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Characterization of cheese analogues produced with addition of nut oil
Mitra, Michal ; Diviš, Pavel (referee) ; Vítová, Eva (advisor)
This thesis deals with the production and characterization of cheese analogues, i.e. products where some of the dairy components are partially or completely replaced by a non-dairy component. Model samples – Eidam type cheese and analogue with the addition of pistachio oil, were produced by a conventional technological process at MENDELU in Brno. Free and bound fatty acids, volatile substances and sensory quality were selected and monitored as the main characterizing parameters of the sample quality. The aim was to characterize the differences between the samples caused by the addition of nut oil in the monitored parameters. The HS-SPME-GC-MS method was used for the identification and semi-quantification of volatiles. The extraction of fats from the samples was performed with a mixture of solvents (diethyl ether, petroleum ether), fatty acids were converted to methyl esters by acid esterification with methanolic solution of boron trifluoride as a catalyst and subsequently identified and quantified by GC-FID. Descriptive scales and comparisons with standard were used to sensory evaluate the appearance, color, texture, odor, taste, and overall acceptability of the samples. The structure was monitored by electron microscopy. The results show that the addition of pistachio oil affects the sensory properties, the maturation process (higher content of volatile substances), the nutritional value (increased content of unsaturated fatty acids) and the stability of the product.
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Assessment of chosen aroma compounds in foods
Greifenthalová, Ivana ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This diploma thesis is focused on the problematic of assessment of 26 most important allergenic aroma compounds in foods, flavoured herbal teas were chosen as the model samples. Aroma is the one of the main characteristics of tea, which is closely linked to taste and odour. The theoretical part of this work is focused on the characteristics of tea, tea types, producing technology, classification according to the fermentation and also their undeniable impact on the human organism. In the experimental part, the allergenic aroma compounds in 10 chosen samples of flavoured tea were identified and quantified using the solid phase microextraction (SPME-GC-FID) in conjunction with gas chromatography. The work also includes sensory evaluation of taste and smell of tea samples by qualified assessors.
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Biologically active substances of chokeberry (Aronia spp.)
Palkovská, Kateřina ; Pořízka, Jaromír (referee) ; Vítová, Eva (advisor)
This master thesis deals with preparation of extracts from fruits of aronia, optimization of conditions for extraction and subsequent characteristics of the obtained optimal extract. In the theoretical part information about the botanical characteristics of Aronia melanocarpa and about its utilization are mentioned. Furthermore, the chemical composition of aronia fruits is described and the main biologically active substances contained in the plant are described. At the end of the theoretical part extraction and separation techniques, determination methods of antioxidant, antimicrobial activity and determination of aromatic active compounds are described. The experimental part describes the optimization of maceration so that the macerate contains as much polyphenolic substances as possible, as well as aromatic active substances. 40% ethanol, at a temperature of 60 ° C, with a weight solvent ratio of 1: 5, for 40 minutes proved to be optimal for the maceration of aronia fruits. The total polyphenol content of the optimal extract was determined to be 5237.2 ± 40.7 mgGAEkg-1 and the antioxidant activity by TEAC to be 512.5 ± 5.04 gml-1. 24 aromatic active compounds were identified in the extract, with the largest percentage being monoterpenes and aldehydes. Furthermore, it was found that the extract did not show antimicrobial activity against the microorganisms used (Bacillus cereus, Escherichia coli and Candida glabrata). The obtained results confirm that aronia extracts are an important source of many biologically active compounds and can be used in food as a natural source of nutritionally and sensory valuable substances.
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Preparation and characterization of plant extracts for application to syrups
Šandová, Lucie ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
The aim of the diploma thesis was to produce herbal syrups from three selected herbs of the Lamiaceae family - Salvia officinalis, Melissa officinalis and Mentha piperita. First, extracts were prepared from these herbs by maceration in 25% of ethanol (60°C, 90 min). From the prepared herbal extracts, herbal syrups were made by mixing with syrup base (65% sucrose solution + lactic acid 2 g.l-1) in different ratios (2:1, 1:1, 1:2 - extract: base of the syrup). On the basis of sensory evaluation, a ratio of 1:1 was selected as optimal. The extracts and syrups produced were characterized in terms of volatile profile, phenolic content, antioxidant activity and antimicrobial activity. The produced syrups were also evaluated sensorially using scales, profile, and order test, and compared with similar commercial samples (Baťkovy sirupy s.r.o.). The HS-SPME-GC-MS method was used for the determination of volatile substances, the Folin-Cicalteu method for total phenolics, the TEAC method for antioxidant activity and the well and disc diffusion method for antimicrobial activity. 36 volatiles were found in model sage syrup, 29 in commercial syrup; 20 volatiles were found in model lemon balm syrup, 32 in commercial syrup; 25 volatiles were found in model mint syrup, 41 in commercial syrup. The quantitative distribution of the most important compounds in the commercial and manufactured syrups differed, with terpenes predominating in all samples. The content of phenolic compounds in syrups decreased in the order sage (570.1 mg.l-1) > lemon balm (378.9 mg.l-1) > mint (96.5 mg.l-1), antioxidant activity in the order lemon balm (332.0 µg.ml-1) > sage (185.6 µg.ml-1) > mint (115.8 µg.ml-1). Commercial syrups showed significantly higher phenolic compound content and antioxidant activity than manufactured syrups for all three herbs. In terms of sensory quality, mint syrup was considered the most palatable and sage syrup the least palatable (mint > lemon balm > sage); only in the case of lemon balm was the manufactured syrup considered better, more palatable than the commercial sample. It was reasonably liquid, clear of a pleasant colour, with a distinctly sweet, slightly herbaceous taste and a pleasant aroma.
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Influence of aroma compounds on sensory quality of sweets
Motúzová, Eliška ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This master´s thesis is focused on determination of aroma active compounds in non-chocolate sweets and their influence on sensory quality/flavour. The theoretical part describes production of non-chocolate sweets, characterizes aroma active compounds including allergenic ones, method for their determination by solid-phase microextraction and gas chromatography with mass detection. For experimental part were used as model samples gummy candies purchrased in regular market. Four flavors were used, specifically yellow (lemon), green (apple), red (strawberry) and orange (orange). The HS-SPME-GC-MS method was used to identify volatile aroma active compounds. To evalutate the sensory quality were used scales, a profile test, and a time course evaluation. Owerall 120 volatille compounds were identified including 8 allergens.
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Production and characterization of non-chocolate sweets with the addition of plant extracts
Knapovská, Pavlína ; Nábělek, Jakub (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the production and characterization of plant extracts of green tea (Camellia sinensis) and sea buckthorn (Hippophae rhamnoides) and non-chocolate sweets – hard candies with the addition of plant extracts. These plants are characterized by a high content of bioactive substances, upon which the prepared extracts and candies were characterised. Determination of volatile substances by HSSPME-GC-MS, antioxidant activity by method with ABTS, determination of total phenols by Folin-Ciocalteu method and sensory analysis were performed. The produced sweets were then compared with similar commercial products. A total of 6 volatile substances were identified in the sample of hard candy with the addition of green tea extract, the antioxidant activity of the sample was determined to be 253,3 ± 0,9 µgml–1 and the total phenolic content was determined to be 0,49 ± 0,02 mgGAEg–1 per 1 g of candy. A total of 8 volatile substances were identified in the hard candy with the addition of sea buckthorn extract, the antioxidant activity of the sample was determined to be 206 ± 3 µgml–1, the total phenolic content was determined to be 0,51 ± 0,04 mgGAEg–1 per 1 g of candy. The obtained results show that the addition of extracts increases the nutritional value (higher antioxidant activity, higher content of phenolic compounds) of produced candy; from a sensory point of view, however, only samples with green tea were evaluated positively, the addition of sea buckthorn extract was not very attractive for consumers, they considered sweets with sea buckthorn to be too bitter.
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Obtaining and complex charaterization of Aronia spp. extracts
Seidlová, Kateřina ; Zemanová, Jana (referee) ; Veselá, Mária (advisor)
Aronia (Aronia melanocarpa) is a berry fruit with distinctive sensory characteristics and health-promoting properties. Polyphenols are the main bioactive compounds found in aronia including natural pigments – anthocyanins. Bioactive compounds are usually obtained from natural materials by extraction, in this work, two methods of extraction were compared – maceration and PHWE. Based on the total phenolic content, maceration was chosen as a more suitable method and then was optimized with statistical model – Design of Experiment. Optimal conditions were set to temperature of 30 °C, extraction agent 50 % ethanol, solid-solvent ratio 10 g per 50 ml and time of extraction for 30 minutes. Extract obtained under these conditions was characterised by total phenolic content – 1441 ± 90 mg/100 g DW, total anthocyanin content 943 ± 8 mg/100 g DW and antioxidation activity by ABTS 24,78 ± 0,09 molTE/g. In total of 25 volatile compounds were indentified in the optimal extract with content > 0,5 %. Major part created aldehydes and esters, with the main compounds being benzaldehyde (32,25 %) and methyl hexanoate (21,37 %).
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Preparation and characterization of Echinacea extracts
Pallová, Jana ; Veselá, Mária (referee) ; Vítová, Eva (advisor)
Echinacea purpurea is a rich source of biologically active compounds, which are attributed to several therapeutic effects. This thesis is focused on the optimization of the extraction process, considered these substances. Maceration was chosen as a type of extraction, due to its simplicity. The Optimal conditions were solid-solvent ratio 1: 5, 40% ethanol, 60 °C, 60 minutes. An extract from the dried flowers of Echinacea purpurea was prepared by this optimized process. The content of total phenolic compounds was set on 365.18 ± 3.51 [mg_GAEl^(-1)] and the antioxidant activity was 507.50 ± 6.89 [mg_TEACl^(-1)]. The percentage of radical scavenging activity ABTS•+ was 95.45 ± 1.30. The antimicrobial activity of the extract was tested against 3 microorganisms – Escherichia coli, Bacillus cereus and Candida glabrata. There was not detected inhibitory effect on the growth of microorganisms. In a total, 39 volatile compounds were identified, and the biggest group were represented sesquiterpenes (70.9%). The obtained results confirm that Echinacea extract has antioxidant activity and contains several interesting aromatic substances, In the future, it can be used as a natural resource of nutritionally and sensory valuable compounds, e.g., into various foods and delicacies.
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Characterization of nut oils
Coufalová, Dominika ; Sýkora, Michal (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the characterization of selected nut oils, almond and pistachio virgin oils. The teoretical part concentrates on the description of nut fruits, the characterization of aroma-active compounds, fatty acids and their content in the nut oils. After that, the fatty characteristics, which determines the oil quality, and instrumental methods selected for individual assignment are described. In the experimental part there were 42 volatile compounds identified in the nut oils by the headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry, 35 were found in almond oil and 24 were found in pistachio oil. Free and bound fatty acids were converted into methyl esters using acid-catalysed esterification with boron trifluoride-methanol solution as a catalyst and then they were determined by gas chromatography with flame ionization detection. There were 12 fatty acids identified in almond oil and 14 fatty acids in pistachio oil. Oleic acid and linoleic acid predominated in both samples. The quality and properties of nut oils were valued by determining the fatty characteristics (acid value, saponification value, ester value, iodine value by Hanus method and peroxid value). The increased value of peroxide value was found in both oils which correlates with the trait and storage time of samples.
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