王 娟,程 萌,孔瑞琪,逯文倩,張榮飛,王相友,郭衍銀
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植物精油海藻酸鈉復(fù)合膜對(duì)雙孢蘑菇的抑菌保鮮效果研究
王 娟,程 萌,孔瑞琪,逯文倩,張榮飛,王相友,郭衍銀
(山東理工大學(xué)農(nóng)業(yè)工程與食品科學(xué)學(xué)院,淄博 255049)
為了研究植物精油對(duì)雙孢蘑菇貯藏期主要腐敗菌的抑制效果,該文以新鮮雙孢蘑菇為試驗(yàn)材料,分離、純化并鑒定引起雙孢蘑菇貯藏期腐敗的主要病原菌;通過(guò)體外抑菌活性試驗(yàn),篩選出抑菌效果較好的植物精油,并將此精油應(yīng)用于復(fù)合膜的保鮮試驗(yàn)中,驗(yàn)證其抑菌保鮮效果。通過(guò)對(duì)雙孢蘑菇主要致腐微生物進(jìn)行分離、純化得到9株單菌落,經(jīng)致病性試驗(yàn)得到主要病原真菌為3號(hào)菌,對(duì)該病原菌18S rDNA 序列進(jìn)行進(jìn)化樹(shù)分析,確定其為豐孢木霉菌()。選用姜黃、連翹、桉葉、當(dāng)歸4種精油對(duì)3號(hào)菌菌株進(jìn)行抑菌活性試驗(yàn),篩選出較優(yōu)精油種類(lèi)及濃度。結(jié)果表明,桉葉油對(duì)豐孢木霉菌的抑制效果最好,其次是連翹油,姜黃油和當(dāng)歸油無(wú)明顯抑制作用。桉葉油最小抑菌濃度(minimum inhibitory concentration, MIC)為0.312 5L/mL,最小殺菌濃度(minimum bactericidal concentration, MBC)為0.625L/mL;連翹油MIC為0.625L/mL,MBC為1.25L/mL。通過(guò)對(duì)海藻酸鈉/桉葉油復(fù)合膜和海藻酸鈉單一膜的性能指標(biāo)進(jìn)行測(cè)定和對(duì)比發(fā)現(xiàn),桉葉油的添加可顯著提高膜的氣體阻隔性能和機(jī)械性能。分別用海藻酸鈉/桉葉油復(fù)合膜、海藻酸鈉單一膜和普通PE膜對(duì)雙孢蘑菇進(jìn)行保鮮試驗(yàn),結(jié)果表明,添加桉葉油的復(fù)合膜可有效降低雙孢蘑菇子實(shí)體的衰老和致病腐爛,具有顯著的抑菌保鮮效果。該研究結(jié)果可為雙孢蘑菇貯藏期防腐和天然殺菌保鮮劑的選擇提供一定的理論依據(jù)。
病原菌;精油;膜;雙孢蘑菇;抑菌;保鮮
雙孢蘑菇()是世界范圍內(nèi)種植最廣泛的一種食用菌,富含多種營(yíng)養(yǎng)物質(zhì),如甘露醇、維生素、菌糖、有機(jī)堿等,是典型的高蛋白、低脂肪、低能量的菌類(lèi)保健食品[1]。新鮮雙孢蘑菇子實(shí)體潔白,含水率高,無(wú)明顯的保護(hù)組織,貨架期短[2],其本身作為一營(yíng)養(yǎng)體很容易受到侵害,尤其是在生長(zhǎng)成熟期間,易發(fā)生病變,常表現(xiàn)性狀為褐斑、腐爛等,嚴(yán)重影響其口感和食用價(jià)值,同時(shí)也很大程度上影響了其商品價(jià)值[3],對(duì)于消費(fèi)者和生產(chǎn)商來(lái)說(shuō)都是不利的。食用菌貯藏期間的腐爛、病變多是由致病微生物的侵染引起的,目前對(duì)食用菌病原菌的研究多集中在種植期間。張春蘭等[3]研究了雙孢蘑菇褐腐病病原菌有害疣孢霉菌的傳播途徑及其核相;陳少珍等[4]分離鑒定了蘑菇黑斑病病原菌為黑根霉菌;Graupner等[5]通過(guò)質(zhì)譜成像及基因組分析研究了雙孢蘑菇軟腐病病原菌中抗真菌毒力因子的特征;羅秀俊等[6]分離鑒定了香菇爛筒病的主要病原菌為哈茨木霉菌。迄今對(duì)引起雙孢蘑菇貯藏期病害的病原菌相關(guān)報(bào)道較少。
植物精油,是植物體內(nèi)一類(lèi)重要的次生代謝產(chǎn)物,通過(guò)蒸餾、壓榨等方式從草本植物的花、果實(shí)、種子等中萃取提煉出來(lái)[7],具有抑菌、抗氧化、抗病毒等作用,因此,在食品、醫(yī)藥、農(nóng)業(yè)等方面得到了應(yīng)用和發(fā)展[8]。研究表明植物精油類(lèi)物質(zhì)大多具有殺菌、防腐的作用,對(duì)食品中常見(jiàn)的鏈格孢菌、鐮刀菌和霉菌中青霉、曲霉、根霉等真菌都具有很強(qiáng)的抑殺作用[9-14]。姜黃為姜科屬,多年生草本植物,具有良好的抗炎鎮(zhèn)痛及體外抗氧化活性[15];連翹屬于木犀科連翹屬植物,作為常用的傳統(tǒng)中藥之一,具有清熱解毒、抗菌利尿、散結(jié)消腫的功效[16];桉葉油是從桉樹(shù)油、玉樹(shù)油、樟腦油、月桂葉油等物質(zhì)中提取而來(lái),具有殺菌消炎的作用[17];當(dāng)歸為傘形科植物,具有擴(kuò)張外周血管,降血壓的作用[18]。以往人們多是對(duì)這4種精油的藥用價(jià)值進(jìn)行研究,而在果蔬保鮮研究中的報(bào)道較少,因此,本文針對(duì)精油的抑菌活性、抗氧化活性及其在保鮮方面的應(yīng)用進(jìn)行研究,以期為植物精油資源的抑菌保鮮應(yīng)用提供依據(jù)。
本試驗(yàn)擬對(duì)從腐爛雙孢蘑菇分離得到的微生物進(jìn)行純化,將純化后的菌株接種于健康雙孢蘑菇進(jìn)行致病性試驗(yàn),對(duì)主要病原菌菌株進(jìn)行測(cè)序,確定其種屬。選用姜黃、連翹、桉葉、當(dāng)歸4種精油進(jìn)行抑菌活性試驗(yàn),篩選出針對(duì)雙孢蘑菇病原菌抑制效果較好的植物精油,并采用精油復(fù)合膜進(jìn)行保鮮驗(yàn)證試驗(yàn),旨在為雙孢蘑菇貯藏期防腐保鮮以及天然殺菌保鮮劑的選擇提供一定的理論依據(jù)。
新鮮雙孢蘑菇采自山東省淄博市臨淄區(qū),采后立即運(yùn)至山東理工大學(xué)實(shí)驗(yàn)冷庫(kù),(4±1)℃下預(yù)冷12 h備用。
姜黃、連翹、桉葉、當(dāng)歸精油(江西省吉安市國(guó)光香料廠(chǎng));海藻酸鈉(天津市光復(fù));UNIQ柱式DNA膠回收試劑盒(上海生工)。
BSC-150型恒溫恒濕箱(上海博訊);XA.XT plus質(zhì)構(gòu)儀(英國(guó)Stable Micro System公司);LDZF-50KB-H型立式壓力蒸汽滅菌器(上海申安);SHP-300型智能生化培養(yǎng)箱(上海三發(fā));TGL-20M高速臺(tái)式冷凍離心機(jī)(湖南湘儀);BCN-1360型生物超凈工作臺(tái)(哈爾濱東聯(lián)電子);DYY-5型穩(wěn)壓穩(wěn)流電泳儀(北京六一);Bio- RadVersaDoc3000 凝膠成像儀(上海和美國(guó)際貿(mào)易有限公司);2720 PCR儀(AB1公司);3730測(cè)序列分析儀(美國(guó)Applied BioSystems公司)。
1.3.1 病原菌的培養(yǎng)和分離
參考杜小琴等[19]的方法,并略有修改:對(duì)腐爛變質(zhì)的部位采用組織分離法進(jìn)行病癥分組。在病健交接處切取約2 mm的組織,用75%的酒精進(jìn)行消毒10 s,無(wú)菌水沖洗3次后于馬鈴薯葡萄糖瓊脂培養(yǎng)基(PDA)中,25 ℃下培養(yǎng)純化。
1.3.2 致病性試驗(yàn)
1)真菌孢子懸浮液的制備
參照周德慶的方法[20],取25℃下培養(yǎng)10 d的帶菌PDA平皿1個(gè),加入含0.05% 吐溫80的無(wú)菌水10 mL,用鑷子挑取平板的病原菌孢子,轉(zhuǎn)入50 mL三角瓶中,在旋渦振蕩器(XW-80A型,上海黃浦滬西儀器廠(chǎng))振蕩15 s后,用4層紗布濾去菌絲,再用血球計(jì)數(shù)板計(jì)數(shù)算出孢子懸浮液的濃度,最后稀釋至所需濃度106CFU/mL。
2)細(xì)菌菌懸液的制備
采用平板菌落計(jì)數(shù)法[20],用無(wú)菌牙簽將供試細(xì)菌接入50 mL無(wú)菌水中,振蕩30 min,稀釋菌懸液,用微量可調(diào)移液器(法國(guó)吉爾森公司)分別吸取標(biāo)記10-4、10-5、10-6菌懸液各200L,轉(zhuǎn)接至無(wú)菌平皿中涂布,37℃培養(yǎng)48 h,平板計(jì)數(shù)。計(jì)算方法如式(1)
3)致病性試驗(yàn)
霉菌制備106CFU/mL微生物孢子懸液,細(xì)菌則為105CFU/mL的細(xì)胞懸液,通過(guò)噴霧接種在新鮮健康的雙孢蘑菇上,每種處理10個(gè)蘑菇,重復(fù)3次。接種后的雙孢蘑菇用普通PE保鮮膜單層包裝,于4℃實(shí)驗(yàn)冷庫(kù)暗培養(yǎng)(相對(duì)濕度85%±5%)。觀察并記錄新鮮雙孢蘑菇的發(fā)病情況,顯癥后與原腐爛雙孢蘑菇進(jìn)行對(duì)比鑒定,一致則可以確定是該病原菌。
1.3.3 形態(tài)學(xué)鑒定
挑取少量的目標(biāo)菌株接種于PDA培養(yǎng)基,25℃培養(yǎng)72 h觀察菌落形態(tài),并用乳酸石碳酸棉蘭染色劑(上海生工)染色,觀察個(gè)體形態(tài)。
1.3.4 18S rDNA鑒定菌種
1)選擇合適的特異性引物
ITSl (5¢-TCCGTAGGTGAACCTGCGG-3¢),ITS4 (5¢-TCCTCCGCTTATTGATATGC-3¢)。
2)擴(kuò)增目標(biāo)區(qū)序列
擴(kuò)增體系:
10×taq Buffer(Takara公司),10L;dNTP MIX(Takara公司),1L;ITS1(泓迅公司合成引物),2L;ITS4(泓迅公司合成引物),2L;菌樣,5L;Taq酶(Takara公司),2L;加去離子水至50L。
反應(yīng)條件:96℃,5 min;(96℃、30 s; 58℃、30 s;72℃、30 s)×35 cycles;72℃,7 min;4℃∝。
3)PCR產(chǎn)物純化
4)PCR產(chǎn)物克隆測(cè)序
5)同源性分析與進(jìn)化樹(shù)的構(gòu)建
采用核酸BLAST技術(shù),將測(cè)序獲得的序列信息與美國(guó)國(guó)立生物技術(shù)信息中心(National Center for Biotechnology Information, NCBI)網(wǎng)站的Gen Bank數(shù)據(jù)庫(kù)進(jìn)行對(duì)比,得到與所測(cè)序列同源性較高的已知分類(lèi)地位的菌種,然后將已知菌株與所測(cè)菌株的18S rDNA序列一起,應(yīng)用Meg Align(Clustal w)進(jìn)行比對(duì),繪制進(jìn)化樹(shù)。
1.3.5 抑菌活性試驗(yàn)
1)不同精油的抑菌效果
采用濾紙片法[21-23]進(jìn)行測(cè)定。分別用100L的姜黃、連翹、桉葉、當(dāng)歸4種不同種類(lèi)精油浸漬無(wú)菌濾紙片(直徑6 mm)2 h。吸取30L濃度為106CFU/mL的孢子懸液,均勻涂布于PDA培養(yǎng)基,于25℃下培養(yǎng),3個(gè)平行對(duì)照,3次重復(fù)。48 h后,用游標(biāo)卡尺測(cè)量包圍平板周?chē)囊种茀^(qū)(zones of inhibition,ZOI)的直徑(包括濾紙片的直徑)記錄。以體積分?jǐn)?shù)10%的吐溫80作為對(duì)照。計(jì)算方法如式(2)
2)最小抑菌濃度(minimum inhibitory concentration, MIC)和最小殺菌濃度(minimum bactericidal concentration, MBC)的測(cè)定
對(duì)于具有較好抑菌活性的植物精油,采用試管二倍稀釋法[24]測(cè)定其MIC。用體積分?jǐn)?shù)10%的吐溫80將植物精油稀釋成不同濃度梯度的稀釋液,每支試管分別加入100L 106CFU/mL制備好的菌懸液。設(shè)立不加精油的空白對(duì)照組。25℃振蕩培養(yǎng)48 h,每組處理3個(gè)平行,3次重復(fù)。用“+”表示有菌生長(zhǎng),“-”表示無(wú)菌生長(zhǎng),MIC為試管內(nèi)無(wú)菌的最小精油濃度。
將上述100L精油有效抑菌濃度藥液接入空白PDA固體培養(yǎng)基上涂布均勻,于25℃恒溫培養(yǎng)48 h,觀察培養(yǎng)基上有無(wú)菌物生長(zhǎng),以培養(yǎng)皿中計(jì)數(shù)減少99.9%原始菌落的精油濃度作為MBC[24]。
1.3.6 膜的制備及性能測(cè)定
1)膜的制備
參考湯秋冶等[25]的方法:稱(chēng)取2 g海藻酸鈉粉末緩慢加入到90 mL的蒸餾水中,80℃水浴攪拌至膜液澄清。然后冷卻至室溫(25℃),分別加入1 mL的甘油和0.7 mL的精油(海藻酸鈉單一膜不加入精油)。調(diào)節(jié)膜液pH值為6.5,然后定容至100 mL,用磁力攪拌器(HJ-4型,崢嶸儀器廠(chǎng))以2 000 r/min 攪拌30 min,于4℃下靜置過(guò)夜。第2天將100 mL 的膜液倒在水平的玻璃模具(100 mm× 100 mm)內(nèi),50℃干燥12 h(必須保證玻璃板的水平性)后,取出模具,加入2%的氯化鈣,交聯(lián)120 s,最后室溫下放置12 h,揭膜。
2)膜的物理和力學(xué)性能測(cè)定
膜的水蒸氣透過(guò)率(water vapor transmission rate,WVTR)和透氧率參考ASTM[26]的方法測(cè)定,機(jī)械性能參考羅寧寧[27]的方法測(cè)定。
1.3.7 不同包裝膜對(duì)雙孢蘑菇保鮮效果試驗(yàn)
分別用制備好的精油復(fù)合膜、海藻酸鈉單一膜和普通PE膜將新鮮雙孢蘑菇包裝起來(lái),無(wú)包裝處理作為空白對(duì)照,將4組不同處理的雙孢蘑菇同時(shí)放入4℃的冷庫(kù)中貯藏,分別在貯藏的第0、3、6、9、12天測(cè)量蘑菇的失質(zhì)量率、硬度、菇皮白度、菇肉白度、細(xì)胞膜透性和菌落總數(shù)等指標(biāo)。
1.3.8 測(cè)定指標(biāo)及方法
1)失質(zhì)量率[28]
式中1為貯藏前雙孢蘑菇質(zhì)量,g;2為貯藏后雙孢蘑菇質(zhì)量,g。
2)硬度
用果實(shí)硬度計(jì)(GY-1型,牡丹市機(jī)械研究所)測(cè)定雙孢蘑菇的硬度。將硬度計(jì)垂直于雙孢蘑菇表面,勻速將壓頭壓入子實(shí)體內(nèi)約5 mm,以指針讀數(shù)作為雙孢蘑菇的硬度值[29]。
3)白度值
雙孢蘑菇子實(shí)體切面的白度值用自動(dòng)色差計(jì)(SC-80型,北京康光儀器有限公司)進(jìn)行測(cè)定,用表示[30]。
4)細(xì)胞膜透性
參考張榮飛等[28]的方法,用電導(dǎo)率儀(DDB-6200型,上海雷磁新涇儀器有限公司)測(cè)定浸提液的電導(dǎo)率。
5)菌落總數(shù)
參照GB/T 4789.2-2016《食品衛(wèi)生微生物學(xué)檢驗(yàn)菌落總數(shù)測(cè)定》測(cè)定菌落總數(shù)[31],結(jié)果單位以lg CFU/g表示。取5 g樣品置于45 mL無(wú)菌生理鹽水中,8 000 r/min均質(zhì)2 min,得到1:10樣品勻液。用無(wú)菌吸管吸取1 mL樣品勻液緩慢注于盛有9 mL無(wú)菌生理鹽水的無(wú)菌試管中,得到1:100樣品勻液,依次制備一系列不同濃度梯度的樣品勻液。選取2~3個(gè)適宜稀釋度樣品勻液,各吸取100L于無(wú)菌PDA培養(yǎng)基中,均勻涂布,25℃恒溫培養(yǎng)48 h。
根據(jù)科赫法則,從腐爛雙孢蘑菇分離純化病原菌(圖1),最終得到9株單菌落,通過(guò)形態(tài)學(xué)鑒定,分別為3種霉菌和2種細(xì)菌?;亟又虏⌒则?yàn)證試驗(yàn),確定雙孢蘑菇的主要致腐病原菌為3號(hào)菌。將3號(hào)菌菌株于25℃下PDA培養(yǎng)基中培養(yǎng)3 d的菌落形態(tài)如圖2a所示,顯微特征觀察(×400)如圖2b所示。
圖1 雙孢蘑菇貯藏期病發(fā)病癥狀、原菌分離和菌落形態(tài)
圖2 病原菌菌株
3號(hào)菌菌落呈棉絮狀,開(kāi)始為白色且膨松,后從菌落中央產(chǎn)生綠色孢子,菌盤(pán)逐漸變成綠色,產(chǎn)孢區(qū)有菌絲輪紋,帶有特殊氣味。菌體可沿培養(yǎng)基表面蔓延生長(zhǎng),培養(yǎng)基背面呈綠色。孢子近似球形,透明。
用質(zhì)量分?jǐn)?shù)1%的瓊脂糖凝膠對(duì)3號(hào)菌菌株的18S rDNA擴(kuò)增產(chǎn)物電泳檢測(cè),經(jīng)溴乙錠染色后,在560 bp附近出現(xiàn)熒光條帶(圖3),與預(yù)期結(jié)果一致。
分析18S rDNA序列可得,該病原菌與木霉屬微生物保守序列相似度最高。進(jìn)化樹(shù)如圖4所示,3號(hào)病原菌與豐孢木霉菌()親緣關(guān)系較近,與哈茨木霉菌()也比較近,但與黑甲肉座菌()親緣關(guān)系較遠(yuǎn)。因此可以推斷,3號(hào)病原菌為豐孢木霉菌()。
注:泳道1、2:3號(hào)菌的PCR擴(kuò)增產(chǎn)物,其中泳道1上樣量1 μL,泳道2上樣量2 μL;泳道M:DNA ladder。
圖4 3號(hào)菌和相關(guān)菌株的系統(tǒng)進(jìn)化樹(shù)
表1為不同植物精油的抑菌圈直徑大小,通過(guò)比較可以得到,桉葉油對(duì)豐孢木霉菌的抑制效果最好,其次是連翹油,姜黃油和當(dāng)歸油無(wú)明顯抑制作用。因此以桉葉油和連翹精油為主要研究對(duì)象測(cè)定其MIC和MBC。
表1 不同植物精油的抑菌圈直徑
表2為不同精油濃度的抑菌效果,由表2可以看出,桉葉油的MIC為0.312 5L/mL,MBC為0.625L/mL;連翹精油的MIC為0.625L/mL,MBC為1.25L/mL。雖然桉葉油與連翹油都具有抑菌活性,但桉葉油針對(duì)豐孢木霉菌的抑制效果更好,這可能與其成分1,8-桉葉油素有關(guān)[32]。因此,選擇桉葉油制備復(fù)合保鮮膜,并進(jìn)行性能比較試驗(yàn)和雙孢蘑菇保鮮應(yīng)用試驗(yàn)。
表2 不同精油濃度的抑菌效果
注:“+”表示有菌生長(zhǎng),“-”表示無(wú)菌生長(zhǎng)。
Note: “+” indicates fungus growth, “-” indicates no fungus growth.
2.3.1 膜理化參數(shù)
表3為海藻酸鈉/桉葉油復(fù)合膜與海藻酸鈉單一膜的性能比較。
表3 海藻酸鈉/桉葉油復(fù)合膜與海藻酸鈉單一膜參數(shù)
由表3可以看出,海藻酸鈉/桉葉油復(fù)合膜的水蒸氣透過(guò)率和氧氣透過(guò)率均顯著低于海藻酸鈉單一膜,說(shuō)明桉葉油的添加增強(qiáng)了膜的氣體阻隔性能,這可能是由于桉葉油均勻分散在復(fù)合膜中,與膜液發(fā)生分子相互作用[27],增加了膜的厚度和致密性。由表3還可以看出,海藻酸鈉/桉葉油復(fù)合膜的拉伸強(qiáng)度和斷裂伸長(zhǎng)率均顯著高于海藻酸鈉單一膜,說(shuō)明桉葉油的添加提高了復(fù)合膜的機(jī)械性能,這可能與精油類(lèi)物質(zhì)干燥成膜后的力學(xué)特性有關(guān)。
2.3.2 失質(zhì)量率
失質(zhì)量率可直觀反映雙孢蘑菇的新鮮度。雙孢蘑菇在采后貯藏中,子實(shí)體品質(zhì)降低,由于雙孢蘑菇含水率較高,又因?yàn)楸砻鏌o(wú)明顯保護(hù)組織,失質(zhì)量主要是失水造成的。失水率大于5%,子實(shí)體即變蔫變軟,新鮮程度降低[28]。不同處理雙孢蘑菇失質(zhì)量率的變化如圖5所示,在整個(gè)貯藏過(guò)程中,4種不同包裝方式處理下,雙孢蘑菇的失質(zhì)量率均呈現(xiàn)不斷上升的趨勢(shì),空白對(duì)照組的失質(zhì)量率在第6天就已高達(dá)7.7%,菌體皺縮嚴(yán)重,普通PE膜和海藻酸鈉單一膜處理均可減緩雙孢蘑菇的失水,但2種處理無(wú)顯著差異(<0.05)。貯藏第12 天時(shí),海藻酸鈉/桉葉油復(fù)合膜處理的雙孢蘑菇失質(zhì)量率僅為3.51%,顯著低于其他處理。這是由于海藻酸鈉/桉葉油復(fù)合膜具有較低的水蒸氣透過(guò)率,可有效減少包裝內(nèi)水蒸氣的散失,較好地維持了雙孢蘑菇貯藏環(huán)境的高濕度要求,降低了雙孢蘑菇子實(shí)體水分的散失。
圖5 不同處理對(duì)雙孢蘑菇貯藏期間失質(zhì)量率的影響
2.3.3 硬度
硬度反映了子實(shí)體的成熟衰老。在貯藏期內(nèi),雙孢蘑菇的硬度會(huì)隨著細(xì)胞膨壓下降、細(xì)胞壁逐漸降解等因素不斷下降[33]。圖6顯示了貯藏過(guò)程中雙孢蘑菇硬度的變化,在整個(gè)貯藏過(guò)程中,各處理雙孢蘑菇子實(shí)體的硬度隨貯藏時(shí)間的延長(zhǎng)不斷降低,這可能與果膠酶的催化作用有關(guān),原果膠不斷分解,在細(xì)胞滲透壓的作用下,被細(xì)胞液溶解,導(dǎo)致菌體硬度減小。在貯藏第12 天海藻酸鈉單一膜處理組雙孢蘑菇硬度由原始的0.94 N/mm2下降到0.52 N/mm2,而海藻酸鈉/桉葉油復(fù)合膜處理的樣品硬度為0.58 N/mm2。在整個(gè)貯藏期內(nèi),復(fù)合膜處理的雙孢蘑菇硬度均顯著高于其他3組。
圖6 不同處理對(duì)雙孢蘑菇貯藏期間硬度的影響
2.3.4 白度值
白度是評(píng)價(jià)雙孢蘑菇商品價(jià)值比較重要也是較為直觀的指標(biāo),采后雙孢蘑菇在貯藏過(guò)程中會(huì)因組織中的多種酚類(lèi)物質(zhì)氧化引起褐變。此外,雙孢蘑菇表面的一些微生物也會(huì)導(dǎo)致蘑菇上產(chǎn)生深褐色的斑點(diǎn)。Gormley[34]將蘑菇的白度分為2類(lèi):白度大于等于86的為好品質(zhì)菇,在80~85之間的為可接受品質(zhì)。試驗(yàn)比較了不同包裝處理的雙孢蘑菇在貯藏期間菇皮和菇肉白度的變化情況。圖7a為不同處理對(duì)雙孢蘑菇貯藏期間菇皮白度的影響,由圖7a可看出,海藻酸鈉/桉葉油復(fù)合膜處理的雙孢蘑菇品質(zhì)要優(yōu)于其他3組處理。對(duì)照組雙孢蘑菇菇皮的白度在第3天就低于85,菇皮有黏著現(xiàn)象,商品價(jià)值嚴(yán)重降低,而復(fù)合膜處理的雙孢蘑菇菇皮白度值在第6天仍高于86,為好品質(zhì)菇。普通PE膜包裝和海藻酸鈉包裝的雙孢蘑菇菇皮白度值在第12天均已低于80,為不可接受品質(zhì),復(fù)合膜處理組雙孢蘑菇菇皮的白度值最低為82.31,仍然為可接受品質(zhì)。另外,由圖7b可看出,4種不同處理雙孢蘑菇菇肉白度也具有相似變化規(guī)律。通過(guò)方差分析,在相同條件下,海藻酸鈉/桉葉油復(fù)合膜貯藏期內(nèi)菇肉白度均高于其他組,且差異顯著。
圖7 不同處理對(duì)雙孢蘑菇貯藏期間菇皮及菇肉白度的影響
2.3.5 細(xì)胞膜透性
果蔬在貯藏期間經(jīng)歷著一個(gè)后熟的過(guò)程,細(xì)胞膜透性間接反映了果蔬品質(zhì)的衰老和損傷情況[35],隨著細(xì)胞的不斷降解,膜透性不斷增加。圖8為不同處理對(duì)雙孢蘑菇貯藏期間細(xì)胞膜透性的影響,由圖8可以看出,在整個(gè)貯藏過(guò)程中,海藻酸鈉/桉葉油復(fù)合膜處理的雙孢蘑菇膜透性較低。在貯藏第12 天時(shí),對(duì)照組的膜透性高達(dá)73.32%,普通PE膜處理組為68.94%,海藻酸鈉單一膜處理組為65.63%,而復(fù)合膜處理組僅為60.71%。這說(shuō)明海藻酸鈉/桉葉油復(fù)合膜的使用能夠有效地降低脂質(zhì)過(guò)氧化和電解質(zhì)外漏的發(fā)生。
圖8 不同處理對(duì)雙孢蘑菇貯藏期間細(xì)胞膜透性的影響
2.3.6 菌落總數(shù)
雙孢蘑菇感染微生物容易造成子實(shí)體的衰老、品質(zhì)下降等現(xiàn)象,最終導(dǎo)致其軟化腐爛,產(chǎn)生病害和有毒物質(zhì)等。即使低溫干燥的條件下也難以減少微生物侵害,食用菌微生物侵染致病問(wèn)題不容忽視。圖9為不同處理對(duì)雙孢蘑菇貯藏期間菌落總數(shù)的影響,由圖9可以看出,隨著貯藏時(shí)間的延長(zhǎng),4組不同包裝處理的雙孢蘑菇菌落總數(shù)均呈不斷上升趨勢(shì)。對(duì)比可得,不同貯藏期內(nèi),海藻酸鈉/桉葉油復(fù)合膜包裝下的雙孢蘑菇菌落總數(shù)上升較為緩慢,且顯著低于其他3種處理,貯藏結(jié)束時(shí),對(duì)照組雙孢蘑菇的菌落總數(shù)高達(dá)12.33 lg CFU/g,普通PE膜處理下的雙孢蘑菇菌落總數(shù)為10.62 lg CFU/g,海藻酸鈉單一膜處理后的雙孢蘑菇菌落總數(shù)為9.85 lg CFU/g,復(fù)合薄膜處理后的雙孢蘑菇菌落總數(shù)僅為7.77 lg CFU/g,說(shuō)明海藻酸鈉/桉葉油復(fù)合膜可以顯著抑制雙孢蘑菇微生物數(shù)量的增長(zhǎng),可有效防止因感染病害導(dǎo)致的褐變、軟化、腐爛等品質(zhì)下降,保持食用價(jià)值和經(jīng)濟(jì)價(jià)值。對(duì)比Qin等[36]對(duì)雙孢蘑菇的研究情況,海藻酸鈉/桉葉油復(fù)合膜更有效減少貯藏期微生物數(shù)量,直觀反映了該膜的抑菌性,即桉葉油具有較好的抑菌性能。
圖9 不同處理對(duì)雙孢蘑菇貯藏期間菌落總數(shù)的影響
本文對(duì)腐爛雙孢蘑菇中的微生物進(jìn)行分離純化,得到9株單菌落;經(jīng)致病性驗(yàn)證試驗(yàn),確定了雙孢蘑菇貯藏期間主要致病菌為3號(hào)菌菌株;通過(guò)18S rDNA序列分析和繪制進(jìn)化樹(shù)比對(duì),該病原菌為豐孢木霉菌()。
研究了4種植物精油對(duì)雙孢蘑菇主要致病菌的抑制效果,結(jié)果表明,桉葉油的抑菌性最強(qiáng),其次是連翹油,而姜黃油和當(dāng)歸油無(wú)明顯抑菌效果。針對(duì)抑菌效果較好的2種精油深入研究,得到桉葉油的最小抑菌濃度(minimum inhibitory concentration, MIC)為0.312 5L/mL,最小殺菌濃度(minimum bactericidal concentration, MBC)為0.625L/mL;連翹精油的MIC為0.625L/mL,MBC為1.25L/mL。
通過(guò)對(duì)海藻酸鈉/桉葉油復(fù)合膜和海藻酸鈉單一膜的性能指標(biāo)進(jìn)行測(cè)定和對(duì)比發(fā)現(xiàn),桉葉油的添加可顯著提高膜的氣體阻隔性能和機(jī)械性能。通過(guò)雙孢蘑菇保鮮試驗(yàn)說(shuō)明,與海藻酸鈉單一膜相比,添加了桉葉油的復(fù)合膜對(duì)雙孢蘑菇起到顯著的抑菌保鮮效果,可有效延緩貯藏期雙孢蘑菇的失重、衰老和褐變,并對(duì)雙孢蘑菇貯藏期間微生物的感染起到了明顯抑制作用,提高了雙孢蘑菇的商品價(jià)值。本研究結(jié)果可為雙孢蘑菇貯藏期防腐和天然殺菌保鮮劑的選擇提供理論依據(jù)。
[1] 張榮飛,王相友,劉戰(zhàn)麗. 納米TiO2/SiO2復(fù)合膜結(jié)構(gòu)的表征及其對(duì)雙孢蘑菇涂膜保鮮的影響[J]. 現(xiàn)代食品科技,2014,30(9):134-141.Zhang Rongfei, Wang Xiangyou, Liu Zhanli. Structural characterization of a nano-TiO2/SiO2composite film and its preservative effect on agaricus bisporus[J]. Modern Food Science and Technology, 2014, 30(9): 134-141. (in Chinese with English abstract)
[2] 曹冬潔,王相友,王娟. 基于酶動(dòng)力學(xué)方程的雙孢蘑菇氣調(diào)貯藏呼吸速率模型[J]. 農(nóng)業(yè)工程學(xué)報(bào),2016,32(4):284-289. Cao Dongjie, Wang Xiangyou, Wang Juan. Respiration rate model ofbased on enzyme kinetics equation under controlled atmosphere storage[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(4): 284-289. (in Chinese with English abstract)
[3] 張春蘭,徐濟(jì)責(zé),柿島真,等. 雙孢蘑菇疣孢霉病的發(fā)病過(guò)程及病原菌的核相研究[J]. 微生物學(xué)報(bào),2017,57(3):422-433. Zhang Chunlan, Xu Jize, Kakishima Makoto, et al. The development ofwet bubble disease and the nuclear phase of pathogen[J]. Acta Microbiologica Sinica, 2017, 57(3): 422-433. (in Chinese with English abstract)
[4] 陳少珍,黃思良,黃卓忠,等. 蘑菇黑斑病病原菌分離與鑒定[J]. 廣西農(nóng)業(yè)科學(xué),2009,40(1):43-46. Chen Shaozhen, Huang Siliang, Huang Zhuozhong, et al. Isolation and identification of pathogen of mushroom black spot[J]. Guangxi Agricultural Science, 2009, 40(1): 43-46. (in Chinese with English abstract)
[5] Graupner K, Scherlach K, Bretschneider T, et al. Imaging mass spectrometry and genome mining reveal highly antifungal virulence factor of mushroom soft rot pathogen[J]. Angewandte Chemie International Edition, 2012, 51(52): 13173-13177.
[6] 羅秀俊,郭建峰,韓波波,等. 一株香菇病原真菌的分離、鑒定與室內(nèi)防治藥劑篩選[J]. 云南農(nóng)業(yè)大學(xué)學(xué)報(bào):自然科學(xué),2017,32(5):793-804. Luo Xiujun, Guo Jianfeng, Han Bobo, et al. Isolation, id- entification of apathogen and vitro screening of control medicament[J]. Journal of Yunnan Agricultural University: Natural Science, 2017, 32(5): 793-804. (in Chinese with English abstract)
[7] 湯曉倩,劉霞,馮蕊. 植物精油在植物保護(hù)中的應(yīng)用研究進(jìn)展[J]. 安徽農(nóng)業(yè)科學(xué),2016,44(1):211-213. Tang Xiaoqian, Liu Xia, Feng Rui. Research advances of application of plant essential on in plant conservation[J]. Joumal of Anhui Agricultural Science, 2016, 44(1): 211-213. (in Chinese with English abstract)
[8] 胡林峰,許明錄,朱紅霞. 植物精油抑菌活性研究進(jìn)展[J]. 天然產(chǎn)物研究與開(kāi)發(fā),2011,23(2):384-391. Hu Linfeng, Xu Minglu, Zhu Hongxia. Advances in antifungal activity of plant essential oil[J]. Natural Product Research and Development, 2011, 23(2): 384-391. (in Chinese with English abstract)
[9] Zakuan Z, Mustapa S A, Sukor R, et al. Antifungal activity of(temukunci) extract against filamentous spoilage fungi from vegetables[J]. International Food Research Journal, 2018, 25(1): 433-438.
[10] Combrinck S, Regnier T, Gpp K. In vitro activity of eighteen essential oils and some major components against common postharvest fungal pathogens of fruit[J]. Industrial Crops and Products, 2011, 33(2): 344-349.
[11] Starovic M, Ristic D, Pavlovic S, et al. Antifungal activities of different essential oils against anise seeds mycopopulations [J]. Journal of Food Safety and Food Quality-Archiv fur Lebensmittelhygiene, 2016, 67(3): 72-78.
[12] Maqbool M, Ali A, Alderson P G, et al. Postharvest application of gum arabic and essential oils for controlling anthracnose and quality of banana and papaya during cold storage[J]. Postharvest Biology & Technology, 2011, 62(1): 71-76.
[13] Tian J, Ban X, Zeng H, et al. Chemical composition and antifungal activity of essential oil fromCelak[J]. International Journal of Food Microbiology, 2011, 145(2/3): 464-470.
[14] 李寧,關(guān)文強(qiáng),趙麗靜. 丁香精油對(duì)貯藏期圣女果防腐效果初步研究[J]. 天津農(nóng)學(xué)院學(xué)報(bào),2011,18(2):16-19. Li Ning, Guan Wenqiang, Zhao Lijing. Preliminary study on clove oil preventing decay of cherry tomato during storage[J]. Journal of Tianjin Agricultural University, 2011, 18(2): 16-19. (in Chinese with English abstract)
[15] 盧彩會(huì),牟德華. 姜黃油的抗炎鎮(zhèn)痛及體外抗氧化活性[J]. 食品科學(xué),2018,39(1):243-249. Lu Caihui, Mou Dehua. Antiin?ammatory, analgesic and in vitro antioxidant activities of turmeric oil[J]. Food Science, 2018, 39(1): 243-249. (in Chinese with English abstract)
[16] 李亞茹,周林燕,李淑榮,等. 植物精油對(duì)果蔬中微生物的抑菌效果及作用機(jī)理研究進(jìn)展[J]. 食品科學(xué),2014,35(11):325-329.Li Yaru, Zhou Linyan, Li Shurong, et al. Antibacterial activity and mechanism of action of plant essential oils and their main components from fruits and vegetables: A review [J]. Food Science, 2014, 35(11): 325-329. (in Chinese with English abstract)
[17] 秦海燕,葉平,白鳳相,等. 桉葉油對(duì)小鼠肺炎的恢復(fù)治療作用[J]. 中國(guó)獸醫(yī)雜志,2012,48(10):57-58.
[18] 妥海燕,任遠(yuǎn),王志旺,等. 當(dāng)歸揮發(fā)油對(duì)哮喘BALB/c小鼠的平喘作用及對(duì)Th17免疫活性的影響[J]. 中國(guó)應(yīng)用生理學(xué)雜志,2016,32(2):137-141.
[19] 杜小琴,何靖柳,秦文,等. 甜櫻桃果實(shí)采后病原菌的分離鑒定及植物精油抑菌效果研究[J]. 食品工業(yè)科技,2015,36(20):339-343. Du Xiaoqin, He Jingliu, Qin Wen, et al. Isolation and identification of pathogenic bacteria forsweet cherry and antibacterial effect of plant essential oil[J]. Science and Technology of Food Industry, 2015, 36(20): 339-343. (in Chinese with English abstract)
[20] 周德慶. 微生物學(xué)實(shí)驗(yàn)教程[M]. 北京:高等教育出版社,2006.
[21] Gao Z L, Chen Y, Xie Y H. In vitro antimicrobial activity of essential oil from artemisia annua[J]. Food Science, 2010, 31(19): 209-211.
[22] 潘素娟,王長(zhǎng)青,李曉東,等. 邪蒿揮發(fā)油化學(xué)成分的GC- MS分析及抑菌作用[J]. 食品科學(xué),2011,32(24):200-203. Pan Sujuan, Wang Changqing, Li Xiaodong, et al. Chemical composition as analyzed by GC-MC and antibacterial activity of volatile oil from stems and leaves ofhiroe[J]. Food Science, 2011, 32(24): 200-203. (in Chinese with English abstract)
[23] Donato R, Santomauro F, Bilia A R, et al. Antibacterial activity of Tuscan Artemisia annua, essential oil and its major components against some foodborne pathogens[J]. LWT- Food Science and Technology, 2015, 64(2): 1251-1254.
[24] 賈會(huì)玲,黃曉德,錢(qián)驊,等. 9種植物精油及精油單體成分對(duì)黃瓜枯萎病的抑菌活性[J]. 安徽農(nóng)業(yè)科學(xué),2017,45(31):160-162.Jia Huiling, Huang Xiaode, Qian Hua, et al. Antifungal activity of nine essential oils and essential oil monomers against[J]. Joumal of Anhui Agricultural Science, 2017, 45(31): 160-162. (in Chinese with English abstract)
[25] 湯秋冶,潘道東,孫楊贏,等. ε-聚賴(lài)氨酸/海藻酸鈉抗菌復(fù)合膜的制備及性能研究[J]. 中國(guó)食品學(xué)報(bào),2016,16(12):101-107. Tang Qiuye, Pan Daodong, Sun Yangying, et al. Preparation and performance of antimicrobial films based on sodium alginate and ε-poly-L-lysine[J]. Journal of Chinese Institute of Food Science and Technology, 2016, 16(12): 101-107. (in Chinese with English abstract)
[26] Standard test methods for water vapor transmission of materials: ASTM E96/E96M-2016 [S]. 2016-07.
[27] 羅寧寧. 殼聚糖-肉桂精油可食性膜的制備、性能及應(yīng)用研究[D]. 上海:上海應(yīng)用技術(shù)大學(xué),2016.
[28] 張榮飛,王相友. 電噴霧納米涂膜工藝優(yōu)化及其對(duì)雙孢蘑菇保鮮效果[J]. 農(nóng)業(yè)工程學(xué)報(bào),2017,33(23):291-299.Zhang Rongfei, Wang Xiangyou. Process optimization of Nano-SiO2/potato starch coatings and its improving effect for storage ofby electrospraying[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(23): 291-299. (in Chinese with English abstract)
[29] 王娟,王相友,李霞. 低溫氣調(diào)貯藏下氧氣含量對(duì)雙孢蘑菇品質(zhì)的影響[J]. 農(nóng)業(yè)機(jī)械學(xué)報(bào),2010,41(4):110-113. Wang Juan, Wang Xiangyou, Li Xia. Effects of oxygen concentration on storage quality ofunder low temperature and controlled atmosphere storage[J]. Transactions of the Chinese Society for Agricultural Machinery, 2010, 41(4): 110-113. (in Chinese with English abstract)
[30] 趙春霞,李大虎,程玉嬌,等. 高氧氣調(diào)包裝對(duì)雙孢蘑菇品質(zhì)的影響[J]. 包裝工程,2014,35(15):5-10. Zhao Chunxia, Li Dahu, Cheng Yujiao, et al. Effects of modified atmosphere packaging with O2on the qualities of. Packaging Engineering, 2014, 35(15): 5-10. (in Chinese with English abstract)
[31] 國(guó)家食品藥品監(jiān)督管理總局. 食品衛(wèi)生微生物學(xué)檢驗(yàn)菌落總數(shù)測(cè)定:GB/T 4789.2-2016 [S]. 北京:標(biāo)準(zhǔn)出版社,2016-12.
[32] 藍(lán)亮美,馬麗,郭占京,等. 三種桂產(chǎn)桉葉油對(duì)常見(jiàn)致腐菌的抑制作用研究[J]. 食品工業(yè)科技,2014,35(22):155-158. Lan Liangmei,Ma Li,Guo Zhanjing,et al. Study on major components and antimicrobial activities of volatile oil extracted from three kinds of eucalyptus leaves[J]. Science and Technology of Food Industry,2014,35(22): 155-158. (in Chinese with English abstract)
[33] 陶菲. 真空預(yù)冷處理延長(zhǎng)白蘑菇貯藏期的研究[D]. 無(wú)錫: 江南大學(xué),2006:1-70.
[34] Gormley R. Chill storage of mushrooms[J]. Journal of the Science of Food & Agriculture, 1975, 26(4): 401-411.
[35] 林河通,席玙芳,陳紹軍,等. 龍眼采后生理和病理及貯運(yùn)技術(shù)研究進(jìn)展[J]. 農(nóng)業(yè)工程學(xué)報(bào),2002,18(1):185-190. Lin Hetong, Xi Yufang, Chen Shaojun, et al. Research advances of postharvest physiology, postharvest pathology andstorage and transport technologies for longan fruits[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2002, 18(1): 185-190. (in Chinese with English abstract)
[36] Qin Y, Liu D, Wu Y, et al. Effect of PLA/PCL/ cinnamaldehyde antimicrobial packaging on physicochemical and microbial quality of button mushroom () [J]. Postharvest Biology &Technology, 2015, 99(3): 73-79.
Inhibitory and fresh-keeping effects study of plant essential oil sodium alginate composite film on
Wang Juan, Cheng Meng, Kong Ruiqi, Lu Wenqian, Zhang Rongfei, Wang Xiangyou, Guo Yanyin
(255049)
Button mushroom () is one of the most popular mushrooms, traditionally cultivated in the world. Mushrooms are a good source of mannitol, vitamins, saccharides, organic bases and many mineral elements. However, button mushrooms only have a short shelf life, and they will lose their commercial value within a few days, due to browning, water loss, senescence and microbial attack. The short shelf-life of mushroom is an impediment to the distribution and marketing of the fresh product. Food spoilage and food poisoning caused by microbial infection during the harvesting, processing, transportation and storage of foods present an enormous threat to consumers and the development of food industry. Plant essential oil (EO) is an important volatile secondary metabolite in plants, which is well known for its high volatility, low residual generation, and very rare resistance problems. The purpose of this paper is to study the inhibitory effect of plant EOs on the main spoilage bacteria of mushroom during storage. Nine colonies were obtained by isolating and purifying the main spoilage microorganisms of mushroom. According to morphological identification, these colonies are 3 kinds of molds and 2 kinds of bacteria respectively. It was confirmed by pathogenicity test that the main pathogen of mushroom during storage was strain No. 3. The 18S rDNA sequence phylogenetic tree analysis of the pathogen showed that the pathogen No. 3 was closely related to. Four kinds of EO, which areEO (TEO),EO (FEO),EO (EEO) andEO (AEO), were used to test the antibacterial activity against the Strain No. 3. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of preferred EO were determined by agar disk diffusion test. The results showed that EEO has the best inhibitory effect on., followed by FEO, while TEO and AEO have no obvious inhibitory effect. The MIC and MBC of EEO were 0.3125 and 0.625L/mL, respectively. The MIC and MBC of FEO were 0.625 and 1.25L/mL, respectively. Water vapor transmission rate, oxygen permeability, tensile strength and elongation at break of sodium alginate/EEO composite ?lm and sodium alginate single film were measured. The results show that the addition of EEO can significantly improve the gas barrier properties and mechanical properties of the membrane. The effects of four different packaging treatments on the physicochemical properties and microbial quality of mushrooms stored at 4°C for 12 d were investigated. The fresh mushrooms were packaged with the sodium alginate/EEO composite ?lm, sodium alginate single ?lm and PE film, and unpackaged mushrooms were used as control. The microbial levels and physicochemical properties such as weightloss, ?rmness, color, cell membrane permeability, and microbiological quality were measured. Although the highest weight loss (3.51%) was observed in the sodium alginate/EEO treatment at the end of storage, it was still lower than 5%. Mushrooms packaged in the sodium alginate/EEO composite ?lm was signi?cantly (<0.05) ?rmer than those packaged in the sodium alginate single film and PE ?lm. The cell membrane permeability the odium alginate/EEO ?lm was lower than those of the other treatments, and the browning index was similar. The sodium alginate/EEO ?lm was more effective in reducing microbial counts of mushrooms than the other two ?lms. The overall acceptability of mushrooms packaged in the sodium alginate/EEO ?lm remained good and within the limit of marketability after 12 d storage. The results suggested that the sodium alginate/EEO film could effectively reduce the senescence and pathogenic decay of mushrooms. The results of this study can provide a theoretical basis for the selection of antiseptic and natural bactericidal preservatives for mushroom during storage.
pathogen; essential oils; film;; antibacterial properties; preservation
2018-09-19
2019-02-28
國(guó)家自然科學(xué)基金資助項(xiàng)目(31301819);山東省農(nóng)業(yè)重大應(yīng)用技術(shù)創(chuàng)新課題(魯財(cái)農(nóng)字[2014]38號(hào));淄博市校城融合計(jì)劃項(xiàng)目(2018ZBXC142)
王 娟,副教授,博士,主要從事農(nóng)產(chǎn)品加工及貯藏方面研究。Email:wangjuan7912@163.com
10.11975/j.issn.1002-6819.2019.05.038
S646
A
1002-6819(2019)-05-0311-08
王 娟,程 萌,孔瑞琪,逯文倩,張榮飛,王相友,郭衍銀. 植物精油海藻酸鈉復(fù)合膜對(duì)雙孢蘑菇的抑菌保鮮效果研究[J]. 農(nóng)業(yè)工程學(xué)報(bào),2019,35(5):311-318.doi:10.11975/j.issn.1002-6819.2019.05.038 http://www.tcsae.org
Wang Juan, Cheng Meng, Kong Ruiqi, Lu Wenqian, Zhang Rongfei, Wang Xiangyou, Guo Yanyin. Inhibitory and fresh-keeping effects study of plant essential oil sodium alginate composite film on[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(5): 311-318. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2019.05.038 http://www.tcsae.org