cooking oil on the pungency degree is also studied, the test result showed that: the oil(0%～12%),the citric acid(0.1%～0.6%),the sucrose( 1%～6%),quinine sulfate(10 mg/kg～60 mg/kg)] had a significant effect on reduce pungency degree.The table salt (1%～6%) and the monosodium glutamate (0.1%～0.6%) could reduced the pungency degree too, but its effect on reduce was little. In general, the higher addition level of oil and seasonings was, the more reduction of pungency degree was. But the table salt influence does not follow this rule.
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