Evaluation of test conditions during the measurement of coffee stability of instant whole milk powder

Coffee provides a harsh environment for the reconstitution of milk powder with undissolved powder being manifested as undesirable 'floaters' or 'sinkers'. A coffee test method was adapted to explore the behaviour of a range of industrial samples of coffee stable and coffee unstable instant whole milk powders, under varying pH, temperature and water hardness. The development and application of a simulation test suggests evidence of some stabilizing contribution by the coffee itself. High surface fat coverage, as determined by electron spectroscopy for chemical analysis, and high ionic calcium levels were associated with instances of poor coffee stability. The effects of the physicochemical characteristics of the powders on coffee stability appear to predominate when various measures were implemented, such as prior reconstitution of the powder before addition to coffee, increased agitation and use of surface active agents, which succeeded in reducing coffee sediment.     

纯乳成分全脂速溶乳粉及其制备方法

采用乳成分制品制备喷涂物料,生产分散度８５％以上的全脂乳粉,称之为“纯乳成分全脂速溶乳粉”;其制备方法又可适用于各种配制乳粉,强化乳粉,豆乳粉及其他速溶饮品,配套设备“三分流组合式离心喷雾器”,可在乳粉喷雾干燥过程中,塔内直接进行颗粒附聚和喷涂,起到与流化床相同作用。     

Slowly dissolving particles in instant whole milk powder – Characterisation and quantitative analysis

Instant milk powders are graded after manufacture using functional tests that gauge the performance of the powder in a way that is relevant to consumer usage, but limited with respect to optimisation of the manufacturing plant. One such test is the slowly dissolving particle test that assesses undissolved particulate material adhering to a glass surface after reconstitution. This particulate material can be comprised of two subclasses ‒ bulk particles and surface particles ‒ which have different origins, natures and compositions and require different approaches for their measurement. However, a combination of an image analysis technique developed to quantify bulk particles and a gravimetric approach to assess the surface particle mass, enables more objective powder grading and better understanding of the source of solubility issues that may arise. Plant operators can use the result to make more specific adjustments to optimise plant performance.     

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。      

Effect of preheating and other process parameters on whey protein reactions during skim milk powder manufacture

Skim milk powder was manufactured in a milk powder plant using different preheating temperatures, concentrate heating temperatures and spray drying temperatures. Varying the preheating conditions from 70 °C for 52 s to 120 °C for 52 s had a marked effect on the denaturation of $\beta$-lactoglobulin A, $\beta$-lactoglobulin B, $\alpha$-lactalbumin, bovine serum albumin (BSA), and immunoglobulin G. In contrast, varying concentrate heating temperature (65–74 °C) and inlet/outlet air dryer temperature (200/101 °C–160/89 °C) had a minimal effect on whey protein denaturation. Most of the whey protein denaturation and association with the casein micelle occurred in the preheating section of the powder plant. Aggregation of β-lactoglobulin (β-lg) and BSA predominantly involved disulphide bonds. Although, greater than 90% of the β-lg and BSA was denatured after preheating at 120 °C for 52 s, the extent of association with the casein micelle was lower, 50% for β-lg and 75% for BSA.     

An alternative process for the manufacture of whole milk powder

The traditional process of manufacturing whole milk powder has some negative aspects: high heat treatment of the milk and, owing to fouling during evaporation, loss of product. To reduce these negative aspects an alternative way of producing whole milk powder was investigated in pilot-plant experiments. Milk was first separated into skim milk and cream and then treated further. Skim milk was subjected to a low heat treatment and concentrated by evaporation. The cream was subjected to a high heat treatment and mixed with the concentrated skim milk. The standardized whole milk concentrate was then spray dried. This process of manufacturing whole milk powder compared favourably with the traditional process with respect to product losses, the physical properties of the whole milk powder and the flavour of the reconstituted milk.     

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。     

The effect of free Ca2+ on the heat stability and other characteristics of low-heat skim milk powder

Low-heat skim milk powder (SMP), reconstituted to 25% total solids, was found to have poor heat stability. This could be improved by reducing the free Ca²⁺ concentration to 1.14 mm, or lower, by the addition of either Amberlite IR-120 ion-exchange resin in its sodium form or tri-sodium citrate in skim milk prior to evaporation and spray drying. Reduction in Ca²⁺ concentration was accompanied by increases in pH, particle size, and kinematic viscosity, and by a reduction in ζ-potential and changes in colour. In-container sterilisation of the reconstituted powder increased particle size, ζ-potential, kinematic viscosity and a* and b* values. However, Ca²⁺ concentration, pH and whiteness decreased. This study elucidated the importance of Ca²⁺ concentration and pH on heat stability of low-heat SMP, suggesting that Ca²⁺ concentration and pH in bulk milk are useful indicators for ensuring that spray dried milk powder has good heat stability.     

咖啡奶稳定性的研究

研究了咖啡奶的稳定性，主要对不同的乳化剂和稳定剂的效果进行了研究。由单因素实验，择优选出对于咖啡奶稳定性较好的添加剂。应用SAS软件进行正交设计，选择最佳的复配稳定剂，确定了提高稳定性的最佳添加剂配方。研究结果表明，对于咖啡乳饮料的稳定性而言，使用复配稳定剂的效果要明显好于使用单一的添加剂复配稳定荆的配方为：单甘醣0．2％、MCC徽晶纤维素0．2％。     

乳粉中的玻璃化相变及对乳粉品质的影响

在无定形聚合物玻璃化相变理论的基础上,介绍了乳粉中乳糖的玻璃相变及测定方法,讨论了玻璃化相变的影响因素以及对乳粉品质的影响。     

乳粉中的玻璃化相变及对乳粉品质的影响

在无定形聚合物玻璃化相变理论的基础上 ,介绍了乳粉中乳糖的玻璃化相变及测定方法 ,讨论了玻璃化相变的影响因素以及对乳粉品质的影响     

The determination of milk powder added to whole milk

The objective was to determine the adulteration of fresh milk with reconstituted full fat milk powder. The ultra violet and visible spectra (700 to 240 nm) indicated two empirical parameters which are used to detect and quantify adulteration. Each parameter was calibrated against standards of adulteration and then tested against samples of known adulteration. One parameter, tested against two known series (5, 10, 20, 40 and 80% adulteration) gave the best correlation (coefficient of variation, 2.9%) between 20 and 60% adulteration. Correlation decreased at 80% adulteration (coefficient of variation 6.7%) and at 0 to 20% adulteration (coefficient of variation 35.9%). The second parameter, used in the range of 0 to 10% adulteration, when tested against 14 known samples gave results with an average of 12.5% below the true values. Sensitivity was 2.5% added reconstituted milk powder. The effect of low fat values (less than 2.3%) is discussed and a correction factor derived. The method when tested against 12 known samples gave the correct result in all cases within the limitations of the method; 4 commercial samples of milk were also analyzed.     

牛奶咖啡饮料的稳定性研究

牛奶咖啡饮料是以咖啡提取液或速溶咖啡粉为主要原料,加入乳粉、白砂糖、稳定剂及其他辅料并经过有效杀菌后制作成的一种中性含乳咖啡饮料,其在货架期内很容易产生脂肪上浮、蛋白絮凝和沉淀,严重影响产品品质。因此,需要筛选添加合适的稳定剂来保证产品的稳定性。本实验利用快速稳定性分析仪LUMiFuge结合目测观察法、粒径分析法、离心沉淀率测定的方法,研究了磷酸盐、乳化剂和增稠剂对牛奶咖啡体系稳定性的影响,确定了最优的稳定剂种类:磷酸盐选取六偏磷酸钠、乳化剂选取羟基化大豆磷脂、增稠剂选取MCC。     

Influence of high-oryzanol rice bran oil on the oxidative stability of whole milk powder

The effect of high oryzanol rice bran oil (RBO) on the oxidative stability of low-heat and high-heat whole milk powder (WMP) was investigated. Milk (3.6% fat) was fortified with RBO at 0.1 and 0.2% (wt/wt) and was concentrated and dried. Control WMP was made without RBO addition. Thiobarbituric acid reactive substances (TBARS) were used to monitor oxidation during storage at 45 degrees C for 40 d. The oxidation of low-heat WMP was significantly reduced by addition of 0.1% RBO, but there was no significant effect on the oxidation of high-heat WMP. An increase of RBO to 0.2% did not significantly improve the oxidative stability when compared with 0.1% RBO. The TBARS in RBO-fortified, low-heat WMP increased with storage time up to 30 d but decreased with further storage to 40 d. The TBARS in all high-heat WMP and low-heat control WMP increased up to 20 d storage and then decreased with further storage. The most likely reason for this increase was due to the reaction of TBARS with milk proteins. Addition of RBO reduced the L (lightness) value and increased the b (yellowness) value but had no effect on the a (redness) value. When compared with the control milk powder, consumers could not detect any effect on the flavor of the reconstituted 0.1% RBO WMP but could detect a flavor difference in the 0.2% RBO WMP.     

充氮包装对全脂羊奶粉贮藏期间脂肪氧化稳定性的影响

采用加速氧化的方法研究充氮包装对全脂羊奶粉贮藏期间脂肪氧化稳定性的影响。通过测定全脂羊奶粉的酸值、过氧化值、硫代巴比妥酸值(TBA)、色度值等指标评价全脂羊奶粉贮藏期间脂肪的分解氧化状况。结果表明:充氮包装的全脂羊奶粉贮藏期间酸值、TBA值和色度值变化趋势较慢,分别于第6周后、第3周后、第7周后显著低于普通包装的全脂羊奶粉(p<0.05);充氮包装的全脂羊奶粉的过氧化值于第7周达到最高值13.54mmol/kg脂肪,变化速率显著小于普通包装的全脂羊奶粉(p<0.01)。说明充氮包装可延缓酸值、过氧化值、TBA值和色度值的变化速率,显著提高全脂羊奶粉脂肪的氧化稳定性。      

低聚果糖咖啡牛奶的加工工艺与稳定性研究

采用单因素试验和正交试验确定了以鲜牛奶、咖啡粉、低聚果糖和白砂糖为主要原料进行超高温瞬时灭菌,无菌灌装后生产咖啡牛奶的加工工艺.结果表明,优化的配方为:鲜奶40%,咖啡粉0.4%,低聚果糖4%,白糖4%,酸0.25%;添加CMC-Na0.25%,果胶0.10%,阿拉伯胶0.15%,柠檬酸三钠0.1%,能起到良好的稳定效果.     

水分活度对全脂羊奶粉贮藏期间脂肪稳定性的影响

采用加速氧化的方法研究水分活度对全脂羊奶粉贮藏期间脂肪稳定性的影响.通过测定全脂羊奶粉的酸值、过氧化值、硫代巴比妥酸值(TBA)、颜色等指标评价全脂羊奶粉贮藏期间的氧化状况.结果表明,水分活度为0.32的全脂羊奶粉贮藏期间酸值、TBA值显著高于水分活度为0.11和0.23的全脂羊奶粉(p＜0.05),且水分活度为0.32的全脂羊奶粉过氧化值变化速率较快(p＜0.05),且褐变严重.因此,降低全脂羊奶粉的水分活度可以提高其贮藏稳定性.