Utilization of algae includes both macroalgae for human consumption dating back to thousands of years, as well as the application of microalgae in health promoting dietary supplements. The autotrophic growth of microalgae is slow, but can be accelerated by optimizing their cultivation conditions. Efficiency optimizations for time and economy should be performed in many parallel experiments. A new high-throughput microalgae cultivation method is presented here, applying 24-low-well microplate with varying illumination, in which the cell growth is followed via evaluation of scanned images. A strain of the genus Nannochloropsis and two Chlorella vulgaris species have been chosen as well described and frequently applied model organisms in order to test the recently developed cultivation system. In these scaled down experiments, the custom design lighting panel was tested by studying the effect of the colour of illumination on cell growth kinetics. RGB LEDs (i.e. light emitting diodes, red: 622 nm, green: 528 nm, and blue: 467 nm) were used individually or together providing red, green, blue, and white colours. While the effect of light’s colour on algae growth was evaluated, also the new system was proven to be suitable for comparing maximal growth rates for different microalgae strains. While the tested two Chlorella isolates reached 1.2–1.4 g l–1 concentrations, the Nannochloropsis strain reached 1.4 g l–1 final cell dry weight, and specific growth rates were observed between 0.58–0.62 day–1.
In existing processes, the extraction of steviol glycosides from stevia leaves involves many process steps often including extraction by organic solvents. The purpose of the present study was to develop a process for the effective extraction of steviol glycosides, which can provide a concentrated juice exhibiting a high level of recovery with regard to the target compounds, rebaudioside A and stevioside. Pressurized Hot Water Extraction (PHWE) was first optimized with Response Surface Methodology in terms of maximized rebaudioside-A yield and minimized colour components. PHWE was then combined with pressing in a wine-press, resulting higher efficiency for extracting both steviol glycosides in comparison to the reported methods in the literature. Finally, spray drying was applied for both product stabilization and removal of contaminants.
Authors:A. Mikulajová, Z. Kohajdová, K. Németh and E. Hybenová
Whole cereal flours (buckwheat, barley, and oat) and wheat bran were used to substitute 20% of white bakery wheat flour to prepare round rolls. Round roll quality was evaluated by determining total phenolic and total flavonoid contents, antioxidative capacity, the content of lipid hydroperoxides (primary oxidation products), and sensory profiling. Moreover, the stability of the phenolic compounds and antioxidant behaviour throughout processing was studied. Technological processing does not cause any significant loss of phenolics (less than 5%). A significant increase in antioxidants and phenolics of the flour mixtures and final products were observed compared to those of white wheat round rolls (as control). Buckwheat and barley round roll crumbs contained the highest total phenolic and total flavonoid contents, and were the most effective in enhancing antioxidant activity, which increased 15-fold and 8-fold, respectively, when compared to the control roll. The tested cereals effectively retarded formation of lipid hydroperoxides (from over 50% to control), which are undesirable from both a nutrition and storage/shelf life perspective. The results of sensory analyses showed that such bakery products are accepted by consumers with the exception of the product made with oat flour, where a reduction in the oat content would be preferable.
Authors:B. Cserháti, K. Juhos, A. Begyik, P. Radácsi, É. Németh and K. Szabó
Wild Origanum vulgare populations in Hungary have been analysed. In 2010 the morphological variability of 11 populations in five shires was investigated, the features of habitats were also described. The difference in elevation between the lowest and highest locality is 630 m. Nine plant associations, four soil types, variable pH between 4.81–7.96 and humus content from 0.54% to 6.97% were determined. Among the examined individual plants the maximum length of stem was 107 cm, the highest number of branches was 14 pairs, furthermore procumbent and mellow stems were also found. The defined colours of inflorescences are dyes of pink or purple. Despite to these we found individuals in one population with white flowers, green bracts and calyces.
Authors:B. Salamon, A. Tóth, P. Palotás, G. Südi, B. Csehi, Cs. Németh and L. Friedrich
The aim of the present study was to evaluate the effect of high hydrostatic pressure (HHP) processing (at 450 or 600 MPa for 300 s) on microbial quality as well as on organoleptic properties of fish salad with mayonnaise during 26 days of storage at 5 and 10 °C. The salad contained diced smoked trout fish, mayonnaise, and different kinds of spices. These freshly made salads usually have only a couple of days of shelf life. The HHP treatment basically did not affect the physical and organoleptic characteristics of the fish salad with mayonnaise. At both storage temperatures, the HHP treated samples showed enhanced safety and increased shelf-life up to 3 weeks.
Authors:A. Mouwakeh, P. Radácsi, ZS. Pluhár, É. Németh Zámboriné, G. Muránszky, CS. Mohácsi-Farkas and G. Kiskó
Nigella sativa L. (black cumin) is well known for its benefits in the field of traditional medicine. The aim of this study was to determine the chemical composition and investigate the antimicrobial activity of cold pressed oil (CO) and essential oil (EO) of Nigella sativa L. on food-borne pathogenic and spoilage bacteria. The microdilution method was used to determine the minimal inhibitory concentration (MIC) of Nigella sativa crude oil (CO) and essential oil (EO) against 4 Gram-positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, and Listeria monocytogenes) and 3 Gram-negative (Salmonella Hartford, Pseudomonas aeruginosa, and Escherichia coli) foodborne pathogenic and spoilage bacteria occurring in food products. Total fatty acid composition of CO was analysed by GLC, while the EO was analysed by GC-MS to detect its active compounds. The results showed that the major fatty acid of CO was palmitic acid (C16:0), as saturated fatty acid, however, linoleic acid (C18:2) was the main unsaturated fatty acid. The major compounds of the EO were p-cymene and thymoquinone. The inhibition on all tested bacteria of EO was 10 times higher than of CO, and the lowest concentration value was observed in case of Bacillus subtilis (0.003%). Hence, results reinforce the ambition to apply Nigella sativa oils in food as natural preservative.
Authors:E. Horvath-Szanics, J. Perjéssy, A. Klupács, K. Takács, A. Nagy, E. Koppány-Szabó, F. Hegyi, E. Németh-Szerdahelyi, M.Y. Du, Z.R. Wang, J.Q. Kan and Zs. Zalán
The increasing consumer demand for less processed and more natural food products – while improving those products’ quality, safety, and shelf-life – has raised the necessity of chemical preservative replacement. Biopreservation refers to extended storage life and enhanced safety of foods using the natural microflora and (or) their antibacterial products. Chitinolytic enzymes are of biotechnological interest, since their substrate, chitin, is a major structural component of the cell wall of fungi, which are the main cause of the spoilage of food and raw plant material. Among the several organisms, many bacteria produce chitinolytic enzymes, however, this behaviour is not general. The chitinase activity of the lactic acid bacteria is scarcely known and studied.
The aim of the present study was to select Lactobacillus strains that have genes encoding chitinase, furthermore, to detect expressed enzymes and to characterise their chitinase activity. Taking into consideration the importance of chitin-bindig proteins (CBPs) in the chitinase activity, CBPs were also examined. Five Lactobacillus strains out of 43 strains from 12 different species were selected by their chitinase coding gene. The presence of the chitinase and chitin-biding protein production were confirmed, however, no chitinolytic activity has been identified.