Browsing by Subject "viscosity"
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(2021)Oat β-glucan is well known for its health benefits, which are related to its rheological behavior in the gut. The objective of this thesis was to investigate the extractability and viscosity of β-glucan from oat bread under physiological conditions and to see whether there were varietal differences. Oat flours of twenty different cultivars were used to bake breads which were subjected to in vitro digestion. The resulting extracts were studied for viscosity using a rheometer, and the β-glucan contents of the breads and the extracts were determined to evaluate the extractability. In addition, the effect of flour particle size on extractability was investigated. Variance in the in vitro extractability of β-glucan was seen between cultivars, which was not explained by flour particle size. All samples produced highly viscous extracts, and the viscosities increased sharply with increasing β-glucan concentration, which suggests that the β-glucan was not extensively degraded during the breadmaking process. The viscosities also varied between cultivars, as some exhibited considerably higher viscosities at similar concentrations. The results indicate that the β-glucan from the oat breads would have good capacity to increase viscosity in the intestine, although varietal differences were observed.
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(2022)The 1.64 Ga Ahvenisto complex in the southeastern Finland, is an anorthosite-mangerite-charnokite-granite (AMCG) suite, which has been discovered to host conspicuous magma interaction structures formed in magma mixing and mingling. These structures form areas where the consequences of mingling are found as monzodioritic pillows and granitic veins forming net-veined complexes. Mixing of monzodioritic and hornblende granitic magmas has produced hybrid rocks with intermediate composition. The main goals of the study were to report the major element mineral chemistry of the main minerals (plagioclase, alkali-feldspar, amphibole, and pyroxene) from the hybrid rocks, hornblende granite, and monzodiorite and to test the suitability of geothermobarometric methods for the rock types related to the different magma interaction structures and to evaluate crystallization pressures and temperatures of the pertinent magmas. The magma interaction structures of the Ahvenisto complex are recognized in the mineral chemistry of the mingling and mixing related rocks. The mineral chemistry confirms that the hornblende-granite represents the most primitive granitic phase in the mixing set and the composition of the minerals change as the mixing proceeds towards the final hybrid rock. The mineral chemistry from the monzodiorites reveals that the monzodiorites from different areas of the Ahvenisto complex have distinguished features and they can be separated by their composition. Hornblende-plagioclase thermobarometers and two-pyroxene thermometers were used, and the results were compared to the previous studies related to the emplacement conditions of the Ahvenisto complex. The hornblende-plagioclase thermobarometers suggest that the crystallization of the mixing related rocks took place at ~790–860°C. For the temperature results, pressures of 100 MPa and 300 MPa were used based on earlier studies and a conclusion is drawn that the pressure has had only minor impact on the temperature. The two-pyroxene thermometers show similar regional difference for the crystallization temperatures of the monzodioritic rocks as recognized in the mineral chemistry. The results from the two-pyroxene thermometers show wider variation in the temperatures, which leaves some uncertainty on the liability of the results. The variation is mainly explained by the mineral chemistry of the mafic silicate minerals in the Ahvenisto complex rocks being very iron-rich and outside the calibration standards of the geothermobarometers.
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(2021)Oat β-glucan is a non-starch polysaccharide, and it is well-known that oat β-glucan provides physiological functionalities, such as reducing glycemic response. It is proposed that the reduction of glycemic response is due to the elevation of digesta’s viscosity in the intestinal tract, which is attributed to the viscosity generated by β-glucan. An increase in viscosity of digesta is assumed to hinder starch digestion, thus reducing glucose absorption. However, it is not known whether viscous β-glucan or β-glucan gel causes such physiological responses. Thus, the aim of this Master’s thesis was to study the effects of viscous β-glucan on in vitro starch digestion. The in vitro starch digestibility method was adjusted to suit the viscous β-glucan. The hypothesis was that sample containing oat β-glucan would hinder starch hydrolysis compared to the sample without oat β-glucan. Viscosity and viscoelasticity of wheat starch were analyzed to ensure that the concentration of the wheat starch used was appropriate for the study. The viscosities of oat β-glucan solutions at different concentrations were also measured. The in vitro starch digestibility result was evaluated by measuring the concentration of starch hydrolysis product. Viscosity and viscoelasticity tests of wheat starch showed that 4% wheat starch was suitable in the starch digestibility study. The viscosities of various concentrations of oat β-glucan exhibited pseudoplastic flow behavior. In vitro starch digestibility showed that oat β-glucan slowed down the starch hydrolysis. Calcium contained in oat β-glucan was found to enhance the activity of α-amylase, resulting in a higher concentration of the starch hydrolysis product. 2160 µg/g Ca2+ was added to all samples in order to compensate for different Ca2+ concentrations in each sample. The maximum Ca2+ concentration that 1 U α-amylase could utilize was 98 µg/g Ca2+. The results of this study confirmed that the viscous oat β-glucan hindered the starch digestibility compared to the sample without oat β-glucan and calcium ions played a role in starch digestibility.
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(2014)Thesis literature review deals with composition of cow´s milk, yogurt manufacturing, composition and process attributes affecting textural properties of yogurt and measuring textural properties of yogurt. Plain, stirred yogurts (kg) were manufactured at Valio Riihimäki and Oulu Dairies. The aim of the research was to find out attributes that affect yogurt quality. First milk base composition was determined and, yogurt textural properties were determined (viscosity, graininess, syneresis) using different techniques. Finally yogurt statistical relationships or Pearson correlations and statistical significance between yogurt textural properties and milk base composition and manufacturing process were determined. Additional objective was to determine common specification limits to yogurt textural properties. Statistical analysis; pearson correlation coefficients, p-value and specification limits were carried out using MINITAB®16 statistical software. Good yogurt texture is viscous, free from grains and syneresis. This study showed that yogurt textural properties (viscosity, graininess and syneresis) were affected significantly by yogurt manufacturing plant. There were a lot of fluctuations in yogurt textural properties. Consequently yogurt viscosity fluctuated over 50%, graininess approx. 25% and syneresis approx. 30%. According to this study, yogurts standing a long time before packaging, were less viscose or watery compared to those with shorter standing time prior to packaging. Graininess and evaporating process were found to correlate positively. Yogurts were with more grains when manufacturing process`s evaporating temperature and evaporating rate (l/h) were higher. The higher milk base fat and dry matter content (%) were found to correlate lesser whey separation in yogurt. In addition the higher evaporating rate was in the yogurt manufacturing process, the lesser whey separation was observed. Results from this research are useful for developing dairy processes concerning yogurt manufacturing.
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(2014)The aim of this thesis was to find a suitable substitute of non-animal origin for fat free stirred yoghurt in order to attract new consumers such as vegetarians and people of different religions. The substitutes for gelatin studied here were two food enzymes (transglutaminase and proteinglutaminase), modified potato starch and whey protein. Costs of replacing the gelatin with food enzymes were also examined. Composition of milk, manufacturing process and structure of stirred yoghurt, formation of yoghurt gel and the substitutes for gelatin were reviewed in the literature section. The yoghurts were prepared in the process laboratory of Valio’s R&D using skimmed organic milk and milk powder. During the thesis two trials with food enzymes were also carried out in the production line of Valio’s non-fat yoghurt. Viscosity, pH and graininess of the yoghurts were measured and sensory analyses were conducted during three weeks of storage and the results were compared to handmade control yoghurt and to yoghurt that has been made in the production line in Riihimäki. Enzyme-treated yoghurts were also analyzed with gel electrophoresis. According to this study the best substitutes for gelatin were TG and PG enzymes and whey protein concentrate. Yoghurts prepared with these substitutes had a structure and flavor comparable with that of the control yoghurt. Their viscosities were even greater than the viscosity of Riihimäki’s yoghurt. No graininess or syneresis was observed in these yoghurts. However, the yoghurts manufactured in the production line were found to be grainy and also some syneresis was observed. The graininess could be reduced by treating the yoghurts with Ytron-Z-mixer. The resulting yoghurts did not differ from the current non-fat yoghurt in viscosity or in sensory properties. We also found out that it was possible to reduce the amount of protein content in the yoghurts without affecting the structure of the yoghurt. The reduction of protein content and substitution of gelatin with food enzymes did not cause any extra costs.
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(2007)The literature review deals with the composition of rye flour and the significance of en-zymes and sourdough in rye flour processing. The operational principles of twin screw extruders, the extrusion of grain based materials and the formation of aroma during grain based extrusion are also reviewed. The aim of this study was to determine the influence of the amount of powered rye sourdough and extrusion cooking parameters on the structure and properties of rye extrudate. Three process parameters were varied: content of rye sourdough powder, process temperature during the final stages of extrusion and revolution speed of the extruder's screws. A Box-Behnken's experimental design was used with 3 levels of dried sourdough powder content (0, 20 and 40%), 3 screws revolution speeds (200, 350 and 500 rpm) and 3 exit temperatures (120, 150 and 180°C). Feed rate was set at 4.0 kg/h and the moisture of the feed was 17.4%. A total of 15 experiments were perfomed. Pasting properties, acidity, acid value and D- and L-lactic acid concentration of full grain rye flour, dried rye sourdough flour and ground extrudate powder were determined. Acetic acid concentration of dried rye sourdough powder was also determined. Moisture content, expansion, texture, bubble sizes and colour of extrudate were determined. Extrusion cooking produce very different types of rye extrudates and the effect of process parameters on structure of extrudate was significant. When the pressure at the die was 30–40 bar, structure of extrudates were porous. Freeze dried extrudates were harder than extru-dates stored for one day at room temperature. Young's modulus decreased with increasing screws speed and processing temperature. Extrudate’s expansion increased as a function of increased revolution speed of screws and decreased processing temperature. As the content of dried sourdough increased, the bubble sizes of extrudate increased and also yellow (a) and red (b) colour and acidity of extrudates became stronger. Lightness (L) was statistical significantly higher when temperature was higher. As expected, the concentration of D- and L-lactic acid increased with increasing dried sourdough content. Decreased content of dried rye sourdough and slower revolution speed of screws increased cold peak viscosity signifi-cant. Peak and hold viscosities increased with slower revolution speed of the screws and decreased content of dried sourdough. Final viscosity and setback value increased signifi-cantly with slower revolution speed of the screws. The optimal extrudate, which was crispy and had a good flavour, was obtained when the content of dried sourdough powder was 20%, revolution speed of the screws was 500 rpm and processing temperature was 120°C.
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(2016)In the literature review of this study, the focus was on biofilms that certain microbes produce, and their potential use in food industry. Biofilms consist of microbial cells and extracellular products, e.g., polysaccharides. Pullulan as an exopolysaccharide has many industrial applications and the aim of this study was to explore a new potential alpha-glucan, dextran, and especially its ability to form a stand-alone film. Pullulan and dextran were separately mixed in de-ionized water. The dynamic viscosities of dextran and pullulan solutions were determined. Film formation of dextran was not successful, not even with sorbitol as a plasticizer. The optical properties, water vapor and oxygen permeabilities and tensile strengths of pullulan films were studied. Additionally, Whatman42-filter material was coated with or immersed in dextran solution. Hence the changes in tensile strength and permeability values between a well-known material and dextran treated material could be detected. Pullulan films had low haze values (2.1–3.9%) and they were transparent to UVA-, UVB- and visible light. The tensile strength values of pullulan films were 47–53 MPa. For filter paper, the corresponding values were 10 MPa and application of dextran coating increased it to 15–19 MPa. All polysaccharide solutions exhibited Newtonian behavior and their relative viscosities were <10 mPa, 5% pullulan with viscosity around 20 mPa as an exception. Pullulan solutions had higher viscosities than dextran solutions. The air permeabilities were 10–50 ml/min for pullulan films, 10 ml/min for dextran-sorbitol film, 200 ml/min for dextran film and 200–500 ml/min for Whatman42 material. The oxygen permeability values for pullulan films were <0,1 cm3·μm m-2·d-1·kPa-1. Based on results in this study, pullulan films are impermeable to oxygen. As the films tolerated water vapor poorly, pullulan might be a potential component in packages made of composite materials, as individual packaging material in dry environment or possibly chemically modified to obtain better resistance to water vapor. Our results show that without additional modifications dextran does not form a continuous self-supporting films in these conditions.
Now showing items 1-8 of 8