【作者】 朱晨；

【导师】 陶能国；

【作者基本信息】 湘潭大学 ， 食品工程， 2022， 硕士

【摘要】 近年来,我国水果产业发展形势喜人,由于水果生产存在成熟季节相对集中、水分流失快和贮藏运输过程易受到病原菌侵染等问题,对水果产业的健康发展造成了一定的影响。特别是水果贮藏运输过程中使用传统化学杀菌剂的潜在危险已引起大众关注,亟待开发和应用新型绿色防腐保鲜技术。植物精油以其天然、安全、绿色及良好的抗菌抗氧化能力被认为是化学保鲜剂的替代品。然而,植物精油存在易挥发、难溶于水、高浓度处理易损伤果实表面等缺陷,限制了其在果蔬防腐保鲜中的应用。气凝胶具有多孔结构及较强吸附性能,可作为负载植物精油的理想载体。本研究以羧甲基纤维素钠(CMC-Na)为基材,聚乙烯醇(PVA)为疏水增强剂制备复合气凝胶,并对其结构进行表征。探讨了上述材料负载植物精油的缓释性能和抗菌抗氧化活性,并应用于柑橘,草莓和火龙果采后防腐保鲜,同时测定处理前后柑橘,草莓和火龙果果实品质和生理生化指标的变化。以期为水果贮藏保鲜领域提供新思路。主要研究结果如下:(1)CMC-Na/PVA复合气凝胶的制备与表征以CMC-Na和PVA(1:1,v/v)为原料,采用冷冻干燥法制备CMC-Na/PVA复合气凝胶,经电子扫描显微镜(SEM)、X射线衍射(XRD)、比表面积分析(BET)和红外光谱扫描(FTIR)分析表明:各组分间主要以氢键形式连接,不同分子间形成了共混骨架,且没有改变气凝胶的多孔结构。疏水测试表明复合气凝胶具有良好的疏水性,水滴在气凝胶表面形成球状水珠,且在300 s内一直保持球状形态。缓释实验表明CMC-Na/PVA复合气凝胶作为载体可以将精油的释放时间延长至15 d,平均释放速率为5.7%。(2)复合气凝胶负载植物精油对柑橘采后绿霉病的防治比较了4种植物精油两两组合(柠檬醛+肉桂醛、肉桂醛+香茅醛、肉桂醛+反式-2-己烯醛、香茅醛+反式-2-己烯醛、柠檬醛+香茅醛、柠檬醛+反式-2-己烯醛)的体外抑菌性能,并结合经济成本确定了植物精油最佳比例为香茅醛+肉桂醛(1:4,v/v),抑制指状青霉的最小抑菌浓度(MIC)和最小杀菌浓度(MFC)均为0.40μL/m L。CMC-Na/PVA复合气凝胶负载复配精油对柑橘进行熏蒸处理并在常温下贮藏30 d,测定贮藏期间内柑橘的生理生化变化,发现该处理能有效抑制贮藏期间柑橘绿霉病的发生、且对柑橘果实品质无不良影响。(3)复合气凝胶负载植物精油对草莓采后灰霉病的防治比较了反式-2-己烯醛、肉桂醛、香茅醛、丁香酚、香芹酚、月桂烯,β-芳樟醇和柠檬醛8种植物精油对草莓灰霉病原菌的MIC和MFC,发现反式-2-己烯醛的抑菌性能最佳,其抑制灰葡萄孢的MIC和MFC均为0.20μL/m L。CMC-Na/PVA复合气凝胶负载反式-2-己烯醛,对草莓进行熏蒸处理并在常温下贮藏6 d,测定贮藏期间内草莓的生理生化变化,发现该处理能抑制贮藏期间草莓灰霉病的发生、有效诱导果实过氧化物酶(POD)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和β-1,3-葡聚糖酶(GLU)等抗氧化及抗病性酶活性,且对草莓果实品质无不良影响。(4)复合气凝胶负载植物精油对火龙果采后炭疽病的防治比较了反式-2-戊烯醛、反式-2-己烯醛、反式-2-癸烯醛、反式-2-辛烯醛、枯茗醛、辛醛等11种植物精油对火龙果炭疽病原菌的MIC和MFC,确定反式-2-辛烯醛抑菌性能最佳,其抑制胶孢炭疽菌的MIC为0.30μL/m L,MFC为0.60μL/m L。CMC-Na/PVA复合气凝胶负载反式-2-辛烯醛,对火龙果进行熏蒸处理并在常温下贮藏15 d,测定贮藏期间内火龙果的生理生化变化,表明该处理能抑制贮藏期间火龙果炭疽病的发生,且对火龙果果实品质无不良影响。综上,本研究制备的CMC-Na/PVA复合气凝胶可作为载体使精油缓慢释放,该处理能显著降低三种南方水果果实腐烂率,且对果实品质无不良影响,可为植物精油控制水果采后腐烂提供新思路。更多还原

【Abstract】 In recent years,the fruit industry is developing rapidly.However,serious economic losses have been caused due to the relatively concentrated time of fruit production,the loss of water,and the infection of pathogenic fungus.The potential dangers of using traditional chemical fungicides during fruit storage have attracted public attention and it is necessary to develop and apply new preservation techniques.Essential oils are considered as the best substitute for chemical preservatives because of their natural,safety,green,antifungal and antioxidant abilities.However,due to the defects of essential oils such as poor stability,insoluble in water,volatile characteristics,and damage the fruit epidermis under highconcentration treatment,which limits their application in the preservation of fruits and vegetables.Aerogels have abundant pore sizes and strong adsorption properties,making them ideal materials as carriers of essential oils.In this paper,composite aerogels were prepared using sodium carboxymethyl cellulose(CMC-Na)as the substrate and polyvinyl alcohol(PVA)as the hydrophobic enhancer,then their structures were characterized and analyzed.The sustained-release properties and antifungal and antioxidant activities of the above materials loaded with essential oils were investigated,and applied to citrus,strawberry and pitaya for postharvest preservation,measuring the changes of physiological and biochemical indexes before and after the treatment of essential oils during storage,which can provide the new ideas for the fruit storage and preservation.The main research results are as follows:(1)Preparation and characterization of CMC-Na/PVA composite aerogelsCMC-Na/PVA composite aerogels were prepared by freeze-drying method,using CMC-Na and PVA(1:1,v/v)as basic materials.The analysis of Scanning Electron Microscopy(SEM),X-ray Diffraction(XRD),Brunauer-Emmett-Teller(BET)and Fourier Transform Infrared Spectrometer(FTIR)showed that the CMC-Na/PVA composite aerogels are mainly connected by hydrogen bonds,and the blending framework was formed between different molecules without changing the porous structure of the aerogels.The hydrophobic test showed that the composite aerogels had good hydrophobicity.Based on the above characteristic,the water could form spherical water droplets on the surface of the aerogel and maintain its shape within 300 s.The sustained-release experiment showed that the CMC-Na/PVA composite aerogels as the carrier could prolong the release time of essential oils to 15 days,with an average release rate of 5.7%.(2)The control of citrus postharvest green mold by CMC-Na/PVA composite aerogel loaded with essential oilThe in vitro antifungal properties of four combinations of essential oils(citral +cinnamaldehyde,cinnamaldehyde + citronellal,cinnamaldehyde + trans-2-hexenal,citronellal + trans-2-hexenal,citral + citronellal,citral + trans-2-hexenal)were compared.Combining with the cost of practical application,the optimal ratio of essential oil was determined as citronellal + cinnamaldehyde(1:4,v/v),whose minimum inhibitory concentration(MIC)and the minimum fungicidal concentration(MFC)against Penicillium digitorum were 0.40 μL/m L.Citrus fruits were fumigated by CMC-Na/PVA composite aerogels loaded with compound essential oils and stored at room temperature for 30 d.The physiological and biochemical changes of fruits during storage were measured,and it was found that the treatment could effectively inhibit the incidence rate of green mold during storage,and without adverse effect on citrus fruit quality.(3)Control of postharvest gray mold in strawberry by CMC-Na/PVA composite aerogel loaded with essential oilThe antifungal activities of eight kinds of essential oils including trans-2-hexenal,cinnamaldehyde,citronellal,eugenol,carvacrol,myrcene,β-linalool and citral,were compared against Botrytis cinerea were compared,of which trans-2-hexenal had the best antifungal activity,whose MIC and MFC were 0.20 μL/m L.CMC-Na/PVA composite aerogels loaded with trans-2-hexenal fumigated strawberries and stored at room temperature for 6 d.The physiological and biochemical changes of fruits during storage were measured,and it was found that the treatment could effectively inhibit the incidence rate of gray mold during storage and have no adverse effect on strawberry fruit quality.Moreover,treating with trans-2-hexenal effectively induced the activities of antioxidant and resistant enzymes such as peroxidase(POD),catalase(CAT),superoxide dismutase(SOD),and glucan1,3-β-glucasidase(GLU).(4)The control of postharvest anthracnose of pitaya by CMC-Na/PVA composite aerogel loaded with essential oil:The antifungal activities of eleven kinds of essential oils such as trans-2-pentenal,trans-2-hexenal,trans-2-decenal,trans-2-octenal,cuminal and octanal,MIC and MFC of pitaya anthracnose pathogen were compared,which trans-2-octenal had the best antifungal activity whose MIC and MFC were 0.30 μL/m L and 0.60 μL/m L,respectively.CMCNa/PVA composite aerogel loaded trans-2-octenal were fumigated to pitaya and stored at room temperature for 15 d.The physiological and biochemical changes of fruits during storage indicating that the treatment could inhibit the incidence rate of anthracnose and has no adverse effect on the quality of pitaya fruits.In conclusion,the CMC-Na/PVA composite aerogels prepared in this study can be used as the carrier to slowly release essential oils.This method can significantly reduce the decay rate of three southern fruits and without adverse effects on fruit quality,which can provide new ideas for essential oils to control postharvest diseases of fruits.更多还原