Mechanical and Product Design Engineering, Faculty of Science, Engineering and Technology, Swinburne University of Technology, John Street, Hawthorn, VIC 3122, Australia.
Mechanical and Product Design Engineering, Faculty of Science, Engineering and Technology, Swinburne University of Technology, John Street, Hawthorn, VIC 3122, Australia.
Ultrason Sonochem. 2016 Jan;28:118-129. doi: 10.1016/j.ultsonch.2015.06.023. Epub 2015 Jun 27.
The ultrasonic fractionation of milk fat in whole milk to fractions with distinct particle size distributions was demonstrated using a stage-based ultrasound-enhanced gravity separation protocol. Firstly, a single stage ultrasound gravity separation was characterised after various sonication durations (5-20 min) with a mass balance, where defined volume partitions were removed across the height of the separation vessel to determine the fat content and size distribution of fat droplets. Subsequent trials using ultrasound-enhanced gravity separation were carried out in three consecutive stages. Each stage consisted of 5 min sonication, with single and dual transducer configurations at 1 MHz and 2 MHz, followed by aliquot collection for particle size characterisation of the formed layers located at the bottom and top of the vessel. After each sonication stage, gentle removal of the separated fat layer located at the top was performed. Results indicated that ultrasound promoted the formation of a gradient of vertically increasing fat concentration and particle size across the height of the separation vessel, which became more pronounced with extended sonication time. Ultrasound-enhanced fractionation provided fat enriched fractions located at the top of the vessel of up to 13 ± 1% (w/v) with larger globules present in the particle size distributions. In contrast, semi-skim milk fractions located at the bottom of the vessel as low as 1.2 ± 0.01% (w/v) could be produced, containing proportionally smaller sized fat globules. Particle size differentiation was enhanced at higher ultrasound energy input (up to 347 W/L). In particular, dual transducer after three-stage operation at maximum energy input provided highest mean particle size differentiation with up to 0.9 μm reduction in the semi-skim fractions. Higher frequency ultrasound at 2 MHz was more effective in manipulating smaller sized fat globules retained in the later stages of skimming than 1 MHz. While 2 MHz ultrasound removed 59 ± 2% of the fat contained in the initial sample, only 47 ± 2% was removed with 1 MHz after 3 ultrasound-assisted fractionation stages.
全脂牛奶的超声乳脂分级实验，采用基于阶段的超声增强重力分离方案，证明了可以将其分离为具有不同粒径分布的级分。首先，在不同的超声时间（5-20 分钟）后，通过质量平衡对单级超声重力分离进行了表征，其中定义的体积部分在分离容器的高度上被移除，以确定脂肪滴的脂肪含量和粒径分布。随后，在三个连续的阶段中进行了超声增强重力分离的试验。每个阶段包括 5 分钟的超声处理，使用 1 MHz 和 2 MHz 的单和双换能器配置，然后对形成的层进行等分收集，以对位于容器底部和顶部的层进行粒径特征分析。在每个超声处理阶段后，轻轻去除位于顶部的分离脂肪层。结果表明，超声促进了脂肪浓度和粒径沿分离容器高度的垂直增加梯度的形成，随着超声时间的延长，这种梯度变得更加明显。超声增强分级在容器顶部提供了高达 13±1%（w/v）的富含脂肪的级分，粒径分布中存在较大的液滴。相比之下，位于容器底部的低脂级分（低至 1.2±0.01%（w/v）），可以产生更小的脂肪液滴。在更高的超声能量输入下，粒径分化得到增强（最高可达 347 W/L）。特别是，在最大功率输入下进行三级操作后的双换能器提供了最高的平均粒径分化，低脂级分的粒径最多可减少 0.9μm。2 MHz 的高频超声在撇脂后期处理较小尺寸的脂肪球时比 1 MHz 更有效。虽然 2 MHz 超声去除了初始样品中 59±2%的脂肪，但在 3 个超声辅助分级阶段后，仅去除了 1 MHz 的 47±2%。
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