AbstractContamination of raw milk by psychrotrophs can lead to the production of heat-resistant proteases and subsequent spoilage of UHT milk. Therefore, this research communication evaluated the effect of a pre-milking teat disinfectant (active components: L-(+)-lactic acid and salicylic acid) and a liner disinfectant (active components: peracetic acid and hydrogen peroxide) on the number of mesophilic and (proteolytic) psychrotrophic bacteria prior to milking. The teat orifices of 10 cows were sampled using a swabbing procedure before and after treatment with a pre-milking teat disinfectant on six subsequent days. On the teat orifices, there was a small but statistically significant decrease in the psychrotrophic bacterial counts between pre and post dipping. No differences were observed for the mesophilic bacterial counts and proteolytic active counts. Liners were also sampled using swabs pre and post disinfection. No statistically significant decrease in the bacterial counts was observed post liner disinfection, although there was a numerical decrease. Sixty-two percent of the proteolytic psychrotrophs were pseudomonads: 16.5% of which were P. fragi, 14.3% P. lundensis, 10.0% P. fluorescens and 2.9% P. putida. Trinitrobenzenesulfonic acid (TNBS) analysis revealed a wide variety in proteolytic activity (from 0 to 55 µmol glycine/ml milk) and the presence of high producers. It can be concluded that there was only a minor effect of teat and liner disinfection on the psychrotrophic bacterial counts indicating that the measures presented did not result in a reduction of the targeted bacteria on teat orifices and liners.

The aim of this study was to develop and validate 2 protocols (for use on-farm and at a central location) for the reduction of Mycobacterium avium ssp. paratuberculosis (MAP) in colostrum while preserving beneficial immunoglobulins (IgG). The on-farm protocol was based on curdling of the colostrum, where the IgG remain in the whey and the MAP bacteria are trapped in the curd. First, the colostrum was diluted with water (2 volumes colostrum to 1 volume water) and 2% rennet was added. After incubation (1 h at 32°C), the curd was cut and incubated again, after which whey and curd were separated using a cheesecloth. The curd was removed and milk powder was added to the whey. Approximately 1 log reduction in MAP counts was achieved. A reduction in total proteins and IgG was observed due to initial dilution of the colostrum. After curd formation, more than 95% of the immunoglobulins remained in the whey fraction. The semi-industrial protocol was based on centrifugation, which causes MAP to precipitate, while the IgG remain in the supernatant. This protocol was first developed in the laboratory. The colostrum was diluted with skimmed colostrum (2 volumes colostrum to 1 volume skimmed colostrum), then skimmed and centrifuged (at 15,600 × g for 30 min at room temperature). We observed on average 1.5 log reduction in the MAP counts and a limited reduction in proteins and IgG in the supernatant. To obtain a semi-industrial protocol, dairy pilot appliances were evaluated and the following changes were applied to the protocol: after 2:1 dilution as above, the colostrum was skimmed and subsequently clarified, after which the cream was heat treated and added to the supernatant. To investigate the effect of the colostrum treatment on the nutritional value and palatability of the colostrum and the IgG transfer, an animal experiment was conducted with 24 calves. Six received the dam's colostrum, 6 were given untreated purchased colostrum (control), and 2 groups of 6 calves received colostrum treated according to both of the above-mentioned methods. No significant differences were found between the test groups and the dam's colostrum group in terms of animal health, IgG uptake in the blood serum, milk, or forage uptake. Two protocols to reduce MAP in colostrum (for use on-farm or at a central location) were developed. Both methods preserve the vital IgG.

Sixty-six putative Pseudomonas strains isolated from different food matrices (ready-to-eat vegetables, meat, milk and dairy products) were examined for their phenotypic features and enzymatic spoilage activities. Their genotype was studied by BOX-PCR, Pseudomonas specific 16S PCR, aprX and housekeeping genes sequencing (16S rRNA gene, gyrB and rpoB). The majority of the isolates are very versatile as shown by their wide ranges in growth temperature (4-45 degrees C), pigment production and production of enzymes. The BOX-PCR clustering showed a high genetic diversity among the isolates and phylogenetic analysis of the rpoB gene allowed a first putative identification at the species level. Thirteen isolates were provisionally classified as Pseudomonas gessardii-like, but probably belong to a yet unknown Pseudomonas species in the Pseudomonas fluorescens group.Protease-activity was qualitatively and quantitatively verified. A large variation in proteolytic activity measured in UHT-milk was observed amongst the protease positive isolates. Several isolates provisionally classified as P. gessardii-like showed the highest activities. An aprX gene based phylogenetic dendrogram showed five different groups and two sub-groups, for which a correlation with the matrix of origin could be demonstrated. An insertion of 15 bp was observed in the aprX gene sequences of isolates of mainly dairy origin. (C) 2015 Elsevier Ltd. All rights reserved.

Based on literature data, the composition of milk from different ruminants (cow, sheep, goat, buffalo, camel, llama, yak and deer) and equidae (horse and donkey) and of human milk were compared to examine possible nutritional differences. Additionally, the alleged health benefits attributed to some of these milks and the effect of heating are discussed. Very generally, ruminant milk has a lower lactose content, but a higher protein (and casein), fat (with a higher share of saturated and mono-unsaturated fatty acids and a higher cholesterol level), vitamin (except for vitamin C) and mineral content compared to horse or donkey milk. Milk composition may however vary largely, not only between ruminants and non-ruminants, but also between different breeding variants of the same species and between individual animals. Consequently, a constant health promoting potential is, if present, difficult to guarantee. Moreover, differences in milk composition do not only concern the relative proportions of the milk components, but also occur at the molecular level (e.g. monomeric versus dimeric proteins, different amino acid sequence). Pasteurization is not expected to affect the nutritional (or presumed health) benefits significantly, regardless of differences observed in thermostability between components of considered types of milk. Even though the milk composition of some animal species resembles to a great extent the composition of human milk, it is recommended to give either human milk or formula milk to babies and infants. For people suffering from milk allergy, milk other than e.g. bovine milk may offer a solution, but this greatly depends from one person to another.

We have compiled a dairy powder databank containing a broad range of the most current dairy types. The databank is composed of whole milk powders, skimmed-milk powders, equine milk powders, whey powders, butter milk powders and ass's milk powders. Near infrared reflection spectroscopy (NIRS) calibration models for routine determination of the composition parameters moisture, fat, protein and lactose content and the heat class by means of the whey protein nitrogen index (WPNI) were developed. Very good NIRS calibration models can be obtained for the composition parameters moisture, fat, protein and lactose. The prediction of the WPNI by NIRS is also acceptable (SD/SECV = 3.86 < 4.0). The short-wave NIRS technique is promising for conducting identification and content determination of the main components of milk powder and the heat class. The use of this very fast technique significantly reduces the laboratory work and greatly shortens analysis times. It reduces the amount of solvents required, which also makes it very environmentally friendly.

Mycobacterium avium subspecies paratuberculosis (MAP) inactivation kinetics was studied to assess whether current legislative pasteurization prescriptions are sufficient to reduce this bacterium to an acceptable level in raw milk. To assess possible protective effects of milk components during pasteurization, raw milk and phosphate-buffered saline (PBS) were compared. Analyzing data from three replicate experiments in milk separately gave D60°C-values ranging from 114.3 to 244.5s and z-values ranging from 4.2 to 6.8°C; in PBS the ranges were 162.4 to 353.3s and 4.0 to 9.0°C, respectively. No statistically significant difference was observed between the heat resistance of MAP in milk versus PBS. The currently prescribed minimum HTST pasteurization conditions (71.7°C, 15s) were found to be insufficient to kill MAP in milk in 2 out of 6 replicate experiments, while LTLT pasteurization (minimum 62.7°C, 30min) was effective, based on extrapolation of the inactivation data obtained.

The purpose of the study was to determine the distribution of Mycobacterium avium ssp. paratuberculosis (MAP) across the main milk and colostrum fractions (cream, curd, and whey). Raw milk and colostrum were inoculated with 1 of 2 MAP strains, ATCC 19698 or S-23, yielding initial concentrations of 10(6) to 10(7) cfu/mL. After fractionation, for milk as well as for colostrum, 80 to 90% of the recovered MAP cells were found in the curd fraction and 10 to 20% in the cream fraction. Total MAP colony counts in milk whey were 4 to 5 log(10) units lower than colony counts of inoculated milk. In colostrum, colony counts were 2 to 3 log(10) units lower in whey than in inoculated colostrum. Because of the slow growth of MAP and to proceed more smoothly with set-up and optimization of the method, luminescent MAP strains were used. The high correlation coefficient (r=0.960) between colony counts and luminescence measurements showed that the use of luminescent MAP strains during method development was plausible.

Milk with an increased content of unsaturated fatty acids was obtained by incorporating 60% of extruded linseed into the concentrate of cows. Two groups of Holstein cows (3 animals/group) were fed a concentrate (control or linseed enriched) together with the same roughage diet (ad libitum). After an adaptation period of 3 wk, evening and morning milk samples were collected every 7 d for 3 wk. Milk was decreamed and anhydrous milk fat (AMF) was isolated from the fat fraction by using the Bureau of Dairy Industries method. The objective of this study was to investigate if the crystallization mechanism of milk fat changed when the content of unsaturated fatty acids was increased. Therefore, the crystallization behavior of a milk fat enriched with unsaturated fatty acids was compared with that of a control milk fat. Nonisothermal crystallization was investigated with differential scanning calorimetry, and 1-step and 2-step isothermal crystallization behaviors were investigated using pulsed nuclear magnetic resonance, differential scanning calorimetry, and x-ray diffraction. A higher content of unsaturated fatty acids in AMF resulted in an increased proportion of low melting triglycerides. These triglycerides lowered the solid fat content profile, particularly at refrigerator temperatures. Furthermore, they induced some changes in the crystallization and melting behaviors of milk fat compared with a control AMF, although no fundamental changes in the crystallization mechanism could be revealed. Even though a lower melting point could be observed for milk fat with a higher content of unsaturated fatty acids, a similar degree of supercooling was needed to initiate crystallization, resulting in a shift in onset temperature of crystallization toward lower temperatures. In addition, slower crystallization kinetics were measured, such as a lower nucleation rate and longer induction times, although crystallization occurred in a similar polymorphic crystal lattice. During melting, a shift in offset temperature toward lower temperatures could be observed for the 3 melting fractions of AMF in addition to a higher proportion of low melting triglycerides. These results demonstrate that a higher content of unsaturated fatty acids has some effect on the crystallization behavior of milk fat. This knowledge could be used to produce dairy products of similar or superior quality compared with conventional products by intervening in the production process of dairy products.

This chapter gives a broad overview of the possible spoilage defects in consumer milk, being either of a microbiological nature (e.g. spore formers and Pseudomonas enzymes) or of a chemical nature (e.g. light-induced oxidation). As these defects can be quite specific for, e.g., pasteurised versus ultra high temperature (UHT) treated milk, a detailed description of the mechanisms of spoilage, the main factors (on farm or industry level) influencing this spoilage, and the methods (including emerging methods on farm or industry level) to prevent spoilage, are discussed for different types of consumer milk. Finally, some future trends and further reading advice are given.

Control milk and milk enriched with unsaturated fatty acids (3.3% fat) were heated using an indirect Ultra-high temperature treatment, then stored at 20 degrees C in containers from different packaging materials: glass (no exposure to light), high density polyethylene (HDPE) packaging with light barrier (3-HDPE; no exposure to light) and monolayer HDPE (1-HDPE: 1000 1x). The decrease in antioxidant content and the formation of oxidation products were monitored over three months. For milk stored in I-HDPE packaging, the available antioxidants were Consumed at the same rate for both milk types. suggesting that oxidation is initiated in the serum phase. After depletion of these antioxidants, oxidation products were formed according to the fatty acid profile. When using a light barrier in the packaging, no oxidation products could be detected over three months. (C) 2009 Elsevier Ltd. All rights reserved.

The shelf-life of dairy products is the result of a delicate balance between the activity of anti- and pro-oxidants. During storage, an imbalance between the presence of reactive oxidants and the antioxidant defence mechanism can cause oxidation. The objective of this study was to investigate the added value of methods that measure the antioxidative capacity, such as the ‘Ferric Reducing Antioxidant Power’ (FRAP) and ‘Diphenyl Picryl Hydrazyl’ (DPPH) method, to monitor the sensitivity to oxidation in milk and to compare these methods with the more conventional peroxide value method measuring primary oxidation of the milk fat. For milk exposed to light, the antioxidative capacity of milk serum already decreased during the first days of storage, while the formation of lipid hydroperoxides was detected only after 7 days. Therefore, the FRAP and DPPH methods provide additional information on sensitivity to oxidation, resulting in a more comprehensive view on the concept of oxidation.

The residual proteolytic activity in milk powders can affect the shelf life of products in which they are used. This study examined the proteolytic activity in several skimmed milk powders, which were classified based on whey protein denaturation (WPNI). All high heat powders tested appeared to contain no residual proteases. Only one of the three medium heat powders examined appeared to contain residual proteases, while considerable proteolytic activity was found in all low heat powders. In the low heat powders 85% of the proteolytic activity could be inhibited by aprotinin. This is an indication that it was most likely due to the presence of active plasmin. The residual 15% was probably caused by proteases of bacterial origin. In the medium heat powder containing the active protease the total protein degradation was 8.5 times lower than in the low heat powders and only 50% of this proteolytic activity could be inhibited by aprotinin. It can be concluded that low heat powders in particular still possess considerable residual protease activity and that this fact should be taken into consideration when further processing these milk powders in dairy products with a long shelf life.

The Maillard reaction is a chemical reaction generally initiated by condensation between the ε-amino group of lysine and a reducing sugar. It is a complex reaction which usually occurs during storage and processing of foods. The Maillard reaction results in physical changes, in loss of nutritional available lysine, in the formation of new compounds and leads to brown pigment or melanoidin formation, which affects the colour of the dairy products. The reaction rate is affected by the chemical nature, concentration and ratio of the reactants (8,9), water activity (7), pH (1) and heating time and temperature.

A model for indirect thermal treatment of milk was implemented and applied to three commercial heat exchanger systems: two systems using tubular heat exchangers, albeit very different ones, and a plate type heat exchanger system. The model emphasis was placed on fouling prediction and bacterial inactivation, but other heat induced reactions were also included. The model was able to reproduce the time–temperature profiles satisfactory in all three cases. Some optimisation strategies with respect to fouling minimisation were simulated. For all cases, it was not possible to obtain major improvements using only the available degrees of freedom. However, the model predictions indicate that significant reductions in fouling are possible when applying minor redesigning to the systems. Especially the location of a preholding section proves to be of major importance.

Deterioration due to Maillard reaction, of milk powder upon storage was monitored by capillary electrophoresis, IEF, amino acid analysis and determination of furosine, HMF, browning index and available lysine. In comparison with these other methods, capillary electrophoresis of β-lactoglobulin, revealing a native and a modified fraction of this protein, proved to be a fast, easy and sensitive method for monitoring the quality of milk powders during storage.

ABSTRACT In total, 71 samples of retail raw milk cheeses produced or imported in Belgium and samples of Belgian farmhouse cheeses were examined for cotiforms, β‐glucuronidase positive Escherichia coli, Escherichia coli O157, Staphylococcus aureus, Salmonella spp., Listeria spp. and Listeria monocytogenes. The presence of staphylococcal enterotoxins was investigated on samples with S. aureus counts higher than 103 cfu/g. The incidence of coliforms, β‐glucuronidase positive E. coli and S. aureus was higher in soft than in blue veined, semi‐hard, hard and fresh cheeses. Four mold‐ripened soft cheeses were positive for E. coli O157. One of the 4 cheeses was positive for verotoxin VT2. Staphylococcal enterotoxins were detected in 1 soft redsmear cheese, which was positive for L. monocytogenes. L. monocytogenes was also detected in one fresh cheese. Salmonella was not detected in any of the 71 raw milk cheeses.

carbohydrates; enzymes; esterases; europe; food-industry; globulins; hydrolases; industry; oligosaccharides; oxidoreductases; processing; proteins; reducing-sugars; sugars; western-europe

A method is presented for the evaluation of the keeping quality of milk powders as a result of heating and storage conditions. Capillary electrophoresis of β-lactoglobulin reveals a native and a modified fraction of this protein. The modifications are a result of Maillard reaction, changing the apparent pI of the polypeptides and are due to heating and storage conditions. This change in pI is related to lysine damage and nutritional availability of this essential amino acid. Capillary electrophoresis allows a fast and easy determination of the ratio of native (unmodified) to total β-lactoglobulin for monitoring storage conditions of milk powders.

Ice-cream containing probiotic bacteria was produced by mixing fortified milk fermented with probiotic strains with an ice-cream mix, followed by freezing.Four different strains of probiotic bacteria were used. Each strain was grown (37 degrees C, 12 h) in UHT semi-skimmed milk fortified by the addition of 1% glucose and 1% tryptone. The fermented milk was added as a 10% addition to an ice-cream mix. The complete mix was frozen in a soft-ice freezer and hardened at +20 degrees C. Ice-cream mixes with and without the addition of glycerol were produced to ascertain whether this had a protective effect against freezing of the probiotic bacteria. Viable counts of probiotic bacteria were made immediately after mixing and after freezing, as well as after 1, 4, 16 and 52 weeks of storage at -20 degrees C. The ice cream samples were organoleptically assessed for probiotic flavour, firmness, chewiness. sourness, off-flavour, iciness and total impression. During freezing, or shortly afterwards, the viable count declined by 0.7-0.8 log cfu/g. The viable count did not change significantly during 52 weeks of frozen storage (p<0.05) and remained above the recommended minimum limit of 10(6) cfu/g. The incorporation of glycerol in the ice-cream did not improve the survival of the strains. All the ice-cream samples received a high score in the organoleptic evaluation; the probiotic taste was not found to be particularly noticeable. Lb. reuteri containing ice-cream was significant more sour and attained a higher "probiotic flavour" than the other ice-cream samples.