Reconstituted Skim Milk Powder Research Articles

Foaming Properties and Foam Structure of Milk Determined by Its Protein Content and Protein to Fat Ratio

AbstractMilk proteins, integral to stable foam production, exhibit seasonal and type-dependent variations. Understanding the impact of protein levels with and without fat on foaming properties is essential for selecting suitable milk types and controlling the foaming process. In this study, we employed steam injection and mechanical mixing to assess foamability, foam stability, and foam structure of (1) reconstituted skim milk powder dispersions (1.5–15% solids concentration, corresponding to 0.5–5.0% protein), (2) reconstituted whole milk powder and commercial whole milk dispersions (0.5% protein), and (3) whole milk with added skim milk powder and milk protein concentrate (3.5 and 4% protein) and butter milk powder (0.5 and 1% total solid content). Results reveal that increasing solids concentration from 1.5 to 15% significantly increased lactose content, viscosity, and surface tension. However, these changes did not impact foamability or foam stability, while slightly decreasing air bubble size. At 0.5% protein, skim milk powder dispersions demonstrated higher foam volume (16 times greater) and more stable foam compared to reconstituted whole milk powder and whole milk dispersions, despite similar foam structure and appearance. These findings emphasize the substantial influence of the protein/fat ratio on milk’s foaming properties. Additionally, the addition of skim milk powder, milk protein concentrate, or butter milk powder at the investigated content did not affect the foaming properties of whole milk.

Influence of minerals on the foaming properties of milk

A comprehensive study on the effect of mineral content on milk foaming properties was conducted. Samples with increased mineral concentration were prepared by adding four different types of minerals (KH2PO4, K3Cit, CaCl2 and MgCl2) at three different concentration levels (5, 10 and 20 mM) in both reconstituted skim milk powder and milk protein concentrate. Samples with reduced minerals were prepared by reconstituting milk protein concentrate in modified simulated milk ultrafiltrates. Different mineral types showed different effects on the physicochemical properties of milk samples. The addition of K3Cit increased the viscosity and decreased the surface tension while there were no significant differences between the samples added with KH2PO4, MgCl2, or CaCl2. In terms of foaming properties, the addition of CaCl2 or MgCl2 significantly increased the foam strength and stability while decreasing foamability. In contrast, the addition of K3Cit significantly decreased foam stability and foam strength while increasing foamability. It was also found that reduction in minerals in the range studied did not affect the foaming properties of milk. These results indicate that the effect of minerals on milk foaming properties depends on the type of mineral and the concentration. This provides an insight that while designing dairy-based food products, the mineral content can be manipulated to achieve the desired foaming properties.

Study on internal structure of casein micelles in reconstituted skim milk powder

In the current study, the internal structure of casein micelles (CMs), primary casein cluster, has been studied by size-exclusion chromatography (SEC) coupled with small-angle X-ray scattering (SAXS), isothermal titration calorimetry (ITC), transmission electron microscopy (TEM) and molecular dynamics (MD) simulations. The casein cluster featured a hierarchical structure predominately consisting of αs-CN and β-CN molecules and a trace of κ-CN. ITC profile showed a typical enthalpogram of CMs with a critical micelle concentration (CMC) of ~0.85 μg/mL. The casein cluster exhibited apparent characteristics of intrinsically disordered proteins (IDPs) with a secondary structure content of 24 % in α-helix, 35.4 % in antiparallel-parallel, 20.2 % in β-turn and 20.4 % in random coil. SAXS results revealed a slightly elongated and tortuous worm-like conformation for the casein cluster in solution with an aspect ratio of 1.36 and an estimated molecular weight of 162.7 kDa. Further scattering data analysis proposed three coexisted species (αs1-β-αs2-CN, αs1-CN and αs1-β-αs2-CN dimer) with a volume fraction of 57.4 %, 30.1 %, and 12.5 % respectively in the casein cluster. TEM observation was consistent with the results of spectra, SAXS and MD that calcium sequestration resulted in a more extended and loose structure, instead, EDTA chelation induced a more compact conformation of the casein cluster.

Influence of Ethanol on the Acid-Induced Flocculation of Casein Micelles

The influence of ethanol (0–10%, v/v) on the acid-induced flocculation of casein micelles was examined using diffusing wave spectroscopy. For this purpose, samples containing 10% (w/w) reconstituted skim milk powder and 0–10% (v/v) ethanol were acidified with glucono-delta-lactone and acid-induced coagulation was monitored by diffusing wave spectroscopy. The pH at which acid-induced flocculation of the casein micelles commenced (pHf) increased near-linearly with increasing ethanol content, whereas the rate of flocculation was not affected by ethanol. The results are discussed in terms of the steric stabilisation of casein micelles by a polyelectrolyte brush in a medium of high ionic strength. Ethanol-induced increases in pHf are probably primarily due to an ethanol-induced reduction in solvent quality; an ethanol-induced reduction in dissociation of carboxylic acid groups in the brush is likely to contribute.

Mid-infrared spectroscopy: Screening method for analysis of food adulterants in reconstituted skimmed milk powder

This study successfully shows that MilkoScan™ FT1 can be employed as rapid screening technology for detecting sixteen out of twenty-one food adulterants in reconstituted skimmed milk powder. The validation of untargeted fingerprinting method correctly identified 100% of unadulterated samples and 93% of samples adulterated with nitrogen-rich compounds or bulking agents at 5% economical adulteration. Furthermore, this work shows that lactose is a challenging adulterant to be detected by an untargeted screening method because it is naturally present in skimmed milk powder. However, this study showed that specific calibration can be applied to detect addition of lactose in skimmed milk powder. As a result, this method of screening displays a high potential to be employed by various food businesses (such as dairy, confectionary and infant formula, etc.) to rapid screening of raw materials and detect abnormalities, which may be linked to food adulteration or quality defects, ensuring products of better quality and safety to consumers. • Detection of food adulterants in reconstituted skim milk powder using mid-infrared. • Untargeted screening method for detection of nitrogen-rich compounds and bulking agents. • The adulterated and unadulterated samples show sensitivity of 93% and 100%, respectively.

Tryptophan front-face fluorescence and functional properties of whey: A preliminary study

This study investigated the potential of front-face fluorescence spectroscopy to predict the functional properties of whey. Whey has a commercial interest due to its excellent nutritional value and versatile functional properties. However, its attributes depend dramatically on heat treatment, which may alter its suitability for different food applications. Tryptophan front-face fluorescence of whey and its functional properties, i.e., foaming, gel-forming, and emulsifying properties, were evaluated after milk heat treatment (at 80 °C with seven holding times) to detect correlations between tryptophan fluorescence and functional parameters and generate predictive models. Whey samples were obtained by isoelectric precipitation of caseins from reconstituted skim milk powder enriched with whey protein isolate. As expected, heat treatments induced an increase in whey protein denaturation, as well as a decrease in total whey protein concentration and tryptophan fluorescence intensity. Gel-forming and emulsifying properties of whey significantly correlated with the maximum intensity of tryptophan (P < 0.001). Concerning foaming properties, only the foam stability index revealed a weak correlation with tryptophan maximum intensity (P < 0.05). Consequently, models presented strong significances (P < 0.001). Specifically, using only tryptophan fluorescence allowed successful prediction of emulsifying properties but was not enough for foaming and gel forming properties.

Chemical, Rheological, Microbiological and Organoleptic Properties of Labneh Manufactured by Using Some Vegetable Oils

Vegetable oils have many nutritional and therapeutic benefits, as it contains essential fatty acids and antioxidant compounds. In this study, virgin olive oil, sunflower oil, corn oil, and sesame oil were used in labneh manufacture for increasing its health benefits. Labneh was manufactured by using reconstituted milk skim milk powder and 1-2% of different vegetable oils. The chemical, rheological, microbiological, and organoleptic properties of labneh manufactured by using vegetable oils were determined. There were slight significant differences in moisture, protein, total nitrogen, fat, and ash values in labneh treatments while pH values decreased gradually until 21 days may be due to an increase in the acidity. Total viable count was gradually increased during storage up to 14 days, then they decreased in 21 days period of storage in treatments. Lactobacillus count was gradually increased during storage up to 21 days. Coliform and staphylococcus bacteria were not detected, while yeasts and molds were detected and reached a maximum at 21 days. Fracture, hardness, adhesiveness, cohesiveness springiness, and chewiness of fresh labneh treatments were determined. Organoleptic properties showed that with the increase in the percentage of vegetable oils, the total score of labneh treatments decreased, except for sesame oil. On other hand, all labneh treatments were sensually acceptable. The best treatment was fortified with 1% sunflower oil, it had a total score higher than the control treatment. Fortified labneh with virgin olive, sunflower, corn, and sesame oils can be considered as a new product with functional properties.

Manufacture of functional Kareish cheese fortified with Oat, Talbina, Lima bean and Sweet Lupin

Recently, fortification of kareish cheese with functional foods has gained momentum in response to the variable health status of developed countries, especially in Egypt. Functional foods such as oat, talbina, lima bean and sweet lupin were used in fortification of kareish cheese. Besides, determination of the chemical composition, microbiological counts, and rheological, organoleptic analysis. In this study, kareish cheese was made using reconstituted skim milk powder at a rate of 10% which was divided into 12 equal portions, one for the control and eleven were fortified with different concentrations 1%, 2% and 3% of the functional foods under study excepting for the ratio 3% of oat addition. The addition of those functional foods had an observed increasing effect on the content of cheese moisture, also a noticeable increase in fat, ash, fiber content, and slight increase in total protein. High acidity of kareish cheese remarkable by the addition. Total bacterial counts and lactic acid bacteria slightly decreased at zero time then started to increase significantly by the increase of the storage period until reached the maximum count at 21 days then the count began to decrease. Molds and yeasts increased by the increasing of storage period. The test results of Coliform and staphylococcus sp. Counts were negative. Rheological properties of kareish cheese were affected significantly by the addition of the functional foods under study. All treatments were sensually acceptable, but the most acceptable treatments were control and those fortified treatments with functional foods under study at ratio of 1%.

Acoustic attenuation spectroscopy and helium ion microscopy study of rehydration of dairy powder

Complete hydration is essential for the production of structured dairy products from powders. It is essential that the ingredients used hydrate completely. Determination of an end point of rehydration is non-trivial, but ultrasound-based methodologies have demonstrated potential in this area and are well suited to measuring bulk samples in situ. Here, acoustic attenuation spectroscopy (AAS) is used to monitor rehydration of skim milk powder, and recombined systems of micellar casein isolate with lactose and whey protein isolate. Dynamic light scattering, zeta-potential measurements and AAS as a function of pH characterise each component around its isoelectric point to assess its functionality. Scanning helium ion microscopy was used to image the dry powders, without any conductive coating, producing resolution equivalent to scanning electron microscopy, but with much larger focal lengths and fewer imaging artefacts. Imaging the powders provides information on particle size and morphology which can affect dissolution behaviour. Reconstituted skim milk powder and recombined samples were monitored showing there are changes occurring over several hours. Attenuation coefficients are shown to predict the end point of hydration. Model fitting is used to extract volume fractions and average particle sizes of large and small particle populations in recombined samples over time. AAS is demonstrated to be capable of tracking the dynamics in rehydrating dispersions over time. Physical parameters such as the volume fraction and particle size of the dispersed phase can be determined.

Effect of thermoresistant protease of Pseudomonas fluorescens on rennet coagulation properties and proteolysis of milk

This study aimed to investigate the effect of different activity levels of a thermoresistant protease, produced by Pseudomonas fluorescens (ATCC 17556), on the cheesemaking properties of milk and proteolysis levels. Sterilized reconstituted skim milk powder was inoculated with the bacteria, and after incubation, centrifuged to obtain a supernatant-containing protease. Raw milk was collected and inoculated to obtain a protease activity of 0.15, 0.60, and 1.5 U/L of milk (treatments P1, P4, and P10, respectively). One sample was not inoculated (control) and noninoculated supernatant was added to a fifth sample to be used as a negative control. Samples were stored at 4°C for 72 h. After 0, 48, and 72 h, the rennet coagulation properties and proteolysis levels were assessed. The protease produced was thermoresistant, as no significant differences were observed in the activity in the pasteurized (72°C for 15 s) and nonpasteurized supernatants. The chromatograms and electrophoretograms indicated that the protease preferably hydrolyzed κ-casein and β-casein, and levels of proteolysis increased with added protease activity over storage time. The hydrolysis of αS-caseins and major whey proteins increased considerably in P10 milk samples. At 0 h, the increase in the level of protease activity decreased the rennet coagulation time (RCT, min) of the samples, possibly due to synergistic proteolysis of κ-casein into para-κ-casein. However, over prolonged storage, hydrolysis of β-casein and αS-casein increased in P4 and P10 samples. The RCT of P4 samples increased over time and the coagulum became softer, whereas P10 samples did not coagulate after 48 h of storage. In contrast, the RCT of P1 samples decreased over time and a firmer coagulum was obtained, possibly due to a lower rate of hydrolysis of β-casein and αS-casein. Increased levels of protease could result in further hydrolysis of caseins, affecting the processability of milk over storage time.

Impact of Bovine Diet on Metabolomic Profile of Skim Milk and Whey Protein Ingredients

The influence of bovine diet on the metabolome of reconstituted skim milk powder (SMP) and protein ingredients produced from the milk of cows fed on pasture or concentrate-based diets was investigated. Cows were randomly assigned to diets consisting of perennial ryegrass only (GRS), perennial ryegrass/white clover sward (CLV), or indoor total mixed ration (TMR) for an entire lactation. Raw milk obtained from each group was processed at pilot scale, to produce SMP and sweet whey, and SMP was further processed at laboratory scale, to yield ideal whey and acid whey. The total amino acid composition and metabolome of each sample were analyzed, using high-performance cation exchange and a targeted combination of direct-injection mass spectrometry and reverse-phase liquid chromatography–tandem mass spectrometry (LC–MS/MS), respectively. The nitrogen composition of the products from each of the diets was similar, with one exception being the significantly higher nonprotein nitrogen content in TMR-derived skim milk powder than that from the GRS system. Total amino acid analysis showed significantly higher concentrations of glycine in GRS- and CLV-derived sweet whey and acid whey than in those from TMR. The cysteine contents of CLV-derived ideal whey and acid whey were significantly higher than for TMR, while the valine content of GRS-derived acid whey was significantly higher than TMR. The phenylalanine content of GRS-derived ideal whey was significantly higher than that from CLV. Metabolomic analysis showed significantly higher concentrations of the metabolites glutamine, valine, and phosphocreatine in each ingredient type derived from TMR than those from GRS or CLV, while the serine content of each GRS-derived ingredient type was significantly higher than that in TMR-derived ingredients. These results demonstrate that the type of bovine feeding system used can have a significant effect on the amino acid composition and metabolome of skim milk and whey powders and may aid in the selection of raw materials for product manufacture, while the clear separation between the samples gives further evidence for distinguishing milk products produced from different feeding systems based on LC–MS/MS.

Application of chemometrics for detection and modeling of adulteration of fresh cow milk with reconstituted skim milk powder using voltammetric fingerpriting on a graphite/ SiO2 hybrid electrode

In the present work, an analytical approach for the voltammetric detection and prediction of adulteration of fresh cow milk with reconstituted skim milk powder is developed. After precipitation of milk proteins upon addition of ethanol and centrifugation, the supernatant liquid of the samples was analyzed by cyclic voltammetry on a novel graphite/SiO2 hybrid working electrode (GSiHE) using LiClO4 as electrolyte. Under these conditions, fresh milk samples gave broadened peaks/plateaus in both forward and backward potential scanning, attributed mainly to oxidases. Such peaks were not evident in the case of reconstituted skim milk powder samples due to inactivation of enzymes and breakdown of certain antioxidants caused by heat and pressure-treatments. The differences between fresh and reconstituted skim milk powder samples in their voltammetric profile were exploited for the detection of fresh milk adulteration by submitting voltammetric data to chemometrics. As datapoints, the differences between forward and backward current values, recorded at the same potentials, were determined and submitted to multivariate analysis. Principal Component Analysis (PCA) provided a clear differentiation between fresh milk and reconstituted skim milk powder samples. Soft independent modeling of class analogy (SIMCA) was employed to model the class of fresh milks, using samples from 12 commercially available fresh milk brands. Prediction of fresh milk adulteration with reconstituted skim milk powders was achieved by means of Partial Least Squares (PLS) regression analysis. Detection limit of the technique was found to be below 6% (v/v) and the linearity of model in terms of observed/predicted values was confirmed up to 100% (v/v). Validation and applicability of both SIMCA and PLS models were confirmed using a suitable test set, consisting of commercial fresh milk and skim milk powder samples as well as synthetic adulterated fresh milk samples.

Utilisation of water extract of green chilli pepper in the manufacture of low‐fat fresh cheese

The effect of the water extract of green chilli pepper (WECP) on some properties of low‐fat fresh cheese was studied. Cheese was manufactured from a mixture of reconstituted skim milk powder, whey protein concentrate and sodium chloride and fortified with WECP at concentrations of 0, 1, 2 and 3%. The addition of WECP significantly decreased the total and lactic acid bacteria counts as well as the yeasts and moulds counts in the fortified cheeses. The flavour was improved in cheeses made using 1 and 2% WECP, and the cheese manufactured with 2% WECP had the highest flavour and total scores.

Antithrombotic Activity of Milk Protein Hydrolysates by Lactic Acid Bacteria Isolated from Commercial Fermented Milks

ABSTRACT In the last decade, thrombosis has been one of the pathologies with high incidence creating great concern in Health Institutes all around the world. Considering this, the aim of this research was to determine the antithrombotic activity of peptides released during lactic fermentation. Reconstituted skim milk powder was fermented by Lactobacillus casei Shirota and Lactobacillus johnsonii LA1 isolated from commercial fermented milks. The hydrolysis degree and proteolytic profile were analyzed by trinitrobenzenesulfonic acid spectrophotometry method and by peptide polyacrylamide electrophoresis gel separation. The milk fermented by Lactobacillus casei Shirota exhibited a higher concentration of free amino groups than that fermented by Lactobacillus johnsonii LA1. Additionally, in both fermentation systems peptides with molecular weights lower than 1.4 kDa were observed. The highest inhibition of thrombin (31.67±2.35%) was observed in milk fermented by Lactobacillus johnsonii LA1 at 10 hours of fermentation. Finally, no relationship was found between the antithrombotic capacity and the proteolytic profile.

Effect of sonication on the viscosity of reconstituted skim milk powder and milk protein concentrate as influenced by solids concentration, temperature and sonication

Skim milk powder (SMP) and milk protein concentrates (MPCs) are manufactured by evaporation followed by spray drying and are widely used as functional and nutritional ingredients. This study investigated the effects of temperature (40–60 °C) and total solids content (TS) on the viscosity of reconstituted MPC (rMPC) (≥30% TS) and SMP (rSMP) (≥46% TS) in laboratory conditions. Additionally, the influence of sonication in batch (70% amplitude) and flow through systems (90% amplitude) was studied in a laboratory setting. The viscosity increased for all treatments with an increase in TS and decreased with an increase in temperature. Overall, sonication in both batch (30 s) and flow through systems (10.1, 20.2, and 30.2 s) resulted in significant decreases in viscosity for both rSMP and rMPC. An increase in viscosity was observed after post-sonication circulation; however, the viscosity did not return to the pre-sonication values.

Physicochemical and sensory properties of yogurts containing sacha inchi (Plukenetia volubilis L.) seeds and β-glucans from Ganoderma lucidum

Dairy products have been widely used for adding various biomolecules with the aim of improving their functional properties and health benefits. In this study, the physicochemical properties and sensory acceptance of yogurts enriched with sacha inchi (Plukenetia volubilis) seeds (SIS) and β-glucans from Ganoderma lucidum (BGGL) were investigated. The angiotensin-converting enzyme-inhibitory activity of some yogurt samples was also evaluated. Yogurts were produced from reconstituted skim milk powder, and SIS (4% wt/wt) and BGGL were added at different concentrations (0-1.5% wt/wt). The fermentation kinetics were not affected by the enrichment process. The addition of SIS and BGGL significantly increased the contents of protein, fat, carbohydrates, ash, total solids, aspartic acid, serine, arginine, glycine, threonine, tyrosine, and alanine. α-Linolenic (49.3%) and linoleic (32.2%) acids were the main fatty acids found in the enriched samples, whose values were about 50- and 25-fold higher than those of the control yogurt. The textural parameters (firmness, consistency, cohesiveness, and index of viscosity) of the enriched yogurts were significantly lower than those of the control samples during the whole storage period. All enriched yogurts showed a sensorial acceptance higher than 70% by untrained panelists. The angiotensin-converting enzyme-inhibitory activity of some selected yogurt samples ranged between 36 and 59%. These results indicate that SIS and BGGL could be used as natural ingredients for improving the nutritional value of yogurt and fermented milks.

Quantitative Microstructure Analysis of Casein Network Dynamics using STED Microscopy with Relation to Macroscopic Gel Properties

Casein proteins are the main structural element in many fermented dairy products. Understanding how protein functionality is affected during modern food processing, such as filtration and spray drying, is key to product and process optimization. Advances in Super Resolution Microscopy have provided novel tools to investigate protein microstructures. Herein, Stimulated Emission Depletion (STED) Microscopy has been used to image casein micelle aggregation, gel formation and network coarsening over time. Protein structures have been resolved to > 100 nm. Native skim milk and reconstituted skim milk powder were used to produce gelled systems. Gelation was induced either through rennet addition and acidification with GDL. Images have quantitatively analyzed to monitor the development of casein network over time, and the fractal dimensions of the different systems have been determined. Label free Coherent Anti-Stokes Raman Spectroscopy (CARS) Microscopy was used to verify that the presence of fluorophore did not interfere with the gelation process during STED microscopy. Image data has been directly correlated with dynamic texture analysis.We demonstrate the ability to resolve casein micelle structures on the scale of a single micelle, and extract valuable information that directly relates to the macroscopic properties of a gelled system. This work provides the basis for the use of STED microscopy to analyze other colloidal structures. We present a framework to extract meaningful information that directly relates to the macroscopic properties and functionality of the system.

Predicting lactulose concentration in heat-treated reconstituted skim milk powder using front-face fluorescence

Industrial processing of milk and dairy foods requires heat treatment, which induces undesirable effects in milk such as protein denaturation, organoleptic and nutritional properties alteration, browning, etc. The hypothesis of the present study is that it is possible to use front-face measurement of fluorescent markers such as tryptophan, dityrosine, Maillard intermediate compounds and riboflavin as an inline, cheap, easy and fast way to evaluate lactulose formation in milk. Thus, the specific objective of this study was modeling the kinetics of lactulose formation during heat treatment of milk as well as evaluating the correlation of lactulose concentration with fluorescent markers in order to obtain prediction models of lactulose concentration in heat-treated milk based on front-face fluorescence.Three replicates of the study were performed at three different temperatures (80, 90 and 100 °C) and six different times (0, 10, 15, 30, 45 and 60 min). Standard, low-heat, spray-dried skim milk powder, supplied by Chr. Hansen SL (Barcelona, Spain) was reconstituted at 12% and used in all trials to ensure consistency among the various experimental trials.Lactulose concentration was significantly correlated (P < 0.001) with fluorescence intensity of different markers such as maximum intensity and maximum emission wavelength of tryptophan as well as the fluorescence intensity of riboflavin. Fluorescence changes associated to thermal treatment of milk were characterized and a series of fluorescent markers were identified as predictors allowing prediction of lactulose concentration with an R2 of 0.91 at a temperature of 90 °C.

Effect of Tween 80 on Conjugated Linoleic Acid Production by Lactobacillus Strains in Reconstituted Skim Milk Powder

Effect of Tween 80 on Conjugated Linoleic Acid Production by Lactobacillus Strains in Reconstituted Skim Milk Powder

Textural Properties of Acid Milk Gels: Effects of Dairy Protein Powder Rehydration State

In this study, the effect of dried dairy ingredient rehydration state on the textural properties and microstructure of acid milk gels was investigated. The control acid gel samples were made with 12% w/w of reconstituted skim milk powder. Milk base was enriched with whey protein isolates and/or micellar casein powders. Different rehydration times (5, 120, 240, 1,440 min) were considered before studying gel textural properties. This study showed that acid milk gels made with whey instead of casein resulted in an increase in firmness, gel strength, graininess but a decrease in syneresis susceptibility. Nevertheless, rehydration duration of casein powder in contrast to that of whey powder strongly altered the physical properties of the obtained acid milk gels. Moreover, prolonged hydration resulted in enhanced textural properties and decreased syneresis. Practical Applications Commercial preparation of yogurt involves different processing steps. Among them, protein fortification of the milk appears as a crucial step that attributes toward the change in textural properties. Milk protein powders are frequently dried in order to stabilize and transport. This is the reason why rehydration is an essential quality attribute of the powder. Consequently, rehydration is often realized by the industry before use and for a long time. This study showed that acid milk gels made with whey instead of casein resulted in an increase in firmness, gel strength, graininess but a decrease in syneresis susceptibility. Rehydration duration of casein powder in contrast to that of whey powder strongly altered the physical properties of the obtained acid milk gels. Prolonged hydration resulted in enhanced textural properties and decreased syneresis. These aspects are of high significance in the preparation of dairy products, i.e., different types of set and stirred yogurts.