Three different methods of acidifying skim milk(milk starter, whey base starter and direct acid set) for making cottage cheese were evaluated for their effect on yield, quality and acidification cost. Cultured cottage cheese was produced with milk starter and pH controlled whey-base starter by the short set method. Five percent milk starter and 2.4% whey base starter were approximately equivalent in activity and gave average setting times of 234 to 255 minutes. Direct acid set cottage cheese was made by the Vitex/American method. The setting time required for direct acid set cottage cheese was 158 minutes. Yields of cottage cheese made by direct acid set were significantly higher than with the two cultured methods. Mean yield for direct acid set was 16.1%, the milk starter yield was 14.5% and the whey base method gave a yield of 14.8%. Protein in the milk starter was less efficiently recovered in the cottage cheese curd than the protein in pasteurized milk. The direct acid set method produced cottage cheese curd that was more mealy than the curd produced by cultured methods, but was still equal in over-all quality to curd made by milk starter methods. The cottage cheese produced by the different acidification methods were judged superior to commercially made direct acid and commercial cultured cottage cheese by an panel of trained judges. Cottage cheese made by whey base starter was preferred over all of the other cottage cheese. Acidification costs per kilogram of cottage cheese curd were $0.54 for milk starter, $0.019 for whey base starter and $0.114 for direct acid set curd. Overall ingredient cost per 1,000 Kg of skim milk set were $160.04, $154,43 and $170.17 respectively. Saving in time with direct acid set methods probably offset the additional cost of ingredients.

This study sought to investigate the role of the C55 undecaprenol lipid carrier in the production of exopolysaccharide (EPS), the effect of exopolysaccharide producing (EPS+) starter cultures on the viscosity of Mozzarella cheese whey, and the possible protective characteristics of capsular EPS against freezing and freeze drying. Efforts to investigate the role of the lipid carrier in EPS production employed pAMbacA, a plasmid that encodes an enterococcallipid kinase that confers bacitracin resistance by increasing intracellular levels of undecaprenol phosphate lipid carrier. Unfortunately, this avenue of study was thwarted by the inability to demonstrate bacA expression in a model dairy lactic acid bacterium, Lactococcus lactis. To study the effect of EPS+ cultures on cheese whey, Mozzarella cheese was made with starters consisting of Lactobacillus helveticus (LH100) paired with one of four Streptococcus thermophilus strains. These strains included a capsular EPS producer (Cps+) MR-1C; a non-exopolysaccharide producing negative mutant (EPS-) of MR-1C, DM10; a ropy EPS producer, MTC360; and a non-EPS producing industrial strain, TA061. Results showed that Mozzarella cheese made with a Cps+ or ropy EPS+ S. thermophilus strain had significantly higher moisture levels than cheese made with non-exopolysaccharide producing (EPS-) streptococci. Melt properties were also better in cheeses with higher moisture. Viscosity measurements of unconcentrated and ultrafiltered (5-fold concentrated) whey showed that ultrafiltered whey from cheeses made with S. thernzophilus MTC360 was significantly higher in viscosity than whey from cheeses made with MR-1C, TA061, or DM10. There was no significant difference in the viscosity of unconcentrated or concentrated whey from cheese made with S. thermophilus MR-1C and cheese made with the commercial starter culture TA061. The results indicated that non-ropy, encapsulated exopolysaccharideproducing S. thermophilus strains can be used to achieve higher cheese moisture levels and to improve the melt properties of Mozzarella cheese without significantly increasing cheese whey viscosity. Finally, S. thermophilus MR-1C and DM10 were subjected to freezing and freeze drying to test for possible protective effects of the capsular exopolysaccharide. Analysis of variance of cell counts taken before and after freezing or freeze drying cycles revealed there was no significant difference between the viability of these strains.

Five strains of Lactococcus lactis were inoculated individually into six commercial bulk set growth media, 11% non-fat dry milk (NDM), and Elliker's broth. After growth in each medium the strains were tested for rate of acid production, and activities of proteinase, aminopeptidase, and lipase/esterase. Growth in commercial starter media significantly influenced acid production rate (P = 0.040), aminopeptidase activity (P < 0.0001), and lipase/esterase activity (P < 0.0001) . For selected strain/media combinations, the duration of induced aminopeptidase and lipase/esterase activity was followed. The chosen strains were grown in selected commercial bulk set media, reinoculated into 11% NDM, and enzyme activity was examined for five successive generations. During growth in 11% NDM, aminopeptidase and lipase/esterase activity began high and appeared to decrease after approximately two generations, as compared to the control. This study demonstrated that it is possible to select specific starter and media combinations to produce a bacterial phenotype that might not change before the cheese is pressed, thereby trapping bacteria with an altered phenotype within the cheese matrix.

<p>Modern heavy trucks tend to get more and more equipment demanding electric power. As a result, the electric power left for startingbecome more and more limited. If a complete view of the entire starting system-battery, starter and the combustion engine - is used, the total system can be investigated and optimized. This thesis is a study of the starting system and its components. Theories for each component are presented and models are derived for a complete starting system. Focus lies on the battery and starter motor. The purpose of the modelling work is to gain knowledge of the starting system. Some results can also be obtained from the simulations - it is very important to keep the electrical resistance as low as possible and the differences between battery types are surprisingly big.</p>

Modern heavy trucks tend to get more and more equipment demanding electric power. As a result, the electric power left for startingbecome more and more limited. If a complete view of the entire starting system-battery, starter and the combustion engine - is used, the total system can be investigated and optimized. This thesis is a study of the starting system and its components. Theories for each component are presented and models are derived for a complete starting system. Focus lies on the battery and starter motor. The purpose of the modelling work is to gain knowledge of the starting system. Some results can also be obtained from the simulations - it is very important to keep the electrical resistance as low as possible and the differences between battery types are surprisingly big.

Yoghurt is a fermented milk product which is produced by Streptococcus thermophilus and Lactobacillus delbrueckii spp. bulgaricus. The production of yoghurt has started in Middle East and spread all over the world. The aim of this study is to select the culture combination which is appropriate to Turkish taste and have the best yoghurt characteristics by means of post-acidification and whey separation properties, texture of gel formation, exopolysaccharide and acetaldehyde content / and to observe the effect of freeze-drying of cultures on these yoghurt properties. At the first part of this study, six L.delbrueckii spp. bulgaricus isolates and six S.thermophilus isolates were used with different combinations to produce 36 yoghurt samples. These isolates were selected among a strain collection which contains 111 L.delbrueckii spp. bulgaricus and 56 S.thermophilus isolates which were isolated from traditional Turkish yoghurt according to their acidification activity and acetaldehyde production properties. In addition, two commercial S.thermophilus isolates and one commercial L.delbrueckii spp. bulgaricus isolate were used to produce two commercial yoghurt samples. 38 yoghurt samples were examined in terms of pH and total titratable acidity changes during 21-day storage, syneresis and hardness. According to these three analyses, six yoghurt samples were chosen, which give the best results, for the determination of exopolysaccharide and acetaldehyde content. In addition, two yoghurt samples produced by commercial cultures and one sample, which gives average results in experiments, were also examined for these compounds to provide a good comparison. In the second part of the study the amount of exopolysaccharide and acetaldehyde of nine yoghurt samples were determined. In addition, sensory analysis was conducted to see consumer perception. According to the results, one culture combination was obtained as the best combination which produces the appropriate yoghurt to Turkish taste with the closest chemical analysis results to the commercial samples. In the last part, freeze drying process was examined if this has a significant effect on the selected LAB combination as well as yoghurt produced by using this.

Hintergrund: Gestillte Kinder haben im Vergleich zu nicht gestillten Kindern eine geringere Inzidenz von gastrointestinalen Infektionen und atopischen Erkrankungen. Man geht davon aus, dass der gesundheitsfördernde Effekt der Muttermilch teilweise über die intestinale Mikrobiota vermittelt wird. Diese ist in Stillkindern durch eine geringe Diversität und einen hohen Anteil an Bifidobakterien charakterisiert. Neueste Ansätze in der Weiterentwicklung industriell hergestellter Säuglingsnahrung zielen darauf ab, eine intestinale Mikrobiota zu fördern, die der von gestillten Kindern ähnelt. Die Supplementation von Säuglingsnahrung mit Probiotika (lebende Mikroorganismen) oder Präbiotika (unverdauliche Kohlenhydrate, die als Energiesubstrat für probiotische Bakterien dienen) könnte die bifidogene und antipathogene, aber auch immunmodulierende Wirkung der Muttermilch nachahmen. Aufgrund unterschiedlicher Interaktionen mit der Darmmikrobiota und dem Immunsystem fokussiert man mit der gleichzeitigen Gabe von Pro- und Präbiotika (Synbiotika) eine synergistische Wirkung an. Zielstellung und Studiendesign: In einer randomisiert-kontrollierten, klinischen Studie wurde untersucht, ob sich in den ersten drei Lebensmonaten von gesunden und termingerecht geborenen Kindern mit einer Synbiotikum-haltigen Säuglingsnahrung eine intestinale Mikrobiota etabliert, die der von gestillten Kindern gleicht. Das Synbiotikum setzte sich aus Bifidobacterium animalis ssp. lactis CNCM I 3446 (ältere Bezeichnung B. lactis BB-12) und Kuhmilcholigosacchariden zusammen. Die Studie umfasste zwei Gruppen von Kindern, die eine Säuglingsnahrung mit (SYN-Gruppe, n=21) oder ohne Supplement (KON-Gruppe, n=18) erhielten. Gestillte Kinder dienten als Referenz (REF-Gruppe, n=23). Um die Diversität der Bifidobakterien auf Speziesebene umfassend zu charakterisieren, wurden quantitative Real-Time PCR (qPCR)-Verfahren, basierend auf dem single-copy groEL als phylogenetisches Zielgen, zur spezifischen Quantifizierung von zwölf Bifidobakterienspezies in humanen Fäzes entwickelt und validiert. Ergebnisse: Die supplementierte Säuglingsnahrung war gut verträglich und unterstützte eine gesunde Entwicklung; vergleichbare anthropometrische Daten von SYN- und REF-Gruppe. Das Synbiotikum stimulierte selektiv das Wachstum von Laktobazillen und Bifidobakterien. Die Zellzahl für Laktobazillen der SYN-Gruppe war zur REF-Gruppe äquivalent (9,07±0,32 versus 9,90±0,27 log10 Zellen/g Fäzes TM [MW±SEM]; p<0,0019; Äquivalenzdifferenz von 1 log10 Zellen/g Fäzes TM) und höher als in der KON-Gruppe (8,27±0,31 log10 Zellen/g Fäzes TM [MW±SEM]). Die Zellzahl für Bifidobakterien war in der SYN-Gruppe am höchsten (11,54±0,05 versus 11,00±0,17 [REF-Gruppe] und 10,54±0,24 [KON-Gruppe] log10 Zellen/g Fäzes TM [MW±SEM]). In der SYN-Gruppe wurde die höchste Anzahl an Bifidobakterienspezies erfasst (167 mit [128 ohne] B. animalis in 56 Fäzesproben versus 98 und 93 in jeweils 51 Fäzesproben der REF- und KON-Gruppe). Neben Kinder-typischen Spezies wie B. bifidum und B. breve wurden auch Spezies, die für Erwachsene charakteristisch sind (B. adolescentis), häufiger in der SYN-Gruppe als in den Vergleichsgruppen nachgewiesen. Der pH-Wert in Fäzes von Kindern aus der SYN-Gruppe war niedriger als der aus der KON-Gruppe (6,07±0,20 versus 6,45±0,17 [MW±SEM]) und näher an dem von gestillten Kindern mit 5,29±0,12 (MW±SEM). Schlussfolgerung: Die Supplementation einer Säuglingsnahrung mit dem Synbiotikum aus CNCM I-3446 und Kuhmilcholigosacchariden führte zu einer Angleichung in der Zusammensetzung der intestinalen Mikrobiota und des fäkalen pH-Wertes an gestillte Kinder. Die in dieser Arbeit entwickelten groEL-basierten qPCR-Verfahren erlaubten eine spezifische und genaue Analyse der Bifidobakterienpopulation unter dem Einfluss eines Synbiotikums. / Background: Compared to formula-fed infants, breast-fed infants have a reduced incidence of gastrointestinal infections and atopic diseases. The health-promoting effect of breast milk is assumed to be partly mediated by the intestinal microbiota, which is characterized by a low diversity and a high proportion of bifidobacteria. Recent approaches in further development of infant formulae aim at promoting an intestinal microbiota similar to that of breast-fed infants. The supplementation of infant formula with probiotics (live microorganisms) or prebiotics (non-digestible carbohydrates, which serves as energy substrates for probiotic bacteria) could mimic the bifidogenic and antipathogenic, but also immunomodulating effect of breast milk. Due to various interactions with the gut microbiota and the immune system, the simultaneous administration of pro- and prebiotics (synbiotics) is focussed to have a synergistic effect. Objective and study design: In a randomized-controlled, clinical trial healthy full-term infants receiving an infant formula with synbiotic for the first three months of life were studied, whether an intestinal microbiota is induced, which is equivalent to that of breast-fed infants. The synbiotic consisted of Bifidobacterium animalis ssp. lactis CNCM I 3446 (previously known as B. lactis BB-12) and cow milk oligosaccharides. The study comprised two groups of infants receiving a starter formula with (SYN-group, n=21) or without supplement (KON-group, n=18). Breast-fed infants served as a reference (REF-group, n=23). In order to comprehensively characterize the bifidobacteria diversity at species level, quantitative real-time PCR (qPCR) assays based on the single-copy groEL as phylogenetic marker for the specific quantification of twelve bifidobacteria species in human feces were established and validated. Results: The supplemented formula was well tolerated and supported a healthy development; comparable anthropometric data of SYN- and REF-group. The synbiotic selectively stimulated the growth of lactobacilli and bifidobacteria. Lactobacilli levels were equivalent in SYN- and REF-group (9.07±0.32 versus 9.90±0.27 log10 cells/g feces DM [Mean±SEM]; p<0.0019; equivalence margin of 1 log10 cells/g feces DM) and higher than the KON-group (8.27±0.31 log10 cells/g feces DM [Mean±SEM]). The highest levels of bifidobacteria were observed in the SYN-group (11.54±0.05 versus 11.00±0.17 [REF-group] and 10.54±0.24 [KON-group] log10 cells/g feces DM [Mean±SEM]). The highest number of bifidobacteria species were obtained in the SYN-group (167 with [128 without] B. animalis in 56 fecal samples versus 98 and 93 in each of 51 fecal samples of the REF- and KON-group). Beside species, typically found in infants such as B. bifidum und B. breve, also species, which are characteristic for adults (B. adolescentis), were detected more often in the SYN-group than in the other study groups. Fecal pH was lower in the SYN- than in the KON-group 6.07±0.20 versus 6.45±0.17 [Mean±SEM]) and closer to that of breast-fed infants (5.29±0.12 [Mean±SEM]). Conclusion: In infants fed a starter formula supplemented with a synbiotic (CNCM I-3446 and cow milk oligosaccharides), composition of intestinal microbiota and fecal pH were closer to that of breast-fed infants. The groEL-based qPCR-assays, developed in this study, allowed a specific and accurate analysis of the bifidobacterial population in response to the synbiotic intake.

In this study, the physico-chemical chances occurring in white cheese and possible effects of starter culture combinations to the ripening period during 30 days storage examinated. A total of thirty six lactic acid bacteria were isolated from a cheese made witohout using starter culture. For identification gram staining, catalase, gas production and coagulation tests were performed. For determination of species API50 CH (BioM&eacute / rieux) and partial 16S rDNA gene sequence analysis were used. Four cheese were produced, one by using commercial starter culture [Lyofast CMS (Lactococcus lactic subs. lactis and Lactococcus lactis subs. cremoris)]as control the other three by using different combinations of isolates [Lactococcus lactic subs. lactis (13%) +Lactobacillus brevis (40%)+Lactobacillus paracasei (47%) / Lactococcus lactic subs. lactis (36%)+Lactobacillus paracasei (64%) / Lactococus lactis subs. lactis (24,5%)+ Lactobacillus paracasei (28,5%) + Lactobacillus brevis (47%)] Cheese were ripened in 15% saline solution 4 C for 30 days.Samples were taken from each treatment and analyzed on 2nd,15th and 30th days Sensory ,microbiological and chemical properties of the cheese preparations as pH, acidity ,salt,fat,moisture,protein contents during storage period were determined. In this respect effect of using different starter culture combinations on quality of Turkish white chee was determined and Lactococcus lactis subs. lactis(13%)+Lactobacillus brevis (40%)+Lactobacillus paracasei(47%) combination was found as the best and can be suggested as ideal combination for white cheese production.

Στο εισαγωγικό μέρος της διατριβής περιγράφονται επιστημονικά δεδομένα για τους λακτοβάκιλλους, τις ζύμες και άλλους προβιοτικούς μικροοργανισμούς, τη χρήση του κεφίρ, τις μεθόδους και τις εφαρμογές της ακινητοποίησης αλλά και της ξήρανσής των μικροοργανισμών στα τρόφιμα. Επίσης, γίνεται αναφορά στις κατηγορίες των τυριών, τις μικροβιολογικές και βιοχημικές μεταβολές κατά την ωρίμανσή τους, τις αρχικές καλλιέργειες που χρησιμοποιούνται καθώς και τη συμβολή τους στην ανάπτυξη του αρώματος. Οι κύριοι στόχοι της διατριβής αυτής είναι η παραγωγή νέων θερμικά ξηρανθεισών αρχικών καλλιεργειών σε ελεύθερη ή/και ακινητοποιημένη μορφή καθώς και η έρευνα για την καταλληλότητα αυτών στην ωρίμανση σκληρών τυριών. Στη συνέχεια της διατριβής μελετήθηκε η παρασκευή σκληρών τυριών με τη χρήση ελεύθερων και ακινητοποιημένων σε καζεΐνη κυττάρων κεφίρ μετά από λυοφιλίωση ή θερμική ξήρανση. Η θερμική ξήρανση του κεφίρ παρουσιάζει οικονομικό πλεονέκτημα έναντι της λυοφιλίωσης και συνέβαλε σημαντικά στην αύξηση της βιωσιμότητας των κυττάρων, στη δημιουργία οπών, στη βελτίωση των οργανοληπτικών χαρακτηριστικών, στη μείωση των παθογόνων και στην αύξηση του χρόνου συντήρησης των τυριών. Παράλληλα, μελετήθηκαν οι μικροβιακοί πληθυσμοί, η οξύτητα καθώς και η συγκέντρωση των σακχάρων και της αιθανόλης στα δείγματα που ωρίμασαν στους 5, 18 και 22 °C. Τα υψηλά ποσοστά βιωσιμότητας των λακτοβακίλλων αποτελούν ένδειξη για τον προβιοτικό χαρακτήρα των τυριών αυτών. Οι παράμετροι αυτές εξετάστηκαν επίσης σε σκληρά τυριά στα οποία προστέθηκε αρχική καλλιέργεια L. casei. Η συγκέντρωση του L. casei επηρέασε τα μικροβιολογικά, χημικά και οργανοληπτικά χαρακτηριστικά των τυριών. Επιπλέον, μελετήθηκαν το υδατοδιαλυτό άζωτο και ο συντελεστής ωρίμανσης ώστε να διαπιστωθεί πιθανή επιτάχυνση της ωρίμανσης στα τελικά προϊόντα. Ο βαθμός υγιεινής των τυριών εξετάστηκε με τον προσδιορισμό των κολοβακτηρίων, των εντεροβακτηρίων και των πιθανών σταφυλόκοκκων. Η αύξηση στη συγκέντρωση της αρχικής καλλιέργειας L. casei βελτίωσε τα χημικά και οργανοληπτικά χαρακτηριστικά των τυριών αλλά δεν κατάφερε να αποτρέψει την ανάπτυξη των παθογόνων μικροοργανισμών. Αντίθετα, στα σκληρά τυριά με μεικτή αρχική καλλιέργεια L. bulgaricus ή L. helveticus και K. marxianus τα παθογόνα κολοβακτήρια, εντεροβακτήρια και οι πιθανοί σταφυλόκοκκοι μειώθηκαν σημαντικά. Η προσθήκη των αρχικών καλλιεργειών μετά από θερμική ξήρανση εφαρμόστηκε με επιτυχία σε ανάλατα σκληρά τυριά. Ο χρόνος ζωής και τα οργανοληπτικά χαρακτηριστικά των τυριών βελτιώθηκαν με τη χρήση της αρχικής καλλιέργειας. Η ακινητοποίηση των κυττάρων σε καζεΐνη δεν επηρέασε σημαντικά τα ποιοτικά χαρακτηριστικά των τυριών. Μεταξύ των αρχικών καλλιεργειών, τα ελεύθερα κύτταρα κεφίρ έδωσαν τα καλύτερα αποτελέσματα. Η παρασκευή των σκληρών τυριών σε πιλοτική κλίμακα ήταν επίσης ένα από τα αντικείμενα της διατριβής. Η αρχική καλλιέργεια που χρησιμοποιήθηκε ήταν κεφίρ μετά από θερμική ξήρανση σε συγκέντρωση 1,0 g/L γάλακτος. Η ωρίμανση των τυριών πραγματοποιήθηκε στους 12 και 18 °C. Τα αποτελέσματα έδειξαν ότι η ανάπτυξη και η ξήρανση της αρχικής καλλιέργειας είναι εφικτή σε βιομηχανική κλίμακα και η χρήση της για την παραγωγή σκληρών τυριών δίνει προϊόντα υψηλής ποιότητας. Σε αυτό συνέβαλε η σημαντική μείωση των παθογόνων μικροοργανισμών που εξετάστηκαν. Τα τυριά εμφάνισαν βελτιωμένα οργανοληπτικά χαρακτηριστικά και αύξηση του βαθμού δημιουργίας οπών σε ικανοποιητικούς χρόνους ωρίμανσης. Το τελευταίο κεφάλαιο των αποτελεσμάτων της διατριβής ασχολείται με την επίδραση των αρχικών καλλιεργειών στα πτητικά παραπροϊόντα των τυριών. Η ανάλυση των δειγμάτων με την τεχνική SPME-GC/MS έδειξε ότι η χρήση αρχικής καλλιέργειας αύξησε τον αριθμό και τη συγκέντρωση των κύριων συστατικών που συνεισφέρουν στη δημιουργία του αρώματος και δευτερευόντως της γεύσης των τυριών. Η θερμική ξήρανση της καλλιέργειας έδωσε καλύτερα αποτελέσματα σε σχέση με τη λυοφιλίωση. Σημαντική είναι η αύξηση των πτητικών ενώσεων στα ανάλατα σκληρά τυριά με αρχική καλλιέργεια που εξηγεί και τη μεγαλύτερη βαθμολογία που έλαβαν κατά την οργανοληπτική δοκιμασία. Οι μεικτές λοιπόν αρχικές καλλιέργειες που μελετήθηκαν μπορούν να χρησιμοποιηθούν μετά από θερμική ξήρανση για την παραγωγή σκληρών τυριών υψηλής ποιότητας και υγιεινής. Επιπλέον, η εκμετάλλευση του ρυπογόνου τυρογάλακτος για την ανάπτυξη των καλλιεργειών και η εφαρμογή μιας οικονομικά προσιτής μεθόδου ξήρανσης αποτελούν βασικά πλεονεκτήματα της παραγωγικής διαδικασίας σε πιλοτική κλίμακα. Η διατριβή αυτή αποτελεί μια ολοκληρωμένη έρευνα των μικροβιολογικών, χημικών και οργανοληπτικών χαρακτηριστικών στα σκληρά τυριά με τη χρήση θερμικά ξηρανθεισών αρχικών καλλιεργειών. / In the introductory part of this Dissertation, the microbiology and starter culture production of lactobacilli, yeasts, other probiotic microorganisms and kefir are reviewed. Cell immobilization and drying of microorganisms for food production are also reported. Moreover, cheese varieties, microbiological and biochemical changes during ripening of cheeses, starter cultures and their contribution to aroma development are discussed. The aim of the current thesis is the production of new thermally dried starter cultures with free or immobilized cells and their application for the ripening of hard-type cheese. Specifically, the production of cheeses with free and immobilized cells of kefir on casein after freeze-drying or thermal drying were studied. It was found that thermal drying of kefir posseses an economical advantage over freeze-drying and contributes significantly to the extension of shelf life, degree of gas holes and to the improvement of sensory characteristics. Microbial populations, acidity, residual sugars and the ethanol concentration were also determined in the cheese samples ripened at 5, 18 and 22 °C. High viability of lactobacilli shows the probiotic character of these hard-type cheeses. Furthermore, the same parameters were studied in hard-type cheese ripened with L. casei as starter culture. L. casei concentration had a significant effect on the microbiological, chemical and sensory characteristics of cheeses. Water soluble nitrogen and ripening time measurements indicated an acceleration of ripening. Safety and hygiene were determined by measurement of coliforms, enterobacteria and presumptive staphylococci. The increase of starter culture concentration improved chemical and sensory characteristics but pathogens were not inhibited. However, in the case of hard-type cheese using a mixed starter culture of L. bulgaricus or L. helveticus with K. marxianus, pathogens as coliforms, enterobacteria and presumptive staphylococci were significantly reduced. A chapter of this thesis concerns the use of thermally dried starter cultures for the production of unsalted hard-type cheeses. In this case shelf-life and sensory characteristics of the samples were improved by the addition of starter culture. Cell immobilization on casein did not have a significant effect on cheese quality characteristics. The best results were obtained by the use of free cells of kefir starter culture. Scale-up of hard-type cheese production at pilot scale was the final step of this dissertation. In the frame of this chapter, thermally dried kefir at a concentration of 1.0 g/L was used as starter culture and products were ripened at 12 and 18 °C. The results indicate that thermal drying of starter culture is feasible under pilot scale conditions and can be used for products of high quality. Thermal drying of kefir was performed by supplying air of 38 °C on a thin layer of biomass. Pathogen populations were significantly reduced in these products. Cheese samples had improved sensory characteristics and number of eyes in a relatively short ripening time. The last part of the thesis revealed the effect of starter cultures on the major volatiles of cheeses. Sample analysis with SPME-GC/MS technique showed that the addition of starter culture increased the number and the concentration of volatile compounds positively contributing to the aroma of cheeses. Thermal drying of culture gave better results than freeze-drying. The increase of flavor compounds in unsalted hard-type cheeses is important and is confirmed by the high scores that these samples achieved in sensory evaluation. A general conclusion of the thesis is that the mixed starter cultures studied can be successfully used after thermal drying in the ripening of hard-type cheeses. Moreover, the exploitation of whey for starter culture production and the application of the economical and feasible method of thermal drying constitute the main advantages of hard-type cheese production at pilot scale.

The master´s thesis describes the design of the remote control, which is used as accessories for motor circuit-breaker. The work is based on the concept of control realized in the bachelor´s thesis. Master’s thesis contains a literature review of management method stepper motors with integrated circuits. standards relating to the control and switching low voltage devices were rehearsed. It was compiled schema of an entire unit after designing optimal control section of a stepper motor with integrated circuits, which consists of four parts (power supply, power section for driving an coils of stepper motor, control section and section for driving external devices). Design and realization of PCB are based on compiled schema, PCB was mounted with components and final PCB was recovered. The last part of thesis is about verification a functionality with using measurement of a prototype parameters.