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Monitoring of oxidative stability of products from shell fruits
Krňávková, Martina ; Hrstka, Miroslav (referee) ; Vítová, Eva (advisor)
The diploma thesis deals with the monitoring of oxidative stability of products, oils and butter, from nut fruits. The theoretical part concentrates on the topic of nut fruits, their properties, compositions which are closely related to the effects on the human health and the possibilities of technological processing. The lipid storage process, especially the most frequently occurring autooxidation reactions are described, followed by experimental part of the thesis. The changes in coconut, walnut, peanut oils and peanut butter samples are monitored during storage at 4 ° C and 20 ° C by determining the acid value, the peroxide value and the fatty acid composition by the GC-FID method. The lowest oxidation stability showed walnut oil due to the highest content of unstable polyunsaturated fatty acids – up to 88,7 %. During storage at 20 ° C there was a statistically significant increase in the content of primary oxidation products, determined as peroxide value PV = 2,55 ± 0,12 µgROOHg-1. An increase was also observed in samples of peanut butter, but it was mainly due to higher water activity, which is important for chemical reactions. The durability of this product after opening mentioned on the product label correlates with their low stability
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Stability of natural oils used in cosmetics and pharmaceuticals
Milerová, Helena ; Enev, Vojtěch (referee) ; Hurčíková, Andrea (advisor)
The bachelor's thesis deals with the issue of stability of selected plant oils used in the cosmetic industry. Six oils were subjected to analysis using differential scanning calorimetry (DSC), which determined the oxidation onset temperatures for all samples. The aim of the thesis is to evaluate the use of the DSC method for obtaining data on the thermo-oxidative stability of plant oils. For comparison, the samples were also measured using the Rancimat method, a commercially established procedure in which the samples were exposed to elevated temperature using air flow. The results yielded induction periods, which indicate the time until the sample starts to oxidize. After measuring the samples using both methods, the oils were ranked according to their oxidative stability from the most stable to the least stable. The resulting sequences from both methods were nearly identical. DSC has proven to be a suitable method for measuring the thermo-oxidative stability of plant oils.
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Monitoring of oxidative stability of products from shell fruits
Krňávková, Martina ; Hrstka, Miroslav (referee) ; Vítová, Eva (advisor)
The diploma thesis deals with the monitoring of oxidative stability of products, oils and butter, from nut fruits. The theoretical part concentrates on the topic of nut fruits, their properties, compositions which are closely related to the effects on the human health and the possibilities of technological processing. The lipid storage process, especially the most frequently occurring autooxidation reactions are described, followed by experimental part of the thesis. The changes in coconut, walnut, peanut oils and peanut butter samples are monitored during storage at 4 ° C and 20 ° C by determining the acid value, the peroxide value and the fatty acid composition by the GC-FID method. The lowest oxidation stability showed walnut oil due to the highest content of unstable polyunsaturated fatty acids – up to 88,7 %. During storage at 20 ° C there was a statistically significant increase in the content of primary oxidation products, determined as peroxide value PV = 2,55 ± 0,12 µgROOHg-1. An increase was also observed in samples of peanut butter, but it was mainly due to higher water activity, which is important for chemical reactions. The durability of this product after opening mentioned on the product label correlates with their low stability
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Monitoring of the backfat oxidative stability in relation to the source of unsaturated fatty acids in the feeding ration
Bezděková, Pavla ; Okrouhlá, Monika (advisor) ; Michaela, Michaela (referee)
Summary
Pork is composed of 46 - 49 % of monounsaturated fatty acids, 40 % saturated fatty acids and 8 - 12 % of polyunsaturated fatty acids. The composition of fatty acids affects the strength of the tissues, their shelf life and quality (mainly taste). The development of fat tissues is characterized by hyperplasia and hypertrophy of fat cells. The quality of the adipose tissue associated with fatty acids.
Monitored was 72 animals (36 of these pigs and 36 gilts). Pigs were divided into 2 experimental groups with 4 % addition of oil (rapeseed, soybean) and one control group, which was without the addition of oil. The animals were fed ad libitum complete feed mixtures, and for the whole period of fattening. In the control and experimental groups were used to compound feed for before fattening (P1) and fattening (P2). The pigs, which were in the experimental groups, was added to the feed mixture P2 oil (rapeseed or soybean), and 6 weeks before slaughter. In each group was assessed in 6 animals. Sampling was conducted from the backfat samples were homogenized and subjected to chemical analysis for the determination of fatty acids and oxidative stability.
From the measurement results, it was found that rapeseed oil contained a fatty acids SFA, MUFA, n-3 PUFAs and higher ratios of S/P, M/P. Compared to the soybean oil contained more PUFA, n-6 PUFA, n-6/n-3 and M/P. In gilts was higher proportion of SFA in the fat of soybean oil and pigs to have more SFA from the oil of rapeseed.
Oxidative stability of backfat increased tendences. Pigs had a higher oxidative stability of the fat in rapeseed oil compared to soybean, and gilts had higher values of oxidative stability of the fat in soybean oil. The measured values in the control group were lower in the oxidative stability of 0 compared to oils (rapeseed, soybean), but in the oxidative stability of 3 and 5 days were the highest.
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