|
|
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.
|
|
|
Characterization of selected vegetable oils for application in food
Podloučková, Michaela ; Gross, Michal (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the characterization of selected types of nut oils made from almonds, walnuts, and hazelnuts. These oils were cold pressed, and they are available on the regular market. The theoretical part deals with the characterization of individual types of nuts and nut oils. The experimental part deals with the comparison of oils in terms of profile and content of volatile substances and fatty acids. The volatile compounds were identified by gas chromatography with mass spectrometry in conjunction with solid phase microextraction. Ten substances, mainly alcohols, were identified in the nut samples. Most substances were found in hazelnut. A total of 44 volatile substances were found in oil samples, mostly in walnut oil. The main substances were aldehydes and alcohols. Fatty acids in free and bound form were converted to methyl esters by acid esterification with methanolic boron trifluoride solution as catalyst. Fatty acids were identified by gas chromatography with flame ionization detection. Unsaturated fatty acids, mainly oleic (almond, hazelnut) and linoleic (walnut) acids, were present in large quantities in the samples.
|
|
|
Influence of used oil on the composition and sensory quality of cheese analogues
Coufalová, Dominika ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This master thesis deals with the production and characterization of cheese analogues with vegetable oil, specifically almond, hazelnut and walnut oils. The products were characterized by volatile compounds, fatty acids, antioxidant activity and sensory quality, and were compared with the standard product. The samples were described as soft white cheese. Volatile compounds were determined by gas chromatography-mass spectrometry. There were 29 compounds identified both in the standard cheese and the analogue with hazelnut oil, 31 compounds in the analogue with almond oil and 34 compounds in the analogue with walnut oil. The highest content of volatile compounds was found in the analogue with hazelnut oil, and the highest number of terpenes in the analogue with walnut oil. Fatty acids were converted into methyl esters after the extraction of fat by using mixture of organic solvents and then they were determined by gas chromatography with flame ionization detection. There were identified 11 saturated, 3 monounsaturated and 2 polyunsaturated fatty acids in all samples. The higher content was found in all cheese analogues compared to standard sample, moreover the content of unsaturated fatty acids increased. The highest content of polyunsaturated fatty acids was found in the analogue with walnut oil. The cheese analogues showed the higher antioxidant activity compared to standard cheese. A significantly higher content was found in the analogue with hazelnut oil. Oil addition decreased the sensory evaluation of consistence and flavour of samples. The standard cheese reached the highest score of overal acceptability among samples; the strongest nut flavour was described in the analogue with hazelnut oil. The results showed that the addition of oils increases the nutritional value of cheeses (higher content of unsaturated fatty acids, higher antioxidant activity), but reduces their sensory quality and overall consumer acceptability.
|
|
|
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.
|
|
|
Characterization of selected vegetable oils for application in food
Podloučková, Michaela ; Gross, Michal (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the characterization of selected types of nut oils made from almonds, walnuts, and hazelnuts. These oils were cold pressed, and they are available on the regular market. The theoretical part deals with the characterization of individual types of nuts and nut oils. The experimental part deals with the comparison of oils in terms of profile and content of volatile substances and fatty acids. The volatile compounds were identified by gas chromatography with mass spectrometry in conjunction with solid phase microextraction. Ten substances, mainly alcohols, were identified in the nut samples. Most substances were found in hazelnut. A total of 44 volatile substances were found in oil samples, mostly in walnut oil. The main substances were aldehydes and alcohols. Fatty acids in free and bound form were converted to methyl esters by acid esterification with methanolic boron trifluoride solution as catalyst. Fatty acids were identified by gas chromatography with flame ionization detection. Unsaturated fatty acids, mainly oleic (almond, hazelnut) and linoleic (walnut) acids, were present in large quantities in the samples.
|
|
|
Influence of used oil on the composition and sensory quality of cheese analogues
Coufalová, Dominika ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This master thesis deals with the production and characterization of cheese analogues with vegetable oil, specifically almond, hazelnut and walnut oils. The products were characterized by volatile compounds, fatty acids, antioxidant activity and sensory quality, and were compared with the standard product. The samples were described as soft white cheese. Volatile compounds were determined by gas chromatography-mass spectrometry. There were 29 compounds identified both in the standard cheese and the analogue with hazelnut oil, 31 compounds in the analogue with almond oil and 34 compounds in the analogue with walnut oil. The highest content of volatile compounds was found in the analogue with hazelnut oil, and the highest number of terpenes in the analogue with walnut oil. Fatty acids were converted into methyl esters after the extraction of fat by using mixture of organic solvents and then they were determined by gas chromatography with flame ionization detection. There were identified 11 saturated, 3 monounsaturated and 2 polyunsaturated fatty acids in all samples. The higher content was found in all cheese analogues compared to standard sample, moreover the content of unsaturated fatty acids increased. The highest content of polyunsaturated fatty acids was found in the analogue with walnut oil. The cheese analogues showed the higher antioxidant activity compared to standard cheese. A significantly higher content was found in the analogue with hazelnut oil. Oil addition decreased the sensory evaluation of consistence and flavour of samples. The standard cheese reached the highest score of overal acceptability among samples; the strongest nut flavour was described in the analogue with hazelnut oil. The results showed that the addition of oils increases the nutritional value of cheeses (higher content of unsaturated fatty acids, higher antioxidant activity), but reduces their sensory quality and overall consumer acceptability.
|
|
|
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.
|
|
|
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.
|
guest ::
