孫翠霞,劉夫國(guó),楊 偉,袁 芳,高彥祥

(中國(guó)農(nóng)業(yè)大學(xué)食品科學(xué)與營(yíng)養(yǎng)工程學(xué)院,北京 100083)

生物來(lái)源的固體顆粒制備Pickering乳液的研究進(jìn)展

孫翠霞,劉夫國(guó),楊 偉,袁 芳,高彥祥*

(中國(guó)農(nóng)業(yè)大學(xué)食品科學(xué)與營(yíng)養(yǎng)工程學(xué)院,北京 100083)

天然來(lái)源、可再生和可生物降解的固體顆粒用于制備Pickering乳液已成為研究熱點(diǎn)。本文綜述了固體顆粒的種類、制備方法與性質(zhì)表征,重點(diǎn)介紹了生物來(lái)源的有機(jī)顆粒如多糖和蛋白質(zhì)對(duì)Pickering乳液的穩(wěn)定作用,并總結(jié)了影響Pickering乳液穩(wěn)定性的因素,同時(shí)闡述了Pickering乳液在生命科學(xué)領(lǐng)域的潛在應(yīng)用。

固體顆粒,Pickering乳液,穩(wěn)定性

乳液(emulsion)是由一種或幾種液體以小液滴的形式分散于另一種與其互不相溶的液體中形成的多相分散體系,通常分為水包油型(O/W)和油包水型(W/O)[1]。由于油-水界面積較大,乳液是一種熱力學(xué)不穩(wěn)定體系,必須向體系中加入乳化劑,通過(guò)減少兩相之間的界面張力,才能獲得穩(wěn)定的乳液[2]。然而,過(guò)量的非食品級(jí)乳化劑必須從樣品中去除,否則會(huì)對(duì)人體產(chǎn)生傷害,影響和破壞乳液后續(xù)的應(yīng)用,如乳化劑會(huì)誘導(dǎo)組織發(fā)炎甚至造成細(xì)胞損傷,這使得由乳化劑制備的傳統(tǒng)乳液在醫(yī)藥制劑方面的應(yīng)用受到限制[3]。

20世紀(jì)初,Ramsden等人最早發(fā)現(xiàn)將不溶性固體細(xì)粉與水和一些油性溶劑進(jìn)行混合分散時(shí),固體細(xì)粉包裹在分散相液滴的表面,形成一個(gè)固體殼層;當(dāng)分散相液滴相互碰撞時(shí),固體殼層對(duì)液滴的變形和聚集起到阻礙作用,可以形成較為穩(wěn)定的乳液[4]。隨后,Pickering對(duì)該乳液體系進(jìn)行了較為深入和系統(tǒng)的研究[5]。因此,由固體顆粒代替乳化劑而制備的乳液被命名為Pickering乳液,如圖1所示[6]。另外,由固體顆粒通過(guò)界面作用阻止乳液液滴聚結(jié)的機(jī)制稱為Pickering穩(wěn)定[7]。Binks研究指出,固體顆粒在油-水界面產(chǎn)生不可逆的吸附,而表面活性劑在一定的時(shí)間范圍內(nèi)其吸附和解吸速度相對(duì)較快[8]。因此,與傳統(tǒng)表面活性劑穩(wěn)定的乳液相比,Pickering乳液具有更高的穩(wěn)定性,可廣泛應(yīng)用于醫(yī)藥、農(nóng)業(yè)、食品和化妝品等領(lǐng)域。

圖1 O/W型傳統(tǒng)乳液和Pickering乳液的結(jié)構(gòu)圖示[3]Fig.1 Sketches of the Pickering emulsionand a classical emulsion[3]

研究表明,Pickering乳液的穩(wěn)定性在很大程度上取決于固體顆粒的性質(zhì),因此,本文綜述了固體顆粒的種類、制備方法與性質(zhì)表征,重點(diǎn)介紹了生物來(lái)源的有機(jī)顆粒如多糖和蛋白質(zhì)對(duì)Pickering乳液的穩(wěn)定機(jī)理,并總結(jié)了影響Pickering乳液穩(wěn)定性的因素,同時(shí)闡述了Pickering乳液的應(yīng)用前景。

1 用于制備Pickering乳液的固體顆粒

目前對(duì)于固體顆粒穩(wěn)定Pickering乳液的研究集中于無(wú)機(jī)或合成粒子,如二氧化硅[9]、二氧化鈦[10]、鋰皂石粘土[11]、磁鐵礦[12]、氧化鋅[13]、氧化石墨烯[14]、各向異性的Janus顆粒[15]等。雖然由這些無(wú)機(jī)或合成粒子制備的Pickering乳液穩(wěn)定性較好,但生物相容性較差,這極大限制了Pickering乳液在醫(yī)藥、農(nóng)業(yè)、食品和化妝品等領(lǐng)域的應(yīng)用。因此,尋求環(huán)境友好型、天然來(lái)源、可再生和可生物降解的固體顆粒用于穩(wěn)定Pickering乳液已成為目前研究的熱點(diǎn)。

在現(xiàn)有的研究中,生物來(lái)源的膠體顆粒已用于穩(wěn)定Pickering乳液,如多糖類,包括淀粉納米晶[16-18]、經(jīng)化學(xué)修飾的淀粉納米顆粒[19]、纖維素納米晶[20-24]、甲殼素納米晶[25-26];蛋白質(zhì)類,包括大豆分離蛋白[27-28]、豌豆分離蛋白[29]、乳鐵蛋白[30]、乳清蛋白[31]、玉米醇溶蛋白[32-33];另外,還有具有生物活性的小分子物質(zhì)如黃酮[34-35]和植物甾醇[36]。

1.1 多糖

多糖是多分散性大分子,親水性強(qiáng)。一些多糖能夠吸附在油-水界面,通過(guò)界面相互作用,作為乳液的穩(wěn)定劑。Li等[37]選用大米淀粉、小麥淀粉和蠟質(zhì)玉米淀粉制備出穩(wěn)定的乳液,其中大米淀粉(顆粒直徑為5.2 μm)制備的乳液穩(wěn)定性最好。Rayner等[38]采用藜麥淀粉(顆粒直徑為2.5 μm)制備穩(wěn)定的乳液,由于藜麥淀粉不含谷朊蛋白,無(wú)致敏性,顆粒直徑相對(duì)較小(直徑為0.5～3 μm)且分布均勻,使藜麥淀粉成為穩(wěn)定Pickering乳液的研究熱點(diǎn)。

多糖膠體表面活性源于兩種途徑,一是某些非極性的化學(xué)基團(tuán)吸附在親水多糖的骨架上,二是蛋白質(zhì)與碳水化合物(如阿拉伯膠、甜菜果膠)發(fā)生部分共價(jià)結(jié)合[39-40]。即使多糖不具有表面活性,只要能與預(yù)先吸附的蛋白質(zhì)通過(guò)靜電絡(luò)合形成次級(jí)空間保護(hù)層,也能夠促進(jìn)乳液的界面穩(wěn)定[41]。另外,多糖組分可通過(guò)誘導(dǎo)與蛋白質(zhì)共價(jià)結(jié)合形成永久的結(jié)合物。最常用的方法是干熱處理,即美拉德反應(yīng)。所得的具有表面活性的蛋白質(zhì)-多糖結(jié)合物可以用于制備Pickering乳液[42-43]。

1.2 蛋白質(zhì)

大多數(shù)蛋白質(zhì)分子具有吸附在油-水界面、伸展并且聚集形成二維網(wǎng)絡(luò)的能力,可作為乳液有效的穩(wěn)定劑[44]。用于吸附的主要熱力學(xué)驅(qū)動(dòng)力使蛋白質(zhì)的非極性側(cè)鏈遠(yuǎn)離水溶液的不利環(huán)境,使界面區(qū)域的水分子濃度降低。次級(jí)驅(qū)動(dòng)力與吸附的蛋白質(zhì)分子的伸展有關(guān)。這會(huì)進(jìn)一步導(dǎo)致蛋白質(zhì)與蛋白質(zhì)、蛋白質(zhì)與水之間相互作用的平衡發(fā)生變化[45]。一旦吸附,蛋白質(zhì)通常不能輕易地從界面解吸。因此,蛋白質(zhì)的吸附通常認(rèn)為是“不可逆”的。吸附在界面的蛋白質(zhì)對(duì)分散顆粒和液滴的穩(wěn)定作用與蛋白質(zhì)的分子結(jié)構(gòu)、水溶液的離子強(qiáng)度有關(guān),可以結(jié)合空間作用和靜電作用進(jìn)行解釋[46]。如無(wú)序的蛋白質(zhì)如酪蛋白,是一種優(yōu)良的空間穩(wěn)定劑[47]。一旦蛋白質(zhì)吸附在單個(gè)分散的油滴上,在油-水界面形成單吸附層,會(huì)產(chǎn)生較強(qiáng)的斥力屏障,可阻止相鄰液滴緊密靠近。球形蛋白質(zhì)(乳蛋白)吸附層的界面結(jié)構(gòu)有很大不同,可以看作是一個(gè)二維排列的緊湊顆粒層。蛋白質(zhì)聚集體的吸附或蛋白質(zhì)與多糖相互作用后的混合吸附會(huì)產(chǎn)生不均勻的吸附層或多重吸附層,具有更復(fù)雜的界面結(jié)構(gòu)。蛋白質(zhì)吸附層的結(jié)構(gòu)區(qū)別可通過(guò)蛋白質(zhì)的表面剪切流變性差異進(jìn)行表征。酪蛋白的吸附層呈液體狀,容易移動(dòng),球狀蛋白的單吸附層剛性更強(qiáng),具有二維凝膠或玻璃態(tài)的性質(zhì)[44-45]。

1.3 蛋白質(zhì)與多糖復(fù)合顆粒的協(xié)同穩(wěn)定作用

通過(guò)對(duì)膠體顆粒的表面進(jìn)行疏水改性,可改善顆粒的潤(rùn)濕性,增強(qiáng)乳液的穩(wěn)定性。疏水改性可通過(guò)加入小分子的表面活性劑,如十二烷基磺酸鈉(SDS)、吐溫系列(Tween 20、40、60、80)的乳化劑等[48-49]。為避免加入小分子表面活性劑而改善顆粒潤(rùn)濕性的方法是,加入兩種帶相反電荷的納米顆粒,通過(guò)異種電荷的吸引聚合改善顆粒的潤(rùn)濕性,顆粒混合物呈絮凝狀分散在水介質(zhì)中,靜電荷足夠低,充分疏水吸附在油滴表面使其穩(wěn)定,從而穩(wěn)定乳液[50-51]。

2 固體顆粒的制備方法與性質(zhì)表征

2.1 反溶劑沉淀法

最常用的制備固體顆粒的方法為反溶劑沉淀法,又稱為液液分散法或相分離法。Patel等[52]采用反溶劑沉淀法制備玉米醇溶蛋白—姜黃素復(fù)合膠體顆粒,透射電鏡結(jié)果表明顆粒呈球形,平均粒徑為100～150 nm;姜黃素在顆粒中的包埋率為86.8%,負(fù)載能力4.1%;通過(guò)差示掃描量熱法和X-射線衍射對(duì)固態(tài)膠體顆粒的研究表明,被包埋的姜黃素表現(xiàn)出非晶性質(zhì);紫外全波長(zhǎng)掃描結(jié)果表明,膠體顆粒對(duì)姜黃素的包埋作用增強(qiáng)了姜黃素的耐光性;另外,Patel等[52]還發(fā)現(xiàn),該顆粒在廣泛的pH范圍內(nèi)(1.2,4.5,6.7和7.4)和在模擬腸道條件下具有良好的膠體穩(wěn)定性;Patel等[52]通過(guò)體外粘膜吸附研究表明,姜黃素在粘膜中150 min的保留率仍在60%以上,Caco-2細(xì)胞粘蛋白的研究進(jìn)一步證實(shí)了玉米醇溶蛋白-姜黃素復(fù)合納米顆粒的粘膜吸附特性。de Folter等[32]采用反溶劑沉淀法制備玉米醇溶蛋白膠體顆粒(ZCP),并首次采用ZCP制備出穩(wěn)定的O/W型Pickering乳液,乳液穩(wěn)定性與顆粒濃度、pH、離子強(qiáng)度有關(guān)。研究表明,未經(jīng)改性的ZCP同時(shí)具有疏水性和親水性,在高于或低于玉米醇溶蛋白等電點(diǎn)(pH6.5)時(shí),在10 mol/L的離子強(qiáng)度下,ZCP在O/W乳液中的三相接觸角在90°左右,可強(qiáng)力吸附于油-水界面,可以制備穩(wěn)定的、不含表面活性劑的乳液,該乳液經(jīng)高速剪切分散器13500 r/min,2 min的混合分散后,乳液的液滴粒徑范圍為10～200 μm。Zou等[53]采用液液分散法制備玉米醇溶蛋白-蔓越莓原花青素(Z-CPs)復(fù)合納米顆粒,結(jié)果表明,隨著CPs在Z-CPs中的比例由1∶8增加至1∶2,Z-CPs納米顆粒的直徑由392 nm增加至447 nm,包埋率由10%增加至86%。掃描電鏡結(jié)果表明,Z-CPs納米顆粒呈球形;傅里葉變換紅外光譜研究表明,Z與CPs之間的交互作用是氫鍵和疏水相互作用;通過(guò)人類前骨髓性白血病HL-60細(xì)胞的細(xì)胞培養(yǎng)研究表明,與CPs相比,包封在納米顆粒中的CPs降低了細(xì)胞毒性。

2.2 超臨界流體技術(shù)

Hu等[54]采用超臨界流體技術(shù)(SEDS)通過(guò)增強(qiáng)溶液的分散性能用于制備玉米醇溶蛋白-葉黃素(Z-L)納米顆粒。SEDS的壓力、溫度、葉黃素與玉米醇溶蛋白的比率、溶液流速等對(duì)負(fù)載量、包封率、平均粒徑、顆粒形態(tài)產(chǎn)生顯著影響。較低的溫度和流速結(jié)合高的壓力,能制備粒徑更小,更規(guī)則的球形顆粒。當(dāng)工藝參數(shù)為壓力10 MPa,L與Z的質(zhì)量比為1∶18,45 ℃下,控制溶液流速1.0 mL/min,能夠獲得粒徑尺寸范圍較小、具有緩釋能力的Z-L納米顆粒。

2.3 熱處理結(jié)合靜電絡(luò)合作用

最近的研究表明,球狀蛋白和帶電多糖的復(fù)合納米顆粒可通過(guò)熱處理結(jié)合靜電絡(luò)合作用制備。有兩種制備方法:一是在高于其熱變性溫度的條件下加熱球狀蛋白溶液形成蛋白顆粒,然后加入離子多糖,調(diào)整溶液條件,以促進(jìn)多糖與蛋白質(zhì)顆粒的靜電絡(luò)合[55];二是蛋白質(zhì)-多糖先在室溫下通過(guò)靜電作用形成復(fù)合物,然后在高于其熱變性溫度的條件下加熱此復(fù)合物,以促進(jìn)蛋白質(zhì)聚集和微粒形成。這兩種方法都能形成非常小的生物聚合物顆粒,具有良好的穩(wěn)定性,不易沉淀,不易受pH和離子強(qiáng)度的影響[56-57]。

Peinado等[58]采用熱處理的乳鐵蛋白(LF)與陰離子多糖(海藻酸鹽、卡拉膠、果膠)通過(guò)靜電絡(luò)合作用制備生物聚合物復(fù)合膠體顆粒,并研究了顆粒穩(wěn)定性和形態(tài)特征。在高于LF的變性溫度下(91 ℃,20 min)加熱LF溶液(0.2% LF,pH7),可促進(jìn)蛋白質(zhì)的伸展,抑制蛋白質(zhì)聚集,形成蛋白質(zhì)顆粒,粒徑范圍為200～400 nm,等電點(diǎn)約為8.5。將該蛋白質(zhì)顆粒與陰離子多糖在pH8時(shí)混合,然后降低pH,通過(guò)靜電作用促進(jìn)多糖沉積在蛋白顆粒表面形成復(fù)合膠體顆粒。使用濁度儀、動(dòng)態(tài)光散射和電泳研究不同pH(2～11)和離子強(qiáng)度(0～200 mmol/L NaCl)對(duì)顆粒穩(wěn)定性的影響。在pH5～pH8的范圍內(nèi)顆粒相對(duì)穩(wěn)定,但在較低pH時(shí)顆粒發(fā)生明顯的聚集,這是因?yàn)榈鞍踪|(zhì)與多糖發(fā)生了靜電中和和橋連絮凝。LF-果膠復(fù)合膠體顆粒,在所研究的鹽濃度范圍內(nèi)都比較穩(wěn)定,但LF-卡拉膠和LF-海藻酸鹽絡(luò)合物在較高鹽濃度時(shí)發(fā)生聚集。

3 影響Pickering乳液穩(wěn)定性的因素

3.1 固體顆粒的潤(rùn)濕性

Pickering乳液的類型和傳統(tǒng)乳液類似,包括O/W、W/O、O/W/O、W/O/W等多種乳液[59]。Finkle[60]指出,Pickering乳液的穩(wěn)定性很大程度上取決于固體顆粒的部分潤(rùn)濕性,即要求顆粒具有親水和親油兩親特性,如果顆粒完全溶解于水或油,它們就會(huì)分散在兩相中的一相中,不能吸附在油-水界面,在這種情況下,不能制備穩(wěn)定的乳狀液。Finkle還首次描述了顆粒的潤(rùn)濕性及其穩(wěn)定乳液能力之間的相關(guān)性,即根據(jù)油—顆?！缑嫣幍慕佑|角度θ判斷乳液的類型和穩(wěn)定性(圖2)。固體顆粒在油-顆粒-水界面的接觸角θ<90°時(shí)為O/W型乳液,而θ>90°時(shí)為W/O型乳液,θ=90°時(shí)乳液穩(wěn)定性最好。

圖2 油—顆?！缑嫣幍慕佑|角圖示[60]Fig.2 Position of Pickering-type stabilizers ata planar o/w interface for contact angles[60]

3.2 固體顆粒在油—水界面的吸附形式

固體顆粒與界面強(qiáng)烈的吸附作用形成了具有剛性的界面,而界面的剛性也決定了液滴抗絮凝的能力。吸附在界面的顆粒之間橫向的交互作用也是調(diào)節(jié)界面性質(zhì)與維持乳液穩(wěn)定的非常重要的因素。當(dāng)兩個(gè)被顆粒吸附的液滴相互靠近時(shí),顆粒在界面可能會(huì)產(chǎn)生不同的分布,從而影響乳液的穩(wěn)定性。兩個(gè)在界面緊密排列的單顆粒層將相鄰分散相分割(圖3A),這是球形顆粒均一、單層吸附在界面用于穩(wěn)定Pickering乳液的理想模型,但是即便通過(guò)高壓均質(zhì)或高強(qiáng)度超聲處理也很難實(shí)現(xiàn),因?yàn)轭w粒通常是多分散性的[61-62]。已有研究表明,液滴即使不被顆粒完全包裹也能制備穩(wěn)定的Pickering乳液,這就說(shuō)明顆粒在界面的分布還存在其他的形式,如單層顆粒緊密排列,在相鄰液滴間形成橋連的致密吸附層,單個(gè)顆粒同時(shí)與兩個(gè)液滴吸附,但每個(gè)顆粒的主要部分仍處于連續(xù)的水相中(圖3B)[63]。這種單層排列的顆粒層能夠穩(wěn)定Pickering乳液,是因?yàn)轭w粒層產(chǎn)生空間阻礙作用,阻止大的顆粒脫離液滴或進(jìn)入液滴內(nèi)部。大多數(shù)固體粒子具有比較均勻的表面,這意味著顆粒吸附的液滴表面具有類似顆粒表面的性質(zhì)。接觸角有利于強(qiáng)烈吸附在油-水界面,這也意味著顆粒在乳液中以弱聚集的狀態(tài)存在。因此,顆粒在界面的分布存在第三種形式即顆粒聚集體吸附在液滴表面用于穩(wěn)定Pickering乳液(圖3C)[64-65]。在這種分布形式下,液滴表面不是簡(jiǎn)單的單層或雙層吸附,也不是緊密堆積吸附。相反,顆粒形成的剛性吸附層是無(wú)序的,形成網(wǎng)絡(luò)結(jié)構(gòu)吸附在油-水界面上,能夠通過(guò)分子間引力使整個(gè)聚集結(jié)構(gòu)保持在一起從而阻止液滴聚集。

圖3 固體顆粒在油—水界面的分布形式示意圖Fig.3 a schematic distribution diagram of thesolid particles in the oil-water interface

3.3 固體顆粒的形狀

顆粒的形狀對(duì)顆粒在液滴表面的覆蓋率及與形狀有關(guān)的界面交互作用產(chǎn)生影響。Madivala等[66]研究了顆粒形狀對(duì)Pickering乳液聚集穩(wěn)定性的影響。對(duì)于O/W或W/O乳液,作者發(fā)現(xiàn)乳液的穩(wěn)定性很大程度上決定于顆粒的長(zhǎng)寬比。當(dāng)具有相似潤(rùn)濕性的球形顆粒或較短的細(xì)長(zhǎng)顆粒不能有效穩(wěn)定乳液時(shí),足夠長(zhǎng)的顆粒是非常有效的乳化劑。顆粒的長(zhǎng)寬比對(duì)乳液穩(wěn)定性的影響可通過(guò)測(cè)定油-水界面的剪切流變性質(zhì)進(jìn)行表征。

3.4 固體顆粒的濃度

當(dāng)固體顆粒濃度較低時(shí),靜電相互作用在很大程度上受到抑制,由于顆粒較少,相鄰液滴間共享吸附的顆?；虼蠓肿?起初形成的液滴迅速結(jié)合,通常發(fā)生某種程度的絮凝,直到液滴表面有足夠的顆粒或分子吸附形成空間保護(hù)層[67]。當(dāng)顆粒濃度較高時(shí),乳液穩(wěn)定性主要由界面張力決定。隨著顆粒濃度的提高,顆粒在油-水界面吸附能力增強(qiáng),引起界面張力降低,從而使液滴粒徑逐漸減小。繼續(xù)增加顆粒濃度,顆粒不再吸附于界面,而是進(jìn)入連續(xù)相中,液滴粒徑基本保持不變,但水相黏度逐漸增加,乳液呈凝膠狀,阻止乳液分層、絮凝或聚集,乳液穩(wěn)定性明顯增強(qiáng)[68]。

3.5 pH

固體顆粒可能在不同pH的產(chǎn)品中使用,在通過(guò)人體胃腸道時(shí)pH也不同,因此,探討pH對(duì)乳液的影響是非常重要的。pH的變化能夠改變顆粒的潤(rùn)濕性和靜電性質(zhì),從而影響顆粒的界面吸附。Luo等[34]研究了pH對(duì)黃酮類化合物(山奈酚,蘆丁和柚皮苷)制備的O/W型Pickering乳液的影響。研究表明,在較高的pH時(shí)蘆丁穩(wěn)定的乳液液滴的平均尺寸最小(5 μm)。蘆丁和山奈酚在油-水界面的表面活性在pH8時(shí)比pH2時(shí)略有增加。在pH較高時(shí)乳液的穩(wěn)定性增加,這是因?yàn)辄S酮類化合物顆粒的ζ-電勢(shì)顯著增加,改善了顆粒分散性能,增加了液滴的表面電荷。Liang和Tang[36]研究指出,豌豆分離蛋白(PPI)在pH3.0時(shí)以納米顆粒形式存在,粒徑為134～165 nm可用于制備穩(wěn)定的O/W型Pickering乳液。Wen等[69]研究了不同pH(4.2,4.8,5.5,6.2,7.0和7.8)對(duì)纖維素納米晶(CNCs)制備的檸檬烯Pickering乳液的影響,結(jié)果表明隨著pH的增加,液滴表面的ζ-電位由-42.9 mV增加到-54.5 mV,液滴間靜電斥力增加,增強(qiáng)了乳液的穩(wěn)定性。

3.6 離子強(qiáng)度

NaCl溶液加入主要影響顆粒的表面電位,NaCl溶液濃度較低時(shí),會(huì)降低顆粒表面的電位,有助于顆粒在油-水界面的吸附。當(dāng)NaCl濃度過(guò)高時(shí),顆粒表面發(fā)生靜電屏蔽,顆粒聚集,粒徑增加,影響乳液的穩(wěn)定性。de Folter等[32]研究了不同濃度NaCl溶液對(duì)玉米醇溶蛋白膠體顆粒(ZNP)制備的Pickering乳液的影響,結(jié)果表明,ZNP在1 mmol/L的NaCl溶液中親水性較強(qiáng),三相接觸角為98°;1 mmol/L的NaCl溶液使Z疏水性增加,三相接觸角為87°,有利于ZNP在油-水界面的吸附;然而,0.1 mol/L的NaCl溶液使液滴聚集,發(fā)生分層,嚴(yán)重降低了乳液的穩(wěn)定性。

4 Pickering乳液的應(yīng)用

目前還沒(méi)有Pickering乳液制備的市售產(chǎn)品或材料。原因之一是Pickering乳液最近幾年才引起大家的關(guān)注。與傳統(tǒng)表面活性劑穩(wěn)定的乳液相比,Pickering乳液由于不含表面活性劑,能有效避免表面活性劑可能引發(fā)的刺激性、毒性、溶血行為等不利影響,在生命科學(xué)領(lǐng)域有很多潛在的應(yīng)用[70-71]。例如,研究表明固體顆粒在細(xì)胞表面有較強(qiáng)的粘附作用,因此Pickering乳液可作為藥物和具有生物活性物質(zhì)的包埋和傳遞系統(tǒng),并且可達(dá)到緩釋和靶向的效果[72-74];另外,由于固體顆粒吸附在液滴表面產(chǎn)生具有剛性的吸附層,經(jīng)干燥的Pickering乳液可以用于制備固體劑型的生物材料[75-77]。

5 展望

近年來(lái)Pickering乳液的研究成果促進(jìn)了乳液基礎(chǔ)理論的發(fā)展,并且拓展了乳液的實(shí)際應(yīng)用范圍。隨著人們對(duì)Pickering乳液研究興趣的增加,尋求新型、安全、可降解的固體納米顆粒作為乳液的有效穩(wěn)定劑應(yīng)用于食品行業(yè)是食品領(lǐng)域面臨的挑戰(zhàn)。同時(shí),固體顆粒的制備技術(shù)仍需突破,Pickering乳液的穩(wěn)定機(jī)理有待進(jìn)一步研究。

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Research progress in Pickering emulsions stabilized with biomass-based solid nanoparticles

SUN Cui-xia,LIU Fu-guo,YANG Wei,YUAN Fang,GAO Yan-xiang*

(College of Food Science and Nutritional Engineering,China Agricultural University,Beijing 100083,China)

Pickering emulsions prepared by natural,renewable and biodegradable solid particles have become a hot topic. Present studies have indicated that the stability of Pickering emulsions depended largely on the nature of the solid particles. Therefore,the types,fabrication and characterization of solid particles were reviewed in this paper,focusing on the stabilization of biological organic particles such as polysaccharides and proteins. The factors affecting the Pickering emulsion stability were summarized and potential applications of Pickering emulsions in life science were also illustrated.

solid particles;Pickering emulsions;characterization stability

2014-12-15

孫翠霞(1987-)，女，博士，研究方向：功能食品研發(fā)，E-mail:scx0728@126.com。

*通訊作者:高彥祥(1961-)，男，博士，教授，研究方向：超臨界加工技術(shù)，E-mail:gyxcau@126.com。

國(guó)家自然基金(31371835)。

TS202.3

A

1002-0306(2015)15-0370-07

10.13386/j.issn1002-0306.2015.15.070