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Porovnání senzorických vlastností džemů slazených steviol-glykosidy a dalšími sladidly
KÜFFNEROVÁ, Nela
The aim of the diploma thesis was evaluation of sensoric attributes of blueberry and current jams sweetened by selected Steviol glycosides and their comparing with other sweeteners. For evaluation of sensoric attributes were used rebaudioside A, stevioside, aspartame, erythritol and sugar beet. Stevia rebaudiana var. Bertoni is a persistent plant, which contains sweetening Steviol glycosides, which have a use in food processing. They are available in the area of EU indicated as E960 since 2011. The most used Steviol glycosides are stevioside and rebaudioside A, which are demarcated with a high sweetness, which could be 200-400 times higher than saccharose. The usage of sweeteners is legislatively allowed, which means it is also allowed to do sensoric analyse and detect perception of added substances in food. These analyses evaluate food with the help of sense - perception. Methodical part of the work contains procedure, used methods for gaining evaluation of data from a sensoric analyse after the degustation of jams, which has taken place with the presence of ten judges - an academic students in the working compartment of University of South Bohemia. Respondents entered their evaluation into protocols, which were prepared in advance. The results of diploma thesis are evaluated by the method of Kramer, which is used for this kind of analyse. The critical scale between 20 and 40 with the value of probability P = 95% was defined according to this method. Evaluation is described with the help of graphs and tables, added with a wordily describtion. Conclusion of analyse of diploma thesis is, that the usage of Steviol glycosides is not most suitable way of sweetening jams. Acceptable valuations of jams containing Steviol glycosides were proven in parameters of colour and aroma. The reasons for less successful evaluation of Steviol glycosides could be due to bad pH of food or badly chosen dosing, without combination of other kinds of sweeteners. The best sensory characteristics traditionally showed sugar beet and aspartame followed by rebaudioside A and stevioside, which were placed on the third and forth place from five used sweeteners. The part of the diploma thesis was an evaluation of questionnaire, where the result was, that asked people preferred fruit ingredient of jams (type of fruit, amount) not their way of sweetening while choosing a jam.
Využití stévie sladké (Stevia rebaudiana, Bertoni) ve výživě člověka
KÜFFNEROVÁ, Nela
The Bachelor's thesis is focused on the use of Stevia rebaudiana (Stevia rebaudiana var. Bertoni) in human nutrition as an alternative sweetener with many positive side effects. Stevia rebaudiana var. Bertoni, also known as honey leaves or Stevia sugar, belongs to the star family (Asteraceae). Its area of origin is the territory of Paraguay in South America and it was first described in 1887 by botanist, Moises Santiago Bertoni. Stevia belongs to the perennial plant group; it grows to one meter in height, the leaves are dark green, densely dotted with fine hairs. The flowers are whitish. The roots grow just under the soil surface, due to the shallow root system. The overall plant appearance depends mainly on the space for growth and nutrient content in the soil. When planting, it is necessary to observe the sowing periods, which range between February and March. It is also important to maintain a constant temperature during germination, which should not drop below 10°C. The Asteraceae family includes 154 species of Stevia. Stevia rebaudiana var. Bertoni is the only one to be characterised by a sweet taste and is therefore the subject of research in the field of nutrition and food. The diterpene sterol glycosides present in it are responsible for its sweetness. The greatest proportion up to 95 % of sterol glycosides is composed of Steviosides and Rebaudiosides A, B, C, D, E, F. Current society is searching for new, alternative methods of sugar replenishment, characterised by a high energy value. The excessive consumption of beet sugar is one of the causes of the high increase of lifestyle diseases, such as diabetes or obesity. The possibility of using the malted potential of Stevia appears to be a suitable alternative. Many studies have been carried out to date. They have investigated the effect of Stevia on human health and its safety for food industry usage. Studies' conclusions demonstrate very good effects of Stevia extracts in the treatment or prevention of certain diseases. For people suffering from Type II Diabetes, the use of Stevia as a sweetener is totally safe, without any negative side effects. Due to the zero energy value, it is suitable for people suffering from obesity, when it is necessary to reduce the caloric intake of food. Investigations have been were carried out in connection with the possible carcinogenicity, mutagenicity, dental caries or potential impact on the fertility. Stevia extracts have been authorised in the EU since 2010, when the European Food Safety Authority (EFSA) issued an opinion on the safety of sterol glycosides, extracted from the plant of Stevia rebaudiana var. Bertoni. The daily acceptable dose of 4 mg/kg body weight was also determined.

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