Effects of Co-spray Drying of Surfactants with High Solids Milk on Milk Powder Wettability

Dairy industries often spray lecithin, a food-grade surfactant, to spray-dried whole milk powders while fluidisation to produce instant powders. Though adding surfactant to milk feed was often reported to improve the wettability of dried powders, this approach was not favourably used. The present study investigated the effects of surfactant addition into high solids milk feed before drying on the wettability of whole milk particles. Adding either 0.1 wt.% Tween 80 or 0.1 wt.% lecithin to un-concentrated whole milk led to a significant wettability improvement of spray-dried powders. At higher feed solids levels of 23 and 33 wt.%, the wetting process of pure milk powders was comparatively rapid, but the surfactant-added powders showed similar wettability to the pure milk powders. The development of powder wettability as drying progressed was investigated using single droplet-drying technique for 32 and 43 wt.% whole milk in the presence and absence with surfactants. The technique captured an advanced shell formation during drying of higher solids milk. The wettability of surface shells formed by surfactant-added milk was similar to those formed by pure milk throughout drying, from initial shell formation to final drying stage. By contrast, coating surfactants on the outer layer of particles being dried could substantially improve wettability. The rapid shell formation and the slow material diffusion owing to the high medium viscosity were considered the main factors limiting the migration of surfactant molecules towards droplet surface during drying.     

Effects of ionic and nonionic surfactants on milk shell wettability during co-spray-drying of whole milk particles

Mixing surfactants with whole milk feed before spray drying could be a commercially favorable approach to produce instant whole milk powders in a single step. Pure whole milk powders obtained directly from spray drying often have a high surface fat coverage (up to 98%), rendering them less stable during storage and less wettable upon reconstitution. Dairy industries often coat these powders with lecithin, a food-grade surfactant, in a secondary fluidized-bed drying stage to produce instant powders. This study investigated the changes in wetting behavior on the surface of a whole milk particle caused by the addition of surfactants before drying. Fresh whole milk was mixed with 0.1% (wt/wt) Tween 80 or 1% (wt/wt) lecithin (total solids), and the wetting behavior of the shell formed by each sample was captured using a single-droplet drying device at intermediate drying stages as the shell was forming. The addition of surfactants improved shell wettability from the beginning of shell formation, producing more wettable milk particles after drying. The increase in surfactant loading by 10 times reduced the wetting time from around 30 s to <5 s. At the same loading of 1% (wt/wt; total solids), milk particles with Tween 80 were much more wettable than those with lecithin (<5 s compared with >30 s). We proposed that Tween 80 could adsorb at the oil–water interface of fat globules, making the surface fat more wettable, whereas lecithin tends to combine with milk proteins to form a complex, which then competes for the air–water surface with fat globules. Spray-drying experiments confirmed the greatly improved wettability of whole milk powders by the addition of either 0.1% (wt/wt) Tween 80 or 1% (wt/wt) lecithin; wetting time was reduced from 35 ± 4 s to <15 s. To the best of our knowledge, this is the first time that a dynamic droplet drying system has been used to elucidate the complex interactions between ionic or nonionic surfactants and milk components (both proteins and fat), as well as the resultant effect on the development of milk particle functionality during drying.     

Dairy powder rehydration: influence of protein state, incorporation mode, and agglomeration

A simplified method to study rehydration was used on different dairy powders. The method involved dispersing powder in a stirred vessel equipped with a turbidity sensor. The changes of turbidity occurring during powder rehydration highlighted the rehydration stage, and the influence of the proteins’ state on rehydration was clarified. Casein powders had a quick wetting time but very slow dispersion, making the total rehydration process time-consuming. On the other hand, whey powders were found to have poor wettability but demonstrated immediate dispersion after wetting. Mixing casein (80%) and whey (20%) before spray drying greatly improved rehydration time compared with casein powder; whereas mixing whey powder with casein powder at the same ratio after spray drying caused a dramatic deterioration in the rehydration properties. Moreover, agglomeration was found to significantly improve the rehydration time of whey protein powder and to slow down the rehydration time of casein powder. These opposite effects were related to the rate-controlling stage (i.e., wetting stage for whey protein and dispersion stage for casein).     

The influence of milk powder characteristics on the properties of halloumi cheese made from recombined milk*

The properties of halloumi made from recombined milks that had been prepared using milk powders processed by different methods were investigated. With skim milk powder, decreases in heat treatment of the liquid skim before drying were found to improve the stretch and melt properties of the cheese. In contrast, the level of solids in the skim concentrate before drying had no effect on the cheese characteristics. Ultrafiltration was also used to concentrate milk for spray drying. The resultant powder was recombined to give protein levels equivalent to that of normal milk and to that of milk concentrated fivefold. In both cases the recombined milks could be converted into high quality halloumi.     

正交试验优化喷雾干燥法制备玛咖精粉工艺

以玛咖块根为原料,经过醇提、浓缩后采用喷雾干燥法制备玛咖精粉,对进料液固形物质量分数、进风温度和热风流速3 个因素进行单因素和正交试验分析,结果表明：进料液固形物质量分数5%、进风温度120 ℃和热风流速0.4 m3/min时制得的玛咖精粉质量最佳,此时玛咖精粉水分含量为21.2 mg/g（含水率2.12%）,生物碱含量为15.87 mg/g,水溶性蛋白质含量为1.64 mg/g,VC含量为6.03 mg/g,总糖含量为554.50 mg/g。对优化条件下得到的玛咖精粉超微结构、吸湿性的实验研究表明,优化后的喷雾干燥工艺使得玛咖中的有效成分得以保留,所制备的玛咖精粉可作为玛咖深加工产品的优良原料。     

Effect of diacetyl on the heat stability of concentrated milks

Very low levels of diacetyl (1–5 mM) markedly increased the heat stability of concentrated milks (20% total solids) reconstituted from skim milk powders. Diacetyl caused only slight stabilization of the concentrates (following dilution to 20% total solids) used in the manufacture of these powders but its efficacy was increased by heating the concentrates (70°C for 10 min) prior to diacetyl addition and especially by freeze drying. Laboratory concentrated milks were destabilized by diacetyl and these samples were also destabilized by freeze drying. However, addition of diacetyl prior to preheating and concentration increased stability.     

Water vapour adsorption properties of agglomerated baby food powders

This paper presents an analysis of the physical properties of materials in powder and agglomerate form and their sorption characteristics on the basis of the shape of the water vapour adsorption isotherms and kinetics. The observed changes that led to a decrease in the vapour adsorption ability of the investigated powdered baby foods depended mainly on their milk powder content and to a lesser extent on the structure of the powders. This was related to the process of agglomeration and the type of wetting liquid used in that process. Wet agglomeration of the baby food powders investigated in this study influenced growth of particle size and increased wettability regardless of the type of wetting liquid used and the components of the powders. The agglomerates obtained using 2% lecithin solution or 50% sugar solution as the wetting liquids presented a decrease in their rate of water adsorption compared to the agglomerates obtained using water.     

微胶囊分子包埋协同喷雾干燥生产山西老陈醋粉工艺优化

以山西老陈醋为原料,与浓缩山楂汁、沙棘汁混合成配料液杀菌,添加β-环状糊精对配料液进行微胶囊分子包埋,加入麦芽糊精作为干燥助剂,与丁香粉和肉桂粉以及酵母提取物进行复配,喷雾干燥后收集醋粉进行包装。分别以总酸、醋粉得率和水分含量为考察指标,通过试验得出生产山西老陈醋粉的工艺参数为浓缩山楂汁添加量12.5%,浓缩沙棘汁添加量6.5%,酵母提取物添加量0.75%,β-环状糊精添加量20%,麦芽糊精添加量30%,可溶性固形物含量36 °Bx,进料速率100 kg/h,进风温度160 ℃。在此条件下得到的山西老陈醋粉水分含量为6.74%,总酸为6.61 g/100 mL,醋粉得率为36.7%。     

牛、羊乳粉的DSC热学性质比较及掺假分析

为明确羊乳粉、牛乳粉的热学特征,采用差示扫描量热法（differential scanning calorimetry,DSC）对真空冷冻干燥制备的全脂羊、牛乳粉样品以及高比例掺假（75%、50%、25%）和低比例掺假（10%、5%、3%、1%）牛乳粉的混合羊乳粉样品进行热力学分析。结果表明,全脂羊乳粉和全脂牛乳粉在DSC热学指标上存在差异,全脂牛乳粉相比全脂羊乳粉缺失一个脂肪特征熔融吸热峰b,蛋白质熔融吸热峰c峰值温度和热焓值较低,而乳糖熔化分解峰e热焓值较高。对于掺入不同比例牛乳粉的羊乳粉,通过检测是否存在吸热峰b及其热焓值,可判断样品掺假牛乳粉比例是否在25%以下及判断掺入牛乳粉的量;在不同比例掺假样品中检测乳糖熔化分解峰e的焓值可判断羊乳粉掺入牛乳粉的掺假量。因此,DSC技术可以实现对羊乳粉、牛乳粉热学性质的分析和评价,也可作为乳制品行业质量保证和真实性鉴别的潜在分析工具。     

Changes in the physical properties,solubility, and heat stability of milk protein concentrates prepared from partially acidified milk

A limiting factor in using milk protein concentrates (MPC) as a high-quality protein source for different food applications is their poor reconstitutability. Solubilization of colloidal calcium phosphate (CCP) from casein micelles during membrane filtration (e.g., through acidification) may affect the structural organization of these protein particles and consequently the rehydration and functional properties of the resulting MPC powder. The main objective of this study was to investigate the effects of acidification of milk by glucono-δ-lactone (GDL) before ultrafiltration (UF) on the composition, physical properties, solubility, and thermal stability (after reconstitution) of MPC powders. The MPC samples were manufactured in duplicate, either by UF (65% protein, MPC65) or by UF followed by diafiltration (80% protein, MPC80), using pasteurized skim milk, at either the native milk pH (~pH 6.6) or at pH 6.0 after addition of GDL, followed by spray drying. Samples of different treatments were reconstituted at 5% (wt/wt) protein to compare their solubility and thermal stability. Powders were tested in duplicate for basic composition, calcium content, reconstitutability, particle size, particle density, and microstructure. Acidification of milk did not have any significant effect on the proximate composition, particle size, particle density, or surface morphology of the MPC powders; however, the total calcium content of MPC80 decreased significantly with acidification (from 1.84 ± 0.03 to 1.59 ± 0.03 g/100 g of powder). Calcium-depleted MPC80 powders were also more soluble than the control powders. Diafiltered dispersions were significantly less heat stable (at 120°C) than UF samples when dissolved at 5% solids. The present work contributes to a better understanding of the differences in MPC commonly observed during processing.     

Behaviour of homogenized fat globules during the spray drying of whole milk

The changes in milk fat globule size and fat globule surface proteins of both low-preheated and high-preheated concentrated milks, which were homogenized at low or high pressure prior to spray drying using a disc atomization drier, were examined. The average fat globule size (d₃₂) of the spray-dried milk powders was smaller than that of the corresponding concentrates, but a small proportion of very large globules (4–80 μm) was also formed during spray drying. As a consequence, total surface protein (mg protein g⁻¹ fat) increased due to the adsorption of casein micelles at the fat globule surface during spray drying. Confocal micrographs of the powders showed some apparent spreading of the fat on the surface of the powder particles, particularly when the concentrates were homogenized at low pressure. These results indicate disruption of the milk fat globules during spray drying, which consequently causes changes in the fat globule surface protein layer.     

In-situ lecithination of dairy powders in spray-drying for confectionery applications

Powders are essential ingredients of chocolate. In particular for milk chocolate milk and whey powders are important, together with sucrose, lactose and cocoa solids. During processing to maintain a good flow of the molten chocolate mass, particles with hydrophilic surfaces, such as dairy powders and sugars, are coated with a surface-active compound. Only lecithin and polyglycerol polyricinoleate (PGPR) (at a limited level) are allowed in chocolate, and as these are expensive as little as possible is added, whilst maintaining rheological properties. Conventionally, lecithin is added during conching, and through the intense kneading of the chocolate mass it is distributed throughout the mass. Usually about 0.5% is added, although the level depends upon the composition of the chocolate. Here we present a new approach to lecithination of spray-dried milk and lactose powders, which we call in-situ lecithination. It has been found that the surface of a spray-dried powder is dominated by any surface-active species, and in a competitive situation, the most rapidly adsorbing species dominates. This behaviour is utilised when lecithin is added to the spray-dryer feed, and through the competitive adsorption of surface-active agents during the drying process, it dominates the powder surface composition as measured by X-ray photoelectron spectroscopy (XPS). This is also seen in differences in sedimentation rate when the powders are mixed with cocoa butter to assess the rheological properties of the powder dispersions. The effect was large for lactose powders, but smaller for skim milk powder and whey powder.     

A new technique for spray drying orange juice concentrate

A new technique for spray drying concentrated orange juice using dehumidified air as drying medium and maltodextrin as drying agent was developed. A pilot-scale spray dryer was employed for the spray drying process. The modification made to the original design consisted in connecting the dryer inlet air intake to an absorption air dryer. 21 DE, 12 DE, and 6 DE maltodextrins were used as drying agents. Concentrated orange juice was spray dried at inlet air temperatures of 110, 120, 130, and 140 °C and (concentrated orange juice solids)/(maltodextrin solids) ratios of 4, 2, 1, and 0.25. Data for the residue remaining on the walls were gathered and the powders were analyzed for moisture content, bulk density, rehydration, hygroscopicity, and degree of caking. The combination of maltodextrin addition and use of dehumidified air was proved to be an effective way of reducing residue formation.Industrial relevanceOrange juice powder has many benefits and economic potentials over its liquid counterparts and provides a stable, natural, easily dosable ingredient, which generally finds usage in many foods and pharmaceutical products such as flavoring and coloring agents. However, the dehydration of orange juice is not a simple task. Thus, the objective of this study was to develop a new technique for spray drying orange juice using dehumidified air as drying medium and maltodextrin as drying agent.     

Effect of spray‐drying parameters on the solubility and the bulk density of camel milk powder: A response surface methodology approach

Response surface methodology coupled with a Box–Behnken experimental design was used to investigate the effect of the air inlet drying temperature, the feed rate, and the fat content on the solubility and the bulk density of spray‐dried camel and cow milk powders. The response surface methodology analysis highlighted that milk fat content and feed rate were the most effective parameters affecting the solubility and the bulk density of cow and camel milk powders. Importantly, there was no significant interaction between the studied drying parameters and camel milk powder solubility or bulk density. Overall, camel milk powder exhibited a comparable solubility to that of cow milk powder with a higher bulk density.     

Chemical modifications of casein occurring during industrial manufacturing of milk protein powders

The effect of milk acidification at different pH levels applied during the processing of various types of milk protein powders was first evaluated in the experimental samples of caseins, caseinates and milk protein concentrates. The absence of inorganic colloidal phosphorus was detected when milk was acidified to pH 4.60, whereas low levels (0.36–0.72 g/100 g of protein) were detected when mild milk acidification occurred. The extent of protein glycation and the occurrence of protein cross-linking were assessed in the same samples by measuring their furosine (5.7–427 mg/100 g of protein) and lysinoalanine (0.4–35.2 mg/100 g of protein) levels, respectively. In addition to heat treatments, the contents of these markers strictly depend on the presence of lactose and consequently on the effectiveness of the washing step applied during processing before drying to remove non-protein soluble components. The determination of these chemical markers in the samples permitted the identification of different technological conditions applied in the manufacturing of commercial milk protein powders with the same class.     

陕西生鲜羊奶及其加工羊奶粉品质调研分析及相关性研究

为调查陕西省生鲜羊奶及羊奶粉品质随月份的变化规律,明确生鲜羊奶和羊奶粉品质之间的相关关系,该研究以2020年4月至11月某乳品企业在陕西不同地区的奶站收购的生鲜羊奶及其加工羊奶粉为试验样品,对其感官、理化和安全指标进行分析.结果表明,生鲜羊奶和羊奶粉在感官指标方面均符合国家标准要求;在理化指标方面,生鲜羊奶脂肪含量为3...     

Effects of spray drying on antioxidant capacity and anthocyanidin content of blueberry by-products

The effect of spray drying on degradation of nutraceutical components in cull blueberry extract was investigated. Samples collected before and after spray drying were tested for antioxidant capacity using oxygen radical absorbance capacity (ORAC(FL) ) and total phenolics; and for individual anthocyanidins. In Study 1, four different levels of maltodextrin (blueberry solids to maltodextrin ratios of 5: 95, 10: 90, 30: 70, and 50: 50) were spray dried a pilot-scale spray dryer. There was significantly higher retention of nutraceutical components with increased levels of maltodextrin indicating a protective effect of maltodextrin on the nutraceutical components during spray drying. In Study 2, the air inlet temperature of the spray dryer was kept constant for all runs at 150 °C, with 2 different outlet temperatures of 80 and 90 °C. The degradation of nutraceutical components was not significantly different at the 2 selected outlet temperatures. ORAC(FL) reduction for blueberry samples after spray drying was 66.3% to 69.6%. After spray drying, total phenolics reduction for blueberry was 8.2% to 17.5%. Individual anthocyanidin reduction for blueberry was 50% to 70%. The experimental spray dried powders compared favorably to commercial blueberry powders. Results of the study show that use of blueberry by-products is feasible to make a value-added powder. PRACTICAL APPLICATION: Results can be used by producers to estimate final nutraceutical content of spray-dried blueberry by-products.     

Effects of ultrafiltration of whole milk on some properties of spray-dried milk powders

The objective was to produce spray-dried milk powders for assessment subsequently in chocolate. Milks were ultrafiltered to increase their protein content (3.08–5.33 g 100 g⁻¹), concentrated to different solids levels (42.8–52.3 g 100 g⁻¹) and spray-dried to produce powders (26–59 g 100 g⁻¹ fat). The relationships between the milk protein content, concentrate viscosity and some powder properties were quantified. The free-fat content of the powders increased linearly to 74 g 100 g⁻¹ fat with milk protein content for 26 and 40 g 100 g⁻¹ fat powders. The particle size and moisture content of the powders increased linearly with concentrate viscosity for 26 g 100 g⁻¹ fat powders. Differences between the control and ultrafiltration-treated milk powders were explained. The free-fat content and the particle size increased with the fat content of the control powders. The vacuole volume of the powders was inversely more related to the free-fat content than to the fat content of the control powders.     

A comparison of reverse osmosis,nanofiltration and ultrafiltration as concentration processes for skim milk prior to drying

Skim milk was concentrated by reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF) and the retentates were spray‐dried. The resulting powders were reconstituted to 25% TS and sterilised to evaluate their heat stability. Reverse osmosis led to maximum retention of calcium, a fall in pH for its retentate and its reconstituted powder. All RO powders produced a weak gel on heating. Some calcium was lost during NF and a greater amount during UF. Their resulting reconstituted powders had a higher pH than those produced by RO. Powders produced by UF showed poor heat stability. Only one powder produced by NF showed good heat stability. This could be improved by addition of stabilisers at appropriate addition rates.     

干燥方式对湿法加工奶茶固体饮料感官和稳定性的影响

为了考察干燥方式对湿法加工奶茶固体饮料感官和稳定性的影响,本实验以喷雾干燥和真空干燥两种方式干燥奶茶固体饮料。结果表明,经过真空干燥的奶茶粉冲泡浮油严重,口感和组织状态显著差于喷雾干燥奶茶粉。真空干燥奶茶粉表面油含量为13.44%,而喷雾干燥仅为0.78%,通过粒径分布和透光率测定,均显示真空干燥奶茶粉稳定性差,喷雾干燥稳定性较佳。在得率方面,喷雾干燥得率59%,真空干燥74%。综合各项结果,喷雾干燥更适合干燥湿法奶茶固体饮料。