Three Prospective Case Studies Examining Mifepristone's Efficacy in Patients with Treatment-Resistant PTSD.

Despite the availability of various treatment approaches for patients with posttraumatic stress disorder (PTSD), some patients do not respond to these therapies, and novel treatment approaches are needed. This study investigated the efficacy of mifepristone, a glucocorticoid receptor antagonist, in treatment-resistant PTSD patients. Three patients with PTSD who were resistant to standard psychological and pharmacological treatments were prescribed mifepristone (600-1,200 mg/day) for 1 week. A baseline-controlled single-case design was used, involving a 2-week baseline phase (no intervention), a 1-week intervention phase (mifepristone), and a 2-week postintervention phase. The primary outcome measure, self-reported PTSD symptom severity (PCL-5), was assessed daily, with participants providing their own control condition. Two of the three patients experienced a significant reduction in PTSD symptom severity after the intervention phase and no longer met the diagnostic criteria for PTSD. These positive results were maintained during long-term follow-up. These findings support the potential effectiveness of mifepristone in the treatment of patients with treatment-resistant PTSD. However, our findings must be interpreted with caution, and further studies with larger sample sizes and more rigorous designs are necessary to confirm the promising results.

Sleep spindle dynamics suggest over-consolidation in post-traumatic stress disorder.

Devastating and persisting traumatic memories are a central symptom of post-traumatic stress disorder (PTSD). Sleep problems are highly co-occurrent with PTSD and intertwined with its etiology. Notably, sleep hosts memory consolidation processes, supported by sleep spindles (11-16 Hz). Here we assess the hypothesis that intrusive memory symptoms in PTSD may arise from excessive memory consolidation, reflected in exaggerated spindling. We use a newly developed spindle detection method, entailing minimal assumptions regarding spindle phenotype, to assess spindle activity in PTSD patients and traumatized controls. Our results show increased spindle activity in PTSD, which positively correlates with daytime intrusive memory symptoms. Together, these findings provide a putative mechanism through which the profound sleep disturbance in PTSD may contribute to memory problems. Due to its uniform and unbiased approach, the new, minimal assumption spindle analysis seems a promising tool to detect aberrant spindling in psychiatric disorders.

Cluster B versus Cluster C Personality Disorders: A Comparison of Comorbidity, Suicidality, Traumatization and Global Functioning.

A general clinical assumption states that cluster B personality disorders (PDs) represent a more severe form of PD than cluster C PDs. Consequently, most PD research is centered on cluster B PDs (especially borderline PD). Yet, prevalence ratings of cluster C PDs exceed those of cluster B PDs. In this explorative, cross-sectional study, we compared cluster B and C PD patients (N = 94) on a wide range of clinically-relevant severity measures, including comorbidity, suicidality, (childhood) traumatization and global functioning. Results showed that, although cluster B PD patients suffered more often from substance use disorders and lifetime suicide attempts, no difference could be established between groups for all other severity measures, including trauma variables. In our study, we additionally included a group of combined cluster B and C PDs, who were largely similar to both other groups. Although our study is insufficiently powered to claim a significant non-difference, these findings emphasize that high rates of comorbidity, suicidality, childhood traumatization and functional impairment apply to both cluster B and C patients. As such, our findings encourage more research into cluster C PDs, ultimately leading to more evidence-based treatments for this prevalent patient group. In addition, the high level of traumatization across groups calls for a routine trauma screening, especially since PD treatment may benefit from concurrent trauma treatment.

Feeding hydrogenated palm fatty acids and rumen-protected protein to lactating Holstein-Friesian dairy cows modifies milk fat triacylglycerol composition and structure, and solid fat content.

The aim of this study was to analyze the effect of fat and protein supplementation to dairy cattle rations on milk fat triacylglycerol (TAG) composition, fatty acid (FA) positional distribution in the TAG structure, and milk solid fat content (SFC). Fifty-six lactating Holstein-Friesian cows were blocked into 14 groups of 4 cows and randomly assigned 1 of 4 dietary treatments fed for 28 d: (1) low protein, low fat, (2) high protein, low fat, (3) low protein, high fat, and (4) high protein, high fat. The high protein and high fat diets were obtained by isoenergetically supplementing the basal ration (low protein, low fat) with rumen-protected soybean meal and rumen-protected rapeseed meal, and hydrogenated palm FA (mainly C16:0 and C18:0), respectively. Fat supplementation modified milk TAG composition more extensively compared with protein supplementation. Fat supplementation resulted in decreased concentrations of the low molecular weight TAG carbon number (CN) 26 to CN34 and medium molecular weight TAG CN40, CN44, and CN46, and increased concentrations of CN38 and the high molecular weight TAG CN50 and CN52. Increased contents of C16:0, C18:0, and C18:1cis-9 in TAG in response to fat supplementation were related to increases in the relative concentrations of C16:0 and C18:0 at the sn-2 position and C18:0 and C18:1cis-9 at the sn-1(3) positions of the TAG structure. Increased concentrations of high molecular weight TAG species CN50 and CN52 in response to fat supplementation was associated with increased milk SFC at 20, 25, and 30°C. Our study shows that important alterations in milk TAG composition and structure occur when feeding hydrogenated palm FA to lactating dairy cattle, and that these alterations result in an increased SFC of milk fat. These changes in milk SFC and TAG composition and structure may improve absorption of both fat and minerals in milk-based products for infants and may affect processing of milk fat.

Associations between personality traits and suicidal ideation and suicide attempts in patients with personality disorders.

INTRODUCTION: People with personality disorders (PDs) have an elevated suicide risk. However, correlates of suicidal ideation (SI) and suicide attempts (SA) remain largely unknown in this population. A growing body of literature highlights the contribution of the Big Five personality traits in suicide-outcomes. Therefore, the present study investigates the association between the Big Five personality traits and SI and SA in people with PDs while applying the ideation-to-action framework. METHOD: Data were obtained from 105 treatment-seeking individuals diagnosed with PDs participating in the Trauma tO Personality Spectrum Study (TOPSS). Multinomial logistic regression analyses were used to analyze the association between the NEO Five-Factor Inventory and the three category suicide-outcome: non-suicidal, SI, and SA. RESULTS: After controlling for age, gender, a comorbid depressive disorder, the severity of borderline manifestations, and other personality traits from the Big Five taxonomy, significantly lower levels of extraversion were observed in participants with SI compared to non-suicidal participants (OR = 0.27, 95% CI 0.10-0.72) but not in SA participants. In contrast, higher levels of extraversion were associated with SA when compared to SI (OR = 3.52, 95% CI 1.33-9.32). Other Big Five traits were not independently associated with suicide-outcomes. CONCLUSIONS: Of the Big Five traits, the introversion-extraversion dimension most clearly distinguishes individuals with SI from non-suicidal individuals, as well as those with a SA in the past from those with SI only. Prospective studies are required to investigate if this personality trait can predict the progression from being non-suicidal to having SI and from having SI to performing an attempt.

Disturbed Sleep in PTSD: Thinking Beyond Nightmares.

Sleep disturbances frequently co-occur with posttraumatic stress disorder (PTSD). Insomnia and nightmares are viewed as core symptoms of PTSD. Yet, relations between disturbed sleep and PTSD are far more complex: PTSD is linked to a broad range of sleep disorders and disturbed sleep markedly affects PTSD-outcome. This article provides a concise overview of the literature on prevalent comorbid sleep disorders, their reciprocal relation with PTSD and possible underlying neurophysiological mechanisms. Furthermore, diagnostic procedures, standard interventions-particularly first choice non-pharmacological therapies-and practical problems that often arise in the assessment and treatment of sleep disturbances in PTSD are described. Finally, we will present some perspectives on future multidisciplinary clinical and experimental research to develop new, more effective sleep therapies to improve both sleep and PTSD.

Seasonal variation in the positional distribution of fatty acids in bovine milk fat.

The aim of this study was to determine the seasonal variation in the positional distribution of fatty acids (FA) in bovine milk fat. Bovine milk samples were collected from May 2017 to April 2018 in the Netherlands, and the FA composition in the sn-2 position was determined by using sn-1(3)-selective transesterification of Candida antarctica lipase B. The majority of the FA showed significant variation at sn-2 and sn-1(3) positions between different seasons. The seasonal variation in sn-2 position was higher than the sn-1(3) positions. Parallel to the changes in the diet of the cows throughout a year, we observed an increase in blood-derived FA (i.e. C18:0, C18:1 cis-9) concentrations and a decrease in de novo-synthesized FA during summer. In winter, more saturated FA were esterified in sn-2 position of milk fat. Highest concentrations of palmitic acid, C16:0, was observed in sn-2 position in winter, whereas the amount of unsaturated FA at this position was highest in summer. These results showed that the FA compositions in different regiospecific positions changed due to season; however, the proportions of a specific FA within the 3 positions of the triacylglycerols in milk fat did not change upon seasonal variation.

Seasonal variation in fatty acid and triacylglycerol composition of bovine milk fat.

The aim of this study was to assess the effects of seasonal variation on the changes of the fatty acid (FA) and triacylglycerol (TAG) composition of bovine milk fat (MF) in a nonseasonal milking system. Weekly milk samples were collected from 14 dairy factories and pooled per week as representative samples of the average Dutch bovine milk. The sample collection started in May 2017 and finished in April 2018, resulting in a total of 52 samples, corresponding to each week of the year. The samples were analyzed for MF content (%) and FA and TAG composition using gas chromatography with flame-ionization detection. The increased intake of C18:3 cis-9,12,15 through grass feeding in spring and summer was associated with major changes in MF FA composition, including reduced proportions of de novo synthesized FA and presence of several rumen biohydrogenation products and conjugated linoleic acid isomers in MF. These changes in seasonal FA composition had an effect on TAG seasonal variation. The TAG seasonal variation showed that all TAG groups were significantly different between months. The low molecular weight and the medium molecular weight TAG groups increased in winter and decreased in summer, whereas the high molecular weight TAG groups increased in summer and decreased in winter. Based on pooled monthly samples, MALDI-TOF-mass spectrometry allowed the analysis of even- and odd-chain TAG species in MF based on their total carbon number and number of double bonds. These analyses indicated saturated TAG species to be greatest in winter, whereas monounsaturated, polyunsaturated, and odd-chain TAG species were greatest in summer. Our study showed that TAG seasonal variation in a nonseasonal milking system is influenced by the variation in FA composition throughout the seasons.

The Association Between Childhood Trauma and Attachment Functioning in Patients With Personality Disorders.

Attachment (mal)functioning and a history of childhood trauma (CT) are both considered psychological determinants of personality disorders (PDs). Their interaction, however, remains largely uninvestigated. In this study, the authors assessed adult and childhood attachment style in a sample of patients with diverse PDs (N = 75) and determined the relation with both occurrence and severity of CT. The authors found that the sample was characterized by severe attachment malfunctioning and high levels of CT. Using cross-tabulations and analysis of variance, the authors showed that patients with a fearful or dismissive attachment style experienced more severe CT than patients with a preoccupied attachment style. Patients reporting an affectionless control bonding style to either parent suffered frequent and severe CT. Although temporal causality cannot be determined, these findings stress the necessity to screen for CT in PDs and suggest that attachment-centered psychotherapy for these patients may benefit from preceding or concurrent trauma treatment.

The role of borderline personality disorder symptoms on absenteeism & work performance in the Netherlands Study of Depression and Anxiety (NESDA).

BACKGROUND: Symptoms of borderline personality disorder (BPD) were previously found to be associated with decreased work performance, even after controlling for depressive and anxiety disorders. Furthermore, co-occurrence of BPD and affective disorders is common. Therefore, we examined the effect of BPD symptoms on occupational functioning in workers with affective disorders. METHODS: Healthy workers (n = 287), workers with current depression/anxiety only (n = 195), workers with BPD symptoms only (n = 54), and workers with both depression/anxiety and BPD symptoms (n = 103) were selected from the Netherlands Study of Depression and Anxiety (NESDA). Both a categorical and dimensional approach were used to cross-sectionally study the effect of BPD symptoms on work performance and absenteeism. RESULTS: Compared to healthy controls, all symptomatic groups had impaired occupational functioning. Workers with current depression/anxiety had higher long-term absenteeism (OR = 3.59; 95%CI:1.83-7.02) and impaired work performance (OR = 7.81; 95%CI:4.44-13.73), workers with BPD symptoms only had higher impaired work performance (OR = 6.02 95%CI:2.76-13.09), and workers with both depression/anxiety and BPD symptoms had higher long-term absenteeism (OR = 3.66 95%CI:1.69-7.91) and impaired work performance (OR = 10.41 95%CI:5.38-20.15). No difference was found between the (symptomatic) groups. In the dimensional analysis, all associations between BPD symptoms and occupational measures disappeared when depressive symptoms were added. Depressive and BPD symptoms were highly correlated (r = .67). CONCLUSIONS: Our findings confirm that both affective disorders and BPD symptoms are associated with occupational dysfunction. The effect of BPD symptoms however, seems mediated by depressive symptoms. This would suggest that focusing on affective symptoms in occupational health may be effective to improve occupational functioning in persons with BPD.

Characterisation of triacylglycerols from bovine milk fat fractions with MALDI-TOF-MS fragmentation.

In this study, we used MALDI-TOF-MS to profile and characterise the triacylglycerol (TAG) species of anhydrous bovine milk fat (AMF) and its low melting (olein) and high melting (stearin) fractions obtained by dry fractionation. Silver-ion solid phase extraction (Ag+-SPE) cartridges were utilised to separate the TAGs according to saturation degree. Then, several TAG species were selected and fragmented via post-source decay (PSD) fragmentation. MALDI-TOF-MS TAG profiles and fragmentation patterns were compared to the TAG and fatty acid (FA) compositions obtained by gas chromatography-flame ionization detector (GC-FID). We found that, olein was rich in medium length chain TAG species like CN38:0 and CN40:1, whereas stearin was rich in saturated long chain TAG species from CN42:0 to CN52:0. Separation of the TAGs based on saturation degree allowed successful selection of the TAG parent-ion for fragmentation by eliminating the interferences of TAG species that have the same carbon number but vary in number of double bonds. The TAG fragmentation patterns indicated significant differences between AMF, olein and stearin as a result of the dry fractionation process. Compared to AMF, olein yielded in higher fragments of short-chain saturated and middle-chain unsaturated FAs. Whereas, stearin yielded in saturated and monounsaturated long chain FA fragments. Fragmentation of unsaturated long chain TAGs showed that the TAGs in olein contained more C18:1 and C18:2 than that of AMF and stearin. Stearin on the other hand, contained higher amount of TAG species containing C16:0. These results were in line with the FA compositions obtained from GC-FID and suggest that Ag+-SPE cartridges coupled with MALDI-TOF-MS offer an informative and practical approach to characterise fats and oils with complex TAG composition.

Barriers and facilitators to employment in borderline personality disorder: A qualitative study among patients, mental health practitioners and insurance physicians.

BACKGROUND: Borderline personality disorder (BPD) is associated with unemployment and impaired functioning. However, a comprehensive understanding of barriers and facilitators to employment from a multidisciplinary perspective is currently lacking. Therefore, the aim of this qualitative study was to explore barriers and facilitators in gaining and maintaining employment in BPD from the perspectives of patients, mental health practitioners (MHPs) and insurance physicians (IPs). METHODS: Fifteen semi-structured interviews were conducted in patients with BPD and two focus groups were carried out among MHPs (n = 7) and IPs (n = 6) following a thematic content analysis approach. RESULTS: All participants described barriers and facilitators relating to three overall themes: characteristics of BPD, stigma, and support to employment. Barriers to employment mainly related to characteristics of BPD, such as low self-image, difficulty posing personal boundaries, difficulty regulating emotions, and lack of structure. MHPs and IPs additionally mentioned externalization and overestimation of competencies on the part of patients. Enhancing emotion regulation and self-reflection by successful treatment was suggested as a facilitator to enhance employment. Increasing collaboration between mental health and vocational rehabilitation services, and increasing knowledge about BPD, were suggested to increase sustainable employment and decrease stigma. CONCLUSIONS: The present findings revealed that both facilitators and barriers are important in gaining and maintaining employment in BPD in which diminishing symptoms, examining stigma and increasing support to employment are key. As a next step, supported employment strategies that follow patient preferences and integrate employment and mental health services, should be studied in the context of BPD.

The DGAT1 K232A polymorphism and feeding modify milk fat triacylglycerol composition.

In the present study, we aimed to investigate the changes in triacylglycerol (TAG) composition as affected by alterations in the cows' diet due to seasonal variations and genetic factors. For this study, 50 milk fat samples in winter and 50 in summer were used from 25 cows with the DGAT1 KK genotype and 25 cows with the DGAT1 AA genotype. The samples were analyzed for milk fat content (%), fat composition, and TAG composition. We found that the content of TAG species CN54 was higher and that of CN34 and CN36 lower in summer than in winter. This seasonal variation in TAG profile was related to seasonal changes in the fatty acids C14:0, C16:0, C18:0, C18:1 cis-9, total unsaturated fatty acids, and total long-chain fatty acids, most likely resulting from dietary differences between seasons. Furthermore, we quantified the effect of DGAT1 K232A polymorphism on TAG profile and detected a significant effect on TAG species CN36, with higher values for the DGAT1 KK genotype. When adjusting for differences in fat content, we found no significant effects of the DGAT1 K232A polymorphism on TAG profile. We detected a significant interaction between DGAT1 K232A polymorphism and season for TAG species CN42 and CN52; in summer, the KK genotype was associated with higher levels for CN42 than the AA genotype, whereas in winter, the difference between the genotypes was small. For CN52, in summer the AA genotype was associated with higher levels than the KK genotype. In winter, the difference between the genotypes was also small. We show that, regardless of preference for DGAT1 genotype (AA or KK) and depending on the availability of FA according to season, UFA (C18:1 cis-9), short-chain FA (C6:0 and C10:0), and medium-chain FA might be esterified on the glycerol backbone of the TAG, keeping the structure characteristics of each TAG species. To our knowledge, this is the first report on the interaction effect of DGAT1 K232A polymorphism and season on the TAG composition in milk fat.

Borderline personality symptoms and work performance: a population-based survey.

BACKGROUND: This study aims to elucidate the interplay between borderline personality symptoms and working conditions as a pathway for impaired work performance among workers in the general population. METHODS: Cross-sectional data from the Netherlands Mental Health Survey and Incidence Study-2 (NEMESIS-2) were used, including 3672 workers. Borderline personality symptoms were measured with the International Personality Disorder Examination (IPDE) questionnaire. Working conditions (decision latitude, psychological job demands, job security and co-worker support) were assessed with the Job Content Questionnaire (JCQ). Impaired work performance was assessed as total work loss days per month, defined as the sum of days of three types of impaired work performance (inability to work, cut-down to work, and diminished quality at work). These were assessed with the WHO Disability Assessment Schedule (WHO-DAS). Common mental disorders (CMD) were assessed with the Composite International Diagnostic Interview (CIDI). RESULTS: Number of borderline personality symptoms was consistently associated with impaired work performance, even after controlling for type or number of adverse working conditions and co-occurrence of CMD. Borderline personality symptoms were associated with low decision latitude, job insecurity and low co-worker support. The relationship between borderline personality symptoms and work performance diminished slightly after controlling for type or number of working conditions. CONCLUSIONS: The current study shows that having borderline personality symptoms is a unique determinant of work performance. This association seems partially explained through the impact of borderline personality symptoms on working conditions. Future studies are warranted to study causality and should aim at diminishing borderline personality symptoms and coping with working conditions.

Interfacial properties, thin film stability and foam stability of casein micelle dispersions.

Foam stability of casein micelle dispersions (CMDs) strongly depends on aggregate size. To elucidate the underlying mechanism, the role of interfacial and thin film properties was investigated. CMDs were prepared at 4°C and 20°C, designated as CMD4°C and CMD20°C. At equal protein concentrations, foam stability of CMD4°C (with casein micelle aggregates) was markedly higher than CMD20°C (without aggregates). Although the elastic modulus of CMD4°C was twice as that of CMD20°C at 0.005Hz, the protein adsorbed amount was slightly higher for CMD20°C than for CMD4°C, which indicated a slight difference in interfacial composition of the air/water interface. Non-linear surface dilatational rheology showed minor differences between mechanical properties of air/water interfaces stabilized by two CMDs. These differences in interfacial properties could not explain the large difference in foam stability between two CMDs. Thin film analysis showed that films made with CMD20°C drained to a more homogeneous film compared to films stabilized by CMD4°C. Large casein micelle aggregates trapped in the thin film of CMD4°C made the film more heterogeneous. The rupture time of thin films was significantly longer for CMD4°C (>1h) than for CMD20°C (<600s) at equal protein concentration. After homogenization, which broke down the aggregates, the thin films of CMD4°C became much more homogeneous, and both the rupture time of thin films and foam stability decreased significantly. In conclusion, the increased stability of foam prepared with CMD4°C appears to be the result of entrapment of casein micelle aggregates in the liquid films of the foam.

Influence of Lactobacillus plantarum WCFS1 on post-acidification, metabolite formation and survival of starter bacteria in set-yoghurt.

The objectives of this study were to evaluate the growth and survival of the model probiotic strain Lactobacillus plantarum WCFS1 in co-culture with traditional yoghurt starters and to investigate the impact of preculturing on their survival and metabolite formation in set-yoghurt. L. plantarum WCFS1 was precultured under sublethal stress conditions (combinations of elevated NaCl and low pH) in a batch fermentor before inoculation in milk. Adaptive responses of L. plantarum WCFS1 were evaluated by monitoring bacterial population dynamics, milk acidification and changes in volatile and non-volatile metabolite profiles of set-yoghurt. The results demonstrated that sublethal preculturing did not significantly affect survival of L. plantarum WCFS1. On the other hand, incorporation of sublethally precultured L. plantarum WCFS1 significantly impaired the survival of Lactobacillus delbrueckii subsp. bulgaricus which consequently reduced the post-acidification of yoghurt during refrigerated storage. A complementary metabolomics approach using headspace SPME-GC/MS and (1)H NMR combined with multivariate statistical analysis revealed substantial impact of sublethally precultured L. plantarum WCFS1 on the metabolite profiles of set-yoghurt. This study provides insight in the technological implications of non-dairy model probiotic strain L. plantarum WCFS1, such as its good stability in fermented milk and the inhibitory effect on post-acidification.

Minimal inhibitory concentrations of undissociated lactic, acetic, citric and propionic acid for Listeria monocytogenes under conditions relevant to cheese.

Minimal inhibitory concentrations (MICs) of undissociated lactic acid were determined for six different Listeria monocytogenes strains at 30 °C and in a pH range of 4.2-5.8. Small increments in pH and acid concentrations were used to accurately establish the growth/no growth limits of L. monocytogenes for these acids. The MICs of undissociated lactic acid in the pH range of 5.2-5.8 were generally higher than at pH 4.6 for the different L. monocytogenes strains. The average MIC of undissociated lactic acid was 5.0 (SD 1.5) mM in the pH range 5.2-5.6, which is relevant to Gouda cheese. Significant differences in MICs of undissociated lactic acid were found between strains of L. monocytogenes at a given pH, with a maximum observed level of 9.0 mM. Variations in MICs were mostly due to strain variation. In the pH range 5.2-5.6, the MICs of undissociated lactic acid were not significantly different at 12 °C and 30 °C. The average MICs of undissociated acetic acid, citric acid, and propionic acid were 19.0 (SD 6.5) mM, 3.8 (SD 0.9) mM, and 11.0 (SD 6.3) mM, respectively, for the six L. monocytogenes strains tested in the pH range 5.2-5.6. Variations in MICs of these organic acids for L. monocytogenes were also mostly due to strain variation. The generated data contribute to improved predictions of growth/no growth of L. monocytogenes in cheese and other foods containing these organic acids.

Formation of ß Polymorphs in Milk Fats with Large Differences in Triacylglycerol Profiles.

In this study, we characterized the polymorphism of milk fat (MF) with various TAG compositions during isothermal crystallization at 20 °C. TAG composition of MF from seven individual cows was determined using GC-FID and MALDI-TOF MS, and MF polymorphism was studied using X-ray diffraction. Results showed that TAG profile determines the polymorphic behavior of MF. Saturated TAG with carbon numbers 34-38 promoted the formation of α polymorphs, whereas unsaturated TAG with 52-54 promoted the formation of the ß polymorphs. Furthermore, MFs with unsaturated fatty acid profiles were increased in unsaturated TAG with 52-54 carbons. The presence of MF crystals in the ß polymorph has been controversial over the years as most authors mainly find MF crystals in the α and ß' form. In our work, we showed that the ß polymorph is formed in MF on the basis of its TAG composition.

Effect of sublethal preculturing on the survival of probiotics and metabolite formation in set-yoghurt.

The objective of this study was to investigate the effect of preculturing of Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp. lactis BB12 under sublethal stress conditions on their survival and metabolite formation in set-yoghurt. Prior to co-cultivation with yoghurt starters in milk, the two probiotic strains were precultured under sublethal stress conditions (combinations of elevated NaCl and low pH) in a batch fermentor. The activity of sublethally precultured probiotics was evaluated during fermentation and refrigerated storage by monitoring bacterial population dynamics, milk acidification and changes in volatile and non-volatile metabolite profiles of set-yoghurt. The results demonstrated adaptive stress responses of the two probiotic strains resulting in their viability improvement without adverse influence on milk acidification. A complementary metabolomic approach using SPME-GC/MS and (1)H-NMR resulted in the identification of 35 volatiles and 43 non-volatile polar metabolites, respectively. Principal component analysis revealed substantial impact of the activity of sublethally precultured probiotics on metabolite formation demonstrated by distinctive volatile and non-volatile metabolite profiles of set-yoghurt. Changes in relative abundance of various aroma compounds suggest that incorporation of stress-adapted probiotics considerably influences the organoleptic quality of product. This study provides new information on the application of stress-adapted probiotics in an actual food-carrier environment.

Influence of different proteolytic strains of Streptococcus thermophilus in co-culture with Lactobacillus delbrueckii subsp. bulgaricus on the metabolite profile of set-yoghurt.

Proto-cooperation between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus is one of the key factors that determine the fermentation process and final quality of yoghurt. In this study, the interaction between different proteolytic strains of S. thermophilus and L. delbrueckii subsp. bulgaricus was investigated in terms of microbial growth, acidification and changes in the biochemical composition of milk during set-yoghurt fermentation. A complementary metabolomics approach was applied for global characterization of volatile and non-volatile polar metabolite profiles of yoghurt associated with proteolytic activity of the individual strains in the starter cultures. The results demonstrated that only non-proteolytic S. thermophilus (Prt-) strain performed proto-cooperation with L. delbrueckii subsp. bulgaricus. The proto-cooperation resulted in significant higher populations of the two species, faster milk acidification, significant abundance of aroma volatiles and non-volatile metabolites desirable for a good organoleptic quality of yoghurt. Headspace SPME-GC/MS and (1)H NMR resulted in the identification of 35 volatiles and 43 non-volatile polar metabolites, respectively. Furthermore, multivariate statistical analysis allows discriminating set-yoghurts fermented by different types of starter cultures according to their metabolite profiles. Our finding underlines that selection of suitable strain combinations in yoghurt starters is important for achieving the best technological performance regarding the quality of product.