Вестник МГТУ. 2019, Т. 22, № 3.

Introduction At present, the issues of storing plant materials are becoming important, especially for food products and medicines. Various raw materials need a certain storage mode depending on the composition of the raw materials, the properties and intensity of the processes occurring in it. Freezing is a conservation method in which the preservation of quality is achieved due to low temperatures that lead to the blocking of redox processes, the reduction of microbiological activity, as well as the activity of free water found in vegetable raw materials by transferring it to crystalline ice. This method of storage allows preserving up to 75-80 % of biologically active substances (BAS) for a long time (Stryukova et al., 2013). The shelf life of frozen foods is measured in months and even years. To date, the processes occurring in brown algae during storage in the freezer and influencing on the content of biologically active substances (BAS) remain poorly understood. Brown algae (Phaeophyceae) are the largest of the known algae, characterized by a huge variety of shapes and sizes. They are a valuable source of various BAS for industry. Brown algae contain a significant amount of pigments, which are usually removed in the production of polysaccharides. However, recent studies have shown the biofunctionality of pigments. For example, fucoxanthin can be used as an antioxidant, chemoprophylactic and chemotherapeutic, reducing fat mass, and also as an anti-inflammatory agent (Indrawati et al., 2015). Chlorophyll a stimulates tissue growth, prevents the spread of bacteria and accelerates the healing process of wounds (Hosikian et al., 2010). In the production of pigment extracts, it is important to take into account that chlorophylls and carotenoids easily decompose when exposed to heat and light, as well as during chemical treatment (acid-base, redox) (Indrawati et al., 2015). Due to their instability, special extraction approaches are required to maximize the release of these pigments from algae. It is necessary to develop a new approach that can be used to create pigment-containing products from commercial and promising species of brown algae, which are still not used in industry. For the production of pigment extracts, it is necessary to investigate the stability of pigments in raw materials during storage as well as in extracts. The purpose of this research is to study the quantitative content of fucoxanthin and chlorophyll a in frozen thalli of Fucus algae of the Barents Sea and extracts from them during storage and heat treatment. Materials and methods Fucus algae at the age of 4+ ... 7+ years of the following species were used in the work: Fucus vesiculosus L., Fucus distichus L., Ascophyllum nodosum L. Algae samples from the southern part of the Teriberskaya Bay in the Zavalishin Bay of the Barents Sea were collected in August 2018 at low tide. Fresh algae were delivered to the laboratory 3 hours after collection, thoroughly cleaned from epiphytes and sand, frozen in a freezer at -25 ± 2 °С. Extraction of pigments was carried out according to the modified method described in our previous works (Gerasimenko et al., 2010; Daurtseva, 2018). Briefly, 3 consecutive extractions with 96 % ethanol with a duration of 5, 10, 10 minutes and then an exhaustive extraction by percolation was made. All extractions were performed at room temperature in a darkened room. To obtain an extract enriched with fucoxanthin, frozen A. nodosum stored for 6 months were used as raw materials. Before extraction, the algae were thawed and crushed on a Redmond grinder (China). Extraction was carried out for 5 minutes, then the extract was filtered and placed in a refrigerator at +4 °C. The total storage time of the extract was 35 days. Then the extract was evaporated to dryness on rotary evaporator IR-1 (Russia) under vacuum at a temperature of 50 °C. To determine the pigment content, the enriched dry extract was dissolved in 96 % ethanol until the original volume was restored. Fucoxanthin content in the extracts was determined on Shimadzu LC-20AD Prominence liquid chromatograph (Japan) with a Shimadzu SPD-M20A Prominence photodiode array detector and Supelco (250 x 4.6, C18, 5 pm) chromatographic column (USA). Methanol : acetonitrile was used as the mobile phase. Selection of chromatographic parameters was carried out experimentally. To assess the purity of the pigment extracts, spectra were obtained in the visible and UV region by spectrophotometry. The spectra were obtained on Nicolett Evolution 500 spectrophotometer by Spectronic Unicam (Great Britain). Fucoxanthin (Sigma-Aldrich) and chlorophyll a (Sigma-Aldrich) were used as standard samples for spectrophotometry and HPLC. Absolutely dry mass of algae samples was determined according to the generally accepted method1. All data were obtained in 3 replicates and processed in the program Statistica. 1 GOST 26185-84. Seaweeds, sea-grasses and its processed products. Methods of physical and chemical analysis. M.,