Maillard reaction and protein cross-linking in relation to the solubility of milk powders

Glycation of goat milk with different casein-to-whey protein ratios and its effects on simulated infant digestion

This research compared the effects of dry heating on the digestion of goat milk proteins with different casein-to-whey ratios (40% casein, C40 and 80% casein, C80). The glycation markers of heated samples were determined by LC-MS. Heating at 60 °C for 8 h induced early glycation while heating at 60 °C for 72 h induced advanced glycation. Unheated C80 samples showed a higher digestibility than unheated C40 samples, which may be due to their higher protein solubility. After dry heating for 72 h, no significant difference in digestibility was observed between C80 and C40 samples. Heating for 72 h decreased the digestibility of C40 samples compared to unheated samples, probably due to glycation, while protein aggregation was the main reason for the reduced digestibility of heated C80 samples. Overall, this study showed that dry heating for 72 h induced a lower digestibility of C80 and C40 samples, although with different underlying mechanisms.

"Milk on Ice": A detailed analysis of Ernest Shackleton's century-old whole milk powder in comparison with modern counterparts

Whole milk powder (WMP) manufactured in New Zealand in 1907 was sent to the Antarctic continent with the Shackleton-led British Antarctic Expedition from 1907 to 1909. This powder was stored at ambient conditions at Shackleton's Hut at Cape Royds, Antarctica, for over 100 yr before a sample was collected on behalf of Fonterra by the Antarctic Heritage Trust. Having spent most of its existence both dried and in frozen storage, any deleterious reactions within the WMP would have been markedly retarded. The composition and some properties of the roller-dried Shackleton's WMP are reported along with those of 2 modern spray-dried New Zealand WMP. The Shackleton powder was less white and more yellow than the modern WMP and was composed of flakes rather than agglomerated particles, consistent with that expected of a roller-dried powder. Headspace analysis showed lipolytic and oxidative volatile compounds were present in the Shackleton WMP, indicting some deterioration of the milk either before powder manufacture or on storage of the finished product. On a moisture-free basis, the Shackleton WMP had higher protein, higher fat (with a markedly higher free fat level), higher ash, and a lower lactose level than the modern WMP. The lysine level was lower in the Shackleton WMP compared with the spray-dried powders, whereas the fatty acid composition was relatively similar. The sodium level was markedly higher in the Shackleton WMP compared with the spray-dried powder, which is probably due to the addition of an alkaline sodium salt to adjust the pH of the milk before roller drying. Lead, iron, and tin levels were markedly higher in the Shackleton WMP compared with the spray-dried powders, possibly due to the equipment used in powder manufacture and the tin-plated cases used for storage. The proteins in the Shackleton WMP were more lactosylated than in the spray-dried powders. The Shackleton WMP had a higher ratio of κ-casein A to B variants and a higher ratio of β-lactoglobulin B to A variants than the spray-dried powders, whereas the αS1-casein, β-casein, αS2-casein, and α-lactalbumin protein variants were similar in all powders. The total phospholipid content was markedly lower in the Shackleton WMP than the spray-dried powders, primarily due to a lower phosphatidylethanolamine concentration. The molecular species distributions within the phospholipid classes were generally similar in the 3 powders. Claims are sometimes encountered that the milk of today is different from that consumed by previous generations. However, this comparative study has shown that the Shackleton WMP was generally similar to modern WMP. Although differences in some components and properties were observed, these were attributable to the manufacturing equipment and processes used in the pioneering years of WMP manufacture.

Structure and in vitro digestion characteristics of skim goat milk protein during processing: effects of fat separation

BACKGROUND

Although nonfat milk has been used worldwide in the industrial dairy process, little is known about the effects of fat separation during the manufacturing process on skim milk's structural and digestive properties. This study investigated the effects of the manufacturing process on the structure and in vitro digestion properties of skim goat milk, particularly emphasizing fat separation.

RESULTS

Changes in the surface charge and hydrophobicity of milk proteins caused by fat separation resulted in oxidation and aggregation in the subsequent homogenization, heat and spray-drying processing, which affected its digestibility. Compared with separation by dish separator (DS), skim milk after tubular centrifugal separation (CS) showed a higher initial and final digestibility. The CS samples also had a lower surface hydrophobicity level and higher free sulfhydryl content, ζ-potential, and average particle size (P < 0.05). Goat milk protein after CS was more readily oxidized and aggregated during the subsequent homogenization and heat treatment, as evidenced by the higher carbonyl content and particle size. Centrifugal separation also converted more β-sheets to α-helices, thus promoting the aggregation of oxidized skim milk protein.

CONCLUSION

The skim milk after CS and DS demonstrated different structural and digestive properties. Skim goat milk products after CS were more susceptible to oxidant-induced protein structural changes, resulting in higher protein digestibility. These findings provide insights into the mechanism involved in the control of gastric digestion of skim milk during manufacturing process. © 2023 Society of Chemical Industry.

Valorization of Sour Buttermilk (A Potential Waste Stream): Conversion to Powder Employing Reverse Osmosis and Spray Drying

Reverse osmosis (RO) is known for the economic dewatering of dairy streams without any change in phase. At the household level, surplus milk is fermented and churned to obtain butter, which is subsequently heated to obtain clarified milk fat (ghee). The production of 1 kg ghee generates 15-20 kg sour buttermilk (SBM) as a by-product that is mostly drained. This causes a loss of milk solids and environmental pollution. The processing, preservation and valorization of SBM are quite challenging because of its low total solids (TS) and pH, poor heat stability and limited shelf life. This investigation aimed to transform SBM into a novel dried dairy ingredient. SBM was thermized, filtered, defatted and concentrated at 35 ± 1 °C, employing RO up to 3.62× (12.86%). The RO concentrate was subsequently converted into sour buttermilk powder (SBMP) by employing spray drying. SBMP was further characterized for its physicochemical, reconstitution and functional properties; rheological and morphological characteristics; and amino acid and fatty acid profiling, along with FTIR and XRD spectra. SBMP was "instant soluble-3 s" and exhibited excellent emulsion stability (80.70%), water binding capacity (4.34 g/g of protein), flowability (28.36°) and antioxidant properties. In nutshell, a process was developed for the valorization of sour buttermilk to a novel dairy ingredient by employing reverse osmosis and a spray-drying process.

Protein interactions during dry and wet heat pre-treatment of skim milk powder (dispersions) and their effect on the heat stability of recombined filled evaporated milk

Skim milk powder (SMP) as well as aqueous dispersions were subjected to dry and wet heat pre-treatment, respectively, to improve the heat stability of recombined filled evaporated milk (RFEM) derived therefrom. However, microrheological analysis revealed that prolonged incubation caused detrimental effects on the heat stability of RFEM, which were thought to be due to protein interactions. SDS-PAGE results indicated that protein aggregation via non-disulfide covalent bonds occurred upon long-time dry or wet heat incubation. This was probably related to some Maillard reaction products, which is sustained by the increase in lactulose and protein carbonyl content. Considerable protein aggregation via disulfide bonds in the serum was found upon wet heat incubation at temperatures of at least 80 °C. Principal component analysis (PCA) revealed that the negative effects of overprocessing on the heat stability of RFEM were predominantly related to protein cross-linking via non-disulfide covalent bonds related to protein carbonylation.

Deciphering the segregation of proteins in high-protein dairy powders after spray-drying

High-protein dairy powders are ingredients mainly produced by spray-drying, then subjected to aging during transport and storage. They often undergo physicochemical changes at this stage, such as the development of the Maillard reaction, primarily because of their intrinsic chemical properties, but also as a result of nonoptimal storage conditions. Components present at the particle surface are the first to be targeted by moisture and other environmental disruptions. Consequently, the identification, control, and prediction of particle surface components are useful to anticipate the effect of powder aging on product quality. Here, a new diafiltration method is proposed which fractionates proteins from a binary colloidal dispersion of 80% casein micelles and 20% whey proteins, according to their presence at the surface or core of the particle. This method shows that whey proteins are strongly enriched at the particle surface, whereas casein micelles are located at the core of the particles. This protocol also allows the identification of the rehydration kinetics for each rehydrated protein layer of the particle, revealing that 2 distinct forms of swelling occur: (1) a rapid swelling and elution of whey proteins present at the particle surface, and (2) a swelling of casein micelles located below the whey proteins, associated with a slow elution of casein micelles from the particles being rehydrated.

Foaming and Physicochemical Properties of Commercial Protein Ingredients Used for Infant Formula Formulation

Protein, as one of the main ingredients for infant formula, may be closely related to the undesirable foam formed during the reconstitution of infant formula. Demineralized whey powder (D70 and D90), whey protein concentrate (WPC), and skimmed milk powder (SMP) are the four protein ingredients commonly used in infant formula formulation. The foaming and physicochemical properties of these four protein ingredients from different manufacturers were analyzed in the present study. Significant differences (p < 0.05) in foaming properties were found between the samples from different manufacturers. SMP showed a highest foaming capacity (FC) and foam stability (FS), followed by D70, D90, and WPC. Although the protein composition was similar based on reducing SDS-PAGE, the aggregates varied based on non-reducing SDS-PAGE, probably resulting in the different foaming properties. Particle size, zeta potential, and solubility of the protein ingredients were assessed. The protein structure was evaluated by circular dichroism, surface hydrophobicity, and free sulfhydryl. Pearson’s correlation analysis demonstrated that FC and FS were positively correlated with random coil (0.55 and 0.74), β-turn (0.53 and 0.73), and zeta potential (0.55 and 0.51) but negatively correlated with β-strand (−0.56 and −0.71), free sulfhydryl (−0.56 and −0.63), particle size (−0.45 and −0.53), and fat content (−0.50 and −0.49). The results of this study could provide a theoretical guidance for reducing formation of foam of infant formula products during reconstitution.

A process optimization approach for microwave vacuum drying of concentrated skim milk

Microwave vacuum drying (MVD) of concentrated skim milk and its resulting powder properties have been studied to a very limited extent. To explore the potential of this technology for the manufacture of milk powder, MVD of concentrated skim milk (37.5% total solids) was evaluated with respect to product properties and drying efficiency. A custom factorial design was used to optimize drying parameters, which enabled us to find optimal drying conditions with a minimal number of drying experiments (16). Vacuum level (3.3-13.3 kPa), specific power input (0.86-1.72 W·g^-1), and product layer thickness (1-4 mm) were studied as factors. Total drying time, product foaming at the beginning of the process, product temperature in the last drying interval, browning, insolubility index, and calculated product yield were used as responses to identify optimal MVD processing parameters. Optimal drying of concentrated skim milk that maximized yield and minimized drying time while maintaining good product quality was achieved at a layer thickness of 2 mm, pressure of 6.0 kPa, and a specific power input of 1.29 W·g^-1. Under constant power output, layer thickness was found to be the most important processing parameter to control product temperature during the final drying stage. Maximum product temperatures below 55°C yielded powder with good solubility. The findings of this exploratory study for MVD of concentrated skim milk yield important information and guidelines for production of good quality milk powders or preservation of starter cultures in a dairy matrix such as infant formula.

Autoclaving time-related reduction in metabolizable energy of poultry meal is greater in growing pigs compared with broiler chickens

The objective of this study was to determine the energy utilization responses of growing pigs and broiler chickens to poultry meal that was autoclaved at 134 °C for 0 to 180 min. Poultry meal from the same batch was autoclaved at 134 °C for 7 autoclaving times of 0, 30, 60, 90, 120, 150, or 180 min to generate 7 samples. Eight experimental diets consisting of a basal diet based on corn and soybean meal, and seven test diets in which 15% of energy-contributing ingredients in the basal diet were replaced with each of the seven poultry meal samples were used. In experiment 1, there were 64 barrows (initial body weight = 19.4 ± 1.0 kg) allotted to 8 experimental diets in a randomized complete block design with body weight as a blocking factor. Each pig received an experimental diet during 5 d of adaptation followed by 5 d of quantitative total, but separate, collection of urine and feces. In experiment 2, a total of 512 male broiler chickens at day 17 post-hatching (initial body weight = 660 ± 80 g) in 8 replicate cages were allotted to 8 experimental diets in a randomized complete block design with body weight as a blocking factor. Excreta were collected from days 20 to 22 post-hatching, and birds were euthanized by CO2 asphyxiation for ileal digesta collection. Data from experiments 1 and 2 were pooled together for statistical analysis as a 2 × 7 factorial treatment arrangement with the effect of species (pigs or broiler chickens) and autoclaving time of poultry meal (7 autoclaving times between 0 and 180 min). An interaction between species and their linear effect of autoclaving time was observed (P < 0.05) in metabolizable energy (ME) of poultry meal. Specifically, linear decrease in ME values in poultry meal with increasing autoclaving time was greater (P < 0.05) in growing pigs (4,792 to 3,897 kcal/kg dry matter) compared with broiler chickens (3,591 to 3,306 kcal/kg dry matter). The ME value of unautoclaved poultry meal was greater (P < 0.01) for pigs than broiler chickens at 4,792 vs. 3,591 kcal/kg dry matter. Although decrease in ME values with autoclaving time of poultry meal was greater in growing pigs than in broiler chickens, the ME in autoclaved poultry meal fed to pigs was greater than ME in non-autoclaved poultry meal fed to broiler chickens. Furthermore, the ratio of cysteine to crude protein concentration is a potential indicator for estimating the ratio of ME to gross energy in poultry meal for growing pigs (r2 = 0.81) and broiler chickens (r2 = 0.84).

A Literature Review on Maillard Reaction Based on Milk Proteins and Carbohydrates in Food and Pharmaceutical Products: Advantages, Disadvantages, and Avoidance Strategies

Milk has two main components that have high nutritional value—milk protein (casein and whey protein), and lactose. These components are extensively used in various areas, especially in food, i.e., as sweeteners, stabilizers, functional food ingredients, nutritional fortifiers, etc. Non-enzymatic browning refers to a series of chemical reactions between sugars and proteins that make food more appetizing. Non-enzymatic browning reactions include degradation of ascorbic acid, lipid peroxidation, caramel reaction, and the Maillard reaction (MR). The MR, as one of the four non-enzymatic browning reactions, has been well studied and utilized in food fields. Milk protein and lactose, as two main components of milk, have high chemical activities; they are used as reactants to participate in the MR, generating Maillard reaction products (MRPs). The MR involves a condensation reaction between carbonyl groups of various sugars and amino groups of amino acids/proteins. These MRPs have different applications in various areas, including food flavor, food oxidation resistance, drug carriers, etc. This work presents the positive and negative effects of the MR, based on the two main components of milk, used in food and medicine, as well as avoidance approaches to prevent the occurrence of negative effects.

Effect of water activity on the functional, colloidal, physical, and microstructural properties of infant formula powder

We report on the physicochemical changes of infant formula (IF) powder and its macronutrients (lactose, fat, and proteins) under given storage conditions. Colloidal (particle size distribution, emulsion stability and sedimentation), morphological (scanning electron microscopy), thermal (differential scanning calorimetry), structural (synchrotron X-ray diffraction) as well as surface and chemical (X-ray photoelectron and Fourier transform infrared spectroscopies) data were used to elucidate the main cause-effect relationships for microstructural, functional, and other properties of the IF powder. The wetting behavior of the powder was found to be significantly affected by water activity (a_w) during storage (a_w in the range between 0.24 and 0.42). At the highest a_w (a_w = 0.42), lactose crystallization and fat migration took place, leading to changes on the surface of the particles that reduced powder wettability. We propose possible mechanisms to explain the observations, associated with changes in protein conformation. Interestingly, no major changes in the pH and colloidal characteristics, including particle size and distribution, stability, and sedimentation were observed in the reconstituted IF powder upon storage for 6 weeks. The results indicated a negligible contribution from possible Maillard reactions. We propose leading microstructural and wetting characterization to troubleshoot changes in the quality of IF powder, most relevant from the perspective of reconstitution after storage.

Effect of dynamic ultra-high pressure homogenization on the structure and functional properties of whey protein

The effects of dynamic ultra-high pressure homogenization (UHPH) on the structure and functional properties of whey protein were investigated in this study. Whey protein solution of 10 mg/mL (1% w/w) was prepared and processed by a laboratory scale high pressure homogenizer with different pressures (25, 50, 100, 150, 200, and 250 MPa) at an initial temperature of 25 °C. Then, the solution samples were evaluated in terms of secondary structure, sulfhydryl and disulfide bond contents, surface hydrophobicity, average particle size, solubility, foaming capacity, emulsifying activity, and thermal properties. It was found that the secondary structure of whey protein changed with the dynamic UHPH treatment. The interchange reaction between the disulfide bond and the sulfhydryl group was promoted and the surface hydrophobicity significantly increased. The functional properties of the whey protein accordingly changed. Specifically, after dynamic UHPH treatment, the average particle size of the whey protein and emulsion decreased while the solubility, the foaming capability and the emulsification stability increased significantly. The results also revealed that with the dynamic UHPH at 150 MPa, the best improvement was observed in the whey protein functional properties. The whey protein solubility increased from 63.15 to 71.61% and the emulsification stability improved from 195 to 467 min.

Mechanochemically Induced Controlled Glycation of Lysozyme and Its Effect on Enzymatic Activity and Conformational Changes

Protein glycation through heating of a mixture of protein and reducing sugars is one of the most commonly used methods of protein modification; however, in most cases, this approach can lead to uncontrolled glycation. The hypothesis that mechanical energy supplied through ball milling can induce glycation of proteins was tested using a well-characterized enzyme lysozyme. The Q-TOF/MS analysis of the milled samples has indicated that the milling of sugar-protein mixtures in stainless steel jars for 30 min and at a frequency of 30 Hz generated mainly monoglycated proteins even with the highly reactive ribose. Increasing the sugar concentration or the milling time did not influence the overall yield or generate more glycoforms. Enzymatic activity measurements, FTIR, and fluorescence spectroscopic studies have indicated that milling of lysozyme alone leads to a significant loss in enzymatic activity and structural integrity in contrast to milling in the presence of sugars.

Storage of Micellar Casein Powders with and without Lactose: Consequences on Color, Solubility, and Chemical Modifications

During storage, a series of changes occur for dairy powders, such as protein lactosylation and the formation of Maillard reaction products (MRPs), leading to powder browning and an increase of insoluble matter. The kinetics of protein lactosylation and MRP formation are influenced by the lactose content of the dairy powder. However, the influence of lactose in the formation of insoluble matter and its role in the underlying mechanisms is still a subject of speculation. In this study, we aim to investigate the role of lactose in the formation of insoluble matter in a more comprehensive way than the existing literature. For that, two casein powders with radically different lactose contents, standard micellar casein (MC) powder (MC1) and a lactose-free (less than 10 ppm) MC powder (MC2), were prepared and stored under controlled conditions for different periods of time. Powder browning index measurements and solubility tests on reconstituted powders were performed to study the evolution of the functional properties of MC powders during aging. Proteomic approaches [one-dimensional electrophoresis and liquid chromatography-mass spectrometry (LC-MS)] and innovative label-free quantification methods were used to track and quantify the chemical modifications occurring during the storage of the powders. Reducing the amount of lactose limited the browning of MC powders but had no effect on the loss of solubility of proteins after storage, suggesting that the action of lactose, leading to the production of MRC, does not promotes the formation of insoluble matter. Electrophoresis analysis did not reveal any links between the formation of covalent bonds between caseins and loss in solubility, regardless of the lactose content. However, LC-MS analyses have shown that different levels of chemical modifications occur during the MC powder storage, depending upon the presence of lactose. An increase of protein lactosylation and acetylation was observed for the powder with a higher lactose content, while an increase of protein deamidation and dephosphorylation was observed for that containing lower lactose. The decrease of pH in the presence of lactose as a result of Maillard reaction (MR) may explain the difference in the chemical modifications of the two powders. In view of the present results, it is clear that lactose is not a key factor promoting insolubility and for the formation of cross-links between caseins during storage. This suggests that lactosylation is not the core reaction giving rise to loss in solubility.

Protein cross-linking and the Maillard reaction decrease the solubility of milk protein concentrates

Milk protein concentrate (MPC) is a widely used material in the food industry. However, despite its widespread use, the mechanism underlying the decreased solubility of MPC that occurs during storage has not yet been clarified. In this study, the solubility changes, protein cross-linking, and Maillard reaction and the relationships between them were investigated in modified MPC powders (MMPC) containing different concentrations of protein and/or lactose stored at 50°C for 15-45 days. The results demonstrated that both the protein and lactose contents affected solubility. The proteins interacted through hydrogen bonding, disulfide bonding, hydrophobic interactions, and nondisulphide covalent bonding, which led to cross-linking. The Maillard reaction promoted protein cross-linking and was in turn influenced by protein cross-linking. The Maillard reaction was slower when the degree of protein cross-linking was greater. These results improve our understanding of the mechanism leading to poor solubility of MPC powders during storage.

Evaluation of the heat damage of whey and whey proteins using multivariate analysis

Maillard reaction (MR) was assessed in 10 powdered whey samples. Initial stages of MR were evaluated using furosine, intermediate stages with hydroxymethylfurfural (HMF) and absorbance at 284nm, advanced stages with color parameters (CIELab color) and final stages with browning index; additionally, insolubility, pH and water activity (Aw) were measured. Principal component analysis (PCA) and cluster analysis (CA) were used to establish the heat damage of samples based on relations between variables. Three principal components were found which explained 79.0% of the total variance and they were the basis for cluster analysis where 5 clusters were formed. PCA and CA can separate samples according to their heat damage and they help in a clearer interpretation of the information from indicators which shows that samples with high lactose content exhibited the higher heat damage.

Changes in physical and gelling properties of freeze-dried egg white as a result of temperature and relative humidity

BACKGROUND

The quality of dried egg white with respect to functional properties can be affected by storage conditions. The effect of temperature and relative humidity (RH) on changes in colour and gelling properties in freeze-dried egg white (FDEW) during storage was investigated.

RESULTS

The glass transition temperature (Tg ) of FDEW decreased with increasing % RH. The colour of FDEW stored at 60 °C was darker yellow than those at 40 and 25 °C, particularly at high % RH. RH had no effect on hardness and water-holding capacity (WHC) of gels made from FDEW stored at 25 °C for 1 week. However, hardness and WHC of gels from FDEW stored at higher temperatures; 40 °C, 48% RH and 60 °C, 11% RH dramatically increased. These results related to the differential scanning calorimeter thermograms which showed a broadening peak with lower enthalpy of protein denaturation. Moreover, the protein's SDS-PAGE pattern in the samples stored at high temperatures or RH levels showed protein aggregation.

CONCLUSION

Storage of FDEW at high temperature and RH levels induced protein conformation changes. These have contributed to protein aggregation which affected the gelling properties of FDEW. © 2016 Society of Chemical Industry.

Generation of Soluble Advanced Glycation End Products Receptor (sRAGE)-Binding Ligands during Extensive Heat Treatment of Whey Protein/Lactose Mixtures Is Dependent on Glycation and Aggregation

Heating of protein- and sugar-containing materials is considered the primary factor affecting the formation of advanced glycation end products (AGEs). This study aimed to investigate the influence of heating conditions, digestion, and aggregation on the binding capacity of AGEs to the soluble AGE receptor (sRAGE). Samples consisting of mixtures of whey protein and lactose were heated at 130 °C. An in vitro infant digestion model was used to study the influence of heat treatment on the digestibility of whey proteins. The amount of sRAGE-binding ligands before and after digestion was measured by an ELISA-based sRAGE-binding assay. Water activity did not significantly affect the extent of digestibility of whey proteins dry heated at pH 5 (ranging from 3.3 ± 0.2 to 3.6 ± 0.1% for gastric digestion and from 53.5 ± 1.5 to 64.7 ± 1.1% for duodenal digestion), but there were differences in cleavage patterns of peptides among the samples heated at different pH values. Formation of sRAGE-binding ligands depended on the formation of aggregates and was limited in the samples heated at pH 5. Moreover, the sRAGE-binding activity of digested sample was changed by protease degradation and correlated with the digestibility of samples. In conclusion, generation of sRAGE-binding ligands during extensive heat treatment of whey protein/lactose mixtures is limited in acidic heating condition and dependent on glycation and aggregation.

The Maillard reaction of a shrimp by-product protein hydrolysate: chemical changes and inhibiting effects of reactive oxygen species in human HepG2 cells

A shrimp by-product protein hydrolysate via the Maillard reaction could alleviate cellular damage, but result in higher HMF and loss of nutritional quality.

Quantification of allergenic bovine milk α(S1)-casein in baked goods using an intact ¹⁵N-labeled protein internal standard

Intact bovine ¹⁵N-α(S1)-casein was used as an internal standard in a selected reaction monitoring (SRM) assay for milk protein in baked food samples containing fats, sugar, and gums. Effects on SRM results of sample matrix composition in two biscuit recipes containing nonfat dry milk (NFDM) were studied, including samples from a milk allergen ELISA proficiency trial. Following extraction of defatted samples with carbohydrate-degrading enzymes and acid precipitation of casein, the SRM assay exhibited an LOQ of <3 ppm NFDM with 60-80% recovery. NFDM levels measured by the SRM assay were 1.7-2.5 times greater than median levels determined by ELISA. Differences were observed in the α(S1)-casein interpeptide SRM ion abundance profile between recipes and after baking. ¹⁵N-α(S1)-Casein increases SRM analysis accuracy by correcting for extraction recovery but does not eliminate underestimation of allergen concentrations due to baking-related milk protein transformation (modifications).