【作者】 李瑜；

【导师】 许时婴；

【作者基本信息】 江南大学 ， 食品科学， 2006， 博士

【摘要】 大蒜的保健和医疗价值很高,具有抗菌消炎、抗病毒、抗氧化、抑制血栓形成、抗肿瘤、防治动脉硬化、降血脂等多种生物活性功能,大蒜所具有的许多生物活性功能都归因于存在有机硫化物特别是硫代亚磺酸酯类(R-S-S(O)-R)。蒜素(二烯丙基硫代亚磺酸酯)是最主要的硫代亚磺酸酯类,大约占破碎大蒜所形成的总硫代亚磺酸酯的70%。本论文的目的是以新鲜大蒜为原料,采用微波真空与真空联合干燥技术制备高蒜素含量的大蒜粉,并采用微胶囊技术制备微胶囊蒜粉保健品,使其在食用过程中蒜氨酸酶在酸性胃液环境中不失活,从而使蒜氨酸全部转化为蒜素,以提高蒜素的人体利用率。论文首先对Lawson分光光度法定量测定蒜素及新鲜大蒜中总硫代亚磺酸酯进行了进一步的改良,通过改变半胱氨酸和DTNB的浓度以及延长反应时间提高测定的准确性和重现性,扩大了其应用范围,使其不仅可应用于新鲜大蒜中硫代亚磺酸酯的定量测定,也同样适用于大蒜提取物、蒜粉以及微胶囊化蒜粉中总硫代亚磺酸酯的定量测定。本文化学合成了蒜氨酸,采用此合成的蒜氨酸研究蒜氨酸酶的酶学性质。对新鲜大蒜、冷冻干燥大蒜片以及微波真空与真空联合干燥(MV/VD)大蒜中提取的蒜氨酸酶粗酶液酶学性质进行比较。采用Sephacryl S-200凝胶柱分别对新鲜大蒜中的蒜氨酸酶和MV/VD法干燥大蒜中的蒜氨酸酶进行一步分离纯化,获得纯化的新鲜大蒜以及MV/VD法干燥大蒜中的蒜氨酸酶。通过对蒜氨酸酶紫外/可见吸收光谱、荧光发射光谱和园二色性的特征研究,探讨了经过MVD处理后蒜氨酸酶的热稳定性提高、最适温度提高的机理。研究表明新鲜大蒜和冷冻干燥大蒜片中蒜氨酸酶的最适温度为40℃,MV/VD得到的干燥蒜片中的蒜氨酸酶的最适温度为45℃,且温度高于45℃时酶的热稳定性提高。反相HPLC测定结果表明,经Sephacryl S-200分离纯化得到的蒜氨酸酶可达较高的纯度;SDS-PAGE电泳也显示了新鲜大蒜和MV/VD法干燥大蒜经Sephacryl S-200分离纯化得到的蒜氨酸酶均达到电泳纯。对蒜氨酸酶紫外/可见光谱、荧光发射光谱和园二色性光谱扫描结果表明,经过MV/VD处理后蒜氨酸酶的分子构象更为有序,从而使得经过MV/VD处理后蒜氨酸酶的热稳定性和最适温度均提高了。蒜氨酸酶热失活动力学研究表明蒜氨酸酶是不耐高温的酶类。采用乙醇提取的硫代亚磺酸酯极不稳定,硫代亚磺酸酯在30℃条件下贮存极其不稳定,在4℃条件下贮存硫代亚磺酸酯可稳定12h,在-20℃条件下贮存30天后保留率为50%左右。采用DSC测定了硫代亚磺酸酯的玻璃化转变温度Tg’为-36.9℃,这解释了硫代亚磺酸酯在常温下贮存极不稳定的原因。采用微波真空干燥法(MVD)对薄层蒜片干燥动力学进行了研究。在不同的真空压力4kPa、6kPa、8kPa下,测定蒜片干燥过程中的温度,当真空度小于等于6kPa时,干燥蒜片中保留了大部分的蒜氨酸酶活性。大蒜片MVD动力学模型可采用Cui等提出的胡萝卜片的MVD动力学模型描述,由于干燥的临界水分含量不同,胡萝卜片的临界水分含量为XW=2(以干基计),大蒜片的临界水分含量为XW=1,因此在干燥后期必须对该数学模型更多还原

【Abstract】 The health care and medical treatment value of garlic are very high. It has antimicrobial, anti-inflammatory, antivirus, antioxidant, antithrombotic, anticancer, and antiatherosclerotic activities, as well as the capacity to lower serum lipid levels. Allicin occupied about 75% of total thiosulfinates in garlic. The aim of this work was to prepare of garlic powder with high allicin content using microwave-vacuum combined with vacuum drying technology and microencapsulating technology in order to protect alliinase activity throughout the stomach and improve the ratio of alliin transforming into allicin.Firstly, in this paper it has described a modified spectrophotometric assay for the determination of allicin and total thiosulfinates in fresh garlic. Improved the accuracy and reproducibility of the method by changing the concentration of crysteine and DTNB and prolonging reaction time. Also enlarged its using fields such as determination of thiosulfinates in garlic extract , garlic powder and microencapsulated garlic powder.Enzyme character of crude garlic alliinase from fresh, freeze dried and microwave vacuum drying combined with vacuum drying(MV/VD) were compared using chemical synthesized alliin. Garlic alliinase from fresh and MV/VD were purified using Sephacryl S-200 gel column and compared their spectral characteristic of ultraviolet/visible(UV/Vis), fluorescence and CD spectroscopy in order to explore the mechanism that both the heat stability and the optimal temperature of alliinase were increased after MV/VD. The results showed that the optimal temperature of alliinase from both fresh garlic and freeze dried garlic were 40℃, but alliinase of MV/VD was 45℃and when the temperature was above 45℃the heat stability increased. RP-HPLC result showed that the purity of alliinase through Sephacryl S-200 was very high, and SDS-PAGE electrophoresis results showed that alliinase achieved electrophoresis pure. The results of UV/Vis, fluorescence and CD spectroscopy of alliinase showed that MV/VD caused the conformation of alliinase was more orderly. That the reason why both the heat stability and the optimal temperature of alliinase were increased after MV/VD. The results of alliinase heat inactivation dynamics showed that alliinase belongs to intolerance high temperature enzyme. Thiosulfinates extracted by using ethonal was not stable. The thiosulfinates was very unstable at 30℃. When the thiosulfinates was stored at 4℃, it could stable for 12hrs. Even stored at–20℃for 30 days, the retention was only about 50%. The glass-transition temperature measured by DSC was–36.9℃. That can explain why thiosufinates was very instable at room temperature.MVD kinetics of garlic were studied. The internal temperature of garlic were measured during drying under differents vacuum pressure 4kPa、6kPa、8kPa, mostly of alliinase activity can be reserved keeping vacuum pressure below 6kPa. MVD kinetics of garlic can be described by using a theoretical model introduced by Cui. But the difference of drying critical point XW=2 (db) in carrot slices drying and XW=1 in garlic slices drying and must be modified by using a correction factor k=10.924e-3.2394Xw. Texture analysis and SEM measurement displayed the material texture and microstructure of fresh garlic, fresh carrot, garlic slices and carrot slices更多还原