Lactose crystallization and Maillard reaction in simulated milk powder based on the change in water activity

Maillard reaction (MR) and lactose crystallization (LC) are important reactions in the storage of milk powder. In this study, three models with different proteins based on skimmed milk powder were established to investigate the relationship between MR and LC at different water activities (a_w ). Moisture sorption isotherm, glass transition temperature (T_g ), and glycation products were evaluated, and the protein structure and lactose crystallinity were determined. The results indicated that MR product content, browning, and LC subsequently enhanced with the increase in a_w . The T_g value dropped lower than 0 at a_w 0.43 in whey protein isolate-lactose (WP-Lac) model and at a_w 0.54 in casein-whey protein isolate-lactose (CN-WP-Lac) model and casein-lactose (CN-Lac) model. The crystallinity of α-lactose monohydrate and anhydrous β-lactose in WP-Lac model was more significant than CN-WP-Lac and CN-Lac models (p < 0.05). The molecular band of whey protein gradually blurred in the Sodium dodecyl-sulfate polyacrylamide gel electrophoresis image, and the content of α-helix of WP-Lac model increased by 45.15% from a_w 0.33 to 0.53 (p < 0.05), while that of CN-WP-Lac model increased by only 3.95% (p < 0.05). With the increase in a_w , WP-Lac model formed more browning and crystallization products than CN-WP-Lac model, indicating that the presence of micelle macromolecules and the interaction between casein and whey proteins limited the browning and crystallization in CN-WP-Lac model. Practical Application Maillard reaction and lactose crystallization are important reactions in the storage of milk powder, and the result will provide theoretical guidance for the development of milk powder in the food industry.

Pectin oligosaccharides from hawthorn (Crataegus pinnatifidaBunge. Var. major) inhibit the formation of advanced glycation end products in infant formula milk powder

Pectin oligosaccharides (POSs) can not only be used as prebiotics but also can be used as natural food-borne antiglycation agents, which is related to their structure, including molecular weight and galacturonic acid content.

Development of quantitation method for glycated aminophospholipids at the molecular species level in powdered milk and powdered buttermilk

The Maillard reaction is a nonenzymatic glycation reaction between a reducing sugar and a free amino group, known to naturally occur during heat processing of food. In this study, we especially focused on phosphatidylethanolamine (PE)-linked Amadori products (Amadori-PE) in powdered milk, since the analysis of these products at the molecular species level has not yet been evaluated. Analysis of Amadori-PE was conducted by using liquid chromatography-tandem mass spectrometry in three different modes. The main Amadori-PE species in a powdered milk sample were first identified as 34:1, 36:1, 36:2 and 36:3 in the total ion current mode. Additionally, by using the characteristic product ions observed in the presence of sodium, we quantified the main Amadori-PE species in the multiple reaction monitoring mode, and evaluated their total concentrations in the precursor ion scan (PIS) mode for the first time. Powdered milk contained much Amadori-PE with concentrations ranging from 4.3 to 8239 mg/100 g, quantified by the PIS mode. The newly developed methods represent powerful tools for detailed analysis of glycated lipids including Amadori-PE in powdered milk, which may further be applied to research relating to infant food and nutrition.

Effect of plant polyphenols on the formation of advanced glycation end products from β-lactoglobulin

Dietary exposure to advanced glycation end products (AGEs) formed from proteins and reducing sugars is of increasing concern to human health. AGEs may form in protein-based powders containing sugars for instant beverages during drying and storage of the product. Chlorogenic acid, a plant phenol characteristic of coffee, was found to protect against the formation of AGEs at a concentration of 50mM during heating of β-lactoglobulin in the presence of glucose as a reducing sugar in 30% aqueous ethanol at 70°C. Epicatechin, a plant phenol characteristic of green tea, had no similar effect for the equivalent concentration of phenol on the formation of AGEs. Immunochemical detection (ELISA) using polyclonal antibodies raised against AGEs showed a dose-dependent effect of protection by chlorogenic acid on AGE formation and is recommended for routine quality control of sugar containing milk-based powders for instant beverages.

The inhibitory effects of γ-glutamylcysteine derivatives from fresh garlic on glycation radical formation

The effects of three reactive peptides, γ-glutamylmethylcysteine (γ-GMC), γ-glutamylpropylcysteine (γ-GPC), and γ-glutamylbutylcysteine (γ-GBC) on the suppression of reactive radicals during the heating of l-lysine in the presence or absence of glucose was studied by electron spin resonance spectroscopy. γ-GMC and γ-GPC were extracted from fresh garlic, and γ-GBC was a synthetic peptide. The results showed that γ-GMC and γ-GPC effectively suppress formation of l-lysine radicals, but that γ-GBC exhibits low radical inhibition. The origin of the short peptides, and the length of their side chain, influenced their surface hydrophobicity and subsequent radical inhibition. In addition, the oxidation of l-lysine was inhibited by the peptides in a similar manner to their inhibition of the Maillard reaction (MR), and their radical inhibition was consistent with similar activity towards N(ε)-(carboxymethyl)lysine (CML).

Free Radical Processes in Non-enzymatic Browning of Glucose and Lysine: Influence of Temperature and Unsaturated Lipids

Formation of dialkylpyrazinium radical cations in aerated 70 % aqueous glycerol solutions of glucose and lysine during heating resulting in browning (90, 110, and 130°C, investigated) was more dependent on temperature than formation of brown colour. Activation energy (Ea) for radical formation was ~83 kJ mol–1, compared with ~70 kJ mol–1 for browning, and was unaffected by methyl linolenate. Low-temperature browning was influenced by non-radical degradation of Amadori products, whereas radical processes were prominent at higher temperatures and were unaffected by unsaturated lipids. In contrast, methyl linolenate reacts with lysine in the absence of glucose to form fluorescent products at a slow rate (Ea 25 kJ mol–1). Glucose increased the rate of formation of fluorescent products (Ea ~60 kJ mol–1), in agreement with Maillard reactions at low temperatures involving glucose as a rate-determining reagent. Lipid oxidation does not have a direct effect on lysine and glucose browning reactions at conditions relevant for food; effects of lipids on Maillard reactions are matrix-related.