Flavor Variability and Flavor Stability of U.S.-Produced Whole Milk Powder

ABSTRACT:  Flavor variability and stability of U.S.-produced whole milk powder (WMP) are important parameters for maximizing quality and global competitiveness of this commodity. This study characterized flavor and flavor stability of domestic WMP. Freshly produced (<1 mo) WMP was collected from 4 U.S. production facilities 5 times over a 1 y period. Each sample was analyzed initially and every 2 mo for sensory profile, volatiles, color, water activity, and moisture through 12 mo storage. Selected volatiles were quantified using solid phase microextraction (SPME) with gas chromatography/mass-spectrometry: dimethyl sulfide, 2-methylbutanal, 3-methylbutanal, hexanal, 2-heptanone, heptanal, 1-octen-3-ol, octanal, 3-octen-2-one, and nonanal. Multiple linear regression with backwards elimination was applied to generate equations to predict grassy and painty flavors based on selected volatiles. All WMP were between 2% and 3% moisture and 0.11 and 0.25 water activity initially. WMP varied in initial flavor profiles with varying levels of cooked, milk fat, and sweet aromatic flavors. During storage, grassy and painty flavors developed while sweet aromatic flavor intensities decreased ( P  < 0.05). Painty and grassy flavors were confirmed by increased levels ( P  < 0.05) of lipid oxidation products such as hexanal, heptanal, and octanal. Hexanal, 2-heptanone, 1-octen-3-ol, and nonanal concentrations were best predictors of grassy flavor ( R ²= 0.38,  P  < 0.0001) while hexanal, 2-methylbutanal, 3-methylbutanal, octanal, and 3-octen-2-one concentrations were best predictors of painty flavor ( R ²= 0.61,  P  < 0.0001). These results provide baseline information to determine specific factors that can be controlled to optimize U.S. WMP flavor and flavor stability.     

Gelation and Water Binding Properties of Transglutaminase-treated Skim Milk Powder

Transglutaminase (TGase)-treated skim milk powder (TG-SMP) was prepared by freeze-drying skim milk after TGase treatment (10 U/g milk protein, 40°C for 3 h), followed by TGase inactivation at 85°C for 5 min. TGase modification resulted in significant increases in hardness and water holding capacity (WHC) of heat-induced gels (10% protein, w/v). A marked increase in storage modulus (G') of TG-SMP upon heating suggests that TG-SMP has a greater gelling ability than control-SMP (C-SMP) prepared with predenatured TGase. Acid gels prepared from TG-SMP had a significantly higher WHC at all solid levels (12%, 14%, and 16%) tested and formed a more elastic network than C-SMP.     

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。     

辐照对市售奶粉品质影响的研究

目的:分析不同剂量辐照对奶粉营养成分的影响。方法:对市售袋装奶粉进行不同剂量的60Coγ照射,辐照剂量分别为0、5、10、15、20kGy,分析了其中主要营养成分、微生物指标和感官指标的前后变化。结果:与对照组相比,5kGy和10kGy组辐照后主要营养成分和感官性状无明显改变,微生物指标大幅度下降:而15kGy和20kGy组辐照后营养成分有显著性改变,p＜0．05,微生物指标为0,感官性状无明显改变。结论:≤10kGy剂量辐照对奶粉营养素没有明显影响,微生物指标大幅度下降,从而延长了奶粉的保质期,增加了奶粉的食用安全性。     

Enzyme-catalyzed Production of Oligopeptides from Skim Milk

With the aim of preparing high nutritional dietary supplements containing oligopeptides from skim milk, an Aspergillus protease, papain and pepsin, separately or in association, were used in different enzyme:substract ratios (1%, 2% and 4%). The fractionation of peptides according to their size was used to evaluate the nutritional quality of protein hydrolysates. The hydrolysates were fractionated by high-performance liquid chromatography in size-exclusion mode and the rapid method of Correct Fraction Area was used for the quantification. In general, the isolated action of the enzymes produced better peptide profiles than their simultaneous use, especially in terms of a higher amount of oligopeptides, which reached 56%.     

Enzyme-catalyzed Production of Oligopeptides from Skim Milk

With the aim of preparing high nutritional dietary supplements containing oligopeptides from skim milk, an Aspergillus protease, papain and pepsin, separately or in association, were used in different enzyme:substract ratios (1%, 2% and 4%). The fractionation of peptides according to their size was used to evaluate the nutritional quality of protein hydrolysates. The hydrolysates were fractionated by high-performance liquid chromatography in size-exclusion mode and the rapid method of Correct Fraction Area was used for the quantification. In general, the isolated action of the enzymes produced better peptide profiles than their simultaneous use, especially in terms of a higher amount of oligopeptides, which reached 56%.     

酶促奶油水解制备天然奶味香精

选用脂肪酶lipaseAY水解奶油制备天然奶味香精。在奶油与乳清粉的质量比为14:1,脂肪酶量为奶油质量的0.2%,反应温度为45℃时,其香气评分最佳。GC-MS分析结果显示:产物中脂肪酸约占80%,内酯和酯类约为20%。所制备的天然奶味香精具有浓郁的干酪风味,带有淡淡的甜奶香味,香气醇厚,口感细腻。另外,适量添加乳清粉有利于改善产物口感。     

脱脂牛乳体系中乳蛋白葡萄糖美拉德反应程度及产物功能性质研究

以脱脂牛乳为研究对象,以葡萄糖为还原糖,对乳蛋白进行美拉德反应修饰,研究葡萄糖添加量为0~9 g/100 mL脱脂乳时反应体系的糖基化程度、pH、中间产物含量、褐变程度、粒径,以及产物乳化性、发泡性和吸油性。结果显示,脱脂乳体系糖基化程度在葡萄糖添加量为3 g/100 mL时达到最大值,之后迅速降低;中间产物和褐变程度均在该添加量下达到最低值,之后迅速上升。反应体系pH并未随葡萄糖添加量的增加而显著变化。糖基化反应后,酪蛋白胶束粒径增加。糖基化修饰改善了脱脂乳体系的乳化性,当葡萄糖添加量为3 g/100 mL时,乳化活性和乳化稳定性均达到最大值。糖基化修饰后,脱脂乳体系的发泡性并未显著提高,但该体系10和30 min泡沫稳定显著增加(p<0.05)。糖基化修饰后乳蛋白的吸油性降低。研究结论可为脱脂乳体系中乳蛋白美拉德反应产物的应用提供基础数据。     

不同发酵方法对发酵银杏粉营养和风味的影响

为制备一款具有较高营养成分且风味宜人的发酵银杏粉,以泰州大佛指银杏果为原料,研究单酶解(M)、酶解+乳酸菌(M+R)、单乳酸菌(R)、乳酸菌+酵母菌(R+J)、酶解+乳酸菌+酵母菌(M+R+J)5种不同发酵方法对发酵银杏粉的营养成分和挥发性风味物质的影响。营养成分测定结果表明:M+R+J组的黄酮(17.06±0.82) mg/g、多酚(46.62±1.97) mg/g、总抗氧化能力(241.91±10.23) U/mL显著高于其他4组(P<0.05);可溶性蛋白(4.74±0.18) mg/g最高;可溶性糖(7.61±0.91) mg/g显著高于R组(5.24±0.52) mg/g和R+J组(3.82±0.41) mg/g(P<0.05)。挥发性风味成分测定结果表明:M+R+J组检测到的醇类物质(17.44%)、酚类物质(3.95%)、酸味物质(13.46%)、挥发性酯类物质(11.87%)均最高,赋予了产品酸香适宜、浓郁的风味;检测到的风味缺陷物质醛类物质(2.38%)最低;5组中的烃类物质大多数为饱和脂肪烃类,嗅觉阈较高,对产品的风味影响较小。结论:酶解后采用乳酸菌协同酵母菌发酵有利于营养成分的析出和风味物质的富集,明显提高发酵银杏粉的营养价值,并赋予其良好的风味。     

Membrane Fractionation Processes for Removing 90% to 95% of the Lactose and Sodium from Skim Milk and for Preparing Lactose and Sodium‐Reduced Skim Milk

ABSTRACT: Pilot‐scale microfiltration (MF), microfiltration‐diafiltration (MDF), ultrafiltration (UF), ultrafiltration‐diafiltration (UDF), and nanofilration (NF) membrane fractionation processes were designed and evaluated for removing 90% to 95% of the lactose and sodium from skim milk. The study was designed to evaluate several membrane fractionation schemes as a function of: (1) membrane types with and without diafiltration; (2) fractionation process temperatures ranging from 17 to 45 °C; (3) sources of commercial drinking water used as diafiltrant; and (4) final mass concentration ratios (MCR) ranging from about 2 to 5. MF and MDF membranes provided highest flux values, but were unsatisfactory because they failed to retain all of the whey proteins. UDF fractionation processes removed more than 90% to 95% of the lactose and sodium from skim milk. NF permeate prepared from UDF cumulative permeate contained sodium and other mineral concentrations that would make them unsuitable for use as a diafiltrant for UDF applications. A method was devised for preparing simulated milk permeate (SMP) formulated with calcium, magnesium, and potassium hydroxides, and phosphoric and citric acids for use as UDF diafiltrant or for preparing lactose and sodium reduced skim milk (L‐RSM). MF retentates with MCR values of 4.7 to 5.0 exhibited extremely poor frozen storage stabilities of less than 1 wk at ?20 °C, whereas MCR 1.77 to 2.95 MDF and UDF retentates and skim milk control exhibited frozen storage stabilities of more than 16 wk. L‐RSM exhibited a whiter appearance and a lower viscosity than skim milk, lacked natural milk flavor, and exhibited a metallic off‐flavor.     

脱脂奶粉勾兑牛奶酒工艺中pH值的影响

探讨了以脱脂奶粉为原料勾兑奶酒的工艺条件,主要研究了牛奶蛋白在乙醇存在下影响其稳定性的一个重要因素——pH值.实验表明,在以脱脂奶粉为原料勾兑奶酒时,酒精应该先进行适量的稀释再加入到复配奶中;随着复配奶pH值的升高,其牛奶蛋白的乙醇稳定性也随之升高.复配奶的pH值决定着勾兑奶酒的pH值,其最适pH值为6.5～7.3,但是酒精的pH对于勾兑奶酒的pH并没有决定性的影响.实验还研究了勾兑奶酒在储存过程中其体系的pH值的变化.     

超高压处理对脱脂乳感官特性的影响

以新鲜脱脂乳为原料,研究高压处理对脱脂乳感官特性的影响。脱脂乳在室温下经不同压力（0.1～700 MPa）和时间（10～30 min）处理后测定其透光率和平均粒径的变化,利用电子眼、电子鼻、电子舌分别检测色泽、气味以及滋味的变化。结果表明：当压力超过200 MPa时脱脂乳透光率增加,而平均粒径不同程度减小;高压处理导致脱脂乳感官特性的改变,在0.1～700 MPa范围内分别处理10～30 min,脱脂乳的主要色号（3002和3018）随着压力的升高逐渐消失,同时出现一些新的色号（如2183和2200）;在处理10 min后脱脂乳中丙酮相对含量的变化不大,处理20～30 min时整体呈减小趋势;乙醛在700 MPa处理10 min、200 MPa处理20、30 min后消失,且出现2-甲基噻吩和乙醇等气味成分,但整体无明显差异（识别指数均小于80）;在处理20～30 min后脱脂乳酸味、咸味与鲜味整体减弱,甜味和苦味增强。因此,超高压处理对脱脂乳气味的影响不大,但会引起色泽、滋味、透光率与粒径产生变化。     

Effective Thermal Conductivity of Rice Flour and Whole and Skim Milk Powder

ABSTRACT: The effective thermal conductivity for 3 kinds of powdered food (rice flour, whole milk powder, and skim milk powder) was measured at selected moisture contents, temperatures, and bulk densities. The transient heat probe method using twin probes was used for the determination of the effective thermal conductivity. The effects of moisture content, temperature, and bulk density on the effective thermal conductivity of samples were investigated. The observed values were compared with the values calculated from the thermal conductivity of air and powder, using the 3 kinds of structural model for thermal conductivity, that is, the series, parallel, and random heat transfer models. An improved random heat transfer model, in which a correction term was incorporated in the random heat transfer model, with the term written as a function of moisture content and temperature, was developed.     

Singlet Oxygen and Ascorbic Acid Effects on Dimethyl Disulfide and Off-Flavor in Skim Milk Exposed to Light

The light-induced off-flavor and dimethyl disulfide increased as fluorescent light exposure increased from 0,2,4,6, to 8h (p<0.05). Sensory evaluation and identified compounds suggest that dimethyl disulfide was mainly responsible for the light-induced off-flavor in skim milk. Dimethyl disulfide was formed by the singlet oxygen oxidation of methionine in milk. Gas chromatographic analysis and sensory evaluation showed that 200,500, and 1000 ppm ascorbic acid, which is a singlet oxygen quencher, lowered the formation of dimethyl disulfide and off-flavor in skim milk (p<0.05).     

钝顶螺旋藻奶粉的研制

螺旋藻粉经特殊处理所得分散性好,风味清新的螺旋藻液,与鲜牛乳及其他原料混合,可制成具有保健功能的适合各种人群的螺旋藻奶粉。     

GC-MS分析天然奶味香精的致香成分

利用气相色谱-质谱联用技术对两种天然奶味香精中的致香成分进行了分析鉴定,结合计算机质谱图库,确定两种香精中的主要致香成分为内酯类、中短链脂肪酸、酯类、噻唑类等化合物.两种香精的香气不同,各化合物之间的组成及含量不同,但含量最高的都为δ-癸内酯.利用确定的GC-MS条件对无水奶油的酶解物进行了分析,鉴定了贡献较大的脂肪酸组成及微量物质.     

基于线扫描拉曼高光谱系统的奶粉中硫氰酸钠无损检测

搭建一套线扫描拉曼高光谱成像系统,探索针对大面积奶粉样本的硫氰酸钠快速无损检测。首先测量硫氰酸钠产生的拉曼信号在脱脂奶粉层中的穿透情况,然后制备10?种不同硫氰酸钠质量分数的奶粉混合样本并采集拉曼高光谱图像,通过高斯窗平滑法和自适应迭代惩罚最小二乘基线校正方法对拉曼光谱进行预处理。预处理后提取2?068.48?cm－1位移处的单波段图像进行分析,结合二值图像最终获得了样本中硫氰酸钠颗粒的含量以及空间分布。结果显示,在2?068.48?cm－1单波段图像中,感兴趣区域内所有像素点的拉曼强度平均值随着硫氰酸钠含量的增加呈线性增长,其决定系数R2达到了0.991?5。二值图像中,感兴趣区域内所有硫氰酸钠检测点之和呈指数增长趋势。在本实验方法中,单次检测奶粉样本的总面积达到80?mm×80?mm,检测时不接触、不破坏样本,无需借助化学试剂。奶粉混合样本中硫氰酸钠颗粒的检测限可达0.01%。研究结果表明,拉曼高光谱成像系统能够快速、无损且大面积地检测出奶粉中的硫氰酸钠,并且可以直观地展示硫氰酸钠颗粒的具体分布,在实际检测应用中该方法具有巨大潜力。     

Volatile Flavor Compounds of Sweetened Condensed Milk

ABSTRACT: The volatile compounds of sweetened condensed milk (SCM) were investigated to explain their contribution to SCM flavor. Commercially processed SCM was diluted with water and the volatiles were isolated by simultaneous steam distillation-extraction under reduced pressure. Commercial liquid milk was used for comparison. The odor concentrate was analyzed by GC and GC-MS, and then fractionated by silica gel TLC and preparative GC to determine the contributors to SCM flavor. Major volatile compounds were 10 fatty acids, 14 lactones, 10 ketones, 13 hydrocarbons, 8 alcohols, 4 aldehydes, and 8 miscellaneous compounds. δ-Decalactone and δ-dodecalactone were the principal contributors to SCM flavor although the other lactones may contribute as well.     

不同热处理脱脂乳粉对褐色乳酸菌饮料稳定性的影响

比较了不同热处理脱脂乳粉的理化性质,并将其应用于褐色乳酸菌饮料生产,以鲜制脱脂乳为对照,探讨了不同脱脂乳原料以及褐色乳酸菌饮料生产工艺对饮料稳定性的影响.结果表明:不同热处理脱脂乳粉的蛋白质、脂肪、水分含量以及乳酸度均无显著差异(P>0.05);但其乳化性、起泡性及乳清蛋白氮指数存在显著差异(P<0.05),随着乳粉受...