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Influence of storage on the microbial composition of French Saint-nectaire cheese
Šislerová, Lucie ; Mikulíková, Renata (referee) ; Brázda, Václav (advisor)
The aim of my work is the comparison of microbial composition between farmtype and dairytype of Saint-nectaire cheese and the influence of storage time and temperature on the development of microbial composition, content of fatty acids and aromatic substances. Selected microorganisms were identified by RT-PCR. In addition, Penicillium roqueforti and fuscoglaucum have been identified in the Saint-nectaire farm type compared to the dairy type. In both types of cheese, the highest amount of selected microorganisms was detected in fresh cheese. When stored at 20 °C, an increase over fresh cheese occurred in the following microorganisms: Streptococcus thermophilus, Lactobacillus bulgaricus, Cladosporium herbarum and Penicillium commune and camemberti, and the presence of contaminants and pathogens was noted. After one week of storage at 20 °C, they were Micrococcus luteus, Salmonella enterica and Staphylococcus aureus, and after another two weeks of storage, Listeria monocytogenes was identified. The fatty acid and volatile compounds were compared for five samples: fresh cheese, cheese stored in the refrigerator for one week and three weeks and cheese stored at 20 °C for one week and three weeks. The content of bound and free fatty acids was measured, both by GC-FID. The content of bound fatty acids was comparable in all measured samples. The highest content of free fatty acids was in the cheese after three weeks of storage at 20 °C. The most common fatty acid is palmitic acid. Volatiles were determined by HS-SPME-GC-MS. The most volatiles were identified in the cheese after three weeks at 20 °C and in the cheese after one week in the refrigerator. The most represented groups were alcohols, ketones and acids.
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Assessment of fatty acids in selected type of cheese
Chmelařová, Adéla ; Sůkalová, Kateřina (referee) ; Vítová, Eva (advisor)
This bachelor thesis is focused on identification and quantification of free and bound fatty acids in commercially available white mold cheeses: Hermelín, Kamadet and Olmín, using gass chromatography withflame ionization detection. Theoretical part of the thesis is dealing with the classification of cheeses with the main attention to white mold cheeses. In a following part cheese production technology is described, lipids and fatty acids are characterised including the possible methods for their assessment, mainly gass chromatography. Experimental part the contents of free and bound fatty acids in selected samples of white mould cheeses were compared. The method in accordance with ČSN EN ISO 1735:2005 was selected for lipid extraction. Fatty acids were identified as methylesters using acid esterification with methanolic solution of bortrifluorid as a catalyst. In total 21 free and bound fatty acids were detected in samples.
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Characterisation of elderberry fruits
Christovová, Silvia ; Diviš, Pavel (referee) ; Vítová, Eva (advisor)
This master's thesis deals with the characterization of elderberry fruit (Sambucus nigra L.) with emphasis on the aroma active compounds (AAC) and vitamin C (ascorbic acid (AA), dehydroascorbic acid (DHA)). The theoretical part gives a brief outlook on the chemical composition and attributes of Sambucus berries, its healing properties and the means of processing. The rest of the theoretical part thoroughly examines the AAC and vitamin C. The suitable assessment methods are also discussed. The experimental part of the work consists of two main tasks. The first one was to assess the aroma profile of Sambucus berries using the HS-SPME-GC-FID. 18 samples were examined (the wild elderberry and 17 cultivated varieties). In total, 24 different volatile aroma active compounds were identified and quantified, 12 of which belonged to alcohols, 5 to aldehydes, 4 to esters, 1 to acids and 2 “other” compounds (linalool and -damascenone). The chemical composition of the individual samples was not uniform; no single sample contained all of the identified compounds. The second task was to assess the total vitamin C content (the sum of DHA and AA) using the HPLC. For the purpose of reducing DHA to AA three reducing agents were examined (DTT, TCEP and L-cysteine) at two different pH levels (7 and 4). TCEP at pH 4 turned out to be most efficient and was subsequently applied on the samples of 5 selected elderberry varieties. The measured vitamin C content was within the range of 5,1 – 13,0 mg per 100 g of fruit.
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The selection and optimization of the method for assessment of free fatty acids
Koval, Dominik ; Vespalcová, Milena (referee) ; Vítová, Eva (advisor)
This master´s thesis deals with optimization and validation of method for determination of free fatty acids. The theoretical part is focused on possibilities of extraction, extract separation, esterification, gas chromatography determination and brief description of the most important validation parameters. All with main emphasis on applying on free fatty acids. The experimental part describes the selection and procedure of optimizing individual steps of the method. Extraction of lipids was performed by solvent mixture (diethylether/petroleumether), based on the standard ČSN EN ISO 1735, for the extraction of free fatty acid solid phase extraction was tested. The acid catalyzed esterification based on ČSN EN ISO 5509 using methanolic solution BF3 was used for derivatization of free fatty acids and a gas chromatograph with a flame ionization detector was used for their determination. Subsequently, selected validation parameters of the method were verified: repeatability, reproducibility, linearity, limits of detection and quantitation. Sunflower oil and emmental type cheese, bought in common food market, were used as model samples for selection and optimatization of the method.
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Profile of fatty acids in Edam type cheese
Babištová, Lucie ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This bachelros thesis is focused on identification and qualification of free and bound fatty acids in edam type cheese. The samples were produced in Univarsity of Tomáš Baťa in Zlín. The theorytical part characterizes the cheese, their classification, composition and production process. This part also contains description of fats, fatty acids and gas chromatography with flame ionization detector. In the experimental part the contents of free and bound fatty acids in the model samples, produced using combination of microbial cultures are determined and compared. The method described in EN ISO 1735:2005 was used for extraction of lipids from the samples. Fatty acids were converted to methylesters by acidic esterification with methanolic solution of bortrifluoride as a catalyst. Then the fatty acids were assessed using the gas chromatography with flame ionization detector. The total number of 17 fatty acids in both free and bound form were assessed in samples. Unequivocal influence of addition of thermophilic culters on the contents of fatty acids cannot be proven.
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Processing of selected species of edible insects for food purposes
Masár, Martin ; Lacina,, Lubor (referee) ; Svěrák, Tomáš (advisor)
Táto diplomová práca je zameraná na nutričné zhodnotenie vybraných práškov hmyzu zo svrčkov domových, z lariev múčiara obyčajného a potemníka stajňového a jedného potravinového produktu na báze hmyzu, ktorý bol tiež vyvinutý ako jeden z cieľov tejto práce. Okrem základných nutričných analýz boli použité aj ICP-OES pre zistenie obsahu minerálov a GC-FID pre zistenie zloženia mastných kyselín. Tiež bol stanovený obsah hrubej bielkoviny pomocou CHNSO analyzátora a stanovený obsah EAA. Pomocou PCA analýzy sa úspešne podarilo rozlíšiť vzorky jednotlivých hmyzích práškov, ktoré potvrdili rozmanitosť jednotlivých druhov hmyzu a vďaka projekcii do roviny hlavných komponent je možné vidieť, v ktorých nutričných parametroch sa najviac líšia. Bola tiež vykonaná senzorická analýza novo vyvinutého produktu na báze hmyzu s prídavkom prášku z potemníka stajňového v porovnaní s konkurenčnými produktmu. Súčasťou práce je aj rozsiahly spotrebiteľský prieskum na vzorke 2 019 účastníkov, týkajúci sa vnímania entomofágie v Českej republike a na Slovensku, ktorý sa uskutočnil online.
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Study of extraction of biologically active substances into fatty base
Komárek, Šimon ; Vítová, Eva (referee) ; Zemanová, Jana (advisor)
This diploma thesis deals with macerates of comfrey (Symphytum officinale) in selected fats (food lard, cosmetic lard and almond oil). Selected fats were first characterized by dry matter content, saponification, acid, iodine number, peroxide value. At the same time, total and free fatty acids were determined using GC-FID. Macerates were prepared by extraction of comfrey roots with selected fats. In prepared macerates the change in acid and peroxide value was monitored, as well as the content of selected bioactive compounds. The content of total phytosterol and total carotenoid content was determined by UV-VIS spectrometry, phytosterols and carotenoids were also analysed using HPLC-DAD. Total phenolic content was measured using Folin-Ciocalteu reagent and antioxidant activity by ABTS assay. The measured properties were then compared with industrially produced comfrey ointment. In macerated fats the increase in acid and peroxide value was determined. Furthermore, an increase in the content of total phytosterols and total carotenoids was observed. Using HPLC-DAD the content of -sitosterol and stigmasterol was determined, but carotenoids were not detected. Of the tocopherols, only DL--tocopherol acetate was detected. During maceration, the content of total phenolic compound in fat increased, which caused a change in antioxidant activity.
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Characterization of lipids in cheese analogues
Bittnerová, Eva ; Šimíčková, Adéla (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the identification and quantification of free and bound fatty acids in samples of vegetable oils, specifically in linseed and rapeseed, and in cheese analogues made from them. The theoretical part deals with the characterization of cheese analogues, the composition and technology of fresh cheese production and the description of selected vegetable oils. It also contains the principle and instrumentation of gas chromatography with a flame ionization detector. In the experimental part, model samples of fresh cheese analogues with the addition of linseed and rapeseed oil and the corresponding oil as the basic raw material for their production were analyzed. The fat was extracted from the cheese analogues with a mixture of diethylether and petroleumether, the fatty acids were converted to methylesters by acid esterification with methanolic bortrifluoride catalyst and determined by gas chromatography with flame ionization detection. A total of 15 fatty acids were identified, predominantly oleic, linolenic and palmitic acids. In both oils, oleic, linoleic and linolenic acids were the most represented; significant amounts of myristic, palmitic and stearic acids were also found in the analog samples. The content of free fatty acids was significantly lower than that bound of all samples.
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The effect of the quantity and type of nuts used in the production of pâté on the product sensory quality
Mejzlíková, Blanka ; Kovalčík, Adriána (referee) ; Mikulíková, Renata (advisor)
This bachelor thesis deals with the sensory evaluation of pâté with nuts. The 9 samples of pâtés which contained different quantity of nuts and different types of nuts were produced for sensory evaluation. In the theoretical part pâtés are characterised, their history, composition and manufacturing are described. The part of literature search is description and chemical composition of nuts which were used for production of pâtés. Another topic is a description of conditionals and methods of sensory analysis and sensory evaluation of meat products. The practical part comprises production of test samples, samples for sensory analysis, evaluating the heat treatment and sensory analysis. Percentage amount of lipids and composition of fatty acids were determined by gas chromatography. Processing of results of sensory and chemical analysis of samples of pâtés was determined that the best samples were pâtés with cashew nuts and pistachios.
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