小麥制粉產(chǎn)品穩(wěn)定碳、氮同位素組成特征

劉宏艷，郭波莉，魏帥，姜濤，張森燊，魏益民

（中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)產(chǎn)品加工研究所/農(nóng)業(yè)部農(nóng)產(chǎn)品加工綜合性重點(diǎn)實(shí)驗(yàn)室，北京 100193）

小麥制粉產(chǎn)品穩(wěn)定碳、氮同位素組成特征

劉宏艷，郭波莉，魏帥，姜濤，張森燊，魏益民

（中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)產(chǎn)品加工研究所/農(nóng)業(yè)部農(nóng)產(chǎn)品加工綜合性重點(diǎn)實(shí)驗(yàn)室，北京 100193）

【目的】小麥制粉產(chǎn)品穩(wěn)定同位素指紋相對(duì)于全粒粉是否存在分餾效應(yīng)，這些產(chǎn)品能否用于小麥的產(chǎn)地溯源，以及利用穩(wěn)定同位素是否能實(shí)現(xiàn)對(duì)小麥制粉產(chǎn)品來(lái)源地的鑒別還不清楚。系統(tǒng)分析全麥粉及各制粉產(chǎn)品中碳、氮同位素在地域間、基因型間的差異，揭示小麥制粉產(chǎn)品碳、氮同位素的組成特征及相關(guān)性，為小麥及其制品產(chǎn)地溯源提供理論與技術(shù)支撐。【方法】2014年將3個(gè)不同基因型小麥品種（邯6172、衡5229和周麥16），種植于河北石家莊趙縣、陜西楊凌區(qū)和河南省新鄉(xiāng)輝縣。每個(gè)地域3個(gè)小區(qū)，每小區(qū)面積10 m2，試驗(yàn)田按照當(dāng)?shù)匦←溒贩N區(qū)域試驗(yàn)管理。2015年收獲期于3個(gè)地域共采集27份小麥樣品，小麥籽粒粉碎制得全麥粉；同時(shí)將小麥籽粒加工制粉，得到面粉、次粉和麩皮。利用元素分析-同位素比率質(zhì)譜儀（EA-IRMS）測(cè)定全麥粉及制粉產(chǎn)品（麩皮、次粉和面粉）中的穩(wěn)定碳、氮同位素。結(jié)合單因素方差分析及Duncan多重比較分析解析碳、氮同位素在不同地域、不同基因型以及不同制粉產(chǎn)品間的差異，結(jié)合皮爾遜相關(guān)分析及線性回歸分析，解析不同種類樣品碳、氮同位素的相關(guān)性?！窘Y(jié)果】不同地域來(lái)源全麥粉及制粉產(chǎn)品中碳、氮同位素均有顯著差異（P＜0.05），碳同位素在地域間變化趨勢(shì)為楊凌＞輝縣＞趙縣，氮同位素在地域間變化趨勢(shì)為輝縣＞趙縣＞楊凌；全麥粉、麩皮和面粉中碳同位素及各類產(chǎn)品中氮同位素在基因型間均無(wú)顯著差異，次粉中碳同位素在邯6172和衡5229之間有顯著差異；碳同位素在全麥粉和不同制粉產(chǎn)品間存在顯著差異（P＜0.05），面粉對(duì)13C略顯富集，次粉和麩皮相對(duì)貧化13C，而氮同位素在四類產(chǎn)品間無(wú)顯著差異；全麥粉和各制粉產(chǎn)品碳、氮同位素相互之間均呈極顯著相關(guān)關(guān)系（P＜0.01）?！窘Y(jié)論】碳同位素在小麥不同制粉產(chǎn)品間有顯著差異，氮同位素在小麥不同制粉產(chǎn)品間無(wú)顯著差異，不同制粉產(chǎn)品與小麥全麥粉中碳、氮同位素呈極顯著相關(guān)關(guān)系；全麥粉及制粉產(chǎn)品中碳、氮同位素具有顯著的地域特征，可用于小麥及其制粉產(chǎn)品的產(chǎn)地溯源。

小麥；制粉；面粉；產(chǎn)地溯源；穩(wěn)定碳同位素；穩(wěn)定氮同位素

0 引言

【研究意義】小麥?zhǔn)菄?guó)內(nèi)外谷物貿(mào)易的重要糧食作物，然而，為獲取經(jīng)濟(jì)利益，跨地域交易中優(yōu)質(zhì)小麥經(jīng)常被偽劣小麥替代，對(duì)消費(fèi)者以及合法的生產(chǎn)商均帶來(lái)較大的負(fù)面影響[1]。小麥產(chǎn)地溯源技術(shù)的建立，可有效協(xié)助政府監(jiān)管、保護(hù)消費(fèi)者利益、保障糧食安全。穩(wěn)定同位素是用于小麥產(chǎn)地溯源的有效指標(biāo)，研究小麥及其制粉產(chǎn)品中穩(wěn)定同位素的組成特征及其在地域間、基因型間的變化規(guī)律，有助于擴(kuò)大穩(wěn)定同位素溯源指紋技術(shù)的應(yīng)用范圍，可為小麥產(chǎn)地溯源及小麥產(chǎn)業(yè)鏈追溯提供理論和技術(shù)支撐。【前人研究進(jìn)展】由于光合過(guò)程中羧化酶對(duì)同位素的分餾效應(yīng)以及氣孔的擴(kuò)散分餾效應(yīng)不同, C3植物、C4植物和CAM植物的13C有明顯區(qū)別。一般C3植物的δ13C=-23‰—-38‰，C4植物的δ13C= -12‰—-14‰，CAM植物δ13C值界于C3和C4植物之間[2]。另一方面，影響植物碳同位素分餾的氣候環(huán)境因素有溫度、降水、壓力、光照、大氣壓及大氣中 CO2的碳同位素組成等[3]。因此，即使同一種植物，其體內(nèi)碳同位素組成也因不同地域環(huán)境因素的差異而不同。目前，穩(wěn)定碳同位素指紋溯源技術(shù)已被應(yīng)用于谷物[4-6]、酒類[7-8]、果蔬[9-11]等植源性農(nóng)產(chǎn)品的產(chǎn)地溯源中。動(dòng)物通過(guò)食物鏈攝食不同種類不同配比的植物，使得碳同位素也在肉類[12-13]、奶類[14-16]、魚(yú)類[17]等動(dòng)物源性食品產(chǎn)地溯源中得以應(yīng)用。植物中的氮取決于土壤中的氮池（硝酸鹽和氨水），而土壤中氮同位素組成取決于地理和氣候條件，并與農(nóng)業(yè)施肥有關(guān)，其通過(guò)影響礦化、硝化、氮的吸收和反硝化等生物轉(zhuǎn)化過(guò)程，進(jìn)而影響氮同位素分餾效應(yīng)和氮的流失程度[18-19]。目前，用于小麥產(chǎn)地溯源研究的樣品主要是全麥粉，BRANCH等[20]測(cè)定了來(lái)自美國(guó)、加拿大和歐洲小麥全麥粉中礦物元素含量（Cd、Se）與穩(wěn)定同位素組成（δ13C、δ15N、208Pb/206Pb、207Pb/206Pb和87Sr/86Sr），發(fā)現(xiàn)單獨(dú)使用δ13C可完全區(qū)分3個(gè)不同地域來(lái)源的小麥樣品。LUO等[21]測(cè)定來(lái)自澳大利亞、美國(guó)、加拿大以及中國(guó)江蘇省和山東省的 35份全麥粉樣品，發(fā)現(xiàn) δ13C在不同地域間具有顯著差異（P＜0.05），利用δ13C、δ15N同位素繪制二維分布圖，能夠明顯區(qū)分不同地域間樣品。全麥粉是由小麥籽粒粉碎制成，其穩(wěn)定同位素組成表征籽粒中各種成分同位素的權(quán)重。小麥的主要消費(fèi)途徑是制成面粉，該過(guò)程還產(chǎn)生麩皮和次粉兩類制粉產(chǎn)品。前人研究表明，礦物元素溯源指紋在麩皮、次粉和面粉間具有顯著差異[22]，而穩(wěn)定同位素在不同制粉產(chǎn)品間是否存在分餾效應(yīng)，不同產(chǎn)品中碳、氮同位素在地域間以及基因型間的表現(xiàn)是否一致，均為未知?！颈狙芯壳腥朦c(diǎn)】小麥制粉產(chǎn)品中穩(wěn)定同位素能否表征地域特征、進(jìn)而應(yīng)用于小麥產(chǎn)地及其自身的產(chǎn)地判別還不清楚，全麥粉與制粉產(chǎn)品中碳、氮同位素之間相關(guān)性的研究還未見(jiàn)報(bào)道。【擬解決的關(guān)鍵問(wèn)題】以小麥為模式植物，設(shè)計(jì)模型試驗(yàn)，解析不同地域、不同基因型和不同制粉產(chǎn)品中碳、氮同位素的差異特征，明確全麥粉與制粉產(chǎn)品中碳、氮同位素的關(guān)系，為小麥及制粉產(chǎn)品的產(chǎn)地溯源提供理論參考。

1 材料與方法

1.1 試驗(yàn)材料

2014年選擇3種基因型小麥（邯6172、衡5229、周麥16），分別種植于河北省石家莊趙縣、河南省新鄉(xiāng)市輝縣和陜西省楊凌區(qū)3個(gè)試驗(yàn)點(diǎn)。每個(gè)地域3個(gè)基因型小麥隨機(jī)排列，每個(gè)小區(qū)面積 10 m2。試驗(yàn)田按照當(dāng)?shù)匦←溁蛐蛥^(qū)域試驗(yàn)管理。2015年收獲期在每個(gè)試驗(yàn)點(diǎn)每個(gè)小區(qū)隨機(jī)選擇3個(gè)點(diǎn)作為重復(fù)，每點(diǎn)收割1 m2，共采集小麥樣品27份。樣品信息見(jiàn)表1。

表1 各試驗(yàn)站地理位置、氣象因子及田間措施Table 1 The geographic locations, climate factors and field management of each experiment field

1.2 試驗(yàn)方法

1.2.1 樣品前處理 將收獲后小麥進(jìn)行晾曬，手工脫粒，然后將小麥籽粒運(yùn)往實(shí)驗(yàn)室進(jìn)行前處理。挑出小麥籽粒中的石子、雜草等雜物，用去離子水反復(fù)沖洗干凈，38℃烘箱內(nèi)約24 h烘干至恒重。烘干樣品用植物粉碎機(jī)粉碎，過(guò)100目篩，得到全麥粉樣品。

1.2.2 小麥制粉 稱取300 g小麥籽粒樣品，進(jìn)行潤(rùn)麥。添加超純水（Milli-Q，Millipore，USA），調(diào)整衡5229和周麥16小麥含水率到14.5%，調(diào)整邯6172小麥含水率到15%，潤(rùn)麥時(shí)間24 h。采用實(shí)驗(yàn)性制粉機(jī)（LRMM8040-3-D，中國(guó)無(wú)錫錫糧機(jī)械制造有限公司）配合粉篩（LFS-30，中國(guó)無(wú)錫錫糧機(jī)械制造有限公司）分離小麥麩皮、次粉與面粉。麩皮和次粉樣品用植物粉碎機(jī)粉碎，過(guò)100目篩，烘干備用。

1.2.3 樣品測(cè)定 稱取5 mg樣品放入錫箔杯中，通過(guò)自動(dòng)進(jìn)樣器進(jìn)入元素分析儀（vario PYRO cube，Elementar，Germany），通過(guò)燃燒與還原轉(zhuǎn)化為純凈的CO2和N2氣體，CO2再經(jīng)過(guò)稀釋器稀釋，最后進(jìn)入穩(wěn)定同位素質(zhì)譜儀（IsoPrime100，IsoPrime，UK）進(jìn)行檢測(cè)。具體的工作參數(shù)如下：

元素分析儀條件：燃燒爐溫度為1 020℃，還原爐溫度為600℃，載氣He流量為230 mL·min-1。

質(zhì)譜儀條件：分析過(guò)程中，每12個(gè)樣品穿插一個(gè)實(shí)驗(yàn)室標(biāo)樣，IAEA600（δ13CPDB=(-27.771±0.043)‰，δ15Nair=(1.0±0.2)‰）對(duì)測(cè)定結(jié)果進(jìn)行校正。

穩(wěn)定同位素比率計(jì)算如下：

δ（‰）=（R樣品/R標(biāo)準(zhǔn)-1）×1000

其中，R為重同位素與輕同位素豐度比，即13C/12C和15N/14N, δ13C的相對(duì)標(biāo)準(zhǔn)為V-PDB，δ15N的相對(duì)標(biāo)準(zhǔn)是空氣中氮?dú)狻?/p>

測(cè)定時(shí)，δ13C和δ15N的連續(xù)測(cè)定精度＜0.2‰。

1.3 數(shù)據(jù)處理及質(zhì)量控制

用SPSS 18.0軟件分別對(duì)數(shù)據(jù)進(jìn)行單因素方差分析，Duncan多重比較分析，皮爾遜（Pearson）相關(guān)分析。

2 結(jié)果

2.1 小麥及制粉產(chǎn)品中碳、氮同位素在地域間的差異

通過(guò)對(duì)不同地域全麥粉及不同制粉產(chǎn)品中碳、氮同位素進(jìn)行單因素方差分析，結(jié)果表明，全麥粉及制粉產(chǎn)品中碳同位素在趙縣與輝縣/楊凌間有顯著差異，氮同位素在不同地域間有顯著差異（P＜0.05）（表2）。各類樣品中碳同位素在不同地域間變化趨勢(shì)一致，均為楊凌最高，趙縣最低；各類樣品中氮同位素在地域間變化趨勢(shì)也一致，均為輝縣＞趙縣＞楊凌。小麥中氮同位素值與當(dāng)?shù)厥褂梅柿系姆N類有一定關(guān)系，輝縣施用復(fù)合肥（δ15N=（4.39±0.41）‰），楊凌施用尿素（δ15N=（-6.89±0.03）‰）和磷酸二銨（δ15N=（-3.34±0.07）‰），趙縣施用尿素（δ15N=（-0.47±0.00）‰）和磷酸二銨（δ15N=（1.54±0.04）‰）。

表2 不同地域全麥粉及小麥制粉產(chǎn)品中的碳、氮同位素Table 2 δ13C, δ15N in wheat milling fractions among different regions

2.2 小麥及制粉產(chǎn)品中碳、氮同位素在基因型間的差異

通過(guò)對(duì)不同基因型的全麥粉及制粉產(chǎn)品中碳、氮同位素進(jìn)行單因素方差分析，結(jié)果表明，全麥粉、麩皮和面粉中碳同位素在3種基因型間無(wú)顯著差異，次粉中碳同位素在邯6172和衡5229之間有顯著差異；全麥粉及其他制粉產(chǎn)品中氮同位素在不同基因型間均無(wú)顯著差異（表3）。

2.3 小麥制粉產(chǎn)品間碳、氮同位素差異

圖1表示全麥粉與制粉產(chǎn)品中碳、氮同位素分布，以及單因素方差分析多重比較結(jié)果。其中全麥粉碳同位素處于中間，平均值為-28.24‰，變幅為-28.90‰—-27.44‰，面粉碳同位素最高，平均值為-28.07‰，變幅為-28.71‰—-27.57‰，麩皮碳同位素最低，平均值為-29.02‰，變幅為-30.02‰—-28.54‰。全麥粉、次粉及麩皮中碳同位素存在顯著差異，其中麩皮和次粉中碳同位素相對(duì)貧化。盡管全麥粉與面粉中碳同位素?zé)o顯著差異，但面粉中碳同位素平均值高于全麥粉，略顯富集。

表3 不同基因型全麥粉及制粉產(chǎn)品中的碳、氮同位素Table 3 δ13C, δ15N in wheat milling fractions among different genotypes

圖1 小麥制粉產(chǎn)品中穩(wěn)定碳（A）、氮（B）同位素組成Fig. 1 δ13C (A) and δ15N (B) of different milling fractions

氮同位素在不同制粉產(chǎn)品間無(wú)顯著差異。全麥粉、麩皮、次粉及面粉的氮同位素變幅分別為-4.50‰—5.15‰、-4.20‰—4.79‰、-4.66‰—4.56‰及-3.92‰—5.10‰。

2.4 小麥及制粉產(chǎn)品碳、氮同位素的相關(guān)性

為了研究全麥粉與不同制粉產(chǎn)品中碳、氮同位素的關(guān)系，對(duì)數(shù)據(jù)采用皮爾遜相關(guān)分析（表4）。結(jié)果表明，全麥粉與不同制粉產(chǎn)品中碳、氮同位素均呈極顯著正相關(guān)（P＜0.01），3類制粉產(chǎn)品之間碳、氮同位素也呈極顯著正相關(guān)（P＜0.01）。

利用3類不同制粉產(chǎn)品與全麥粉碳、氮同位素進(jìn)行線性回歸分析（圖 2），結(jié)果表明，麩皮、次粉及面粉的碳同位素與全麥粉碳同位素線性擬合均較好，3條擬合線近似平行，且所有次粉樣品位于面粉與麩皮之間。3種制粉產(chǎn)品的氮同位素與全麥粉氮同位素?cái)M合效果優(yōu)于碳同位素，3條擬合線相互間隔較近，次粉與麩皮存在部分交叉，進(jìn)一步說(shuō)明不同制粉產(chǎn)品氮同位素差異較小。

表4 小麥及制粉產(chǎn)品中碳、氮同位素相關(guān)分析系數(shù)表Table 4 Correlation coefficient of δ13C and δ15N of different wheat milling fractions (n=27)

圖2 小麥中碳（A）、氮（B）同位素與制粉產(chǎn)品的線性回歸分析Fig. 2 Linear fittings of δ13C (A) and δ15N (B) between whole wheat flour and milling fractions

3 討論

小麥作為C3植物，其葉片碳同位素組成可表示為 δ13Cplant=δ13Cair-a-(b-a)Ci/Ca[23]，表明小麥碳同位素主要受大氣CO2的δ13C值、葉片內(nèi)外CO2分壓比的影響。大氣CO2的碳同位素值有隨緯度升高而增大的趨勢(shì)[24]，而本研究中緯度最低的楊凌小麥體內(nèi)碳同位素最高，因此其變異來(lái)源主要是葉片內(nèi)外 CO2分壓比。小麥碳同位素表現(xiàn)為隨海拔升高而增大的趨勢(shì)，該結(jié)果與前人研究一致[25-26]，然而，海拔對(duì)植物δ13C的影響是多種環(huán)境因素綜合作用的結(jié)果。海拔高度的變化引起降水量、光照、溫度、大氣壓等環(huán)境因素的變化，從而改變?nèi)~片形態(tài)、生理特性及光合氣體交換，最終影響植物δ13C值的大小。其中，碳同位素有隨濕度的降低而增加，隨光照的增強(qiáng)而增大的趨勢(shì)[3]，但以上趨勢(shì)均未在本研究中顯現(xiàn)，可能由于3個(gè)地點(diǎn)降水量、濕度和光照強(qiáng)度的變化較小，不足以引起碳同位素變化。因此，本研究中海拔升高主要引起CO2濃度和大氣壓的降低，導(dǎo)致植物的Ci/Ca值減小，從而導(dǎo)致小麥體內(nèi)碳同位素的增加。

比較不同地域小麥及化肥中氮同位素組成可知，氮同位素在不同地域間的差異主要受到栽培措施的影響，且受肥料影響較大。一方面化肥的種類不同，氮同位素值不同[27-28]。輝縣復(fù)合肥的氮同位素顯著高于楊凌和趙縣施用的尿素和磷酸二銨；即使同一種化肥，生產(chǎn)廠家不同，也具有不同的氮同位素值[29]。楊凌地區(qū)小麥?zhǔn)┯玫哪蛩睾土姿岫@中氮同位素值均低于趙縣小麥?zhǔn)┯玫倪@兩類化肥的氮同位素值。此外，在一定氮濃度內(nèi)，有機(jī)氮肥輸入越多，植物體內(nèi)的氮同位素隨之升高；無(wú)機(jī)氮肥輸入越多，植物體內(nèi)的氮同位素隨之降低[29]。LIM等[30]研究不同氮肥處理對(duì)盆栽大白菜和菊花中氮同位素的影響，發(fā)現(xiàn)未施肥的白菜和菊花中氮同位素值均顯著高于施用尿素處理。本研究中3個(gè)試驗(yàn)地點(diǎn)中楊凌施肥量最高，也可能是導(dǎo)致當(dāng)?shù)匦←滙w內(nèi)氮同位素更為貧化的原因之一。

前人研究表明，小麥籽粒碳同位素受基因型影響顯著[31-32]，并與植物本身的抗旱性和水分利用效率有關(guān)[33]。而本研究中全麥粉、面粉及麩皮的碳同位素在不同基因型間無(wú)顯著差異，可能由于所選的3個(gè)小麥品種間碳同位素本身差異較小所致。

在實(shí)際的制粉工藝中，麩皮、次粉和面粉中各組分含量因不同的潤(rùn)麥加水量、潤(rùn)麥時(shí)間、剝刮力度而略有不同。麥麩約占小麥籽粒的22%—25%，主要由果皮、種皮、糊粉層、少量胚和胚乳組成；次粉約占小麥籽粒的5%左右，其中胚乳高于麩皮而低于面粉，糊粉層的含量高于麩皮和面粉[34-35]；面粉主要由胚乳磨制而成，富含淀粉。本研究結(jié)果表明，制粉產(chǎn)品相對(duì)全麥粉碳同位素產(chǎn)生不同程度的貧化或富集。其中，麩皮和次粉碳同位素相對(duì)貧化，可能是由于二者相對(duì)于面粉具有較多的纖維素和木質(zhì)素；另一方面，面粉中碳同位素略顯富集，主要由于面粉富含淀粉，前人研究表明淀粉中碳同位素高于木質(zhì)素和纖維素中碳同位素值[36]。同一品種小麥次粉中的纖維素、木質(zhì)素和淀粉含量位于麩皮和面粉之間[36]，因此，其碳同位素值低于面粉但高于麩皮。

氮同位素在動(dòng)物不同組織間存在分餾效應(yīng)。其中，蛋白質(zhì)含量較高、脂肪含量較低的肌肉組織中氮同位素值較高，而脂肪含量較高的肝臟和腸組織中氮同位素值較低[37-38]。本研究中各類樣品中氮同位素?zé)o顯著差異，可能是由于全麥粉與制粉產(chǎn)品中蛋白質(zhì)和脂肪含量差異較小導(dǎo)致。

4 結(jié)論

小麥制粉產(chǎn)品與全麥粉中碳、氮同位素具有地域特征，且變化趨勢(shì)一致；小麥制粉產(chǎn)品中碳同位素具有顯著差異，氮同位素?zé)o顯著差異；全麥粉與制粉產(chǎn)品碳、氮同位素之間呈極顯著相關(guān)性。因此，碳、氮穩(wěn)定同位素指紋可用于小麥及其制粉產(chǎn)品的產(chǎn)地溯源。今后可進(jìn)一步研究小麥不同種類蛋白、脂肪等同位素組成特征及其用于小麥產(chǎn)地溯源的可行性。

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（責(zé)任編輯 趙伶俐）

Characteristics of Stable Carbon and Nitrogen Isotopic Ratios in Wheat Milling Fractions

LIU HongYan, GUO BoLi, WEI Shuai, JIANG Tao, ZHANG SenShen, WEI YiMin
(Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Comprehensive Key Laboratory of Agro-Products Processing, Ministry of Agriculture, Beijing 100193)

【Objective】 It remains unclear for several points when identifying the geographical origin of wheat. Is there any fractionation for the stable isotopic fingerprints of milling fractions by comparing with whole wheat flour, and whether the stable isotopic fingerprints in milling fractions can be used for identifying the geographical origin of the milling fractions as well as the whole wheat flour? These problems need to be resolved. This study was conducted to reveal the characteristics and correlations of stable carbon (δ13C) and nitrogen (δ15N) isotopic ratios in different milling fractions by analyzing the difference in stable isotopic ratios among milling fractions, regions or genotypes, which could provide a theoretical and technical basis for geographicaltraceability of wheat and its milling fractions.【Method】 In 2014, three genotypes of wheat (Han 6172, Heng 5229 and Zhoumai 16) were grown in three regions of China which were Huixian (Henan Province), Yangling (Shaanxi Province) and Zhaoxian (Hebei Province). Three plots were conducted in each region, the typical size of plot was 10 m2, recommended local agricultural practices were adopted. Totally 27 wheat samples were collected from three regions in 2015, whole wheat flour were obtained by grinding, and flour, wheat shorts and bran were obtained by milling. δ13C and δ15N were measured for whole wheat flour and milling fractions (flour, wheat shorts and bran) by an element analysis-isotope ratio mass spectrometer. One-way analysis of variance combined with Duncan’s multiple comparison was employed to identify the significant differences among different regions, genotypes and milling fractions at isotopic levels, and Pearson correlation analysis and linear regression analysis were used to test the correlations of δ13C and δ15N among different categories of samples.【Result】Significant differences were observed among different regions in δ13C and δ15N in whole wheat flour and milling fractions, and the δ13C in wheat from three regions decreased in the following order: Huixian＞Zhaoxian＞Yangling. No significant difference was found between different genotypes in δ13C in whole wheat flour, bran and flour, and in δ15N in each category of wheat samples, significant differences were found in δ13C between wheat genotypes of Han 6172 and Heng 5229. Significant differences were also found in δ13C among different categories of wheat samples (P＜0.05), δ13C was relatively enriched in flour and depleted in wheat shorts and bran, while no significant difference was found in δ15N among different categories of wheat samples. Significant correlations were found in δ13C and δ15N between different kinds of wheat samples (P＜0.01). 【Conclusion】There were significant differences in δ13C among different wheat milling fractions, but no significant differences in δ15N among different wheat milling fractions. Significant correlations were observed between different categories of wheat samples in δ13C and δ15N. Both δ13C and δ15N of whole wheat flour and milling fractions were characterized by geographical features, which could be used for identifying the geographical origin of wheat and its milling products.

wheat; mill; flour; geographical origin; stable carbon isotope; stable nitrogen isotope

2016-07-01；接受日期：2016-09-22

國(guó)家自然科學(xué)基金（31371774）、國(guó)家小麥產(chǎn)業(yè)技術(shù)體系建設(shè)專項(xiàng)（CARS-03）

聯(lián)系方式：劉宏艷，Tel：010-62815954；E-mail：lhy_cpu@126.com。通信作者魏益民，Tel：010-62815956；Fax：010-62895141；E-mail：weiyimin36 @hotmail.com