牦牛乳乳糖酶解及其预热处理条件优化

针对牦牛乳热处理和乳糖酶解问题,采用夏河鲜牦牛乳为原料,以乳糖水解速率(V0)和微生物数量为评价指标,探究牦牛乳乳糖酶解预热处理参数,并以乳糖水解率为目标对酶解条件进行优化。结果表明:牦牛乳经适宜条件热处理能明显增强外源乳糖酶酶解活性,65℃热处理5 min后酶解乳糖,V0升高49.0%。结合实际生产需求,乳糖酶解前对牦牛乳分别进行高温短时和低温长时巴杀处理,确定预热处理参数为85℃,13 s;优化得到酶解条件为:酶解温度39℃,酶解时间2.4 h,酶添加量2.4 u/m L,乳糖水解率达(79.7±0.9)%,相比未经热处理牦牛乳中同等条件,酶解率升高11.2%~14.0%,且水解率达标(≥70%)时间缩短0.75 h。     

固定化酶生产低乳糖牛乳的研究

以离子交换树脂D151为载体,采用吸附交联法固定化黑曲霉来源乳糖酶,并将固定化酶装填于填充床反应器中处理牛乳,研究固定化酶连续生产低乳糖乳的条件和使用稳定性.试验结果表明:在50℃下,牛乳以0.53 mL/min的流速通过反应器生产低乳糖乳效果最好,可获得79.7%的乳糖水解率,达到低乳糖乳的要求.固定化酶在最适条件下连续水解牛乳,每隔20 h用pH 6.5缓冲液清洗反应柱,其10d内酶活力丧失12%,此时乳糖水解率为70.1%,达到低乳糖乳的要求.固定化乳糖酶连续使用半衰期约为22d.该研究为工业化利用固定化酶连续生产低乳糖乳提供了技术依据.     

处理条件对芝麻素酚三糖苷稳定性的影响

探讨光、热、氧(空气)、酸、碱、酶及高压蒸汽处理对芝麻素酚三糖苷稳定性的影响。结果发现,光、热、氧(空气)、碱液(氢氧化钠)、高压蒸汽及α-葡萄糖苷酶处理对芝麻素酚三糖苷稳定性无显著性影响,盐酸、β-葡萄糖苷酶、α-半乳糖苷酶及β-半乳糖苷酶处理均可导致芝麻素酚三糖苷稳定性显著性降低。表明芝麻素酚三糖苷在特定的酸或酶作用下不稳定,可以转化为其他物质。     

植物乳杆菌透性化细胞催化生产低聚半乳糖的工艺优化

以乳糖为底物,利用含β-半乳糖苷酶的植物乳杆菌透性化细胞催化生产低聚半乳糖(GOS).在5L发酵罐上进行了以乳糖为碳源的植物乳杆菌WZ011的厌氧培养,β-半乳糖苷酶产量在发酵14 h时达到最大值5 U/mL.收获的植物乳杆菌菌体用于透性化全细胞催化生产GOS的研究.比较了乙醇、Tween 80、SDS、DMSO、丙酮这五种渗透剂对胞内β-半乳糖苷酶酶活的影响.结果表明以40％乙醇作为渗透剂处理最为有效,β-半乳糖苷酶胞内酶活可达500 U/g(细胞干重DCW).进一步对40％乙醇渗透处理后整细胞催化生产GOS的工艺条件进行了研究,结果表明乳糖浓度、初始pH、温度和反应时间对GOS合成均有显著影响.在乳糖质量浓度为400g/L,初始pH为7.0,温度50℃及反应进行10h的条件下,GOS产量达到最大值32％(质量分数).     

固定化乳糖酶制备低乳糖牛奶的研究进展

不同来源的β-半乳糖苷酶已经用于水解牛乳或乳清中的乳糖。酶水解乳糖的基本产物为葡萄糖和半乳糖。经水解后的乳糖增加了产品的甜度并使得牛乳适于那些患乳糖不耐症的人群。由于用游离乳糖酶会使牛奶掺入外来蛋白以及使用游离乳酶酶提高了生产成本,从而使乳糖酶的应用受到限制。将乳糖酶固定化后既可以重复使用,又能连续操作,且缩短了处理时间,从而明显降低了使用成本,因此对于乳糖酶的固定化受到了酶学专家的关注。本文简要介绍了乳糖和乳糖酶及其分类、乳糖酶的固定化方法及其应用,包括包埋法、交联法、吸附法、结合法及多种方法的混合使用及国内外的研究现状,并简要介绍了固定化乳糖酶的清洗。     

破壁方法对嗜热链球菌SP1.1胞内乳糖代谢关键酶活性的影响及其条件优化

通过超声波破壁法、溶菌酶破壁法、反复冻融法和机械破壁法4种不同破壁方式对嗜热链球菌SP1.1进行破壁处理,对菌体的破壁率、提取的β-半乳糖苷酶和乳酸脱氢酶两种胞内酶的活力进行分析比较,以确定适合于嗜热链球菌细胞破壁方法及其最佳条件。结果表明：这4种菌体细胞破壁效果存在很大差异,其中经溶菌酶处理胞内酶提取效果最好,破壁率可达99.87%,β-半乳糖苷酶酶活力为0.387U,乳酸脱氢酶酶活力为2.375U,与其他3种方法的破壁效果差异极显著(P＜0.01)。优化溶菌酶破壁条件,当处理8mL菌浓度为1.3×109CFU/mL的样品时,确定处理最佳温度为37℃,时间为30min,酶(20000U/mL)用量为1mL,此时破壁率可达99.99%,β-半乳糖苷酶酶活力为0.429U,乳酸脱氢酶酶活力为2.431U。     

酶解制备低乳糖牛奶的优化研究

针对低乳糖牛奶制备中的酶解工艺进行优化研究,采用正交试验设计考察了乳糖酶用量、酶解时间、酶解温度和pH等因素对乳糖水解率的影响。试验结果表明,最佳酶解工艺条件为：乳糖用量4000Nlu/L,酶解时间3h,酶解温度39℃,pH6.8,乳糖水解率可达76.6%,达到生产低乳糖牛奶产品的要求,满足乳糖不耐受症患者的需求。     

乳糖酶特性的研究

从脆壁酵母菌中提取得乳糖酶,其特性:酶最适温度45℃,最适pH值6.5,酶水解乳糖所需的最适乳糖浓度为15%。温度、pH、乳糖浓度和酶浓度对酶水解乳糖影响程度的大小顺序是;pH＞酶浓度＞温度＞乳糖浓度。K+、Na+、Mg++、Mn++对酶有明显的激活作用,Ca++有抑制作用,而微量Ca++（1.0mM）表现激活作用。40℃、0.4%和0.6%酶量水解含乳糖15%的乳清以及30℃C、0.3%酶量水解15%乳糖水溶液,在5小时之内,乳糖水解率均可达80%,达到商业要求。     

α-半乳糖苷酶辅助饱和硫酸铵法制备IgG及其活性研究

以新鲜牦牛血为原材料,采用α-半乳糖苷酶辅助饱和硫酸铵盐析处理获得免疫球蛋白G(immunoglobulin G,IgG),选取酶解时间、酶解pH、酶解温度、酶添加量4个因素,在4个单因素的基础上,利用响应面分析法,得到α-半乳糖苷酶辅助饱和硫酸铵法制备IgG的最佳酶解条件。并采用ELISA方法检测经过酶处理后样品IgG活性含量。结果表明,酶解时间2h、酶解pH 4.4、酶解温度39℃、酶添加量5mL(467.5 U),在该工艺条件下,IgG的含量最高,可达27.13mg/mL,比不加酶处理IgG含量(22.35 mg/mL)提高了21.39%(P0.05)。经过酶处理后样品IgG活性含量为15.92mg/mL,比不加酶处理IgG活性含量(16.07 mg/mL)下降了0.93%。     

微胶囊化的嗜酸乳杆菌在极端环境下的生理特性研究

研究了嗜酸乳杆菌NCFM菌株经胶囊化处理后对逆境的抵抗能力。结果表明,经pH值为2.5的酸处理后,微胶囊化菌株的活菌数(6.4×108 mL-1)、酸度(95oT)和!-半乳糖苷酶活力(0.127 mmol/g.min),明显高于对照菌株(P<0.01)的活菌数(2.3×108 mL-1)、酸度(56 oT)和!-半乳糖苷酶活力(0.078 mmol/g.min);经质量浓度为14 g/L的胃蛋白酶处理后,与对照菌株的活菌数(7.8×108 mL-1)、酸度(70 oT)和!-半乳糖苷酶活力(0.01 mmol/g.min)相比,微胶囊化菌株的活菌数、酸度、!-半乳糖苷酶活力明显提高(P<0.01),分别为1.41×109 mL-1,119 oT和0.075 mmol/g.min;经质量分数为0.4%胆盐处理后,微胶囊化菌株的活菌数(4.8×108 mL-1)、酸度(98 oT)和!-半乳糖苷酶活力(0.97 mmol/g.min),明显高于对照菌株(P<0.01)的活菌数(2.9×108 mL-1)、酸度(52 oT)和!-半乳糖苷酶活力(0.43 mmol/g.min);经质量浓度为3 g/L胰蛋白酶处理后,与对照菌株的活菌数(0.2×107 mL-1)、酸度(48 oT)和!-半乳糖苷酶活力(0.017 mmol/g.min)相比,微胶囊化菌株的活菌数、酸度、!-半乳糖苷酶活力显著提高(P<0.01),分别为3.5×108 mL-1,90.8 oT和0.1 mmol/g.min;经质量分数为18%的NaCl溶液处理后,微胶囊化菌株的活菌数(11.7×108 mL-1)、酸度(102 oT)和!-半乳糖苷酶活力(0.52 mmol/g.min),明显高于对照菌株(P<0.01)的活菌数(0.37×108 mL-1)、酸度(38 oT)和!-半乳糖苷酶活力(0.18 mmol/g.min)。显然,微胶囊化处理能明显提高嗜酸乳杆菌在极端环境下的存活能力。     

乳清饮料

介绍了利用多种类型的乳清（包括天然的干酪乳清、干酪素乳清、超滤乳清透过液或保留液、超滤乳清蛋白浓缩物或粉、脱盐的或脱蛋白的乳清粉等等）以制备各种类型的饮料（包括清澄透明的、乳状液型的、乳酸发酵的、酒精性发酵的、充入CO2的等等）,达到高营养、高生理价值、良好风味的乳清饮料。证明乳清饮料今后开发前景广阔。     

Factors regulating astringency of whey protein beverages

A rapidly growing area of whey protein use is in beverages. There are 2 types of whey protein-containing beverages: those at neutral pH and those at low pH. Astringency is very pronounced at low pH. Astringency is thought to be caused by compounds in foods that bind with and precipitate salivary proteins; however, the mechanism of astringency of whey proteins is not understood. The effect of viscosity and pH on the astringency of a model beverage containing whey protein isolate was investigated. Trained sensory panelists (n = 8) evaluated the viscosity and pH effects on astringency and basic tastes of whey protein beverages containing 6% wt/vol protein. Unlike what has been shown for alum and polyphenols, increasing viscosity (1.6 to 7.7 mPa·s) did not decrease the perception of astringency. In contrast, the pH of the whey protein solution had a major effect on astringency. A pH 6.8 whey protein beverage had a maximum astringency intensity of 1.2 (15-point scale), whereas that of a pH 3.4 beverage was 8.8 (15-point scale). Astringency decreased between pH 3.4 and 2.6, coinciding with an increase in sourness. Decreases in astringency corresponded to decreases in protein aggregation as observed by turbidity. We propose that astringency is related to interactions between positively charged whey proteins and negatively charged saliva proteins. As the pH decreased between 3.4 and 2.6, the negative charge on the saliva proteins decreased, causing the interactions with whey proteins to decrease.     

Whey beverages decrease blood pressure in prehypertensive and hypertensive young men and women

Whey protein beverages reduced blood pressure in young men and women in a six week controlled intervention. There were no differences in systolic blood pressure (SBP), diastolic blood pressure (DBP), or mean arterial pressure (MAP) observed between groups consuming 28 g per day of either hydrolyzed or non-hydrolyzed whey protein in a beverage. However, in young adults with elevated DBP and SBP, whey beverage consumption significantly decreased SBP, DBP, and MAP by 8.0, 8.6, and 6.4 mm Hg, respectively (P ≤ 0.001 for all comparisons). In subjects with elevated SBP only, SBP significantly decreased by 3.8 mm Hg (P ≤ 0.04) after the whey beverage intervention. Subjects with normal blood pressure had no change in SBP, DBP, and MAP. Whey beverages also significantly decreased total and low-density lipoprotein cholesterol concentrations (P ≤ 0.001 and 0.05, respectively). Whey protein beverages may be useful for the dietary treatment of prehypertension and/or stage 1 hypertension.     

牦牛乳清固体饮料的配方设计及优化

为了充分利用牦牛乳清,开发出一种良好口腔刺激感的片状固体饮料。以牦牛乳生产甜干酪时排出的副产物乳清液为基础原料,45 ℃旋转蒸发,-55 ℃真空冻干成粉。采用感官加权总分为评价指标,通过单因素试验、L₉(34)正交试验和Box-Behnken响应面优化,确定饮料片的最佳工艺配方。结果表明,乳清粉添加量、阿斯巴甜添加量和崩解剂添加量对饮料片感官加权评分影响极显著(P<0.001)。最佳工艺参数为:28.75%的乳清粉,43.75%的崩解剂,2.75%的阿斯巴甜,8%的聚乙二醇6000,酸碱比为1.24:1,感官加权总分为4.04。产品直径约10 mm,重约0.50 g/片,崩解时间小于120 s,发泡量大于8 mL,料液pH为6.42,色泽透亮,香味怡人,口感清爽。该结果可作为指导乳清固体饮料生产的理论依据,为功能性乳清的开发提供应用潜能。     

Preference Mapping of Lemon Lime Carbonated Beverages with Regular and Diet Beverage Consumers

The drivers of liking of lemon‐lime carbonated beverages were investigated with regular and diet beverage consumers. Ten beverages were selected from a category survey of commercial beverages using a D‐optimal procedure. Beverages were subjected to consumer testing (n = 101 regular beverage consumers, n = 100 diet beverage consumers). Segmentation of consumers was performed on overall liking scores followed by external preference mapping of selected samples. Diet beverage consumers liked 2 diet beverages more than regular beverage consumers. There were no differences in the overall liking scores between diet and regular beverage consumers for other products except for a sparkling beverage sweetened with juice which was more liked by regular beverage consumers. Three subtle but distinct consumer preference clusters were identified. Two segments had evenly distributed diet and regular beverage consumers but one segment had a greater percentage of regular beverage consumers (P < 0.05). The 3 preference segments were named: cluster 1 (C1) sweet taste and carbonation mouthfeel lovers, cluster 2 (C2) carbonation mouthfeel lovers, sweet and bitter taste acceptors, and cluster 3 (C3) bitter taste avoiders, mouthfeel and sweet taste lovers. User status (diet or regular beverage consumers) did not have a large impact on carbonated beverage liking. Instead, mouthfeel attributes were major drivers of liking when these beverages were tested in a blind tasting. Practical Application : Preference mapping of lemon‐lime carbonated beverage with diet and regular beverage consumers allowed the determination of drivers of liking of both populations. The understanding of how mouthfeel attributes, aromatics, and basic tastes impact liking or disliking of products was achieved. Preference drivers established in this study provide product developers of carbonated lemon‐lime beverages with additional information to develop beverages that may be suitable for different groups of consumers.     

板栗水解液乳酸发酵饮料的加工研究

采用单因素试验,结合正交试验对板栗水解液乳酸发酵饮料的加工进行研究。试验表明,板栗的破碎程度对水解液的褐变程度及水解过程有影响。破碎程度越大,水解液的褐变程度越大,水解液的固形物含量越高。发酵温度、发酵时间及发酵基质配比对板栗发酵饮料的质量亦有影响。随着发酵时间的延长,发酵温度的增大,产品酸度增大,酸味增加,饮料风味有所改善。板栗水解液乳酸发酵的适宜条件为板栗水解液:牛奶比为1:1,发酵温度45℃,发酵时间4h。     

由软饮料之现状谈其发展创新

2006年的新年钟声已经敲响，2005年软饮料产销道路已经甩在了我们身后，不妨回过头去看看已经走过的路线，看看这条道路的曲直起伏，为以后的发展找准起点和方向。     

我国市售饮料中游离糖含量研究

目的 了解我国市售饮料中游离糖及其单体的含量,为游离糖摄入及其风险评估提供基础数据,为制定完善相关政策提供科学依据.方法 根据我国饮料行业产销量并结合地理分布,2015年采集9类饮料样品共计708份;根据美国分析化学家协会(AOAC)2000.17方法,以高效离子色谱-脉冲安培检测法测定其中的单糖和二糖(葡萄糖、果糖、...     

Production of an exopolysaccharide-containing whey protein concentrate by fermentation of whey

Using whey as a fermentation medium presents the opportunity to create value-added products. Conditions were developed to partially hydrolyze whey proteins and then ferment partially hydrolyzed whey with Lactobacillus delbrueckii ssp. bulgaricus RR (RR; an EPS-producing bacterium). In preliminary experiments, pasteurized Cheddar cheese whey was treated with Flavourzyme to partially hydrolyze the protein (2 to 13% hydrolyzed). Fermentation (2 L, 38 degrees C, pH 5.0) with RR resulted in EPS levels ranging from 95 to 110 mg of EPS per liter of hydrolyzed whey. There were no significant differences in the amount of EPS produced during fermentations of whey hydrolyzed to varying degrees. Since a high level of hydrolysis was not necessary for increased EPS production, a low level of hydrolysis (2 to 4%) was selected for future work. In scale up experiments, whey was separated and pasteurized, then treated with Flavourzyme to hydrolyze 2 to 4% of the protein. Following protease inactivation, 60 L of partially hydrolyzed whey was fermented at 38 degrees C and pH 5.0. After fermentation, the broth was pasteurized, and bacterial cells were removed using a Sharples continuous centrifuge. The whey was then ultrafiltered and diafiltered to remove lactose and salts, freeze-dried, and milled to a powder. Unfermented hydrolyzed and unhydrolyzed whey controls were processed in the same manner. The EPS-WPC ingredients contained approximately 72% protein and 6% EPS, but they exhibited low protein solubility (65%, pH 7.0; 58%, pH 3.0).     

Whey protein hydrolysate: Functional properties,nutritional quality and utilization in beverage formulation

The objective of the study was to analyze the functional and nutritional properties of enzymatically hydrolyzed whey protein concentrate (WPC) and to formulate a beverage mix. WPC hydrolysates were produced using fungal protease and papain, at time intervals of 20, 40 and 60 min and were analyzed for proximate composition and functional properties. A beverage was formulated with hydrolyzed WPC, skim milk powder, cocoa, liquid glucose, sugar and vegetable fat and analyzed for physicochemical properties, sensory attributes and keeping quality. Results revealed that the protein content of WPC was 75.6% and decreased slightly on enzyme treatment (69.6%). The water absorption capacity of WPC was 10 ml/100 g and increased in enzyme treated samples from 16 to 34 ml/100 g with increase in the time of hydrolysis. Emulsion capacity (45 ml of oil/g of control WPC) showed a decreasing trend with increasing time of hydrolysis. Enzyme treatment slightly increased the foam capacity in three samples but lowered foam stability in all. The gel filtration pattern of enzyme treated samples showed an increase in low molecular weight fractions. The amino acid profile showed higher content of methionine in samples treated with enzymes, compared to the control. The in vitro protein digestibility of untreated WPC was 25% and increased in all treated samples to varying degrees (69–70%). Formulated beverage had 52% protein, 10% fat and 6.6% ash. There were no significant differences in the sensory attributes of formulated and commercial beverage. The formulated beverage could be stored well in a PET container for 30 days.