The functionality of milk powder and its relationship to chocolate mass processing, in particular the effect of milk powder manufacturing and composition on the physical properties of chocolate masses

Summary The functionality of twelve different milk powders that are used for chocolate mass processing was investigated. In two types of spray‐dried and one type of roller‐dried powder, the milk fat and milk fat fractions were integrated. Depending on the production process, the amount of free fat available in the milk powders varied greatly. A good correlation was found between the free fat content of the milk powder and the viscosity of the chocolate mass when comparable particle sizes were used. This study reports on the development of spray‐dried milk powders, which when used in chocolate processing produced low viscosities, comparable with those obtained by using roller‐dried milk powder. Calorimetric analysis showed that the shape of the milk powder particles has no influence on the calorimetric qualities of chocolate masses. Only when milk fat was added in a free form, was a higher ‘mixing effect’ in the crystallization peak of cocoa butter and milk fat observed.     

Influence of milk components on properties and consumer acceptance of milk chocolate

The objective of the study was to assess the effects of various milk components on chocolate quality, defined by measurable properties and decisively by consumer liking.The choice of milk products considered different types, technologies and suppliers. Samples produced under standardised conditions were analysed for particle size, flow properties, colour and by a trained sensory panel. Consumer testing determined overall liking. Results revealed that milk ingredients influence consumer liking of milk chocolate through the quality driving parameters of particle size/sandiness, viscosity/melting mouthfeel and milk flavour. Chocolates made from milk products that contain high amounts of free fat - e.g. skim milk powder plus anhydrous milk fat - scored better than those using bound fat - e.g. whole milk powder. Milk fat status had more influence than differences between spray and roller-dried powders. High free fat cream powders were most suitable for cream chocolates. All milk components need to be free from off-notes that require sensory checks. Fillers like lactose could replace some sucrose, and whey protein concentrate can partially replace skim milk powder.     

Impact of amorphous and crystalline lactose on milk chocolate properties

Chocolate mass of low viscosity is preferred for most applications. Milk powder influences processing behaviour, flow properties and taste of milk chocolate. The project aimed to investigate influences of skim milk powders containing amorphous or crystalline lactose on flow properties after producing samples by roller milling and conching or alternatively by ball milling. For the first case, it was found that mass consistency before roller milling is strongly influenced by lactose type; producers must specify it and adapt initial mass fat content. Little impact on final products was found after processing milk powders at equilibrium moisture. If predried powders are used for reducing conching time, crystalline lactose leads to chocolate with slightly lower viscosity. At ball mill processing, crystalline lactose resulted in significantly lower viscosity, for example 15% at 40 s^?1; thus, for this process, it can be recommended to use special milk powders high in crystalline lactose content.     

Effects of selected properties of ultrafiltered spray-dried milk powders on some properties of chocolate

The effects of selected properties of spray-dried milk fat powders on chocolate were determined. Milk powders produced from control or ultrafiltered (UF) milks with various levels of fat were blended with skim milk powder to give a standard 26 g fat 100 g⁻¹ powder. Particle size of the chocolate mixes after refining decreased as the fat content and free-fat content of the powders increased. Despite this, increasing fat and free-fat contents of powders reduced the Casson viscosity of the subsequent molten chocolates. Casson viscosities using powders from control or UF milks were similar, but decreased as the particle size of powders increased and particle size after refining the chocolate mix decreased. Casson yield value and hardness decreased as fat content of powders increased. Casson yield value increased with vacuole volume of powders. It is possible to alter important properties of chocolates using milk powders of varying fat contents, free-fat contents and particle sizes.     

Effect of Sucrose on Physical Properties of Spray‐Dried Whole Milk Powder

ABSTRACT: Spray‐dried whole milk powders were prepared from whole condensed milk with various sucrose concentrations (0%, 2.5%, 5%, 7.5%, and 10% w/w), and their glass transition temperature and some physical properties of importance in chocolate manufacture were evaluated. In milk powder samples, the glass transition temperature and free‐fat content decreased in a nonlinear manner with sucrose addition. Moreover, increasing sucrose concentration reduced the formation of dents on the particle surface. Addition of sucrose in whole condensed milk increased linearly the apparent particle density and in a nonlinear manner the particle size of spray‐dried milk powders. The particle size volume distribution of milk powders with the highest sucrose concentration differed from the log‐normal distribution of the other samples due to the formation of large agglomerates. Neither vacuole volume, nor the amorphous state of milk powders was affected by sucrose addition.     

A Process for Increasing the Free Fat Content of Spray-dried Whole Milk Powder

Exposing spray‐dried whole milk powder to high shear and elevated temperature in a twin‐screw continuous mixer increased the free fat content. The effects of operating conditions (powder feed rate, processor screw speed, and process temperature) on lactose crystallinity, particle size distribution, color, and moisture content of spray‐dried whole milk powder were investigated using response surface methodology. Exposure to elevated temperatures and high shear: (a) increased the free fat to more than 80%, (b) crystallized the lactose, (c) reduced the average volume‐based particle size, and (d) broadened the particle size distribution. The raw whole milk powder with creamy‐white color turned into an oily paste with bright‐yellow color. Processing enhanced the functional properties of spray‐dried whole milk powder for milk chocolate manufacture.     

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.     

Development and application of confocal scanning laser microscopy methods for studying the distribution of fat and protein in selected dairy products.

Confocal scanning laser microscopy (CSLM) methods were developed to identify fat and protein in cheeses milk chocolate and milk powders. Various fluorescent probes were assessed for their ability to label fat or protein in selected food products in situ. Dual labelling of fat and protein was made possible by using mixtures of probes. Selected probes and probe mixtures were then used to study (a) structure development of Mozzarella cheese during manufacture and ripening, and (b)) the distribution of fat and protein in milk chocolate made with milk powders containing varying levels of free fat. Microstructural changes in the protein and fat phases of Mozzarella cheese were observed at each major step in processing. Aggregation of renneted micelles occurred during curd formation; this was followed by amalgamation of the para-casein into linear fibres during plasticization. Following storage, the protein phase of the Mozzarella became more continuous; entrapping and isolating fat globules. Chocolate made with a high free-fat spray-dried powder blend showed a homogeneous fat distribution, similar to that of chocolate made with roller-dried milk. Chocolate made with whole milk powder containing 10 g free fat/100 fat showed a non-homogeneous fat distribution with some fat occluded within milk protein particles. These differences in fat distribution were related to Casson yield value and Casson viscosity of the chocolates.     

巧克力专用乳粉

研究了不同乳粉的颗粒大小和结构、游离脂肪含量对巧克力浆料粘度的关系。滚筒乳粉与喷雾乳粉之对比，滚筒干燥的全乳粉具有下列优点；游离脂肪含量高，可减少可脂的用量，赋与巧克力以更好的风味；可降低巧克力浆料的粘度。乳粉中羟甲基糠醛含量可增进巧克力风味、口感，提高喷雾乳粉中游离脂肪含量改进的工艺。     

Influence of formulation and processing variables on ball mill refining of milk chocolate

The influence of both formulation and processing variables on the physical characteristics of milk chocolate has been studied during milling with a pilot ball mill. Nine experimental millings were carried out varying the type of dried milk used (roller, high free fat and spray-dried milk) and the time of lecithin and dried milk addition during the refining process. For the samples collected during 2 h of milling, particle size, moisture, Casson plastic viscosity and yield value were evaluated. In all the experiments, the solid particle size was effectively reduced during the first 120 min of refining; after this time the particle size reduction assumed an asymptotic trend. The addition of lecithin at the beginning of the refining kept the viscosity low and constant throughout the process, thus allowing the addition of milk from the start of the process, regardless of the technology adopted for milk drying.     

Physical properties of goat milk powder with soy lecithin added before spray drying

In this study, physical characteristics of goat milk powder produced with the addition of soy lecithin at levels of 0 (control), 0.4, 0.8 and 1.0 g lecithin/100 g of total solids in concentrated milk before the spray drying process were investigated. Goat milk was pasteurised, concentrated at 40% of total solids, spray dried and packed in plastic bags under vaccum conditions. Lecithin addition decreased the wetting time of milk powders, although no influence was observed on dispersibility, water sorption, water activity and particle size distribution of the powders. Powders with higher levels of lecithin showed significantly lower brightness, with a greater intensity of yellow colour. It was concluded that lecithin addition before spray drying process at the minimal proportion in concentrated milk of 0.4 g lecithin/100 g of total solids in concentrated milk is useful for achieving more rapid wetting time of goat milk powder.     

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.     

GRINDING SPRAY-DRIED MILK POWDER NEAR the GLASS TRANSITION TEMPERATURE

The fine grinding of chocolate is typically accomplished on five‐roll mills. Chocolate manufacturers consider milk powder, a component of milk chocolate, difficult to grind. Spray‐dried milk powders comprise a glassy lactose matrix in which fat globules, air vacuoles and protein are entrapped. the glassy‐rubbery transition in commercial milk powders usually lies between 60–70C, depending on the moisture content. A mixture of 60% wt/wt commercial whole milk powder, T_g～ 60C, and 40% wt/wt cocoa butter was ground in a three‐roll refiner at temperatures of 40, 50, 60, 70 and 75C. Below T_g the particles exhibited brittle fracture, while above T_g plastic deformation was evident and particles became highly asymmetric. the amount of fat liberated from the lactose matrix, so‐called free fat, particle density, and mean particle size increased with grinding temperature. However, the Casson yield value and plastic viscosity of finished “white chocolate” coatings, manufactured to a constant free fat content, increased with grinding temperature, suggesting an influence of particle shape on flow behavior.     

The effect of high-pressure jet processing on cocoa stability in chocolate milk

Fat-free chocolate milk formulations containing skim milk, cocoa powder, and sugar were thermally treated and then processed using high-pressure jet (HPJ) technology from 125 to 500 MPa. The rheological properties and stability of HPJ-treated chocolate milks were compared with controls (no HPJ processing) prepared both with and without added κ-carrageenan. As expected, carrageenan-free chocolate milk exhibited immediate phase separation of the cocoa powder, whereas formulations containing κ-carrageenan were stable for 14 d. An increased stability was observed with increasing HPJ processing pressure, with a maximum observed when chocolate milk was processed at 500 MPa. The apparent viscosity at 50 s⁻¹ of HPJ-processed samples increased from ~3 mPa·s to ~9 mPa·s with increasing pressure, and shear-thinning behavior (n < 0.9) was observed for samples processed at HPJ pressures ≥250 MPa. We suggest that HPJ-induced structural changes in casein micelles and new casein-cocoa interactions increased cocoa stability in the chocolate milk. Because casein seemed to be the major component enhancing cocoa stability in HPJ-treated samples, a second study was conducted to determine the effect of additional micellar casein (1, 2, or 4%) and HPJ processing (0–500 MPa) on the stability of fat-free chocolate milk. Formulations with 4% micellar casein processed at 375 and 500 MPa showed no phase separation over a 14-d storage period at 4°C. The addition of micellar casein together with HPJ processing at 500 MPa resulted in a higher apparent viscosity (~17 mPa·s at 50s⁻¹) and more pronounced shear-thinning behavior (n ≤ 0.81) compared with that without added micellar casein. The use of HPJ technology to improve the dispersion stability of cocoa provides the industry with a processing alternative to produce clean-label, yet stable, chocolate milk.     

Influence of packaging information on consumer liking of chocolate milk

Chocolate milk varies widely in flavor, color, and viscosity, and liking is influenced by these properties. Additionally, package labels (declared fat content) and brand are some of the extrinsic factors that may influence consumer perception. The objective of this study was to evaluate the effects of packaging labels and brand name on consumer liking and purchase intent of chocolate milk. A consumer acceptance test, conjoint analysis survey, and Kano analysis were conducted. One hundred eight consumers evaluated 7 chocolate milks with and without brand or package information in a 2-d crossover design. A conjoint analysis survey and Kano analysis were conducted after the consumer acceptance test. Results were evaluated by 2-way ANOVA and multivariate analyses. Declared fat content and brand influenced overall liking and purchase intent for chocolate milks to differing degrees. A subsequent conjoint analysis (n = 250) revealed that fat content was a driver of choice for purchasing chocolate milk followed by sugar content and brand. Brand name was less important for purchase intent of chocolate milk than fat or sugar content. Among fat content of chocolate milk, 2 and 1% fat level were most appealing to consumers, and reduced sugar and regular sugar were equally important for purchase intent. Kano analysis confirmed that fat content (whole milk, 1, or 2% fat chocolate milk) was an attractive attribute for consumer satisfaction, more so than brand. Organic labeling did not affect the purchase decision of chocolate milk; however, Kano results revealed that having an organic label on a package positively influenced consumer satisfaction. Findings from this study can help chocolate milk producers as well as food marketers better target their product labels with attributes that drive consumer choice of chocolate milk.     

Thickening of molten white chocolates during storage

When white chocolates are kept molten in storage tanks, problems can arise due to uncontrolled thickening and solidifying of the chocolate mass. The thickening of molten white chocolate was simulated on a laboratory scale using a rotational rheometer under static conditions, interrupted by short shear periods to measure the increasing viscosity. Several chocolates having different dairy components and fat contents were investigated for their tendency to thicken. In addition, sorption isotherms for white chocolates were obtained using Dynamic Vapour Sorption at different temperatures. The sorption isotherms showed the presence of amorphous lactose in all the chocolates that were manufactured from milk powders. Moisture that is released during the crystallisation of amorphous lactose causes stickiness and agglomeration of the neighbouring particles and starts the thickening process. This process is highly temperature-dependent. On elevating the temperature the lactose crystallisation occurs at lower relative humidities. In order to reduce the tendency of white chocolate to thicken, a high free fat level should be maintained, based on a high total fat content and on the use of high free fat milk powders, preferably roller-dried whole milk powders or the combination of skimmed milk powder and anhydrous milk fat.     

Functionality of Milk Powders and Milk‐Based Powders for End Use Applications—A Review

Abstract: Newer variants of milk powders and milk‐based powders are being produced are looking for prospective end users. Powders possess physical and functional properties that are of significance in its usage notably powder structure, particle size distribution, powder density, bulk density, particle density, occluded air, interstitial air, flowability, rehydration (wettability, sinkability, dispersibility, solubility), hygroscopicity, heat stability, emulsifying ability, water activity, stickiness, caking, and others. Some of the functional properties of significance to milk powders and milk‐based powders are discussed in this review. Applications with regard to specific milk powders for reconstituted cheese making, coffee creamers, and those suited for milk chocolate and for the baking industry are described.     

Fast conching for milk chocolate

The objective of the study was to shorten the conventional conching process for milk chocolate, which still takes many hours, in order to increase productivity. Due to recent findings and to progress made in raw material treatment, a hypothesis was proposed: that flavour development in the conch could be less important for milk chocolate than it certainly is for dark chocolate. Other functions of conching, like water removal and fat covering of particles, could be achieved faster by using drier raw materials and by machines applying more shear force. For the experiments, a conventional process (taking 5 hours) was condensed into 30–90 minutes. In screening trials various flake pre-drying techniques were also tested. Samples produced were analysed for particle size and flow properties, as well as by a trained sensory panel. Results from the experimental design showed best results at 60–90 minutes conching time. Probably the procedures for flake pre-drying had little or no influence under the conditions used. Verification trials compared the fast conching procedure to the standard process using two different recipes. No relevant differences in physical or sensory properties were found between samples from standard and 90-minute-fast-conching, proving that under favourable conditions conching times for milk chocolates can be drastically reduced without negative impact on product properties and perception.     

Fat properties during homogenization, spray-drying, and storage affect the physical properties of dairy powders

Changes in fat properties were studied before, during, and after the drying process (including during storage) to determine the consequences on powder physical properties. Several methods were combined to characterize changes in fat structure and thermal properties as well as the physical properties of powders. Emulsion droplet size and droplet aggregation depended on the homogenizing pressures and were also affected by spray atomization. Aggregation was usually greater after spray atomization, resulting in greater viscosities. These processes did not have the same consequences on the stability of fat in the powders. The quantification of free fat is a pertinent indicator of fat instability in the powders. Confocal laser scanning microscopy permitted the characterization of the structure of fat in situ in the powders. Powders from unhomogenized emulsions showed greater free fat content. Surface fat was always overrepresented, regardless of the composition and process parameters. Differential scanning calorimetry melting experiments showed that fat was partially crystallized in situ in the powders stored at 20°C, and that it was unstable on a molecular scale. Thermal profiles were also related to the supramolecular structure of fat in the powder particle matrix. Powder physical properties depended on both composition and process conditions. The free fat content seemed to have a greater influence than surface fat on powder physical properties, except for wettability. This study clearly showed that an understanding of fat behavior is essential for controlling and improving the physical properties of fat-filled dairy powders and their overall quality.