【作者】 曹建平；

【导师】 董明盛；

【作者基本信息】 南京农业大学 ， 食品科学， 2008， 硕士

【摘要】 高压处理技术被认为是新的食品加工与保藏技术中最有潜力和发展前途的一种物理技术。超高压均质既能有效灭菌,又能较好的保留营养成分及色、香、味等。澳豆(Narrow-leafed lupin)中富含丰富的蛋白质和合理的氨基酸组成,在食品配方中作为一种重要的功能成分和食品添加剂广泛应用于食品工业。传统的加热杀菌易使大豆蛋白变性,易使蛋白饮料沉淀,从而影响产品的质量。本论文选择澳豆豆乳作为研究对象,运用多种分析检测手段,研究了压力、循环次数等因素对豆乳的物理、化学、微观结构特性的影响,为超高压均质在大豆制品加工中的应用、大豆蛋白的改性及食品安全提供理论依据;并探索了在脱脂奶中超高压均质与溶菌酶协同作用对微生物的影响,试图寻求一种新的食品冷杀菌新技术。本论文的实验和研究结果如下:1、超高压均质对澳豆豆乳理化性质、微生物及显微结构的影响以澳豆豆乳为食品体系,研究了超高压均质(UHPH)对澳豆豆乳理化性质、微生物及微结构性质的影响,结果表明在均质压力175MPa,循环次数为6条件下,豆乳中的菌落总数减少了4个log CFU/mL,正交试验表明压力对杀菌效果的影响最大。表示豆乳物性的参数有颜色、稳定性、表观黏度、颗粒大小。超高压均质处理的样品颜色都有所变化,在均质压力为175MPa,6个循环时,ΔE~*木与对照样相差1.63,从肉眼上就会感觉到有差异;澳豆豆乳经过超高压均质机处理后,表观黏度明显降低,稳定性提高。随着压力的不断增大,循环次数不断增多,豆乳中颗粒不断减小;透射电镜照片显示了胶体颗粒的分布和一般特性,超高压均质处理后没有发生聚合现象,在所有图片中看出颗粒大小与对照样相比,明显降低,蛋白在未处理样品中比超高压均质处理样品中更加分散。2、超高压均质与溶菌酶协同作用对微生物的影响研究了超高压均质与溶菌酶联合处理对以脱脂奶为培养基的G~-、G~+菌的影响。溶菌酶对细菌的最小抑制浓度(MIC)结果表明该溶菌酶对革兰氏阴性菌,革兰氏阳性菌都有不同程度的抑制作用。Escherichia coli、Lactobacillus plantarum对压力有抵抗力,Bacillus subtilis、Pseudmonas putida、Staphylococcus aureus对高压均质比较敏感。溶菌酶的添加提高了压力对所选菌株抗菌效果,此外,溶菌酶和超高压均质协同处理显著的影响了菌株的生长动力学特征。通过不同均质压力处理,比较生残菌菌落数,溶菌酶的添加提高了对G~-处理的效果。预均质的溶菌酶在75MPa下,10h时菌落数减少了1.93logCFU/mL,与对照相比酶的抗菌活性提高了。另一方面,菌与酶液在接触6h时,100MPa均质时,对植物乳杆菌的抗菌效果更好。初步地证明酶和高压均质有协同或交互作用,细菌总数的下降而不仅仅是由于均质压力对细菌细胞壁或细胞膜的作用。通过扫描电镜图观察到在130MPa时,菌体细胞质不均匀开始萎缩、变形,细胞膜破裂,或者细胞破碎。本实验结果证明不是两种因子的简单加和而是他们协同作用的结果。更多还原

【Abstract】 Dynamic high-pressure processing is considered as one of the most potential and promising physical modification technologies in the latest food processing and preservation development.In the process of ultra-high pressuree homogenization(UHPH) can not only kill food-borne microorganisms,but bring less detriment to food compounds such as nutrients,pigments,and flavoring agents,et al.Aussie bean is a full-nutrient food due to have abounding proteins and rational amino acids.So Aussie bean proteins are commonly used as a functional ingredient and additive for food formulation because of its excellent function properties and good nutritional values.Thermal preservation results in denaturation of proteins and precipitation of beverage containing protein,thus affects the quality of products.The lupin-milk has been studied by multiple analysis ways.The effects of high pressuree homogenization on the physicochemical and microstructural characteristics of lupin-milk have been analyzed,in order to provide the reference for the application of soybean products,modification of soybean protein,and food safety. Combined effect of lysozyme and high pressure homogenization on microorganism in model systems based on skim milk was discussed,too.And try to seek for a novelty nonthermal pasteurization technology.The experimental results of this paper are summarized showed as follows:1.Effects of ultra high pressure homogenization(UHPH) on physicochemical, microbial and microstructural characteristics of lupin-milkThe effects of ultra high pressure homogenization(UHPH) on physicochemical, microbial and microstructural characteristics of lupin-milk was studied and compared with lupin-milk(control) processed with conventional homogenization pressure(25MPa) used in industry.UHPH treated lupin-milks were compared with the control lupin-milk,and the result of microbiological quality showed that UHPH was reducing the total number of bacteria,reaching reductions of 4 logCFU/mL at 175MPa with 6 passes and results of levels of orthogonal experiment showed the pressure was the most effective on sterilization. Physicochemical parameters assessed in lupin-milk were viscosity,color,and particle size. Color differences between UHPH treatment and control were found that the UHPH treatments increased the L*,a*and△E* values and reduced the b* value of treated lupin-milk,moreover the maximum difference value of△E* between the treated and control was 1.63 which was noticeable difference.And the UHPH treatments induced a reduction in viscosity valuesk and a enhencement in physical stability index values of treated soymil compared with control.With the higher the pressure and the more passes employed,the smaller was the particle size.Images of transmission electron microscopy showed the distribution and general characteristics of the particles and structures of samples. No structures in coalescence process were observed after UHPH treatment.Differences of size and distribution of globules depending on the treatment applied to lupin-milk could be seen.More detailed images of protein could be observed,evidencing that the protein fraction in the continuous phase appeared more disperse that in UHPH lupin-milks.2.Combined effects of ultra high pressure homogenization and lysozyme on microorganismIt was studied the reduction of a population of Gram positive and Gram negative species inoculated in in skim milk by the combination of ultra-high pressure homogenization(UHPH) treatment and the use of lysozyme as antimicrobial.The minimum inhibitory concentration(MIC) of lysozyme against bacteria showed that lysozyme had a different extent of inhibition against Gram positive and Gram negative species.Escherichia coli.Lactobacillus plantarum were the most pressure resistant species,while Bacillus subtilis,Pseudomonasputida,Staphylococcus aureus were found to be very sensitive to the hyperbaric treatment.The enzyme addition enhanced the instantaneous pressure efficacy on almost all the considered species as indicated by their instantaneous viability loss following the treatment.Moreover,the combination of the enzyme and high pressure homogenization significantly affected the recovery and growth dynamics of several of the considered species.The enzyme addition enhanced the treatment efficacy on the Gram negative species as indicated by the comparison of data relative to surviving cells of samples homogenized at different pressures in the presence or absence of lysozyme.HPH-treated lysozyme(75MPa) reduced the cell load after 10h from treatment of 1.93 logcfumL in comparison with the control.On the other hand,a treatment at 100 MPa enhanced the lysozyme activity and induced,after an incubation of about 6 h,an increase of the L. plantarum deactivation rate with respect to the control.These results preliminary evidence that the interaction lysozyme-high pressure homogenization should not be attributed only to the effect of pressure on the integrity of the cell walls or outer membrane for the Gram negative species.As shown by the SEM(scanning electron microscopy) micrographs,at the pressure level applied(130 MPa) severe damages,including shrinkage of surface,rupture of parital cell wall,also the discharge of cytoplasmic content and even breakage of microbial cells,were observed.These results suggested that the combined effects of the process and enzymes cannot be attributed to a mere sum of their individual actions but to their synergetic effect.更多还原