2018, Vol. 16, Special Issue 2

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/5381

Sirvi

Nüüd näidatakse 1 - 20 27

Single cell protein production from waste biomass: review of various agricultural by-products
(2018) Spalvins, K.; Ivanovs, K.; Blumberga, D.
Agricultural waste constitutes for most of the manmade waste streams. Processing of biodegradable waste materials ensures the treatment of harmful substances and allows to reduce environmental pollution. In addition, conversion of these waste materials in value - added products makes these recycling methods more economically viable. Single - cell protein is one of the value - added products that can be produced by microbial fermentation of waste materials. In this review various biodegradable agricultural by - prod ucts as substrates for production of SCP are categorized and compared.
Flavonoids and total phenolic content in extruded buckwheat products with sweet and salty taste
(2018) Krumina–Zemture, G.; Beitane, I.; Cinkmanis, I.
The aim of research was to evaluate the effect of added ingredients used for taste improvement on flavonoids and total phenolic c ontent in extruded buckwheat products. The added ingredients were – sugar, vanilla sugar, stevia, agave syrup, cinnamon, caraway, garlic powder, sweet pepper powder and salt. Six extruded buckwheat products were analysed, where an extruded buckwheat produc t without added ingredients was a control sample, two extruded buckwheat products were with sweet taste and three products with salty taste. Total phenolic content was determined using the modified Folin – Ciocalteu method but flavonoid content according to LC - TOF - MS method. The highest total phenolic content (p < 0.05) was determined in extruded buckwheat product with vanilla sugar + stevia (91.17 ± 0.67 GAE mg 100g - 1 DW). It was almost three times higher than in the control sample. The significant difference s were observed in extruded buckwheat products with caraway + salt + agave syrup (41.5 ± 0.12 GAE mg 100g - 1 DW) and sweet pepper powder + salt + agave syrup (42.39 ± 0.80 GAE mg 100g - 1 DW) comparing to other extruded products (p < 0.05). The highest content of rutin and quercetin (p < 0.05) was established in extruded buckwheat product with garlic powder + salt + agave syrup, whereas the highest content of catechin and epicatechin – in extruded buckwheat product with vanilla sugar + stevia. The extruded buckw heat product with caraway + salt + agave syrup in addition contained luteolin, kaempferol and isoquercitrin. The results of research showed that some added ingredients used for taste improvement can significantly influence the total phenolic content and fl avonoid content.
Meat chemical composition of pasture pure lambs and crossbreeds
(2018) Vecvagars, J.; Bārzdiņa, D.; Kairiša, D.
Increased customer interest of safe, healthy and environmentally friendly food consumption promote development of sheep farming industry in Latvia. Aim of the paper – explain of different pasture - fattened sheep breed and their crosses lamb meat composition traits. A study of pasture fattened lamb meat chemical composition was carried out from year 2013 to 2017. Fattening lambs were kept in breeding rams control station ‘Klimpas’ (57°50’58.8’’N 25°19’39.6’’E) pasture array. Lambs were slaughtered in a certif ied slaughterhouse, but analysis of meat chemical composition were conducted in laboratory of Institute of Food Safety, Animal Health and Environment (BIOR). For the analysis of the meat chemical composition were used up to 1 kg heavy Quadriceps femoris mu scle samples. In meat were analysed following elements of its chemical composition: dry matter, protein, fat, minerals, pH, cholesterol and unsaturated fatty acids. Data analysis shows that the lambs before slaughter ranged in age from 5 to 8 months. Lamb meat obtained from the study groups had a significantly different total amount of dry matter and fat. The lowest total fat, but the highest ash content was obtained in the lamb meat of the extensive breed group. The lowest total fat and the highest ash con tent were obtained in the lamb meat from the extensive breed group. In meat obtained a small (in individual samples < 0.10%) cis - 10 - pentadecenoic acid, cis - 11 - eicosenoic acid and myristoleic acid content. Of unsaturated fatty acids in lamb meat were represented higher amount of oleic acid, linoleic acid and elaidic acid.
Changes in the nutritional value of breakfast cereals containing germinated spring grain flakes during storage
(2018) Kruma, Z.; Galoburda, R.; Tomsone, L.; Gramatina, I.; Senhofa, S.; Straumite, E.; Klava, D.; Kince, T.; Cinkmanis, I.; Zagorska, J.; Kunkulberga, D.
Th e aim of current research was to assess the nutritional value of breakfast cereals containing germinated spring grain flakes and its changes after 6 month storage. Three types of breakfast cereals were prepared and packaged in two types of Standup pouches – Pap50g/Alu7/Pe60 (AL), Pap40g/PELD20/PE40 (PE). For the accelerated shelf life test the samples were stored at 35 ± 2 °C and dietary fibre, protein, fat, B - group vitamins, sugars, total phenol content and DPPH, ABTS+ radical scavenging activity were dete rmined. Developed breakfast cereals have high nutritional value and all are high in fibre and thiamine. Additionally, sample S2 is source of protein, riboflavin, niacin, and S3 – is source of riboflavin and high in niacin. Comparing total phenolic content and antioxidant capacity of tested samples S3 showed the highest values. Storage and selected packaging influenced stability of nutrients, and for S1 and S2 AL showed bett er results whereas for S3 – PE.
Study of potential PCR inhibitors in drinking water for Escherichia coli identification
(2018) Dalecka, B.; Mezule, L.
In the last few decades, the polymerase chain reaction (PCR) has become one of the most powerful molecular biological tools. However, the PCR is an enzymatic reaction and therefore sensitive to inhibitors which may occur in drinking water samples. In this work, the possible inhibition effect of chlorine, humic acids, and iron for real - time PCR (qPCR) efficiency was studied and the environmental sample from drinking water treatment system before iron removal was selected and analysed. The results demonstrate d that the highest concentrations of humic acids (5 mg L - 1 and 1 mg L - 1 ) and iron (4 mg L - 1 ) inhibited the PCR reaction while no effect of chlorine was observed. The analysis of the environmental sample with spiked Escherichia coli cells demonstrated reduc tion efficiency of the average threshold cycle (C t ) values compared with control dilution series determining the possible inhibition for qPCR assay.
Shrinkage effect on diffusion coefficient during carrot drying
(2018) Aboltins, A.; Rubina, T.; Palabinskis, J.
Many studies have been previously carried out on the carrot drying and the undergoing processes. The developed mathematical models provide an opportunity to gain an understanding of this complex process and its dynamics. But they are sim plified and based on a number of assumptions, including calculation of diffusion coefficient values. In one of the previous studies, the authors of this study determined that the diffusion coefficient is linearly dependent on the moisture concentration wit h the assumption that the sample's geometric shape does not change. The aim of this study is to determine the dependence of the diffusion coefficient on the moisture concentration taking into account the change in sample thickness during the drying experim ent. The experiments were carried out with carrot slices of three different thicknesses: 5 mm, 10 mm and 15 mm thickness on the film infrared dryer at temperature 40 °C . During the experiments, measurements of the weight and thickness of the slices were pe rformed. Using the experimental data the average thickness and diffusion coefficient of slices was calculated depending on the moisture concentration . Obtained results show that thickness depends linearly on the moisture concentration. Using experimental d ata and obtained average values of samples thickness, the values of diffusion coefficient was calculated. The results indicate that diffusion coefficient value depend linearly on moisture concentration. Their values are close and tend to zero when the conc entration decreases if the thickness changes are taken into account during the experiment.
Effect of germination and extrusion on the phenolic content and antioxidant activity of raw buckwheat (Fagopyrum esculentum Moench)
(2018) Beitane, I.; Krumina–Zemture, G.; Sabovics, M.
The aim of the research was to determine the total phenolic content, antioxidant activity and phenolic compounds in raw and germinated common buckwheat grain and their extruded products in order to estimate the effect of germination and extrusion on the total phenolic content, antioxidant activity and phenolic compounds in buckwheat. A total of 10 buckwheat samples were analysed, where the raw buckwheat grain was the control sample, four samples were germinated and then extruded. The total phenolic content was determined using the Folin– Ciocalteu assay. The antioxidant activity was determined using a micro plate assay and phenolic compounds with Liquid Chromatography –Time of Flight Mass Spectrometer method. The results showed that germination of buckwheat significantly affected the total phenolic content, antioxidant activity, radical scavenging activity and content of phenolic compounds. The decrease of the total phenolic content, antioxidant activity, radical scavenging activity and the content of some phenolic compounds depended on germination time – 48 h of germination provided greater concentrations at the end of a 24 h germination period, whereas the content of some phenolic compounds like rutin, quercetin and vitexin increased substantially after germination, besides, the increase of phenolic compounds depended on the germination time. In total 26 different phenolic compounds were detected in raw and germinated buckwheat samples and only one compound with an m/z value 385.1282 was unidentified. The data of extrusion revealed a significant decrease of total phenolic content, antioxidant activity, radical scavenging activity and phenolic compounds content in buckwheat samples (P < 0.05). In the extruded buckwheat samples novel phenolic compounds like 4–hydroxybenzoic acid, homovanillic acid, catechin, ferulic acid, and hyperoside were detected.
Effect of impact-activating-disintegration treatment on grain protein fraction of autumn rye
(2018) Sabirov, А.А.; Barakova, N.V.; Samodelkin, Е.А.
This paper studies the distribution of rye protein fractions according to their mass and amino acid composition while milling by machines with different work tools. The research was conducted on the autumn rye of harvest year 2017 with kernel moisture con tent of 8%. Cereals were milled in the machine of an impact - activating - disintegrating type DEZI - 15 with three - row and five - row rotors which rotate at 120 s - 1 , and in the laboratory mill with a knife - rotor work tool. The milling grain size was determined by a diffraction - type grain analyser Malvern Mastersizer 2000. The average grain size obtained from three - row disintegrating rotor was 167 μm , from the five - row rotor 158.1 μm , and from the laboratory knife - rotor mill 384 μm , respectively. The free amino aci ds composition in flour samples was investigated using the size exclusion chromatography method (SEC - method). The polypeptide composition of total grain protein has been determined by One - dimensional SDS - acrylamide gel electrophoresis. According to the ele ctropherogram results obtained from all the the content of high - protein fraction of 200 kDa . The glutelin fraction with molecular weight of 116.25 kDa is definitely observed in the sample obtained from the three - row disintegrating rotor. Whereby the lowest glutelin content has been detected in the flour sample obtained from the five - row disintegrating rotor. Fractions with molecular weight of 60 – 75 kDa – globulin fractions – come up frequently in the sample obtained from the three - row disintegrating rotor. Prolamine fractions of 45 – 47 kDa are clearly observed in the flour sample obtained from the laboratory knife - rotor mill. The albumin fraction with molecular weight of 17 – 28 kDa are mostly observed in the samples obtained by three - row and five - row disintegr ating rotors. Few LMW fractions (from 6.5 to 15 kDa ) are found in samples obtained using the impact - activating - disintegrating technique, mostly in the sample milled in the laboratory knife - rotor mill. Based on the data of free amino acid content in sample investigated it can be concluded that the impact - activating - disintegrating techniques does not cause reduction in protein biological value. The albumin rich flour milled in the disintegrator can be used for production of functional food. Due to the low con tent of glutelin protein fraction the flour obtained from the five - row disintegrating rotor offers the greatest promise for production of gluten - free foods.
3D image analysis of the shapes and dimensions of several tropical fruits
(2018) Herak, D.; Mizera, C.; Hrabe, P.; Kabutey, A.
T hree dimension virtual models of Avocado ( Persea americana ) , Salak ( Salacca zalacca ) , Dragon fruit ( Hylocereus undatus ) , Mango ( Mangifera indica ) , Coconut ( Cocos nucifera ) using 3D scanner Intel RealSense were determined. C alculated models based on arithmetic and geometric diameter were also determined. From statistically analysis implies that virtual models on significance level 0 .05 are significantly different with calculated values based on arithmetic or geometric diameter.
Contents of tocols in different types of dry shell fruits
(2018) Hejtmánková, A .; Táborský, J.; Kudelová, V.; Kratochvílová, K.
The aim of this study was to identify all forms of vitamin E in different kinds of dry shell fruits (generally called ‘ nuts ’ ) obtained from different sources and to perform their mutual comparison . All tocols were determined by reversed phase HPLC using is ocratic elution with fluorescence detection. Almonds were evaluated as the most important source of α - tocopherol (average value 1 , 132 mg kg - 1 ), β - tocopherol was present in all samples as a minor component, its maximum content was found in hazelnuts (9.6 mg kg - 1 ). γ - T ocopherol was found in all kinds of nuts and the highest content was found in pistachios (584 mg kg - 1 ), very high amount of δ - tocopherol was contained in Brazil nuts (2 , 29 8 mg kg - 1 ). Tocotrienols were found in a smaller number of nut kinds than tocopherols. α - Tocotrienol was found only in three kinds of nuts - Brazil nuts, which contained the highest amount (399 mg kg - 1 ), pine nuts and hazelnuts grown in the Czech Republic, which were analyzed soon after harvest. Similarly, γ - tocotrienol w as det ermined only in four kinds of nuts (pistachios, macadamias, cashew and walnuts grown in the Czech Republic ) , which were analyzed soon after harvest ; t he most significant amount was found in pistachios (34.8 mg kg - 1 ) , β - and γ - tocotrienols were below the detection limit . In the Czech Republic, walnuts and hazelnuts are the most widely cultivated and consumed nuts. While in walnuts the most important form is γ - tocopherol (459 ± 40 mg kg - 1 ), in hazelnuts it is α - tocopherol ( 863 ± 10 mg kg - 1 ).
Sonochemical effects on food emulsions
(2018) Krasulya, O.; Potoroko, I.; Tsirulnichenko, L.; Khmelev, S.; Bogush, V.; Anandan, S.
Acoustic cavitation of food emulsions is widely applied as the main processing method to improve the quality of a finished product and its organoleptic characteristics, as well as to increase production performance. To identify the optimal modes of ultrasonic emulsification, we propose a model of emulsion droplet breakup in an acoustic cavitation field, which allows us to determine the dependence of emulsion droplets’ diameter on exposure time and intensity of action. The developed models enabled us to pioneer complex research of the dependence of emulsion droplets’ diameter on time given the maximum radius of cavitation bubbles and physical properties of liquid phases in the emulsion composition. We carried out the fi rst complex theoretical and practical research of how shapes and positions of absolutely fixed boundaries influence the propagation of oscillations in a activating liquid medium (food emulsion). To verify the adequacy of the obtained theoretical models, we studied the dependence of emulsion droplets’ breakup rate (by the example of a model water/oil emulsion) on the exposure time and the intensity of ultrasonic action. The calculation results revealed that the results of a series of experiments and the resu lts obtained with the use of the developed mathematical model are consistent. Based on the theoretical data obtained, we designed an industrial flow - type acoustic cavitation device aimed at acting on food emulsions; it differs from analogous devices in th at it has within it a cylindrical wave acting through solid walls of the tunnel for transmitting processed liquid.
Optimisation of biologically active compounds ultrasound assisted extraction from potatoes using response surface methodology
(2018) Zarins, R.; Kruma, Z.; Skrabule, I.
Potato ( Solanum tuberosum L.) is source of p henolic compounds and from plant matrixes can be extracted by several methods. In recent years ultrasound assisted extraction has become more popular due to its efficiency for recovery of phenolic compounds and antioxidants and response surface methodology is an effective tool for optimisation of extraction procedure by evaluating different variables and their interaction. The aim of the current research was to optimize ultrasound assisted extraction of biologically active compounds from potatoes by respons e surface methodology. For experiment purple - flesh potato variety ‘Blue Congo’ was selected. Control sample was extracted by stirring for 1 hour. Box - Behnken design was used for optimization of extraction conditions from fresh potatoes and as variables wer e selected: ethanol concentration (% v/v), hydrochloric acid concentration (molarity) and time (min). For extracts as responses total phenolic, total flavonoid, total anthocyanin content and antioxidant activity (DPPH, ABTS+ scavenging activity) were deter mined using a spectrophotometric methods. Significant models were obtained for antocyanins, total phenols and DPPH radical scavenging activity. Optimisation of extraction showed that for maximising all responses optimal HCl concentration is 2.5M, ethanol c oncentration 79.4% and extraction time 60 minutes, resulting in following responses: 57.41 mg 100 g - 1 of anthocyanins, 238.52 mg 100 g - 1 of TPC, 24.58 mM TE 100 g - 1 of DPPH scavenging activity and 12.99 mM TE 100 g - 1 of ABTS scavenging activity. Convention al extraction method showed significantly lower results. It could be concluded that ultrasound assisted extraction is effective method for recovery of phenolic compounds and solvents and extraction time is significant parameter influencing efficiency.
Production and investigations of antioxidant rich beverage: utilizing Monascus purpureus IHEM LY2014 - 0696 and various malts
(2018) Adadi, P.; Kovaleva, E.G.; Glukhareva, T.V.; Barakova, N.V.
Antioxidant evokes numerous health benefits to the consumer as well as stabilisation of the beverages flavours. Therefore, this paper provides detailed information on the application of Monascus purpureus IHEM LY2014 - 0696 in combination with vario us malts in brewing antioxidant rich beverage (ARB). Starter culture Angkak was prepared by solid state bioprocessing (SSB). Single infusion method of mashing was used. Physicochemical parameters, volatile compounds, DPPH (2, 2 - diphenyl - 1 - picrylhydrazyl) r adical scavenging activity and fermentability of the wort were evaluated. Distillation procedure based on pycnometry technique was use to quantify the alcohol content (%ABV). Fermentability of the wort was found to be 97.6 ± 0.46% whilst %ABV was equal to 5.42 ± 0.03 . It was observed that ARB showed a strong DPPH radical scavenging activity of 1.00 × 10 – 4 mol × equ (R 2 = 0.91) whereas 3.43 × 10 - 5 mol × equ (R 2 = 0.81) for wort. The strong antioxidant activity (AOA) is thought to be caused by pigments produced by M. purpureus IHEM LY2014 - 0696 and other compounds originated from the malts and hops utilised in brewing ARB. A total of 4 volatile compounds were identified in the present study. Incidence of microbial load ranged from 2.14 ± 0.04 × 10 7 and 0.8 ± 0.1 × 10 5 for M. purpureus IHEM LY2014 - 0696 and bacterial respectively was observed in the ARB. This study contradicts some previous ones, as the ARB brewed did not take the red pigment produced by the M. purpureus . Panellists generally ex pressed their acceptance for the ARB as they assessed it as a new product, moreover, taking account its health benefits.
A study of commercial β-galactosidase stability under simulated in vitro gastric conditions
(2018) Žolnere, K.; Ciproviča, I.; Ķirse, A.; Cinkmanis, I.
β-Galactosidase activity in milk may be affected by several factors, such as temperature, pH, milk composition, and metal ions. It is important to note that digestive proteases and gastrointestinal pH can affect enzyme activity during transit through the gastrointestinal tract. For the investigation of commercial β - galactosidase stability in human and animal gastric tracts, human gastrointestinal tract (GIT) models were employed, enabling prediction of enzyme activity under in vivo conditions. The aim of this study was to analyse and compare commercial β - galactosidase stability under simulated in vitro gastric conditions. Commercial enzymes (Ha Lactase 5200 produced by Kluyveromyces lactis and NOLA™Fit5500 produced by Bifidobacterium bifidum expressed in Bacillus lichenifo rmis , Chr. Hansen, Hørsholm, Denmark; GODO - YNL2 produced by Kluyveromyces lactis , Danisco, Copenhagen, Denmark) were used for this study. Commercial enzymes were added to GIT models at 1 and 5 mL L – 1 . The enzyme activity was assessed as the percentage of l actose hydrolysis by the enzymes from Kluyveromyces lactis and Bacillus licheniformis using HPLC after digestion. β - Galactosidase extracted from yeast ( Kluyveromyces lactis ) and bacteria ( Bacillus licheniformis ) was found to be effective as a strategy for improving lactose tolerance.
Encapsulation of Gallic acid in solid lipid core surrounded with maltodextrin shell
(2018) Sepelevs, I.; Reineccius, G.A.
Multiple phase capsules had been prepared in a single spray drying process. The main goal of the present study was to investigate whether the conversion of a portion of the modified starch (wall material used in spray drying) to resistant starch (RS) would offer added protection of encapsulated material. To achieve this, dry gallic acid (GA; a model water soluble phenol compound used in the present study) was initially dispersed in palm oil and stabilized with Polyglycerol Polyricinoleate (PGPR 4175) as an emulsifier. This dispersion was homogenized with a modified starch (MS, dextrose equivalent of 15) solution, that was previously treated with high pressure and increased temperature to achieve starch retrogradation, and then spray dried. It was possible to produce only small amounts of RS from modified starch, varying from 0.1 to 0.2% of total carbohydrate content. GA content in the lipid phase of the capsule was determined by lipid droplet size in the O/W emulsion (the feeding solution), as smaller droplet s results in the significantly bigger surface area, and more intensive GA diffusion from O to W phase. Maltodextrin shell wall was able to prevent leaking of the melted palm oil form the capsule core to the surface during seating tests, preventing agglomer ation of capsules. This could be very important for the storage/transportation of capsules in the uncontrolled temperature conditions.
The development of gluten - free sourdough bread technology with rowan powder
(2018) Dubrovskaya, N.; Savkina, O.; Kuznetsova, L.; Parakhina, O.
A new form of technology was developed which focussed on gluten - free bread with gluten - free sourdough and rowan powder (from the botanical species Sorbus aucuparia ). This new form of technology allows organoleptic characteristics to be improved, along wit h structure, texture, microbial spoilage resistance, and the shelf life of gluten - free bread. The gluten - free dry microbial composition with lactic acid bacteria was developed as a starter for sourdough. The lactic acid bacteria, L. brevis E38 , was experim entally selected for dry microbial composition on the basis of its antagonistic activity against ropy bread disease pathogens ( B. subtilis and B. licheniformis ). The dependence was revealed of the accumulation of acetic acid and lactic acid in the sourdoug h on the microbial composition during fermentation. A gluten - free sourdough technology was developed which involved a new starter, rice, and soy flour at a ratio of 0.2:2:1. It was shown that the use of soy protein slows down the fermentation process in th e sourdough. An increase – in acidity levels of between 7.5 – 9.5 times higher in the dough with sourdough and rowan powder when compared to dough without sourdough. Sourdough usage allowed compressibility of the crumb to be increased by between 1.8 – 2 times, with a specific volume of 19.0% and a porosity of 9.8% and 11.5%, and for the sensory characteristics to be improved as perceived by consumers. It was proved that microbial composition with a lactic acid bacteria, L. brevis E38 , inhibits ropy disease and mould development in bread. The results of the present study showed that the addition of sourdough and rowan powder can be used to improve the quality of gluten - free bread.
Comparison of power consumption of a two-roll mill and a disc mill
(2018) Smejtkova, A.; Vaculik, P.
Grinding or milling is often used process, for example in the production of feed, grinding of malt in beer production, grinding of cereals on flour, etc. In order to optimize the energy intensity of the whole production process, it is necessary to know the energy consumption of individual processes. The grinding of malt influences the mashing process, the drawing-off and the boiling yield. Correct grain grinding makes the endosperm available for enzyme and physicochemical reactions during wort production. Husks affect the drawing-off process. Two-, four- or six-roll mills, in some cases a hammer mill or disc mill, are most commonly used for grinding of malt. Power consumption was monitored when light, Munich, caramel and coloring malt were grinding. A two-roll mill and a disc mill with engine speeds of 1,500 rpm and 2,800 rpm were used for grinding. The gap between the mill rollers and the mill disks was set to 0.4 mm. The fineness of the grinding was evaluated for all types of malt on all used equipment. The energy intensity of the grinding was correlated on 1.0 kg of malt and then compared.
A study of dynamics of bitter acids and xanthohumol in hop pellets during storage
(2018) Táborský, J.; Hejtmánková, A.; Hlavatá, E.; Chládek, L.
Eight varieties of hop pellets were analyzed for the contents of α - acids, ß - acids and xanthohumol according to the EBC 7.7 analytical method. The pellets were extracted with acidified mixture methanol - diethylether and analyzed using HPLC with a diode - array detector and a Nova - Pak column C 18 . Four series of analyses were performed: immediately after the unpacking of the pellets and then after five, seven and nine months of storage at 4 °C. According to the first ser i es of analyses, the contents were assayed as following (α - acids, ß - acids, xanthohumol resp., all in weight % in pellets): Galaxy (13.4, 8.0, 0.74), Citra (11.1, 3.0, 0.48), Tradition (8.2, 8.0, 0.58), Cascade (4.5, 5.2, 0.25), Northern Brewer (4.0, 2.9, 0. 37), Sládek (3.5, 4.0, 0.48), Saaz (2.0, 3.4, 0.24), and Triskel (1.7, 3.6, 0.18). According to these results, variety Galaxy was found as the richest in all three parameters. After nine months of storage at 4 °C, the weight loss of α - acids ranged from 4.1 % (Citra and Triskel) to 66.4% (Galaxy). The losses of β - acids and xanthohumol were less distinctive (from zero to 31.3% and 25.7%, resp.) and indicated good long storage possibilities of these compounds at convenient conditions (darkness, low temperature, elimination of direct influence of oxygen).
Bioactive compounds in herbal infusions
(2018) Augšpole, I.; Dūma, M.; Ozola, B.
Herbal teas are very popular and known as important source of biologically active compounds. Some of popular Latvian herbal teas: Calendula (Calendula officinalis L.), Matricaria chamomilla (Matricaria chamomilla), Lady's-mantle (Alchemilla vulgaris L.), Jasmine (Jasminum officinale L.), Yarrow (Achillea millefolium L.) and Linden flowers (Tilia spp.) were selected for analysis. This study was carried out with the aim to investigate the effect of extraction time (10, 15, 20 min) on the content of total flavonoids and total phenols as well as antioxidant activity of herbal tea extracts. The infusions were prepared by usual domestic preparation technique using ground air-dried plant materials and boiling deionized water (0.055 µS cm-1 ) for extraction. Content of total flavonoids, total phenols and antioxidant activity was determined spectrophotometrically. Dry matter content was determined in lyophilized herbal infusions. The obtained results indicated that extraction time did not affected the content of biologically active compounds in the herbal infusions significantly (P > 0.05). The highest level of flavonoids was found in Jasmine and Lady's-mantle infusions (average 104.98 ± 9.21 mg quercetin equivalent 100 g -1 and 115.28 ± 5.25 QE mg 100 g -1 respectivelly), while the lowest was determined in Matricaria chamomilla extract – (average 70.10 ± 4.68 QE mg 100 g -1 ). Lady's-mantle tea contained the largest amount of total phenols (average 4126.62 ± 26.24 mg gallic acid equivalents 100g-1 ), the lowest – Calendula tea 1828.04 ± 10.37 mg GAE 100 g -1 ). Data analysis showed a close linear positive correlation between the content of total flavonoids and total phenols in herbal infusions (R2 = 0.872; r = 0.934) with the probability of 99%. In general, all samples tested in this study, demonstrated high level of antioxidant activity (from 75.04 to 91.54 mmol Trolox equivalents 100 g-1 ). Results of the present experiments demonstrated that content of dry matter in analysed herbal teas was significantly different (P < 0.05).
Comparison of phenolic compounds and antioxidant activity of fresh and freeze-dried potatoes
(2018) Zarins, R.; Kruma, Z.; Tomsone, L.; Kampuse, S.; Skrabule, I.; Konosonoka, I.H.
Potatoes (Solanum tuberosum L.) contain a wide range of compounds with health benefits, and different techniques have been developed for the determination of these compounds. Freeze-drying is a common method for the preservation and preparation of samples for the analyses of bioactive compounds, but it is well known that drying influences the composition of food products. The aim of the current study was to compare phenolic compounds and antioxidant activity of fresh and freeze-dried potatoes. In the experiment 11 cultivar potatoes grown in experimental fields of the Institute of Agricultural Resources and Economics in 2016 were analysed. Potatoes were freeze-dried. Homogenized fresh and freeze-dried samples were extracted with an ethanol/water (80/20 w/w) solution. Total phenolic content (TPC) was determined using the Folin-Ciocalteu method, and the antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH˙) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. The highest TPC and radical scavenging activity were determined in cultivars ‘Peru Purple’ and ‘Blue Congo’ potatoes. Freeze-drying influenced all the tested parameters but more significantly the TPC, and for certain cultivars a reduction of more than 30% was observed. A strong correlation between TPC, DPPH and ABTS in fresh and freeze-dried samples was observed, r = 0.81, r=0.93, r = 0.92, respectively. It could be concluded that the effect of freeze-drying on TPC and antioxidant activity is cultivar dependent.

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