MCM-41分子筛催化D-葡萄糖酸制备D-葡萄糖酸-δ-内酯的研究

以MCM-41分子筛为催化剂,由D-葡萄糖酸制备D-葡萄糖酸-δ-内酯.考察了反应温度、反应时间、催化剂用量以及催化剂循环使用次数对D-葡萄糖酸-δ-内酯产率的影响.实验结果表明,MCM-41是制备D-葡萄糖酸-δ-内酯较好的催化剂.最佳工艺条件为:催化剂用量为30%,反应温度80℃,反应时间2h,D-葡萄糖酸-δ-内...     

δ-葡萄糖酸内酯添加量对豆腐凝胶特性的影响

以内酯豆腐为研究对象,在豆浆中添加不同比例(0.2%、0.3%、0.4%)的δ-葡萄糖酸内酯(GDL),通过质构仪、SDS-PAGE、红外光谱、激光扫描共聚焦显微镜等仪器,对其组织结构、含水量和保水性、凝胶作用力组成、蛋白质亚基组成、二级结构和微观结构进行测定,分析GDL添加量对豆腐凝胶特性的影响。结果表明,随着GDL添加量的增加,其硬度、弹性和咀嚼性显著提高(P<0.05),当GDL添加量为0.4%时,保水性最好,达到了83.38%,豆腐中疏水作用逐渐增强,可溶性蛋白的亚基条带逐渐减少,蛋白质向凝胶转化的趋势增大,豆腐蛋白质中β-折叠含量由31.93%增加到38.43%,无规则卷曲含量由13.93%下降到13.78%。     

多功能食品添加剂──D-葡萄糖酸-δ-内酯

本文介绍了D-葡萄糖酸-δ-内酯的理化性质、生产工艺和在食品工业中的应用。最后提出了我国研究和发展D-葡萄糖酸-δ-内酯的几点建议。     

高效液相色谱法测定食品中的葡萄糖酸-δ-内酯

建立了一种高效液相色谱法检测食品中葡萄糖酸-δ-内酯的方法。采用有机酸柱(4.6mm×250mm,5μm),流动相为0.01mol/L磷酸二氢钾-磷酸缓冲液(ph=6.2),流速:0.8m L/min,采用内部温度为35℃示差检测器。测定了肉与肉制品、豆制品、运动饮料等食品,结果显示方法线性关系良好,检出限为7.5mg/kg,测定结果的相对标准偏差为0.5%~1.9%(n=6),回收率在87%~95%之间。方法具有灵敏度高、定性准确的优点,适合食品中葡萄糖酸-δ-内酯的检测。     

葡萄糖酸δ内酯在乳化香肠中的应用

在乳化型香肠的制作过程中,首先须将肉绞碎。随后通过乳化机、斩拌机或搅拌机使瘦肉蛋白包裹脂肪颗粒,如果酸度过高,接近蛋白质的等电点,就会影响蛋白质的乳化功能,使成品中出现许多游离脂肪颗粒,产品质量下降。因此在绞肉、乳化、灌肠过程中,就不能加入酸性较     

姜汁凝乳影响因素的研究

生姜经清洗、打浆榨汁后可制得姜汁,将姜汁以2%的比例添加到经杀菌和冷却处理的鲜乳中可制成具有凝乳状态的姜汁牛乳。为了探讨姜汁凝乳的影响因素,文中研究了温度、pH值、牛乳蛋白质和盐类等对姜汁凝乳的影响。结果表明,温度和pH值是影响姜汁凝乳的关键外部因素。牛乳蛋白质、CaCl2、NaCl是凝乳促进物。     

乳蛋白多态性和盐分布对牛乳凝乳性能的影响

研究不同基因型乳蛋白对牛乳凝乳特性的影响规律。采集1 071 头荷斯坦奶牛血样,分析κ-酪蛋白（κ-casein,κ-CN）和β-乳球蛋白（β-lactoglobulin,β-LG）的基因型,在明确基因型的基础上,采集样品开展牛乳凝乳能力评价。在初步筛选的基础上,选择凝乳性能好、凝乳性能差和不凝乳样品各至少30 份,重复3 次,开展凝乳流变学特性、蛋白多态性及矿物离子分布分析。通过动态流变仪、电感应耦合等离子体质谱仪、毛细管电泳、高效液相色谱技术分析不同凝乳等级牛乳的凝乳时间,胶体钙、镁、磷含量差异,不同基因型导致蛋白多态性及含量对牛乳凝乳能力的影响。结果显示,在所有奶牛组中,β-LG的AB基因型（占比48.48%）最常见,但AA型基因（30.97%）的原料乳凝乳效果较好;κ-CN的BB基因型（12.00%）凝乳效果较好,较AA、AB等其凝乳时间更短和凝胶强度更强。凝乳性能好的样品中CN含量及胶体钙含量较高,pH值较凝乳性能差和不凝乳样品低,凝乳时间与κ-CN含量呈反比,酪蛋白和乳清蛋白组成和基因频率的变化会影响牛乳凝乳性能的变化。     

Milk Coagulation Properties and Milk Protein Genetic Variants of Three Cattle Breeds/Types in Sri Lanka

Milk coagulation is the primary step in the development of most dairy products. Raw milk from individual cows and different breeds exhibit distinct coagulation capacities. This variation is largely influenced by milk protein genetic variants. The aim of the present study was to evaluate differences in coagulation properties between milk obtained from three cattle breeds/types found in Sri Lanka. A total of 90 milk samples (400 mL from each individual) were collected from two Sri Lankan cattle breeds/types (Thamankaduwa White/TW and Local/“Batu” cattle) and one European cattle breed (Friesian). Collected samples were subjected to enzymatic coagulation using commercial rennet source (Chymax®, Christian Hansen Standard, Denmark) and lactic acid bacteria (LAB) coagulation using a commercial starter culture(YFL 8 12,Christian Hansen Standard, Denmark) to determine milk coagulation properties. Different properties of milk coagulum such as yield, curd firmness, syneresis and rheological properties were evaluated. The biochemical composition (lactose, protein, fat, solid-non-fat) of milk samples were determined. Capillary Zone Electrophoresis (CZE) method was used to determine milk protein genetic variants. Experimental design was Nested Completely Randomized Design with three treatments. Milk coagulation time and curd firmness after enzymatic-coagulation were not significantly different (p>0.05) among the breeds. Coagulum yield was significantly higher (p<0.05) for the TW type than that of other breeds. Coagulum yield was negatively correlated with β-caseinA1 and α-lactalbumin in both enzymatic (-0.58) and LAB coagulation (-0.69). Coagulum yield was positively correlated (p<0.05) with β-casein B variant (0.70), protein (0.34) and lactose (0.36) contents. Meltability value was weakly and positively (p<0.05) correlated (0.34) with fat content of milk. Overall results indicate that there is a significant correlation between milk coagulation properties and milk protein genetic variants in three cattle breeds/types considered in the current study. TW type is the unique among studied breeds in terms of coagulation properties and milk protein genetic variants.     

Optimizing Processing Conditions for Milk Coagulation Using the Hot Wire Method and Response Surface Methodology

ABSTRACT: :
To evaluate the relationship between the factors affecting coagulation, the hot wire method was used for direct measurements of the renneting milk process as well as a central composite design with 3 factors: rennet concentration (x₁), renneting pH (x₂), and temperature (x₃). Second-order models for maximum voltage (Y₁), time at maximum voltage (Y₂), and coagulation time (Y₃) were employed to generate response surface contours. Optimum conditions for cutting time were found with x₁= 0.0278 R.U./mL milk, x₂= 6.60, and x₃= 35 °C, for which the responses were Y₁= 2854 ± 171 μV, Y₂, = 14.08 ± 3.04 min, and Y₃= 7.16 ± 1.12 min. No significant differences (p > 0.01) were found between the 3 responses obtained in the experiment and the ones predicted by the models. The use of the objective and non-destructive monitoring of curd formation and the response surface methodology can be recommended to optimize milk coagulation.     

免疫乳及其制品研究

本研究选择人肠道致病性大肠杆菌７株，沙门氏菌２株和轮状病毒１株作为免疫原制成混合疫苗对泌乳母牛进行系统免疫，以刺激机体产生特异性ＩｇＧ进入乳中，研究结果表明，在试验期内（产犊后２１０天）经免疫处理的乳牛，其常乳中ＩｇＧ活性平均为３７９．５５，而非免疫牛乳中ＩｇＧ活性平均为４８，免疫处理后乳中免疫球蛋白活性提高８倍。对免疫中ＩｇＧ热致变性研究表明，免疫乳中ＩｇＧ热变性属零级反应，变性活化能平均为１３     

牛初乳鲜奶生产中稳定剂的应用研究

以产牛生产后1～3d的混合牛乳为原料,采用在牛初乳混合样中添加不同剂量的磷酸氢二钠、瓜尔胶、CMC（羧甲基纤维素）、卡拉胶、乳糖的方法,通过热凝固时间法（HcT）来测定牛初乳的热稳定状况,从而判定各稳定剂在牛初乳中的使用效果,为进行牛初乳鲜奶的研制奠定基础。研究表明：磷酸氢二钠、CMC（羧甲基纤维素）、乳糖的添加使用,对提高牛初乳的热稳定性效果显著。     

乳酸亚铁微胶囊化及对液态奶感官性状影响研究

以β-环状糊精、明胶、单甘酯、蔗糖脂肪酸酯为壁材而制成的乳酸亚铁微胶囊，可作为液态奶的铁强化剂。试验采用L9（3）^4正交设计，结果表明：乳酸亚铁微胶囊化的最佳配方为β-环状糊精86．4％、单甘酯1．0％、明胶10．8％、蔗糖脂肪酸酯1．2％，对乳酸亚铁的包埋效果最好。包埋率、有效铁相对含量分别为96．05％、10．33％，差异显著（p〈0．05），对液态奶的感官性状无影响。     

日本乳与乳制品安全标准研究

介绍了日本乳与乳制品安全标准的情况,并阐述了日本乳等法规的颁发部门及条令的基本框架,以及乳制品安全相关指标的规定。     

乳蛋白基因多态性对加工与营养的影响

综述了乳蛋白基因多态性和检测方法以及其对乳品加工及人类营养影响的研究进展。酪蛋白的基因型较多,除了基因差异外,还有磷酸化水平与糖基化程度等其他影响因素。乳清蛋白部分,β-乳球蛋白(-βLG)的基因型较多,而α-乳白蛋白(-αLA)的基因型较少。乳蛋白基因多态性可从蛋白水平和基因水平两方面进行检测。乳蛋白基因型会显著影响乳的加工特性,包括热稳定性、凝乳性能及干酪的产率和品质。乳蛋白基因与人类营养息息相关,随着分子技术的发展,基因多态性的应用会更广,需进一步的研究来更好地描述多态性与乳品加工及营养之间的关系。     

嗜酸乳杆菌发酵乳增酵因子的研究

以质量浓度100g／L脱脂乳为基础培养基，研究了添加不同比例和种类的维生素、氨基酸、蛋白质及糖类等营养素对嗜酸乳杆菌产酸能力及凝乳时间的影响。结果表明：乳糖0．5％、泛酸0．08％、半胱氨酸1％、大豆蛋白胨0．25％可使发酵乳凝乳时间从18-24h缩短到4h，pH值达4．30～5．25，因此该四种营养素可作为嗜酸乳杆菌发酵乳的增酵因子。