Innovation Of Processing Technology Of Wintersweet-Scented Tea And Study On Scenting Mechanism

The key processing procedures for wintersweet-scented tea (WST) were studied in this paper. The suitable cultivars for WST production were identified, the processing technology system was established, the scenting mechanism was also preliminary studied. The main results were summarized below.Volatile compounds emitted from flowers of four cultivars of Chimonanthus praecox (L.) Link (SX, QZ1,QZ2,and HX) and at different stage were investigated using headspace solid-phase micoextraction in combination with gas chromatography-mass spectrometry (HS-SPME-GC-MS).The main compounds in the cultivars were ocimene, alloocimene, benzyl acetate, methyl salicylate, which accounted for over 80% of the total volatile compounds. The ratio of terpenoids to esters decreased with the increase in the number of purple whorls in the inner petals of flowers. The relative contents of esters were significantly higher than that of terpenoids in the flowers of the cultivar HX, and as a result, the aroma of HX was pungent and lacked leisurely long fragrance. The number of volatile compounds underwent slight change from buds stage to blooming stage, and the similarity rate of flavor pattern between buds stage and blooming stage was over 0.990, and so it showed that the flavor pattern did not significantly change during flowering process, which was not same as the releasing process of flavor compounds in Jasmine flowers.The volatile compounds in the flower essence were also investigated by simultaneous distilled extraction in combination with gas chromatography-mass spectrometry (SDE-GC-MS). Results showed that the number and the relative content of terpenoids in wintersweet flowers were significantly more than that of esters and alcohols. All these results suggested that cultivars with fewer purple whorls of inner petals could be used for wintersweet-scented tea production, especially flowers at full blossom.The characteristics of tea dhools, scenting technologies, primarily scenting techniques, and changes of quality during processing of WST were studied using organoleptic evaluation, color analyzing, chemistry analyzing, and simultaneous distilled extraction in combination with gas chromatography-mass spectrometry (SDE-GC-MS). Results were shown as follows:The green tea dried by hot air baking was the most suitable dhool for WST, and the second was baking and roasting combined green tea, and the roasting green tea was not recommended to be used as dhool for WST production. The score of aroma and total score increased with the strengthening of rolling degree, but the values of color and contents of chlorophyll significantly declined(P<0.05).Therefore, in order to improve aroma quality, it was best to select dhools that fairly intensively rolled in producing of WST. Results of tenderness experiments showed that the total score of WST scented with one-bud-one leaf dhools was slightly higher than that of pure buds dhools and one-bud-two leaves dhools, but not significantly. So it was better to select one-bud-one leaf and one-bud-two leaves dhool for WST production, and the pure buds dhools was not recommended since that could result in wasting of tea resources.The score of aroma, taste and total score of WST samples produced by separately scented method were significantly lower than that by contiguously scented method. The organoleptic quality and contents of main chemistry compounds were not significantly different between WST samples produced by continuously and discontinuously scented methods. The contiguously and continuously scented method could be chosen for production of WST.If the ratio of weight of F flowers to tea dhools (RFT) was over 3% during primarily scenting, the fragrance of F flowers would cover the wintersweet aroma of WST, coursing an aroma deficiency which was called’appearing fragrance of F flowers’.The appropriate RFT was 0.5%-1.5%, and the primarily scenting procedure could be omitted when the conditions were absent during the production of WST.When scented time was less than 16h, the score of aroma and total score of WST samples were lower than that of samples with scented time more than 16h, and the organoleptic score of WST samples with scented time between 24h-40h were higher than that of other samples. The score of aroma, taste and total score of WST was raised with the increase of scenting times, but it increased slowly after scented for three times, and the score of appearance and color decreased, so the optimal scenting time was 2-3.When the water contents of tea dhools were 5%-25%,the organoleptic quality and contents of main chemistry components were not significantly different, which meant that there was a wide tolerance in water contents of tea dhools during scenting process of WST.With the increase of the ratio of weight of wintersweet flowers to tea dhools (RWT), the score of aroma and taste increased, but that of appearance, drying tea color and liquor color declined. However, the total score did not significantly change when the RWT increased from 45% to 105%.The total score decreased when the scented temperature was over 30℃,and the score of organoleptic qualities of WST samples were relatively higher when scented temperature was 15℃-25℃,but the difference was not significant.The parameters of scented time, RWT, scented temperature and water contents of dhools were optimized using an orthogonal experimental design L27 (313).Results indicated that the optimal parameters were:scented time about 20h, RWT 30%-50%, scented temperature around 15℃,and water contents of dhools 5%-25%.The influences of the RWT ratio of every scenting procedure on the qualities of WST were not significant when total RWT kept unchanged. The parameters of scenting time and total RWT were optimized using an orthogonal experimental design L9 (3).Results showed that the ideal scenting time was 2 times, and the optimal total RWT was about 80%. The RWT ratio of the first scenting to second was optional, and 5:3 was recommended.The drying technique and raising fragrance technique were studied. Results showed that the optimal drying parameters in a hot air drier were:temperature was 75℃-85℃, drying time 30min-45min, and the RWT of raising fragrance was 2%.Quality changes of WST during processing were investigated. Organoleptic quality and color were analyzed, and results showed that the appearance and color deteriorated after thirdly scenting, but the score of aroma and total score were not significantly different between WST samples scented two times and three times, and the total score of WST after raising fragrance procedure was more than that of WST scented three times. The Ha*b* value of thirdly scented tea significantly decreased after thirdly scenting (P<0.05).Volatile compounds were detected using SDE-GC-MS.Results indicated that the main flavor compounds of WST were benzyl acetate,2-aminobenzoate-3,7-dimethyl-1,6-Octadien-3-ol, methyl salicylate, benzyl alcohol, linalool, alloocimene, naphthalene, a-ionone. The relative contents of esters and alcohols in secondly scented tea were significantly the highest among samples (P<0.01),and that of ketones did not significantly change during processing, and that of terpenoids in raising fragrance tea were significantly more than that in other samples (P<0.05). The values of flavor pattern similarity between dhool and other procedures were lower than that between firstly, secondly, thirdly scented, and raising fragrance procedures.Main chemistry components were analyzed. Results indicated that the contents of polyphenols and chlorophyll in thirdly scented tea significantly decreased compared to that of dhool (P<0.05),but that of soluble sugar significantly increased after secondly scenting (P<0.05), and that of amino acids did not significantly change.Influences of dhools extracted by different solvents (CK, the dhool was not extracted; NEW, the dhool was extracted by water; NAE, the dhool was extracted by aether; NWAE, the dhool was extracted by water and aether) and particle size of dhools on the quality of WST were studied by organoleptic appreciation, chemistry analysis and SDE-GC-MS. Results of extraction experiments showed that the total score of CK was the highest and that of NWAE the lowest, NAE was higher than that of NEW. The SDE-GC-MS results showed that the main flavor compounds in the four samples were benzyl alcohol,3, 7-dimethyl-1,6-octadien-3-ol-2-aminobenzoate, benzyl acetate, eugenol, methyl salicylate, acetic acid cinnamyl ester, the relative content of which in NWAE was the highest among samples, followed by CK, NAE and NWE, The mainly reason that the relative content in NWAE was highest was caused by the extraction procedures. The adsorption capacity in dhool was promoted by the structural change of dhool and the increase of the pore volume and surface area. As a result, physical adsorption was the main adsorption type during WST scenting. Results in particle size experiments indicated that the score of aroma decreased with lessening in the dhool particle diameter, and the quality of WST deteriorated when the dhool particle diameter was less than 0.71mm, so the dhool with less than 0.71mm diameter could not be used for production of WST.