Principles of lactose crystallization and rheology of milk protein concentrate (original) (raw)

Technological aspects of lactose-hydrolyzed milk powder

Food Research International

Few reports describe the effect of lactose hydrolysis on the properties of milk powder during production and storage. Hence, the aim of this study was to evaluate the effects of five different levels of enzymatic lactose hydrolysis during the production and storage of milk powder. As the lactose hydrolysis rate increased, adhesion to the drying chamber also increased, due to higher levels of particle agglomeration. Additionally, more brown powder was obtained when the lactose hydrolysis rate was increased, which in turn negatively affected rehydration ability. Using Raman spectroscopy, crystallization of the lactose residues in various samples was assessed over 6 weeks of accelerated aging at a room temperature environment with 75.5 % of air moisture. Products with 25% or greater lactose hydrolysis showed no signs of crystallization, in contrast to the non-hydrolyzed sample.

An investigation into lactose crystallization under high temperature conditions during spray drying

Food Research International, 2010

Lactose crystallization was studied at high temperature conditions in a Buchi B-290 mini spray dryer. The inlet gas temperature was 200°C, and an insulating material was used to reduce the heat loss from the drying chamber (outlet temperature 157°C), thus increasing the gas and particle temperatures. At these conditions, lactose crystallinity was found to increase significantly compared with a case where it was spray dried at 170°C in a non-insulated drying chamber (outlet temperature 90°C), but the process yield was lower for the former case (0.16% yield) than for the low temperature conditions (47% yield). There is some evidence that high-temperature spray drying of lactose is more likely to give more b-lactose anomer. Different analytical techniques (Fourier Transform Infrared Spectroscopy, modulated differential scanning calorimetry, moisture sorption test, Raman spectroscopy) were used to investigate the degree of crystallization and possible lactose anomer formation during this spray drying at high inlet gas temperatures.

Importance of glass transition and water activity to spray drying and stability of dairy powders

Le Lait, 2002

Spray-drying is a rapid dehydration method allowing production of high quality dairy powders. In dehydration and subsequent powder handling and storage, however, both chemical and physical changes, such as caking, lactose crystallisation, and nonenzymatic browning, may impair powder characteristics and result in loss of powder quality. Many of these changes are related to the physical state of lactose, as rapid removal of water in spray drying results in the formation of lowmoisture, amorphous, noncrystalline structures of lactose and other milk components. The amorphous components may exist as solid-like glasses or highly supercooled, viscous liquids. The formation of amorphous, glassy lactose during spray drying allows production of a free-flowing powder. High temperatures or residual water contents at the later stages of the drying process, however, may cause stickiness, caking, browning, and adhesion of the powder particles to the processing equipment. The glass transition of amorphous lactose occurs in the vicinity of room temperature at a water content of about 6.8 g (g × 100)-1 of lactose corresponding to an equilibrium relative humidity of 37% and 0.37 a w (water activity). At higher water contents, as the glass transition of amorphous lactose is well below storage temperature, dairy powders become sticky and the amorphous lactose may exhibit time-dependent crystallisation. Crystallisation of amorphous lactose may also release sorbed water from the amorphous material, which enhances other deteriorative changes, such as the nonenzymatic browning reaction. Amorphous lactose in dairy powders encapsulates milk fat, which, as a result of lactose crystallisation, is released and becomes susceptible for rapid oxidation. The glass transition and water activity are, therefore, important factors controlling processability, handling properties and stability of dairy powders. Glass transition / dairy powder / spray drying / stability / water Résumé-Importance de la transition vitreuse et de l'activité de l'eau pour le séchage par atomisation et la stabilité des poudres de lait. Le séchage par atomisation est une méthode de déshydratation rapide permettant la production de poudres de lait de première qualité. Cependant, au cours

Lactose crystallisation and early Maillard reaction in skim milk powder and whey protein concentrates

Le Lait, 2005

Lactose crystallisation and Maillard reaction are two major modifications occurring in milk and whey powders during processing and storage. In this work, the aim was first to monitor the solid-state early Maillard reaction (EMR) in whey protein concentrates (WPC) heated at 60 °C and various water activities, and then, to characterise the physical changes that occur as a consequence of heat treatment in skim milk powder (SMP) and WPCs. After a w adjustment, SMP and WPC were heated at 60 °C in hermetic conditions to induce an amino-sugar reaction. Furosine analysis (% of blocked lysine) was used to monitor the progress of EMR. The results showed that the kinetic of EMR was linked to the initial a w of the powders. Heating of SMP may lead to the crystallisation of lactose in humidified powders, without apparently affecting the progress of EMR. Surprisingly, lactose crystallisation-monitored by micro-Differential Scanning Calorimetry-was easily induced in heated SMP, whereas it was delayed or even inhibited in WPC. The results showed that this effect was dependent on the protein/lactose ratio in WPCs. lactose crystallisation / early Maillard reaction / whey protein concentrate / water activity

Influence of protein concentration on surface composition and physico-chemical properties of spray-dried milk protein concentrate powders

International Dairy Journal, 2015

Surface composition, moisture sorption behaviour and glasserubber transition temperature (T gr) were determined for spray-dried milk protein concentrate (MPC) powders over a range of protein contents (35 e86 g 100 g À1). Surface characterisation of MPC powders indicated that fat and protein were preferentially located on the surface of the powder particles, whereas lactose was located predominantly in the bulk. Moisture sorption analysis at 25 C showed that MPC35 exhibited lactose crystallisation, whereas powders with higher protein contents did not and continually absorbed moisture upon humidification up to 90% RH. The GAB equation, fitted to sorption isotherms of MPCs, gave increases in monolayer moisture value (m m) with protein content. T gr , measured with a rheometer, decreased significantly (P < 0.05) with increasing water content and increased with increasing protein content (P < 0.05). In conclusion, increasing protein concentration of MPCs resulted in altered surface composition and increased m m value and T gr values.

Impact of Spray Drying Parameters on Lactose-Free Milk Powder Properties and Composition

Journal of Agricultural Studies

Lactose-free milk powders are an interesting topic, as the industry still struggles with the enhanced stickiness of the material. To better understand this topic, an industrial scale spray-dryer was used to assess the influence of process parameters on the powder properties of lactose-free milk. A simple design of experiments was conducted varying the inlet temperature in combination with the atomization flow rate. The intention was to set different driving forces for drying in combination with the different surfaces are for mass transport. Yield is typically the process bottleneck, but from results, high inlet temperature combined with small droplet size resulted in a 50.73% yield. Powder's moisture contents were between 0.53% and 5%, and water activity between 0.21 and 0.43, being all values within a safety threshold for storage. From bulk and tap density results, all powders revealed to be cohesive with the Hausner ratio above 1.5. Color measurements revealed off white sample...

Differences in the physical state and thermal behavior of spray-dried and freeze-dried lactose and lactose/protein mixtures

Innovative Food Science & Emerging Technologies, 2006

The physical state and thermal behavior of dried food ingredients are important in the control of processing and storage stability of such materials. The physical structures of spray-dried and freeze-dried anhydrous and crystalline lactose, lactose/whey protein isolate (WPI), lactose/ Na-caseinate and lactose/gelatin mixtures were observed by scanning electron microscopy (SEM). Glass transition, T g , and instant crystallization temperatures, T cr , were determined using differential scanning calorimetry (DSC). Particles in spray-dried amorphous lactose were spherical, and in lactose/protein mixtures it was also spherical with some dents. Freeze-dried lactose and lactose/protein mixtures resembled pieces of broken glass. Crystals formed from spray-dried lactose were tomahawk-like but those formed from freeze-dried lactose had needle-like or rod-like structures. T g and T cr of freeze-dried lactose and lactose/protein mixtures were slightly higher than those of spray-dried lactose and lactose/protein mixtures at corresponding water contents. But T cr of lactose/Na-caseinate and lactose/gelatin mixtures were lower in freeze-dried than in spray-dried materials. Time-dependent lactose crystallization was observed at RVP 44.1% and above in both dehydrated materials, except in freeze-dried lactose/Na-caseinate and lactose/gelatin. These results indicated that freeze-dried and spray-dried materials have different physical and thermal behavior suggesting that different microstructures and product properties are obtained with different drying methods.

Chemical and Physical Changes in Milk Protein Concentrate (MPC80) Powder during Storage

Journal of Agricultural and Food Chemistry, 2011

The solubility and chemical changes due to the Maillard reaction were investigated in milk protein concentrate powder containing 80% protein (MPC80) during storage at temperatures and relative humidities in the ranges of 25À40°C and 44À84%, respectively. The Maillard reaction was studied by measuring furosine (a product of lactosylated protein after digestion with acid) and free hydroxymethylfurfural (HMF) contents by HPLC and L*, a*, b* values with a color-meter. Furosine, free HMF, and browning in MPC80 increased during storage, whereas the solubility decreased. The correlation between the Maillard reaction and solubility loss was explored in modified MPC80 to which glucose was added to enhance the rate of the Maillard reaction. More furosine and brown pigments were observed in the glucose-containing MPC80 than in MPC80 with added lactose. The opposite trend occurred for solubility, suggesting that the Maillard reaction may be a cause of solubility loss in MPC powder.