Search Results

You are looking at 171 - 180 of 504 items for :

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

Recently several studies have focused on the antioxidant activity of lycopene such as quenching of singlet oxygen and scavenging of peroxyl radicals. These properties may play a role in the prevention of different cancer and heart diseases. Tomato is one of the most important sources of lycopene. The main information on the effect of environmental parameters on quality and health-retaining constituents of tomato fruit is mostly related to temperature (air- and fruit canopy temperature) and light effects that might provide a stress to the fruit. Nowadays little is know about the direct effect of elevated CO2.The aim of the present work was to evaluate the effects of elevated CO2 in Perspex open top chambers (OTC) on the lycopene content of tomato fruit.Experiments on the effects of elevated CO2 concentrations showed mixed results. In this work it was found that concentrations of lycopene in a fruit decreased significantly when elevated CO2 was used. Elevated nitrogen sources generated only slight, but not significant difference in the lycopene concentration of tomato fruit.

Restricted access

A strain of Saccharomyces cerevisiae used in the food industry was propagated in the presence of zirconium ascorbate or zirconium citrate complex. The propagation of the yeast was slightly inhibited by zirconium (Zr) in a complex form, but it was not toxic. The Zr content in the fermentation medium decreased faster when using ascorbate complex than the citrate complex. The ascorbate complex was better accumulated by the yeast (4300 mg Zr g-1 dry mass) than the citrate complex (1600 mg Zr g-1 dry mass). The total amino acid content of the yeast cells decreased in the presence of both complexes. The concentration of some amino acids [threonine (Thr), proline (Pro), phenylalanine and cysteine (Cys)] was increased by 10-39% in the medium containing Zr ascorbate, while that of other amino acids [arginine (Arg), serine (Ser), methionine (Met) and glutamic acid (Glu)] decreased by 18-60%. As a result of the presence of zirconium citrate the concentration of Glu, aspartic acid (Asp), leucine (Leu), Thr, valine (Val), Ser, Arg, Pro and Met decreased by 19-32%, and the concentration of Cys increased by 59%.

Restricted access

Total polyphenol content and in vitro antioxidant properties were investigated in five lager and three dark beers. The average concentration of total polyphenols in lager and dark beers was 376 and 473 mg l -1, respectively. All samples exhibited strong hydrogen-donating property and reducing power in a concentration-dependent manner. Beers also showed copper(II)-chelating ability and antioxidant property in Randox TAS measurement. The differences of polyphenol content and antioxidant characteristics between lager and dark beers were statistically not different. Antioxidant properties were dependent on the total polyphenol content of beers. The concentration of polyphenols and antioxidant properties except for chelating ability of beers measured in the same in vitro test system was very similar to those characteristics of white wine, while the extent of chelating ability of beers showed similarity to that of red wines. Studies evaluating the relative benefits of wine versus beer versus spirits suggest that moderate consumption of any alcoholic beverage is associated with lower rates of cardiovascular disease. Although beers have antioxidant capacity like white wines with having half the alcoholic content of wines, beers should be good sources of antioxidant polyphenols, and moderate consumption as a part of a well-balanced diet cannot be criticised either medically or socially and may have a beneficial effect on reducing oxidative disorders.

Restricted access

The compounds of interest in the present study were the natural compounds rutin and quercetin, which are strong antioxidants and have beneficial effects on human health (Myake & Shibamoto, 1997). They are present in everyday foods and beverages and in this way they are used as an integral part of human diet. Therefore, it seemed interesting to investigate the influence of these valuable natural compounds on corrosion processes of aluminium, an ambalage material often used in food industry (Jovanovic et al., 1994). All the investigations were performed in 3% solution of sodium chloride, in aqueous rutin and quercetin solutions as well as in rutin and quercetin solutions in 3% sodium chloride solution. Concentrations of rutin and quercetin solutions used ranged from 10-2 to 10-5 mol dm-3, and investigations involved electrochemical methods. The results obtained showed that rutin and quercetin previously dissolved in 0.1 M NaOH and added to the 3% sodium chloride solution at concentrations of 10-4 and 10-5 mol dm-3 acted as aluminium corrosion inhibitors, while at higher concentrations (10-2 and 10-3 mol dm-3) their effects were opposite. The efficiency of the corrosion inhibition of aluminium by rutin and quercetin solutions was the result of forming protective film on the metal surface. Therefore, the diluted rutin and quercetin solutions could be used as corrosion inhibitors of aluminium.

Restricted access

The content of potentially antioxidant, anticarcinogenic and antiallergic flavonoid aglycons, quercetin, kaempferol, myricetin, apigenin and luteolin of 45 fruits were determined by RP-HPLC with UV detection. Fresh and dried fruits were purchased in the local markets in Budapest at a period of their most frequent consumption. Total flavonoid content of fruits varied between 0–1000 mg kg –1, the average concentration was about 30 mg kg –1 fresh weight. Quercetin could be detected in most fruits, namely in apples, pear, plums, sweet and sour cherry and berries between 10–53 mg kg –1. Luteolin at a concentration of 20 mg kg –1 was found in melons, apples, kiwi and lemon. Myricetin was in detectable amount in redcurrant, and at very high concentration in some berry fruits (mulberry 453 mg kg –1, raspberry 540 mg kg –1, blackberry 636 mg kg –1, strawberry 994 mg kg –1), and in walnut (4565 mg kg –1). Kaempferol and apigenin were not found in the fruits investigated. None of the five flavonoids was found in some variety of grapes, in peach, pear, banana, orange, grapefruit and tangerine, in nuts such as almond, pistachio, nuts, and in dried fruits such as raisin, date, fig and prunes. These data provide a basis for the evaluation of the average daily intake of Hungarian population and for an epidemiological evaluation of health-promoting effects of flavonoids. __

Restricted access

Eight Lactobacillus, five Saccharomyces and one Streptococcus strains were chosen to perform mono and mixed culture fermentations, focusing on interaction investigation via agar diffusion and analysis of cell growth kinetics, both serving as selection criteria. Mixed culture fermentations with four lactic acid bacteria (Lb. bulgaricus, Lb. paracasei SF1, Lb. plantarum 2142, and Lb. casei Shirota) and four yeast strains (S. cerevisiae W66, S. cerevisiae WS34/70, S. cerevisiae W120, and S. carlsbergensis 843) were performed in wort with initial cell ratio of 1:1. It was determined that during fermentations, cell concentration of lactic acid bacteria exceeded that of yeasts by one order of magnitude. Three strain combinations (S. carlsbergensis with Lb. bulgaricus, Lb. 2142, and Lb. Shirota) were chosen for further fermentations. Basic behaviour of them in wort was studied in mono culture, which helped to determine interaction type between bacteria and yeast in mixed culture. It resulted in higher Lactobacillus cell concentration in mono cultural than in mixed culture fermentation, which refers to competition. Cell ratio was changed to 1:10 (lactobacilli:yeasts), to favour growth of yeast and avoid lower pH. Despite the higher initial concentration of yeast, results turned in favour of lactobacillus already at the 24th hour.

Restricted access
Acta Alimentaria
Authors: M. Croitoru, I. Fülöp, M. Ajtay, G. Dudutz, O. Crăciun, and M. Dogaru

To date, monosodium glutamate is the most used flavour enhancing food additive. Because high levels of glutamate are toxic to brain concerns appeared regarding the safe use of glutamate and there is a 10 g kg −1 concentration limit in foodstuff. A simple HPLC-UV method, based on a derivatization procedure with o -phthaldialdehyde, was developed for determination of glutamate in meat products, soup bases and vegetable concentrates. Even if our method is less sensitive than the HPLC-fluorescence ones widely available, it is able to measure amounts at least 200 times smaller than the maximum allowed one, has good reproducibility (CV under 2% for intraday and under 3% for interday determinations), linearity and accuracy. Less expensive HPLC systems are required and the formed derivative is very stable (at least 1 week), good separation is obtained with the less expensive 5 μm particle C 18 columns and methanol as organic phase. Concentration of free glutamate ranged between 0.14 g kg −1 in sausage without added glutamate to as high as 2.16 g kg −1 in a pork sausage. Concentration in vegetable mixes and soup bases were between 80–120 g kg −1 .

Restricted access

The influence of three milling techniques (MT1: industrial roller-grinder, MT2: grain hammer crasher, and MT3: traditional millstone) and two baking methods (BM1: industrial oven, BM2: traditional ceramic stove heated by wood (log fire oven)) on mycotoxin deoxynivalenol (DON) and nivalenol (NIV) levels in bread were investigated. The DON and NIV concentrations in wheat grain, flour, and bread were analysed using high performance liquid chromatography with UV-detection methods. The 2 500 kg lot of wheat grain containing 1 400–1 900 μg kg −1 deoxynivalenol and 130–200 μg kg −1 nivalenol was divided into sub-lots which were processed to get three types of flour (F1: industrial bread flour, F2: industrial wholegrain flour and F3: traditional wholegrain flour). The concentrations of DON and NIV measured after milling the grain according to MT1 (yielding F1) amounted to 310–370 \g kg −1 and <50–70 μg kg t1 , respectively. After applying MT2 to the grain (yielding F2), the DON and NIV levels were measured to be 1 060–1 400 μg kg −1 and 60–87 μg kg −1 , respectively. Applying MT3 (yielding F3) produced a DON level of 1 100–1 770 μg kg 1 and a NIV level of 80–95 μg kg −1 . Six types of bread were baked from the three types of flour according to BM1 or BM2, and the mycotoxin levels were analysed. The average reduction in DON concentration after baking (70 min at 195–235 °C) was 47.2% for bread baked in the industrial oven and 48.7% for bread baked in the log fire oven. Concentrations of DON in bread prepared by the industrial MT1 were under the permitted limit of 500 μg kg −1 stated in EC (2006) regulation, despite the fact that the bread was baked from grains highly contaminated with mycotoxins. In the bread baked from traditional wholegrain flour, mycotoxin concentrations were higher (850–950 μg kg −1 ).

Restricted access

characteristics, dissolved oxygen concentration, biomass amount). It has a long tradition to use Activated Sludge Models (ASM) model family [ 10 ], therefore a lot of experience is gained in model calibration and validation procedure. These models focus on

Open access

characteristics, dissolved oxygen concentration, biomass amount). It has a long tradition to use Activated Sludge Models (ASM) model family [ 10 ], therefore a lot of experience is gained in model calibration and validation procedure. These models focus on

Open access