Quality characteristics of goat milk powder produced by freeze drying followed by UV-C radiation sterilization

Goat milk was directly freeze-dried into milk powder after freezing and then sterilized using UV-C radiation to produce low-dose, medium-dose and high-dose UV-C radiation sterilized freeze-dried goat milk powder (LGP, MGP and HGP). UV-C sterilization effectively reduced the total bacteria count and coliform bacteria in the goat milk powder while preserving the active proteins, and maintaining the color unchanged. Additionally, LGP, MGP, and HGP all exhibited a moisture content below 5 g/100 g and water activity below 0.5. Upon reconstitution, the milk powder formed uniform and stable emulsion. During accelerated storage tests, the increased Aw did not compromise the microbial quality of milk powder, and there were no significant changes in active proteins as confirmed via SDS-PAGE results. Furthermore, the color parameters (a*, b* and ΔE) showed a strong correlation with hydroxymethyl furfural levels.

A Gently Processed Skim Milk-Derived Whey Protein Concentrate for Infant Formula: Effects on Gut Development and Immunity in Preterm Pigs

SCOPE

Processing of whey protein concentrate (WPC) for infant formulas may induce protein modifications with severe consequences for preterm newborn development. The study investigates how conventional WPC and a gently processed skim milk-derived WPC (SPC) affect gut and immune development after birth.

METHODS AND RESULTS

Newborn, preterm pigs used as a model of preterm infants were fed formula containing WPC, SPC, extra heat-treated SPC (HT-SPC), or stored HT-SPC (HTS-SPC) for 5 days. SPC contained no protein aggregates and more native lactoferrin, and despite higher Maillard reaction product (MRP) formation, the clinical response and most gut and immune parameters are similar to WPC pigs. SPC feeding negatively impacts intestinal MRP accumulation, mucosa, and bacterial diversity. In contrast, circulating T-cells are decreased and oxidative stress- and inflammation-related genes are upregulated in WPC pigs. Protein aggregation and MRP formation increase in HTS-SPC, leading to reduced antibacterial activity, lactase/maltase ratio, circulating neutrophils, and cytotoxic T-cells besides increased gut MRP accumulation and expression of TNFAIP3.

CONCLUSION

The gently processed SPC has more native protein, but higher MRP levels than WPC, resulting in similar tolerability but subclinical adverse gut effects in preterm pigs. Additional heat treatment and storage further induce MRP formation, gut inflammation, and intestinal mucosal damage.

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.

Lipid oxidation in foods and its implications on proteins

Lipids in foods are sensitive to various environmental conditions. Under light or high temperatures, free radicals could be formed due to lipid oxidation, leading to the formation of unstable food system. Proteins are sensitive to free radicals, which could cause protein oxidation and aggregation. Protein aggregation significantly affects protein physicochemical characteristics and biological functions, such as digestibility, foaming characteristics, and bioavailability, further reducing the edible and storage quality of food. This review provided an overview of lipid oxidation in foods; its implications on protein oxidation; and the assessment methods of lipid oxidation, protein oxidation, and protein aggregation. Protein functions before and after aggregation in foods were compared, and a discussion for future research on lipid or protein oxidation in foods was presented.

The cysteine residue in beta-lactoglobulin reacts with oxidized tyrosine residues in beta-casein to give casein-lactoglobulin dimers

Proteins are modified during milk processing and storage, with sidechain oxidation and crosslinking being major consequences. Despite the prevalence and importance of proteins in milk, and particularly caseins (∼80% of total content), the nature of the cross-links formed by oxidation, and their mechanisms of formation, are poorly characterized. In this study, we investigated the formation and stability of cross-links generated by the nucleophilic addition of Cys residues to quinones generated on oxidation of Tyr residues. The mechanisms and stability of these adducts was explored using ubiquitin as a model protein, and β-casein. Ubiquitin and β-casein were oxidized using a rose Bengal/visible light/O₂ system, or by the enzyme tyrosinase. The oxidized proteins were incubated with glutathione or β-lactoglobulin (non-oxidized, but unfolded by treatment at 70 °C), before analysis by SDS-PAGE, immunoblotting and LC-MS. Our data indicate that Cys-quinone adducts are readily-formed, and are stable for >48 h. Thus, oxidized β-casein reacts efficiently with the thermally unfolded β-lactoglobulin, likely via Michael addition of the exposed Cys to a Tyr-derived quinone. These data provide a novel, and possibly general, mechanism of protein cross-link formation, and provides information of the stability of these species that have potential as markers of protein quality.

Detection of protein oxidation products by fluorescence spectroscopy and trilinear data decomposition: Proof of concept

Current analytical methods studying protein oxidation modifications require laborious sample preparation and chromatographic methods. Fluorescence spectroscopy is an alternative, as many protein oxidation products are fluorescent. However, the complexity of the signal causes misinterpretation and quantification errors if single emission spectra are used. Here, we analyzed the entire fluorescence excitation-emission matrix using the trilinear decomposition method parallel factor analysis (PARAFAC). Two sample sets were used: a calibration set based on known mixtures of tryptophan, tyrosine, and four oxidation products, and a second sample set of oxidized protein solutions containing UV-illuminated β-lactoglobulin. The PARAFAC model succeeded in resolving the signals of the model systems into the pure fluorophore components and estimating their concentrations. The estimated concentrations for the illuminated β-lactoglobulin samples were validated by liquid chromatography-mass spectrometry. Our approach is a promising tool for reliable identification and quantification of fluorescent protein oxidation products, even in a complex protein system.

Alternatives to Cow’s Milk-Based Infant Formulas in the Prevention and Management of Cow’s Milk Allergy

Cow’s milk-based infant formulas are the most common substitute to mother’s milk in infancy when breastfeeding is impossible or insufficient, as cow’s milk is a globally available source of mammalian proteins with high nutritional value. However, cow’s milk allergy (CMA) is the most prevalent type of food allergy among infants, affecting up to 3.8% of small children. Hypoallergenic infant formulas based on hydrolysed cow’s milk proteins are commercially available for the management of CMA. Yet, there is a growing demand for more options for infant feeding, both in general but especially for the prevention and management of CMA. Milk from other mammalian sources than the cow, such as goat, sheep, camel, donkey, and horse, has received some attention in the last decade due to the different protein composition profile and protein amino acid sequences, resulting in a potentially low cross-reactivity with cow’s milk proteins. Recently, proteins from plant sources, such as potato, lentil, chickpeas, quinoa, in addition to soy and rice, have gained increased interest due to their climate friendly and vegan status as well as potential lower allergenicity. In this review, we provide an overview of current and potential future infant formulas and their relevance in CMA prevention and management.

Health Effects of Dietary Oxidized Milk Administration in Offspring Mice during Pregnancy and Lactation with Metabolomic Strategies

Milk is an important source of nutrients during pregnancy. Previous studies have consistently shown that oxidation in milk and dairy products can induce oxidative stress, inflammation, and fibrosis in the liver and kidney. However, the mechanism underlying these effects remains largely unexplored. This study aimed to investigate the effects of oxidized milk on fecal metabolism and liver and kidney function of offspring mice. Oxidative modification of milk was performed using H₂O₂-Cu or heating, causing varying degrees of oxidative damage. Kunming female mice were fed with a H₂O₂-Cu, heat, or normal control diet until their offspring were 3 weeks old. Feces were collected for the metabolomics study based on mass spectrometry. Forty-two potentially significant metabolic biomarkers were screened, and each group's relative intensity was compared. The results showed that oxidized milk mainly regulated isoleucine metabolism, proline metabolism, and tricarboxylic acid cycle. In addition, the histopathological analysis showed accumulation of protein and lipid oxidation products in the liver and kidney tissues after intake of oxidized milk, which induced oxidative stress, increased the levels of inflammatory factors, and significantly increased the expression of genes and proteins involved in inflammatory pathways. The above results suggest that intake of oxidized milk during gestation may increase the risk of liver and kidney injury in male offspring by interfering with amino acid and energy metabolism, highlighting the potential health risks of oxidized milk in humans.

Lycopene Regulates Dietary Dityrosine-Induced Mitochondrial-Lipid Homeostasis by Increasing Mitochondrial Complex Activity

SCOPE

Dityrosine (DT), a marker of protein oxidation, is widely found in many high-protein foods. Dietary intake of DT induces myocardial oxidative stress injury and impairs energy metabolism. Lycopene is a common dietary supplement with antioxidant and mitochondrial-lipid homeostasis modulating abilities. This study aimed to examine the effects of lycopene on DT-induced disturbances in myocardial function and energy metabolism.

METHODS AND RESULTS

Four-week-old C57BL/6J mice received intragastric administration of either tyrosine (420 µg kg^-1 BW), DT (420 µg kg^-1 BW), or lycopene at high (10 mg kg^-1 BW) and low (5 mg kg^-1 BW) doses for 35 days. Lycopene administration effectively reduced oxidative stress, cardiac fatty acid accumulation, and cardiac hypertrophy and improved mitochondrial performance in DT-induced mice. In vitro experiments in H9c2 cells showed that DT directly inhibited the activity of the respiratory chain complex, whereas oxidative phosphorylation and β-oxidation gene expression is upregulated. Lycopene enhanced the activity of the complexes and inhibited ROS production caused by compensatory regulation.

CONCLUSION

Lycopene improves DT-mediated myocardial energy homeostasis disorder by promoting the activity of respiratory chain complexes I and IV and alleviates the accumulation of cardiac fatty acids and myocardial hypertrophy.

Oxidized Milk Induces Spatial Learning and Memory Impairment by Altering Gut Microbiota in Offspring Mice during Pregnancy and Lactation

Early adverse diet exposures are known to be associated with increased risk of learning and memory injury in offspring, yet whether oxidized milk is involved in such an effect has been largely unknown. Here, we focused on oxidized milk intake in mice during pregnancy and lactation to measure the changes in the learning and memory ability in offspring and also probed into the relevant association with gut microbiota. Milk was oxidized with H₂O₂-Cu or HClO, resulting in different degrees of oxidative damage. KM female mice were fed H₂O₂-Cu, HClO, or normal control diets immediately after caging until their offspring were 3-weeks old. Behavioral tests were then performed to test the learning and memory ability, and 16S rRNA sequencing was completed with harvested fecal contents. As analyzed, fecal microflora in mice with oxidized milk was affected, mainly reflected in decreased mucin-degrading bacteria, Akkermansia and Lactobacillus, and in reversely increased pro-inflammatory bacteria Shigella, pathobiont Mucispirillum, nervous associated bacteria Ruminococcus, Escherichia, and Desulfovibrio. In the meantime, the inflammation developed in mice was aggravated accompanied by increased expression of relevant genes, while the genes and proteins associated with the learning and memory ability were down-regulated. Further behavioral tests proved impairment of the learning and memory ability in offspring. In general, milk of oxidative damage is a risk factor of the impaired transgenerational ability in learning and memory, which is associated with gut microbiota and intestinal mucosa conditions. This finding may help support the potential of early adverse diet as a harmful factor in learning and memory.

Analysis of Protein Oxidation in Food and Feed Products

Food and feed proteins are subject to oxidation reactions during production, processing, and storage. Several individual oxidized amino acids have been described in model systems and food; however, protein oxidation in food is still mostly assessed by the analysis of protein carbonylation. In the present review, the chemistry of protein oxidation and its implications for protein functionality, food flavor, and nutritional physiology are briefly summarized. Limitations of generic methods targeting redox-relevant functional groups and properties of typical reaction products, such as the determination of protein carbonyls and fluorescence spectroscopy, are presented. Methods for the quantitation of individual oxidation products of susceptible amino acids, such as cysteine, methionine, phenylalanine, tyrosine, and tryptophan, are reported. Special regard is paid to limitations resulting from the required hydrolysis procedures and unintended formation of the analytes during sample pretreatment. If available, results from food analysis obtained by different methods are compared. Suggestions and requirements for future works on protein oxidation in food and nutrition are given.

Dietary Dityrosine Induces Mitochondrial Dysfunction by Diminished Thyroid Hormone Function in Mouse Myocardia

Oxidized tyrosine products (OTP) have been detected in commercial foods with high protein content, such as meat and milk products. OTP intake induces tissue oxidative stress and affects the normal activity of the hypothalamic-pituitary-thyroid axis (HPT). This study aims to investigate the effects of OTP and their main product, dityrosine (Dityr), on mouse myocardial function and myocardial energy metabolism. Mice received daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), Dityr (420 μg/kg body weight), or OTP (1909 μg/kg body weight) for 35 days. Additionally, H9c2 cells were incubated with various concentrations of Dityr for 72 h. We found that OTP and pure Dityr induced oxidative stress in growing mice and in H9c2 cells, resulting in a redox state imbalance, myocardial injury, mitochondrial dysfunction, and energy metabolism disorder. Dityr interferes with T3 regulation of the myocardium via the PI3K/AKT/GSK3β pathway, leading to myocardial mitochondrial damage and energy metabolism disorders. Food-borne OTP, especially Dityr, can disrupt thyroid hormone function in mouse myocardia leading to mitochondrial dysfunction, energy metabolism disorder, and oxidative stress.

Study of Polyphenol Content and Antioxidant Properties of Various Mix of Chocolate Milk Masses with Different Protein Content

The aim of the study was to analyze the antioxidant character of conched chocolate milk masses, taking into account different protein content in milk. For the study, cocoa liquor obtained from roasted and unroasted cocoa beans from different regions, as well as milk powder obtained by spray and cylindrical drying were used. The analysis that was carried out showed that the protein content of powdered milk products ranged from about 11.6% (w/w) to over 31% (w/w). Lower content of polyphenols and lower antioxidant activity were shown in the masses to which the addition of milk with higher protein content was applied. The analysis of antioxidant character of chocolate milk masses showed higher total polyphenols content in masses prepared from unroasted cocoa beans liquor.

Comparison of Oxidative Status of Human Milk, Human Milk Fortifiers and Preterm Infant Formulas

Preterm and low birth weight infants require specific nutrition to overcome the accumulated growth deficit, and to prevent morbidities related to postnatal growth failure. In order to guarantee an adequate nutrient-intake, mother’s own milk, when available, or donor human milk, are usually fortified with additional nutrients, in particular proteins. Fortification with processed ingredients may result in additional intake in oxidative compounds, deriving from extensive heat treatments, that are applied during processing. The aim of the present work was to compare the in vitro antioxidant activity and oxidative compound content conveyed by different preterm infant foods and fortifiers, namely raw and pasteurized human milk, two different preterm infant formulas, three bovine milk-based fortifiers and two experimental donkey milk-based fortifiers. Univariate and multivariate statistical analyses revealed significant differences between the different products. The use of human milk minimizes the intake of dietary oxidative compound in comparison to infant formulas, irrespective of pasteurization or fortification, especially as far as malondialdehyde content is concerned. The addition of fortifiers to human milk increases its antioxidant capacity, and the choice of the protein source (hydrolysed vs. whole proteins) differently impacted the resulting total antioxidant capacity of the diet.

Whey proteins: targets of oxidation, or mediators of redox protection

Bovine whey proteins are highly valued dairy ingredients. This is primarily due to their amino acid content, digestibility, bioactivities and their processing characteristics. One of the reported bioactivities of whey proteins is antioxidant activity. Numerous dietary intervention trials with humans and animals indicate that consumption of whey products can modulate redox biomarkers to reduce oxidative stress. This bioactivity has in part been assigned to whey peptides using a range of biochemical or cellular assays in vitro. Superimposing whey peptide sequences from gastrointestinal samples, with whey peptides proven to be antioxidant in vitro, allows us to propose peptides from whey likely to exhibit antioxidant activity in the diet. However, whey proteins themselves are targets of oxidation during processing particularly when exposed to high thermal loads and/or extensive processing (e.g. infant formula manufacture). Oxidative damage of whey proteins can be selective with regard to the residues that are modified and are associated with the degree of protein unfolding, with α-Lactalbumin more susceptible than β-Lactoglobulin. Such oxidative damage may have adverse effects on human health. This review summarises how whey proteins can modulate cellular redox pathways and conversely how whey proteins can be oxidised during processing. Given the extensive processing steps that whey proteins are often subjected to, we conclude that oxidation during processing is likely to compromise the positive health attributes associated with whey proteins.

Spatial Learning and Memory Impairment in Growing Mice Induced by Major Oxidized Tyrosine Product Dityrosine

This study focused on the effects of oxidized tyrosine products (OTPs) and major component dityrosine (DT) on the brain and behavior of growing mice. Male and female mice were treated with daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), DT (420 μg/kg body weight), or OTPs (1909 μg/kg body weight) for 35 days. We found that pure DT and OTPs caused redox state imbalance, elevated levels of inflammatory factors, hippocampal oxidative damage, and neurotransmitter disorders while activating the mitochondrial apoptosis pathway in the hippocampus and downregulating the genes associated with learning and memory. These events eventually led to growing mice learning and memory impairment, lagging responses, and anxiety-like behaviors. Furthermore, the male mice exhibited slightly more oxidative damage than the females. These findings imply that contemporary diets and food-processing strategies of the modern world should be modified to reduce oxidized protein intake.

The Chemistry of Protein Oxidation in Food

Oxidation is one of the deterioration reactions of proteins in food, the importance of which is comparable to others such as Maillard, lipation, or protein-phenol reactions. While research on protein oxidation has led to a precise understanding of the processes and consequences in physiological systems, knowledge about the specific effects of protein oxidation in food or the role of "oxidized" dietary protein for the human body is comparatively scarce. Food protein oxidation can occur during the whole processing axis, from primary production to intestinal digestion. The present review summarizes the current knowledge and mechanisms of food protein oxidation from a chemical, technological, and nutritional-physiological viewpoint and gives a comprehensive classification of the individual reactions. Different analytical approaches are compared, and the relationship between oxidation of food proteins and oxidative stress in vivo is critically evaluated.

Effects of Protein-Derived Amino Acid Modification Products Present in Infant Formula on Metabolic Function, Oxidative Stress, and Intestinal Permeability in Cell Models

Proteins present in infant formulas are modified by oxidation and glycation during processing. Modified amino acid residues released from proteins may be absorbed in the gastrointestinal tract, and pose a health risk to infants. In this study, the markers of glycation furosine (1.7-3.5 μg per milligram of protein) and N^ε-(carboxymethyl)lysine (28-81 ng per milligram of protein) were quantitated in infant formulas. The effects of these species, and other amino acid modifications, at the levels detected in infant formulas, on 3T3-L1 (murine preadipocyte) and Caco-2 (human intestinal epithelial) cells were assessed. Incubation of 3T3-L1 cells for 48 h with amino acid side chain oxidation and glycation products (1 and 10 μM) resulted in a loss (up to 40%, p < 0.05) of cell thiols and decreased metabolic activity compared with those of the controls. In contrast, Caco-2 cells showed a stimulation (10-50%, p < 0.05) of cellular metabolism on exposure to these products for 24 or 48 h. A 28% ( p < 0.05) increase in protein carbonyls was detected upon incubation with 200 μM modified amino acids for 48 h, although no alteration in transepithelial electrical resistance was detected. Oxidation products were detected in the basolateral compartments of Caco-2 monolayers when modified amino acids were applied to the apical side, consistent with limited permeability (up to 3.4%) across the monolayer. These data indicate that modified amino acids present in infant formulas can induce effects on different cell types, with evidence of bioavailability and induction of cellular stress. This may lead to potential health risks for infants consistently exposed to high levels of infant formulas.

Effect of quality of milk on maillard reaction and protein oxidation during preparation of cow and buffalo milk khoa

The browning indicators (Lactulose, HMF and Furosine) and protein bound carbonyls were used to assess the effect of developed acidity and subsequent neutralization of milk at various stages of khoa (heat desiccated milk product) preparation. Available lysine was also analyzed in raw milk and final product i.e. khoa. Available lysine decreased as milk progressed to khoa preparation. Present study indicated that increase in heating intensity resulted in increased concentration of browning indicators and protein bound carbonyls (PC) in boiled milk and khoa. Concentration of browning indicators was found to be significantly higher in buffalo milk and khoa samples whereas, PCconc. was higher in cow milk and khoa samples. Neutralization of milk significantly affected Maillard reaction by elevating concentration of browning indicators and PC in both milk and khoa.

Effect of 2,2-azobis (2-amidinopropane) dihydrochloride oxidized casein on the microstructure and microrheology properties of emulsions

The impacts of protein oxidation on the droplet size and microrheology properties of casein emulsions with 20% oil content were investigated. The degree of protein oxidation was indicated by carbonyl concentration. The droplets in the emulsions of different-oxidation-degree casein had bimodal distribution, but their size altered due to oxidation. The effects of protein oxidation on the morphology, motion type, viscoelasticity, and stability of droplets were also investigated by microrheology analysis. The droplet motion was blocked by protein oxidation due to mean square displacement slope results. Solid-liquid balance values provided the liquid behavior dominating these emulsions. Oxidation of carbonyl concentration 16.72 raised the primary droplets, increased the elasticity, decreased the viscosity, and promoted the droplet motion rate, resulting in better stability of emulsions. Further oxidation promoted the aggregation of droplets and resulted in poor stability.

Methionine sulfoxide profiling of milk proteins to assess the influence of lipids on protein oxidation in milk

Methionine sulfoxide profiling revealed that protein oxidation in milk and milk products is not promoted by lipids.