Studies On Aroma Compounds In Papaya(Carica Papaya L.)Juice And Aroma Variation After Thermal Sterilization

Aroma was an important measurement of fruit and fruit products'quality. The aroma of fruits was composed by a variety of volatile compounds. The aroma was always unstable and easily damaged during processing, which leads to reduction of product value. Papaya smelt special and pleasant and had a good prospect for development. The thesis investigated the aroma compounds in sunrise solo papaya, which is widely grown in Hainan province, with HS-SPME/GC-MS, E-nose and GC-O system. The aroma variation after thermal sterilization was analyzed at the same time. The main conclutions were listed below:1. The optimal analysis condition of aroma components in papaya juice was: CAR/DVB/PDMS fiber,5 mL of juice with 1.5g NaCl, extracted at 40? for 20 minutes. A total number of 34 aroma compounds were detected in the papaya juice by GC-MS, using the extraction method of SPME. The contents of alcohols and esters were the highest, which were 69.62% and 10.13%.2.48 kinds of free aroma components were identified in the quantity and qualitative analysis of papaya juice while 33 in glycosidically bound form. In the free aroma compounds alcohols and esters dominated with a total content of 5787.96?g/L; the total content of bound aroma compounds was 1194?g/L. Enzymatic hydrolysis increased the contents of linalool, benzyl isothiocyanate and other aroma constituents; the bound aroma compounds such as benzyl alcohol, phenylethyl alcohol, nonanol, methyl phenylacetate and 6-methyl-5-hepten-2-one, didn't exist in the free aroma compounds.3. Thermal sterilization had significant influence on papaya juice:sensory evaluation results showed that the juice quality reduced greatly after thermal sterilization, the fragrance of pasteurized juice losed seriously, off-flavor was strong; the pH value and titratable acid changed slightly after two kinds of thermal sterilization while the TSS of pasteurized juice fell 2.4°Brix. Vc was destroyed seriously; Free aroma compounds changed greatly after thermal sterilization; UHT sterilization did less damage to the juice than pasteurization; After thermal sterilization, aroma compounds in bound form declined, off-flavour compound a-terpineol increased significantly; Bound benzyl isothiocyanate increased; E-nose analysis and scores of PCA indicated that pasteurized juice smelt great different to the original juice, while the UHT sterilizing could keep papaya fragrance better.4. GC-O analysis could identify the odour-active compounds in papaya well. Improved that linalool, benzyl isothiocyanate, limonene, (E)-linalool oxide (furanoid) have a direct effect on papaya; the off-flavor caused by thermal sterilization was probably correlated with butanoic acid and a-terpineol.