Browsing by Subject "geeli"

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  • Kolmonen, Aino (Helsingin yliopisto, 2019)
    Elintarvikkeiden komponenttien välillä olevat vuorovaikutukset voivat vaikuttaa elintarvikkeiden valmistusprosesseihin, säilyvyyteen ja terveysvaikutuksiin. Tärkkelys ja beetaglukaani molemmat sitovat vettä, ja niiden vaikutus gluteenittoman leivän rakenteen muodostumisessa on olennaista. Gluteenittoman leivän suurin haaste on rakenteen säilyminen paiston jälkeen, mikä aiheuttaa hävikkiä. Vuorovaikutuksien tuntemisen ansiosta prosessit voitaisiin optimoida niin, että gluteenittoman leivän rakenne säilyisi pidempään hyvänä. Kokeellisen työn tavoitteena oli selvittää reologisilla menetelmillä, onko tärkkelyksen ja beetaglukaanin geeliytymisessä eroja, kun näiden muodostamien seosten kuumennusaikaa ja lämpötilaa vaihdeltiin.Vuorovaikutuksia tutkittiin mittaamalla seosten viskositeettia Rapid Visco Analyzerilla (RVA), ja geelien reologiaa mitattiin taajuuspyyhkäisymittauksella. Beetaglukaania sisältävän tärkkelysliuoksen RVA:lla saadun liisteröitymiskäyrän huippuviskositeetti ja loppuviskositeetti olivat korkeampia kuin ilman beetaglukaania valmistetun tärkkelysliuoksen. Beetaglukaania ja tärkkelystä sisältävillä geeleillä oli myös vahvempi rakenne kuin pelkästä tärkkelyksestä valmistetulla geelillä. Beetaglukaanin ja tärkkelyksen liuottaminen yhdessä ei kuitenkaan johtanut vahvemman geelin muodostumiseen, kun liuosta kuumennettiin levyllä noin kahden tunnin ajan. Tutkimuksessa haluttiin tutkia tarkemmin sitä, miten liuotusaika ja -lämpötila vaikuttavat geelirakenteeseen. Kahden tunnin ajan 85 ˚C lämpötilassa liuotetun beetaglukaanin ja gelatinoidun tärkkelyksen sekoituksesta valmistetun geelin ominaisuuksia vertailtiin 15 minuuttia korkeintaan 37 ˚C:ssa liuotetun beetaglukaanin ja liisteröidyn tärkkelyksen sekoituksesta valmistettuun geeliin, ja havaittiin ettei beetaglukaanin parempi liukeneminen johtanut vahvemman geelin muodostumiseen. Tutkimuksen tulokset viittasivat siihen, että laimean beetaglukaaniliuoksen geeliytymisen taustalla on osittainen liukeneminen, mikä on todistettu jo aiemmissa tutkimuksissa. Tutkimuksen tuloksien soveltamisesta gluteenittoman leivän valmistuksessa voitaisiin saada hyötyä, kun rakenne säilyisi hyvänä pidempään prosessien optimoinnin seurauksena.
  • Männistö, Laura (Helsingfors universitet, 2012)
    The literature review focused on the basic structure and characteristics of the cereal starches such as the structure of the starch granule, chemical composition and gelatinization properties. Properties of starches from different botanical sources were compared. The objective of the experimental study was to compare the characteristics of native barley starch to other cereal starches and especially to potato starch. Native commercial barley starch was used as testing material which has uniform size distribution (A). This barley starch was compared to commercial wheat, corn and potato starches. Gelatinization properties were measured by RVA (Rapid Visco Analyzer) in acidity range from 3 to 6. Starch granules were observed by light-microscopy. Viscoelastic properties of starch gels were measured reometrically and texture analyzer was used for surface properties. Synersis as diffused amount of liquid was measured of starch gels. Suitability of barley starch in sponge cakes was also investigated. The effect of pH was significant on gelatinization of starches. The maximum viscosity of cereal starches increased when pH decreased, at the same conditions the viscosity of potato starch decreased. The maximum viscosity of potato starch was nearly ten times higher compared to cereal starches. Native cereal starches formed harder gel and during the storage syneresis was stronger than in the potato starch. The potato starch gel was sticky and bright in color. Sponge cake made of potato starch had the highest level of retrogradation and its volume was small. Potato starch may not be applied to confectionary, because it made the crumb structure dry faster than cereal starches. The sponge cake made of corn or potato starch was firmer in crumb structure. Barley starch was more suitable for sponge cake than corn or potato starch. The size distribution of starch granules seemed to have an impact on stability of cake dough. Barley starch was different in many properties compared to potato starch and those applications differ from each other. Based on this research barley starch is suitable for cake baking.
  • Erämies, Tuijamaija (Helsingfors universitet, 2016)
    A range of different factors affect the composition of a sausage. The main objectives of this thesis were to research and define which factors have an impact on the firmness of the gel in sausages and to develop a method to define the composition of a warm sausage. Anchoring agents and fillers are added into sausages to improve the composition and flavour and to decrease the manufacturing costs. Most of the anchoring agents are proteins, however starch is also used. Starches are very viable anchoring agents. Gelatinised starches absorb or bind water and make it possible to have more water in a sausage. The research was composed of two phases in which the variables were the ingredients of the sausages. The factors that have an impact on the composition of sausages were analysed using statistical tests and variance analysis. In the first phase of the research a method to measure the firmness of a warm sausage was developed. The density of the gel was measured by sensory analysis and by Instron mechanical testing using the research method. The method was based on raising the core temperature of sausages above 49 °C to make the solid collagen soluble. Using a double boiler the core temperatures of the samples were adjusted to the desired level after which the samples were placed in the Instron mechanical tester in a styrox mold to limit the heat conduction. In addition to the mechanical tests a consumer survey to define the optimal eating temperature was included in the development of the research method. The results obtained by using the research method and the results from the sensory test had a correlation. In the future it is possible to skip sensory testing and use only this method to define the composition of a warm sausage. The method was used in the second phase of the research when studying the effects of different ingredients on the firmness of the gel in sausages. The results indicated that the composition of a sausage does undergo changes when heated.