Modeling of Lactose Crystallization and Color Changes in Model Infant Foods

Abstract

Lactose crystallization and color changes in formulas containing beta-lactoglobulin and gelatinized starch were investigated. Model infant formulas were prepared by colyophilization of 3 components (lactose, beta-lactoglobulin, and gelatinized starch). A mixture design was used to choose the percentage of each mixture component. These formulas were stored for 3 mo at different relative humidities (RH), ranging from approximately 0 to 94.6%, to study the lactose crystallization and color changes. Crystallization kinetics was studied by gravimetric methods, and lactose state (crystalline vs. amorphous) was verified before and after storage by differential scanning calorimetry. Before storage, lyophilized lactose was amorphous, but during storage it crystallized, depending on the RH. The lactose crystallization RH depended on the quantity of beta-lactoglobulin and gelatinized starch, and by increasing these quantities, the crystallization RH increased. For some formulas, the crystallization RH was noted at 3 different RH during storage. The first was noted after 1 d of storage and the second and third were observed later on, showing that crystallization is a time-dependent phenomenon. Nonenzymatic browning was studied in model infant formulas by yellow color changes of samples at 11.3, 43.2, 54.5, and 75.4% RH. In this study, 7 mathematical models were proposed to predict the moisture sorption properties and color changes at different RH, and the models were validated by experimental results.

Mechanical relaxation times as indicators of stickiness in skim milk–maltodextrin solids systems

“…Lactose crystallization in the systems appeared at higher a w when maltodextrin contents were increased. This was consistent with the results of delayed amorphous lactose crystallization in mixes with sugars and high molecular weight polymers (Berlin et al, 1968(Berlin et al, , 1972Roos and Karel, 1991a;Gabarra and Hartel, 1998;Kouassi and Roos, 2001;Haque and Roos, 2004a,b;Foster et al, 2005;Nasirpour et al, 2006;Silalai and Roos, 2010a). After lactose crystallization, the loss of sorbed water of skim milk-maltodextrin solids systems with 10% (w/w) maltodextrin (DE9) was higher than in the systems with 10% (w/w) maltodextrin (DE17) as shown in Fig.…”

Fractionation and some physicochemical properties of almond gum (Amygdalus communis L.) exudates

“…The higher hygrscopicity of the water soluble fraction compared to that of the whole gum and its soluble fraction is in good match with its total carbohydrate content. Moreover, it is well established that amorphous compounds show higher hygroscopicity values (Nasirpour et al, 2006). As already explained, the insoluble fraction has a higher crystallinity index than the whole almond gum and the soluble fraction, giving rise to its lower tendency for water absorption.…”

“…For this purpose, an exact amount of 1.0 g of each sample was placed in a desicator over a saturated solution of Mg(NO 3 ) 2 (RH ¼ 54.5, temp. ¼ 25 C) for 14 days (Nasirpour, Scher, Linder, & Desobry, 2006). Each sample was weighed on a daily basis to determine the weight increase until the sample reached a constant weight.…”

Lactose: Crystallization, hydrolysis and value-added derivatives

“…In some instances, impurities may inhibit the formation of the nuclei. The effects on crystal growth are a function of intricate physico-chemical interactions of available energies, adsorption rate to the various crystal faces, steric hindrance caused by proteins and polysaccharides, tendency to spontaneous nucleation, and the concentration of substances in question (Nasirpour, Scher, Lindner, & Desobry, 2006;Nickerson, 1974). In the presence of impurities, lactose crystals tend to be irregularly shaped and clumped, instead of yielding the characteristic crystals obtained from simple lactose solutions (Nickerson, 1962).…”