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Characterization of lipids in fresh cheeses
Vaňková, Veronika ; Křikala, Jakub (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the determination of fatty acids in samples of fresh cheeses with or without the addition of plant extracts (rhyme, echinacea), produced in laboratory conditions at FCH BUT. The theoretical part of the thesis focuses on the general characterization of lipids and fatty acids. The next part discusses the characterization, division, and methods of cheese production, focusing mainly on fresh cheeses. The end of the work is devoted to gas chromatography as a method for the determination of fatty acids in cheese samples. The experimental part aimed to determine the content of fatty acids in the samples of fresh cheese. For the extraction of lipids from cheese samples, the choice of the method was according to ČSN EN ISO 1735. Acid esterification with boron trifluoride as a catalyst was used for the preparation of fatty acid methyl esters. The determination of fatty acid methyl esters was performed by gas chromatography with a flame ionization detector (FID). A total of 14 fatty acids were identified in all samples in a bound and free form. Myristric, palmitic, stearic and oleic acids predominated in all samples, which is in agreement with the knowledge of the composition of milk fat. The obtained results show, that even due to slight differences in the content of individual fatty acids, the addition of extracts does not affect the composition of fatty acids in fresh cheeses.
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Production of acid- vs. rennet-curd fresh cheese varieties
Veselá, Vendula ; Suská, Alžběta (referee) ; Vítová, Eva (advisor)
This bachelor thesis‘ focus is on the production and characterization of fresh cheese. Model samples of fresh cheese were produced on VUT Brno using purely acidic curdling (cream cheese culture – lactic acid), combined curdling (cream cheese culture + rennet) and acidic combined with heat curdling (acetic acid. 92 C) The samples were observed for their content of bound and free fatty acids, volatile (aromatic) substances and for their sensory quality. The goal was to determine the influence of the method of curdling on the observed factors. The fats were extracted from the samples using a mixture of diethyl ether and petroleum ether solvents. The fatty acids were esterified with acid to methyl esters under boron trifluoride catalysis and identified by the GC-FID method. In the cheese curdled by combined curdling, a greater amount of free fatty acids was detected compared to the other samples. No significant difference in the amount of bound fatty acids was observed. The greatest fatty acid content overall was observed in the cheese produced by acidic curdling. For identification and semi-quantification of the volatile (aromatic) substances, an HS-SPME-GC-MS method was used. 72 volatile compounds were identified in the samples. The percentual representation of different chemical groups varied significantly, the highest number of volatile substances was observed in the cheese produced by acidic curdling. Sensory evaluation was conducted using an evaluation scale as well as a ranking test. In all the observed indicators, the commercial sample was evaluated the best. The cheese produced by combined curdling was received rather negatively due to the sour taste. The second-best cheese was ranked to be the cheese produced by acidic curdling. The results show that the acidic curdling is the best for taste as well as aromatic substance and fatty acid content. If we, however, consider other factors such as the time taken, the cheese produced by combined curdling appears to be the best overall.
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Production and characterization of cheese with the addition of plant extract
Kučerka, Štefan ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This master´s thesis deals with production and characterization of fresh cheese with addition of herb extracts, specifically extracts from Plectranthus amboinicus and Echinacea purpurea. The purpose of this thesis was to prepare samples with higher sensory quality and nutritional value. Produced cheeses were characterized in terms of volatile (aroma) substances, fatty acid content, total phenolic substances, antioxidant activity and sensory quality. Cheese sample with added extract from E. purpurea reached the highest value of total phenolic compounds (0,172 ± 0,019 mgGAEg-1 of cheese) and antioxidant activity (91,2 ± 2,2 gTEACg-1 of cheese). Cheese sample with added extract from P. amboinicus, compared to standard cheese sample (without added extract) also reached higher values of total phenolic compounds and antioxidant activity. 43 volatile (aroma) compounds were identified in both samples with added extracts (P. amboinicus, E. purpurea), in standard cheese sample it was 33. In sample with E. purpurea camphor was present in high amount (15,23 %) responsible for the camphor aroma, camphor was also identified in small amount in sample with P. amboinicus. Highest volatile matter content was identified in sample with P. amboinicus. Standard cheese sample was rated as the best from the sensory perspective. Addition of extracts had negative effect on color, taste, and aroma perception of cheese. Strongest herbal taste was identified in sample with E. purpurea, brownish color of this sample manifested in lower pleasantness of color. Obtained results show, that extract addition increases the nutritional value of cheese (higher content of aromatic substances and phenolic compounds, higher antioxidant activity), but lowers sensory quality and overall consumer acceptability.
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DNA extraction from cheeses for polymerase chain reaction analysis
Mohelský, Tomáš ; Rittich, Bohuslav (referee) ; Španová, Alena (advisor)
This work was focused on DNA isolation from cheeses for the use in polymerase chain reaction. First, there was optimised the procedure of homogenisation of different types of cheeses from commercial sources, cell lysis and DNA isolation. DNA was isolated using magnetic microspheres and phenol extraction. It was shown that the DNA was amplified in PCR for domain Bacteria after dilution. Next, there was optimised the procedure of DNA isolation from fresh cheeses and from contaminated fresh cheeses and their pickles. DNA from all samples was amplified in PCR. The presence of DNA of domain Bacteria and yeast DNA was demonstrated. In the last part of the work, there were optimised the preparation of PCR mixtures and bacterial DNA amplification in PCR with primers with clamp (F357-GC and R518). Synthetized PCR products were analysed using DGGE. It was shown that amplicons of DNA isolated from cheeses and pickles differ in positions and numbers. Larger number of bands of different intensities was detected after amplification of DNA isolated from contaminated pickles.
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Mikrobiologie čerstvých a polotvrdých sýrů – změny v počtech významných skupin mikroorganismů v průběhu výroby a skladování.
Vítová, Jana
The aim of the thesis was to find out whether the numbers of important groups of microorganisms in fresh and semi-hard cheeses change during storage. Changes in the number of microorganisms were detected by microbiological analysis, where significant groups of microorganisms were determined. The total number of microorganisms, psychrotrophic microorganisms, coliforms including Escherichia coli, lactic acid bacteria and micromycetes including yeasts and molds were detected. The microorganisms were detected in fresh cheeses packed in boxes, vacuum packed stored for 14 days and stored for 21 days. The fresh cheeses were produced in the dairy manufactory of the Faculty of AgriSciences at Mendel University and contained four different concentrations of cream starter. For the semi-hard cheeses microbiological analysis was carried out on delivery of the cheeses to the laboratory and subsequently at an interval of either 14 days or 8 weeks. The semi-hard cheeses were obtained from the market. Very low numbers of coliforms and moulds were detected in packaged fresg cheeses. On the other hand, due to the longer storage time, there was a significant decrease in lactic acid bacteria. Longer storage period resulted in higher detection of yeast and psychrotrophic microorganisms. As for semi-hard cheeses that were analysed after 8 weeks, there was a decrease in the total number of microorganisms and lactic acid bacteria. For semi-hard cheeses analysed after 14 days, higher total numbers of microorganisms, psychrotrophic bacteria and moulds were detected. No coliforms were detected in any of the semi-hard cheeses, including Escherichia coli. The results of the work showed that vacuum packaging of fresh cheeses can extend their shelf life. However, longer storage times reduce lactic acid bacteria.
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Technologie výroby čerstvých sýrů v závislosti na použitých surovinách a podmínkách výroby
Koudelková, Jana
In the theoretical part, this diploma thesis first deals with the definition of fresh cheeses and also describes the history of cheeses in general. Subsequently, cheeses are classified based on several factors and the basic representatives of fresh cheeses are described here. It describes what raw materials are necessary for the production of fresh cheese, and how the process of their creation looks step by step. The work contains information on the basic sensory properties of fresh cheeses and possible defects that may occur in fresh cheeses. The last part of the theoretical work is focused on potential factors in the production of fresh cheese that could affect the quality and taste of the final product, including the possibilities of its quality control. In the experimental part of the thesis, raw materials and procedures for the production of fresh cheese were first selected, and then the production of fresh cheese itself took place. After production, the basic chemical and sensory properties of the manufactured products were determined. The results showed that the produced fresh cheeses corresponded chemically to the general values and the spices used significantly influenced parameters such as the taste and aroma of the cheese. Provençal spices were used for flavoring; paprika and pepper; wild garlic and dill; Italian herbs, which in the end were evaluated as the best option for flavoring cheeses. The obtained results were processed into graphs and evaluated statistics.
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Analysis of selected milk quality indicators and their impact on the yield and sensory properties of fresh cheeses
PLONER, Michaela
The aim of the diploma thesis was to evaluate the effect of cow´s milk quality on the fermentation, yield and selected properties of fresh cheese produced in laboratory conditions. For this purpose, there were 51 fresh cheese samples produced in three trials from 17 bulk milk samples originating from six farms. For milk and cheese sam-ples, selected analyzes were performed, and the obtained data were statistically eval-uated. The chemical composition, physicochemical and sensory properties, weight and yield of fresh cheese were evaluated depending on i) the time of fermentation, ii) the milk quality. As expected, the average values of pH, weight and yield of the fresh cheeses differed during the fermentation. The protein content, lactose and so-matic cell counts significantly influenced the yield and quality indicators of fresh cheese. The quality of milk also influenced the assessment of sensory properties, es-pecially color intensity and consistency. To achieve the optimal pH of fresh cheese (<5.00), the time of fermentation should be from 15 to 16 hours.
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Optimization of fresh cheese production and their characterization
Bittnerová, Eva ; Pořízka, Jaromír (referee) ; Vítová, Eva (advisor)
This thesis deals with the optimization of fresh cheese production and their characterization in terms of free and bound fatty acids, volatile (aromatic) substances and sensory quality. The theoretical part deals with the characterization of fresh cheeses, their production technology and sensory quality. It also includes options for determining volatile substances and fatty acids in fresh cheeses. In the experimental part, produced fresh cheese samples were analyzed during 14-day storage. The fat was extracted from fresh cheeses with a mixture of diethyl ether and petroleum ether, fatty acids were converted to the appropriate methyl esters by acid esterification with boron trifluoride as a catalyst and determined by gas chromatography with a flame ionization detector. Volatile substances were identified based on the comparison of mass spectra with a library of spectra and retention indices (according to Van den Dool and Kratz). The content of the identified substances was expressed semi-quantitatively using the areas of the respective peaks. A total of 20 fatty acids were identified, palmitic, myristic, stearic, capric, caproic and lauric acids predominated as representatives of saturated fatty acids, oleic acid as a representative of monounsaturated fatty acids, and linoleic acid was abundantly represented among polyunsaturated fatty acids. In terms of volatile substances, a total of 37 compounds were identified in the frozen samples and 42 compounds in the fresh samples. Alcohols, acids, aldehydes and ketones were the most represented. The results of the sensory evaluation show that the evaluators liked the stored cheeses better, so the cheeses maintain a good quality of min. for 14 days when stored in the refrigerator.
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Production of acid- vs. rennet-curd fresh cheese varieties
Veselá, Vendula ; Suská, Alžběta (referee) ; Vítová, Eva (advisor)
This bachelor thesis‘ focus is on the production and characterization of fresh cheese. Model samples of fresh cheese were produced on VUT Brno using purely acidic curdling (cream cheese culture – lactic acid), combined curdling (cream cheese culture + rennet) and acidic combined with heat curdling (acetic acid. 92 C) The samples were observed for their content of bound and free fatty acids, volatile (aromatic) substances and for their sensory quality. The goal was to determine the influence of the method of curdling on the observed factors. The fats were extracted from the samples using a mixture of diethyl ether and petroleum ether solvents. The fatty acids were esterified with acid to methyl esters under boron trifluoride catalysis and identified by the GC-FID method. In the cheese curdled by combined curdling, a greater amount of free fatty acids was detected compared to the other samples. No significant difference in the amount of bound fatty acids was observed. The greatest fatty acid content overall was observed in the cheese produced by acidic curdling. For identification and semi-quantification of the volatile (aromatic) substances, an HS-SPME-GC-MS method was used. 72 volatile compounds were identified in the samples. The percentual representation of different chemical groups varied significantly, the highest number of volatile substances was observed in the cheese produced by acidic curdling. Sensory evaluation was conducted using an evaluation scale as well as a ranking test. In all the observed indicators, the commercial sample was evaluated the best. The cheese produced by combined curdling was received rather negatively due to the sour taste. The second-best cheese was ranked to be the cheese produced by acidic curdling. The results show that the acidic curdling is the best for taste as well as aromatic substance and fatty acid content. If we, however, consider other factors such as the time taken, the cheese produced by combined curdling appears to be the best overall.
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Production and characterization of cheese with the addition of plant extract
Kučerka, Štefan ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This master´s thesis deals with production and characterization of fresh cheese with addition of herb extracts, specifically extracts from Plectranthus amboinicus and Echinacea purpurea. The purpose of this thesis was to prepare samples with higher sensory quality and nutritional value. Produced cheeses were characterized in terms of volatile (aroma) substances, fatty acid content, total phenolic substances, antioxidant activity and sensory quality. Cheese sample with added extract from E. purpurea reached the highest value of total phenolic compounds (0,172 ± 0,019 mgGAEg-1 of cheese) and antioxidant activity (91,2 ± 2,2 gTEACg-1 of cheese). Cheese sample with added extract from P. amboinicus, compared to standard cheese sample (without added extract) also reached higher values of total phenolic compounds and antioxidant activity. 43 volatile (aroma) compounds were identified in both samples with added extracts (P. amboinicus, E. purpurea), in standard cheese sample it was 33. In sample with E. purpurea camphor was present in high amount (15,23 %) responsible for the camphor aroma, camphor was also identified in small amount in sample with P. amboinicus. Highest volatile matter content was identified in sample with P. amboinicus. Standard cheese sample was rated as the best from the sensory perspective. Addition of extracts had negative effect on color, taste, and aroma perception of cheese. Strongest herbal taste was identified in sample with E. purpurea, brownish color of this sample manifested in lower pleasantness of color. Obtained results show, that extract addition increases the nutritional value of cheese (higher content of aromatic substances and phenolic compounds, higher antioxidant activity), but lowers sensory quality and overall consumer acceptability.
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