‘东魁’杨梅鲜果与干果的风味比较分析

Flavour differences between fresh and dried fruit of Myrica rubra‘Dongkui'

【目的】分析杨梅干制后甜、酸、鲜、香等风味与杨梅鲜果差异性。【方法】以‘东魁’杨梅为试材,分别测定了鲜果与干果中糖、有机酸、氨基酸和挥发性香气成分,并对各成分种类和含量进行了比较分析。【结果】干果中还原糖占总糖的比例比鲜果有所升高。鲜果与干果中柠檬酸含量最高,均占有机酸含量的56%,有机酸主要有柠檬酸、琥珀酸、苹果酸、乳酸、草酸和酒石酸等6种。鲜果与干果中均含有苏氨酸、缬氨酸、蛋氨酸、异亮氨酸、亮氨酸、苯丙氨酸和赖氨酸等7种必需氨基酸,而非必需氨基酸分别为8种和9种,酪氨酸因含量低在鲜果中未测出。经GC-MS技术分析,分别鉴定鲜果与干果中挥发性香味成分44和48种,主要由萜类(包括萜烯、萜醇和萜醚)、醇类、酮类、酯类和酸类等成分组成,萜类在鲜果中占挥发性香味成分的90%,是杨梅鲜果的重要特征香气,在干果中萜类仅占48%。醛类物质是干果中特有的微量成分。【结论】干果中糖、有机酸和氨基酸等营养兼风味成分的含量均高于鲜果,基本呈浓缩效应,而挥发性香气成分的种类和含量在鲜果与干果中差异显著。

[Objective] Nutrition and flavor components play an important role in the quality and market- ing of the fresh fruit and processed products. In order to investigate the flavour differences between fresh and dried fruit of bayberry （Myrica rubra ＇ Dongkui＇） and to develop its deep-processing products, the re- lated components of sugar, acidity and fragrance in the fresh and dried fruit were determined. The possi- ble reasons for the composition changes between the fresh and dried fruit were analyzed, and the nutri- tional value of bayberry＇ s dried fruit was evaluated comprehensively. [Methods] The total sugar, reduc- ing sugar and sucrose of the fresh and dried fruit of bayberry were measured by phenol-sulfuric acid meth- od, film Reagent and the first method of GB/T5009.8-2008 respectively. The organic acid standards （Sig- ma）, including oxalic acid, tartaric acid, malic acid, lactic acid, succinic acid and citric acid, were pre- pared in ultrapure water at concentrations from 0.01 to 1.0 g·L^-1. The conditions of HPLC were as follows： Varian C18 column （150 mm^4.6 mm）, mobile phase contained 0.5% KH2PO4, the wavelength of the ul-traviolet detector 210 nm, and injection volume 20 μL . The fresh and dried bayberry samples were ground with 10 mL ultrapure water, then centrifuged （8 000 r. rain-~, 10 min） and supernatant fluid was fixed to 25 mL, respectively, The solutions were analyzed directly by using HPLC. The fresh and dried bayberry samples were ground and homogenized with 5 mL HC1, and then fixed to 25 mL, respectively. After 24 h hydrolysis in vacuo at 110 ℃, sample was cooled, filtered, vacuum dried, and diluted by pH 2.2 citrate buffer, amino acid composition was determined on amino acid analyzer （SYKAM S-433D）. The volatile components of bayberry＇ s fresh and dried fruit were extracted by steam distillation at 150 ℃, and 400 mL fraction solution was received after 2 hours steam distillation. The fraction solution was ex- tracted by 5 mL petroleum ether （HPLC grade） twice, the volatile flavor components of extraction were de- termined by gas chromatography-mass spectrometry （GC-MS）. The gas chromatography conditions were as follows： Chromatographic separations on a TG-5MS column （30 m×0.25 mm×0.25 m） , carrier gas Helium at 1.0 mL·min-1 in the constant flow mode. The injector temperature was 250 ℃, transfer line temperature was 280 ℃ ; injection volume was 0.5 μL. The oven temperature program was as follow： ini- tial 50 ℃ for 5 min, raised to 250 ℃ at 8 ℃. min-1 and held for 30 min. The ion-trap manifold tempera- ture was 280 ℃, the ion energy for electron impact （EI） was set at 70 eV, scan range 50-500 amu. Identi- fication of the volatile compounds was achieved by comparing the GC retention time and mass spectra NIST08 standard library. [Results] The contents of total sugar, reducing sugar and sucrose in the dried fruit were concentrated Compared to that in fresh fruit, and the ratio of reducing sugar to total sugar in dried fruit increased with the decrease of sucrose proportion. Based on the peak area and the concentra- tion of each organic acid, the organic acid standard curves were plotted. Regression equations and correla- tive indices were shown as Oxalic acid （γ=5×106x＋ 196 096, R2=0.998 5）, Tartaric acid （y=106x＋46 424, R2=0.994 7）, Malic acid （y=481 015x＋14 637, R2=0.998 2）, Lactate （γ=287 663x-19 368, R2=0.991 9）, Citric acid （γ=579 378x＋6 853.5, R2=0.998 5） and Succinate （γ=6×105x＋ 1 669.0, R2=0.997 0）. Concen- trations of organic acids were positively correlated with peak areas in their chromatograms of HPLC. Five organic acids （including citric acid, malic acid, lactic acid, oxalic acid and tartaric acid） were detected in dried fruit, while less of an organic acid in fresh fruit, due to very low levels of tartaric acid. The con- tents of citric acid was the highest, accounting for 56 percent of organic acids in both fruits. Non-volatile organic acids were the main components providing the sour taste. Seven essential amino acids, including threonine, valerian leucine, methionine, isoleucine, leucine and phenylalanine, were discovered in fresh fruit （1.2 mg＂ g-＇） and dried fruit （6.8 mg. g-l）, which accounted 29.4% and 27.2% of the total amino acid content, respectively. And there were 8 kinds （2.89 mg＂ g-l） of non-essential amino acids in fresh fruit and 9 kinds （18.3 mg. g-l） in dried fruit, respectively. Tyrosine wasn＇t detected in the fresh fruit. The other eight kinds include aspartic acid, histidine, serine, glutamic acid, glyeine, alanine, cystine and praline in fresh and dried fruit. GC-MS results showed that 44 and 48 volatile components, including terpenes, alcohols, ketones, esters and acids, were identified in fresh and dried fruit, respectively. The terpenes accounted for 90% of the volatile components in flesh fruit, but only 48% in dried fruit. Alde- hydes were unique and critical in dried fruit. [Conclusion] The results indicated that the nutritional and aroma contents of total sugar, reducing sugar, amino acid and organic acid were higher in dried fruit than in fresh fruit due to the concentrated effect. Fresh and dried fruit have significant differences in the Vola- tile aroma components.