Two pasteurization steps are often used in the preparation of whey protein concentrate (WPC) before evaporation into a dry product. The Pasteurized Milk Ordinance in the United States requires that raw bovine milk be pasteurized using a process that meets minimum heat treatment requirements to achieve reductions in pertinent microorganisms. In addition, WPC produced from USDA-approved plants must comply with CFR subpart B 58.809, which dictates that all fluid whey used in the manufacture of dry whey products shall be pasteurized before being condensed. These heat treatments are effective at inactivating the most thermally resistant bacterium, such as Coxiella burnetii; however, they can also alter milk proteins, inducing denaturation, aggregation, and reduced bioactivity. Though the impact of thermal treatments on whey proteins has been examined, the specific influence of 2 HTST pasteurization steps on the retention of proteins in WPC remains unknown. This study aimed to investigate the effect of commercial-scale HTST pasteurization of both raw milk and the resulting sweet whey on the products' overall protein profile. We analyzed 3 distinct batches of raw milk (RM) and the corresponding pasteurized milk (PM), resulting whey (RW), and pasteurized whey (PW) produced at commercial scale. Assessments of denaturation were conducted through solubility testing at pH 4.6 and hydrophobicity evaluation via anilinonaphthalene-1-sulfonic acid assay. Additionally, ELISA, PAGE, and liquid chromatography tandem MS (LC-MS/MS) were employed to compare the retention of key bioactive proteins before and after each HTST pasteurization step. The percentage of soluble whey protein decreased from RM to PM and from RW to PW, but no significant differences were observed via hydrophobicity assay. The ELISA revealed a significant reduction in key bioactive proteins, such as lactoferrin, IgA, and IgM, but not IgG, after HTST pasteurization of RM and RW. The PAGE and LC-MS/MS results revealed a significant decrease in the retention of lactoferrin and key milk fat globular membrane proteins, such as xanthine dehydrogenase oxidase/xanthine oxidase, lactadherin, and fatty acid binding protein. Additionally, xanthine oxidase activity was significantly reduced after HTST pasteurization of milk and whey. This research helps to identify the limitations of the current processing techniques used in the dairy industry and could lead to innovation in improving the retention of bioactive proteins.

In the fight against fermentation-disrupting bacteriophages, UV-C irradiation is promising due to its capability of damaging nucleic acids and preventing organisms to replicate. The purpose of this study is to investigate the effect of this radiation on whey using three different devices (lab-/technical-scale, batch/continuous) and UV-C doses between 0.4 and 100 J mL-1. In vitro toxicity assays (Comet, WST-1, Ames) proved that irradiated whey does not exhibit any genotoxic, cytotoxic, or mutagenic activity and is presumed to be harmless to health. However, the irradiated product had an intense "cowish/ stable-like/manure-like" off-flavor, which was identified as para-cresol by GC-MS-O. Riboflavin decay was observed as well as decreases in cystine and aromatic amino acids, whose degradation products are known to be odor-active. With our current data, we are not able to define a suitable process window or to recommend the application of this technology to treat whey. (c) 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In this study, possible reasons for an increased level of free fatty acids (FFA) in UHT-treated full-fat (3.5% wt/wt) milk and its effect on the frothing properties of milk were investigated. Lipolysis of raw milk from 2 different breeds of cattle (Holstein and Jersey) was induced by mechanical stress and kinetics of lipolysis were compared. Frothing capacity and foam stability of shelf-stable milk with different concentrations of FFA were determined, with a good to medium initial foam volume for up to 4 mEq FFA·(100 g of fat)-1 fat and poor foam stability with >2 mEq FFA·(100 g of fat)-1. A combination of mechanical stress and initial condition of fresh raw milk was found to trigger lipolysis and potential sources of mechanical stress during milk processing were identified.

The techno-functional properties of dairy cheeses are often superior to their plant-based cheese alternatives. However, the constant increase in demand for plant- based cheese alternatives makes it important to achieve texture and functionality as in dairy cheeses. In this study commercial dairy cheeses and plant-based cheese alternatives were analyzed in regard to chemical composition, texture properties (unheated and heated state) and melting behavior with methods commonly applied to dairy cheeses. Especially, during an oscillatory temperature sweep, data did not show the "melting" the consumer notices while baking the product in an oven as done in the Schreiber test (2_CA, 3_CA). Therefore, a large amplitude oscillatory strain method (LAOS 60 degrees C) was applied and linked with the results obtained from the Schreiber test and the temperature sweep measurements. LAOS not only showed good correlation with the melting behavior observed in the Schreiber test but also allowed conclusions about the microstructure of the samples.

Whey protein concentrate (WPC) is consumed for its high protein content. The structure and biological functionality of whey proteins in WPC powders may be affected by the drying technique applied. However, the specific impact of spray drying and freeze drying on the overall protein profile of whey protein derived from sweet whey streams at scale is unknown. Herein, we examine the effects of commercial-scale freeze drying and spray drying on WPC to determine which method better preserves bioactive whey proteins, with the goal of helping the dairy industry create high-value products that meet the growing consumer demand for functional dairy products. WPCs were produced from pasteurized liquid whey using either a commercial spray dryer or freeze dryer. A variety of analytical techniques, including enzyme-linked immunosorbent assay, polyacrylamide gel electrophoresis, and bottom-up proteomics using liquid chromatography-tandem mass spectroscopy were used to identify, quantify, and compare the retention of bioactive proteins in WPC before and after spray drying and freeze drying. In addition, the extent of denaturation was studied via solubility testing, differential scanning calorimetry, and hydrophobicity assessment. There was little to no difference in the retention or denaturation of key bioactive proteins between spray-dried and freeze-dried WPC powders. There was a higher percentage of select Maillard modifications in freeze-dried and spray-dried powders than in the control. The lack of significant differences between spray drying and freeze drying identified herein indicates that freeze drying does not meaningfully improve retention of bioactive proteins compared with spray drying when performed after multiple pasteurization steps. PRACTICAL APPLICATION: This study aimed to provide insight into the impacts of spray drying versus freeze drying on whey proteins. Overall, our results indicate that for commercial dairy processing that involves multiple rounds of pasteurization, freeze drying does not meaningfully improve the retention of bioactive proteins compared with spray drying. These findings may help the food and dairy industry make informed decisions regarding the processing of its whey protein products to optimize nutritional value.

The authors would like to make the following corrections to this paper [...]

The aim of the present study was to evaluate the concentration of sodium pyruvate in growth media by using the most-probable number method to decompose carried-over liquid hydrogen peroxide (H2O2) without negative influences on correct enumeration of Geobacillus stearothermophilus spores. An equivalent molar ratio of sodium pyruvate and H2O2 was verified to be sufficient for a complete decomposition. The results showed that by exposition of G. stearothermophilus spores in different liquid hydrogen peroxide and by carry-over of concentrations ranging from 3.56 center dot 10(-6) up to 1.69 center dot 10(-4) mol, a sodium pyruvate concentration of 0.05 mol L-1 in growth media was most efficient for the recovery of spores.

Fermentation processes can only succeed if intact and active starter cultures are present. Bacteriophages, which can lyse bacteria and thus bring entire fermentation processes to a standstill, therefore pose a major threat. Cheese production, for example, is often affected. The by-product whey can be highly contaminated with bacteriophages (≤109 plaque-forming units/mL) and in this state, further utilization is a quality and processing risk. Therefore, an orthogonal process consisting of membrane filtration followed by UV-C irradiation could be applied to eliminate bacteriophages and to generate “phage-free” whey. In order to define suitable process parameters, 11 lactococcal bacteriophages belonging to different families and genera and differing in their morphology, genome size, heat resistance, and other attributes, were screened for their UV-C resistance in whey. P369 was found to be the most resistant and could thus be well-suited as a biomarker. Starting from a 4 log unit bacteriophage reduction by membrane filtration, another 5 log unit decrease should be realized when applying a UV-C dose of 5 J/cm2. A clear correlation of UV-C sensitivity to the chosen attributes studied such as bacteriophage morphology and genome size was difficult and ambiguous, presumably because other yet unidentified parameters are important. Mutation experiments were performed with the representative bacteriophage P008 by multiple cycles of UV-C irradiation and propagation. A few mutational events were found, but could not be linked to an artificially generated UV-C resistance, indicating that the process used would probably not lose its effectiveness over time.

UV-C irradiation is a powerful non-thermal principle to inactivate lactococcal bacteriophages, which pose a high risk for fermentation failures in dairies. However, milk products limit ray penetration with their turbidity and absorption properties. In reactor design, attention must be paid to uniform and effective dose distribution, which can be achieved by thin fluid layers and/or turbulence. Preliminary tests performed in a lab-scale batch mode irradiation chamber showed filtered whey to be the most suitable application site. In a subsequent larger-scale feasibility study, two continuous flow-through reactors (lab-scale and technical-scale) were investigated. A bacteriophage reduction of 5 log units required a volume-related UV-C dose of 10.6 J mL-1 in the irradiation chamber, but only 1.8 J mL-1 in the continuous lab-scale reactor and 2.4 J mL-1 in the continuous technical-scale reactor. These data show that upscaling is feasible and that an effective bacteriophage inactivation with gentle product treatment is allowed. & COPY; 2023 Elsevier Ltd. All rights reserved.

The rheological properties, e.g., viscosity and yield stress, of fermented concentrated milk products (protein content > 8%) are strongly dependent on their volume fraction. Post-treatment with high-power ultrasound can reduce the volume fraction of these products and, hence, lead to reduced crowding effects and thus lower viscosities and yield stress. Besides that, the particle size distribution (span) should stay unaltered. Increasing the energy input during the sonication of fat-free fresh cheese with a protein content of 8.9 ± 0.4% decreased the volume fraction below the limit for concentrated products (ϕ = 0.4), while the particle size also decreased. This led to a narrowed span and, hence, the viscosity should have increased; however, the results showed that viscosity and yield stress were decreasing. Consequently, the influence of the span was neglectable for concentrated fermented milk products with volume fractions below the concentrated area. Furthermore, the sonicated samples showed no syneresis over a storage time of two weeks. The sonicated samples reached similar rheological properties to commercial stirred yogurt, which demonstrated the suitability of high-power ultrasound as a post-treatment to tailor the rheological properties of high-protein fermented milk products.

Lactococcus lactis phages can be very heat resistant and phage P680 survive pasteurisation. In this work, phage growth, thermal and non-thermal as well as chemical methods were presented together and reevaluated in the elimination of P680. A fermentation failure within 2 h can occur under the presence of phage P680, which survived heating at 95 degrees C for 5 min. Up to 4 log units of reduction could be achieved using membrane filtration (cut-off 100 nm). In case of ultraviolet-C treatment, doses up to 0.05 J cm(-2) and 4 J cm(-2) were required for phage P680 to achieve 6 log units reduction in water and 8 log units reduction in filtered whey. Phage P680 was mostly resistant at pH levels of 3 and 10 (<0.5 log reduction), however, a significant drop of the phage levels was observed at pH values of 2 and 12 (similar to 6 log units of reduction). (C) 2022 Elsevier Ltd. All rights reserved.

This study presents a frothing system for testing steam frothing capacity for "barista"-style specialties and investigating foaming properties of protein suspensions and other liquid solutions. The presented foaming methodology is similar to the classic barista frothing with a steam wand. In addition, steam pressure and air entrainment into the sample can be controlled, to create reproducible froths. A steam-air-premix is entrained and dispersed into the sample to be frothed. Final sample temperature can be defined by frothing time and steam pressure and the final foam volume by frothing time and steam:air ratio.

Powdered milk products, such as skim milk powder or whey protein powder, represent a large fraction of the dairy sector, especially with respect to export. In the past years, the contamination with aerobic endospore-forming bacteria has become one of the main factors to evaluate microbial powder quality. Besides mesophilic spore formers, thermophilic and thermoresistant species have been isolated all over the world. During production of powdered commodities, milk or intermediate products go through several process steps. This review highlights and discusses individual production steps and their effect on the microbiota and the spore count. The plant cleaning and its influence on spore resistance are discussed in detail, since this is the most important step in controlling recontamination and persistence. Finally, future technologies to reduce spore counts during powder production are presented. The contribution on ‘non-thermal’ and novel technologies towards low-spore milk powders are discussed critically.

In this study, different adhesives manufactured by using various casein powders (micellar casein, αS-, β- and ĸ-casein fractions, sodium caseinate and calcium caseinate) were investigated for their properties and potential application in the food industry. Casein-based adhesives using different sources of caseins were produced and the differences in their adhesive strength were determined. For the isolation of casein fractions, the methods of selective solubility, precipitation and a decanter centrifuge (for separation of precipitated casein and supernatant) were used. Achieved purities of αS-, β- and κ-casein fractions were higher than 25, 91 and 54%, respectively. Results showed that the type of casein raw material used in the production of adhesives had an influence on the adhesive properties and the highest adhesive strength was achieved with the enriched αS-casein fraction and micellar casein.

There is a bidirectional interaction between the gut microbiota and human health status. Disturbance of the microbiota increases the risk of pathogen infections and other diseases. The use of bacteriophages as antibacterial therapy or prophylaxis is intended to counteract intestinal disorders. To deliver bacteriophages unharmed into the gut, they must be protected from acidic conditions in the stomach. Therefore, an encapsulation method based on in situ complexation of alginate (2%), calcium ions (0.5%), and milk proteins (1%) by spray drying was investigated. Powdered capsules with particle sizes of ~10 µm and bacteriophage K5 titers of ~107 plaque-forming units (pfu) g−1 were obtained. They protected the bacteriophages from acid (pH 2.5) in the stomach for 2 h and released them within 30 min under intestinal conditions (in vitro). There was no loss of viability during storage over two months (4 °C). Instead of consuming bacteriophage capsules in pure form (i.e., as powder/tablets), they could be inserted into food matrices, as exemplary shown in this study using cereal cookies as a semi-solid food matrix. By consuming bacteriophages in combination with probiotic organisms (e.g., via yoghurt with cereal cookies), probiotics could directly repopulate the niches generated by bacteriophages and, thus, contribute to a healthier life.

Lactococcal bacteriophages can cause fermentation failures in the cheese production (e.g., Cheddar), especially when the by-product whey (<= 10(9) plaque-forming units mL(-1) of bacteriophages) is recycled and added to new batches. Using membrane filtration, the bacteriophage titre in whey can be reduced by 4 log units without protein denaturation. To achieve higher bacteriophage reduction (>= 9 log units), we attempted an orthogonal process strategy (combination of different technologies supporting each other). Three representative bacteriophages were inactivated in membrane filtered whey by (i) UV-C irradiation and (ii) heat treatment to achieve additional 5 log units reduction. Thermal treatment was only partially successful, as the varying degrees of heat resistance required, in the worst-case, temperature-time combinations above pasteurisation conditions. In contrast, UV-C treatment required doses of maximally 2.25 J cm(-2) for successful inactivation, thus representing a promising avenue for the establishment of a novel process for the production of "phage-free" whey. (C) 2021 Elsevier Ltd. All rights reserved.

This chapter focuses on the heat stability of indigenous (expressed from different bovine tissues and cells, then secreted into milk) and bacterial (exogenous) dairy enzymes as well as thermal and non-thermal inactivation methods. The fundamentals of heat inactivation kinetics are outlined and the heat stabilities of the following enzymes are discussed in detail: alkaline phosphatase, γ-glutamyltransferase, lactoperoxidase, lipoprotein lipase, cathepsin D, plasmin, and peptidases from Pseudomonas ssp. Based on the presented kinetic data of these enzymes, inactivation lines revealing possible temperature-time combinations for a targeted inactivation were calculated. The given information should serve as a base to deduce individual parameters (e.g., time and temperature) for handling each dairy derived enzyme.

There has been a growing interest in casein fractions (αS-, β- and κ-casein) due to their various techno- and bio-functional properties and as source for bio-active peptides. Several methods for isolating and purifying caseins have been reported. However, there is still room for improvement regarding purity and yield. In this study, three casein fractions were obtained by selective precipitation. A continuous process generating three major casein fractions using a temperature-controlled decanter centrifuge for separation was developed and suitability of the experimental setup was established. The process stability evaluated and the effect of operational parameters of the decanter on the separation process was investigated. The enrichment of the fractions was optimised by adjusting the operational parameters, e.g., inner weir diameter, centrifugal force and differential speed. The purity and yield of the fractions obtained were 39.6% and 96.1% for αS-casein, 92.1% and 27.5% for β-casein and 39.2% and 54.1% for κ-casein, respectively.