全脂乳粉和脱脂乳粉在1kHz～10MHz下的介电特征研究

分别研究了各4种不同品种的全脂乳粉和脱脂乳粉在1kHz～10MHz波段的介电特性。结果发现:随着频率的增加,全脂乳粉和脱脂乳粉的ξ’和ξ″值呈单调递减趋势;全脂乳粉的ξ’和ξ″值都高于脱脂乳粉,相同类型乳粉各品种间的ξ’和ξ″差异不大;全脂乳粉的ξ″值在103～105Hz频率段减小趋势明显,且ξ″值的对数与频率的对数成线性反比关系,而脱脂乳粉无此规律;全脂乳粉和脱脂乳粉的穿透深度Dp随频率的提高而减小,两类乳粉的介电特性差异可能与它们各自的脂肪和乳糖含量有关。      

915MHz和2450MHz下扇贝柱介电特性的研究

利用介电网络分析仪测量温度20~100℃,频率0.3~3GHz下扇贝柱介电常数和介电损耗因数,从而得出扇贝柱在微波加热过程中温度和频率对介电特性的影响。结果表明,温度一定时,介电常数和介电损失因数都是先随着频率增加而降低,随后变化不显著;频率915MHz和2450MHz时,介电常数与温度成负相关,介电损耗因数与温度成正相关。且915MHz和2450MHz下,穿透深度随温度的升高而减小。扇贝柱介电特性的研究为微波杀菌技术的研究提供了理论基础。      

915MHz和2450MHz下扇贝柱介电特性的研究

利用介电网络分析仪测量温度20~100℃,频率0.3~3GHz下扇贝柱介电常数和介电损耗因数,从而得出扇贝柱在微波加热过程中温度和频率对介电特性的影响。结果表明,温度一定时,介电常数和介电损失因数都是先随着频率增加而降低,随后变化不显著;频率915MHz和2450MHz时,介电常数与温度成负相关,介电损耗因数与温度成正相关。且915MHz和2450MHz下,穿透深度随温度的升高而减小。扇贝柱介电特性的研究为微波杀菌技术的研究提供了理论基础。     

全脂乳粉生产过程中HACCP的建立与实施

介绍了全脂乳粉生产HACCP体系的建立过程,对生产工艺进行了危害分析,确定了关键控制点及其关键限值并建立了监控措施和纠偏措施。     

脱脂乳粉为壁材通过喷雾干燥法制备微胶囊的技术研究

采用脱脂乳粉为壁材,色拉油为芯材,通过正交实验,根据芯材的滞留率确定微胶囊化的最佳工艺条件。实验结果表明:采用脱脂乳粉、色拉油、2%吐温-20乳化剂水溶液和水的质量比为40:10:10:90,在8000r/min条件下乳化15min,之后在进风温度为140±2℃、出风温度为80±2℃条件下喷雾干燥,色拉油滞留率接近60%。可见,此种方法制作的微胶囊包埋效果较好。      

营养强化剂对脱脂乳粉中甲醛产生的影响

目的 研究不同营养强化剂对脱脂乳粉中甲醛生成的影响.方法 脱脂乳粉添加5％有效含量的单一营养强化剂,经热处理后测定甲醛含量,进行单因素实验,考察不同营养强化剂对甲醛产生的影响,选择作用显著的营养强化剂进行双因素组合实验,研究不同营养强化剂之间的相互作用.结果 110℃热处理10 min的情况下,单因素实验结果表明,维生...     

以全脂淡乳粉为主要原料进行新型肠道营养粉的研究

肠道营养对一些患者,尤其肠道疾病患者疾病治疗、身体康复有很大的作用,是治疗方案中不可缺少的一部分,因此,人们都在研究营养要素膳的组成和作用。本研究根据市场需求,对比以往营养要素膳,研究开发出一种营养素配比适当、蛋白质模式近于人体需要、脂肪符合人体需求、无机盐和维生素全面,而且口感好、易溶解、价格适宜的新型肠道营养粉。本研究是以全脂乳粉为主要原料,添加了必需的营养物质,采用了先进的研发工艺。     

脱盐乳清粉及脱脂乳粉理化指标的跟踪检测

通过比较法国及芬兰生产的脱盐乳清粉在粒径、密度、灰分、水分、蛋白、维生素B1、维生素B2、泛酸等10项理化指标上的差异,发现法国生产的脱盐乳清粉在维生素指标上优于芬兰生产的脱盐乳清粉。然后又测定了法国某公司生产的不同批次脱盐乳清粉的理化指标,由单因素方差分析发现不同生产批次或某些批次间在5％的水平上存在显著性差异．并由统计学分析初步得出其理化指标的规格。本研究同时对美国及法国脱脂乳粉的理化指标进行了跟踪检测,经比较发现5％的显著水平上,二者理化指标差异不大。     

羊全脂乳粉对小鼠肠道菌群的影响

中医书籍中有多处羊乳有益肠道健康的记载,这可能与羊乳能够影响肠道菌群有关。为研究羊全脂乳粉对小鼠肠道菌群的影响,本研究收集饲喂羊全脂乳粉小鼠的盲肠内容物,采用CTAB法提取肠道菌群总DNA,经PCR扩增16s rDNA V4区后,用Illumina高通量测序技术测定小鼠肠道中菌群的分布和丰度状况,并重点分析小鼠肠道中乳杆菌属、双歧杆菌属、拟杆菌属、梭菌属的分布,并结合小鼠血液生化指标分析来研究羊全脂乳粉对小鼠肠道菌群和生理生化指标的影响。     

脱脂乳粉非酶褐变影响因素的实验研究

在食品、饮料、营养品、医药等行业广泛涉及非晶态粉体产品,这些粉体产品的非酶褐变,会严重影响产品质量。本文对脱脂乳粉的非酶褐变特性进行了实验研究;考查了水分活度、贮藏温度、储藏时间和玻璃化转变温度等参数对脱脂乳粉非酶褐变的影响。结果表明:随着水分活度、贮藏温度、贮藏时间以及贮藏温度T与脱脂乳粉的玻璃化转变温度Tg间的差值(T-Tg)的增加,脱脂乳粉非酶褐变指数显著增大;脱脂乳粉应在较低水分活度(例如0.3以下)和较低温度(例如40℃以下)下贮藏,以延长其货架寿命。     

全脂牛乳粉中糖基化酪蛋白分析

研究全脂牛乳粉中糖基化酪蛋白,探讨其酶解特性。重点考察了不同pH、酸及提取方法对酪蛋白提取质量百分数的影响,并通过SDS-PAGE电泳分析酪蛋白,高碘酸—希夫碱染色法及莫氏试验鉴定糖基化酪蛋白,木瓜蛋白酶水解酪蛋白,测定其氨基酸含量。结果表明,pH 4.6时提取酪蛋白的质量百分数显著高于其他组(P0.05);质量百分数为2%的乙酸(pH 3.58)提取酪蛋白的质量百分数为(40.45±0.66)%,显著高于其他组(P0.05);鞣酸提取酪蛋白的质量百分数为(46.13±0.46)%,显著高于其他方法(P0.05);酪蛋白SDS-PAGE电泳结果表明,不同酸、不同方法提取的酪蛋白均有3条带,其分子量均分别为34,24,60ku;高碘酸—希夫碱染色结果表明,分子量为34,24ku的酪蛋白是糖基化酪蛋白;莫氏试验结果表明,乳粉酪蛋白中存在糖基化酪蛋白;酶解结果表明,乳粉酪蛋白经木瓜蛋白酶水解后游离氨基酸含量显著高于鲜乳酪蛋白(P0.05)。说明全脂牛乳粉中有糖基化酪蛋白,其分子量分别为34,24ku,易于水解。     

奶粉加速破坏性实验中质量参数的确定

在35℃和45℃的恒湿贮存条件下，考察了全脂和脱脂奶粉的脂肪氧化以及参与美拉德反应的蛋白质变性情况。全脂奶粉由于脂肪含量高，45℃下的硫代巴比妥酸反应物(TBARS)在10d以后便开始递增，明显早于30d才变化的反映美拉德反应的荧光强度，说明首先导致全脂奶粉品质变化的原因是脂肪氧化。在35℃和45℃下。脱脂奶粉荧光强度的增加都先于全脂奶粉，并且增加的幅度都很大，通过运用SDS-PAGE对蛋白质结构进行分析对照，荧光强度可以实时反映蛋白质的变性程度。     

Influence of skimmed milk concentrate replacement by dry dairy products in a low fat set‐type yoghurt model system. I: Use of whey protein concentrates,milk protein concentrates and skimmed milk powder

Ten commercial samples of dry dairy products used for protein fortification in a low fat yoghurt model system at industrial scale were studied. The products employed were whey protein concentratres, milk protein concentrates, skimmed milk concentrates and skimmed milk powder which originated from different countries. The gross chemical composition of these dried products were determined, including polyacrylamide gel electrophoresis (SDS‐PAGE) and isoelectric focusing of the proteins, and minerals such as Na, Ca, K and Mg. Yoghurts were formulated using a skim milk concentrated as a milk base enriched with different dry dairy products up to a 43 g kg⁻¹ protein content. Replacement percentage of skim milk concentrated by dry dairy products in the mix was between 1.49 and 3.77%. Yoghurts enriched with milk protein concentrates did not show significantly different viscosity (35.12 Pa s) and syneresis index (591.4 g kg⁻¹) than the two control yoghurts obtained only from skimmed milk concentrates (35.6 Pa s and 565.7 g kg⁻¹) and skimmed milk powder (32.77 Pa s and 551.5 g kg⁻¹), respectively. Yoghurt fortified with the whey protein concentrates, however, was less firm (22.59 Pa s) and had less syneresis index (216 g kg⁻¹) than control yoghurts. Therefore, whey protein concentrates may be useful for drinking yoghurt production. © 1999 Society of Chemical Industry     

Characterisation of pressure‐treated skimmed milk powder dispersions: application of NMR spectroscopy

Skimmed milk powder (SMP) (bovine) and skimmed milk powder/sucrose dispersions before, during and after high‐pressure treatment have been studied by nuclear magnetic resonance (NMR) spectroscopy (principally P‐31). The P‐31 spectra of samples at 293 K before and after pressure (400–600 MPa) treatment were not significantly different from one another, whether or not sucrose was present. This indicates that physicochemical changes relating to phosphorus‐containing components occurring during a pressure cycle are either reversible or result in re‐immobilisation, while protein components may be rearranged. The P‐31 NMR spectra of these dispersions at 293 K under pressure (100–300 MPa) showed that pressure caused a considerable increase in the free inorganic phosphate concentration and that the increase was proportional to the magnitude of pressure. Decompression to ambient caused an exact reversal of this trend. These findings are discussed in terms of characterisation and properties of pressure‐treated SMP dispersions by other methods and techniques. © 2002 Society of Chemical Industry     

中性及酸性条件下不同来源脱脂乳粉的稳定性比较分析

目的对5种不同来源的脱脂乳粉在中性和酸性条件下的稳定性进行比较分析。方法对不同脱脂乳粉的营养组成、乳清蛋白氮、热凝固时间、△p H、离心沉淀率等指标进行检测并进行对比。结果 5种脱脂乳粉在蛋白质、乳糖、钙等影响稳定性的成分上差异不大,脱脂乳粉热凝固时间越长、△p H越小,酸性乳饮料经高温热处理后离心沉淀越少,而脱脂乳粉乳清蛋白氮越高,中性条件下离心沉淀越少。结论本研究对脱脂乳粉在中性和酸性条件下的稳定性评价较为科学,对于乳清蛋白氮、热凝固时间和△p H的测定可应用于产品中脱脂乳粉的选择。     

贮藏温度对全脂羊奶粉品质稳定性的影响

本文主要研究了贮藏温度(5、25和35℃)对全脂羊奶粉品质稳定性的影响。通过测定全脂羊奶粉的酸值(AV)、过氧化值(POV值)、硫代巴比妥酸值(TBA值)、溶解度、色值等指标反应贮藏期间品质的变化。结果表明,贮藏在35℃的全脂羊奶粉贮藏期间酸值、过氧化值、TBA值变化速率较快,分别于第4个月后、第2个月后、第3个月后显著高于贮藏在5℃和25℃的全脂羊奶粉(p<0.05);所有样品的溶解度和色值变化规律相似,但差异不显著(p>0.05)。因此降低贮藏温度可提高全脂羊奶粉品质稳定性。      

Physicochemical properties of whole milk powder derived from cows fed pasture or total mixed ration diets

This study examined the effect of dietary factors on compositional and functional properties of whole milk powder (WMP) produced from bovine milk. Raw milk samples were obtained from 3 groups of 18 Holstein Friesian spring-calving cows randomly assigned to diets based on perennial ryegrass (GRS), perennial ryegrass/white clover sward (CLV), and total mixed ration (TMR). Raw milks obtained in late lactation were subsequently standardized for fat, heat-treated (90°C for 30 s), evaporated, and homogenized before spray drying. The WMP produced from each diet were analyzed to determine differences in color, particle size distribution, heat coagulation time, yogurt gelation, texture profile, and protein profile due to each diet. Significant differences in heat coagulation time were observed between the CLV and TMR samples, whereas color values were significantly different between GRS and TMR samples. No significant differences in gross composition, protein profile, or whey protein nitrogen index were found between the 3 WMP samples. Average D₉₀ values (the particle size at which 90% of the particles were smaller than the specified size) for fat globules were significantly lower in the TMR sample compared with the GRS and CLV samples. Yogurts produced from GRS- and CLV-derived WMP had significantly higher elastic moduli (G′) than those produced from TMR-derived WMP. Similarly, texture profile analysis revealed significantly higher firmness values in yogurt samples derived from CLV compared with TMR samples. Our data characterize the effect of these diets on the composition and functional properties of fat-standardized WMP, suggesting better yogurt functionality and thermal stability in WMP derived from pasture-based bovine diets.     

Selective fractionation of cholesterol from whole milk powder: optimisation of supercritical process conditions

Supercritical fluid extraction (SCFE) of cholesterol from whole milk powder (WMP) was investigated in this study. The combined effects of temperature (40–80 °C) and pressure (150–250 bar) on the efficacy of cholesterol extraction (mg 100 g^?1), modifications in the fat content (FC) (%) and solubility index (SI) (%) of WMP were studied and optimised by the application of response surface methodology (RSM). Variations in the free fatty acids (FFAs) (mg oleic acid per 100 g of milk fat) and lightness value (L*) were also investigated after SCFE process. About 55.8% reduction in cholesterol was achieved at the optimised condition of 68 °C, 207 bar with 40 min static time and 2 h dynamic time at flow rate of 6 L min^?1. Extraction at the optimised conditions maximised the yield of cholesterol while retaining the FC, SI, FFA and L* at moderate limits of 23.7%, 85.1%, 7.7 mg per 100 g milk fat and 95.4, respectively.     

嗜热链球菌在脱脂乳中发酵特性的研究

本文主要探讨了5株不同嗜热链球菌菌株(ST、ST1、ST5、ST7、ST9)在脱脂乳中发酵8 h和24 h的产酸和产粘情况的对比,并从中选出两株相差较大的菌株ST5和ST9,研究其在发酵过程中的p H、滴定酸度、氨基酸态氮和粘度的变化规律。5株嗜热链球菌中,产酸能力大小顺序为:ST5>ST,ST7>ST1>ST9,产粘能力大小顺序为:ST5>ST7>ST>ST1>ST9。其中,ST5发酵乳的酸度和粘度最大,ST9则相反。对两种菌株进一步研究中发现,在不同的发酵时间,ST5的产酸能力和产粘能力均较强,其对应的发酵乳还原糖和总糖含量较低,且二者发酵乳的粘度变化均呈抛物线型,但是ST9菌株对蛋白质的降解能力大于ST5。研究发现,不同嗜热链球菌菌株在脱脂乳中的发酵特性具有差异性,且随发酵时间的增加而变化。