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The influence of various storage conditions on the stability of anthocyanins in blueberries (Vaccinium myrtillus L.)
Martanová, Anna ; Kotíková, Zora (advisor) ; Petr, Petr (referee)
This diploma thesis deals with the influence of different storage methods on the stability of anthocyanins in the fruits of blueberries. The theoretical part describes blueberry (Vaccinium myrtillus L.), anthocyanin pigments and their stability based on the studied literature. Moreover, an overview of the most common methods for their determination in plant materials is given. The methodical part depicts the methods of determining the content and the extent of the degradation of anthocyanins in blueberries using the different ways of storage. Anthocyanin dyes contained in the blueberries were subjected to acid hydrolysis and their content was expressed in the form of free aglycones (anthocyanidins). During the initial analysis, the measurement of the content of anthocyanidins in the fresh blueberries was done. Furthermore, a sample preparation was carried out applying the different storage methods. Three storage variants were tested, dried samples at 80 ° C, lyophilized and frozen samples. During the eight-month storage, five further measuring of the degradation rate of anthocyanins in time was performed. All samples were analyzed in triplicates. A mass spectrometer 3200 QTRAP with triple quadrupole and ESI ionization, coupled with a liquid chromatograph, type UHPLC was used for the analysis. Afterward, the values were averaged and presented using graphs and tables. The results of the thesis pointed out that the least intrusive variant of preserving the sample was lyophilisation, especially than for the first two months of storage. The amount of the anthocyanins did not changed during this period. Moreover, also the freezing variant was a suitable method for preserving the sample. Freezing was assessed as the favorable method for preserving the sample for longer periods since the value has decreased in the relation to time more gradually and during the final collection have shown higher values than the variant of the lyophilized blueberries. The variant of dried blueberries was the least stable compared to the previous variants. The rapid decline of anthocyanins occurred already during drying, depending on the time the values continued to decline In the variant of drying, petunidin was evaluated as the most stable anthocyanidin, while kyanidin and delphinidin were determined as the least stable. Delphinidin was determined to be the most stable anthocyanin in the variant of both freezing and lyophilization whilst the least stable the anthocyanins were petunidin in the variant of freezing and cyanidin in the variant of lyophilization.
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Effect of drought stress factor on glycoalkaloid contents in potato (Solanum tuberosum L.)
Matoušková, Vendula ; Kotíková, Zora (advisor) ; Martinková, Jaroslava (referee)
Potatoes are an important and irreplaceable crop. This kind of crop is very important not only for it is use but also for a nutrition composition. There are also a prominent source of vitamins, minerals and antioxidants. Outside substances beneficial to health and potatoes contain harmful substances. These substances are foreign or naturally occurring, which include toxic glycoalkaloids. Glycoalkaloids are secondary metabolites of plants. Glycoalkaloids in potatoes have protective function it can increase the synthesis for example in case of pest infestations, mechanical damage or in case of to much light and heat. The potatoes were found several glycoalkaloides. Main, which constitutes 95 % of their content, are alpha-chaconine and alpha-solanine. Their toxicity is inhibition of acetylcholinesterase and breaking the cell membranes. The potato tuber is their content is distributed unevenly. The quantity of glycoalkaloids is affected by manny factors as for example place, year, kind, the way how the crops are grown and storage. In Czech Republic the maximum allowed limit of glycoalkaloides in potatoes were made by legislation on 200 mg/kg fresh potato matter. In the commonly grown varieties of the amount is far below the hygienic limit. The methods for isolation of glycoalkaloids in potatoes are mainly chromatographic. The most commonly used HPLC (high performance liquid chromatography). In performed experiment was determined the content of majority glycoalkaloid alpha- chaconinu and alpha-solaninu at four different kinds -Milva, Marabel, Laura and Valfi. Drought stress has been studied for their content, assuming their accumulation in comparison with the other two variants - irrigation watering and drip irrigation. The glycoalkaloides content were messured by the UHPLC/MS/MS. The obtained results concluded that the content of glycoalkaloids is the variety dependent. Drought stress can probably increase their content. In our experiment, it positively did not. Important is the choice of kind in case if expectation a hot and dry year of growing. Kinds Milva and Marabel are very good in these conditions. In the case of general principles for cultivation, storage and cooking, the glykoalkaloids does not vision a risk for the consumer.
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