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.     

UHT(超高温灭菌)朱古力牛乳的研制

本文介绍了UHT朱古力牛乳的制作方法及其合理、可行的超高温杀菌生产工艺 ,其主要由牛乳、朱古力、白砂糖、稳定剂等调制而成 ,经长时间观察和尝试发现该产品具有稳定性好、口感佳等特点。     

Controlling fat bloom formation in chocolate – Impact of milk fat on microstructure and fat phase crystallisation

The partial replacement of cocoa butter (CB) with milk fat (MF) strongly influences micro-scale topographic evolution and fat phase crystallisation in milk chocolate. Adding MF reduces the incidence of large surface crystals and the number and diameter of amorphous, welled CB deposits (‘cones’), with a concurrent decrease in initial surface roughness (p < 0.05) and rate of surface coarsening. Presence of MF also slows the solidification of the cones into disorganised crystalline masses. Finally, MF reduces the initial solid fat content, and slows the rate of change in whiteness index, as well as the form V to VI polymorphic transition. Fat crystal growth is accelerated by repeated temperature-cycling (26–29 °C) compared to isothermal conditioning (26 °C). However, cone hardening occurs more rapidly when isothermally-stored. Irrespective of fat composition and storage conditions, fat crystal growth, welling and ultimately fat bloom begin only at specific locations on the chocolate surface, suggesting that chocolate’s microstructural heterogeneity is responsible for distinct surface fat crystallisation pathways.     

Physical stability of chocolate milk

The stability of chocolate milk, made from two different cocoa powders and skim milk, was studied. Three types of instability could be distinguished: sedimentation of cocoa particles, formation of large flocs and formation of light and dark coloured layers (segregation). From adsorption studies and rheological measurements it could be deduced that chocolate milk behaves as a fluid with a weak network. The cocoa particles themselves are incorporated in this network structure. This network is formed by an interaction of protein and protein-covered cocoa particles in the presence of a suitable stabilizer (carrageenan). Heat treatment has a considerable effect on the interactions. Segregation is supposed to be caused by uniaxial compression of the total network due to gravitational force, and segregation will stop when the gravitational force is counterbalanced by the elastic modulus multiplied by the deformation gradient of the network. The compression may be influenced by the adherence of the network to the container wall.     

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.     

Using extra dry milk ingredients for accelerated conching of milk chocolate

Core objective of the work was to shorten conventional conching by means of omitting the dry conching phase and to replace it with a short or continuous liquefaction process. In order to achieve this for milk chocolate, it is necessary to dry milk powder below its equilibrium beforehand. Thus water removal by conching will no longer be necessary, but fat covering of particles and adjustment of flow properties still has to be done by using high shear force. In a first step a procedure was developed, in which skim milk powder is dried to <1% moisture and then coated and stabilised in fat. Milk chocolate flakes produced thereof contained <0.6% water. Secondly, conching time was gradually reduced. Flow properties of samples were very close to a standard, if enough shear was applied. Thirdly, scale up trials using industrial equipment gave similar results. A batch process now takes 15–30 min, however using a continuous high shear mixer is also feasible. Minor sensory differences between samples and standards were neither related to milk powder drying nor to fast liquefaction. Finally an outlook is given on other feasible drying methods and productivity benefits.     

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.     

New concept for fast continuous conching of milk chocolate

The objective of the development was to conch milk chocolate continuously in a device applying high shear during a short residence time. Compared with conventional conching—still taking many hours—this would increase productivity by lowering investment and energy costs. On the basis of previous tests about shortening batch conching and experiments monitoring water content during conching and its influence on flow properties the continuous high shear mixer REFLECTOR was selected. First, experiments on developing continuous dosing and parameter settings were run at low throughputs. Sample properties were very close to standard with just slightly increased yield values and only negligible differences in sensory perception. Scale-up to industrial throughput made the flow properties fall off. Possibly no more drying happened, and this is assumed to be effective at low throughput. Usage of polyglycerol polyricinoleate improved the results, although water residues were still left. The best flow properties could be achieved by combining a short conventional dry conching step with subsequent rapid liquefying by the REFLECTOR. Further process development will focus on predrying either refiner flakes or raw materials.     

Crystallization and rheological properties of soya milk chocolate produced in a ball mill

The aim of this paper is to define the optimal conditions for the pre-crystallization of chocolate produced in a ball mill, that contains 20% soya milk. Chocolate mass and soya milk are refined in a ball mill employing three refining times (30, 60 and 90 min) and pre-crystallization temperatures (26, 28 and 30 °C).     

巧克力调温工艺及其发展

介绍了巧克力调温工艺的概念，原理，类型及评价方法，探讨了调温工艺的发展。     

Effects of different milk substitutes on pasting, rheological and textural properties of puddings

Commercial pudding powders are usually composed of starch, hydrocolloids, sugars, colorings and aromas, and are intended to be dissolved in milk. However, the use of milk substitutes is mandatory for people suffering from lactose intolerance and milk allergies, but these ingredients have an effect on pudding structure and rheological behavior that has been little studied. This work investigates the pasting, rheological and textural behavior of two commercial pudding powders dissolved in rice drink, light soy drink, partially skimmed milk (reference sample), and water (model system). The eight different puddings were evaluated both during preparation (heating and cooling phases) and a 3 day refrigerated storage period, by means of viscoamylographic tests, rotational and oscillatory measurements, and penetration tests. The two pudding powders, apparently similar in formulation, resulted in final products with large structural differences, that could be ascribed to different types and quantity of starch and carrageenans present in the formulation. Soy and rice drinks can not be indifferently used for pudding production, as the optimal texture of the final product is not always achieved. Generally, the properties of soy drink-based puddings were similar to those of the reference samples, while the characteristics of rice drink-based products were comparable to those of the water systems.     

Optimisation of processing conditions and rheological properties using stephan mixer as conche in small‐scale chocolate processing

This study investigated the suitability of Stephan mixer for use as conche during small‐scale chocolate production in an attempt to reduce cost and processing time. Molten chocolate was processed using the Stephan mixer under different temperature and time combinations and Buhler Elk'Olino conche (as reference), and the flow properties (Casson plastic viscosity, Casson yield stress and thixotropy) were studied using a shear‐rate‐controlled rheometer. Optimum settings of 65 °C for 10 min at 443  g dry conching followed by 50 °C for 15 min at 443  g wet conching in the Stephan mixer resulted in similar flow properties as the reference sample. Increasing the blade rotary speed for both dry and wet conching resulted in a decrease in flow properties. The Stephan mixer proved to be suitable for conching small‐scale (approximately 1 kg) chocolate productions and could be explored as a fast and cost‐effective method for small‐scale chocolate conching processes.     

Cleaning of whey protein and milk salts soiled on DLC coated surfaces at high-temperature

New surface coatings offer great potential to reduce deposition on heat exchanger surfaces and to improve their cleanability. However, the surface coating must be resistant to thermal, chemical and mechanical stress during processing and cleaning. The aims of this investigation were to evaluate the potential of DLC (diamond-like carbon) coatings to enhance the cleaning efficiency of milk soil and to identify surface parameters influencing its cleaning behavior.     

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。     

朱古力乳酸奶饮料的研制和生产技术

本文研究了以低脂奶粉、可可粉为主要原料生产朱古力乳酸奶饮料的生产工艺、操作要点和产品质量标准。生产的朱古力乳酸奶饮料 ,质量稳定、口感柔和、营养丰富     

Influence of cocoa butter refining on the quality of milk chocolate

A refining step is often crucial for the removal of undesired components in fats and oils. More flexible refining technologies are required due to a global decline in cocoa butter quality and to meet industry’s demand for cocoa butters with improved properties. The aim was to investigate the impact of the cocoa butter refining process on milk chocolate quality. Therefore a crude cocoa butter was subjected to a steam refining at different temperatures and this with or without a silica pretreatment. The major effect of the silica pretreatment was the complete removal of phosphorus (thus phospholipids), iron and alkaline components. During the steam refining step mainly Free Fatty Acids (FFA) were removed at increased temperatures (T ? 200 °C). The refining of the cocoa butter influenced the rheological properties of the chocolate. An increased packed column temperature, coinciding with the removal of FFA, resulted in a lower yield stress and a higher viscosity. Reduction of FFA positively influenced the crystallization kinetics and the formation of the crystal network, resulting in differences on a macroscopic scale.     

UHT咖啡牛奶饮品的研制

通过对咖啡牛奶饮品的配方、工艺及稳定性的研究,确定了最佳配方及工艺参数,制成的咖啡牛奶饮品口感细腻,常温保存六个月组织状态均匀。     

Study of the mineral content of chocolate flavoured beverages

The concentrations of sodium, potassium, calcium, magnesium, sulfur and phosphorus (major elements) and iron, copper, zinc, selenium, molybdenum, chromium and manganese (minor elements) in chocolate-flavoured beverages from São Paulo State, Brazil, were determined. Different brands of this kind of beverage were analysed after digestion in a microwave oven and the quantification of the elements was done by inductively coupled argon plasma atomic emission spectrometry (ICP OES). Forty-four different samples from 13 different brands were studied, with significant differences in the contents of both major and minor elements formed between and within the different brands. However, it was possible to conclude that the samples analysed are good sources of K, Ca, Mg, S and P, and mainly those whose compositions included powdered milk. On the other hand, chocolate-flavoured beverages are shown to be poor sources of sodium. The data were examined by multivariate analysis with application of the method of pattern recognition (hierarchical grouping or cluster analysis).     

Pre-dried refiner flakes allow very short or even continuous conching of milk chocolate

Chocolate conching is usually still performed in a time consuming batch process. For milk chocolate, its main purpose is to remove water and to adjust flow properties. As the conch is not an efficient dryer and flow properties are mainly influenced by shear treatment, the objective of this study was to separate and optimise both processes. Prior to liquefaction, refiner flakes were dried to <0.6% of water in an oven, which allows to omit the dry phase of conching. Conventional conching of 5 h was then reduced to a liquefaction process taking 20 min. Alternatively, continuous processing was tested applying a high shear mixer REFLECTOR^®. Sample properties were very close to a standard. Only continuous liquefaction at very high throughput resulted in slightly increased viscosity. Sensory analyses just found negligible differences. Thus neither pre-drying nor short or continuous liquefaction had a negative impact on product quality.     

Fouling behaviour of milk and whey protein isolate solution on doped diamond-like carbon modified surfaces

Doped diamond-like carbon (DLC) coated stainless steel surfaces were studied for their fouling behaviour with milk and whey protein isolate (WPI) solution at both laboratory and pilot-scale. Stainless steel (316 SS 2B) surfaces were modified with three different doped DLC coatings (DLC-1, DLC-2 and DLC-3) using plasma assisted chemical vapour deposition. At the laboratory-scale, the DLC-1 coated surface showed a statistically significant reduction in the mass of milk fouling deposits. However, at the pilot-scale, none of the modified surfaces offered significant benefit in fouling mitigation over the control stainless steel surface. Subsequently, in the laboratory-scale trials with a whey protein isolate (WPI) solution, the mass of fouling deposits for all doped DLC modified surfaces were about 35–40% lower in comparison to their controls when fouled for 120 min. However, these benefits were reduced to less than 15% with longer fouling duration. Thus, the results obtained in this study found no commercial benefit of modified surfaces in fouling mitigation when fouled for longer times with skim milk, whole milk or WPI solution.