Search

The monitoring of physicо-chemical changes in the oleic type of sunflower oil when frying potatoes in restaurant conditions by using a professional MModular fryer at 180 °C and comparison with the use of the linoleic typeof sunflower oil was researched. In the oleic type of sunflower oil, there was a slight increase of the AV (acid value) observed till the second frying, after which there was detention within the limits of 0.15 to 0.20 % till the tenth frying. The peroxide value (PV, mеqО2/kg) increased significantly in both types of oil - oleic and linoleic, reaching the maximum at the fourth frying, and the value was close to the limiting value for vegetable oils from the linoleic type of sunflower oil - 10 mеqО2/kg. The induction period in the oleic type of sunflower oil was long - 22 hours, but it gradually decreased and after the tenth frying, it was 5 hours. In the linoleic type of sunflower oil, the induction period in the beginningwas 8.55 hours, and after the fourth frying, it decreased to 4 hours. The color numbers according to Lovibondon 10 oil samples from repeated frying of products were determined and this indicator increased with the number of fryings over time. Chlorophyll content was not been established. Theoleic type of sunflower oil produced in Bulgaria, when frying fresh potatoes, was more stable to the oxidation than the traditionally used sunflower oil - linoleic type. Itshowedstability during storage and long frying time of the used products in real working conditions. This made it more suitable for the preparation of food products, culinary items, main courses, starters and garnishes that require longer thermal treatment. This type of product can be recommended for use when frying in the restaurant business and in the area of nutrition. The methods in our research can be used to control the degree of oxidation of frying oils with vegetable origin in their repeated use, by taking samples on the first, fourth and tenth day of frying at different loads of fryers and to test for acidity, peroxide number and color number. [ABSTRACT FROM AUTHOR]

Importance of the study of the influence of coal oxidability on vitrinite reflectance (VR) as a criterion of the quality of coals and indicator of paleogeothermal regime is shown. Overview of relevant concepts demonstrates that this issue remains debatable. Carboniferous coals of the Dobrudja foredeep, which belong to the class of helitolites in terms of their microcomponent composition, were studied. They were subjected to oxidation during storage outdoors. Consequently, the VR value of high volatile bituminous (long-flame and gas ranks, according to the Russian classification) coals decreased, but this parameter remained virtually unaltered for medium volatile bituminous (fat) coals. Bulgarian researchers obtained similar results for Carboniferous coals of the Dobrudja basin represented by helitolites and mixtohumolites. In our opinion, the VR decrease in the course of coal oxidation is caused by decrease in the condensation and density of aromatic structures and increase in the share of nonaromatic carbon atoms. [ABSTRACT FROM AUTHOR]