Hysteresis in phase volumes, compositions and interfacial roughness in model OPV-small-molecule/polymer thin-films.

Domain morphology and composition, and the structure of interfaces between domains are key factors in the performance and stability of organic photovoltaics (OPVs) fabricated from polymer/small-molecule blends. In this study, we investigate the evolution of composition, phase-volume and interfacial roughness in model polymer/small-molecule bilayers, in response to thermal annealing. Polystyrene/fullerene mixing is studied as a function of annealing temperature, using in situ neutron reflectivity, in thin-film bilayer samples comprising pure component or mixed layers. Remarkably, we discover that thermal annealing at temperatures around or above the reported glass transition temperatures, Tg, of the components can result in extensive mass-transfer between layers, that has the superficial appearance of equilibration, but leaves the layer compositions, thicknesses, and/or the interfacial composition profile in a non-equilibrium state. This is not merely a case of slow kinetics near Tg, as subsequent heating to higher temperatures, followed by cooling, reveals pronounced hysteresis in these systems. This has important implications for the measurement of equilibrium compositions in polymer/small-molecule mixtures for OPV applications, and for device stability during operation.

Liquid-liquid equilibrium in polymer-fullerene mixtures; an in situ neutron reflectivity study.

The composition profiles of a series of model polystyrene/fullerene bilayers are measured, before, during and after thermal annealing, using in situ neutron reflectometry. In combination with grazing-incidence X-ray diffraction measurements, these experiments, which quantify layer compositions as a function of molecular weight using changes in both scattering length density and layer thickness, extend and corroborate recent measurements on ex situ annealed samples and demonstrate that the composition profiles rapidly formed in these systems correspond to two co-existing liquid-liquid phases in thermodynamic equilibrium. The measurements also demonstrate a clear and systematic onset temperature for diffusion of the fullerenes into the PS layer that correlates with the known glass-transition temperatures of both the polymer (as a function of molecular weight) and the fullerene, revealing that the molecular mobility of the fullerenes in these systems is controlled by the intrinsic mobility of the fullerenes themselves and the ability of the polymer to plasticise the fullerenes at the interface. Over the temperature range investigated (up to 145 °C), measurements of equilibrated composition profiles as a function of temperature (during gradual cooling) reveal no significant changes in composition profile, other than those associated with the known thermal expansion/contraction of polystyrene thin-films.

Essential medicines for emergency care in Africa.

OBJECTIVES: Essential medicines lists (EMLs) are efficient means to ensure access to safe and effective medications. The WHO has led this initiative, generating a biannual EML since 1977. Nearly all countries have implemented national EMLs based on the WHO EML. Although EMLs have given careful consideration to many public health priorities, they have yet to comprehensively address the importance of medicines for treating acute illness and injury. METHODS: We undertook a multi-step consensus process to establish an EML for emergency care in Africa. After a review of existing literature and international EMLs, we generated a candidate list for emergency care. This list was reviewed by expert clinicians who ranked the medicines for overall inclusion and strength of recommendation. These medications and recommendations were then evaluated by an expert group. Medications that reached consensus in both the online survey and expert review were included in a draft emergency care EML, which underwent a final in-person consensus process. RESULTS: The final emergency care EML included 213 medicines, 25 of which are not in the 2017 WHO EML but were deemed essential for clinical practice by regional emergency providers. The final EML has associated recommendations of desirable or essential, and is subdivided by facility level. Thirty-nine medicines were recommended for basic facilities, an additional 96 for intermediate facilities (e.g. district hospitals), and an additional 78 for advanced facilities (e.g. tertiary centres). CONCLUSION: The 25 novel medications not currently on the WHO EML should be considered by planners when making rational formularies for developing emergency care systems. It is our hope that these resource-stratified lists will allow for easier implementation, and will be a useful tool for practical expansion of emergency care delivery in Africa.

Essential medicines for emergency care in Africa

Essential medicines lists (EMLs) are efficient means to ensure access to safe and effective medications.The WHO has led this initiative, generating a biannual EML since 1977. Nearly all countries have implemented national EMLs based on the WHO EML. Although EMLs have given careful consideration to many public health priorities, they have yet to comprehensively address the importance of medicines for treating acute illness and injury.Methods:We undertook a multi-step consensus process to establish an EML for emergency care in Africa. After a review of existing literature and international EMLs, we generated a candidate list for emergency care. This list was reviewed by expert clinicians who ranked the medicines for overall inclusion and strength of recommendation. These medications and recommendations were then evaluated by an expert group. Medications that reached consensus in both the online survey and expert review were included in a draft emergency care EML, which underwent a final in-person consensus process.Results:The final emergency care EML included 213 medicines, 25 of which are not in the 2017 WHO EML but were deemed essential for clinical practice by regional emergency providers. The final EML has associated recommendations of desirable or essential, and is subdivided by facility level. Thirty-nine medicines were recommended for basic facilities, an additional 96 for intermediate facilities (e.g. district hospitals), and an additional 78 for advanced facilities (e.g. tertiary centres).Conclusion:The 25 novel medications not currently on the WHO EML should be considered by planners when making rational formularies for developing emergency care systems. It is our hope that these resource-stratified lists will allow for easier implementation, and will be a useful tool for practical expansion of emergency care delivery in Africa

Plasmin and coagulant activities in a minicurd model system: Study of technological parameters.

The effect of scalding temperature of the curd, the inclusion of a washing step, and the pH at whey drainage on plasmin and coagulant activities were assessed in a minicurd model of young hard cooked cheese. The variables were tested as follows: draining pH was assayed at 3 levels (4.6, 5.6, and 6.4), curd scalding temperature was tested at 50 and 56°C, and washing of the curd was examined at 2 levels (no washing step, and the replacement of the whey by water). Increase in pH at whey drainage and washing of the curd had a positive effect on plasmin activity, which was also evidenced by compatible changes in soluble peptide profiles. No effect of increased cooking temperature was found on plasmin activity. Plasminogen activation was not verified in any treatment. As for coagulant, lower pH values at whey drainage and a decrease in curd cooking temperature increased its activity; washing of the curd showed no influence on coagulant residual activity. These results were consistent with proteolysis described by peptide profiles, electrophoresis, and soluble nitrogen fractions.

Short communication: A new minicurd model system for hard cooked cheeses.

The aim of this study was to propose and validate a new minicurd model of young hard cheese. Curd particles and whey obtained from conventional cheese making of Reggianito Argentino were separated and frozen. Then, both fractions were thawed and the mixture of whey and curds was reconstituted, from which minicurds were made on the laboratory scale. Repeatability and the effect of freezing on minicurd composition were investigated by assessing pH, protein and moisture contents, sodium chloride content, and total thermophilic lactic flora counts. Good repeatability was achieved, and no significant differences were found between minicurds made from fresh compared with frozen materials. Composition of the minicurd was appropriate for modeling Reggianito Argentino cheese.

Growth, survival, and peptidolytic activity of Lactobacillus plantarum I91 in a hard-cheese model.

In this work, we studied the growth, survival, and peptidolytic activity of Lactobacillus plantarum I91 in a hard-cheese model consisting of a sterile extract of Reggianito cheese. To assess the influence of the primary starter and initial proteolysis level on these parameters, we prepared the extracts with cheeses that were produced using 2 different starter strains of Lactobacillus helveticus 138 or 209 (Lh138 or Lh209) at 3 ripening times: 3, 90, and 180 d. The experimental extracts were inoculated with Lb. plantarum I91; the control extracts were not inoculated and the blank extracts were heat-treated to inactivate enzymes and were not inoculated. All extracts were incubated at 34°C for 21 d, and then the pH, microbiological counts, and proteolysis profiles were determined. The basal proteolysis profiles in the extracts of young cheeses made with either strain tested were similar, but many differences between the proteolysis profiles of the extracts of the Lh138 and Lh209 cheeses were found when riper cheeses were used. The pH values in the blank and control extracts did not change, and no microbial growth was detected. In contrast, the pH value in experimental extracts decreased, and this decrease was more pronounced in extracts obtained from either of the young cheeses and from the Lh209 cheese at any stage of ripening. Lactobacillus plantarum I91 grew up to 8 log during the first days of incubation in all of the extracts, but then the number of viable cells decreased, the extent of which depended on the starter strain and the age of the cheese used for the extract. The decrease in the counts of Lb. plantarum I91 was observed mainly in the extracts in which the pH had diminished the most. In addition, the extracts that best supported the viability of Lb. plantarum I91 during incubation had the highest free amino acids content. The effect of Lb. plantarum I91 on the proteolysis profile of the extracts was marginal. Significant changes in the content of free amino acids suggested that the catabolism of free amino acids by Lb. plantarum I91 prevailed in a weakly proteolyzed medium, whereas the release of amino acids due to peptidolysis overcame their catabolism in a medium with high levels of free amino acids. Lactobacillus plantarum I91 was able to use energy sources other than lactose to support its growth because equivalent numbers of cells were observed in extracts containing residual amounts of lactose and in lactose-depleted extracts. The contribution of Lb. plantarum I91 to hard-cooked cheese peptidolysis was negligible compared with that of the starter strain; however, its ability to transform amino acids is a promising feature of this strain.

Two strains of nonstarter lactobacilli increased the production of flavor compounds in soft cheeses.

The contribution to flavor generation and secondary proteolysis of 2 strains of mesophilic lactobacilli isolated from cheese was studied. Miniature soft cheeses (200 g) were produced with or without the inclusion of a culture of Lactobacillus plantarum I91 or Lactobacillus casei I90 in the starter composed of Streptococcus thermophilus. During ripening, cheeses containing the added lactobacilli showed an increased content of total free amino acids, but this increase was only significant in cheeses with Lb. plantarum I91. In addition, free amino acid profiles were modified by selective increases of some amino acids, such as Asp, Ser, Arg, Leu, and Phe. Cheeses inoculated with Lb. plantarum I91 or Lb. casei I90 were also characterized by a significantly higher concentration of diacetyl, a key flavor compound, and an increased content of acetoin. Results suggest an increase in the catabolism of either citrate or aspartate, with the production of the derived aroma compounds. Overall, aspartate content increased in both lactobacilli-added cheeses, whereas citrate was more or less constant, suggesting that aspartate could be the source of increased diacetyl and acetoin. A triangle aroma test showed that the addition of the lactobacilli strains significantly changed the sensory attributes of cheeses. At least 11 of 12 panelists commented that the aroma of cheeses with adjuncts was more buttery than that of control cheeses, which is desirable in most soft cheeses. Both Lb. plantarum I91 and Lb. casei I90 performed well as adjunct cultures by influencing cheese aroma development and cheese proteolysis.

Influence of milk pretreatment on production of free fatty acids and volatile compounds in hard cheeses: heat treatment and mechanical agitation.

This work aimed to identify technological steps that can increase fat hydrolysis and volatile compounds production in hard cheeses; these biochemical events have been related with improved piquant taste and development of genuine flavor during cheese ripening. For that purpose, 2 different pretreatments of cheese milk were tested: heat treatment and mechanical agitation. Both factors were assayed at 2 levels: milk was either batch pasteurized or nonthermally treated, and mechanical agitation was either applied or not applied. For all combinations, hard cheeses (Reggianito type) were produced in a pilot plant and ripened for 90 d. In all cheeses the degree of lipolysis, assessed by gas chromatography, increased similarly during ripening. However, the proportion of short-chain fatty acids was higher in the cheeses made with unpasteurized milk, suggesting a higher activity of lipases with positional specificity toward the sn-3 position of the triglyceride, among which milk lipoprotein lipase is found. Similar results were found for most of the volatile compounds, determined by solid-phase microextraction-gas chromatography flame-ionization detector/mass spectrometry, which constitute the groups of ketones, alcohols, esters, and the group of acids. On the contrary, no effect of mechanical agitation was observed, although some interactions between factors were found. In the conditions of the study, results suggest that heat treatment had a higher effect on cheese lipolysis and volatile compounds production than partial destabilization of the fat emulsion produced by the agitation method applied.

Levonorgestrel, not etonogestrel, provides contraception in free-ranging koalas.

Management of high-density koala (Phascolarctos cinereus) populations is essential because of the browsing damage they inflict on their habitat. We have tested two types of gestagen implant, namely levonorgestrel and etonogestrel, as contraceptives for koalas. Free-ranging female koalas were given either a control, levonorgestrel (70 mg) or etonogestrel (34 or 68 mg) implant before the breeding season. Koalas were monitored every 4-12 weeks for births. Plasma progesterone was measured and a cytological smear of the urogenital sinus was taken. Fertility was high in the control group and the two etonogestrel-treated groups, with approximately 90% of females giving birth. In contrast, no levonorgestrel-treated female produced young during the study. Removal of levonorgestrel implants from six females reversed the contraceptive effect in the next breeding season, whereas the eight females in which the levonorgestrel implants were left in remained infertile for six breeding seasons. Vaginal cytology showed evidence of oestrous cycles during the breeding season in all females from all groups and there was no difference seen in the prevalence of cornified epithelial cells in the oestrous smears. This indirectly suggests that levonorgestrel does not prevent follicular development and oestrous cycling. Plasma progesterone in levonorgestrel-treated females remained low all year, but rose in controls concurrent with the onset of the breeding season. This suggests that levonorgestrel prevents pregnancy by blocking ovulation. Etonogestrel had absolutely no contraceptive effect at the two doses delivered and so is not suitable for controlling koala populations. In contrast, levonorgestrel was effective as a long-term, reversible contraceptive in wild koalas.

Multivariate analysis of proteolysis patterns differentiated the impact of six strains of probiotic bacteria on a semi-hard cheese.

The individual contribution of 6 strains of probiotic bacteria (3 of Lactobacillus acidophilus and 3 of the Lactobacillus casei group) to proteolysis patterns in a semi-hard cheese was assessed. Control cheeses (without probiotics) and 2 types of experimental cheeses (with the addition of probiotics either directly to milk or by a 2-step fermentation method) were manufactured. Cheeses containing Lb. acidophilus showed the most extensive peptidolysis, which was evidenced by changes in the peptide profiles and a noticeable increase of free amino acids compared with control cheeses. The strains of the Lb. casei group showed a lower contribution to cheese peptidolysis, which consisted mainly of free amino acid increase. Two-step fermentation improved peptidolytic activity for only one of the cultures of Lb. acidophilus tested. The addition of Lb. acidophilus strains into cheese may be suitable not only for their beneficial health effect but also for their influence on secondary proteolysis, consistent with acceleration of ripening and improved flavor formation.

Impact of chymosin- and plasmin-mediated primary proteolysis on the growth and biochemical activities of lactobacilli in miniature Cheddar-type cheeses.

Strongly proteolytic starters seem to improve the growth of nonstarter lactobacilli during cheese ripening, but no information is available on the impact of the nonmicrobial proteases usually active in cheese on their development. In the current study, the influence of chymosin- and plasmin-mediated proteolysis on the growth and biochemical activities of lactobacilli during ripening of miniature Cheddar-type cheeses, manufactured under controlled microbiological conditions, was studied. Two experiments were performed; in the first, residual chymosin activity was inhibited by the addition of pepstatin, and in the second, plasmin activity was increased by adding more enzyme, obtained in vitro through the activation of plasminogen induced by urokinase. Cheeses with or without a Lactobacillus plantarum I91 adjunct culture and with or without added pepstatin or plasmin solution were manufactured and ripened for 60 d. The addition of the adjunct culture resulted in enhancement of secondary proteolysis, evidenced by an increase in the total content of free amino acids (FAA) and modifications of the individual FAA profiles. Reduction in residual chymosin activity caused a decrease in primary and secondary proteolysis, characterized by the absence of alpha(s1)-casein hydrolysis and reduced production of peptides and FAA, respectively. The increase in plasmin activity accelerated primary proteolysis but no enhancement of secondary proteolysis was observed. Chymosin- and plasmin-mediated proteolysis did not influence the growth and biochemical activities of adventitious or adjunct lactobacilli, indicating that it is not a limiting factor for the development and proteolytic-peptidolytic activities of lactobacilli in the cheese model studied.

Viability and contribution to proteolysis of an adjunct culture of Lactobacillus plantarum in two model cheese systems: cheddar cheese-type and soft-cheese type.

AIMS: The influence of the cheese-making process, ripening conditions and primary starter on the viability and proteolytic activity of an adjunct culture of Lactobacillus plantarum I91 was assessed in two miniature cheese models, representative of Cremoso Argentino and Cheddar cheeses. METHODS AND RESULTS: Cheeses with and without adjunct culture were made under controlled microbiological conditions and sampled during ripening for physicochemical and microbiological analyses. The addition of lactobacilli neither contributed to acid production nor caused changes to the composition of the cheeses. The strain studied exhibited good development and survival and showed a similar growth pattern in both cheese matrices. The adjunct culture caused changes to secondary proteolysis of both cheese types, which were evidenced by modification of peptide profiles and the increase in the levels of some individual amino acids as well as the total content of free amino acids. The changes observed were consistent with the acceleration of proteolysis in the two cheese models assayed. CONCLUSION: Lactobacillus plantarum I91 has desirable and robust technological properties, which makes it a suitable adjunct culture for cheese-making. SIGNIFICANCE AND IMPACT OF THE STUDY: Other cultures and environmental conditions prevailing in the food may affect the viability of adjunct cultures and its biochemical activities; this is the first report describing the successful performance of an adjunct culture of Lact. plantarum I91 in two different model cheese systems.

Color Doppler imaging of retrobulbar hemodynamics in Sturge-Weber syndrome-associated glaucoma.

PURPOSE: Sturge-Weber syndrome (SWS) is frequently associated with early onset glaucoma in the eye on the same side as the facial angioma. The exact cause of glaucoma in SWS is poorly understood and difficult to treat. The purpose of this study is to investigate the ocular hemodynamics of children with SWS-associated glaucoma using color Doppler imaging techniques. METHODS: This is a prospective study of 10 pediatric patients with unilateral SWS-associated glaucoma. Color Doppler imaging was used to measure the peak systolic velocity and the end diastolic velocity of both the ophthalmic and central retinal arteries in the glaucomatous eye compared to the fellow healthy eye. RESULTS: Twenty eyes of 10 children with SWS (6 boys) with unilateral glaucoma were included in the prospective study. The mean age of the 10 participants was 5.5 years. When compared to their contralateral normal eyes, the glaucomatous eyes had greater CDR (p<0.001) and a myopic shift (p=0.04). No significant differences were found in the measurements of ocular blood flow velocities of the ophthalmic and central retinal arteries. CONCLUSIONS: Vascular pathology has been proposed to play a role in SWS glaucoma etiology. The authors did not find arterial retrobulbar blood flow differences between the glaucomatous and the fellow normal eye. Since the primary vascular anomaly in patients with SWS is in the venous plexus, a bigger prospective trial is warranted in order to better understand and treat children with SWS glaucoma.

Nonstarter Lactobacillus strains as adjunct cultures for cheese making: in vitro characterization and performance in two model cheeses.

Nonstarter lactic acid bacteria are the main uncontrolled factor in today's industrial cheese making and may be the cause of quality inconsistencies and defects in cheeses. In this context, adjunct cultures of selected lactobacilli from nonstarter lactic acid bacteria origin appear as the best alternative to indirectly control cheese biota. The objective of the present work was to study the technological properties of Lactobacillus strains isolated from cheese by in vitro and in situ assays. Milk acidification kinetics and proteolytic and acidifying activities were assessed, and peptide mapping of trichloroacetic acid 8% soluble fraction of milk cultures was performed by liquid chromatography. In addition, the tolerance to salts (NaCl and KCl) and the phage-resistance were investigated. Four strains were selected for testing as adjunct cultures in cheese making experiments at pilot plant scale. In in vitro assays, most strains acidified milk slowly and showed weak to moderate proteolytic activity. Fast strains decreased milk pH to 4.5 in 8 h, and continued acidification to 3.5 in 12 h or more. This group consisted mostly of Lactobacillus plantarum and Lactobacillus rhamnosus strains. Approximately one-third of the slow strains, which comprised mainly Lactobacillus casei, Lactobacillus fermentum, and Lactobacillus curvatus, were capable to grow when milk was supplemented with glucose and casein hydrolysate. Peptide maps were similar to those of lactic acid bacteria considered to have a moderate proteolytic activity. Most strains showed salt tolerance and resistance to specific phages. The Lactobacillus strains selected as adjunct cultures for cheese making experiments reached 10(8) cfu/g in soft cheeses at 7 d of ripening, whereas they reached 10(9) cfu/g in semihard cheeses after 15 d of ripening. In both cheese varieties, the adjunct culture population remained at high counts during all ripening, in some cases overcoming or equaling primary starter. Overall, proximate composition of cheeses with and without added lactobacilli did not differ; however, some of the tested strains continued acidifying during ripening, which was mainly noticed in soft cheeses and affected overall quality of the products. The lactobacilli strains with low acidifying activity showed appropriate technological characteristics for their use as adjunct cultures in soft and semihard cheeses.

Proteolysis in Mozzarella cheeses manufactured by different industrial processes.

The objective of the present study was to investigate the influence of stretching temperature, fat content, and time of brining on proteolysis during ripening of Mozzarella cheeses. Seventeen cheese-making experiments (batches) were carried out on an industrial scale on successive days, following the standard procedure with some modifications. Fat content of cheese milk, temperature at the stretching step, and time of brining varied from one batch to another as required by the experimental design, outlined by a surface response model. Proteolysis was assessed during ripening of samples, which was prolonged for at least 3 mo, by means of electrophoresis, nitrogen fractions, and soluble peptide mapping. The amount of soluble nitrogen at pH 4.6 was not significantly different in cheeses obtained by diverse procedures, but it increased during ripening of all samples. This result was coincident with the breakdown of alpha(s1)- and beta-caseins evidenced by electrophoresis, which reached similar extents at late stages of ripening, regardless of the cheese-making process. Multivariate analysis on soluble peptide profiles obtained by liquid chromatography also detected sample grouping according to ripening time, but did not evidence any separation caused by the cheese-making technology. We concluded that the changes in the cheese-making process assayed in this work were insufficient to produce significant differences in proteolysis of the cheeses. Ripening time had more influence on proteolysis of Mozzarella cheeses than any other assayed variable.

Influence of residual milk-clotting enzyme on alpha(s1) casein hydrolysis during ripening of Reggianito Argentino cheese.

Milk-clotting enzyme is considered largely denatured after the cooking step in hard cheeses. Nevertheless, typical hydrolysis products derived from rennet action on alpha(s1)-casein have been detected during the ripening of hard cheeses. The aim of the present work was to investigate the influence of residual milk-clotting enzyme on alpha(s1)-casein hydrolysis in Reggianito cheeses. For that purpose, we studied the influence of cooking temperature (45, 52, and 60 degrees C) on milk-clotting enzyme residual activity and alpha(s1)-casein hydrolysis during ripening. Milk-clotting enzyme residual activity in cheeses was assessed using a chromatographic method, and the hydrolysis of alpha(s1)-casein was determined by electrophoresis and high performance liquid chromatography. Milk-clotting enzyme activity was very low or undetectable in 60 degrees C- and 52 degrees C-cooked cheeses at the beginning of the ripening, but it increased afterwards, particularly in 52 degrees C-cooked cheeses. Cheese curds that were cooked at 45 degrees C had higher initial milk clotting activity, but also in this case, there was a later increase. Hydrolysis of alpha(s1)-casein was detected early in cheeses made at 45 degrees C, and later in those made at higher temperatures. The peptide alpha(s1)-I was not detected in 60 degrees C-cooked cheeses. The results suggest that residual milk-clotting enzyme can contribute to proteolysis during ripening of hard cheeses, because it probably renatures partially after the cooking step. Consequently, the production of peptides derived from alpha(s1)-casein in hard cheeses may be at least, partially due to this proteolytic agent.

Proteolysis on Reggianito Argentino cheeses manufactured with natural whey cultures and selected strains of Lactobacillus helveticus.

Reggianito Argentino cheese is traditionally manufactured with whey starter cultures that provide typical and intense flavor but can cause poor quality standardization. In this study, the influence of natural and selected starters on Reggianito Argentino cheese proteolysis was investigated. Cheeses were manufactured with three strains of Lactobacillus helveticus (SF133, SF138 and SF209) cultured individually in sterile whey and used as single or mixed starters. Control cheeses were made with natural whey starter culture. Cheeses were analyzed to determine gross composition, as well as total thermophilic lactic flora. Proteolysis was assessed by N fractions, electrophoresis and liquid chromatography. Gross composition of the cheeses did not significantly differ, while viable starter cell counts were lower for cheeses made with strain SF209 alone or combined with other strains. Soluble N at pH 4.6 was the same for cheeses made with natural or selected starters, but soluble N in 12% trichloroacetic acid and 2.5% phosphotungstic acid was significantly higher in cheeses made with starters containing strain SF209. Nitrogen fractions results indicated that natural whey starter cultures could be replaced by several starters composed of the selected strains without significant changes to proteolysis patterns. Starter cultures prepared only with SF209 or with the three selected L. helveticus strains produced cheese products with significantly more proteolysis than control cheeses. Chromatographic profiles analyzed by principal components showed that three main peaks on chromatograms, presumptively identified as Tyr, Phe, and Trp, explained most of variability. Principal component scores indicated that cheese samples were grouped by ripening time, which was confirmed by linear discriminant analysis. On the contrary, samples did not cluster by Lactobacillus strain or type of starter.

Influence of milk-clotting enzyme concentration on the alphas1-casein hydrolysis during soft cheeses ripening.

We studied the influence of the dose of milk-clotting enzyme on alphas1-CN degradation, soluble nitrogen production, and sensory profile for an Argentinean soft cheese: Cremoso Argentino. Five different types of cheeses were produced: 1) control cheeses with normal technology, 2) cheeses with inactivated milk-clotting enzyme, 3) cheeses with inactivated milk-clotting enzyme, without starter (acidified with glucono delta lactone), 4) cheeses with a half dose of milk-clotting enzyme, and 5) cheeses with a double dose of milk-clotting enzyme. Proteolysis was assessed by isoelectric focusing electrophoresis of the insoluble fraction at pH 4.6, followed by densitometric quantification. Soluble nitrogen at pH 4.6, expressed as a percentage of total nitrogen and defined as ripening index was also performed. A sensorial panel evaluated the cheeses at the end of ripening. The hydrolysis level of alphas1-CN depended on the milk-clotting enzyme dose used in cheese making. Cheeses without active coagulant did not show degradation at the end of ripening, while cheeses with half and whole doses showed proportional degradations to coagulant dose. Cheese with a double dose of coagulant did not show higher alphas1-CN hydrolysis than normal cheese. No difference was found between cheeses with and without microbiological starter, indicating that the selected culture, composed of thermophilic strains, was unable to attack the whole casein. A high linear correlation was found between ripening index and the relation Sensorial characteristics of cheeses agree with objective analysis. Cheeses without active coagulant were hard and crumbly, while cheeses with normal dose were soft and creamy.

Efecto de la adición de proteínas de suero sobre la elaboración y la calidad del queso cremoso argentino / Effect of the increase of the milk proteins in quality of argentine milk

Realizó un estudio en laboratorio y planta piloto acerca de lai nfluencia del agregado de ricota (proteínas de suero) sobre la tecnología, las características organolépticas y el rendimiento del queso Cremoso Argentino.