The critical flux during ultrafiltration of whey protein concentrate and sodium caseinate suspensions was investigated. The weak form of critical flux was found for both suspensions. Critical flux of sodium caseinate was higher than that of whey protein concentrate. This could be due to the differences in particle size of the suspensions, resulting in a slower particle back transportation for small particles (whey proteins) compared to the larger casein micelles. Critical flux increased as crossflow velocity increased and decreased as concentration increased, suggesting that critical flux was determined by competition between rate of particle removal from the membrane surface and rate of particle movement towards the membrane surface. Influence of changing pH, addition of NaCl and CaCl2 on the critical fluxes of both protein suspensions was also studied. Increasing pH led to an increase in critical flux for both protein suspensions, suggesting that electrostatic repulsive forces are involved in determining critical flux in both cases. Addition of NaCl gave rise to a decrease in electrostatic interactions due to an increase in ionic strength and ζ potential, and resulted in a decrease in critical flux for sodium caseinate, but had no significant effect for whey protein concentrate. Addition of CaCl2 resulted in a decrease in the critical flux and had a more pronounced influence than NaCl. These results suggest that, in addition to electrostatic repulsive forces, other factors such as structure of protein may be involved in determining the critical flux.

The action of bile on bifidobacteria was studied by measuring changes in zeta potential, hydrophobicity and adherence to enterocyte-like cells in vitro. Highly hydrophobic strains shocked with bile displayed more negative zeta potential values and a decrease in adherence. When a non-hydrophobic non-adherent strain (CIDCA 5324) was shocked with bile, an increase in hydrophobicity was observed. However, no changes of zeta potential or adherence properties were apparent. The action of the bile components was different from the action of whole bile. Cholate and deoxycholate produced a decrease in the negativity of zeta potential values of all strains studied whereas taurocholate displayed a shift in zeta potential of hydrophobic strains to more negative values, thus explaining the decrease in the autoaggregation by charge repulsion. However, the decrease in zeta potential caused by cholate and deoxycholate did not increase autoaggregation in a hydrophobic non-adherent strain (CIDCA 531). This suggests that other forces are contributing to autoaggregation.

The effect of long-term intake of two fermented milk products on the development of hypertension was compared in young spontaneously hypertensive rats (SHR). The products contained tripeptides isoleucine-proline-proline (IPP) and valine-proline-proline (VPP), which have been shown to possess angiotensin converting enzyme (ACE) inhibitory activity. Six-week-old SHR were divided into four groups to receive orally ad libitum water, skim milk or two fermented milk products (fermented milk A or fermented milk B; the latter is commercially available in Japan with trade name Calpis®) for 14 weeks. The calculated intake of IPP was 0·4 mg/d and 0·2 mg/d in the groups receiving fermented milk A and B, respectively, whereas the corresponding amounts for VPP were 0·6 mg/d and 0·3 mg/d. Systolic blood pressure (SBP) was monitored weekly by tail-cuff method. The development of hypertension was significantly attenuated in both groups receiving fermented milk products, whereas skim milk did not affect blood pressure. The effect was detectable after 6 weeks of treatment. At the end of the experiment, the lowest blood pressure level was found in the group receiving fermented milk A: the SBP was 21 mm Hg lower than in the group receiving water and 10 mm Hg lower than in the group receiving fermented milk B. This difference could be explained by larger intake of ACE inhibitory tripeptides in the group receiving fermented milk A as compared with fermented milk B.

The dairy industry would benefit from rapid and non-destructive determination of moisture content of cheese products. The two components primarily responsible for the low-field magnetic resonance (MR) spin-spin relaxation (T2) signal of cheese products are fat and the water bound to protein. If the moisture component of the signal can be distinguished from the fat component, it should be possible to measure moisture using an MR sensor. Therefore, a key aspect of the development of an MR moisture measurement method is examination of techniques for analysis of T2 relaxation curves. One common method of T2 analysis of complex foods, such as cheese, is to fit multi-term exponential models to the curves. An alternative approach is proposed which uses stretched exponential models. The single-term stretched exponential model has been used for porous rock systems and polymers, but not for foods. The T2 relaxation curves were analysed using both models and the results were compared. The number of unknowns in the three-term exponential and two-term stretched exponential models was reduced by assuming the relaxation curve of the fat component was the same as the relaxation curve of pure fat. In each model, one of the exponential terms described the behaviour of the water in the cheese analogue, while the remaining term or terms described the behaviour of the fat. For each model the T2 relaxation time associated with the water was well correlated with moisture content. Coefficients of determination of the relaxation time versus moisture from each of the two models were nearly identical. The advantages and disadvantages of the two models are discussed.

In the dairy industry re-use and multi-use cleaning-in-place (CIP) systems are operated by circulating chemicals and water without taking the equipment apart. The solutions, which become polluted due to the removal of fouling compounds, are drained periodically when they are considered to be too polluted. This work shows the large variations in composition (pollution, surface tension, etc) of the industrial caustic solutions coming from milk standardization and pasteurization plant CIP throughout their life time (7 days) and from 1 week to another. The work is also intended to show how nanofiltration (1 kg mol−1 molecular weight cut-off) was robust and performed well, with good recovery of caustic solutions, even when faced with large variations of solutions composition: high caustic yield, permeation flux (J) in the range 42–110 l h−1 m−2, average chemical oxygen demand (COD) reduction equal to 0.58 and low surface tension change. Equations have been established for the prediction of J as a function of initial membrane hydraulic resistance (Rm) caustic concentration, volume reduction ratio (VRR) and initial soluble COD. When VRR increased, both J and pollution retention decreased despite the increase in irreversible fouling induced by the increase of soluble pollution concentration in retentate . The higher the initial soluble COD, the sharper the decrease in J vs. VRR. Since irreversible fouling was usually small (0.1–3.4×1013 m−1, that is to say of the same order of magnitude as Rm), the membrane cleaning could be efficiently performed by using single phase sodium hypochlorite alternately with a more expensive acid–base cleaning sequence. The obtained permeate was a clear regenerated cleaning solution with low soluble COD (0.2–3.5 g/l) and surface tension (56–30 mJ m−2) which could be successfully exploited owing to its cleaning potential.

The therapeutic and preventive effects of yogurt and lactic acid bacteria on diseases such as cancer, infection and gastrointestinal disorders are well documented. The aim of this research was to study the effects of different doses of yogurt addition after milk re-nutrition diet, on the recovery of the intestinal barrier and mucosal immune function. Experiments were performed on groups of mice, malnourished and re-nourished with milk during 7 d, and mice with diet supplemented with yogurt for 2, 5 and 7 consecutive d. Nutritional parameters such as weight gain, serum total protein, and the number of IgA, IgM and IgG B cells of the small intestine were determined. We also quantified intraepithelial leukocytes, mastocytes and goblet cells, and performed structural and ultrastructural studies on the small intestine. We observed that 5 d of yogurt feeding was the optimal dose for improving gut barrier function and mucosal immune system in a malnutrition model. This effect was not observed with milk re-nutrition. Although the results were better for 5 d of yogurt, addition for 7 d also showed beneficial effects. Yogurt feeding in our model did not impair any gut functions. These results suggest that yogurt addition after a re-nutrition diet gives better recovery of intestinal function than the re-nutrition diet usually recommended. Although these results were obtained in an animal model, they indicate that consumption of yogurt by malnourished children might accelerate the restoration of gut function.

Thirty-three Lactobacillus strains were tested as adjuncts in a cheese model system. Eighteen strains originated from cheese (nine Lactobacillus spp. and nine Lb. paracasei/casei) and 15 from human intestinal mucosa (11 Lb. rhamnosus; three Lb. paracasei; one Lb. plantarum). Model cheeses weighing 120 g were made of cheese grains from full-scale production of washed curd semi-hard cheese (Herrgård). The model system was reproducible and similar to full-scale production with respect to moisture, salt content, pH and microbial flora. The model cheeses were sampled for aerobic and anaerobic plate count and viable counts of Lactobacillus and Lactococcus. The presence of adjuncts in the model cheeses was confirmed by typing isolates with Randomly Amplified Polymorphic DNA (RAPD). The sensory properties of model cheeses were described. In a first trial 23 of the 33 adjuncts were re-isolated from the corresponding model cheeses after 9 or 13 weeks. Adjuncts of Lb. paracasei were re-isolated more frequently than adjuncts of Lb. rhamnosus. Nine strains were selected, on the basis of their ability to grow and be a dominating part of the microflora of model cheese with interesting sensory properties. These strains were further studied together with two commercial cultures. The sensory influences on model cheeses of six of the adjuncts were confirmed, and flavour scores were in the range of 2.9–7.1 for model cheeses with different adjuncts while the control had a flavour score of 5.6 (0–10 scale). Survival and growth of seven out of the nine strains correlated with the results of the first trial. Growth and influence on flavour of four adjunct cultures were confirmed in experimental cheese manufactured in a 400-l open vat.

The effects of high intensity pulsed electric field (HIPEF) treatments at room or moderate temperature on water-soluble (thiamine, riboflavin, ascorbic acid) and fat-soluble vitamins (cholecalciferol and tocopherol) were evaluated and compared with conventional thermal treatments. Vitamin retention was determined in two different substrates, milk and simulated skim milk ultrafiltrate (SMUF). Samples were subjected to HIPEF treatments of up to 400 μs at field strengths from 18·3 to 27·1 kV/cm and to heat treatments of up to 60 min at temperatures from 50 to 90 °C. No changes in vitamin content were observed after HIPEF or thermal treatments except for ascorbic acid. Milk retained more ascorbic acid after a 400 μs-treatment at 22·6 kV/cm (93·4%) than after low (63 °C-30 min; 49·7% retained) or high (75 °C-15 s; 86·7% retained) heat pasteurisation treatments. Retention of ascorbic acid fitted a first-order kinetic model for both HIPEF and thermal processes. First-order constant values varied from 1·8×10−4 to 1·27×10−3 μs−1 for the HIPEF treatments (18·3–27·1 kV/cm) and, for thermal processing ranged from 5×10−3 to 8×10−2 min−1 (50–90 °C). No significant differences were found between the results obtained after applying HIPEF treatments at room or moderate temperature. However, results depended on the treatment media. A beneficial effect of natural skim milk components, mainly proteins, was observed on the preservation of ascorbic acid, since skim milk retained more ascorbic acid than SMUF after HIPEF treatments.

Monensin sodium is widely used to manipulate ruminal fermentation (Bergen & Bates, 1984), with the aim of increasing energy supply to the animal. Monensin has been most widely used in diets of beef cattle and young growing dairy cattle, particularly in confinement management systems, where the ionophore can be mixed directly into the ration. Accurate daily dosing of grazing ruminants with small quantities of rumen modifiers, such as ionophores, proved particularly labour-intensive and expensive until the development of the controlled-release capsule (CRC; Laby et al. 1984). Subsequently a commercially available CRC containing monensin sodium was developed (Elanco Animal Health, Cambridge, NZ) facilitating its use in grazing animals. It has also been tested as a method of reducing the incidence of bloat in lactating dairy cows grazing pastures containing legumes.

The influence of carbonation on the evolution of lactose, galactose and glucose in fermented milks with added probiotic bacteria (Lactobacillus casei, Lactobacillus acidophilus and/or Bifidobacterium bifidum) was evaluated and related to β-galactosidase activity of starter strains. During incubation and first days of refrigeration, lactose hydrolysis resulting in the liberation of galactose and glucose occurred in CT (Streptococcus thermophilus/Lb. casei), AT (Str. thermophilus/Lb. acidophilus) and ABT fermented milks (Str. thermophilus/Lb. acidophilus/Bifid. bifidum). Levels of galactose were higher than those of glucose and could be related to the preferential consumption of glucose by actively growing bacteria. Through the incubation, lactose and monosaccharide levels were not affected by milk carbonation. However, during refrigerated storage the presence of this gas was associated with slightly lower content of lactose and higher levels of galactose and glucose in AT and ABT products but not in CT fermented milks. Through the refrigeration galactose was moderately utilised by Lb. acidophilus in AT products whereas the presence of Bifid. bifidum seems to prevent the consumption of this sugar in ABT fermented milks. Glucose remained constant, with minor variations in CT products but a continuous increase of this sugar occurred in carbonated AT and ABT fermented milks during storage. β-Galactosidase activity displayed by Str. thermophilus strains was similar at pH 6·5 (initial pH of non-carbonated samples) and pH 6·3 (initial pH of carbonated samples) whereas Lb. acidophilus LaA3 showed greater β-galactosidase activity at pH 6·3 than at higher pH values. Thus, the enhanced metabolic activity of Lb. acidophilus caused by the low initial pH of carbonated milk also promoted higher cellular β-galactosidase activity that could have released greater amounts of galactose and glucose from lactose in AT and ABT fermented milks through the refrigerated period. In CT fermented milks, similar β-galactosidase activity levels of Str. thermophilus at pH 6·5 and 6·3 together with the absence of β-galactosidase activity in Lb. casei could explain the lack of differences on glucose and galactose content between carbonated and non-carbonated samples.

Iron is an essential element for humans and physiological needs are determined by obligatory loss, growth, menstruation and pregnancy. Although iron metabolism occurs in a ‘closed circuit’, physiological losses occur and they must be made good. Three factors are important in the study of iron needs: the total amount of iron in the diet; the nature of the iron compound; and other components of the diet (Hallberg et al. 1998). Although iron de®ciency ensues if insu¾cient iron is absorbed to meet requirement, the total iron absorbed normally exceeds requirement (Hallberg et al. 1997; Jackson, 1997).

Since its identification by Devirese et al. (1983), Staphylococcus caprae has been frequently isolated from udder halves of goats with subclinical intramammary infection (IMI) (Contreras et al. 1995; Poutrel et al. 1996). Several different studies have demonstrated the capacity of Staph. caprae to persist throughout lactation (Poutrel et al. 1996; Contreras et al. 1997; Bedidi-Madani et al. 1998a) and during the dry period (Poutrel, 1984). Bedidi-Madani et al. (1998a) found that isolates of Staph. caprae from udders of uninfected goats express potential virulence factors (different exoproteins and slime); other researchers have occasionally isolated it from clinical cases of goat mastitis (Deinhofer & Pernthaner, 1995), or from human clinical specimens associated with bone and joint infection (Vandenesh et al. 1995; Shuttleworth et al. 1997). In spite of these forms of pathogenicity, some studies have not shown significant increases in somatic cell count (SCC) of milk from goat udder halves infected by Staph. caprae (Deinhofer & Pernthaner, 1995; Poutrel et al. 1996). Moreover, there is a lack of information on the effect of infection by this mammary pathogen on milk yield and composition. Knowledge of repercussions for hygiene and production would be useful in mastitis control programmes in view of the high frequency of isolation (higher than 22% of the staphylococci isolated) of Staph. caprae in dairy goat herds (Contreras et al. 1995; Poutrel et al. 1996). The aim of the present investigation was to ascertain the significance of persistent subclinical IMI by Staph. caprae on SCC, milk yield and physical-chemical parameters of Murciano-Granadina goat milk at mid-lactation.

Cystic fibrosis (CF) is the most common genetic disease of Caucasians with an incidence of 1 in 2500 live births and a carriage rate of 1 in 20 individuals. CF patients continue to suåer from recurrent and chronic respiratory tract infections and most of their morbidity and mortality is due to such infections throughout their life (Høiby, 1991). These infections are usually dominated by Gram-negative organisms, especially by the pseudomonads including in particular, Pseudomonas aeruginosa, as well as members of the Burkholderia cepacia complex of organisms.

In the present work, 67 strains of Lactobacillus helveticus isolated from whey starter cultures and cheeses were identified and grouped by genotypic and phenotypic methods. Strains were identified by sugar fermentation pattern, by cell-wall protein profile, and by probe hybridisation. Phenotypic diversity was evaluated by a chemometric model taking into account biochemical characteristics (i.e. acidifying and peptidase activities) of technological interest. Genotypic diversity was evidenced by RAPD-PCR, which provided strain-specific patterns and revealed the occurrence of different strains. The RAPD-PCR profiles were clustered according to their similarities; the groups obtained, together with the cell-wall protein profiling and the chemometric information, could be sometimes correlated with the type of cheese and/or dairy niches used as sources of strains. A computerised analysis of genotypic and phenotypic information could be successfully applied for rapid and reliable differentiation and characterisation of Lb. helveticus isolates occurring in different dairy products.

Proteolysis of casein is the principal cause of textural changes and flavour development in ripened cheese (Fox & McSweeney, 1996). Caseins are degraded into small peptides and free amino acids during a complex process, described by Grappin et al. (1985) as a two-step scheme. Caseins are initially broken down into large, well characterised fragments. This initial step, called primary proteolysis, is catalysed principally by the residual coagulant (chymosin and pepsin), and to a variable extent by endogenous milk proteases, such as plasmin, cathepsin D, and possibly somatic cell proteinases. Enzymes originating from either rennet or milk are active in most ripened cheese varieties. However, their relative contributions vary substantially depending on manufacturing practices. For instance, in Swiss-type cheeses, cooking the curd extensively inactivates the coagulant, and simultaneously enhances plasmin activity, which therefore becomes predominant (Ollikainen & Kivela, 1989).

Milk is known to provide not only excellent nutrition but also protection against infection in mammalian neonates. Whey proteins, such as immunoglobulins, lactoferrin, lysozyme and lactoperoxidase, are well known antimicrobial components in milk. Håkansson et al. (1995) demonstrated that some multimeric human α-lactalbumin derivatives induced apoptosis in immature and tumour cells. Yoo et al. (1997) found that lactoferricin, which had been isolated from peptic lactoferrin as an antimicrobial peptide, induced apoptosis in tumour and immature mammalian cells. Apoptotic cell death is considered to be an important physiological function in the development and homeostasis of multicellular organisms and to be a highly controlled means of eliminating dangerous, damaged or unnecessary cells without causing tissue damage. Therefore, these findings suggest that whey proteins may have beneficial health effects by restricting specific cell population in the body.

Use of electromyography (EMG) to monitor mastication is a relatively new concept in assessing food physical and sensory properties. Although expert assessment of cheese characteristics is widely used, the effect of training in sensory analysis on mastication patterns, as assessed using EMG is not well known. Nine samples of the same Mahon cheese (60 days ripening) were given to 24 subjects (8 experts, 16 untrained) and EMG recorded for each chewing sequence. Three samples were tested in a single session by each subject, and three sessions carried out on different days. EMG was recorded from four masticatory muscles for each subject. From EMG records the following was extracted: number of chews, chewing time, mean and maximum voltage of EMG bursts (i.e. chews) across chewing sequence, chewing work and chewing rate. No gender bias was found for the EMG parameters considered, therefore, as regards gender, each group was considered to be homogeneous. Variability within-subjects across samples was greater for experts than untrained subjects. Significant differences in chewing time, chewing work and chewing rate were found between the expert and untrained groups. Data analysis of the three sessions showed an influence of cognitive constructs, mediating states, on the chewing process. The experts were found to be goal driven as to their mastication process. Experts showed no significant differences between sessions, untrained subjects were found to vary their EMG output in successive sessions for number of chews, chewing time, mean voltage, and chewing work.