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Study of the presence of phenolic substances and their antioxidant activity in food products containing rosehip (Rosa canina L.)
Hronová, Vendula ; Mikulíková, Renata (referee) ; Kovalčík, Adriána (advisor)
This bachelor's thesis monitored the content of bioactive substances and antioxidant activity in the jams made of the fruit of rose hips (Rosa canina L.). The jams were sweetened with various sweeteners such as cane sugar, beet sugar, erythritol and stevia. Moreover, the rheological properties of jams were determined. The properties of home-made jams prepared from rosehip fruit were compared with the commercial jam. Another aim was to determine whether the by-products received after the production of jams could serve as beneficial sources of bioactive substances after the preparation of water extracts. The content of carbohydrates, polyphenols, flavonoids, and antioxidant activity were determined in jams and extracts spectrophotometrically. Next, the spectrophotometric detection of pectin, the chemical characterization of jams by infrared spectrometry, and the spectrophotometric determination of the jam colour were performed. The concentration of bioactive substances in jams was influenced by the geographical location and the time and weather conditions of harvest. The rheological properties and pectin content of the jams depended on the type of the used sweetener. The assessment of the water extracts prepared from the by-products after jam production and from the dried fruits of rosehip showed the high content of bioactive substances and high antioxidant activity in all tested extracts. The presented work points out that it is possible to prepare jams with superfood properties from the fruit of rose hips and extracts with high antioxidant activity.
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Sensory evaluation of model non-chocolate sweets
Malyszová, Markéta ; Mikulíková, Renata (referee) ; Vítová, Eva (advisor)
The aim of this bachelor's thesis was to implement a sensory analysis of model non-chocolate sweets of a selected type – specifically gummy jellies. The theoretical part deals with the characteristics of non-chocolate confectionery, information about their composition and properties and technological processes of production. Principle of sensory evaluation, including selected methods of this analysis are mentioned, too. The experimental part focuses on sensory evaluation of prepared gummy jellies. Several samples were made, which contained the addition of herbal extract, namely chokeberry and echinacea. The samples were evaluated using a scale based on their colour, aroma, and flavour. Furthermore, a profile test of tastes was applied, and their overall acceptability was evaluated. Untrained assessors, students from Faculty of Chemistry BUT, performed the sensory evaluations. The aim was to assess the influence of these herbal extracts on the sensory quality of the sample. The pleasant colour and taste influenced the positive evaluation the most. On the other hand, the faint aroma and bitter taste contributed to the negative evaluation.
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Determination of the effect of dog rose (Rosa canina L.) on the oxidative stability in fresh juices
Borová, Šárka ; Mikulíková, Renata (referee) ; Kovalčík, Adriána (advisor)
This bachelor thesis aimed to determine the content of bioactive substances and antioxidant activity in ethanolic extracts of rose hips fruits (Rosa Canina L.). This work verified the possibility of using the rosehip ethanolic extract as an antioxidant to inhibit the oxidation of fresh pear juice. The ethanolic extracts were prepared by extracting rose hips fruits in various ratios of fruits to the volume of 40% ethanol for 7-28 days. After determining the total content of carbohydrates, polyphenols, flavonoids and vitamin C, it was found that, in principle, the range of the defined substances increases with the ratio of rosehip fruit to the volume of ethanol solution as well as with the extraction time. Ethanol rosehip extracts have also been shown to possess significant-high antioxidant activity. The stabilizing effect of rosehip fruit extract against the oxidation of fresh pear juice was determined spectrophotometrically. It was found that rosehip fruit extracts could inhibit the oxidation of fresh pear juice and have the potential as a natural stabilizer of fresh fruit juices.
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Analysis of onion and garlic samples of different geographical origin
Korček, Jakub ; Mikulíková, Renata (referee) ; Diviš, Pavel (advisor)
Presented master thesis dealt with the analysis of garlic and onion samples and tried to find correlations between chemical composition and country of origin. The parameters examined were dry content, crude protein content, concentration of phenolic compunds, carbohydrate content (fructose, glucose), alliin content and concentration of selected elements (P, Mg, Ca, Na, K, Fe, Zn). Average content of dry matter of fresh samples was 35,84 ±2,12 g/100 g and of dehydrated samples was 90,61 ±2,90 g/100 g. Concentration of phenolic compounds was measured spectrophotometrically with Folin-Ciocault reagent. Average phenolic compounds content of samples was 0,1840 ±0,1286 GAE g/100 g. Crude protein content was measured by Kjeldahl method, and calculated from total nitrogen content. Carbohydrates were measured by HPLC-ELSD after hydrolysis of fructans. Average content of fructose of garlic samples was 57,014 ±0,863 g/100 g, of onion samples was 33,718 ±1,168 g/100 g. Average content of glucose of onion samples was 22,633 ±0,405 g/100 g. Alliin content was measured by HPLC-DAD method. Average alliin content of fresh samples was 4,644 ±0,446 g/100 g and of dehydrated samples was 1,962 ±0,180 g/100 g. Elemental analysis was conducted by ICP-OES method. Average concentration of selected elements was: P 2,15 ±0,11 mg/g, Mg 0,638 ±0,03 mg/g, Ca 1,246 ±0,05 mg/g, Na 0,550 ±0,08 mg/g, K 7,49 ±0,41 mg/g, Fe 79,3 ±6,16 mg/kg, Zn 11,4 ±3,33 mg/kg. Obtained data were statistically processed on significance level 0,05. Based on the principal components analysis, it was found, that the best parameters to differentiate samples from Czechia, Poland and Ukraine from other countries were content of nitrogen, phosphorus, magnesium, sodium and calcium. It was also discovered, that genus differences between onion and garlic have greater significance than geographical differences.
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Analysis of sweet peppers of different geographical origin
Fiala, Petr ; Mikulíková, Renata (referee) ; Diviš, Pavel (advisor)
The diploma thesis is focused on the determination of basic nutritional properties of 26 samples of ground pepper from different countries and evaluates, whether the chemical composition of ground pepper is affected by the geographical origin. The amount of 19 nutritional properties were determined by advanced analytical methodes (ICP-OES, HPLC DAD, HPLC ELSD) together with other laboratory techniques. Final results were statistically processed by the methods of analysis of variance (ANOVA), cluster analysis, principal component analysis (PCA) and discriminant analysis (DA). Statistical evaluation confirmed, that the chemical composition is affected by the geographical origin. Analysis of variance (ANOVA) determined 14 parameters to statistically differ (p
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Modification of soda lignin isolated from winery waste
Chovanec, Martin ; Mikulíková, Renata (referee) ; Kovalčík, Adriána (advisor)
This bachelor thesis provides research on the antibacterial activity of lignin isolated from grape pomace. To separate lignin from grape pomace was used soda lignin isolation method. This method helps to dissolve lignin in the solution of sodium hydroxide. Two isolation procedures were used: 1) isolation by using a conventional laboratory set-up at atmospheric pressure and a temperature of 110 °C and 2) isolation by using a hydrothermal autoclave at increased pressure and a temperature of 110 °C. The hydrothermal autoclave was explicitly developed for this bachelor thesis. Both separations methods were compared from the viewpoint of lignin yields and lignin purity. The lignin yield obtained by using the hydrothermal autoclave was much higher compared to the conventional laboratory set-up, yielding about 36.4 g of soda lignin per 100 g of grape pomace. The infrared spectroscopy analysis of both lignins showed that lignin received by using the conventional laboratory set-up was mixed with hemicelluloses and cellulose. The isolation by using the hydrothermal autoclave enabled to prepare lignin with higher purity. Lignin isolated from grape pomace did not show any antimicrobial activity. The antimicrobial activity was reached after modification of lignin with silver particles in situ. Antimicrobial activity was tested against Bacillus subtilis, Escherichia coli, Micrococcus luteus, Serratia marcescens, Saccharomyces cerevisiae and Candida glabrata. The lignin/silver compound showed the antibacterial activity against all tested bacteria, however no antimicrobial activity against yeasts.
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Determination of athenticity of plant foods by molecular techniques
Plášková, Anna ; Mikulíková, Renata (referee) ; Němcová, Andrea (advisor)
The aim of presented diploma thesis was to determination of authenticity of fruit baby foods for early infant feeding using molecular methods. In the experimental part, isolation kit was used for isolation of plant DNA from fruits (strawberry, apricot, raspberry, apple) and from six commercial fruit products for children. Isolated DNA was characterized and verified using PCR methods with primers specific for plant rDNA (ITS2). Specific primer pairs were designed to amplify DNA for the detection of one fruit species. Primer specificity was assessed with four fruit species. A mixture of fruit puree from the two fruits was used to determine the sensitivity of the multiplex PCR assay. Six commercial fruit products were evaluated to verify the applicability of the multiplex PCR assay. The methodology of molecular detection of fruit DNA by qPCR and multiplex qPCR (duplex) includes approaches, which enable to detect two fruits (strawberry-raspberry, apricot-apple) in one reaction and thus reduces time and money requirements.
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Optimization of extraction of pigments from yeast and algae cells
Šimanský, Samuel ; Mikulíková, Renata (referee) ; Márová, Ivana (advisor)
The presented diploma thesis deals with the extraction and storage stability of lipophilic pigments produced by selected strains of yeasts and algae. In this thesis, there was studied the influence of the selected solvents on the efficiency of extraction, as well as the effect of ambient temperature on the stability of the pigments during storage. The work is divided into two main parts, theoretical and practical part. In the theoretical part knowledge about algae, yeasts and their cultivation parameters is summarized. Furthermore, some information regarding the selected lipid metabolites, their properties and possibilities of application in various branches of industry is mentioned. The practical part deals with the preparation of extracts and stability tests. Extracts were prepared from selected biomass samples in solvents suitable for applications in food industry or cosmetics (ethanol and hexane). Subsequently, the long-term stability tests lasting 4 months and short-term stability tests lasting a total of 28 days were performed on these extracts. The pigments were determined by HPLC and spectrophotometrically, the fatty acid content was determined by GC. For the extraction of pigments from biomass, in the most cases ethanol appears to be the optimal solvent. However, for lipid extraction from biomass, hexane appears to be the optimal solvent for a significant number of samples. In most samples, storage in the freezer showed the most favourable effect on pigment stability, but some samples showed comparable stability even when stored in the refrigerator.
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Influence of oil used on composition and sensory quality of cheese analogues
Buldra, Martin ; Mikulíková, Renata (referee) ; Vítová, Eva (advisor)
This paper deals with the manufacture and characterisation of cheese analogues, which are products, where the milk components are totally or partially replaced by non-milk components. Model samples, edam type cheese and the analogue containing hazelnut oil, were manufactured using the standard way at Brno Mendelu. The main parameters chosen to describe the quality of samples were free and bound fatty acids, volatile compounds and sensory quality. The main aim was to judge the influence of added hazelnut oil on mentioned parameters. For the identification and semiquantification of volatile compounds HS-SPME-GC-MS method was used. Fat extraction from sample was made with a mixture of two solvents (diethylether, petrolether), fatty acids were identified and quantified by GC-FID, with their former acid transesterification using methanolic solution of BF3 as a catalyst. For sensory analysis of the appearance, colour, texture, aroma, taste and overall acceptance of the sample descriptive scales and comparison with standard were used, the structure was observed by electron microscopy. The results show that addition of hazelnut oil affects the sensory properties, ripening process (higher amount of volatile compounds, faster lipolysis), nutrition value (higher amount of unsaturated fatty acids), and the stability of the product.
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Optimization of cultivation of carotenogenic yeasts on mixed waste substrates
Holub, Jiří ; Mikulíková, Renata (referee) ; Márová, Ivana (advisor)
The master thesis addresses the issue of cultivation of selected strains of carotenogenic yeasts on waste materials of the food industry using a laboratory bioreactor. Carotenogenic yeasts are able to produce highly valuable metabolites during cultivation, which are located predominantly in the lipid part of the cells. Particularly, they are carotenoids, ergosterol, coenzyme Q and fatty acids. The thesis is divided into two main parts, the theoretical part and the practical part. The theoretical part describes individual yeast strains, types of waste materials, produced metabolites and methods of their analysis. The experimental part deals with the processing of waste materials of the food industry, specifically animal fat, whey and spent coffee grounds into the form of substrates usable as nutrition sources for yeast cultivation. Furthermore, cultivations focused on the recovery of the monitored metabolites and their analysis by using HPLC/PDA and GC/FID assemblies were studied as well. The yeast strains Rhodotorula mucilaginosa (CCY 19-4-6), Rhodotorula kratochvilae (CCY 20-2-26), Rhodosporidium toruloides (CCY 062-002-001), Sporidiobolus pararoseus (CCY 19-9-6) a Cystofilobasidium macerans (CCY 10-1-2) were used in this work. As one of the best producing strains Sporidiobolus pararoseus (CCY 19-9-6) was found, which achieved very high productions of carotenoids, coenzyme Q and ergosterol.
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