The structure of the casein micelle of milk and its changes during processing

Gastric digestion of cow milk, almond milk and oat milk in rats

In this study, gastric digestion of isocaloric and iso-macronutrient cow milk, almond milk and oat milk were compared in rats euthanized at different post-feeding times.

Temperature-dependent dissociation of human micellar β-casein: Implications of its phosphorylation degrees and casein micelle structures

Temperature-dependent dissociation of human micellar β-casein regarding its phosphorylation degrees and micelle structures were studied. Human milk was fractionated at 25 °C into soluble (S-25 °C) and micellar (M-25 °C) fractions, and the latter was fractionated at 4 °C into soluble (S-4 °C) and micellar (M-4 °C) fractions. β-casein ratios among S-25 °C, S-4 °C and M-4 °C were 19%, 59% and 22%. β-casein isoforms were predominated by 0-P, 1-P and 2-P in S-25 °C, by 0-P, 1-P, 2-P and 4-P in S-4 °C, and by 0-P in M-4 °C. For micelles remained after dissociation of β-casein and calcium, the size increased, molar mass decreased, morphologies were maintained, and internal protein inhomogeneities disappeared, compared with micelles in M-25 °C. β-casein isoforms with lower phosphorylation degrees may form a frame mainly through hydrophobic interactions, attached with more highly phosphorylated isoforms and colloidal calcium phosphate via calcium bridges for forming human micelle.

Effect of processing on the bioaccessibility of essential minerals in goat and cow milk and dairy products assessed by different static in vitro digestion models

The study evaluated the effect of goat and cow milk processing on the bioaccessibility of calcium, magnesium and zinc using different methods following the static in vitro simulation of gastrointestinal digestion: solubility and dialysis models. Raw goat and cow milks were processed to obtain pasteurized milk, yogurt and cheese. In general, goat milk and dairy products presented higher bioaccessibility of Ca and Mg than cow milk and dairy products. The milk processing affected the minerals bioaccessibility indicating the importance of food structure, composition and minerals equilibrium on the in vitro digestion and bioaccessibility prediction. The potential absorptions of Ca and Zn were higher in cheeses when compared to the milks and yogurts, independently of the method used. The minerals bioaccessibility evaluated by the solubility method was higher than the obtained by dialysis method for all the products evaluated.

Characterization of a Novel Aspartic Protease from Rhizomucor miehei Expressed in Aspergillus niger and Its Application in Production of ACE-Inhibitory Peptides

Rhizomucor miehei is an important fungus that produces aspartic proteases suitable for cheese processing. In this study, a novel aspartic protease gene (RmproB) was cloned from R. miehei CAU432 and expressed in Aspergillus niger. The amino acid sequence of RmproB shared the highest identity of 58.2% with the saccharopepsin PEP4 from Saccharomyces cerevisiae. High protease activity of 1242.2 U/mL was obtained through high density fermentation in 5 L fermentor. RmproB showed the optimal activity at pH 2.5 and 40 °C, respectively. It was stable within pH 1.5-6.5 and up to 45 °C. RmproB exhibited broad substrate specificity and had K_m values of 3.16, 5.88, 5.43, and 1.56 mg/mL for casein, hemoglobin, myoglobin, and bovine serum albumin, respectively. RmproB also showed remarkable milk-clotting activity of 3894.1 SU/mg and identified the cleavage of Lys21-Ile22, Leu32-Ser33, Lys63-Pro64, Leu79-Ser80, Phe105-Met106, and Asp148-Ser149 bonds in κ-casein. Moreover, duck hemoglobin was hydrolyzed by RmproB to prepare angiotensin-I-converting enzyme (ACE) inhibitory peptides with high ACE-inhibitory activity (IC₅₀ of 0.195 mg/mL). The duck hemoglobin peptides were further produced at kilo-scale with a yield of 62.5%. High-level expression and favorable biochemical characterization of RmproB make it a promising candidate for cheese processing and production of ACE-inhibitory peptides.

Active cargo loading into extracellular vesicles: Highlights the heterogeneous encapsulation behaviour

Extracellular vesicles (EVs) have demonstrated unique advantages in serving as nanocarriers for drug delivery, yet the cargo encapsulation efficiency is far from expectation, especially for hydrophilic chemotherapeutic drugs. Besides, the intrinsic heterogeneity of EVs renders it difficult to evaluate drug encapsulation behaviour. Inspired by the active drug loading strategy of liposomal nanomedicines, here we report the development of a method, named "Sonication and Extrusion-assisted Active Loading" (SEAL), for effective and stable drug encapsulation of EVs. Using doxorubicin-loaded milk-derived EVs (Dox-mEVs) as the model system, sonication was applied to temporarily permeabilize the membrane, facilitating the influx of ammonium sulfate solution into the lumen to establish the transmembrane ion gradient essential for active loading. Along with extrusion to downsize large mEVs, homogenize particle size and reshape the nonspherical or multilamellar vesicles, SEAL showed around 10-fold enhancement of drug encapsulation efficiency compared with passive loading. Single-particle analysis by nano-flow cytometry was further employed to reveal the heterogeneous encapsulation behaviour of Dox-mEVs which would otherwise be overlooked by bulk-based approaches. Correlation analysis between doxorubicin auto-fluorescence and the fluorescence of a lipophilic dye DiD suggested that only the lipid-enclosed particles were actively loadable. Meanwhile, immunofluorescence analysis revealed that more than 85% of the casein positive particles was doxorubicin free. These findings further inspired the development of the lipid-probe- and immuno-mediated magnetic isolation techniques to selectively remove the contaminants of non-lipid enclosed particles and casein assemblies, respectively. Finally, the intracellular assessments confirmed the superior performance of SEAL-prepared mEV formulations, and demonstrated the impact of encapsulation heterogeneity on therapeutic outcome. The as-developed cargo-loading approach and nano-flow cytometry-based characterization method will provide an instructive insight in the development of EV-based delivery systems.

High-quality milk exosomes as oral drug delivery system

Many drugs must be administered intravenously instead of oral administration due to their poor oral bioavailability. The cost of repeated infusion treatment for 6 weeks every year is as high as tens of billions of dollars worldwide. Exosomes are nano-sized (30-150 nm) extracellular vesicles secreted by mammalian cells due to environmental stimulation or self-activation. Milk contains abundant exosomes originated from multiple cellular sources. It has been proved that milk exosomes (MEs) could survive with the strongly acidic conditions in the stomach and degradative conditions in the gut. Furthermore, they can cross biological barriers to reach targeted tissues. The ability of MEs to cross the gastrointestinal barrier makes them as a promising drug delivery tool for oral delivery. This review is devoted to the purification of MEs, their biocompatibility and immunogenicity, and prospects for their use as natural drug carriers for oral administration.

Influence of Glycomacropeptide on Rehydration Characteristics of Micellar Casein Concentrate Powder

Glycomacropeptide (GMP) shows potential for enhancing the rehydration properties of high-protein dairy powders due to its hydrophilic nature. This study involved formulating micellar casein concentrate (MCC) solutions (8.6% final protein content) with 0, 10, and 20% GMP as a percentage of total protein, and investigated the physicochemical and rehydration properties of the resultant freeze-dried powders (P-MCC-0G, P-MCC-10G, and P-MCC-20G, respectively). The surface charges of caseins in the control MCC and 10 or 20% GMP blended solutions were −25.8, −29.6, and −31.5 mV, respectively. Tablets prepared from P-MCC-10G or P-MCC-20G powders displayed enhanced wettability with contact angle values of 80.6° and 79.5°, respectively, compared with 85.5° for P-MCC-0G. Moreover, blending of GMP with MCC resulted in faster disintegration of powder particles during rehydration (i.e., dispersibility) compared to P-MCC-0G. Faster and more extensive release of caseins from powder particles into solution was evident with the increasing proportion of GMP, with the majority of GMP released within the first 15 min of rehydration. The results of this study will contribute to further development of formulation science for achieving enhanced solubility characteristics of high-protein dairy powder ingredients, such as MCC.

Casein Micelles as an Emerging Delivery System for Bioactive Food Components

Bioactive food components have potential health benefits but are highly susceptible for degradation under adverse conditions such as light, pH, temperature and oxygen. Furthermore, they are known to have poor solubilities, low stabilities and low bioavailabilities in the gastrointestinal tract. Hence, technologies that can retain, protect and enable their targeted delivery are significant to the food industry. Amongst these, microencapsulation of bioactives has emerged as a promising technology. The present review evaluates the potential use of casein micelles (CMs) as a bioactive delivery system. The review discusses in depth how physicochemical and techno-functional properties of CMs can be modified by secondary processing parameters in making them a choice for the delivery of food bioactives in functional foods. CMs are an assembly of four types of caseins, (α_s1, α_s2, β and κ casein) with calcium phosphate. They possess hydrophobic and hydrophilic properties that make them ideal for encapsulation of food bioactives. In addition, CMs have a self-assembling nature to incorporate bioactives, remarkable surface activity to stabilise emulsions and the ability to bind hydrophobic components when heated. Moreover, CMs can act as natural hydrogels to encapsulate minerals, bind with polymers to form nano capsules and possess pH swelling behaviour for targeted and controlled release of bioactives in the GI tract. Although numerous novel advancements of employing CMs as an effective delivery have been reported in recent years, more comprehensive studies are required to increase the understanding of how variation in structural properties of CMs be utilised to deliver bioactives with different physical, chemical and structural properties.

Skimmed milk structural dynamics during high hydrostatic pressure processing from in situ SAXS

Understanding the changes in milk at a nanostructural level during high-pressure (HP) treatment can provide new insights to improve the safety and functionality of dairy products. In this study, modifications of milk nanostructure during HP were studied in situ by small-angle X-ray scattering (SAXS). Skimmed milk was pressurized to 200 or 400 MPa at 25, 40 or 60 °C and held for 5 or 10 min, and the effect of single- and double-HP treatment was also investigated. In most cases, the SAXS patterns of skimmed milk are well fitted with a three-population model: a low-q micellar feature reflecting the overall micelle size (~0.002 Å^-1), a small casein cluster contribution at intermediate-q (around 0.01 Å^-1) and a high-q (0.08-0.1 Å^-1) population of milk protein inhomogeneities. However, at 60 °C a scattering feature of colloidal calcium phosphate (CCP) which is normally only seen with neutron scattering, was observed at 0.035 Å^-1. By varying the pressure, temperature, holding and depressurization times, as well as performing cycled pressure treatment, we followed the dynamic structural changes in the skimmed milk protein structure at different length scales, which depending on the processing conditions, were irreversible or reversible within the timescales investigated. Pressure and temperature of the HP process have major effects, not only on size of casein micelles, but also on "protein inhomogeneities" within their internal structure. Under HP, increasing processing time at 200 MPa induced re-association of the micelles, however, the changes in the internal structure were more pressure-dependent than time dependent.

High Hydrostatic Pressure Induced Changes in the Physicochemical and Functional Properties of Milk and Dairy Products: A Review

High-pressure processing (HPP) is a nonthermal technology used for food preservation capable of generating pasteurized milk products. There is much information regarding the inactivation of microorganisms in milk by HPP, and it has been suggested that 600 MPa for 5 min is adequate to reduce the number of log cycles by 5-7, resulting in safe products comparable to traditionally pasteurized ones. However, there are many implications regarding physicochemical and functional properties. This review explores the potential of HPP to preserve milk, focusing on the changes in milk components such as lipids, casein, whey proteins, and minerals, and the impact on their functional and physicochemical properties, including pH, color, turbidity, emulsion stability, rheological behavior, and sensory properties. Additionally, the effects of these changes on the elaboration of dairy products such as cheese, cream, and buttermilk are explored.

Replacement of animal proteins in food: How to take advantage of nutritional and gelling properties of alternative protein sources

Given the growing world population, there is a need to balance animal and vegetable sources of dietary protein and to limit overall protein resources, and food formulation has to consider alternative protein sources as a way to meet human requirements. The protein concentration, essential amino acids (EAA) of all protein sources were analyzed with respect to human needs along with additional macronutrients of nutritional and energy interest (i.e. carbohydrates and lipids). New indexes are proposed to classify the alternative protein sources considering their EAA balance and how it may change during food processing. A global overview of all protein sources is provided including the quantity of food and associated caloric intakes required to fulfill our daily protein needs. As texture is a key parameter in food formulation, and is often influenced by protein gelation, we conducted an exhaustive review of the literature in a large scientific database on the ability of proteins from all sources to go through the sol-gel transition with the corresponding physical-chemical conditions. Traditional and innovative recipes are discussed and some improvement are proposed in terms of their ability to fulfill human needs for EAA and food and caloric intakes.

Distribution and variation in proteins of casein micellar fractions response to heat-treatment from five dairy species

Casein micelles (CMs) contribute to the physicochemical properties and stability of milk. However, how the proteome of CMs changes following heat treatment has not been elucidated. Here, changes in the proteins of CMs in samples of Holstein, buffalo, yak, goat, and camel milk following heat treatment were investigated using a LC-MS/MS approach. According to the hierarchical clustering results, Holstein, yak, and buffalo milk samples had similar CMs protein components, followed by goat and camel milk samples. Changes in lipoprotein lipase and α-lactalbumin in CMs were dependent on the intensity of heat treatment and were similar among the studied species, whereas changes in κ-casein, lactoferrin, and apolipoprotein A-I differed among different types of milk. These results provide information on the distribution and variations of the proteomes of CMs following heat treatment, which will assist in the identification of proteins that are dissociated and attached to CMs from different dairy species during heat treatment.

Progress in micellar casein concentrate: Production and applications

Micellar casein concentrate (MCC) is a novel ingredient with high casein content. Over the past decade, MCC has emerged as one of the most promising dairy ingredients having applications in beverages, yogurt, cheese, and process cheese products. Industrially, MCC is manufactured by microfiltration (MF) of skim milk and is commercially available as a liquid, concentrated, or dried containing ≥9, ≥22, and ≥80% total protein, respectively. As an ingredient, MCC not only imparts a bland flavor but also offers unique functionalities such as foaming, emulsifying, wetting, dispersibility, heat stability, and water-binding ability. The high protein content of MCC represents a valuable source of fortification in a number of food formulations. For the last 20 years, MCC is utilized in many applications due to the unique physiochemical and functional characteristics. It also has promising applications to eliminate the cost of drying by producing concentrated MCC. This work aims at providing a succinct overview of the historical progress of the MCC, a review on the manufacturing methods, a discussion of MCC properties, varieties, and applications.

Current Developments in Native Nanometric Discoidal Membrane Bilayer Formed by Amphipathic Polymers

Unlike cytosolic proteins, membrane proteins (MPs) are embedded within the plasma membrane and the lipid bilayer of intracellular organelles. MPs serve in various cellular processes and account for over 65% of the current drug targets. The development of membrane mimetic systems such as bicelles, short synthetic polymers or amphipols, and membrane scaffold proteins (MSP)-based nanodiscs has facilitated the accommodation of synthetic lipids to stabilize MPs, yet the preparation of these membrane mimetics remains detergent-dependent. Bio-inspired synthetic polymers present an invaluable tool for excision and liberation of superstructures of MPs and their surrounding annular lipid bilayer in the nanometric discoidal assemblies. In this article, we discuss the significance of self-assembling process in design of biomimetic systems, review development of multiple series of amphipathic polymers and the significance of these polymeric "belts" in biomedical research in particular in unraveling the structures, dynamics and functions of several high-value membrane protein targets.

Skimmed Goat's Milk Powder Enriched with Grape Pomace Seed Extract: Phenolics and Protein Characterization and Antioxidant Properties

The aim of this research was phenolics and protein characterization and antioxidant properties evaluation of skimmed thermally treated goat's milk powder enriched with different concentration of grape pomace seed extract (SE). The dominant phenolics in SE were phenolic acids, flavan-3-ols and procyanidins. Different electrophoretic techniques together with UHPLC-MS/MS analysis revealed the presence of phenolics-protein interactions in the samples, mainly procyanidins with whey protein/caseins complexes. Addition of SE into thermally treated goat's milk significantly improved antioxidant properties of goat's milk such as TAC, FRP, DPPH^• and ABTS^•+ scavenging activity. Gallic acid, catechin, and procyanidins mostly contributed to these activities. The schematic representation of phenolics-casein micelles interactions in thermally treated goat's milk enriched with SE was given. The addition of SE into thermally treated goat's milk can be a promising strategy in food waste recovery and to enhance the beneficial health effects of goat's milk-based functional foods.

Spectroscopic and docking studies of the interaction mechanisms of xylitol with α-casein and κ-casein

The molecular interactions of xylitol (XY) with α-casein (α-CN) and κ-casein (κ-CN) at pH 7.4 as a function of temperature (298, 308, and 318 K) were characterized by multispectral techniques and molecular docking. The fluorescence results showed that XY strongly quenched the intrinsic fluorescence of α- and κ-CN by static quenching, as well as the presence of a single binding site for XY on both proteins with a binding constant value of ∼10⁵ L/mol. The binding affinity of both proteins for XY decreased with increasing temperature, and Van der Waals forces, hydrogen bonding and protonation were the key forces in the interactions. The addition of XY altered the polarity of the microenvironment of proteins and changed their secondary structure from ordered to disordered. The molecular docking results showed that XY had different binding sites to α- and κ-CN, with several amino acids involved in the binding processes.

Effect of protein concentrate mixtures and dietary addition of exogenous phytase on major milk minerals and proteins, including casein phosphorylation

Variations in major milk minerals, proteins, and their posttranslational modifications are largely under genetic influence, whereas the effect of nongenetic factors is less studied. Through a controlled feeding experiment (incomplete balanced Latin square design), the effect of concentrate mixtures, based on fava beans, rapeseed meal, or soybean meal as main P and protein sources, on milk composition was examined under typical Danish management conditions. Concentrations of P, Ca, and Mg, together with proteomics for relative quantification of major milk proteins and their isoforms, were analyzed in milk samples from 24 cows sampled in 4 periods. Each cow was fed 1 of the 3 diets in each period with or without addition of exogenous phytase. Cows were blocked by lactation stage into early and mid-lactation (23.3 ± 6.7 and 176 ± 15 d in milk, respectively, at the beginning of the experiment, mean ± standard deviation). Significant effects of feed concentrate mixture were observed for milk protein concentration, milk urea nitrogen, citrate, and the percentage of mixed and preformed fatty acids as well as mineral composition, and their distributions within micellar or serum phases. Furthermore, relative contents of α_S1-casein (CN) 9P form and unglycosylated κ-CN and thereby phosphorylation degree of α_S1-CN (PD) and the glycosylation degree of κ-CN were found to be significantly affected by these diets. To our knowledge, we are the first to document that feed concentrate mixture can affect the relative concentrations of α_S1-CN phosphorylation isoforms in milk, and the results suggested an effect on α_S1-CN 9P and PD, but not on α_S1-CN 8P. Furthermore, although only significant for α_S1-CN 8P, we found a lower relative concentration of α_S1-CN 8P and higher α_S1-CN 9P (and thus higher PD) in milk from cows in mid compared with early lactation. Also, protein concentration and concentration of Mg in skim milk and serum as well as relative concentration of α-lactalbumin were found to be significantly affected by lactation stage. Addition of dietary exogenous phytase only had a minor effect on milk composition or functionality with significant effect detected for α-lactalbumin and micellar Mg concentration.

The mineral profile affects the coagulation pattern and cheese-making efficiency of bovine milk

Natural variations in milk minerals, their relationships, and their associations with the coagulation process and cheese-making traits present an opportunity for the differentiation of milk destined for high-quality natural products, such as traditional specialties or Protected Designation of Origin (PDO) cheeses. The aim of this study was to quantify the effects of the native contents of Ca, P, Na, K, and Mg on 18 traits describing traditional milk coagulation properties (MCP), curd firming over time (CF_t) equation parameters, cheese yield (CY) measures, and nutrient recoveries in the curd (REC) using models that either included or omitted the simultaneous effects of milk fat and casein contents. The results showed that, by including milk fat and casein and the minerals in the statistical model, we were able to determine the specific effects of each mineral on coagulation and cheese-making efficiency. In general, about two-thirds of the apparent effects of the minerals on MCP and the CF_t equation parameters are actually mediated by their association with milk composition, especially casein content, whereas only one-third of the effects are direct and independent of milk composition. In the case of cheese-making traits, the effects of the minerals were mediated only negligibly by their association with milk composition. High Ca content had a positive effect on the coagulation pattern and cheese-making traits, favoring water retention in the curd in particular. Phosphorus positively affected the cheese-making traits in that it was associated with an increase in CY in terms of curd solids, and in all the nutrient recovery traits. However, a very high P content in milk was associated with lower fat recovery in the curd. The variation in the Na content in milk only mildly affected coagulation, whereas with regard to cheese-making, protein recovery was negatively associated with high concentrations of this mineral. Potassium seemed not to be actively involved in coagulation and the cheese-making process. Magnesium content tended to slow coagulation and reduce CY measures. Further studies on the relationships of minerals with casein and protein fractions could deepen our knowledge of the role of all minerals in coagulation and the cheese-making process.

Recent advances in the application of ultrasound in dairy products: Effect on functional, physical, chemical, microbiological and sensory properties

Alternative methods for improving traditional food processing have increased in the last decades. Additionally, the development of novel dairy products is gaining importance due to an increased consumer demand for palatable, healthy, and minimally processed products. Ultrasonic processing or sonication is a promising alternative technology in the food industry as it has potential to improve the technological and functional properties of milk and dairy products. This review presents a detailed summary of the latest research on the impact of high-intensity ultrasound techniques in dairy processing. It explores the ways in which ultrasound has been employed to enhance milk properties and processes of interest to the dairy industry, such as homogenization, emulsification, yogurt and fermented beverages production, and food safety. Special emphasis has been given to ultrasonic effects on milk components; fermentation and spoilage by microorganisms; and the technological, functional, and sensory properties of dairy foods. Several current and potential applications of ultrasound as a processing technique in milk applications are also discussed in this review.

Effect of pH and heat treatment conditions on physicochemical and acid gelation properties of liquid milk protein concentrate

Milk protein concentrates (MPC) are typically dried high-protein powders with functional and nutritional properties that can be tailored through modification of processing conditions, including temperature, pH, filtration, and drying. However, the effects of processing conditions on the structure-function properties of liquid MPC (fluid ultrafiltered milk), specifically, are understudied. In this report, the pH of liquid MPC [13% protein (70% protein DM basis), pH 6.7] was adjusted to 6.5 or 6.9, and samples at pH 6.5, 6.7, and 6.9 were subjected to heat treatment at either 85°C for 5 min or 125°C for 15 s. Sodium dodecyl sulfate PAGE was used to determine the distribution of caseins and denatured whey proteins in the soluble and micellar phases, and HPLC was used to quantify native whey proteins as a measure of denaturation, based on the processing conditions. Both heat treatments resulted in substantial whey protein denaturation at each pH, with β-lactoglobulin denatured more extensively than α-lactalbumin. Changes in liquid MPC physicochemical properties were monitored at d 1, 5, and 8 during storage at 4°C. Viscosity increased after heat treatment and also over time, regardless of pH and heating conditions, suggesting the role of whey protein denaturation and aggregation, and their interactions with casein micelles. The MPC samples processed at pH 6.9 had a significantly higher viscosity than those heated at pH 6.5 or 6.7, for both temperature and time conditions; and samples processed at 85°C for 5 min had higher viscosity than those heated at 125°C for 15 s. Particle size analysis indicated the presence of larger particles after 5 and 8 d of MPC storage after heating at pH 6.9. Acid-induced gelation of the liquid MPC led to significantly higher gel firmness after processing at 85°C for 5 min, compared with 125°C for 15 s. Also, gels made from MPC adjusted to pH 6.5 had higher storage moduli, with both time and temperature combinations, demonstrating the role of pH-dependent association of denatured whey proteins with casein micelles in gel network formation. These findings enable a better understanding of the processing factors contributing to structural and functional properties of liquid MPC and can be helpful in tailoring milk protein ingredient functionality for a variety of food products.

Identify the interactions between phytochemicals and proteins in the complicated food matrix

Phytochemicals usually mix with food proteins in our regular diet. Unexpected interactions may lead to changes in bioaccessibility, bioactivity, and bioavailability of phytochemicals. However, our understanding of these interactions between phytochemical and food proteins is limited because of the experimental restrictions. Here, we used pulse-proteolysis to conduct the unfolding equilibrium and dose-dependent experiments on the food proteins for the first time. The interaction between epigallocatechin gallate (EGCG) and caseins was identified in the complicated food matrix, whole milk. Another food proteome, soymilk, was also optimized for identifying the binding targets of EGCG and caffeine. Among the identified interactions, the mixing of milk with coffee generates the most prominent masking effect of 46.61 ± 3.86% relative to the calculated antioxidant capacity. Our results demonstrated that pulse proteolysis is applicable for identifying the interactions between phytochemicals and proteins in the complicated food matrix.

Whipping properties of recombined, additive-free creams

There is increasing industrial interest in the use of the milkfat globule membrane as a food ingredient. The objective of this research was to determine whether the aerosol whipping performance of cream separated into butter and buttermilk, and then recombined, would perform in a manner similar to untreated cream. Churning of cream tempered to different solid fat contents was used to separate butter from buttermilk, which were then recombined at the same ratios as the initial extraction yield, or with 25% extra buttermilk. Differences in milkfat globule size distributions among the recombined creams were apparent; however, their whipping behavior and overrun were similar. Importantly, all recombined creams did not yield properties similar to the original cream, indicating that the unique native milkfat globule membrane structure plays a role in cream performance well beyond its simple presence.

Revisiting the dynamics of proteins during milk powder hydration using asymmetric flow field-flow fractionation (AF4)

The dynamics of β-casein and casein micelles in the reconstitution of skim milk were revisited in this study. β-casein migrates into casein micelles upon an increase in temperatures due to an increase in the hydrophobic effect and lower calcium-phosphate cluster solubility. This process can be reversed upon cooling. These phenomena are well known in fresh milk and are not yet clearly established for reconstituted milk powder. As milk powder is commonly used as a functional ingredient in food products, it is of interest to investigate the migration of casein micelle β-casein to and from the serum phase in reconstituted milk. This study aimed to use asymmetrical flow field flow fractionation (AF4) in combination with various detectors to revisit the dynamics of β-casein when reconstituting skim milk at different temperatures. Fluorescence-labelled β-casein was added to fresh and reconstituted skim milk and rapid transport of β-casein into the outer shell of the casein micelles could be observed already after 5 ​min of reconstitution at 50 ​°C. This process stabilized after approximately 5 ​h, which indicates that an equilibrium of β-casein between the serum and the micellar phase was reached. Similar results were found for fresh milk. The apparent density of the casein micelles in the skim milk samples was also found to increase during reconstitution at 50 ​°C. During cold reconstitution of milk powders, the migration of β-casein to the serum was not observed. The results suggest that β-casein was already present in the serum phase upon reconstitution at 6 ​°C. When a sample was reconstituted for 180 ​min at 50 ​°C, the migration of β-casein back into the serum was observed upon cooling the same sample to 6 ​°C. The size of casein micelles in reconstituted milk at 6 ​°C was larger compared to reconstitution at 50 ​°C. With AF4 and the multi-detector approach, the change in concentration and size of casein micelles can be readily investigated and the migration of β-casein can be tracked simultaneously. Therefore, the method is a valuable tool for studies of the properties and changes in various milk samples.

Depolymerization of chicken egg yolk granules induced by high-intensity ultrasound

The effects of high-intensity ultrasound (HIU) treatment-induced depolymerization of chicken egg yolk granules were investigated. The results showed that the yolk granules were depolymerized after HIU treatment, and the average particle size was significantly reduced from 289.4 nm (untreated) to 181.4 nm (270-W HIU treatment). All contents of dry matter, protein, calcium and phosphorus in the supernatant of the HIU-treated yolk granule solution increased, which suggests that HIU treatment increases the dissolution of yolk granule components. Spectroscopic analysis showed that HIU treatment increased the polarity of the microenvironment and enhanced the hydrogen bond force of yolk granules. These changes induced by HIU treatment collectively enhanced the zeta potential, decreased the free sulfhydryl group content, and slightly improved the emulsifying activity index of yolk granules. The present study reveals the depolymerization effect of HIU treatment on egg yolk granules and can inspire new potential applications of egg yolk granules.

Cow's Milk Processing-Friend or Foe in Food Allergy?

Cow’s milk (CM) is an integral part of our daily diet starting in infancy and continuing throughout our lifetime. Its composition is rich in proteins with a high nutritional value, bioactive components, milk minerals including calcium, and a range of immunoactive substances. However, cow’s milk can also induce a range of immune-mediated diseases including non-IgE-mediated food allergies and IgE-mediated food allergies. Cow’s milk allergens have been identified and characterized and the most relevant ones can be assigned to both, the whey and casein fraction. For preservation a range of processing methods are applied to make cow’s milk and dairy products safe for consumers. However, these methods affect milk components and thus alter the overall immunogenic activity of cow’s milk. This review summarizes the current knowledge on cow’s milk allergens and immunoactive substances and the impact of the different processes up- or downregulating the immunogenicity of the respective proteins. It highlights the gaps of knowledge of the related disease mechanisms and the still unidentified beneficial immunomodulating compounds of cow’s milk.

Functionality of bovine milk proteins and other factors in foaming properties of milk: a review

For many dairy products such as cappuccino-style beverages, the top foam layer determines the overall product quality (e.g. their appearance, texture, mouthfeel and coffee aroma release rate) and the consumer acceptance. Proteins in milk are excellent foaming agents, but the foaming properties of milk are greatly affected by several factors such as the protein content, ratio of caseins to whey proteins, casein micelle size, pH, minerals, proteolysis, presence of low molecular weight compounds (lipids and their hydrolyzed products) and high molecular weight compounds (polysaccharides); milk processing conditions (e.g. homogenization, heat treatment and aging); and foaming method and temperature. These factors either induce changes in the molecular structure, charge and surface activity of the milk proteins; or interfere and/or compete with milk proteins in the formation of highly viscoelastic film to stabilize the foam. Some factors affect the foamability while others determine the foam stability. In this review, functionality of milk proteins in the production and stabilization of liquid foam, under effects of these factors is comprehensively discussed. This will help to control the foaming process of milk on demand for a particular application, which still is difficult and challenging for researchers and the dairy industry.

Chol-Dex nanomicelles: Synthesis, characterization and evaluation as efficient drug carriers for colon targeting

Core-shell structures obtained from amphiphilic molecules on self-assembly in a medium have emerged as an important tool in the area of biomedical sciences. Here, we have synthesized cholesteryl-dextran (Chol-Dex) amphiphiles in sufficiently high yields via conjugation of cholesteryl hemisuccinate to dextran in two different concentrations (5 and 10%). After physicochemical and spectral analysis, the nanomicelles were subjected to size measurements. DLS and TEM confirmed the formation of core-shell type of nanomicelles. Hydrophobic drug-entrapped formulations (Metronidazole and Rifampicin) displayed sustained release behaviour of drugs from them. Sustained release at neutral pH demonstrated usefulness of the non-toxic delivery system for colon specific diseases.