Changes in bioactive milk serum proteins during milk powder processing

Thermal stability and in vitro biological fate of lactoferrin-polysaccharide complexes

Lactoferrin (LF) is a thermally sensitive iron-binding globular glycoprotein. Heat treatment can induce its denaturation and aggregation and thus affect its functional activity. In this study, carrageenan (CG), xanthan gum (XG) and locust bean gum (LBG), allowed to apply in infant food, were used to form protein-polysaccharide complexes to improve the thermal stability of LF. Meanwhile, in vitro simulated infant digestion and absorption properties of LF were also estimated. The results showed that the complexes formed by CG and XG with LF (LF-CG and LF-XG) could significantly inhibit the loss of α-helix structure of LF against heating. LF-CG and LF-LBG could protect LF from digestion in simulated infant gastric fluid and slow down the degradation of LF under the simulated intestinal conditions. Besides, LF, LF-CG and LF-XG showed no adverse effects on the growth of Caco-2 cells in the LF concentration range of 10-300 μg/mL, and LF-XG exhibited better beneficial to improve the cell uptake of the digestive product than the other protein-polysaccharides at the LF concentration of 100 µg/mL. This study may provide a reference for the enhancement of thermal processing stability of LF and development infant food ingredient with high nutrients absorption efficiency in the gastrointestinal environment in the future.

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.

Site-specific glycoproteomic analysis of purified lactoferrin from human and animal milk

Lactoferrin is a highly glycosylated protein, which have important biological functions in the growth and development of neonates. However, the glycoforms and glycosylation sites differed between species. The aim of the study was to identify the glycosylation profile (including glycosites, glycan structures, and glycoforms) of purified lactoferrin from human and animal (cow, goat, sheep) milk by using site-specific glycoproteomics technique. In total, a number of 89 N-glycans were identified in human and animal milk lactoferrin. We identified three N-glycosites with 23 different compositions of N-glycans in cow lactoferrin (CLF), four distinctive N-glycosites with 34 dissimilar N-glycan compositions in goat lactoferrin (GLF), five N-glycosites with 57 different N-glycan compositions in sheep lactoferrin (SLF), while five unique N-glycosites with 50 different N-glycan compositions were ascertained in human lactoferrin (HLF). HLF had the most complex glycan, while animal lactoferrin had the most high-mannose glycoforms. The results of this study further our understanding of lactoferrin differences between human and animal milk, which can provide a perspective on the analysis of differences in functional characteristics.

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.

Colostrum Composition, Characteristics and Management for Buffalo Calves: A Review

In this review, the composition, characteristics, and management of dairy buffalo calves were examined and compared with bovines. The neonatal period is critical for buffalo calves and is characterized by a high mortality rate (more than 40%). The early intake of high-quality colostrum (IgG > 50 mg/mL) is the one way to improve the immune system of calves (serum IgG > 10 mg/mL after 12 h), thus increasing their chances of survival. Mainly in intensive farms, the availability of high-quality colostrum is necessary; thus, good quality colostrum is often stored to provide newborn calves which cannot be fed by their mothers. Also, the manipulation of the immunological status of animals through vaccination has been depicted since the quality of colostrum tended to be influenced by vaccination against pathogens. Buffalo breeding is constantly expanding in Italy, mainly thanks to the Mozzarella cheese production that represents the excellence of the "Made in Italy" and is exported worldwide. Indeed, high calf mortality rates directly affect the profitability of the business. For these reasons, the aim of this review was to examine specific research on buffalo colostrum that, compared with other species, are scarce. Improving the knowledge of buffalo colostrum, in terms of characteristics and management, is critical to guarantee buffalo newborns' health in order to reduce their mortality rate. Importantly, considering the knowledge on cattle valid also for buffalo is a widespread, and often erroneous, habit in several fields, including colostrum feeding. Therefore, the two species were compared in this review.

Quantitative Phosphoproteome of Infant Formula: New Insights into the Difference of Phosphorylation in Milk Proteins between Bovine and Goat Species

Phosphorylation is a broad post-translational protein modification, and the level of phosphorylation of milk proteins is associated with lactation, coagulation properties, and digestibility. However, phosphoproteins in bovine milk-based and goat milk-based infant formula have not been systematically explored. Here, we have analyzed six bovine and six goat milk-based infant formula using a quantitative phosphoproteomics approach, from which we identified 200 phosphoproteins with 276 phosphorylation sites and 156 phosphorylation sites from 75 phosphoproteins, respectively. Of these, 99 phosphorylation sites from 26 shared phosphoproteins were differentially expressed between bovine and goat milk-based infant formula. Especially, CSN1S1 was the most phosphoprotein with 25 quantified phosphorylation sites. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that the identified phosphoproteins not only provide nutrition to the infant but also have anti-inflammatory, antipathogenic, and other biological functions. Our results shed light on the composition, phosphorylation sites, and biological functions of phosphoproteins in bovine milk and goat milk-based infant formula, which provide new insights into the key role of protein modifications during infant development. It also helps us to better understand the differences in digestibility of infant formula from different animal milk sources and thus guides the choice of milk source for infant formula.

The application of lactoferrin in infant formula: The past, present and future

Human milk is universally regarded as the gold standard to fulfill nutrition needs of infants. Lactoferrin (LF) is a major multiple bioactive glycoprotein in human milk but little is presented in infant formula. LF can resist digestion in the infant gastrointestinal tract and is absorbed into the bloodstream in an intact form to perform physiological functions. Evidence suggest that LF prevents pathogen infection, promotes immune system development, intestinal development, brain development and bone health, as well as ameliorates iron deficiency anemia. However, more clinical studies of LF need to be further elucidated to determine an appropriate dosage for application in infant formula. LF is sensitive to denaturation induced by processing of infant formula such as heat treatments and spay drying. Thus, further studies should be focus on maximizing the retention of LF activity in the infant formula process. This review summarizes the structural features of LF. Then the digestion, absorption and metabolism of LF in infants are discussed, followed by the function of LF for infants. Further, we summarize LF in infant formula and effects of processing of infant formula on bioactivities of LF, as well as future perspectives of LF research.

Choice Experiment Assessment of Consumer Preferences for Yogurt Products Attributes: Evidence from Taiwan

Previous studies on consumer yogurt preferences have mainly focused on added sugar, nutrient content, and health claims, leaving several knowledge gaps that should be filled through in-depth research. In this study, a more complete multi-attribute preference model was developed using the number of probiotic types, type of milk source, presence of edible gels (GEL), and usage of health food labels as the main yogurt attributes. A choice experiment (CE) was then conducted to investigate the relationship between multiple attribute preferences and willingness-to-pay (WTP). A total of 435 valid questionnaires were collected by the convenience sampling method. The results show that (1) respondents highly value the health food label (HEA), followed by the number of probiotic types (PRO); (2) the highest WTP in the conditional logit (CL) model was New Taiwan Dollar (NTD) (USD 10.5 for HEA, and the lowest was NTD 1.0 for 100% milk powder (MLK2); (3) in the random-parameter logit (RPL) model, the highest WTP was NTD 14.6 for HEA, and the lowest was NTD 2.8 for GEL; (4) the most preferred attribute combination of yogurt was “8 or more probiotic types”, “a blend of raw milk and milk powder”, “the absence of edible gels”, “the presence of a health food label”, and “a price premium of NTD 6–10”; (5) married respondents with children were more willing to pay extra for yogurt products with a higher number of probiotic types and a health food label. The results may help the food industry understand and pay attention to consumer needs, which will, in turn, provide a reference for future product development and marketing strategies.

Effects of Drying Methods on Serum Protein Powder Properties

This study investigated the effects of atmospheric spray drying (ASD), low-pressure spray drying (LPSD) and freeze drying (FD) on the properties of serum protein powder, including the basic characteristics of the powder, bioactive proteins and changes in protein profile, using a proteomics approach. The total solid and water activity of the powder obtained by FD was significantly higher than that obtained by ASD and LPSD. There was no significant difference in the content of fat, lactose or solubility between the three kinds of powders. The concentration and activity of the proteins/enzymes in the serum protein powder made from LPSD were not altered after drying, similar to FD, although both parameters decreased after ASD. The microstructure of the powder observed by scanning electron microscopy indicated that the powder manufactured by ASD and LPSD was spherical in structure, while that manufactured by FD was flake-like. In total, there were 245 proteins identified in the serum protein concentrate and powder from the three drying methods. These findings indicate that LPSD is an effective and cost-saving method for producing serum whey protein powder.

Effect of biofilm on the survival of Staphylococcus aureus isolated from raw milk in high temperature and drying environment

Microbial contamination in dairy products is a momentous factor affecting food safety. Studies have shown that Staphylococcus aureus, which is an important causative agent of a range of infectious and foodborne diseases, may remain in raw milk after a series of complex processing processes. Although most S. aureus possess biofilm formation capacity, there are few studies concerning the role of biofilm formation of this bacterium in stress tolerance and longtime survival in the dairy products. In this study, we selected 5 S. aureus (RMSA1, RMSA2, RMSA3, RMSA4 and RMSA5) isolates from raw milk and investigated their virulence and biofilm characteristics. Results from biofilm assays showed that all 6 S. aureus strains (5 dairy isolates and 1 human-derived model strain NCTC8325) could form complete biofilms in vitro. The reverse transcription-PCR experiments confirmed that multiple genes related to virulence factors and biofilm formation were expressed in the 6 strains. Furthermore, we simulated the high temperature (at 60 °C for 30 min) and drying pressure (at 37 °C for 24 h) during dairy processing to detect the survival rate of strains culturedunderbiofilm or planktonic condition. The data showed that under high temperature and dry conditions, the survival rates of strains cultured under biofilm conditions were much higher than that of strains cultured under planktonic conditions. In addition, the adversity resistance associated with biofilm formation was more obvious in the milk-isolated strains compared with strain NCTC8325. This study provides evidence regarding the mechanisms of stress resistance of S. aureus strains isolated from raw milk and contribute to prevention of dairy product contamination caused by this bacterium.

Proteomic analysis of differentially expressed whey proteins in Saanen goat milk from different provinces in China using a data-independent acquisition technique

Whey proteins of Saanen goat milk samples from 3 provinces in China (Guangdong, GD; Inner Mongolia, IM; Shaanxi, SX) were characterized and compared using data-independent acquisition quantitative proteomics technique. A total of 550 proteins were quantified in all 3 samples. There were 44, 44, and 33 differentially expressed proteins (DEP) for GD versus IM, GD versus SX, and IM versus SX, respectively. Gene ontology annotation analysis showed that the largest number of DEP for the 3 comparisons were as follows: for biological processes: response to progesterone, glyceraldehyde-3-phosphate metabolic process, and negative regulation of megakaryocyte differentiation; for molecular functions: antioxidant activity, binding, and peroxiredoxin activity; and for cellular components: the same category of extracellular regions for the 3 comparisons, respectively. Pathways for the DEP of 3 comparisons were (1) disease; (2) synthesis and metabolism; and (3) synthesis, degradation, and metabolism. Protein-protein interaction network analysis showed that DEP for GD versus SX had the most interactions.

Potential Benefits of Bovine Colostrum in Pediatric Nutrition and Health

Bovine colostrum (BC), the first milk produced from cows after parturition, is increasingly used as a nutritional supplement to promote gut function and health in other species, including humans. The high levels of whey and casein proteins, immunoglobulins (Igs), and other milk bioactives in BC are adapted to meet the needs of newborn calves. However, BC supplementation may improve health outcomes across other species, especially when immune and gut functions are immature in early life. We provide a review of BC composition and its effects in infants and children in health and selected diseases (diarrhea, infection, growth-failure, preterm birth, necrotizing enterocolitis (NEC), short-bowel syndrome, and mucositis). Human trials and animal studies (mainly in piglets) are reviewed to assess the scientific evidence of whether BC is a safe and effective antimicrobial and immunomodulatory nutritional supplement that reduces clinical complications related to preterm birth, infections, and gut disorders. Studies in infants and animals suggest that BC should be supplemented at an optimal age, time, and level to be both safe and effective. Exclusive BC feeding is not recommended for infants because of nutritional imbalances relative to human milk. On the other hand, adverse effects, including allergies and intolerance, appear unlikely when BC is provided as a supplement within normal nutrition guidelines for infants and children. Larger clinical trials in infant populations are needed to provide more evidence of health benefits when patients are supplemented with BC in addition to human milk or formula. Igs and other bioactive factors in BC may work in synergy, making it critical to preserve bioactivity with gentle processing and pasteurization methods. BC has the potential to become a safe and effective nutritional supplement for several pediatric subpopulations.

Dose escalation study of bovine lactoferrin in preterm infants: getting the dose right

Lactoferrin as a nutritional enteral supplement has emerged as a novel preventative therapy against serious infections in preterm infants, although neonatal studies have demonstrated variable results, in part due to the lack of pharmacokinetic data and differences in the products tested. We conducted a prospective, dose escalation (100, 200, and 300 mg·kg–1·day–1) safety study of bovine lactoferrin (Glanbia Nutritionals, USA) dissolved in sterile water (100 mg·mL–1) for 30 days in preterm infants with birth weight <1500 g. Safety related to adverse events (AEs), tolerability, and exposure-response of lactoferrin was assessed. We enrolled 31 patients [10, 10, and 11 patients, for the lactoferrin treatment groups (100, 200, and 300 mg·kg–1·day–1, respectively)] over a 10-month period. No AEs related to the study solution occurred, and lactoferrin was tolerated by each group. During lactoferrin supplementation, one bloodstream infection occurred in each group, but there were no incidences of urinary tract infections and no cases of necrotizing enterocolitis. Postnatal cytomegalovirus acquisition was detected in the group treated with 200 mg·kg–1·day–1 (n = 2). There were no adverse effects on hepatic, renal, or hematologic function. All of the patients survived to discharge. Bovine lactoferrin at doses up to 300 mg·kg–1·day–1 is safe in preterm infants. Future studies examining higher doses of lactoferrin, length of treatment, and potency of different products will aid in determining the optimal approach for the use of lactoferrin to prevent infections in preterm infants.

A sensitive and high-throughput fluorescent method for determination of oxidase activities in human, bovine, goat and camel milk

Milk oxidases are an integral part of milk immune system, and good indicators for milk thermal history. Current assay methods for milk oxidases are either insensitive, tedious or not cost-effective. In this study, a high-throughput fluorescence assay method for determination of xanthine oxidase (XO) and polyamine oxidase (PAO) activities in milk samples was developed. The hydrogen peroxide generated by XO catalysed oxidation of hypoxanthine, and PAO catalysed oxidation of spermine, was coupled to horseradish peroxidase conversion of Amplex® Red (1-(3,7-dihydroxyphenoxazin-10-yl)ethanone) to the fluorescent product resorufin. The assay was highly sensitive, with limits of detection of activity in milk being 3 × 10^-7 and 7 × 10^-7 U/mL for XO and PAO, respectively. Intra-run and inter-run results showed good assay repeatability and reproducibility. The assay was successfully applied to survey the XO and PAO activities in human, bovine, goat and camel milk samples, and it can be readily adapted for measurements of other oxidase activities.