Deciphering the segregation of proteins in high-protein dairy powders after spray-drying.

High-protein dairy powders are ingredients mainly produced by spray-drying, then subjected to aging during transport and storage. They often undergo physicochemical changes at this stage, such as the development of the Maillard reaction, primarily because of their intrinsic chemical properties, but also as a result of nonoptimal storage conditions. Components present at the particle surface are the first to be targeted by moisture and other environmental disruptions. Consequently, the identification, control, and prediction of particle surface components are useful to anticipate the effect of powder aging on product quality. Here, a new diafiltration method is proposed which fractionates proteins from a binary colloidal dispersion of 80% casein micelles and 20% whey proteins, according to their presence at the surface or core of the particle. This method shows that whey proteins are strongly enriched at the particle surface, whereas casein micelles are located at the core of the particles. This protocol also allows the identification of the rehydration kinetics for each rehydrated protein layer of the particle, revealing that 2 distinct forms of swelling occur: (1) a rapid swelling and elution of whey proteins present at the particle surface, and (2) a swelling of casein micelles located below the whey proteins, associated with a slow elution of casein micelles from the particles being rehydrated.

Recent advances on lactose intolerance: Tolerance thresholds and currently available answers.

The genetically programmed reduction in lactase activity during adulthood affects 70% of the world adult population and can cause severe digestive disorders, which are the sign of lactose intolerance. Lactose intolerance symptoms vary depending on the residual lactase activity, the small bowel transit time, and especially the amount of ingested lactose. To formulate dairy products suitable for the vast majority of lactose intolerants, it is essential to define lactose intolerance threshold. A recent meta-analysis permitted to show that almost all lactose intolerants tolerate 12 g of lactose in one intake and approximately 18 g of lactose spread over the day. The prevalence and severity of lactose intolerance are probably overestimated by the general public. This misconception usually leads to an unnecessary reduction of dairy foodstuff consumption. Nevertheless, dairy products are essential for health mainly due to their calcium content and the positive influence of probiotic bacteria. The formulation of dairy products suitable for most intolerant and suspicious subjects seems necessary. The use of exogenous enzyme preparations, as well as the consumption of lactose-free products or products rich in probiotic bacteria are proposed as symptom-reducing strategies.

Physicochemical and thermal properties of taro (Colocasia esculenta sp) powders as affected by state of maturity and drying method.

The study was aimed at determining the effect of harvesting time and drying method on the thermal and physicochemical properties of taro powder, Sosso ecotype. A 5 × 2 factorial experiment with 5 harvesting times (6, 7, 8, 9 and 10 months after planting) and 2 drying methods (sun and electric oven drying) was used for this purpose. The variance component analysis revealed harvesting time as the most important factor affecting all the variables measured. In particular the proteins and available sugar contents of the powders increased significantly with increase in harvesting time. The same was true of the gelling property and water absorption capacity of the powders. It was equally observed that the temperatures (start, peak and end) and enthalpy of gelatinization of the powders increased with harvesting time. It is concluded that harvesting sosso-taro at full maturity (10 months after planting) and sun-drying produces food powders with excellent gelling properties among others.

Combined effect of heat treatment and ionic strength on the functionality of whey proteins.

A 5% (wt/vol) whey protein isolate (WPI) dispersion (pH 6.5) with different concentrations of NaCl was submitted to dynamic heat treatment. Protein dispersions were characterized as to their rheological properties, particle sizes, morphology, denaturation temperatures, and protein surface hydrophobicity. At low ionic strength (<200 mmol/kg), gel elastic modulus increased and strongest gel stiffness was achieved. High salt concentrations lead to a weaker gel, whereas no gels at all were formed without salt. The gelation temperature was also influenced by ionic strength and an increase in denaturation temperature and thermal stability was also observed by using differential scanning calorimetry. Additionally, heat-induced changes in secondary structures upon salt augmentation were followed by Fourier transform infrared spectroscopy. Secondary structural elements estimations obtained from amide I assignments were correlated with those from amide III assignments. Upon salt increase, no differences in secondary structure were observed without heating, whereas upon heating and without salt increase, the Fourier transform infrared spectroscopy data revealed an increase in intermolecular ß-sheets at the cost of ß-turns and random coils, with no change in α-helical structures. However, NaCl addition along with dynamic heat treatment of WPI dispersion showed a stabilizing effect on the secondary structural elements of both amide I and amide III bands. Whey protein isolate dispersions in water were also characterized by transmission electron microscopy by a spherical shape with 2 populations (6 and 70 nm). Salt increase alone resulted in the formation of denser aggregates, whereas a transition from spherical/compact protein aggregates to linear ones was observed due to combined salt/heat effect. The important size of these edifices was confirmed by microscopy and light-scattering techniques. Moreover, protein surface hydrophobicity related to the number of hydrophobic sites available decreased significantly. Finally, experimental results demonstrated the strong interaction between ionic strength and dynamic thermal treatment on protein functional properties and their careful adjustment could enable the food industry to effectively use WPI as a gelling agent.

Characterization of high-milk-protein powders upon rehydration under various salt concentrations.

Rehydration of native micellar casein and native whey isolate protein powders was followed in different ionic environments. Solutions of NaCl and CaCl2 in the concentration range of 0 to 12% (wt%) were used as rehydration media. The rehydration profiles obtained were interpreted in terms of wetting, swelling, and dispersion stages by using a turbidity method. Two behaviors were observed depending on the salt concentration. For native micellar casein powder, a significant change was observed between 3 and 6% NaCl and between 0.75 and 1.5% CaCl2. The first behavior (low salt concentration) presents a typical rehydration profile: quick wetting, swelling, and long dispersion stage. The dispersion stage of the second behavior (high salt concentration) was significantly shortened, indicating a strong modification of the protein backbone. The rehydration of whey protein powder was less influenced by salts. At low salt concentrations, a typical profile for whey powders was observed: wetting with lump formation and no swelling followed by a quick dispersion. At high CaCl2 concentrations, no turbidity stabilization was observed, indicating a possible protein unfolding and denaturation. Additionally, the changes in secondary structures of the 2 proteins upon salt increase were followed by Fourier transform infrared spectroscopy and confirmed the different profiles observed.

Dairy powder rehydration: influence of protein state, incorporation mode, and agglomeration.

A simplified method to study rehydration was used on different dairy powders. The method involved dispersing powder in a stirred vessel equipped with a turbidity sensor. The changes of turbidity occurring during powder rehydration highlighted the rehydration stage, and the influence of the proteins' state on rehydration was clarified. Casein powders had a quick wetting time but very slow dispersion, making the total rehydration process time-consuming. On the other hand, whey powders were found to have poor wettability but demonstrated immediate dispersion after wetting. Mixing casein (80%) and whey (20%) before spray drying greatly improved rehydration time compared with casein powder; whereas mixing whey powder with casein powder at the same ratio after spray drying caused a dramatic deterioration in the rehydration properties. Moreover, agglomeration was found to significantly improve the rehydration time of whey protein powder and to slow down the rehydration time of casein powder. These opposite effects were related to the rate-controlling stage (i.e., wetting stage for whey protein and dispersion stage for casein).

Lactose crystallization delay in model infant foods made with lactose, beta-lactoglobulin, and starch.

Handling and storage alter infant food powders due to lactose crystallization and interactions among components. Model infant foods were prepared by colyophilization of lactose, beta-lactoglobulin (beta-LG), and gelatinized starch. A mixture design was used to define the percentage of each mixture component to simulate a wide range of infant food powders. The kinetics of crystallization was studied by a gravimetric method (dynamic vapor sorption) at 70% relative humidity (RH). After freeze-drying, lactose was amorphous and crystallized at 70% RH. The delay before crystallization depends on the contents of beta-LG and starch in the formulations. A mathematical model was proposed to predict crystallization time (delay) at 70% RH. For the formulation containing 50% lactose, 25% beta-LG, and 25% starch, lactose was still amorphous after 42 h at 70% RH, whereas pure amorphous lactose crystallized after approximately 70 min. Calculated and experimental results of adsorbed moisture from the formulations were compared. Adsorbed water of formulation containing lactose could not be calculated from moisture sorption properties of each component at a given RH because beta-LG and gelatinized starch prevented lactose crystal growth.

Surface composition of dairy powders observed by X-ray photoelectron spectroscopy and effects on their rehydration properties.

The surface composition of three dairy powders was investigated by X-ray photoelectron spectroscopy. These spray-dried casein powders were more or less enriched in hygroscopic material (lactose and/or minerals). The principal limitation of these high protein content powders is their poor rehydration ability. Consequently, information about surface composition is required in order to get a better understanding of rehydration behaviour (i.e. wetting time and time of rehydration). The obtained results indicate that the surface of the three powders was dominated by proteins. Lactose and minerals are marginal compounds at the surface whereas the surface coverage of fat was over represented. A correlation between the lactose surface content and the wetting time of the powders was found, but no relationship with the surface fat. Moreover, as the surface is partly depleted in minerals and lactose, it is concluded that these compounds are principally located in the bulk of the particle. Therefore this observation could be related with a wetting time of the powders only slightly affected by the addition of hygroscopic material whereas the time of rehydration was strongly improved; powder wetting being more affected by the surface composition whereas powder dispersion being more influenced by the powder bulk composition.

Modeling of lactose crystallization and color changes in model infant foods.

Lactose crystallization and color changes in formulas containing beta-lactoglobulin and gelatinized starch were investigated. Model infant formulas were prepared by colyophilization of 3 components (lactose, beta-lactoglobulin, and gelatinized starch). A mixture design was used to choose the percentage of each mixture component. These formulas were stored for 3 mo at different relative humidities (RH), ranging from approximately 0 to 94.6%, to study the lactose crystallization and color changes. Crystallization kinetics was studied by gravimetric methods, and lactose state (crystalline vs. amorphous) was verified before and after storage by differential scanning calorimetry. Before storage, lyophilized lactose was amorphous, but during storage it crystallized, depending on the RH. The lactose crystallization RH depended on the quantity of beta-lactoglobulin and gelatinized starch, and by increasing these quantities, the crystallization RH increased. For some formulas, the crystallization RH was noted at 3 different RH during storage. The first was noted after 1 d of storage and the second and third were observed later on, showing that crystallization is a time-dependent phenomenon. Nonenzymatic browning was studied in model infant formulas by yellow color changes of samples at 11.3, 43.2, 54.5, and 75.4% RH. In this study, 7 mathematical models were proposed to predict the moisture sorption properties and color changes at different RH, and the models were validated by experimental results.

Apoptosis inducing activity of viscin, a lipophilic extract from Viscum album L.

Detection of antiproliferative activity and bioactivity-guided fractionation of viscin, a lipophilic extract from Viscum album L., led to the isolation of betulinic acid, oleanolic acid and ursolic acid as active components. Viscin, betulinic acid, oleanolic acid and ursolic acid inhibited growth and induced apoptotic cell death in Molt4, K562 and U937 leukaemia cells. The growth inhibitory effect of viscin was more pronounced in Molt4 and U937 cells (IC50 (concentration that inhibited cell proliferation by 50%): 118 +/- 24 and 138 +/- 24 microg mL(-1)) than in K562 cells (IC50: 252 +/- 37 microg mL(-1)). Oleanolic acid was the least effective in all cell lines (7.5-45.5% inhibition at 10 microg mL(-1)) and ursolic acid the most active in Molt4 and U937 cells (81.8 and 97.8% inhibition, respectively, at 5 microg mL(-1)). A dose-dependent loss of membrane phospholipid asymmetry associated with apoptosis was induced in all cell lines as shown in flow cytometry by the externalization of phosphatidylserine and morphological changes in cell size and granularity. There were differences in individual cell lines' response towards the apoptosis-inducing effect of viscin, betulinic acid, oleanolic acid and ursolic acid. The triterpenoids beta-amyrin, beta-amyrinacetate, lupeol, lupeolacetate, beta-sitosterol and stigmasterol, and the fatty acids oleic acid, linoleic acid, palmitic acid and stearic acid were also present in the lipophilic extract.

Use of a turbidity sensor to characterize micellar casein powder rehydration: influence of some technological effects.

A simplified method to study rehydration of dairy powders was developed for native phosphocaseinate powder. The method involved dispersing powder in a stirred vessel equipped with a turbidity sensor under standardized conditions. The changes of turbidity occurring during powder rehydration highlighted several stages. These stages include particles wetting, and then swelling as the water penetrates into the powder bed, followed by a slow dispersion of the particles. With this tool, some technological effects on powder rehydration were analyzed. Ultrafiltrate incorporation to the casein concentrate before spray drying was found to greatly improve the rehydration, whereas mixing ultrafiltrate powder with casein powder after spray drying did not change the rehydration properties. The effect of granulation on powder rehydration stages was also investigated.

Toward a better determination of dairy powders surface composition through XPS matrices development.

The surface composition of dairy powders prepared by mixing various amounts of micellar casein (MC), whey proteins isolate (WPI), lactose, and anhydrous milk fat (AMF) was investigated by XPS measurements. The use of matrices are generally accepted to transform surface atomic composition (i.e., C, O, N contents) into surface component composition (i.e., lactose, proteins, lipids). These atomic-based matrices were revisited and two new matrices based on the surface bond composition were developed. Surface compositions obtained from atomic and bond-based matrices were compared. A successful matrix allowing good correlations between XPS predicted and theoretical surface composition for powders free from fat was identified. Nevertheless, samples containing milk fat were found to present a possible segregation of components owing to the AMF overrepresentation on the surface. Supplementary analyses (FTIR, SEM) were carried out in order to investigate the homogeneity of the mixtures.

Gene regulation of melatonin and dopamine receptors during eye development.

To gain insight into the role of melatonin and dopamine in retinal development, gene expression of two melatonin receptors, MT1 and MT2, as well as five dopamine receptors, D1, D2, D3, D4 and D5, in the rat eye was analyzed by reverse transcription-polymerase chain reaction across various developmental stages. MT1 transcript levels reached maximum levels at embryonic day (E) 16 and then decreased gradually until reaching adult levels by postnatal day (P) 14. MT2 transcript levels similarly peaked at E16, but then decreased dramatically until birth to its lowest levels, which were maintained throughout the postnatal period. Thus, gene expression of both the MT1 and MT2 receptors showed a striking inverse correlation with maturation of the eye. In contrast to melatonin receptors, gene expression of all dopamine receptor subtypes, except for D3, showed only an increase as development proceeds with highest levels in adulthood. The D3 message was not detected throughout the developmental period examined. Gene expression of D1-like receptors, D1 and D5, showed a substantial increase to adult levels during the fetal period at E16 and E20, respectively. Transcript levels of D2-like receptors, D2 and D4, on the other hand, were not detected before birth but increased significantly to adult levels by P7 and P14, respectively. The present findings suggest the presence of unique developmental mechanisms by which transcription of various G protein-coupled receptors are regulated in the eye.

A new abortion technique: intravaginal and intramuscular prostaglandin.

The 15-methyl analog of prostaglandin F2 alpha (15-ME-PGF2 alpha), administered in a 3-mg dose via a single vaginal suppository and supplemented at 24 hours by intramuscular injection(s) of 250 micrograms, successfully induced abortion in 80 of 81 patients in the midtrimester of pregnancy. The mean abortion time was 19.6 hours. Two thirds of the patients aborted after treatment with the suppository alone in a mean time of 14.6 hours; the remaining 27 patients required intramuscular injections of 15-ME-PGF2 alpha to effect expulsion of the products of conception. Twenty-six of these 27 patients subsequently aborted in a mean total abortion time of 29.6 hours. Fifty-eight patients aborted within 24 hours of the initial prostaglandin administration, and 78 aborted by 36 hours. Parity and length of gestation did not significantly affect abortion time in this series, although the mean abortion time for parous patients and patients with gestations earlier than 17 weeks tended to be somewhat shorter than that of nulliparous patients and those with more advanced gestations. The placenta was spontaneously expelled in the majority of patients. Abortion was incomplete in 3 patients and required curettage. Uterine activity, as measured via an intraamniotic catheter in 6 patients, developed very gradually with the suppository, peaking at 3 hours after insertion, and was characterized by regular contractions with low intrauterine baseline tonus. The gastrointestinal side effects that occurred in 59% of patients who received the suppository were also most frequently observed at 3 hours after administration. In contrast the gastrointestinal disturbances elicited by intramuscular injections of the analog immediately followed the administration.

Prothrombin activation fragment (F1.2) is increased in pregnant patients with antiphospholipid antibodies.

Recurrent fetal wastage has been attributed to thrombosis in the antiphospholipid antibody syndrome (APAS); however, this has not been proven. Assays of coagulation activation fragments which may provide evidence for a role for thrombosis, have not been previously reported in this setting. We therefore investigated whether F1.2 levels are altered in APAS pregnancies. F1.2 levels were performed on plasmas obtained from fifty-four APA patients with a history of persistent elevation of antiphospholipid antibodies and recurrent abortion who were studied during eighty-three consecutive visits. Results from these patients were compared to a control group of thirty-two healthy pregnant females. F1.2 levels were significantly higher in APAS patients than controls in the second trimester (6.5 nM +/- 4.3 nM vs. 1.2 nM +/- 0.9 nM, p < 0.0001), and in the third trimester of pregnancy (8.6 nM +/- 2.5 nM vs. 3.7 nM +/- 2.0 nM, p < 0.0001). The F1.2 levels in the APA group returned to baseline soon after delivery. No correlation was observed between F1.2 and APA values. This study shows that pregnant patients with a history of recurrent abortions and APA have significantly increased activation of prothrombin compared to healthy pregnant females. These data indicate that the potential value of activations peptide assays such as F1.2 in this setting should be tested in prospective clinical trials.

Cloud-point analysis of microlitre samples-determination of water in six common solvents.

The classical cloud-point technique for determination of small amounts of water in organic solvents has been systematically investigated. The extreme sensitivity of the critical solution temperature of binary liquid mixtures to traces of impurity in one of the components makes the cloud-point method capable of high accuracy and sensitivity for routine determination of solvent contamination by water, and is admirably suited to analysis of small samples. Typically, the absolute error for water as contaminant is about 0.2% for 10-mul samples and 0.06 % for 50-mul samples. The critical solution temperature used was that of the n-hexane-methanol system. Its value is in dispute and considerable care was taken to obtain what is believed to be the correct value of 34,4 +/- 0,2 degrees . Small amounts of water in methanol, ethanol, 2-propanol, acetone, ethyl methyl ketone and dioxan were determined.

The collapsing perimeter. A commentary on life, death, and death-in-life.

The individual is encased in an existential, phenomenological space that has the capacity to contract or expand, to isolate itself, or to join with others. An analysis is provided of how this individual space capsule functions under varying circumstances, such as depression, schizophrenia, sociopathy, divorce, child-battery, aging, death, overpopulation, cultural disruption, and execution.

Lactic acid bacteria in dairy food: surface characterization and interactions with food matrix components.

This review gives an overview of the importance of interactions occurring in dairy matrices between Lactic Acid Bacteria and milk components. Dairy products are important sources of biological active compounds of particular relevance to human health. These compounds include immunoglobulins, whey proteins and peptides, polar lipids, and lactic acid bacteria including probiotics. A better understanding of interactions between bioactive components and their delivery matrix may successfully improve their transport to their target site of action. Pioneering research on probiotic lactic acid bacteria has mainly focused on their host effects. However, very little is known about their interaction with dairy ingredients. Such knowledge could contribute to designing new and more efficient dairy food, and to better understand relationships between milk constituents. The purpose of this review is first to provide an overview of the current knowledge about the biomolecules produced on bacterial surface and the composition of the dairy matter. In order to understand how bacteria interact with dairy molecules, adhesion mechanisms are subsequently reviewed with a special focus on the environmental conditions affecting bacterial adhesion. Methods dedicated to investigate the bacterial surface and to decipher interactions between bacteria and abiotic dairy components are also detailed. Finally, relevant industrial implications of these interactions are presented and discussed.

Interest of energy dispersive X-ray microanalysis to characterize the surface composition of milk powder particles.

Energy dispersive X-ray (EDX) is a technique rarely used for organic powders. Nevertheless, this technique is of great interest in the characterization of milk particle surface. In order to validate the method, the EDX technique was tested on pure milk components, on model powders composed of different ratio of lactose/whey proteins and on whole milk powders presenting or not free fat at the surface. For all these powders, satisfactory results were obtained with correct experimental atomic percentages in comparison with expected theoretical percentages. The technique was then applied to skimmed and whole milk powders sieved in 4 fractions. The surface and the core (cut particle) were analyzed by EDX and compared. A relationship between the particle size and the surface composition was observed. X-ray photoelectron spectroscopy (XPS) often used to characterize milk powder surface, however no differences were observed between surface and core composition using this method. The depth of analysis by EDX is far more significant (1 µm) in comparison to that of the XPS (5 nm); hence it was concluded that the analysis of cut particle by EDX was not interesting since too close to the results obtained at the surface. Finally, the technique was coupled with XPS and successful hypothesis concerning composition gradients were done.

In vitro interactions between probiotic bacteria and milk proteins probed by atomic force microscopy.

Interactions between microbial cells and milk proteins are important for cell location into dairy matrices. In this study, interactions between two probiotic strains, Lactobacillus rhamnosus GG and Lactobacillus rhamnosus GR-1, and milk proteins (micellar casein, native and denatured whey proteins) were studied. The bacterial surface characterization was realized with X-ray photoelectron spectroscopy (XPS) to evaluate surface composition (in terms of proteins, polysaccharides and lipid-like compounds) and electrophoretic mobility that provide information on surface charge of both bacteria and proteins along the 3-7 pH range. In addition, atomic force microscopy (AFM) enabled the identification of specific interactions between bacteria and whey proteins, in contrast to the observed nonspecific interactions with micellar casein. These specific events appeared to be more important for the GG strain than for the GR-1 strain, showing that matrix interaction is strain-specific. Furthermore, our study highlighted that in addition to the nature of the strains, many other factors influence the bacterial interaction with dairy matrix including the nature of the proteins and the pH of the media.