Lactose in dairy ingredients: Effect on processing and storage stability

Abstract

Lactose is the main carbohydrate in the milk of most species. It is present in virtually all dry dairy ingredients, with levels ranging from <2% (e.g., caseinates, milk protein isolates) to 100% in lactose powders. The presence of lactose has a strong effect on ingredient processing and stability. Lactose can negatively influence powder properties and lead to undesirable effects, such as the stickiness of powder resulting in fouling during drying, or caking and related phenomena during storage. In addition, being a reducing carbohydrate, lactose can also participate in the Maillard reaction with free amino groups of proteins, peptides, and free AA. In this review, the influence of the presence (or absence) of lactose on physiochemical properties of dairy ingredients is reviewed, with particular emphasis on behavior during processing and storage. Particularly important features in this respect are whether lactose is in the (glassy) amorphous phase or in the crystalline phase, which is strongly affected by precrystallization conditions (e.g., in lactose, permeate, and whey powders) and by drying conditions. Furthermore, the moisture content and water activity of the ingredients are important parameters to consider, as they determine both mobility and reactivity, influencing Maillard reactions and concomitant browning, the crystallization of amorphous lactose during storage of dairy ingredients, glass transitions temperatures, and associated stickiness and caking phenomena. For the stickiness and caking, a crucial aspect to take into account is powder particle surface composition in relation to the bulk powder. Lactose is typically underrepresented at the powder surface, as a result of which deviations between observed lactose-induced caking and stickiness temperatures, and determined glass transition temperatures arise. By considering lactose as an integral part of ingredient composition along with all other compositional and environmental properties, lactose behavior in dairy ingredients can be understood, controlled, and optimized. Routes to achieve this are outlined in this review paper.

Introductory Chapter: Lactose

“…Therefore, the width of the MZ determines the temperature drop necessary to induce lactose nucleation. After nucleation, crystals' growth depends on the degree of lactose saturation and the temperature, since the last one affects lactose solubility [7,[9][10][11][12][13]. The overall process of lactose crystallization is slow.…”

Sonocrystallization of Lactose from Whey

“…In contrast, if the nucleation is slow and fewer crystals nucleate at a time, the supersaturation in the solution drops slowly, the nucleation of new crystals continues, and the solution presents a wider crystal size distribution (CSD) [21]. Other variables that affect the crystal growth are the temperature, viscosity, pH, presence of salts, and whey proteins, which modify the levels of supersaturation and consequently the nucleation and crystal growth [24][25][26]. Speaking of impurities like salts and proteins, these can either accelerate or inhibit the crystal growth.…”

“…In the same way, the whey proteins promote nucleation but slow down the growth of lactose crystals. This effect is attributed to its high water-binding capacity that creates areas of lactose supersaturation, which are favorable for nucleation [25].…”

“…This clarified and defatted (0.07%) whey must be deproteinized in advance to the concentration step. The presence of whey proteins decreases the solubility of lactose [24], promotes nucleation, accelerates the lactose crystallization [25], and reduces the purity of lactose crystals [5]. Besides, proteins increase significantly the viscosity of the concentrated whey, hindering the recovery of lactose crystals [5].…”

“…The process of lactose crystallization is conventionally carried out in presence of residual whey proteins (0.1-0.2%), which also decrease significantly the crystals size. The water-binding capacity of whey proteins creates supersaturation spots that favor nucleation [24,25]. A few studies have addressed the effect of whey proteins on lactose sonocrystallization.…”