The technology of modern fermented milk production is not complicated and relies largely on the characteristics of the microorganisms used in its manufacture. Biochemical substances excreted by the starter cultures contribute to the chemical, physical and organoleptic properties of cultured milks. Chemical and organoleptic properties of yoghurt starter cultures have been widely studied over several decades. Conversely the biosynthetic processes and genetic control of the production of viscous extracellular material (slime) by selected thermophillic streptococci is still insufficiently understood. This study attempted to elucidate physiological aspects and the genetic control of slime production. An attempt to chemically induce ropiness was also preformed. Twenty strains of Gram positive, thermo-tolerant, milk dotting, catalase negative cocci were collected from a variety of sources. All strains were identified as Streptococcus thermophilus. Four of the isolates were identified as capable of producing an extracellular, ‘ropy’ capsular material. A negative staining method for highlighting capsular material under light microscopy was described. Ropy isolates displayed thick capsular zones of between 6-8 μm. The isolates graded as non-ropy produced only small capsular zones (less than 2 μm); two variants displayed no capsular material. Instability of the ropy phenotype during subculture and prolonged storage was described for all four ropy isolates at varied temperatures. Instability during transfer was reported as moderate with a loss of no more than 45% of ropy colonies after 15 subcultures at 48°C A significant increase in instability, during transfer, associated with an increase in incubation temperature (37-48°C) was also reported. Prolonged storage of ropy variants over ten days resulted in a drop in the number of ropy colonies. The loss was minimal when cultures were stored at 8°C, but excessive (approaching 100%) at 37°C This suggested the presence of capsular degradative substances. Analysis of the plasmid profiles of 20 strains identified only two strains harboured plasmid DNA. All plasmids were small, less than 23kilobases, and each strain possessed a single plasmid species. Only one ropy strain contained plasmid DNA that was shown, with the aid of curing experiments, not to be linked to production of the ropy phenotype. The amino acid analogue p-fluoro-DL-phenylalanine was unsuccessful in generating ropy colonies from non-ropy variants of Streptococcus thermophilus at low concentrations. Some technological considerations for the use of ropy variants of Streptococcus thermophilus in yoghurt starter cultures were made.

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Probiotic bacteria are added to commercial yoghurts as adjunct cultures, to impart health benefits to consumers. To gain maximum therapeutic benefit, the bacteria must remain viable over the shelf life of the yoghurt. Studies have shown, however, that the viability of these bacteria decreases significantly over this period and in some products, is negligible prior to the expiry date. Some strains of probiotic bacteria are oxygen sensitive. Yoghurt has been found to contain a significant concentration of dissolved oxygen and it has been proposed that this has a negative effect on probiotic viability. In this research, several tests were conducted and observations made. Experiments were conducted with non-commercial probiotic cultures to observe the effect of low oxygen environment on probiotic viability. No significant difference existed in viability between probiotic bacteria stored in oxygen reduced yoghurt and regular yoghurt. All yoghurt stored in oxygen barrier packaging material displayed enhanced shelf-life properties, this was observed in replicated experiments. Oxygen barrier packaging combined with an oxygen scavenging material was found to be the most effective oxygen removal system, particularly when used with set type yoghurt. / Doctor of Philosophy (PhD)

<p>This degree project was performed by Marina Hultin and Lina Larsson and it is our final project in the Innovation- and design engineer programme at Karlstad University. The project was carried out during the spring semester 2007. The project comprises 20 weeks of work and 5 of these were reserved for a study of literature. Our project was assigned by Designstudio Värmland and our instructor and examiner was Lennart Wihk.</p><p>Each year 50 kg of food is thrown away per person. One of the reasons for this is that a lot of the food remains in the container. We produce more food than there is a need for because of all the food that goes to waste. This also contributes to an emission of carbon dioxide of a half million tons. As assigned by Designstudio Värmland we took a closer look at the food packaging of today. The base for this project is a research project, which has been carried out at Karlstad University. The purpose was to show that if it is possible to get the most out of the food container, it is justified to use more packaging material. The packaging shall be optimized, not minimized!</p><p>The purpose of the project is to examine some packings on the market that contributes to the food waste. If the food packaging is optimized, the waste of food can be reduced and at the same time the consumers will be more satisfied and also get more value for their money.</p><p>Our aim was to develop three concepts of optimized packings that will reduce the food wastage. Graphic design for each and every packing is included. The work method that was used is called the design procedure.</p><p>When the brainstorming was completed we decided to only include packaging for yoghurt. This decision was made because today’s yoghurt containers are difficult to empty.</p><p>The project resulted in three concepts of new yoghurt containers. Prototypes were made both in CAD and as visuals. Graphic design was also made for each concept.</p> / <p>Detta examensarbete har utförts av Marina Hultin och Lina Larsson under vårterminen 2007 och är en avslutning på Innovations- och designingenjörsprogrammet på Karlstads universitet. Arbetet omfattar 20 poäng, varav 5 poäng består av en fördjupad litteraturstudie. Uppdragsgivare var Designstudio Värmland och handledare för examensarbetet var Lennart Wihk.</p><p>Varje år slänger vi 50 kg livsmedel per person. Detta beror till stor del på att det finns livsmedel kvar i förpackningen. Eftersom vi slänger livsmedel så innebär det att mer mat produceras än det finns behov för. Den mat vi slänger bidrar till ett koldioxidutsläpp på en halv miljon ton per år. På uppdrag av Designstudio Värmland tittade vi närmare på dagens förpackningar för livsmedel. Detta arbete grundar sig i en forskningsstudie som bedrivits på Karlstads universitet. Studien visar att om det går att få ut lite mer av livsmedlet ur dess förpackning så är det befogat att använda mer förpackningsmaterial. Förpackningen ska optimeras, inte nödvändigtvis minimeras.</p><p>Syftet med projektet är att undersöka några olika förpackningar på marknaden som bidrar till slöseriet av livsmedel. Genom att optimera förpackningen kan livsmedelspillet minskas och konsumenterna blir nöjdare och får även mer valuta för pengarna.</p><p>Målet som sattes upp var att ta fram tre koncept på optimerade förpackningar, med tillhörande grafisk design, som minskar livsmedelspillet. Arbetet utfördes enligt designprocessen.</p><p>Efter idégenereringen beslutade vi att avgränsa oss till yoghurtförpackningar, då dagens förpackningar för yoghurt är svåra att tömma.</p><p>Resultatet blev tre koncept på nya yoghurtförpackningar. CAD-modeller och prototyper togs fram på alla olika koncept. Till varje koncept gjordes även en grafisk utformning.</p>

This degree project was performed by Marina Hultin and Lina Larsson and it is our final project in the Innovation- and design engineer programme at Karlstad University. The project was carried out during the spring semester 2007. The project comprises 20 weeks of work and 5 of these were reserved for a study of literature. Our project was assigned by Designstudio Värmland and our instructor and examiner was Lennart Wihk. Each year 50 kg of food is thrown away per person. One of the reasons for this is that a lot of the food remains in the container. We produce more food than there is a need for because of all the food that goes to waste. This also contributes to an emission of carbon dioxide of a half million tons. As assigned by Designstudio Värmland we took a closer look at the food packaging of today. The base for this project is a research project, which has been carried out at Karlstad University. The purpose was to show that if it is possible to get the most out of the food container, it is justified to use more packaging material. The packaging shall be optimized, not minimized! The purpose of the project is to examine some packings on the market that contributes to the food waste. If the food packaging is optimized, the waste of food can be reduced and at the same time the consumers will be more satisfied and also get more value for their money. Our aim was to develop three concepts of optimized packings that will reduce the food wastage. Graphic design for each and every packing is included. The work method that was used is called the design procedure. When the brainstorming was completed we decided to only include packaging for yoghurt. This decision was made because today’s yoghurt containers are difficult to empty. The project resulted in three concepts of new yoghurt containers. Prototypes were made both in CAD and as visuals. Graphic design was also made for each concept. / Detta examensarbete har utförts av Marina Hultin och Lina Larsson under vårterminen 2007 och är en avslutning på Innovations- och designingenjörsprogrammet på Karlstads universitet. Arbetet omfattar 20 poäng, varav 5 poäng består av en fördjupad litteraturstudie. Uppdragsgivare var Designstudio Värmland och handledare för examensarbetet var Lennart Wihk. Varje år slänger vi 50 kg livsmedel per person. Detta beror till stor del på att det finns livsmedel kvar i förpackningen. Eftersom vi slänger livsmedel så innebär det att mer mat produceras än det finns behov för. Den mat vi slänger bidrar till ett koldioxidutsläpp på en halv miljon ton per år. På uppdrag av Designstudio Värmland tittade vi närmare på dagens förpackningar för livsmedel. Detta arbete grundar sig i en forskningsstudie som bedrivits på Karlstads universitet. Studien visar att om det går att få ut lite mer av livsmedlet ur dess förpackning så är det befogat att använda mer förpackningsmaterial. Förpackningen ska optimeras, inte nödvändigtvis minimeras. Syftet med projektet är att undersöka några olika förpackningar på marknaden som bidrar till slöseriet av livsmedel. Genom att optimera förpackningen kan livsmedelspillet minskas och konsumenterna blir nöjdare och får även mer valuta för pengarna. Målet som sattes upp var att ta fram tre koncept på optimerade förpackningar, med tillhörande grafisk design, som minskar livsmedelspillet. Arbetet utfördes enligt designprocessen. Efter idégenereringen beslutade vi att avgränsa oss till yoghurtförpackningar, då dagens förpackningar för yoghurt är svåra att tömma. Resultatet blev tre koncept på nya yoghurtförpackningar. CAD-modeller och prototyper togs fram på alla olika koncept. Till varje koncept gjordes även en grafisk utformning.

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Darbo tikslas – įvertinti jogurtų sudedamąsias dalis, mitybinę vertę ir vartotojų nuomonę apie jogurtus. Darbo uždaviniai: 1. Remiantis moksline literatūra, aptarti jogurto savybes, gaminimo metodikas, įvairovę; 2. Įvertinti apklaustųjų nuomonę pasirenkant pirkti ir vartoti jogurto produktus; 3. Atlikti jogurto sudedamųjų dalių analizę, pagal pakuočių ženklinime pateiktą informaciją; 4. Atlikti laktozės laboratorinius tyrimus atrinktuose jogurto pavyzdžiuose; 5. Parengti jogurtų vartojimo rekomendacijas. Darbo metodai – mokslinės literatūros analizė, kokybinis (jogurto sudėtis) ir kiekybiniai (anketinė apklausa, laktozės laboratorinis tyrimas) tyrimai, statistinė tyrimo rezultatų analizė. Siekiant įvertinti jogurtų sudedamąsias dalis, jų mitybinę vertę, bei apklaustųjų nuomonę pasirenkant pikti ir vartoti jogurtą, tyrimui buvo parinkti šie tyrimo instrumentai: vartotojų apklausos klausimynas (anketa), jogurtų pakuočių ženklinimo etiketės; jogurtų laboratorinių tyrimų protokolas. / The aim of the research – to evaluate the ingredients, the nutritive value of yoghurts and consumers‘opinion on yoghurts. Research tasks: 1. To discuss the characteristics of yoghurt in accordance with the scientific literature, its production techniques and its diversity; 2. To evaluate the opinion of respondents which determine their choice when buying and consuming yoghurt products; 3. To conduct the yoghurt ingredients’ analysis according to the package labelling information; 4. To perform lactose laboratory tests of selected samples of yoghurt; 5. To prepare yoghurt consumption recommendations. Methods of the Work – scientific literature analysis, qualitative (yoghurt composition) and quantitative (questionnaire, lactose laboratory test) research, statistical analysis of the survey results. In order to evaluate the yoghurt’s ingredients, its nutritional value and the respondents’ preferences of buying and consuming yoghurt the following tools for the conduction of research have been chosen: consumer survey questionnaire; yoghurt packaging labelling marking; the protocol of yoghurts’ laboratory testing.

Magistrantūros studijų baigiamajame darbe pateikiami jogurto, praturtinto liofilizuotomis daržovėmis, fizikinių rodiklių (klampumo, rišlumo, konsistencijos, tvirtumo ir rūgštingumo) bei juslinių savybių tyrimų rezultatai. Darbo objektas – 3,5 % riebumo ekologiškas jogurtas, kuris buvo pagardintas liofilizuotomis daržovėmis, prieskoniniais augalais ir pievagrybiais. Buvo paruošti 6 jogurto su priedais variantai: I var. (kontrolinis) – be priedų; II var. – pomidorų, žaliųjų bazilikų milteliai, druska; III var. – pomidorų, žaliųjų bazilikų, svogūnų milteliai, druska; IV var. – pomidorų, svogūnų milteliai, druska; V var. – paprikų, dašio milteliai, druska; VI var. – pievagrybių, svogūnų milteliai, druska. Darbo metodai: jogurtų spalva matuota spalvos analizatoriumi ColorFlex 45˚/0˚ (HunterLab, JAV). Šviesos atspindžio režimu matuoti parametrai: L*, a* ir b*. Jogurto tekstūra įvertinta tekstūros analizatoriumi TA.XT plus (Stable Micro Systems, JK). Tyrimo metu naudotas atgalinio išspaudimo 35 mm diskas bei 50 mm skersmens stiklinaitė. Nustatyti tyrimo parametrai: disko judėjimo greitis prieš bandymą – 1,0 mm s-1, greitis bandymo metu – 1,0 mm s-1, greitis po bandymo – 10,0 mm s-1. Jogurto juslinėms savybėms įvertinti naudotas aprašomasis juslinės analizės metodas. Buvo nustatyti tokie jusliniai rodikliai: skonis, kvapas, konsistencija, išvaizda ir spalva. Jie įvertinti naudojant intervalines 5 balų skales. Juslines jogurto savybes vertino 6 vertintojai, kurie turėjo užpildyti... [toliau žr. visą tekstą] / Master‘s thesis presents physical properties (viscosity, firmness, consistency, cohesiveness and acidity) and sensory analysis results of yoghurt with lyophilised vegetables. Object of the research: 3.5 % fat yoghurt enriched with lyophilised vegetables, herbs and mushrooms. Six samples of yoghurt were produced. (1) variant (control) was natural yoghurt without any vegetables; (2) variant was made by adding tomatoes, green basil powder, salt; (3) variant of yoghurt contained tomatoes, green basil, onions powder and salt; (4) variant was enriched with tomatoes, onion powder, salt; (5) test variant was made with red peppers, summer savoury powder, salt; (6) variant was yoghurt enriched with mushrooms, onion powder and salt. Research methods: Visual colour of yoghurts was measured by using a Hunter Lab Colour Measurement System Model Color Flex. 45/0 (Hunter Associates Laboratory, Inc.,USA) on the L*a*b* scale. A TA.XT Plus Texture Analyser (Stable Micro Systems Ltd., England) was used to analyse the textural properties of yoghurt samples through simple compression test, using back extrusion 35 mm cell disk and 50 mm back extrusion container. TA settings: Pre – Test speed: 1.00 mm/s, Test speed: 1.00 mm/s, Post – Test speed: 10 mm/s. The descriptive sensory analysis method was applied to assess the following sensory properties of yoghurt: taste, odour, consistency, appearance and colour. The sensory properties were analysed by six tasters who were asked to fill in the... [to full text]