常江,宛新國(guó),孫智慧,李曉燕
水產(chǎn)品超聲輔助浸漬冷凍技術(shù)研究進(jìn)展
常江a,宛新國(guó)a,孫智慧b,李曉燕c*
(哈爾濱商業(yè)大學(xué) a.輕工學(xué)院 b.高教發(fā)展研究中心 c.能源與建筑工程學(xué)院,哈爾濱 150028)
為延長(zhǎng)水產(chǎn)品銷售周期,最大程度保持其營(yíng)養(yǎng)品質(zhì),促進(jìn)水產(chǎn)品冷凍保藏及加工技術(shù)的發(fā)展和產(chǎn)業(yè)化。歸納總結(jié)超聲輔助浸漬冷凍的作用機(jī)理,并探究其對(duì)冰晶形成和生長(zhǎng)以及水產(chǎn)品保鮮加工的影響。超聲輔助浸漬冷凍能有效提高冷凍效率,減小冰晶晶核規(guī)格,縮短冷凍時(shí)間,減緩水產(chǎn)品蛋白質(zhì)變性與脂質(zhì)氧化速率,改善水產(chǎn)品質(zhì)構(gòu)、保持其營(yíng)養(yǎng)價(jià)值,是水產(chǎn)品冷凍處理的有效途徑。超聲輔助浸漬冷凍技術(shù)能在一定程度上解決水產(chǎn)品冷凍過(guò)程中存在的問(wèn)題,為水產(chǎn)品冷凍技術(shù)產(chǎn)業(yè)化提供支持。超聲輔助浸漬冷凍技術(shù)在作用機(jī)制、適用范圍和特定環(huán)境下的作用衰減等方面存在著一定缺陷,還需深入闡述其作用機(jī)理,為冷凍智能裝備開(kāi)發(fā)提供保障。
水產(chǎn)品;浸漬冷凍;超聲輔助;研究進(jìn)展
隨著人們健康意識(shí)的增強(qiáng),高營(yíng)養(yǎng)低脂肪的水產(chǎn)品逐漸受到消費(fèi)者青睞,但由于水產(chǎn)品中的內(nèi)源酶和微生物,為其貯藏保鮮帶來(lái)不良影響,限制了水產(chǎn)及其制品的流通銷售[1]。我國(guó)水產(chǎn)資源豐富,養(yǎng)殖和出口量居世界前列。相關(guān)資料顯示,我國(guó)每年由于儲(chǔ)運(yùn)導(dǎo)致死亡和腐敗的水產(chǎn)品占其總量的1/10,其中的36%被制成粉或動(dòng)物飼料等,浪費(fèi)極其嚴(yán)重,因此迫切需要利用高效的水產(chǎn)品保鮮技術(shù)保持水產(chǎn)品的鮮度品質(zhì),以減少其流通期間的品質(zhì)劣變,提高利用率。目前,水產(chǎn)品的保鮮主要包括化學(xué)保藏、生物保藏和物理保藏等[2-4]?;瘜W(xué)保藏操作方便,但存在化合物殘留,易造成安全問(wèn)題;生物保藏安全性高,但存在生物活性提取物結(jié)構(gòu)和成分復(fù)雜、分離純化工藝較復(fù)雜、成本高昂等問(wèn)題;物理保藏安全性高,能有效抑制酶活性,減緩新陳代謝作用,從而有效保持水產(chǎn)品質(zhì),延長(zhǎng)流通周期,近年來(lái)成為了國(guó)內(nèi)外研究人員聚焦的熱點(diǎn)[5]。
傳統(tǒng)的物理保藏技術(shù)以冰溫保鮮和凍藏為主,盡管可以保持水產(chǎn)品的品質(zhì),但較長(zhǎng)的冷凍時(shí)間使得晶核形成周期長(zhǎng)、晶核大、營(yíng)養(yǎng)細(xì)胞內(nèi)部組織破壞程度大、營(yíng)養(yǎng)流失嚴(yán)重[6-7],因此,改進(jìn)冷凍技術(shù)和方法,提高冷凍速率對(duì)提高冷凍水產(chǎn)品品質(zhì)至關(guān)重要。浸漬冷凍技術(shù)(Immersion Chilling and Freezing,ICF)是將食品置于低溫冷凍液中實(shí)現(xiàn)速凍的加工技術(shù),與傳統(tǒng)冷凍技術(shù)相比,其具有高效低能的特點(diǎn),并能有效提升水產(chǎn)品品質(zhì),在國(guó)內(nèi)外廣受好評(píng)[8-9]。食品的浸漬式冷凍過(guò)程最大的特征就是傳熱傳質(zhì)同時(shí)發(fā)生,它不僅導(dǎo)致熱量迅速傳遞,同時(shí)也伴隨著食品內(nèi)部水分與溶液溶質(zhì)的相互遷移,其過(guò)程如圖1所示。食品在凍結(jié)過(guò)程中,其種類、形狀、大小、成分組成等因素均會(huì)影響凍結(jié)速率。浸漬式冷凍技術(shù)能有效地提高食品的冷凍速率是因?yàn)槔鋬鲆旱膫鳠嵯禂?shù)高于空氣幾倍有余。在食品與冷凍液傳熱過(guò)程中,沿?zé)崃鞣较虻闹饕獰嶙枋沁吔鐚樱浜穸仍酱?,傳熱效果越差。因此,在浸漬冷凍過(guò)程中,可引入輔助技術(shù),如高壓、超聲、電磁場(chǎng)和微波[10-12]等,從而提升冷凍速率,減小對(duì)水產(chǎn)品營(yíng)養(yǎng)成分的破壞。其中發(fā)展最為迅速的是超聲波輔助冷凍。超聲的聲學(xué)效應(yīng)能促進(jìn)冰晶成核,減少組織破壞引起的營(yíng)養(yǎng)損失,更好地保持冷凍食品的組織結(jié)構(gòu),提升保存質(zhì)量[13-14]。對(duì)超聲輔助浸漬式速凍技術(shù)的保鮮機(jī)理和工作過(guò)程進(jìn)行研究并不斷優(yōu)化,有利于更好地保持水產(chǎn)品的鮮度品質(zhì),延緩水產(chǎn)品流通期間的品質(zhì)劣變,提升水產(chǎn)原料的利用率,也可為水產(chǎn)品物理保鮮技術(shù)的發(fā)展提供參考。本文針對(duì)水產(chǎn)品的超聲輔助浸漬冷凍技術(shù)的研究現(xiàn)狀,歸納總結(jié)了超聲輔助浸漬冷凍技術(shù)的機(jī)理、實(shí)驗(yàn)裝置及對(duì)水產(chǎn)品品質(zhì)影響等方面的研究進(jìn)展,旨在為水產(chǎn)品超聲輔助浸漬冷凍加工產(chǎn)業(yè)化和冷鏈物流技術(shù)發(fā)展提供理論參考。
超聲輔助浸漬冷凍主要利用超聲的空化和微射流效應(yīng)提升水產(chǎn)品的冷凍速率、減小晶核規(guī)格和組織損傷,提高水產(chǎn)品保藏和解凍品質(zhì)。超聲是一種頻率在20 kHz以上、超出人耳聽(tīng)覺(jué)極限的機(jī)械波,在傳播過(guò)程中可以引起振動(dòng)[15]。目前,常見(jiàn)的超聲波分為高頻低能和低頻高能2類,高頻低能超聲波主要應(yīng)用于食品的無(wú)損檢測(cè)和品質(zhì)控制,頻率超過(guò)100 kHz,但能量較低;低頻高能超聲頻率介于20~100 kHz,能量較高,主要應(yīng)用于改善水產(chǎn)品性質(zhì)等方面[16-18]??栈?yīng)的產(chǎn)生源于超聲在介質(zhì)中傳播時(shí)可以產(chǎn)生一種高頻的機(jī)械壓力,這種機(jī)械壓力效應(yīng)能夠使介質(zhì)中質(zhì)點(diǎn)因振動(dòng)而移位,進(jìn)而在介質(zhì)中形成高壓區(qū)和負(fù)壓區(qū),超聲作用會(huì)在直徑為1 μm以下的氣泡之間形成負(fù)壓空化氣泡,當(dāng)超聲功率未引起氣泡破裂時(shí),空化氣泡形成微射流減少了水產(chǎn)品與介質(zhì)的邊界層阻力,提高了介質(zhì)的傳熱效率,進(jìn)而提高了冷凍效率;當(dāng)超聲功率高于氣泡空化閾值時(shí),劇烈的震動(dòng)引起空化氣泡的破裂,提高了過(guò)冷度、加快了二次成核的速度、減小了冰晶的尺寸[19-20]。冷凍時(shí)間的縮短、冰晶尺寸的減小能夠降低冷凍對(duì)細(xì)胞組織造成的損傷,進(jìn)而提升水產(chǎn)品貯藏品質(zhì)。超聲輔助浸漬冷凍過(guò)程中水產(chǎn)品與冷凍液的傳熱傳質(zhì)過(guò)程和超聲輔助冷凍技術(shù)作用機(jī)理分別如圖1和圖2所示。
圖1 超聲輔助浸漬冷凍過(guò)程中食品與冷凍液的傳熱與傳質(zhì)
1.2.1 對(duì)冰晶成核的影響
初次成核和二次成核是超聲輔助成核的2個(gè)主要階段。當(dāng)溫度達(dá)到成核溫度時(shí),開(kāi)始初次成核,釋放出大量潛熱,超聲的空化作用有助于過(guò)冷度的降低,從而驅(qū)動(dòng)成核過(guò)程[21-22];尺寸達(dá)到臨界閾值的微氣泡本身可充當(dāng)冰核;穩(wěn)定的空化氣泡運(yùn)動(dòng)會(huì)導(dǎo)致微流和渦流,從而增強(qiáng)傳熱和傳質(zhì),并有助于成核。在基于預(yù)先存在的冰晶的二次成核過(guò)程中,由于空化氣泡的塌陷和剪切力,超聲輻照可將這種預(yù)先存在的冰的樹(shù)突分解為許多源自微流較小的碎片,導(dǎo)致產(chǎn)生更多的成核位點(diǎn)。
圖2 超聲輔助冷凍技術(shù)作用機(jī)理[21]
在無(wú)晶體溶液中形成新晶體的過(guò)程被稱為初次成核。初次成核是冷凍效果和被冷凍食品質(zhì)量的決定性因素[23]。成核過(guò)程自發(fā)隨機(jī),功率超聲的加入能提高初次成核的確定性或可重復(fù)性。功率超聲會(huì)引發(fā)空化氣泡的塌陷,會(huì)顯著提升細(xì)胞的局部壓力和過(guò)冷度,導(dǎo)致晶核形成,同時(shí)還會(huì)控制水到冰的相變過(guò)程,提高過(guò)冷水中冰晶形成的可能性,而冰晶的重現(xiàn)程度可由超聲強(qiáng)度控制[24-26]。冰晶的成核速率和數(shù)量與空化作用有關(guān),超聲輔助能夠誘導(dǎo)細(xì)胞內(nèi)外成核速率,并減小冰晶的尺寸分布[27-28]。吳宇桐等[29]認(rèn)為超聲作用下空化氣泡破碎會(huì)使局部壓力瞬間達(dá)到5×106Pa以上,同時(shí)釋放大量的熱,引發(fā)溶液形成晶核。因此,超聲輔助浸漬冷凍技術(shù)有利于晶核的快速形成,并可將冰枝晶分解成較小碎片,減少對(duì)水產(chǎn)品結(jié)構(gòu)損傷,但誘導(dǎo)冰晶成核的機(jī)制還未明晰,成核過(guò)程可能存在多種機(jī)制的相互作用,有待進(jìn)一步深入研究。
二次成核指在含有已有晶體的溶液中產(chǎn)生新的晶體,其可通過(guò)晶體作為模板形成新的晶體核,也可通過(guò)晶體破碎產(chǎn)生更多的成核位點(diǎn),微射流作用是二次成核的主要誘因。超聲的空化氣泡產(chǎn)生的微射流可破壞枝晶,改變冰晶的整體生長(zhǎng)模式,產(chǎn)生新的晶核,引起二次成核[30-31]。Kiani等[32]和Zhang等[33]研究發(fā)現(xiàn)超聲空化作用會(huì)引起氣泡的擴(kuò)散,導(dǎo)致氣泡破碎而引起微射流,使溶液二次成核。分子偏析是超聲誘導(dǎo)成核的另一種形式,冰晶成核的驅(qū)動(dòng)力源自空化氣泡周邊的壓力梯度,其間的時(shí)間差可由氣泡塌陷引起的質(zhì)量擴(kuò)散時(shí)間決定。因此,2種理論從不同的角度證實(shí)了超聲輔助浸漬冷凍有利于冰晶的二次成核,主要由于超聲對(duì)枝晶的分裂作用,被破碎的冰晶會(huì)在冷夜中促進(jìn)形成新的晶核,但超聲成核的機(jī)理仍未有明確闡述,還有待于深入研究。
1.2.2 超聲輔助浸漬冷凍對(duì)晶體生長(zhǎng)規(guī)律的影響
冰晶規(guī)格和分布規(guī)律是評(píng)價(jià)冷凍食品質(zhì)量的重要參數(shù),營(yíng)養(yǎng)細(xì)胞中冰晶越細(xì)、分布越均勻,對(duì)細(xì)胞和組織的破壞越小,品質(zhì)和營(yíng)養(yǎng)保持得越好[34-35]。超聲輔助冷凍具有誘導(dǎo)成核和控制冰晶生長(zhǎng)的能力,兩者取決于過(guò)冷程度。當(dāng)在系統(tǒng)溫度低于凝固點(diǎn)溫度時(shí)施加功率超聲,會(huì)形成許多原子核,且其只會(huì)長(zhǎng)到有限大小。Sun等[36]利用不同頻率超聲輔助浸漬冷凍技術(shù)對(duì)鯉魚(yú)進(jìn)行處理,表明175 W的超聲功率下,鯉魚(yú)組織的冰晶規(guī)格最小,組織細(xì)胞破壞程度最低。向迎春等[37]對(duì)比了–20 ℃下的冰箱冷凍、直接浸漬冷凍和超聲輔助浸漬冷凍后的明蝦,結(jié)果表明,超聲輔助能夠優(yōu)化冰晶生長(zhǎng)和調(diào)控,減小了冷凍引起的組織損傷。綜上所述,超聲誘導(dǎo)成核會(huì)生成較小的冰晶,降低冰晶的平均尺寸并增加其平均圓形度,優(yōu)化冰晶的形態(tài)和分布。但是關(guān)于超聲輔助浸漬冷凍對(duì)冰晶生長(zhǎng)或晶體形態(tài)影響的研究成果相對(duì)較少,冷凍對(duì)象的組織結(jié)構(gòu)不同,冰晶的形態(tài)和分布規(guī)律也不盡相同。因此,在后續(xù)的研究中,需要從多個(gè)角度進(jìn)一步明晰超聲輔助的作用機(jī)制,為實(shí)現(xiàn)工業(yè)生產(chǎn)提供理論依據(jù)。
1.2.3 超聲輔助浸漬對(duì)冷凍速率的影響
冷凍速率是衡量水產(chǎn)品冷凍效果的重要參數(shù)。相比于傳統(tǒng)冷凍方式,快速冷凍可形成更小冰晶、緩解細(xì)胞脫水速率、保護(hù)組織結(jié)構(gòu),從而更好地保持水產(chǎn)品品質(zhì)。葉劍等[38]、向迎春等[37]和劉宏影等[39]利用超聲輔助浸漬冷凍技術(shù)分別對(duì)鮸魚(yú)、明蝦和海鱸魚(yú)片進(jìn)行了處理。結(jié)果發(fā)現(xiàn)超聲輔助浸漬冷凍比直接浸漬冷凍的速度提升了10倍,比冰箱冷凍提升了90.15%。超聲輔助浸漬冷凍能夠提升冷凍速度的主要原因在于晶核的形成速率和尺寸分布。通過(guò)1.2.1節(jié)和1.2.2節(jié)可知,超聲的空化作用能夠引起晶枝的破損,生成尺寸更小、分布更均勻的冰核,可以有效地提高冰晶的形成速率,進(jìn)而提高冷凍速率。因此,超聲輔助浸漬冷凍有利于提高冷凍速率,減少結(jié)晶對(duì)組織細(xì)胞的傷害,獲得更好的組織結(jié)構(gòu),保持水產(chǎn)品的含水率和營(yíng)養(yǎng)。
近年來(lái),國(guó)內(nèi)外對(duì)超聲輔助浸漬冷凍裝置的研究日益升溫,常用的超聲輔助浸漬冷凍設(shè)備根據(jù)浸漬方式的不同可分為全浸沒(méi)式、半浸沒(méi)式和非浸沒(méi)式三大類。通常超聲輔助浸漬冷凍裝置由超聲系統(tǒng)、冷卻劑循環(huán)系統(tǒng)、制冷循環(huán)系統(tǒng)、溫度檢測(cè)系統(tǒng)和數(shù)據(jù)記錄系統(tǒng)等幾部分組成。超聲系統(tǒng)通常由多個(gè)傳感器組構(gòu)成,這些傳感器均勻地連接在冷凍槽底部,另一端則連接到發(fā)電機(jī)上。冷卻液循環(huán)系統(tǒng)通過(guò)位于溫度控制端的盤管泵送,并與壓縮機(jī)相連的熱交換器進(jìn)行冷卻和溫度控制。溫度檢測(cè)系統(tǒng)通常與數(shù)據(jù)記錄系統(tǒng)耦合,由熱電偶探針和連接到計(jì)算機(jī)的數(shù)據(jù)記錄器組成。常見(jiàn)的超聲輔助冷凍裝置結(jié)構(gòu)及特點(diǎn)如表1所示。就超聲輔助浸漬冷凍裝置而言,全浸式輔助冷凍裝置目前應(yīng)用最為廣泛,半浸沒(méi)式和非浸沒(méi)式超聲輔助冷凍裝置鮮有使用。Sun等[40]在180 W超聲輔助條件下對(duì)鯉魚(yú)進(jìn)行了全浸漬冷凍,研究結(jié)果表明,與傳統(tǒng)冷凍和空氣冷凍相比,超高壓輔助全浸漬冷凍的鯉魚(yú)組織中的冰晶更小,蛋白質(zhì)穩(wěn)定性更高,硫代巴比妥酸活性物和揮發(fā)性鹽基氮總量較低,提高了鯉魚(yú)在冷凍過(guò)程中的質(zhì)量。
超聲輔助浸漬冷凍能縮短冷凍時(shí)間,形成小而均勻的冰晶,提升水產(chǎn)品的水分、顏色與質(zhì)構(gòu)等,削弱冰晶對(duì)蛋白質(zhì)等營(yíng)養(yǎng)物質(zhì)組織結(jié)構(gòu)的破壞程度,保持其品質(zhì)。
表1 常見(jiàn)超聲輔助冷凍裝置結(jié)構(gòu)及特點(diǎn)[41]
Tab.1 Structures and characteristics of common ultrasound assisted freezing devices[41]
水是決定水產(chǎn)品穩(wěn)定性的關(guān)鍵成分,因?yàn)槠浞植己拖嗷プ饔秒S水產(chǎn)品成分的不同而變化。水與其他組分的相互作用和鍵合也決定了不同溫度下的水活性。水產(chǎn)品的含水量較高,以游離水、固定化水和結(jié)合水的方式存在。在冷凍儲(chǔ)存過(guò)程中,由于水的滲透去除、冰晶對(duì)肌纖維的破壞、肌纖維蛋白的聚集等變化會(huì)引起水產(chǎn)品的質(zhì)構(gòu)、顏色、風(fēng)味等發(fā)生變化,從而導(dǎo)致品質(zhì)降低。超聲輔助浸漬冷凍技術(shù)限制了水的流動(dòng),提高了冷凍速率,縮短了冷凍周期,減少了結(jié)合水的析出。空化作用減小了冰晶的尺寸和分布,改善了水產(chǎn)品中水分子的分布和遷移[42-43],降低了冰晶對(duì)組織纖維的破壞,提升了水產(chǎn)品的品質(zhì)。葉劍等[38]發(fā)現(xiàn)空氣冷凍、浸漬冷凍后,鮸魚(yú)的持水力有所降低,而超聲輔助浸漬冷凍后鮸經(jīng)過(guò)12周的儲(chǔ)藏后魚(yú)的持水力仍然維持得較好。說(shuō)明,超聲輔助能夠在一定程度上彌補(bǔ)浸漬冷凍技術(shù)的短板,提升水產(chǎn)品品質(zhì)。
質(zhì)構(gòu)是表征水產(chǎn)品口感特征的重要指標(biāo)之一,包括其硬度、咀嚼性、彈性等,真實(shí)反映了水產(chǎn)品的品質(zhì)。水產(chǎn)品在冷凍過(guò)程中的冰晶大小、冷凍速率等工藝指標(biāo)與水產(chǎn)品的質(zhì)構(gòu)有著緊密的聯(lián)系。在冷凍過(guò)程中,冰晶的形成會(huì)破壞水產(chǎn)品的肌原纖維及結(jié)締組織,從而引起質(zhì)構(gòu)的破壞。超聲輔助浸漬冷凍技術(shù)能夠提高冷凍速率、誘導(dǎo)晶核生長(zhǎng)分布而形成更小且分布均勻的冰晶,減小由于冰晶的形成造成的水產(chǎn)品肌肉組織破壞程度,有利于水產(chǎn)品質(zhì)構(gòu)特性的保持。Ying等[44]基于Box-Behnken優(yōu)化了超聲輔助浸漬冷凍工藝條件,在超聲功率180 W下,中國(guó)對(duì)蝦的纖維組織明顯優(yōu)于非超聲冷凍的顯微組織切片。Ma等[45]研究了大黃魚(yú)超聲輔助冷凍的品質(zhì),結(jié)果表明處理后的樣品質(zhì)量參數(shù)和顯微組織更接近新鮮樣品,具有更明顯的紋理特征和更強(qiáng)的持水能力。緩解了由于冷凍引起的解凍損失和烹飪損失,降低了大黃魚(yú)的值和硫代巴比妥酸值等,有效保持了大黃魚(yú)品質(zhì)。
色差指2個(gè)試樣在顏色知覺(jué)上的差異,它包括明度差、彩度差和色相差三方面。水產(chǎn)品在貯藏過(guò)程中,隨著腐敗的進(jìn)行,體表的明度和色度會(huì)隨之改變。因此,水產(chǎn)品的色差是消費(fèi)者評(píng)價(jià)水產(chǎn)品新鮮度最直觀的指標(biāo),也是刺激消費(fèi)者購(gòu)買欲望的直接因素。Shi等[46]研究發(fā)現(xiàn)利用超聲輔助冷凍技術(shù)處理的鯰魚(yú)由于表面游離水的增加使魚(yú)肉白度呈波動(dòng)性增加,由于酶和氧氣接觸發(fā)生的脂質(zhì)氧化使魚(yú)肉從白色到微黃色變化的程度變得比較緩慢,有效地抑制了魚(yú)肉顏色的變化。明度和亮度的變化與魚(yú)肉含水量緊密聯(lián)系,在儲(chǔ)藏過(guò)程中,魚(yú)肉會(huì)由于水分的損失影響其色澤,使魚(yú)肉黯淡無(wú)光。因此,超聲輔助浸漬冷凍技術(shù)在保持水產(chǎn)品水分方面的優(yōu)勢(shì)會(huì)減小其在流通和儲(chǔ)藏方面的色差損失,但是否與冰晶分布和大小有關(guān),還有待進(jìn)一步研究。
水產(chǎn)品中的蛋白質(zhì)含量豐富,還含有多種礦物質(zhì)、氨基酸及維生素等營(yíng)養(yǎng)物質(zhì),備受消費(fèi)者的關(guān)注。由于水產(chǎn)品肉質(zhì)含水量較高,容易引起蛋白質(zhì)的變性,因此,在儲(chǔ)藏和銷售過(guò)程中受到了諸多限制。冷凍是當(dāng)下最常見(jiàn)的儲(chǔ)存方式,探究超聲輔助浸漬冷凍對(duì)水產(chǎn)品蛋白質(zhì)的影響,能夠檢驗(yàn)水產(chǎn)品在凍藏過(guò)程中的品質(zhì)變化。孫協(xié)軍等[47]研究了海鱸魚(yú)片在超聲輔助浸漬冷凍下的魚(yú)肉蛋白質(zhì)特性,結(jié)果表明,此方法能保持纖維蛋白的三級(jí)結(jié)構(gòu)和品質(zhì)。Yang等[48]利用超聲輔助浸漬冷凍技術(shù)對(duì)美洲石首魚(yú)的品質(zhì)和蛋白質(zhì)氧化程度進(jìn)行了分析。結(jié)果表明,利用超聲輔助冷凍技術(shù)處理的石首魚(yú)肌原纖維的氧化變性蛋白質(zhì)在冷凍儲(chǔ)存90 d后減少。此外,超聲頻率為200 W組的冷凍樣本與其他組相比具有更高的蛋白質(zhì)穩(wěn)定性。因此,超聲輔助浸漬冷凍能降低蛋白質(zhì)的變性和結(jié)構(gòu)破壞的程度,降低氧化程度,加速角狀體的冷凍過(guò)程,保持其肌肉質(zhì)量,提高蛋白的穩(wěn)定性和完整性,使水產(chǎn)品纖維更加緊實(shí),提升其口感并保持營(yíng)養(yǎng),減少自由水和結(jié)合水的流動(dòng)性,保持組織細(xì)胞的含水量,提升加工品質(zhì)。超聲輔助能改善冷凍后水產(chǎn)品的品質(zhì)和營(yíng)養(yǎng)價(jià)值,其根本在于超聲輔助對(duì)冰晶的成核作用。因此,對(duì)其作用機(jī)理的進(jìn)一步探究,能實(shí)現(xiàn)超聲輔助浸漬冷凍技術(shù)的工業(yè)化。
超聲輔助浸漬冷凍技術(shù)能加快晶核的形成、控制冰晶規(guī)格和分布、提高冷凍速度、減小組織損傷、最大程度保持水產(chǎn)品品質(zhì)和營(yíng)養(yǎng)價(jià)值。關(guān)于該技術(shù)在水產(chǎn)品中的應(yīng)用和作用機(jī)制的研究也成為了研究熱點(diǎn),擁有廣闊的應(yīng)用前景,能為水產(chǎn)品加工產(chǎn)業(yè)發(fā)展和智能裝備開(kāi)發(fā)提供有效途徑。已有研究成果表明超聲輔助浸漬冷凍具有一定的優(yōu)越性,但也存在著一定的技術(shù)缺陷:對(duì)脂肪含量比較高的海產(chǎn)品而言,超聲的空化作用會(huì)引起局部壓力和溫度的增大,在水中生成大量自由基,加速脂類物質(zhì)的氧化變質(zhì);如何避免超聲作為能量波,在傳遞過(guò)程中可能會(huì)出現(xiàn)的散射或衰減引起的作用減弱;當(dāng)水產(chǎn)品中含有特殊結(jié)構(gòu)時(shí),超聲作用可能會(huì)產(chǎn)生異味,影響水產(chǎn)品品質(zhì)。綜上所述,超聲輔助浸漬冷凍技術(shù)的適用范圍和技術(shù)缺陷尚未得到解決,作用機(jī)制也尚未明晰,需要在今后的研究中深入探究并解決。
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Research Progress in Ultrasound Assisted Immersion Freezing Technology for Aquatic Products
CHANG Jianga, WAN Xinguoa, SUN Zhihuib, LI Xiaoyanc*
(a. Light Industry, b. Higher Education Development Research Center, c. School of Energy and Building Engineering, Harbin University of Commerce, Harbin 150028, China)
The work aims to extend the sales cycle of aquatic products, maximize their nutritional quality, and promote the development and industrialization of frozen storage and processing technology for aquatic products. The mechanism of ultrasound assisted immersion freezing and its impact on the formation and growth of ice crystals as well as the preservation and processing of aquatic products were summarized and reviewed. The ultrasound assisted immersion freezing could effectively improve the freezing efficiency, reduce the size of ice crystals, shorten the freezing time, slow down the protein denaturation and lipid oxidation rate of aquatic products, improve the quality structure of aquatic products and maintain their nutritional value, which was an effective way to freeze aquatic products. Ultrasound assisted immersion freezing technology can solve the problems existing in the freezing process of aquatic products to some extent, providing support for the industrialization of aquatic product freezing technology. The ultrasonic assisted immersion freezing technology has certain shortcomings in terms of its mechanism of action, applicability, and attenuation in specific environment. It is necessary to further elaborate on its mechanism of action to provide support for the development of intelligent freezing equipment.
aquatic products; immersion freezing; ultrasound assistance; research progress
TB661
A
1001-3563(2024)01-0183-08
10.19554/j.cnki.1001-3563.2024.01.021
2023-09-19
“十三五”國(guó)家科技支撐計(jì)劃項(xiàng)目(2016YFD0400301)