Denaturation and aggregation of whey protein have been extensively studied but there is limited knowledge of their effects on processing properties of infant milk formulae (IMF) systems. In this study, the separate effects of denaturation and aggregation of whey protein on the physicochemical characteristics during processing of a model IMF were examined. Whey protein solutions (8%, w / w , protein) were pre-heated for 2 min at 72 or 85 °C, followed by addition of 2.2 mM calcium (Ca) (H-BCa), or at 85 °C after addition of the same level of Ca (H-ACa), to give pre-treated whey protein for inclusion in three model IMF systems, encoded as H-72-BCa, H-85-BCa and H-85-ACa, respectively. Unheated control samples without (UH-C) and with (UH-C-Ca) added Ca were also prepared. Model IMF systems (5.2%, w / w , protein, 60:40 whey protein:casein ratio, pH 6.8) were then prepared incorporating these pre-treated whey protein ingredients and subjected to lab-scale high-temperature short-time (HTST) heating at 85 °C for 2 min; whey protein denaturation was >81.2% in all samples after HTST. Aggregation of whey protein resulted in a significantly ( P < 0.05) higher viscosity in sample H-85-ACa (8.3 mPa.s) compared to UH-C (4.0 mPa.s), and measurement of Ca ion concentration on heating showed that Ca ions enhanced whey protein aggregation, resulting in larger mean protein particle size. The results also suggest that pre-heating of whey protein had a preventative effect on aggregation of protein during HTST of IMF. This study clearly showed that aggregation is more influential than denaturation in determining viscosity development during HTST treatment of IMF, and that such viscosity development can be controlled by altering protein-protein interactions using, for example, pre-heat treatment of whey protein ingredients.
Progressive loss of solubility of high-protein dairy powders is an unsolved issue in the dairy industry. Recent research has found that the solubility loss of powders is mainly contributed by the loss of dissociability of casein micelles from the parent powder particles. One of the ways of maintaining solubility of powders is to reduce the rate of development of association between casein micelles, by introducing spacers between the micelles. In this work, feasibility of using lecithin nanovesicles (produced by microfluidization) as spacers to improve solubility of protein-rich dairy powders was investigated. Nanostructured high-protein dairy powders were manufactured by adding 1, 5 and 10% w / w (of the total solids) nanovesicle (~82 nm) dispersions to MPC80 suspensions and spray drying at 160 °C inlet and 75 °C outlet air temperature. The powders obtained were stored at 25 or 4 °C and 0.23 water activity and analysed for solubility loss during storage. The biggest effect of addition of lecithin nanovesicles on solubility was seen after 90 days of storage at 25 °C. Addition of nanovesicles at a level as low as 1 and 5% w / w (of the total solids) could improve the solubility of MPC80 by 13 and 30%, respectively during storage at 25 °C for 90 days. As expected, the solubility of all powders did not change much during 180 days of storage at 4 °C and remained above 90%.
Few data are available concerning the composition of biofilms found at the surface of filtration membranes, which, to some extent, explains the long-term failure of numerous strategies developed to control biofouling. This preliminary study intended to design a metagenomic tool targeting the 16S rRNA gene in order to unravel a general portrait of bacterial communities found on spiral-wound membranes used in the dairy industry. A total of seven spiral-wound membrane elements (ultrafiltration, nanofiltration, or reverse osmosis) at the end of their useful lifetimes were collected from different dairy plants. Targeted analysis of the 16S rRNA genes of the metagenome extracted from the membranes revealed their bacterial diversity via high-throughput sequencing technology (Miseq, Illumina). It was found that the nature of the filtered fluid (milk, whey, water) explained 58.6 % of the variance observed between communities found on membranes. Treatments applied on dairy fluids (milk pasteurization, whey bleaching or whey ultrafiltration) induced a selective pressure that affected the diversity of bacterial communities found on membranes and the proportions of spore-former bacteria among them. This work provides the first complete bacterial portrait of the biofilm composition of spiral-wound membranes used in the dairy industry. It suggests that the nature of the filtered fluid and potentially filtration operating parameters may be important elements to consider in order to design new cleaning strategies or preventive measures targeting biofouling.
Heat treatment of concentrated milk systems for preservation and long shelf life or at least a sufficient removal of food pathogens prior to spray drying is a crucial step due to the decreasing stability of these systems toward heat compared to unconcentrated milk. Heat-induced coagulation is observed when temperature-time combinations for the achievement of certain microbial inactivation effects are higher than the heat and colloidal stability of the concentrated milk system allows. In this work, the effects of direct steam injection on the stability of casein micelles in concentrated skim milk (CSM) of 18, 23, and 27% total non-fat solids, heat-treated by direct steam injection (DSI), were investigated. Quantitative differential centrifugation for the separation of aggregates, casein micelles, dissociated submicellar particles, and soluble proteins and subsequent analysis of caseins and whey proteins within these fractions by RP-HPLC were applied. Quantitative separation was monitored by particle size measurements. The dissociation of κ-casein as well as an increase in casein micelle hydrodynamic radius were observed to increase with increasing total solid content of CSM, heat treatment time, and temperature. Heat-induced dissociation of β-Lg-κ-casein complexes at a critical level of 30–35% was found to induce severe coagulation of κ-casein-depleted calcium-sensitive casein micelles in CSM heated by DSI. Dissociated and aggregated proteins were found to be present as distinct colloidal particle classes differing in size from casein micelles.
Protein type and/or heat treatment pre- or post-homogenisation can affect the physical stability of infant formulations during manufacture. Previous research has described the use of α-lactalbumin addition in infant formulae, but has not demonstrated the effect of heating pre- or post-emulsion formulation during processing. The objective of this study was to evaluate the effect of both of these parameters. Three batches of model 1st-stage infant formula containing differing whey protein ratios (60:40 whey: casein with α-lactalbumin content 12, 30 or 48% of total protein) were prepared. Each batch was split; one half receiving heat treatment pre-homogenisation and the second half homogenised and then heat treated. Emulsion stability was determined by size exclusion chromatography, SDS-PAGE, particle size and viscosity measurements. There was a significant (P < 0.05) reduction in the formation of large soluble aggregates upon increasing α-lac concentration in emulsions heat treated either before or after homogenisation. Heat treatment of formulations post-homogenisation resulted in a higher (P < 0.05) D.v09 within the particle size distribution; increasing α-lactalbumin concentration to 30 or 48% significantly (P < 0.05) reduced the D.v09 within the particle size distribution in these emulsions. The viscosity of concentrates (55 % total solids) containing the 12% α-lactalbumin, heat treated post-homogenisation, was significantly greater (P < 0.05) than the equivalent emulsion heat treated pre-homogenisation; increasing the α-lactalbumin concentration to 30 or 48% significantly (P < 0.05) reduced viscosity. When the α-lactalbumin content was increased to 48% as a percentage of the total protein, heating before or after emulsion formation had no effect on concentrate viscosity. The findings demonstrate the importance of thermal denaturation/aggregation of whey proteins (and in particular, the ratio of α-lactalbumin to β-lactoglobulin) prior to homogenisation of infant formula emulsions.
Implementation of reverse osmosis filtration at the dairy farm will reduce the volume of milk, which has to be transported, and thereby potentially reduce energy consumption and CO2 emission. The aim of this study was to examine the quality of whole milk powder produced from reverse osmosis retentate concentrated at the farm. Whole milk powder prepared from reverse osmosis retentate, with a volume concentration factor of 2, was compared to powder from non-concentrated milk, as well as to a range of commercial whole milk powders. A storage experiment of the stability of retentate powder for up to 12 months at room temperature was conducted and evaluated for quality parameters, including proteolysis, oxidation, furosine and colour. The results showed that concentration of the oxidation products hexanal, heptanal and nonanal increased during storage of both retentate powder and powder from non-concentrated milk, but not to a higher extent than found in commercial powder of similar storage conditions. Detectable furosine was higher in powder prepared from non-concentrated milk than that in powder from pre-concentrated milk, and further no changes in colour was found during storage. However, high variation in powder composition between produced powders, especially with regard to moisture content, could have affected some quality parameters. In conclusion, pre-concentrating milk by reverse osmosis at the farm did not have significant effects on the overall quality of the produced milk powders in this study.
Dispersibility is a key quality variable for instant whole milk powder (IWMP) measured manually using a complex and laborious dissolution method post-production. Consequently, the lack of timely feedback means that the functional quality cannot be controlled in real time. This work proposes the idea of applying a simpler, surrogate measurement that can be implemented in the plant in order to have useful real-time information regarding the quality of the product being produced. This, we term, is a proxy measurement. The functional property dispersibility was used as a case study, with particle size being investigated as a proxy at an industrial IWMP plant. It was found that particle sizing could be used to provide useful information regarding the powder, with the proxy measurement being able to predict in-specification powder 97% of the time. Although the test was not as effective for predicting out-of-specification results, with a false-positive rate of 50%, the fact that out-of-specification events are rare in the industry setting means that the overall proxy measurement is still between 78 and 87% accurate and thus useful for predicting the dispersibility quality of the IWMP. Furthermore, these proxy measurements can then be combined with on-line plant information using multivariate techniques to further improve their accuracy and understand how the quality can be controlled by changing the plant processing conditions.
The present work studied the rehydration properties of milk protein concentrates (MPCs), prepared using ultrafiltration (UF) and diafiltration (DF). Milk was acidified to pH 6 with glucono-δ-lactone (GDL) prior to UF to alter the mineral composition of the final concentrates. The particle size distribution and the microstructure of the casein micelles in reconstituted MPCs as well as the partitioning of calcium, phosphate, and proteins between the colloidal and soluble phases were investigated. Reconstituted samples analyzed by electron microscopy showed that, even in partially dissolved particles, the particle surface was porous and similar to its inner portion and had no distinct skin layer. Partial acidification of milk did not have any significant effects on the microstructure; however, it significantly increased the average diameter of the casein micelles for both UF and DF samples and decreased the concentration of total calcium and phosphate. Sodium dodecyl sulfate (SDS)-PAGE analysis of the centrifugal supernatants of reconstituted MPC demonstrated that the amount of soluble caseins present in milk concentrates dramatically increased with acidification, and it further increased after restoring the mineral composition of the serum phase through dialysis against milk. This work contributes to a better understanding of how processing conditions, particularly partial acidification of milk prior to concentration, can alter the composition and physical properties of the caseins and the soluble phase of MPC after rehydration. Such alterations can significantly impact the technological properties of the reconstituted MPC.
Time temperature integrators (TTIs) are useful tools in estimating the heat load applied on differently processed dairy products. The objective of this study was to analyze and assess three TTIs – lactulose, furosine, and acid-soluble β-lactoglobulin (β-Lg) – in 70 high heated dairy products at retail in Austria and Germany comprising whipping cream, coffee cream/milk, and condensed milk products. While β-Lg was not appropriate to evaluate the heat load of these products, furosine and especially lactulose increased with rising intensity of heat treatment, and are appropriate to distinguish between several heating categories analyzed. Pasteurized ( n = 8) and “heat treated” ( n = 5) whipping cream samples showed lowest furosine (48 ± 14/ 45 ± 19 mg.100 g −1 protein) and low lactulose (29 ± 10/57 ± 28 mg.L −1 ) concentrations, followed by ESL whipping cream ( n = 10), ESL coffee cream ( n = 1), and UHT whipping cream ( n = 10) (furosine = 72 ± 37/71/161 ± 30 mg.100 g −1 protein; lactulose = 56 ± 41/161/195 ± 39 mg.L −1 ), respectively. Sterilized condensed milk samples ( n = 14) showed the highest concentrations of both TTIs and could be clearly separated from UHT treated samples ( n = 5) (furosine = 491 ± 196/216 ± 46 mg.100 g −1 protein; lactulose = 1997 ± 658/409 ± 161 mg.L −1 ), whereas the so-called heat-treated samples ( n = 9) had a heat load in between showing an extreme range of variation for both TTIs.
The presence of gas-producing clostridia in ewe’s milk can lead to the occurrence of late-blowing defects in cheeses. However, data on this aspect are limited. In the present study, using the most probable number (MPN) method, clostridial spores were enumerated in 527 ewe’s milk samples collected in the Grosseto Province (Tuscany, Italy) from autumn 2014 to summer 2015. In addition, using polymerase chain reaction (PCR), we identified the species most frequently involved in late-blowing defects in cheese ( Clostridium tyrobutyricum , Clostridium butyricum , Clostridium beijerinckii , and Clostridium sporogenes ), and of Clostridium perfringens . Gas-producing clostridial spores were detected in 99% of samples. Spore concentrations ranged from 360 to more than 110,000 spores∙L −1 . We observed that 86% of samples had a spore load higher than 1000 spores∙L −1 . During autumn and summer, spore concentrations were significantly higher than in winter and spring ( P < 0.001). A total of 222 isolates obtained from 77 MPN positive tubes from different milk samples were subjected to PCR. Colonies from 63/77 (82%) MPN positive tubes were taxonomically identified. Among the 63 PCR-positive samples, C. perfringens was the most frequently detected species (56%), followed by C. sporogenes (44%), C. tyrobutyricum (7.9%), C. butyricum (1.6%), and C. beijerinkii (1.6%). In addition, in 11% of the MPN positive tubes, at least two clostridial species were found to be present simultaneously. This work highlights the presence of clostridial spores in ovine milk from central Italy (Tuscany) and led to the identification of some of the clostridia species involved in such high spore loads.
Chal is a traditional fermented product produced from spontaneously fermented camel milk which contains several bacterial species with potential usage in producing traditional dairy products and functional foods. The aims of this study were to isolate and identify predominant lactic acid bacteria (LAB) from Chal and investigate antioxidant activity of camel and bovine milk fermented by these isolates. Chal samples were collected from Turkman Sahra, Golestan Province, Iran. The protein hydrolysis was determined by o-phthaldialdehyde (OPA) method, and antioxidant activities of whey fractions were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals scavenging methods. Nine catalase-negative bacteria including Lactobacillus ( L. ) plantarum , L. paraplantarum , L. kefiri , L. gasseri , L. paracasei , Leuconostoc ( Leu. ) lactis , Weissella ( W. ) cibaria , and Enterococcus ( E. ) faecium were isolated and identified by conventional and molecular methods. Both camel and bovine milk were fermented by the strains for 24 h. Fermented camel milk showed significantly ( P < 0.05) higher antioxidant activity than bovine milk. Camel milk fermented by Leu. lactis showed significantly ( P < 0.05) higher DPPH (57.90 ± 4.59 μM) and ABTS (1484.35 ± 128.20 μM; P < 0.05) radical scavenging activity compared to samples fermented by other strains. According to sensory evaluation of fermented camel and bovine milks, camel milk fermented by Leu. lactis SM10 had the highest overall acceptance values. Our findings suggest that camel and bovine milk fermented by LAB isolated from Chal could potentially be used for producing novel functional foods.
The acquisition of prtS by Streptococcus thermophilus strains allowed hydrolysis of caseins into peptides and then to increase their growth in milk. This leads to faster milk acidification, which is important in dairy industry. However, some strains harboring the same allele of prtS present different acidification rates, which could be explained by a difference in the regulation of prtS expression. We chose two strains with the same allele of prtS (including the same promoter region): one, PB302, is with high acidification rate while the other, PB18O, is without. They exhibited similar growth in M17, but not in milk, where PB302 showed better growth. The expression of prtS and activity of PrtS were lower in PB18O, in the two media tested. We demonstrated that other genes known to be involved in carbon and nitrogen metabolism were overexpressed in PB302. Interestingly, these genes were overexpressed in milk compared to M17. Nearly all these genes possessed a putative CodY-box in their promoter region. Taken together, difference of gene expression detected in PB302 between milk (low-peptide medium) and M17 (rich-peptide medium) and presence of a putative CodY-box is a feature of the transcriptional pattern of CodY-regulated genes. Altogether, our results propose that acquisition of prtS is not enough in certain strains to achieve rapid milk acidification. High transcriptional level of dtpT, amiF, ilvC, ilvB, bcaT, livJ, ackA, codY, and prtS in fast acidifying strain suggests that this transcriptional pattern could be required for fast milk acidification in Streptococcus thermophilus.
Milk proteins contained encrypted in their sequence biologically active components that can be released by enzymatic hydrolysis. Among the biological activities recognized in milk components, the antioxidant activity is of great interest. The objective of the present study was to analyse the antioxidant properties of whole, semi-skimmed and skimmed milk during simulated gastrointestinal digestion and to identify the compounds responsible for the antioxidant activity. Simulated digestion increased the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) + radical scavenging activity of milk. In digested whole milk, the main contribution to ABTS + radical scavenging activity was due to high molecular weight fraction (>3 kg.mol −1 ). For semi-skimmed and skimmed milk, the main contribution was due to low molecular weight fraction (<3 kg.mol −1 ). Twelve major peaks were collected from low molecular weight fraction of digested skimmed milk by reversed-phase high-performance liquid chromatography and evaluated for their ABTS + radical scavenging activity. Among the different fractions, three (F2, F3 and F5) showed high ABTS + and hydroxyl radical scavenging activity and lipid peroxidation inhibitory capacity. The compounds (free amino acids and peptides) present in these fractions were identified with nano-LC-QTOF MS/MS analysis. The amino acids tryptophan and tyrosine seemed fundamental in the ABTS + and hydroxyl radical scavenging capacities whereas the amino acids phenylalanine and histidine played an important role in the lipid peroxidation inhibitory activity of the peptides. The results reported in this study suggested that milk proteins could act as a carrier for the delivery of antioxidant compounds in the gastrointestinal tract possibly protecting the gastrointestinal tract itself from the oxidative damage.
For its nutritional composition, donkey milk is an excellent alternative to breast milk for infants suffering from cow’s milk allergies. Even in donkeys, a passage of aflatoxin from contaminated feed to milk could occur, as reported by many authors in other dairy species, but there are no studies on this topic. This work was aimed at studying the excretion of aflatoxin M1 (AFM1) and M2 (AFM2) in milk after feeding trials with contaminated feed. Six donkeys, at the end of lactation, received a diet with naturally contaminated corn containing 202 and 11 μg.kg −1 of aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2), respectively. Individual milk samples were analyzed for AFM1 and AFM2 for 15 days after the contaminated feed administration. Amounts of AFM1 and AFM2 were detected in the milk. The steady state condition was reached after 6 days. No AFM1 or AFM2 were detected in milk after 28 h from the last contaminated feed administration. The carryover from AFB1 to AFM1 and from AFB2 to AFM2 was found to be 0.02 and 0.31%, respectively. The results obtained in this study are thus a further step toward understanding the possible carryover of aflatoxin in donkey milk.
Currently, donkey milk is receiving an increasing attention from consumers and research community because of its several beneficial aspects, such as a poor allergenic nature and a remarkable antimicrobial compound content. In this study, we evaluated the growth rate of Staphylococcus aureus ATCC 6538, Listeria monocytogenes ATCC 7644TM, Campylobacter jejuni ATCC 33291, and Pseudomonas aeruginosa ATCC 27853 at refrigeration conditions (4 ± 2 °C) in goat milk added with different percentages of donkey milk (1, 2.5, 5, 10% v / v ) along 6 days of storage; furthermore, donkey milk and goat milk samples were employed as controls. Lysozyme content of donkey milk was determined and ranged from 1 mg.mL −1 up to 2 mg.mL −1 . An inhibited growth rate in donkey milk samples was observed during storage for S. aureus , L. monocytogenes , and C. jejuni , with a growth decrease of 0.61 log CFU.mL −1 , 5.55 log CFU.mL −1 , and 1.72 log CFU.mL −1 , respectively. These data confirm the antibacterial activity of donkey milk against Gram-positive and Gram-negative microorganisms; however, microbial growth rates in milk mixtures and goat milk were comparable, with no significant increase in antibacterial activity due to donkey milk addition. Considering a potential employment of donkey milk in dairy products, further studies should be performed in order to detect the optimal balance of milk mixtures in terms of caseins and antimicrobial molecules amounts.
The source of microbiological contamination of whey protein concentrate (WPC), a quality problem for the dairy industry, has not been thoroughly investigated. The objectives of this study were to identify the bacteria isolated from whey protein concentrate containing 80% protein (WPC 80) and determine their ability to form biofilms as a potential source of contamination in a whey processing line. Six Bacillus species including (percentage of isolates in brackets) Bacillus licheniformis (67%), Bacillus cereus (19%), Bacillus thuringensis (4%), Bacillus subtilis (4%), Bacillus pumilus (4%) and Paenibacillus glucanolyticus (2%) were identified based on BLAST databases in six different WPC80 batches. B. licheniformis was the predominant isolate. B. licheniformis are thermo-tolerant bacteria with the ability to form biofilm. This biofilm is a potential source of microbial contamination of product, resulting in microbial specification limits being exceeded. Spoilage of product may result from the metabolic products, such as enzymes, produced by these biofilms.
Lactose-free dairy products become increasingly important for lactose-intolerant consumers, but there are only few studies concerning the rheological properties of fermented dairy products from lactose-hydrolysed milk. Hydrolysation was performed with commercial β-galactosidase either before or during fermentation (co-hydrolysis). In each trial, fermentation of the base milk was carried out simultaneously using the same starter cultures for (a) untreated milk (reference) (b) hydrolysed milk as substrate and (c) by performing lactose hydrolysis and fermentation simultaneously (co-hydrolysis). In total, five thermophilic starter cultures and two products (yoghurt and Greek-style yoghurt) were investigated. Results show that the influence of hydrolysis of lactose on the properties of the fermented dairy products strongly depends on starter culture and substrate. For starters C and D, apparent viscosity (extracted from flow curves at a shear rate of 75 s −1 ) of fermented milks was only marginally affected by lactose hydrolysis, ranging between approx. 0.34–0.31 and 0.37–0.31 Pa.s, respectively. Hydrolysed products from starters A and E exhibited significant lower apparent viscosity (0.16 and 0.24 Pa.s) compared with their respective references (0.29 and 0.35 Pa.s). Fermentation of both substrates (regular yoghurt, Greek-style yoghurt) with starter B resulted in a decrease of yield stress and apparent viscosity because of lactose hydrolysis only for Greek-style yoghurt. Furthermore, a trend towards higher EPS synthesis was found when using hydrolysed milk. The results clearly show that products made from lactose-hydrolysed milk with similar rheological properties as the reference product can be obtained but that there is a lack of information concerning the complex interactions between starter culture and milk substrate.
In this paper, we propose a feasible, sample preparation free and fast validated methodology for the detection and quantitative analysis of Minas Frescal cheese waste whey as an adulterant in raw milk using mid-infrared spectroscopy with Fourier transform (FTMIR) along with the chemometric technique of partial least squares (PLS). The PLS model was built in accordance with Brazilian and international guidelines and was analytically validated through the estimate of figures of merit parameters, in accordance with ASTM E1655-05 standard. This model showing an effective and feasible method for quality control of raw milk can be adopted for the quality control by regulatory agencies, as shown by the satisfactory results obtained for all estimated figures of merit with no systematic errors and low errors, with R=0.99.
The synthesis of bile salt hydrolase has been linked to the health benefit of Lactobacillus reuteri toward lowering blood cholesterol. The aim of this study was to examine the growth and bile salt hydrolysis activity (BSHA) of L. reuteri NCIMB 30242 during milk fermentation with a yogurt starter. There was little growth of L. reuteri during a 4-h co-fermentation with a yogurt culture, and an inoculation of 4.5 × 10 7 CFU.mL −1 was needed to obtain the 10 8 CFU.mL −1 target in the product. Enrichment of milk with sugars, minerals, or peptone-based ingredients did not improve growth of L. reuteri . Viable counts of L. reuteri above 1.5 × 10 8 CFU.mL −1 generated texture defects. Free and microencapsulated (ME) cultures were tested for BSHA in the yogurt drinks. L. reuteri cells which grew during the 4-h lactic fermentation had 40% less BSHA than L. reuteri added directly via the commercial culture. The BSHA of free cells was apparently three times higher than in the ME culture. This study adds data showing that the yogurt production process could affect the functionality of probiotic bacteria.
Milk is a source of bioactive compounds essential for health and growth of newborns. Donkey milk, rich in lactose and whey proteins, has been proven to be a good breast milk substitute during infancy and adequate nourishment for patients with cow milk protein allergy. Beside, this milk is gaining a growing interest for human nutrition because of some other alleged health benefit. It shows antibacterial activity toward a wide range of Gram-positive and Gram-negative bacteria, stimulates immune system in convalescence, regulates gastrointestinal flora, and prevents inflammatory and autoimmune diseases. As regards its antimicrobial properties, although all the milk components might contribute to this activity, the whey protein fraction of donkey milk is generally believed to play the main role. The aim of this review is to highlight the antimicrobial properties of donkey milk with a special focus on the whey protein fraction. The effects of preservation and processing treatments on whey protein content and antimicrobial activity are also discussed.
