Color formation and Maillard reactions during the spray drying process of skim milk and model systems

Abstract

The thermal degradation of fresh skim milk, reconstituted skim milk and two model systems with different lactose/WPI ratios in a new design of spray dryer has been investigated. The extent of thermal degradation has been measured by the formation of Advanced Maillard reaction products, as assessed by a fluorometric method. Significant changes have been found when the inlet temperature increased from 180 C to 190 C, suggesting that temperature may play an important role in the kinetics of milk degradation in spray dryers. The non-uniform distribution of particle residence time in the pilot-scale dryer suggested that the design and operation of the spray dryer used for drying may also affect the extent of thermally induced reactions during the spray-drying process. Results from the spray drying of model systems with different lactose/WPI ratios suggested that WPI concentration may be the rate-limiting factor. Colourimetric analysis of the samples suggested a strong correlation between the formation of advanced Maillard reaction products and the color intensities of the spray-dried products. Practical ApplicationsA correlation exists between the color intensity of the spray-dried products and formation of advanced Maillard reaction products, which can be potentially further developed as a rapid, cost-effective quality evaluation method for spray-dried products. The discussion of the effect of spray drying conditions on the wall-deposition and re-entrainment process and thus the particle residence time distribution may also assist in improving the spray-drying process for thermally sensitive products. | INTRODUCTIONSpray drying is a common method used for drying liquid feedstocks.One of the key applications of spray drying is in the final stage of milk powder production. Other than the requirements for a low final moisture content and other physical properties of dried products, the flavor, the nutritional values, and the appearance of the dried milk are also important, so the loss of volatile components and heat-induced degradation should be minimized during the spray-drying process.Heat-induced degradation includes denaturation and aggregation of proteins (e.g., caseins, whey proteins), Maillard reactions, enzyme inactivation and lactulose isomerization (Jaskulski, Atuonwu, Tran,

Microencapsulation of Erythrocytes Extracted from Cavia porcellus Blood in Matrices of Tara Gum and Native Potato Starch

“…The study of color is relevant to the organoleptic properties of products fortified with iron encapsulants [ 28 , 31 ]. In addition, they are affected by the natural color of the wall materials used [ 16 , 56 , 57 ], and the amount of these used in spray drying [ 58 , 59 ], which would cause changes in the color shades due to non-enzymatic browning reactions at high temperatures [ 60 , 61 ]. Another essential aspect to consider would be the possible caramelization of carbohydrates due to the effect of high temperatures, which would contribute to a more significant darkening of the products obtained [ 62 , 63 ].…”

Modeling Maillard reaction kinetics in spray dryers using both lumped‐ and distributed‐parameter modeling approaches

“…The extent of Maillard reactions in the samples was measured using the method described in the previous study by Zhou and Langrish (2021b), which is a fluorometric method for measuring the extent of Maillard reactions proposed by Birlouez-Aragon et al (1998). Samples were reconstituted with distilled water to a concentration of 8.8 wt.%, and the fluorometric measurement of the diluted samples was carried out by using a Horiba FluoroMax-4 spectrometer.…”

“…Spray drying of the model systems with different whey protein isolate (WPI) and lactose ratios was described and carried out in the previous study by Zhou and Langrish (2021b). The overall heat loss coefficient of the spray dryer to the environment was approximately 5 W m À2 K À1 .…”

Particle residence time distributions in different configurations of a pilot-scale spray dryer

“…These fans provide drying air at a flow rate of 257 m 3 /h together when operating at full capacity. [11] Fig. 2 Spray dryer with conical drying chamber…”

“…Particle residence time distributions were measured using the devices described in Zhou's study (2021). [11] In short, tracer (red food dye) was introduced into the atomizer as pulses every three minutes. As the tracer and feed (skim milk droplets) refract the laser differently, changes in the light intensity occur that were detected by a photomultiplier located at the outlet of the drying chamber.…”