乙醇耦合其他预处理提高扇贝柱热泵干燥速率及品质

Enhancing the heat pump drying rate and quality attributes of scallop adductors using ethanol coupled with other pre-treatments

干燥后期速率低、能耗高是限制热泵干燥(heat pump drying,HPD)在水产品干燥中应用的瓶颈。非热力预处理技术在易腐食品干燥中具有提高干燥速率和改善干制品品质的巨大潜力。基于此,该研究以乙醇(E)单独和联合真空(VC+E)、超声波(US+E)、超声波辅助真空(USVC+E)预处理作为处理组,以未经预处理的扇贝柱为对照(CK),探究其对扇贝柱干燥动力学及干制品品质特性的影响。利用低场核磁共振(low-field nuclear magnetic resonance,LF-NMR)技术,对扇贝柱热泵干燥过程中水分状态及分布进行了研究。结果表明:扇贝柱热泵干燥处于降速干燥阶段,干燥过程受水分内部扩散的控制。Weibull模型能较好地描述扇贝柱热泵干燥过程。与CK相比,乙醇单独处理和US和/或真空联合预处理都能提高水分有效扩散系数(Deff),进而提高干燥速率。LF-NMR结果表明,扇贝柱中主要水分为不易流动水;随着干燥进行,各组分的横向弛豫时间向左偏移;不易流动水所占比例降低,而紧密结合水、疏松结合水和自由水所占比例增加。与CK相比,预处理有利于扇贝柱不易流动水向自由水转化,进而提高干燥速率。与CK相比,乙醇单独处理和US和/或真空联合预处理可降低扇贝柱黄度、总色差、收缩率、硬度、弹性和咀嚼性,但是增加了扇贝柱的亮度、红度和复水比。预处理组中,US+E和USVC+E色泽参数(总色差:US+E,(7.40±0.22);USVC+E,(6.99±0.16))最佳,收缩率(US+E,35.97%±1.29%;USVC+E,34.43%±1.24%)和硬度(US+E,(25.20±1.08)N;USVC+E,(26.68±0.61)N)最低;而US+E弹性(0.55±0.01)和咀嚼性(7.27±0.30)N最低,但复水比(1.753±0.022)最高。相比于CK,US+E可显著降低(P<0.05)总色差58.24%,收缩率32.75%、硬度23.17%、弹性15.38%、咀嚼性38.91%,但是复水180 min后,能显著提高(P<0.05)复水比9.975%。综合考虑,US+E作为一种非热力、绿色预处理技术,可用于强化扇贝柱热泵干燥效率,改善干制品品质。

Low drying rate and high energy consumption in the later stage of heat pump drying(HPD)have restricted its application in aquatic products drying.Non-thermal pretreatment has exhibited great potential for the drying of perishable food with enhanced drying rate and quality performances.This study aims to investigate the effects of ethanol(E)alone and in combination with other pretreatments,viz.,vacuum(VC+E),ultrasonic(US+E),and ultrasonic-assisted vacuum(USVC+E)on the drying kinetics and quality of dried scallop adductors(SA).Moreover,the SA without pretreatment(control group,CK)was also performed for comparison.The water state and distribution in the SA during HPD were also explored using low-field nuclear magnetic resonance(LF-NMR).The results showed that the drying behavior of SA was typical in a falling rate stage,where in the internal moisture diffusion dominated the enrire drying.The Weibull model perfectly described the HPD process.Ethanol alone and combined with US and/or vacuum pretreatment enhanced the effective moisture diffusivity(Deff)and drying rate,compared with the CK.LF-NMR analysis revealed that the immobilized water was dominated in the SA.The transverse relaxation time of all the components was shifted left,whereas the proportion of the immobilized water decreased,but the tightly and loosely bound water and free water increased,as the drying progressed.The conversion of the immobilized water into the free one was more favored with the respective pretreatment,compared with the CK.There was a decrease in the yellowness,total color difference(ΔE),shrinkage rate(SR),hardness,springiness,and chewiness;but an increase in the lightness,redness,and rehydration ratio(RR)of the dried SA with ethanol alone and in combination with other pretreatment in comparison to the CK.Among them,the SA with US+E and USVC+E achieved the best color parameters(ΔE(7.40±0.22)and(6.99±0.16)for US+E and USVC+E,respectively),the lowest SR(35.97%±1.29%and 34.43%±1.24%for US+E and USVC+E,respectively)and hardness((25.20±1.08)N and(26.68±0.61)N for US+E and USVC+E,respectively);whereas the US+E performed the lowest springiness(0.55±0.01)and chewiness(7.27±0.30)N,but with the highest RR(1.753±0.022).Compared with the CK,the US+E significantly decreasedΔE by 58.24%,SR by 32.75%,hardness by 23.17%,springiness by 15.38%,and chewiness by 38.91%,whereas,there was an increase in the RR by 9.975%after 180-min rehydration.Overall,the US+E was recommended as the suitable non-thermal and green pretreatment of SA with a high DR and quality performances.