为延长精油的释放时间,增强其保鲜效果,该研究采用高压微射流技术制备柠檬醛纳米乳(citral nanoemulsion,C-NE),并考察其对砂糖桔贮藏品质的影响。以海藻酸钠为水相,柠檬醛和玉米油为油相,制得了粒径小于200 nm且可稳定分散的纳米乳。当柠檬醛含量为0.3%(质量分数)时,乳液粒径为130 nm,多分散性指数<0.3,Zeta电位为-50 mV。采用柠檬醛含量为0.1%、0.3%和0.5%(质量分数)的纳米乳分别对砂糖桔进行浸泡处理,并以未处理组(blank group,BG)、海藻酸钠处理组(sodium alginate,SA)和0.3%柠檬醛溶液处理组(0.3% citral,0.3%C)为对照,监测果实贮藏期间腐烂率、呼吸速率、失重率、硬度、营养物质含量、果皮中丙二醛含量以及抗氧化酶活性等指标的变化,以考察纳米乳处理对砂糖桔的保鲜效果。结果表明,与BG组和SA组相比,柠檬醛纳米乳处理可显著抑制果实的呼吸,降低其失重率,从而减少腐烂。其中,0.3%C-NE组在14 d贮藏期内果实的腐烂率均为0。同时,纳米乳处理有助于保持果实中的抗坏血酸含量,减少丙二醛的积累,且0.3%C-NE组在贮藏后期相较于其他组具有较高的抗氧化酶活性。研究证明,柠檬醛质量分数为0.3%的纳米乳可较好地发挥抑菌保鲜的作用,降低果实的呼吸强度并提高其抵御病原菌入侵的能力,从而显著抑制果实腐烂,在采后果实的贮藏保鲜中具有良好的应用潜力。
To prolong the release time of essential oil and enhance its preservation effect, citral nanoemulsion was prepared using high-pressure microfluidization technology, and its effect on the storage quality of Shatangju (Citrus tachibana Blanco) was investigated. Using sodium alginate as the aqueous phase and citral and corn oil as the oil phase, stably nanoemulsions with particle size less than 200 nm were prepared. When the mass fraction of citral was 0.3%, the particle size of the emulsion was 130 nm, the polydispersity index (PDI) < 0.3, and the Zeta potential was -50 mV. Shatangju fruits were treated by nanoemulsions containing 0.1%, 0.3%, and 0.5% citral (0.1% C-NE, 0.3% C-NE, and 0.5% C-NE), while the untreated group (BG), sodium alginate treated group (SA), and citral solution treated group (0.3%C) were prepared as controls. The effect of nanoemulsion treatment on the preservation of Shatangju was investigated by measuring the variations of the decay rate, respiration rate, weight loss, hardness, nutrient content, and malondialdehyde content in the peel and antioxidant enzyme activity during storage. Results showed that compared with BG and SA groups, citral nanoemulsion treatment significantly inhibited the respiration of fruits and reduced their weight loss, thus reducing their decay. Especially, the decay rate of 0.3% C-NE group during the 14 d storage period was 0. Meanwhile, nanoemulsion treatment helped maintain the ascorbic acid content in fruits and reduced the accumulation of malondialdehyde. The 0.3% C-NE group also had higher enzyme activity in the late storage period compared to the other groups. This indicated that the nanoemulsion with a citral concentration of 0.3% had a good antibacterial and preservation effect, which could reduce the respiration of fruits and improve the resistance of fruits against pathogenic bacteria, thus significantly reducing the decay of the fruit. Therefore, the citral essential oil nanoemulsion has good potential for the preservation of postharvest fruits during storage.
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