| In this paper, fresh hami melon was used as the material to study the changes of color, turbid, browning degree in hami melon juice exposed to supercritical carbon dioxide, and to analyze the dynamics of related data. Meanwhile, before and after treatment of SCCO2, the fatty acid, aroma compounds in the hami juice were determined by GC and SPME/GC/MS, respectively; the sugars and organic acids content were determined by HPLC.The total amounts and the key enzymes activity in the Hami melon juice were studied before and after SCCO2 treatment and storage at 4℃. Meanwhile, the flavor and sensory of the melon juice were evaluated by Krame's and indistinct comprehensive evaluation method and the evaluation model was established. The change trends of aroma compounds were investigated. The best parameters for hami juice non-heating treatment were obtained from the results. The main results showed as followed:1.After SCCO2 treatment,the turbid of Hami melon juice slightly increased,the value of L was declined insignificantly (P>0.05), at 35 MPa,65℃, the L declined for 0.54. Adopt class 1 reaction dynamics to analysis the value L and browning (value A) of Hami melon juice during SCCO2 and heating treatment processing. When the SCCO2 treatment at 35Mpa,65℃, the velocity constant KL is 0.27×10-2 and KA is1.75×10-22.The best condition of determine the sugar is:chromatogram columniation:SHIM-PACK CLC-NH2 (M),velocity of flow:1.0mL/min, sample volume:20μL, temperature:40℃, flowage, C2H3N-exceed pure water (75%:25%); the best contidition of determine the organic acid is: chromatogram columniation:SHIMADZU VP-ODS (10μm,4.6 mm i.d.×250 mm), velocity of flow: 0.6 mL/min, sample volume:20μL, examine wavelength:210 nm, temperature:40℃, flowage:3% CH3OH-0.01 moL/LK2HPO4 liquor (pH=2.7,H3PO4 prepare).3.With Kramer method, L9 (33) orthogonal design experiment was used to evaluate and sequence. The results with the SPME-GC-MS detection of online analytical results are generally consistent with the use of SPME-GC-MS method The original juice mainly by ester and green aroma of fresh gas composition, the relative contents of esters and alcohols are larger.Nineteen compounds were found either in the fresh melon juice samples or in the treated samples, such as, ethyl acetate, propyl acetate, ethyl butyrate, hexyl acetate, methyl isobutyrate, ethyl isobutyrate and ethyl 2-methylbutyrate.After SCCO2 melon juice after treatment, (3E,6Z)-3,6-Nonadien-1-ol and (Z)3-Nonen-1-ol content increased clearly, (Z)6-Nonen-1-ol,(Z)6-Nonenal,(Z)3-Nonen-1-ol,(Z)-3-Hexenal,(3E,6Z)-3,6-Nonadien-1-ol have lower aroma threshold, they showed a strong green odor.The linoleic acid content is the highest in hami melon juice after SCCO2-treated. It was 24.96%-32.09%, followed by palmitic acid, arachidonic acid and linolenic acid. linoleic acid and linolenic acid contents in samples are accord with the sensory index and GC-MS analysis of aroma components determination results, linoleic acid and linolenic acid may to be material and the formation of aromatic precursor in hami melon juice.4.The microbe total amount and pH value were changed after SCCO2 treatment and stored at 4℃.In the untreated hami melon juice, the microbe total amount was 5.8×103/mL, it increased with the storage time. It was 5.8×103/mL after 4-week storage. The initial pH value was 6.36, then decreased. It proved that microbial count was restrained when pH got to 5.36. Bacillus bacteria was the dominant microbe. The.amount decreased from 1.87×104 cfu/mL to 1.8×103 cfu/m L. It was determined that the microbe was effectively restrained at 35Mpa.5.Subjective factors were significantly eliminated when the indistinct comprehensive evaluation method applied to the evaluation of sensory quality of food. From the results, the order of the sensory quality was 6#>7#>5#>3#>8#>9#>4#>2#>1#.6.Based on the above analysis, best parameter condition for hami melon juice treated with SCCO2 was pressure:35MP, temperature:45℃, time:45min;pressure:30MP, temperature 65℃, time:15min; A certain extent, the color, turbid, browning degree, nutriment and fragrance of hami melon juice were closer to those of in the original melon juice. SCCO2 treatment can keep well the quality of hami melon juice. |
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