Heat Treatment Of Milk Research Articles

Ultra-high Temperature (UHT) Processing: Technological Significance and Updates

Background: Background: Milk forms an integral part of the human diet from the nutritional point of view. Besides nutrition, it has also unique functional properties which are harnessed by the industry for numerous uses. Being highly perishable specific techniques are required to minimize the losses during processing and adequate preservation of this precious commodity. In the U.S. and many other parts of the world, the traditional pasteurization of milk requires a minimum heat treatment of 72ºC for 15 seconds with subsequent refrigeration. However, the advent of Ultra High Temperature (UHT) treatment of milk has added a new dimension to the marketing of liquid milk in urban as well as remote areas without the requirement of cold chain management. The distinctive feature of UHT processed milk is that it is commercially-sterile-not pasteurized and so has long shelf life at room temperature. UHT milk, also known as long-life milk, is emerging as an attractive commercial alternative offering a hygienic product of unmatched quality, which can be bought anywhere, at any time and in any quantity. The present review will discuss numerous aspects of UHT processing of milk with reference to historical significance, fundamental principle, various systems used and prerequisites, type of exchangers used, fouling and other defects in system, chemical and microbiological effect of the treatment, its effect on nutritional components, organoleptic quality of milk and the advantage and involved challenges of the process. Conclusion: Raw milk is easily contaminated with pathogens and microbes and hence its consumption of raw milk is associated with certain ill health effects. Therefore, heating milk before consumption is strongly suggested. Thus, UHT treatment of milk is done to ensure microbial safety and also to extend the shelf life of this highly perishable commodity. Heating milk at such a high temperature is often associated with the change of organoleptic properties like change in flavor or cooked flavor, rancidity due to microbes or acid flavor, etc. But UHT treatment does not substantially decrease the nutritional value or any other benefits of milk.

Metabolic Availability of Lysine in Milk and a Vegetarian Cereal–Legume Meal Determined by the Indicator Amino Acid Oxidation Method in Indian Men

Lysine rich foods such as milk and legumes serve as important food additions to the lysine deficient cereal-based diets of vegetarian populations in low- and middle-income countries (LMICs) to alleviate the risk of quality corrected dietary protein inadequacy. Dietary protein quality can be determined by estimating the metabolic availability (MA) of lysine. The study aimed to estimate the MA of lysine in spray-dried cow milk powder (SMP), heat-treated spray-dried cow milk powder (HSMP), and a habitually consumed cereal-legume based vegetarian meal (VM), using the indicator amino acid oxidation (IAAO) slope-ratio method. The MA of lysine in SMP, HSMP, and VM was estimated in 7 healthy young men aged 19-24 y with BMI of 21.5±0.5kg/m2 in a repeated measures design. The IAAO response slopes with 2 graded lysine intakes (10.5 and 15.0 mg·kg-1·d-1) from the SMP and VM were compared with the response slope generated with 3 graded crystalline lysine intakes (6.0, 10.5, and 15.0 mg·kg-1·d-1) at the subrequirement level. To produce HSMP, pasteurized cow milk was heat treated and spray dried. The MA of lysine in HSMP was tested at a single level of lysine intake (15 mg·kg-1·d-1). A total of 8 IAAO experiments were conducted on each participant in randomized order. The IAAO slopes were estimated using a linear mixed-effect regression model. The MA of lysine in SMP, HSMP, and VM was 91.9%, 69.9%, and 86.6% respectively. Heat treatment reduced the MA of lysine by 22% in HSMP compared with SMP in healthy Indian adults. The lysine MA estimates can be used to optimize lysine limited cereal-based diets, with the addition of appropriately processed legumes and milk powder, to meet the protein requirement. This trial was registered at Clinical Trials Registry of India (http://ctri.nic.in) as CTRI/2019/08/020568.

Forming technological traits of dry milk

Dry milk is used in a wide variety of products due to its high energy value and long shelf life. Its use is especially valuable in the dairy industry, since it smooths the seasonality of raw milk production. Moreover, dry milk makes it possible to generate socially essential products in the regions of Russia where dairy farming is not developed or where it is impossible to produce raw milk. There are different methods to form dry milk's traits and the required functional features like cheesability, heat stability and solubility. Among these methods we emphasize on technological ones, based on prevention measures of impact on raw milk during its processing. As a result, methods for the increase of dry milk's heat stability are among the most essential, since its low values make it impossible to generate products of high quality or to use this milk in any processing at all. A number of foreign and national works are dedicated to the improvement of dry milk's heat stability. These studies offer various methods like an effective refining of raw milk, its preliminary heat treatment, the use of specific food supplements and raw milk components, the correction of physicochemical values, the variation of temperature regimes, the use of unconventional equipment for desiccation and condensation. Integrated methods of heat stability increase do not require core changes in the current technological requirements of dry milk production and can be integrated into the existing production conditions, thus they arose a lot interest and have prospects. This overview allows to broaden knowledge and to find new methods to form technological traits of not only dry milk, but canned milk as well.

Effect of packing pH values on the crumbliness of fresh Turkish White cheese

A significant amount of Turkish White cheese is still produced in 1-kg cheese blocks and distributed to retail stores and farmers markets in 18-kg tin containers with brine. Portioning the cheese for the customer's desired weight requires a slicing process. The crumbs that occur during cutting or portioning are undesirable for customers and can cause economic loss for the business. In this study, our goal was to investigate the sliceability of White cheese that was manufactured at various final packing (i.e., packing with brine) pH values (5.3, 5.0, 4.7). For this purpose, we manufactured 4 batches of cheese at different times from high heat-treated milk (78°C, 8 min) and monitored the chemical and textural properties at 1, 2, 4, and 8 wk. Cheeses that were packed at pH 4.7 were harder compared with cheeses that were packed at pH 5.0 and 5.3. No correlation was observed between cheese-packing pH values and the size of the crumbs; however, there was a significant negative correlation between packing pH and crumb weight (i.e., decrease in cheese-packing pH increased the crumb weight). Cheeses packed at pH 5.0 and 5.3 exhibited increased slicing adhesiveness during storage. All cheese samples exhibited similar colloidal calcium phosphate levels and water-soluble nitrogen values during storage. This study showed that an increase in the packing pH of White cheese reduced the weight of crumbs that occurred during cutting. This study is the first study to investigate crumbs occurring with slicing in White cheese. This is also the first study in the literature that monitored the colloidal calcium phosphate content of Turkish White cheese.

A randomized trial of oral immunotherapy for pediatric cow's milk-induced anaphylaxis: Heated vs unheated milk.

BackgroundSevere reactions may develop during cow's milk (CM) oral immunotherapy (OIT). We investigated the safety and efficacy of low‐dose OIT with heated milk (HM) or unheated milk (UM) in children with anaphylaxis.MethodsChildren with symptom onset after ingestion of 3‐mL HM on a double‐blind, placebo‐controlled food challenge were randomly assigned to the HM (n = 17) or UM (n = 16) group. HM group ingested milk powder heated at 125°C for 30 seconds, whereas the UM group used UM. Patients were hospitalized for 5 days; the HM or UM was gradually increased to 3 mL/day; 3‐mL/day ingestion was continued at home. One year later, the patients underwent 2‐day consecutive 3‐ and 25‐mL HM‐oral food challenges (OFCs) after 2‐week avoidance.ResultsAt baseline, milk‐ and casein‐specific immunoglobulin E (IgE) levels were 56.0 and 51.4 kUA/L in the HM group, and 55.2 and 65.6 kUA/L in the UM group, respectively. One year later, 35% and 18% in the HM group and 50% and 31% in UM group passed the 3 and 25 mL OFCs, respectively. Rates of moderate or severe symptoms and respiratory symptoms per home dose were significantly lower in the HM than in the UM group (0.7% and 1.2% vs 1.4% and 2.6%, respectively, P < .001). β‐lactoglobulin‐specific IgG4 levels significantly increased from baseline only in the UM group, whereas casein‐specific IgG4 levels significantly increased from baseline in both groups.ConclusionsHM‐OIT induced immunological changes more safely than the UM‐OIT. The possibility of lower treatment efficacy with HM‐OIT needs to be evaluated in larger studies.

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

Lactoperoxidase (LPO) is one of the major antibacterial ingredients in milk and an extensively employed indicator for milk heat treatment. The traditional method for LPO activity measurement using ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonate) cannot achieve high sensitivity and is affected by indigenous milk thiocyanate. A more sensitive microplate fluorescent assay was developed by monitoring generation of red-fluorescent resorufin from LPO catalysed oxidation of Amplex® Red (1-(3,7-dihydroxyphenoxazin-10-yl)ethanone) in this study. The assay is particularly suitable for milk LPO activity measurement as it eliminates the influences of indigenous milk hydrogen peroxide and thiocyanate. The method limit of detection was 7.1x10−6 U/mL of LPO in milk and good intra-run and inter-run precision was obtained. The LPO activities ranked as bovine > goat > camel > human in the four types of milk analysed. The high sensitivity and low cost of this assay makes it suitable for LPO activity analyses in both laboratory and commercial scales.

Enzymatically Cross-Linked Sodium Caseinate as Techno-Functional Ingredient in Acid-Induced Milk Gels

Sodium caseinate is widely used as techno-functional ingredient in food processing. However, no studies are currently available on applications of enzymatically cross-linked sodium caseinate although such a modification might have a potential to improve its techno-functional properties and thus reduce the amount of protein necessary to achieve the desired product properties. In the present study, aqueous sodium caseinate solutions were cross-linked by microbial transglutaminase to different extents and subsequently spray-dried. These powders were either redissolved in water or added to reconstituted skim milk to compare acid-induced gels from sodium caseinate solutions to gels from milk with added sodium caseinate. Gelation induced by glucono-δ-lactone was studied using time-based oscillation rheology. The maximum storage modulus (G′MAX) of sodium caseinate gels increased with increasing cross-linking extent, whereas enriched milk gels showed a peak in G′MAX at moderate cross-linking extents. Heat treatment of the enriched milk shifted the highest G′MAX to an even lower cross-linking extent. The results show that constituents of complex food matrices as well as processing routes affect the techno-functional properties of modified food proteins such as cross-linked caseins. It was possible to reduce the amount of added protein from 10 to 7.5 g/kg when cross-linked sodium caseinate was used while obtaining milk gels with similar G′MAX and forced syneresis. Future studies should elaborate ways to further improve the properties of cross-linked sodium caseinate to allow for an even greater reduction in protein enrichment.

Examination of Aflatoxin M1 Contamination in Milk and Milk Drinks Available in Fukuyama City

To determine the relationship between seasons and regions and aflatoxin M1 (AFM1) contamination of milk distributed in Fukuyama City, we conducted a survey once during the summer and once during the winter between June 2018 and January 2019. We compared the AFM1 contamination levels in milk drinks available in Fukuyama City during the same period, to provide more about the factors causing AFM1 contamination. All milk samples examined exhibited AFM1 contamination levels below the standard AFM1 contamination level (0.5 μg/kg). For the comparison based on seasons, one milk sample collected in the summer (0.07 μg/kg) exceeded the EU limit (heat-treated milk: 0.050 μg/kg). However, there was no significant difference in the AFM1 contamination level (p>0.05). For the comparison based on regions, the AFM1 contamination level in the milk sample from the Chugoku Region was significantly higher in the winter and significantly lower in the summer compared to those from other regions. AFM1 contamination of milk did not have a direct relationship with seasons or regions, but was instead influenced by the type, amount, and management of feed supplied to dairy cattle. For the comparison between milk and milk drinks, the AFM1 contamination levels in milk drinks were significantly lower (p<0.01). The highest AFM1 concentration (0.08 μg/kg) was detected in one sample of milk drink sampled during the summer. The AFM1 contamination of milk drinks is likely affected by the level of contamination in raw materials, the proportion of such raw materials in the drinks, and the process type. An increase in non-fat milk solids was assumed to be a factor that increases AFM1 contamination.

Modeling heat stress under organic dairy farming conditions in warm temperate climates within the Mediterranean basin

We studied the effect of heat stress on milk quality in Spanish organic dairy farms using published milk productivity equations. We collected data from 23 weather stations and 14,424 milk test-days for milk yield and milk fat and protein content for the period July 2011 to June 2013. As an indicator of heat stress, we used the maximum daily temperature–humidity index (THI) from 2 days before the milk test date. We fitted the data using hierarchical regression models stratified by farm, cow parity and monthly test-day milk records. The effect of THI was deemed low on biological costs through milk yield. However, the known negative relationship between milk yield and milk quality (protein and fat content) became even steeper when the THI increased, suggesting a significant negative correlation between heat stress and milk quality. Therefore, although the milk yield of cows in the organic farming systems analyzed appeared resilient to heat stress conditions, milk quality, a major selling point for organic dairy products, was negatively affected. The model presented here could be used to predict the potential impacts of different climate change scenarios on dairy farming, and to delineate adaptation strategies within organic systems.

Quality by design of yogurt product using taguchi multi responses method

Quality of yogurt could be determined based on its flavor and texture which could be tested using an organoleptic test. The quality objective of the yogurt flavor and texture is larger the better. As one of the intermediate products that could be processed to become various other products, the demand for yogurt is continuously increasing in Indonesia. Along with the increase in demand, the demand for quality of yogurt has also increased. In this study, experiments have been conducted to improve the quality of a yogurt product. The experiments were designed based on the Taguchi method with Multi Responses Signal to Noise (MRSN) that involves 7 factors consists of 6 controllable factors and 1 uncontrollable factor. Every factor has 2 levels of an experiment. The 6 controllable factors are heating temperature, heating duration, number of yogurt seeds, incubation temperature, incubation duration, number of sugars, while the uncontrollable factor is the weather condition. Result of the experiments showed when weight for flavor and texture is 0.437 and 0.563 respectively, the levels of the optimum factors are 950C for milk heating temperature, 20 minutes for the duration of milk heating process, 75 ml of yogurt seeds, 450C of the temperature of incubation, 6 hours of incubation duration and 12.5 grams of sugar weight. Based on the organoleptic test that conducted by a group of experienced testers, the new optimum factors combination could improve the yogurt’s quality in term of flavor and quality up to 16.24% and 11.37% respectively. It could be concluded that the proposed method could improve the quality of yogurt-based on preferences from the experienced testers that have been expressed by the weight of every quality response.

Effect of milk pH at heating on protein complex formation and ultimate gel properties of free-fat yoghurt.

The effect of milk pH before heating on casein-whey protein interactions and ultimate gel properties of the free-fat yoghurt was investigated. Reconstituted skim milk at different pH values (6.4, 6.8 and 7.2) was heated at 80°C for 30min. The type of protein and size of casein micelle in milk were determined. The storage modulus (G'), loss tangent (tan δ), flow behaviour as well as microstructure, firmness and water holding capacity of the yoghurt samples were measured. Heating milk at pH 7.2 formed mostly soluble protein complexes whereas at pH 6.4 micelle bound complexes was dominant. However, heating milk at pH 6.8 resulted in a relatively compact protein network due to a balanced contribution from both soluble protein/κ-casein complexes and whey protein-casein micelle associated complexes. Yoghurt prepared with milk heated at pH 6.8 showed significantly higher G' values, shorter gelation times, higher water holding capacity, firmness and more compact protein network compared to those at pH 6.4, 7.2 and unheated milk. The obtained results demonstrated that milk pH adjustment before heating could be an important factor governing uniform quality yoghurt production.

Effect of heating milk on whey protein denaturation and cheese-making properties

The cheese-making properties of milk heated at 80 °C for different times (0–8 min), and mixtures of severely-heated milk (80 °C, 30 min) with non-heated milk were evaluated in separate experiments. In both approaches, milk pH was adjusted to 6.3, 6.7 or 7.0 before heating. Despite different distributions of denatured whey protein (WP) between casein micelle surface and serum phase, heating pH had no significant effect on cheese-making properties. The two approaches were compared by reporting the results as a function of WP denaturation rate in milk. The mixed milk approach showed a higher detrimental effect on rennet-induced coagulation kinetics and curd contraction capacity during cooking than the heated milk approach. For similar WP-denaturation rate, higher yield was obtained for the mixed milk than the heated milk as a result of the better protein retention and larger increase of cheese moisture.

Conventional heating, ultrasound and microwave treatments of milk: Fermentation efficiency and biological activities

The individual and combined effects of ultrasound, microwave, and heat treatment of milk on L. acidophilus viability, lactate concentration and bioactive properties (radical scavenging capacity, proteases activities, peptide level, anticancer activity, α-amylase inhibition and exopolysaccharide content) during fermentation were investigated. It was notable that Lactobacillus acidophilus exhibited by far the best growth in microwave treated samples, while ultrasonicated microwaved samples had higher antioxidant and anticancer activities. The antioxidant activity of ultrasonicated microwaved milk at the end of fermentation was 13.9%, 44.7% and 77.3% higher than that of ultrasonicated autoclaved, microwaved and autoclaved samples, respectively. After 24 h fermentation, the average protease activity of the microwaved milk was 1.3–1.8 times more than the observed values in the other treated samples. The amount of exopolysaccharide, anticancer activity and α-amylase inhibition of ultrasonicated microwaved milk, especially after 8 h fermentation, were also significantly higher than those of the other treated milks.

Effect of heat treatment of milk on the physicochemical, microbiological and sensory characteristics of white cheese (Gibna bayda)

This study was conducted to determine the effect of heat treatment of milk on the physicochemical, microbiological, and sensory characteristics of white cheese (Gibna bayda). The cheese was made from raw warmed (45 °C) milk (T1) and heat-treated (72 °C/1 min) milk (T2) to which the starter culture (2% w/w), sodium chloride (2% w/w) and CaCl2 (0.02% w/w) were added. After manufacture, cheese was preserved at 5 °C for 45 days and subjected to physicochemical, microbiological, and sensory analysis. The results revealed that T2 had longer coagulation time (75.5 min) and higher cheese yield (17.1 kg/100 L) compared to T1. Fat (25.28%), moisture (55.70%), and ash (6.40%) contents were higher in T1, while protein (18.51%), total solids (47.49%) contents, and acidity (0.56%) were high in T2. Total viable bacteria [TVB] (log10 6.64 cfu/gm), Staphylococcus aureus (log10 1.88 cfu/gm) and yeasts and moulds (log10 5.53 cfu/gm) counts were high in T1, while Escherichia coli count was log10

Effect of heat treatment of milk on the physicochemical, microbiological and sensory characteristics of white cheese (Gibna bayda)

Effect of heat treatment of milk on the physicochemical, microbiological and sensory characteristics of white cheese (Gibna bayda)

Microstructure of kajmak skin layer made during kajmak production

Kajmak is a unique dairy product with a long tradition in Balkan countries and the Middle East. Kajmak skin layers are formed during 60 minutes of kajmak production, influencing the quality and determining the structure of the final product. The influence of milk composition and heat treatments (75-95 °C/5min) on the composition, microstructure and protein distribution of kajmak skin layers was investigated in this study. Microstructure was determined using scanning electron microscopy (SEM), while the distribution of protein fractions was studied by SDS PAGE in reducing and non-reducing conditions. Kajmak skin layers obtained from milk treated at common intense heat regime were characterized with β-LG and α-LA mainly as disulfide-linked complexes, while lower temperature (75 °C) caused the presence of whey proteins in dominantly individual form. More severe treatments (85 °C, 90 °C and 95 °C) caused the full involvement of β-LG in the complexes, since a certain amount of α-LA was found as a monomer. The kajmak skin layer composition, severity of the applied milk heat treatment and the linked whey proteins exhibited a very strong influence on kajmak skin layer microstructure. The microstructure of kajmak skin layer with a low fat content and fat/protein (F/P) ratio was characterized by a compact structure with a dense protein matrix. High fat content and F/P ratio resulted in a dispersive form of the stretched protein network. Kajmak skin layers produced from milk with added whey proteins were characterized by fibrous, thread-like segments, due to the incorporated denatured whey proteins, especially linked β-LG.

Monensin residues in the production of Minas Frescal cheese: Stability, effects on fermentation, fate and physicochemical characteristics of the cheese

Considering the widespread use of the antibiotic monensin (MON) in the Brazilian livestock and the possibility of residues in milk, this paper aimed to study the stability and fate of this drug during the production of Brazilian Minas Frescal cheese, its effects on milk fermentation and on the physicochemical characteristics of this product. For that, samples of raw milk were fortified with MON at three different nominal concentrations (1.0, 2.0 and 8.0 μg/kg), passed through heat treatment and used to produce Minas Frescal cheese. Pasteurization efficiency was certified by alkaline phosphatase and peroxidase enzyme tests and cheese samples were evaluated for pH, moisture and total protein and fat content. MON residues were determined by LC-MS/MS in the following steps: raw milk, heat-treated milk, whey and cheese. No significant degradation of MON due to heat treatment was observed, suggesting that the drug is resistant to high temperatures. Moreover, the residue levels quantified in cheese and whey demonstrated a concentration of this antibiotic in the curd by about 5-fold, with a small amount of MON being lost during draining. There were no significant differences (p > 0.05) considering the physicochemical parameters evaluated in cheese samples. Fermentation was also not affected by the presence of the drug. The results showed that residues of MON in milk are stable during cheese production and may be concentrated in the final product, as well as indicate the need to establish a MON safe residue level for this food commodity.

The effect of heat treatment on the front-face fluorescence spectrum of tryptophan in skim milk

The effect of heat treatment on tryptophan front-face fluorescence emission spectra of reconstituted skim milk was assessed. Samples were heat-treated from 70 to 100 °C at six holding times. Treating milk at 90 and 100 °C induced a decrease in fluorescence intensity (∼37 and ∼47 %) and a red shift (12 and 14 nm), respectively, with both parameters significantly affected at 99.9 % by temperature, time, and the interaction of both factors. Red shift, which could be attributed to whey protein denaturation and tryptophan exposure to increasing solvent polarity, was found to follow a quadratic trend as a function of holding time (from 0 to 60 min). The decrease of fluorescence intensity observed at those two temperatures and in the mentioned holding time range was also a quadratic function of the associated red shift. Emission intensity change at a single wavelength (∼340 nm) was partly caused by direct intensity decrease and indirectly due to the emission maximum shift. Tryptophan fluorescence allowed sample classification by PCA analysis according to heat load, i.e., temperature and time. These results established the bases for development of a cost-effective sensor based on simple, economic optical components for measurement of a few well-selected emission wavelengths, which associated with data processing, should allow inline control of milk heat treatment.

Evaluation of Heat and pH Treatments on Degradation of Ceftiofur in Whole Milk.

Waste milk feeding practices have been implicated as a potential source for disseminating antimicrobial resistant bacteria among animals and the environment. Two interventions that have shown potential for degrading antimicrobial drugs in milk are heat and pH treatment. The aim of this study was to evaluate the effect of heat and pH treatments on the degradation of ceftiofur and ceftiofur free acid equivalents in milk at concentrations previously found in waste milk on dairy farms by spiking saleable pasteurized whole milk with ceftiofur sodium. Three heat treatments of ceftiofur sodium spiked milk were evaluated for their ability to degrade ceftiofur: 63°C for 30 min (LTLT), 72°C for 15 s (HTST) and 92°C for 20 min (HTLT). Two pH treatments of ceftiofur sodium spiked milk were evaluated: pH 4.0 (LpH) and pH 10 (HpH). Control samples spiked with ceftiofur sodium were kept at room temperature and samples collected at corresponding times for heat and pH treatments. Four treatment replicates were performed for each treatment group. Ceftiofur was quantified in milk samples using liquid chromatography mass spectrometry (LC-MS/MS) and ceftiofur free acid equivalents (CFAE) were measured using high-performance liquid chromatography (HPLC). HTLT resulted in a degradation of 35.24% of the initial concentration of ceftiofur. Ceftiofur degradation did not differ between control and the remaining two heat treatment groups (LTLT and HTST). HpH resulted in degradation of the 95.72 and 96.28% of the initial concentration of ceftiofur and CFAE, respectively. No significant changes in degradation of ceftiofur or CFAE were observed for control or LpH treatments. In conclusion, our study results were that alkalinizing milk to pH 10 and heating milk to 92°C for 20 min degraded ceftiofur and CFAE in spiked simulated waste milk demonstrated promising potential as treatment options for degrading ceftiofur and CFAE in waste milk, and further research is needed to evaluate the viability for implementation of these treatments in dairy farms.

Survival of staphylococci and transmissibility of their antimicrobial resistance genes in milk after heat treatments

There is growing concern that the milk heat treatments, which are the main antibacterial safeguard in the dairy industry, are not sufficient in inactivating the antimicrobial resistance (AMR) genes of staphylococci and may induce a viable but non-culturable (VBNC) state of these microorganisms. This study investigated the persistence and quantification of blaZ, mecC and tetK plasmid-mediated AMR genes copy numbers of two staphylococcal strains in both milk and Tris-EDTA (TE) buffer. During subsequent storage after pasteurization, all tested genes showed increased copy numbers. By electroporation of these genes to the Staphylococcus aureus RN42200 electro-competent strain, both mecC and tetK genes were still expressive and transferable. The formation of VBNC cells was estimated with viability staining and quantitative PCR of 16S rDNA copy numbers of both staphylococcal strains. The copy numbers increased over the storage period, which suggests that the pasteurization process was a stress factor and likely induces VBNC state in tested staphylococci. This explains the continual increase in the copy numbers of AMR genes. In contrast, after the sterilization treatment all the genes showed decreases in copy numbers. Further studies are required to evaluate the efficiency of currently practiced pasteurization and to assess the hazard level of VBNC staphylococci.