2.2 不同貯藏條件下不同組織檸檬苦素含量變化
圖2顯示,檸檬苦素主要分布在種子和外果皮中,囊衣次之,汁胞和中果皮中含量最少。采摘時(shí)檸檬苦素在種子、外果皮、囊衣、中果皮和汁胞中的含量分別為(1470.04 ± 59.94)、(685.69 ± 30.90)、(121.51 ± 1.07)、(35.08 ± 3.05)和(6.13 ± 0.16) μg·g-1。貯藏過(guò)程中,各處理果實(shí)中果皮和種子的檸檬苦素含量逐漸下降,在種子中,經(jīng)4 ℃低溫貯藏的果實(shí)檸檬苦素含量最低,下降速度最快,而在中果皮不同貯藏條件差異不明顯。各處理果實(shí)外果皮和汁胞中檸檬苦素含量在貯藏第30天,上升達(dá)到最高峰,隨后急劇下降然后緩慢下降,汁胞中檸檬苦素含量以4 ℃低溫不包薄膜袋貯藏最高,室溫不包膜貯藏最低。貯藏第30天A、B、C 3種不同貯藏條件汁胞中檸檬苦素含量分別為(47.28 ± 1.91)、(33.64 ± 1.90)和(84.19 ± 5.56) μg·g-1。
2.3 不同貯藏條件下不同組織諾米林含量變化
諾米林主要分布在種子中,外果皮和囊衣次之,汁胞和中果皮中含量最少。采摘時(shí)諾米林在種子、外果皮、中果皮、囊衣和汁胞中的含量分別為(1 673.88 ± 0.21)、(140.91 ± 3.50)、(40.2 ± 2.87)、(358.27 ± 12.20)和(22.57 ± 0.35) μg·g-1。貯藏過(guò)程中,囊衣和種子中諾米林含量逐漸下降,且4 ℃低溫不包薄膜袋貯藏果實(shí)含量最低。外果皮和中果皮中諾米林含量在貯藏過(guò)程中先下降后上升然后再下降,在中果皮中,室溫不包薄膜袋果實(shí)諾米林含量最高,外果皮中各處理間差異不顯著。汁胞中諾米林含量在貯藏第30天達(dá)到最大值然后下降,以室溫包薄膜袋貯藏的果實(shí)諾米林含量最高。在貯藏第30天,3種不同貯藏方式汁胞中諾米林含量分別為(68.29 ± 3.60)、(54.71 ± 1.82)和(53.49 ± 2.13) μg·g-1。
3討論
柑橘類果實(shí)中主要含有兩類苦味物質(zhì),一類是黃酮類化合物,以柚皮苷為主。在柑橘果實(shí)生長(zhǎng)發(fā)育過(guò)程中,柚皮苷的含量變化隨著果實(shí)成熟度的增加呈現(xiàn)先升高后下降的趨勢(shì)且在果實(shí)中的分布也極為不均勻(Sun et al, 2005)。沙田柚成熟果實(shí)苦味物質(zhì)主要以柚皮苷為主,主要分布在中果皮和囊衣中,汁胞中含量最少,這與Sun et al(2005)的結(jié)果一致。在貯藏過(guò)程中各組織柚皮苷含量起伏波動(dòng)并逐漸上升,說(shuō)明柚皮苷等黃酮類化合物可能具有采后合成特性。三種貯藏方式相比,在貯藏后期,經(jīng)4 ℃低溫貯藏的果實(shí)其外果皮、中果皮和囊衣中柚皮苷含量最低,這可能因?yàn)榈蜏匾种屏髓制ぼ盏牟珊蠛铣?。而在果?shí)汁胞中,經(jīng)4 ℃低溫貯藏的果實(shí)柚皮苷含量上升速度最快,室溫包膜的果實(shí)上升速度最慢,這可能與植物自身的防御反應(yīng)為提高生物抗氧化性有關(guān),且環(huán)境條件變化越明顯其合成速度越快,具體作用機(jī)制需要進(jìn)一步研究。
柑橘類果實(shí)中另一類苦味物質(zhì)是檸檬苦素類化合物,以檸檬苦素和諾米林等為主(眭順照等,2008)。檸檬苦素類化合物的產(chǎn)生是以角鯊烯為起始物,在植物體內(nèi)通過(guò)三萜的生物合成途徑合成。首先在莖部的篩管中經(jīng)醋酸和甲羥戊酸合成檸檬苦素類似物的最初前體物質(zhì)諾米林,再向葉、果實(shí)和種子轉(zhuǎn)運(yùn)(Nakatani, 2001),諾米林經(jīng)過(guò)檸檬苦素群、宜昌根辛群、卡拉敏群以及醋酸酯類檸檬苦素類似物群4個(gè)合成途徑最終形成檸檬苦素類化合物(蔡護(hù)華和橋永文男,1996)。本研究表明,在成熟沙田柚果實(shí)中檸檬苦素和諾米林主要存在種子中,汁胞中含量最低,在貯藏過(guò)程中各組織檸檬苦素含量呈現(xiàn)下降趨勢(shì)。但檸檬苦素在水溶液中的苦味閾值約為6 mg·kg-1,比柚皮苷的苦味強(qiáng)度高20倍(Kuroyanagi et al, 2008),因此檸檬苦素可能是影響沙田柚口感最主要的苦味成分。
本研究在貯藏第1~30天各處理果實(shí)汁胞中檸檬苦素含量急劇上升然后下降,且低溫貯藏的果實(shí)汁胞中檸檬苦素含量高于室溫包膜和不包膜的果實(shí)。柑橘果實(shí)中存在少量檸檬苦素,但卻存在大量的檸檬苦素前體物質(zhì)-檸檬苦素A環(huán)內(nèi)酯(Breksa et al, 2005),當(dāng)果實(shí)受到迫害時(shí),果汁細(xì)胞的細(xì)胞質(zhì)隔膜中的檸檬苦素A環(huán)內(nèi)酯暴露在酸性果汁環(huán)境中,同時(shí)在檸檬苦素D環(huán)內(nèi)酯水解酶作用下快速轉(zhuǎn)變成檸檬苦素(蔡護(hù)華和橋永文男,1996)。因此貯藏前期檸檬苦素含量的增加可能因?yàn)楣麑?shí)在離開(kāi)樹(shù)體后為適應(yīng)環(huán)境變化進(jìn)行自身調(diào)節(jié),在檸檬苦素D環(huán)內(nèi)酯水解酶作用下合成檸檬苦素,且4 ℃低溫脅迫更能促進(jìn)檸檬苦素合成與轉(zhuǎn)化,這與丁帆(2010)研究一致。而汁胞中諾米林含量以4 ℃低溫貯藏的果實(shí)最低,可能因?yàn)榈蜏丨h(huán)境促進(jìn)了諾米林作為合成前體向檸檬苦素類似物進(jìn)行轉(zhuǎn)化。
王壯(2011)研究了不同地理位置柑橘果實(shí)檸檬苦素和諾米林的含量,結(jié)果表明其主要受溫度影響,檸檬苦素含量隨溫度的升高呈下降趨勢(shì),而諾米林則呈上升的變化趨勢(shì),這與我們的研究不一致,這可能因?yàn)楣麑?shí)在發(fā)育和采后過(guò)程中苦味物質(zhì)的作用機(jī)制不同。而在外果皮、囊衣和種子中,經(jīng)4 ℃低溫貯藏的果實(shí)柚皮苷和檸檬苦素含量低于室溫貯藏,與汁胞中不一致,這可能因?yàn)榻M織中含水量和酸堿度不同,汁胞在環(huán)境脅迫下反應(yīng)更明顯,而在其他組織存在著脅迫條件下苦味物質(zhì)的合成與自然衰老過(guò)程中物質(zhì)降解的一個(gè)平衡,也可能存在組織間物質(zhì)轉(zhuǎn)運(yùn),具體原因需要進(jìn)一步研究。
參考文獻(xiàn):
BREKSA AP 3RD, ZUKAS AA, MANNERS GD, 2005. Determination of limonoate and nomilinoate A-ring lactones in citrus juices by liquid chromatography-electrospray ionization mass spectrometry [J]. J Chromatogr A,1 064: 187-191.
CAI HH,HASHINAGA F, 1996. The prospect and current studies on the limonoids in Citrus [J]. Acta Bot Sin,38(4):328-336. [蔡護(hù)華,橋永文男, 1996. 柑橘果實(shí)中檸檬苦素類化合物的研究現(xiàn)狀與展望 [J]. 植物學(xué)報(bào),38(4):328-336.]
DING F,LIU B Z,WANG Z, et al, 2010. Effects of different storage temperature on changes of limonin and naringin content in pulp of Satsuma Mandarin [J]. J Huazhong Agric Univ,29(2):221-226. [丁帆,劉寶貞,王壯, 等, 2010. 貯藏溫度對(duì)柑橘果肉中檸檬苦素和柚皮苷含量變化的影響 [J]. 華中農(nóng)業(yè)大學(xué)學(xué)報(bào),29(2):221-226.]
HUANG GX, 2005. Study on the integrated techniques of quality improving of shatianyou (CitrusgrandisOsbeck)[D]. Nanning: Guangxi University.[黃桂香. 2005. 沙田柚品質(zhì)改良綜合技術(shù)研究 [D]. 南寧:廣西大學(xué)]
KUROYANAGI M, ISHII H, KAWAHARA N, et al, 2008. Flavonoid glycosides and limonoids from Citrus molasses [J]. J Nat Med, 62: 107-111.
LIU JJ, 2006. Study on bitterness mechanism and bitter compounds [J]. Food Sci Technol,8(3):21-24. [劉晶晶, 2006. 苦味機(jī)理及苦味物質(zhì)的研究概況 [J]. 食品科技,8(3):21-24.]MORIGUCHI T, KITA M, TOMONO Y, et al, 2001. Gene expression in flavonoid biosynthesis: correlation with flavonoid accumulation in developing citrus fruit [J]. Physiol Plant, 114: 251-258.
NAKATANI M, 2001. Limonoids from Meliaecae and their biological activities. bioactive compounds from natural sources [M]. London: Taylor & Fran: 527-554.OU SH,LIAO KF,XIAO YH,et al, 2010. The selection of self-pollination pomelo variety“Guiyou 1” [J]. Guangxi Agric Sci,41(1):4-6. [區(qū)善漢,廖奎富,肖遠(yuǎn)輝,等, 2010. 自花結(jié)果沙田柚品種“桂柚1號(hào)”選育初報(bào) [J]. 廣西農(nóng)業(yè)科學(xué),41(1):4-6.]
SUI SZ,ZANG Q,LUO J, et al, 2008. Molecular cloning and analysis of a novel gene encoding limonoid glucosyl transfer ase ( LGT) inCitrusmaxima[J]. J Fruit Sci,25(4):607-610. [眭順照,張倩,羅江會(huì), 等, 2008. 柚苦味形成相關(guān)基因CmLGT的克隆與分析 [J]. 果樹(shù)學(xué)報(bào),25(4):607-610.]
SUN CD, CHEN KS, CHEN Y, et al, 2005. Contents and antioxidant capacity of limonin and nomilin in different tissues of citrus fruit of four cultivars during fruit growth and maturation [J]. Food Chem, 93(4): 599-605.SUN ZG,HUANG XG,JIAO BN, et al, 2005. Studied on the distributing of main bitter components in citrus fruit and the debittering technology of orange juice [J]. Food Sci,26(6):146-148. [孫志高,黃學(xué)根,焦必寧, 等, 2005. 柑橘果實(shí)主要苦味成分的分布及橙汁脫苦技術(shù)研究 [J]. 食品科學(xué),26(6):146-148.]
WANG Z, 2011. Bilterness quality evaluation of fruit from different citrus germplasm resources and Newhall navel orange harvested in different area[D]. Wuhan: Huazhong Agricultrual University. [王壯. 2011. 不同柑橘種質(zhì)資源及不同產(chǎn)區(qū)紐荷爾臍橙果實(shí)苦味品質(zhì)的評(píng)價(jià) [D]. 武漢:華中農(nóng)業(yè)大學(xué).]ZHANG KC, 2004. Study progress in bitterness mechanism and bitterness depressant technique [J]. Chin Cond,309. [張開(kāi)誠(chéng), 2004. 苦味機(jī)理與苦味抑制技術(shù)研究概況 [J]. 中國(guó)調(diào)味品,309.]
Effects of different storage conditions on changes of bitter substance of “Shatian” Pomelo
LIU Ping1,2, HUANG Chun-Xia1,2, DENG Guang-Zhou1,2*, FAN Qi-Jun1,2, NIU Ying1,2
( 1.GuangxiAcademyofSpecialtyCrops, Guilin 541004, China; 2.GuangxiKeyLaboratoryofCitrusBiology, Guilin 541004, China )
Abstract:The “Shatian” Pomelo (Citrus grandis Osbeck) was native to Guangxi, rich in nutrition and for hypertension and diabetes patients to eat. In recent years, there were many problems in the industry, such as quality decreased, smell and bitter generated. The “Shatian” Pomelo were stored under ambient temperature with film (A), ambient temperature without film (B) and 4 ℃ without film (C). Naringin, limonin and nomilin contents in different sues of fruits were determined during storage by high-performance liquid chromatography. The results showed that Naringin as main bittering substance of Shatian” Pomelo was distributed in the albedos and segment membranes. Limonoids mainly distributed in the seeds and flavedos, and nomilin mainly distributed in the seeds. Changes of bittering substance contents were different during storage under three storage conditions. The naringin content slightly increased during storage, while limonin and nomilin contents declined overall with a minor fluctuation. The contents of limonin and nomilin in juice sac increased firstly and then decreased. On the 30th day of storage, A, B and C storage conditions of naringin contents in juice sacs were (0.139 ± 0.006), (0.190 ± 0.009) and (0.194 ± 0.019) mg·g-1respectively and limonin contents were (47.28 ± 1.91), (33.64 ± 1.90) and (84.19 ± 5.56) μg·g-1respectively. Comparing with the A and B storage conditions, the contents of naringin and limonin of fruit juice sac under 4 ℃ low temperature storage (C storage conditions) were the highest. On the contrary, the contents of naringin, limonin and nomilin in flavedos, albedos, segment membranes and seeds were the lowest under C storage condition. This study provides theoretical guides for storage of postharvest “Shatian” Pomelo.
Key words:“Shatian” Pomelo, postharvest storge, HPLC(high-performance liquid chromatography), naringin, limonin, nomilin
DOI:10.11931/guihaia.gxzw201409034
收稿日期:2014-09-16修回日期:2015-03-23
基金項(xiàng)目:廣西自然科學(xué)基金(2012GXNSFAA053040);國(guó)家現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)技術(shù)體系廣西創(chuàng)新團(tuán)隊(duì)建設(shè)專項(xiàng)(桂農(nóng)業(yè)發(fā)〔2011〕33號(hào));廣西科學(xué)研究與技術(shù)開(kāi)發(fā)計(jì)劃項(xiàng)目(桂科能1347013-9;桂科能14123006-31)[Supported by the Natural Science Foundation of Guangxi (2012GXNSFAA053040); Guangxi Special Fund for Innovation Team Construction of the National System of Modern Agricultural Technology (〔2011〕33號(hào))]; Scientific Research and Technology Development Project of Guangxi(1347013-9;14123006-31)。
作者簡(jiǎn)介:劉萍(1983-),女,山西左權(quán)人,碩士,助理研究員,從事采后生物技術(shù)與研究工作,(E-mail)liupingsmile@126.com。 *通訊作者:鄧光宙,高級(jí)農(nóng)藝師,從事柑橘品種選育及柑橘無(wú)病苗繁育研究工作,(E-mail)dgz66@126.com。
中圖分類號(hào):Q945
文獻(xiàn)標(biāo)識(shí)碼:A
文章編號(hào):1000-3142(2016)06-0658-05
劉萍,黃春霞,鄧光宙,等. 不同貯藏條件對(duì)沙田柚果實(shí)苦味物質(zhì)含量的影響[J]. 廣西植物, 2016, 36(6):658-662
LIU P,HUANG CX,DENG GZ,et al. Effects of different storage conditions on changes of bitter substance of “Shatian” Pomelo[J]. Guihaia, 2016, 36(6):658-662