Search Results

You are looking at 1 - 10 of 14 items for :

  • Materials and Applied Sciences x
  • All content x
Clear All

Glycosyltransferase activity of Pectinex ultra SP-L (from Aspergillus aculeatus) commercially available enzyme preparation was studied in mono- and bisubstrate systems using different donors (maltose, lactose, and sucrose) and acceptors (fructose, galactose, glucose, maltose, mannose, xylose, lactose, and sucrose). Oligosaccharides consisting of three monomers were detected in the cases of maltose, sucrose, and lactose as monosubstrates, thus this preparation should contain glucosyl-, fructosyl-, and galactosyl-transferase activity. Generally, yields of oligosaccharides synthesized were higher in bisubstrate systems maltose:sucrose, maltose:lactose, and sucrose:lactose than on monosubstrates. Use of maltose:sucrose bisubstrate resulted new oligosaccharide(s) (fructosyl-maltose or glucosyl-sucrose). The optimal ratio of substrates in the case of maltose:sucrose was determined to be 1:9. Increase of the dry content of the reaction mixture induced the transfer reaction. The highest oligosaccharide content was obtained at 60% (w/v) substrate concentration. In the case of the optimal ratio and dry content, 4.02% (w/v) oligosaccharide (DP3) concentration was achieved. These oligosaccharides may alter prebiotic and biochemical properties in food applications.

Restricted access

The aim of the work was to evaluate the authenticity of honey present in Lithuanian market using GC-FID analysis of trimethylsilylated carbohydrates. In total, 15 natural honey samples and one artificial honey sample were analysed. In general, the composition of carbohydrates in the tested samples of natural honey was quite similar, except for trisaccharides, which were not found in any of the analysed samples. Although the amount of identified compounds was different, the percentages of the quantified sugars in natural honey were within the limits established by Codex Alimentarius Commission. Artificial honey contained 9.01% of sucrose and 34.60% of maltose, while the content of maltose in natural honey varied in the range of 0.29–1.41%. The content of fructose and glucose in artificial honey was 2.41% and 22.89%, respectively; while the sum of the main monosaccharides in natural honey was averagely 38.80%. The results obtained indicate that tested natural honey samples from Lithuanian market were genuine products.

Restricted access

This study was aimed to investigate the effect of carbon and nitrogen sources on the production of bioactive total dietary fibres (TDF) and glucans (α- and β-glucans) in submerged cultures of wild Ganoderma australe and commercial Pleurotus ostreatus, both of Greek origin. The contents of glucans and TDF were determined by using the respective Megazyme enzymatic kits. Glucose and yeast extract (YE) were suggested as appropriate carbon and nitrogen sources, respectively, for obtaining simultaneously high production of TDF and β-glucans by G. australe, which are compounds of great pharmacological interest, whereas maltose and YE were found favourable for high production of the above-mentioned functional components by P. ostreatus. The data obtained in this study provide useful information for further development of the studied mushroom fermentation process on a scale of the bioreactor aiming at enhanced TDF and β-glucan production.

Restricted access

Fermentation trials were conducted in all-malt wort with mixed cultures of SaccharomycescerevisiaeWS 34/70 and one of two non-Saccharomycesyeast strains: Saccharomycodesludwigiiand Torulaspora delbrueckiiDSM 70607. Interactions were observed between the two yeasts during the alcoholic fermentation process started with eight different initial cell ratios ranging from 1:1 to 1:20 (Saccharomyces yeast : non-Saccharomyces yeast). Composition of the medium greatly affected the cell yield, degree of attenuation and ethanol concentration due to the maltose-negative characteristic of the non-Saccharomycesyeast strains. Starting cell ratios had less effect on the outcome of the fermentation experiments. S. cerevisiaelimited the growth of T. delbrueckiito a great extent, overgrowing it in the course of fermentation. On the other hand, S. cerevisiaedid not grow as dynamically in mixed culture with S. ludwigiias the composition of the medium would have suggested.

Restricted access
Acta Alimentaria
Authors: L. Červenka, S. Řezková, J. Hejdrychová, J. Královský, I. Brožková, M. Pejchalová, and J. Vytřasová

Chemical composition (moisture, ash, protein, fat, total carbohydrate, sucrose, fructose, glucose and maltose) of four types of biscuits and four gingerbreads were determined and moisture adsorption characteristics of samples were evaluated at 25 °C using the Novasina hygrometric technique. Generally, the GAB model gave the best description of the experimental sorption data; however, these findings were not statistically significant compared with the BET model. Gingerbreads absorbed higher amount of water (20–25 g/100 g on dry weight basis) at a w >0.70 in comparison to biscuits studied mainly due to higher content of sucrose and/or other simple saccharides. Monolayer moisture content evaluated by BET and GAB models were in general higher for the gingerbreads. Although the Novasina water activity meter is suitable for construction of sorption isotherms, in the lower range of a w values (i.e. <0.45) the water uptake is slightly underestimated.

Restricted access
Acta Alimentaria
Authors: B. Vecseri-Hegyes, P. Fodor, and Á. Hoschke

The most sensitive and time-consuming technological step of beer production is the fermentation of wort. Problems during fermentation will not only prolong production time but it will lead to the deterioration of beer quality. Most often it is due to low zinc concentration of the wort or the yeast. Due to lack of zinc the fermentation lasts longer, composition of fermentation by-products changes, maltose intake slows down, sedimentation ability and heat sensitivity of the yeast increase. In Part I of our work, the factors affecting the degree of zinc supply of wort were examined. During the examination of zinc supply of wort two kinds of beer were produced: all-malt beer and beer with adjunct. Change of zinc concentration was followed throughout the brewing process at every technological step. It was found that concentration of zinc gradually decreases during production of wort, and only a small fraction of the calculated amount appears in it. Wort made with adjunct has even lower zinc concentration than all-malt wort. In all malt wort 3.4%, while in wort containing adjunt only 0.4% of the zinc appeared in the wort. Yeast can absorb only the ionic form of zinc during fermentation, thus we had elaborated a method for the separation of the organic and inorganic form of zinc, which was followed by the determination of the concentration of ionic zinc in wort prior to fermentation.

Restricted access

In this study, the effects of various carbon sources for Morchella conica sclerotium formations were investigated under in vitro conditions. The formations of sclerotial initials, which improved from hyphae of Morchella conica , were obtained by using different carbohydrates. Vegetative mycelia were developed very well in agar media, containing malt extract (MEA), wheat (WA), potato dextrose (PDA) and complete medium yeast extract (CYM), however, moderate development occurred in defined media, containing glucose, sucrose, maltose and starch. The carbohydrate concentrations were prepared as 0.0%, 0.25%, 0.50%, 0.75%, 1.00% and 1.25%. Whole wheat agar and potato dextrose agar media consisting of glucose, sucrose and 0.25%, 0.75% and 1.25% starch excluded, while other cultural environments supported sclerotial formations. Sclerotial structures were examined morphologically and anatomically. The pigmentation changed from yellow to orange and brown. Time sclerotial formation varied from 10 days up to 7 months. Pigmentation, structure and quantity of sclerotia were taken as morphological criteria. Anatomical properties of sclerotia were obtained on light microscopy and scanning electron microscopy. Generally, sclerotial cells were very thick and spherical.

Restricted access

The aim of this study was to develop simple, rapid and reliable methods for the selective determination of Bifidus essensis from ACTIVIA (Danone) yogurts. The methods are based on a modified MRS medium (B-broth), which does not contain inhibitory additives. The sugar source of the medium is maltose, which is metabolized by the bifidobacteria applied in the probiotic products, and not by the normal microflora of yogurt ( Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus ). The redox potential of the medium was reduced with cysteine-HCl. Due to its reduced redox potential, the new bouillon is suitable for aerobic cultivation of bifidobacteria, while in agar form it needs anaerobic incubation. In bouillon form (MPN method) the incubation time is only 2 days compared to the 5-day requirement of the classical anaerobic plate counting methods. The B-broth in diluted form was successfully used in a RABIT (Don Whitley) equipment for selective impedimetric determination of bifidobacteria in Danone yogurts. The exact detection time of the Bifidobacterium counts in a good quality probiotic yogurt, containing bifidobacteria at a concentration of 10 7 to 10 8 CFU ml −1 is not more than 10 to 12 h (in contrast to the 5 days of classical anaerobic plate counting methods).

Restricted access

Currently gluten-free beer is not produced in Hungary for coeliacs. The goal of our research was to develop brewery products made of domestically grown millet (Alföldi 1) and buckwheat (Oberon) that are similar to traditional beer of barley malt regarding taste, aroma, consistency, colour, foam stability and alcohol content.On a micromalting equipment malts were made of buckwheat and millet. Beer was produced on pilot plant scale (50 l) with decoction process (mashing program with rests at 50 °C, 65 °C and 72 °C) and was supplemented with a highly heat-stable bacterial α-amylase, a fungal α-amylase and β-glucanase. Malts were evaluated by congress mashing (extract content, extract difference, pH, and colour); wort and final beer analyses were performed as well (pH, extract, iodine test, FAN, colour, bitterness, alcohol and extract content). Finally, sensory characterization was carried out. Difficulties with lautering were encountered during the brewing process with buckwheat. The analytical results indicated that the buckwheat and millet beer had different values compared with a typical barley beer with regard to pH, FAN, fermentability, and total alcohol. The extracts of the buckwheat and millet wort were lower, resulting in a final attenuation of 61.5% and 73.2%.In laboratory experiments optimal temperature of β-amylase found in domestically grown buckwheat (64 °C) and millet (62 °C) was determined by detecting maltose production with HPLC. Data was used to set the rest temperature of the enzyme during mashing. Inhibiting effect of certain substances on proteolytic enzymes was investigated by measuring the extract, FAN, and soluble nitrogen contents. Inhibition was detected in case of both raw materials, although to a different extent. Inhibition is influenced by tannins and polyphenols found in the grain (Chethan et al., 2008).

Restricted access

. M. (1979): Synthesis and properties of alkylglucosides with mild detergent action: improved synthesis and purification of β-octyl, -nonyl and -decyl-glucose. Synthesis of β-1-undecyl-glucose and β-1-dodecyl-maltose. Chem. Phys. Lipids , 23 , 321

Restricted access