The impact of cream processing on milk fat globule membrane (MFGM) was assessed in an industrial setting for the first time. Three creams and their derived MFGM fractions from different stages of the pasteurization procedure at a butter dairy were investigated and compared to a native control as well as a commercial MFGM fraction. The extent of cross-linking of serum proteins to MFGM proteins increased progressively with each consecutive pasteurization step. Unresolved high molecular weight aggregates were found to consist of both indigenous MFGM proteins and β-lactoglobulin as well as αs1- and β-casein. With regards to fat globule stability and in terms of resistance towards coalescence and flocculation after cream washing, single-pasteurized cream exhibited reduced sensitivity to cream washing compared to non- and double-pasteurized creams. Inactivation of the agglutination mechanism and the increased presence of non-MFGM proteins may determine this balance between stable and non-stable fat globules.

The aim of the studies presented in this research communication was to compare species of origin (goat and sheep) and the effect of treatment (pasteurization at 56, 63 and 72 °C, skimming and curding) and refrigeration time on colostrum antimicrobial activity (AnAc). Two experiments were performed. In experiment 1, twenty-four first milking colostrum samples were obtained (12 goats, 12 sheep) and an aliquot of each sample was subjected to 6 different treatments, control (untreated), pasteurization at 56, 63 and 72 °C, skimming and curding. Colostrum AnAc was tested directly against E. coli using disks in a Petri dish and Enrofloxacin (antibiotic) and saline serum as positive and negative control, respectively. Species had no effect (P > 0.05) on colostrum AnAc, and neither did pasteurization at different temperatures or skimming. However, curding showed the lowest colostrum AnAc (P < 0.05) in both species. In the second experiment, four treatments were assayed, control, pasteurization at 56 and 63 °C and skimming. An aliquot of twelve goat colostrum samples were refrigerated after treatments for 10 d at 4 °C. Colostrum AnAc was measured at 0, 2, 4, 6, 8, and 10 d. A reduction in colostrum AnAc was observed due to refrigeration time. The results suggest that if farmers use frozen colostrum for neonates, the process of curding colostrum or refrigeration at 4 °C longer than 4 d is not recommended.

The process of agglutination causes firm cream layers in bovine milk, and a functioning agglutination mechanism is paramount to the quality of non-homogenized milks. The phenomenon is not well-described, but it is believed to occur due to interactions between immunoglobulins (Ig) and milk fat globules. For the first time, this paper demonstrates how the process of agglutination can be visualized using confocal laser scanning microscopy, rhodamine red and a fluoresceinisothiocynat-conjugated immunoglobulin M antibody. The method was used to illustrate the effect on agglutination of storage temperature and pasteurization temperature. Storage at 5 °C resulted in clearly visible agglutination which, however, was markedly reduced at 15 °C. Increasing storage temperature to 20 or 37 °C cancelled any detectable interaction between IgM and milk fat globules, whereby the occurrence of cold agglutination was documented. Increasing 20 s pasteurization temperatures from 69 °C to 71 °C and further to 73 °C lead to progressively higher inactivation of IgM and, hence, reduction of agglutination. Furthermore, 2-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that changes in storage temperature caused a redistribution of Ig-related proteins in milk fat globule membrane isolates. Poly-immunoglobulin G receptor was present in milk fat globule preparations stored at cold (4 °C) conditions, but absent at storage at higher temperature (25 °C). The findings provide valuable knowledge to dairy producers of non-homogenized milk in deciding the right pasteurization temperature to retain the crucial agglutination mechanism.

Until now there are only few data on the effects of thermal treatments on the nutritional and hygienic characteristics of donkey milk. This Research Communication aims to provide information on the effects of pasteurization (at +65 °C for 30 min) and prolonged storage at refrigeration and freezing temperatures (21 d at + 3 °C ± 2 °C and up to 90 d at −20 °C ± 5 °C) on some nutritional and hygienic characteristics of Amiata donkey milk. The milk was monitored by chemical and microbiological analysis. Pasteurization ensured compliance with EC Regulation No 1441/2007, as Enterobacteriaceae were never found in the milk, or during storage at refrigeration and freezing temperatures. Colony count at 30 °C in pasteurized milk never went beyond 1 log CFU/ml. The heat treatment and the storage did not result in any variations in the main constituents of the milk. Only a decrease in lactose and few variations in some fatty acids at 90 d of freezing were observed. In conclusion, pasteurization was able to achieve and maintain a high hygienic-sanitary quality over time; storage at refrigeration or freezing temperatures did not alter the nutritional quality of fat and the gross composition of the product. These findings are useful to improve knowledge on the milk shelf life in order to guarantee safety and nutritional quality for infants who need small quantities of daily milk.

In recent decades, a diverse community of dairy farmers, consumers and nutrition advocates has campaigned amidst considerable government opposition, to secure and expand the right of individuals to produce, sell and consume fresh unprocessed milk, commonly referred to as ‘raw milk’. This advocacy shares important parallels with battles fought in the organic food movement over the past century. Both the raw milk and organic food movements originated with farmers and consumers who sought to replace industrialized food production and processing practices with more traditional ones. Both movements equate the preservation of natural integrity in farming and food handling with more wholesome, nutritious food and environmental conservation. Both movements have had to work diligently to overcome a false perception that their practices are anachronistic, notably with regard to productive output of organic agriculture and the safety of fresh unprocessed milk. There is also the failure of opponents to acknowledge a growing body of scientific evidence for health benefits associated with drinking of fresh unprocessed milk. The raw milk movement has the potential to economically benefit family farmers, much as organic agriculture has done. Building soil fertility, a foundational principle of organic farming, would benefit from having numerous small pasture-based dairies spread across the land providing fresh unprocessed milk. Agricultural universities and the Cooperative Extension System could seize a real leadership opportunity by promoting and participating in this reinvention of dairy farming, and restoring the ecology of this traditional food and farming system.

The combination of ultrasound and heat (thermoultrasound) is an emerging food preservation technique that retains higher quantities of bioactive components compared with current thermal pasteurization practice, but has not yet been assessed for pasteurizing human milk. Artificially contaminated human milk samples were treated with ultrasound (20 kHz, 150 watts) with and without heating. The retention of four human milk proteins was quantified by biochemical assay and laser scattering particle sizing was used to determine the extent of homogenization. While ultrasonic treatment was effective at inactivating Escherichia coli (D4 °C=5·94 min), Staphylococcus epidermidis exhibited resistance (D4 °C=16·01 min). Thermoultrasonic treatment was considerably more effective (Esch. coli D45 °C=1·74 min, D50 °C=0·89 min; Staph. epidermidis D45 °C=2·08 min, D50 °C=0·94 minutes) with a predicted retention (2·8 min treatment, 50°C) of secretory IgA lysozyme, lactoferrin and bile salt stimulated lipase of 91, 80, 77, and 45%, respectively. Homogenization of the milk samples occurred after 5 min and 2 min of ultrasonic and thermoultrasonic treatment, respectively. Thermoultrasonic treatment is an effective method for pasteurizing donor human milk and retaining a greater proportion of bioactive components compared with current practices. However, further studies are required to assess the practicality of applying this technique routinely to donor human milk.

Studies of the potential of high pressure homogenisation (HPH) for the combined pasteurisation/homogenisation of raw bovine milk were undertaken. Raw milk was preheated to 45 °C and HPH-treated at 150, 200 or 250 MPa; milk outlet temperature at these pressures were 67, 76·8 and 83·6 °C, respectively, with a holding time of ~20 s. Raw and commercially pasteurized and homogenized (CPH) milk samples were analysed as controls. Fat globules in HPH samples were approximately half the size of those in CPH samples, although differences were not significant (P>0·05). β-Lactoglobulin was denatured at pressures [ges ]150 MPa, although little denaturation of α-lactalbumin was observed. Numbers of psychrotrophic bacteria in raw milk were reduced by 2·73 log cycles by HPH at 150 MPa and were uncountable following HPH at 200 or 250 MPa. Mesophilic bacterial counts were reduced by 1·30, 1·83 and 3·06 log cycles by HPH at 150, 200 or 250 MPa, respectively. No viable Staphylococcus aureus nor coliform cells remained in any HPH milk samples. HPH did not affect the colour of milk and HPH samples did not cream during refrigerated storage. The activities of plasmin, alkaline phosphatase and lactoperoxidase in milk were all greatly reduced by HPH. Pseudomonas fluorescens, inoculated into milk (~106 cfu/ml), was reduced to undetectable levels by HPH at 200 MPa (milk inlet temperature, ~10 °C); however, Ps. fluorescens proteinase was quite resistant to HPH under such conditions. Overall, owing to the significant increase in temperature and the possibility of varying the holding time, there may be potential applications for HPH as a novel liquid milk processing technique, combining many advantages of conventional homogenization and pasteurization of milk in a single process.