Browsing by Subject "sugar"

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  • Lamichane, Nicole (Helsingin yliopisto, 2019)
    Over the past years sugar consumption has seen great increases worldwide, together with a rise in the prevalence of metabolic diseases. There is a growing need for a comprehensive characterisation of the genes involved in sugar metabolism, yet the mechanisms by which cells sense and respond to sugars in vivo have remained incompletely understood. Here, I analyse members of a protein family best known for their regulation of differentiation during development with regards to their role in sugar metabolism. The Hairy and Enhancer of Split (HES) protein family are a group of basic helix-loop-helix (bHLH) transcription factors that function as major downstream effectors of the Notch signalling pathway. In mammals, the HES proteins have mostly been studied for their role in cell differentiation, but HES1 has been implicated in metabolic control. Drosophila has several transcription factors belonging to the HES family, including Hairy and seven bHLH transcription factors located in the Enhancer of split complex (E(spl)-C). The E(spl)-C bHLH transcription factors display high homology and are considered to be genetically redundant, and therefore little is known about their individual functions. The other HES family members in Drosophila have not previously been linked to metabolic regulation, but Hairy has been shown to repress the tricarboxylic acid cycle. In light of the findings implicating HES1 and Hairy in the regulation of metabolism, I systematically investigated the role of the HES transcription factors in sugar metabolism. By using the GAL4/UAS system in Drosophila melanogaster, I knocked down gene expression of each of the family members, and raised the flies on diets varying in sugar content to identify possible sugar intolerance phenotypes. Here, I show that knockdown of one of the E(spl)-C bHLH genes led to severe sugar intolerance that affected both survival and organismal growth, but did not alter the levels of circulating carbohydrates and storage lipids as measured with colorimetric assays and lipid staining. Furthermore, I identify the tissues in which this transcription factor functions to provide sugar tolerance. Using analysis of publically available chromatin-immunoprecipitation sequencing data coupled with quantitative RT-PCR, I uncover mTOR target Thor/4E-BP as a putative target gene. Additionally, I show that Hairy is similarly required for complete sugar tolerance, but that the mechanism differs from the E(spl)-C bHLH transcription factor. Hairy binds to and positively regulates expression of genes involved in glycolysis and the pentose phosphate pathway, suggestive of a cooperation with earlier known regulators of sugar sensing. In conclusion, I have shown that only two HES family members are involved in the regulation of sugar metabolism and that their regulatory mechanisms are distinct, implying that the HES family members have more diverse roles than previously assumed.
  • Liukkonen, Tanja (Helsingfors universitet, 2015)
    Gelatin-based confections are one type of gummy confections. Their main ingredients are water, sucrose, glucose syrup and gelatin, which causes gel-like texture. The literature review focused on the raw materials, the manufacturing process and the properties of gelatin- and starch-based gummy confections. The aim of this study was to find out how invert sugar, when it replaces sucrose and glucose syrup, affects structural properties and short-term shelf life of gelatin-based confections. In addition, changes in the sensory quality were observed. In the experimental research, the gelatin-based confections were manufactured on a laboratory scale according to simplex-centroid mixture design, where the total sugar content was constant, but sucrose, glucose syrup and invert sugar mass fractions were varied. Measurements for the samples were rheological properties, sugar content and dry matter content of confection paste and mechanical properties (hardness, stickiness and relaxation parameters), dry matter content, water activity and water sorption of confections. In addition, a few samples were manufactured with coloring and flavoring agents for sensory observation. The results were analyzed with the PLSR (Partial Least Squares Regression). Finnsugar Ltd.'s product development department offered the topic of this study and raw materials, but all the experiments were carried out in the Department of Food and Environmental Sciences in the University of Helsinki. The PLSR model contained five components, and the coefficient of determination R2 was 74.1%, the adjusted R2 was 63.3% and the coefficient of prediction Q2 was 43.6%. The model determined all response variables well, but predicted some of them poorly. Almost all response variables regression models were statistically significant at 5% significance level, but some of the models were incomplete (plof<0.05). The variables important in projection (VIP) in the PLSR model were mass fraction of invert sugar, mass fraction of glucose syrup and their interactions with mass fraction of sucrose. The PLSR model was best for rheological properties of confection pastes and mechanical properties of confections, and poorest for water activity and dry matter content of confections. Even at low mass fraction of invert sugar viscosity of confection paste decreased. Invert sugar also reduced hardness of confections, and speeded up their structures recovery after compression. Sensory observation shows the positive effects of invert sugar, such as softness of structure and stronger taste. The present study showed that the sugars have interactions, which also affect properties of the gelatin-based confections, and invert sugar content alone is not the significant factor. Based on the results of this study it seems that invert sugar affected stronger most of the response variables if it replaced relatively more glucose syrup than sucrose.
  • Toivola, Johanna Maria (Helsingfors universitet, 2015)
    The purpose of this study was to investigate the structure of ice cream, especially the effects of temperature, sugar composition and stabilizer-emulsifier concentration on the melt down, hardness and moulding properties of ice cream. The aim was to produce a soft and easily mouldable ice cream that suits the intended purpose. A sensory evaluation was conducted to the ice creams with desired structural properties. The literature review deals with ice cream ingredients, manufacturing process and factors affecting ice cream structure. For the experimental study, 16 ice creams with different compositions were made. The ice creams contained 12 or 6 % fat, different types of sugar compositions (A, B, C, D, E, F) and different concentrations of two types of stabilizer and emulsifier blends (A, B). Ice creams were stored at different temperatures. The hardness of ice cream was measured with a Texture Analyser, the melting rate was determined and the moulding properties were analysed with a moulding test. The two ice creams with desired structure were compared to a commercial ice cream in a sensory evaluation. The results of the hardness measurements revealed, that temperature and sugar composition affected hardness the most. Stabilizer and emulsifier concentration and type did not have an effect. The softest ice creams were those stored at higher temperatures and those made with sugar composition C, D, E and F. The slowest melting ice creams were the ones containing greater amounts of stabilizers and emulsifiers. The ice cream made with sugar composition D melted the fastest. For the moulding test, the softer ice creams were the easiest to mould. The ice cream made with sugar composition D was found to be too soft, almost runny, and the ones made with sugar composition A and B were found to be too hard. The ice creams made with sugar composition C, E and F were found pleasing. The batches containing a greater amount of stabilizer and emulsifier were found to be a bit gummy. In the sensory evaluation there were only one difference in sweetness found between the study ice creams and the commercial one. There were no differences found in creaminess and over all liking. From this can be concluded that the study ice creams are accepted by the consumers as well.
  • Pinomaa, Anni (Helsingfors universitet, 2016)
    Protected cultivation of raspberries (Rubus idaeus L.) has increased its popularity in Finland. One reason is that the fruit is extremely sensitive to rainy weather during its development. The raspberry plant itself is sensitive to wind and low temperatures, which can reduce growth. In Europe most of the raspberry is grown in protected cultivation, and this technology is now becoming popular in Finland. A high tunnel is a cost-efficient way to protect the plants against rainy weather and extend the harvest season. The protected cultivation has been shown to increase the yield and cropping potential of raspberry and reduce the gray mold in the berries. In human diet, berries are among the richest sources of antioxidants. In raspberry, the most important antioxidants are vitamin C (20 %) and phenolic compounds (80 %). Among phenolic compounds, ellagitannins and anthocyanins give the greatest contribution to antioxidant activity. The aim of this thesis was to study the yield, sensory quality, nutritional quality and shelf life of three floricane fruiting raspberry cultivars grown in high tunnel and open field. Cultivars ’Glen Ample, ’Glen Dee’ and ’Maurin Makea’ were used in the study. Sugar and acid content of raspberry were examined to get an overview of sensory quality. The nutritional quality was studied with an antioxidant activity assay (using FRAP method) and total phenolics assay (using Fast Blue BB method). The shelf life was tested both in +5 °C and in room temperature. The average total yield per cane was 99 % greater in tunnel than in the open field, whereas both sugar and acid content of the berry were greater in open field. Berry weight and total phenolics content were strongly cultivar dependent characteristics. The results of the antioxidant activity assay did not show significant differences between either growing conditions or the cultivars. The shelf life in room temperature was equally weak for all samples, but in +5 °C storage the open field raspberries developed symptoms of gray mold earlier than those picked from the tunnel. The conclusion is that contents of health beneficial compounds in berries were not affected in tunnel cultivation, but berry taste may be affected, as differences in sugar and acid contents were observed.