Ograniczanie wyników

Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 111

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 6 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  storage condition
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 6 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Bee pollen is a product of rich and varied chemical composition, and its biological activities are diverse. Many of these activities are related to the antioxidant effect of bee pollen. The aim of this study was to determine the effect of storage conditions on the antioxidant activity of bee pollen extracts. The study was conducted on three types of bee pollen extracts, namely, ethanol and pepsin extracts of bee pollen, as well as on ethanol extracts of pepsin-digested bee pollen. Antioxidant activity was determined by a DPPH method, directly after obtaining the extracts and after storing them for twelve months under various conditions, i.e. at –18°C in the dark, at 4-8°C in the dark, at room temperature in the dark, and at room temperature in the light. It was concluded that the 12-month storage of bee pollen extracts caused a decrease in the antioxidant activity of all extracts examined, and the decrease depended on storage conditions. The highest decrease in antioxidant activity was observed in all types of extracts stored at room temperature in the light. The lowest decrease in antioxidant activity was found in ethanol extracts of pepsin-digested bee pollen.
Bee pollen belongs to bee products that are characterized by high nutritional value and biotic activity. These characteristics result from the wide variety of compounds that bee pollen contains. Our study determined the effects of storage conditions of bee pollen extracts on polyphenol content. The study was conducted with the use of three types of bee pollen extracts, namely ethanol extracts, enzymatic hydrolysates from pollen, and ethanol extract of pepsin-digested bee pollen. Polyphenol content in the studied extracts was determined immediately after extraction and after 12-month storage. We have concluded that 12- month storage of bee pollen extracts decreases polyphenol concentration in all three types of extracts, and the changes depend on the storage conditions.
The research was carried out in 2002-2006 at the Crop-Growing Product Storage and Processing Laboratory, Department of Horticulture, Lithuanian University of Agriculture Animal Husbandry Institute of Lithuanian Veterinary Academy. 15 amino acids were determined in the studied samples of potato tubers of 5 cultivars including 9 essential amino acids. Essential amino acids make up 38-45% of all the amino acids. In potato tubers, the dominating amino acids were leucine and valine, the lowest amount was of methionine and histidine. Dominating alterable amino acids were glutamic and aspartic acids. The latter were one of the most mobile during the storage period. During the whole period of storage, the lowest changes were observed in the following: lysine in cv. Goda tubers, histidine in cv. Nida tubers, methionine, histidine and isoleucine in potato tubers of the cv. Vaiva. Alterable amino acids, i.e. glycine, alanine and tyrosine, during the whole period of storage changed the least in the potato tubers of all cultivars. The decrease in the protein content during the storage period causes the increase in the tyrosine content. Tyrosine is not desirable in potato tubers due to the fact that it negatively affects the color of raw potato tubers. Under the increasing amount of tyrosine, potatoes darken faster. According to the data of our research, the amount of tyrosine in potato tubers of all cultivars was not significant. After carrying out the correlation analysis between the darkening of raw potato tubers and the amount of tyrosine, a weak correlation was determined (r = -0.4).
The content of antioxidative compounds was evaluated in frozen green asparagus produced with the traditional technology from the material blanched before freezing or with the modified technology from cooked asparagus. Compared with blanched asparagus, the product cooked before freezing contained more dry matter and polyphenols, similar amounts of beta-carotene, less carotenoids and vitamin C and its antioxidative activity was lower. During a 12-month storage at -20°C and -30°C a steady decrease in the level of the analysed constituents was observed in frozen products prepared for consumption. Compared with the raw material, asparagus prepared for consumption after the 12-month period of refrigerated storage contained 56–62% of vitamin C; 55–71% of polyphenols; 73–81% of beta-carotene; 74–89% of carotenoids while its antioxidative activity was reduced to 65–73%. In products obtained using the modified method the level of the analysed constituents was similar or a little higher than in the traditional products. Frozen products stored at -30°C were usually characterised with a higher content of analysed constituents and a higher level of the antioxidative activity in comparison with frozen asparagus stored at -20°C. Sensory quality of traditional frozen products slightly exceeded that of frozen products obtained using the modified method. The quality of products stored at -30°C was also better than that of products stored at -20°C.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 6 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.