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The aim of this study was to determine the stimulatory effect of honey addition on fermentation activity of Lactobacillus casei Lc-01 in cow’s and goat’s milk. Two monofloral honey types, dark-coloured chestnut and light-coloured acacia honey were added to cow’s and goat’s milk before fermentation. Different mathematical and statistical models were used to describe the kinetics of fermentation in all analysed samples. The basic hypothesis of this study was that addition of honey could influence fermentation kinetics in both types of milk. Comprehensive kinetic analyses suggested complex interaction between all components in fermented milk samples. The results presented in this paper showed that addition of both types of honey had a stimulatory effect on the growth of Lactobacillus casei Lc-01 in cow’s and goat’s milk. Addition of acacia honey significantly stimulated (P<0.05) the growth of Lactobacillus casei Lc-01 in cow’s and goat’s milk. This resulted in higher number of Lactobacillus casei cells, as well as in lower pH values of the samples with addition of acacia honey. Furthermore, goat’s milk was fermented faster than cow’s milk. Calculated values of selected kinetic parameters showed that the critical period of fermentation kinetics, when influence of honey proved stimulatory, was between 10th and 20th hour of the fermentation.

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To estimate the quality deterioration caused by lipid peroxidation in stored ground poppy-seed samples, the kinetic behaviour of different biochemical parameters characteristic of lipid peroxidation was studied and compared with flavour deterioration. It was found that the probability of rapid deterioration of samples is low when the change in AC values (the ratio of the values at the time of measurement and at the beginning of investigation) for peroxide values is a linear function of storage time and when lipoxygenase activity is low. When the kinetics is immediately non-linear and high activity of lipoxygenases is detected, the possibility of rapid quality deterioration can be anticipated.

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Acta Alimentaria
Authors:
M. Pardo
,
M. Bruno
,
C. Sequeiros
,
S. Trejo
,
L. López
,
N. Caffini
, and
C. Natalucci

Results are given on the milk clotting properties and casein hydrolytic behaviour of partially purified extracts of four new cysteine plant endopeptidases: balansain, hieronymain, asclepain f, and philibertain g. Milk coagulation behaviour was different for the assayed proteases: balansain and hieronymain showed a similar performance, whereas asclepain f exhibited the lowest clotting activity; philibertain g exhibited the highest one when was previously incubated with cysteine. According to the relative ratio of clotting activity to proteolytic activity, balansain, philibertain g and hieronymain appear as possible vegetable rennets. Casein hydrolysates were produced with each enzyme and the hydrolysis pattern was analysed by tricine SDS-PAGE. The α S2 - and α S1 -casein fractions, associated with cheese texture, showed different degradation patterns: higher degradation kinetics was obtained for philibertain g, followed by balansain and hieronymain, whereas asclepain f showed the lowest activity. The β-casein fraction, related to bitterness, showed similar initial degradation kinetics for balansain and asclepain f; degradation was faster in the case of philibertain g and slower for hieronymain. In the case of the κ-casein fraction, involved in milk clotting, the most remarkable behaviour was that of hieronymain, as this casein fraction was quickly degraded by the protease.

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Previous reports highlighted the onion solid wastes as abundant, residual material that might contain a significant load of antioxidant polyphenols. Although there have been studies pertaining to polyphenol recovery from onion wastes, the effect of temperature has not been adequately addressed. In this line, this study was undertaken with the aim of establishing a correlation between the extraction yield in total polyphenols and the extraction temperature, using acidified aqueous ethanol as the solvent system. Extraction of polyphenols from onion solid wastes was found to obey 2nd-order kinetics. On such a basis, the yield in total polyphenols at saturation could be very effectively determined and correlated with temperature using non-linear regression. The results indicated that the extraction yield at saturation is highly correlated with temperature, following a quadratic function. The extract obtained at optimal temperature (40 °C) had a total polyphenol yield of 21.10 mg gallic acid equivalents per gram of dry weight, and it was further analysed by liquid chromatography-mass spectroscopy to characterise its major constituents. The polyphenols detected were quercetin glucosides, as well as quercetin oxidation derivatives, including certain degradation products and dimers. The outcome of this study outlined that temperatures above 40 °C are rather not favourable for polyphenol extraction from onion solid wastes, as suggested by the model established through kinetics. The extract obtained under optimal conditions contained peculiar polyphenolic composition, not encountered in any other food processing residue.

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The production of Kluyveromyces marxianus biomass enriched with copper ions were studied. For that reason the growth of Kluyveromyces marxianus in whey with different concentrations of copper ions in batch process under semiaerobic and aerobic conditions were examined. The kinetics of copper ions accumulation in yeast cells, under the same conditions, as well as the reduction of chemical oxygen demand (COD) during yeast growth in aerobic condition, were monitored, as well. The concentration of copper ions in media up to 4 mg l −1 did not affect the yeast growth, whereas at a higher concentration, a marked decrease in the rate of yeast growth, ethanol production and lactose consumption occurred. In semiaerobic conditions, the maximum uptake of 0.35 mg Cu g −1 d.m. was obtained, while in aerobic conditions a lower uptake of 0.26 mg Cu g −1 d.m. and COD reduction of 85% were achieved. COD reduction was independent of the copper addition or uptake.

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Acta Alimentaria
Authors:
V. Stehlik-Tomas
,
S. Grba
,
D. Stanzer
,
N. Vahčić
, and
V. Gulan Zetić

Procedures for the production of Saccharomyces cerevisiae biomass enriched with iron and the effects of the iron ions addition into the molasses medium on the yeast growth and the production of ethanol were studied. The growth of the yeast S. cerevisiae and the ethanol production in media with different concentrations of Fe were monitored in the batch process under semiaerobic and anaerobic conditions. The highest biomass concentration and ethanol production were achieved in the medium with 0.6-0.8 g l-1 of Fe under both (semiaerobic and anaerobic) conditions. Kinetics of the iron ions accumulation in yeast cells during 24 h of growth in the batch process under semiaerobic and anaerobic conditions were monitored. In anaerobic conditions the maximum uptake (10 mg g-1 d.m. yeast biomass) was obtained after 12 h of fermentation, while in semiaerobic conditions a four times lower uptake (2.5 mg g-1 d.m. yeast biomass) was obtained after 16 h of fermentation.

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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.

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Acta Alimentaria
Authors:
Á. Koncz
,
L. Mészáros
,
J. Farkas
,
K. Pásztor-Huszár
,
R. Helt
, and
N. Lechner

Thermal and HHP treatments were compared. We established that the applied HHP treatments reduced the total cell count more significantly than thermal treatments. For example, the 10 min 600 MPa/10 min HHP treatment was equivalent to about 10 min thermal treatment at 70 °C. This combination of temperature and time is not used in the pasteurisation practice of the dairy industry. The various thermal treatments reduce the phosphatase enzyme activity to between one-third and one-hundredth of the original activity. The HHP treatments yielded similar results. Six hundred MPa pressure caused 10 to 70% decrease in the enzyme activity, while 700 MPa pressure led to a decrease of one log cycle.In the second year we tried to investigate the kinetics of the effect of HHP treatment. The 5, 10, 20, 40 min holding times were systematically applied in the range of 400 to 700 MPa. According to the results, 600 and 700 MPa HHP treatments effectively assured a decrease in the total cell count and the alkaline phosphatase enzyme activity. No organoleptic changes occurred.

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Mustard seed ( Sinapis alba L.) has valuable chemical composition and its cultivation in moderate climate, especially in Hungary is economically feasible. In spite of the advantageous chemical composition and colloid-chemical properties, the use of mustard seed flour is limited in food industry or in animal feeding because of its pungent taste. The pungent taste develops through the action of myrosinase; but it could be eliminated by heat inactivation of the enzyme. In the course of our preliminary experiments, it was observed that heat inactivation of the myrosinase enzyme depended on mustard variety. The heat stability of myrosinase enzyme prepared from different mustard varieties was examined and compared in our research work. Crude myrosinase was prepared from three mustard genotypes (Budakalászi, Tilney, and LM-1 (a low erucic acid content cultivar) and the heat stability was determined at 60, 70 or 80 °C for 5, 10, 15, 20 and 30 min. The semi-logarithmic plots of myrosinase activity as a function of time at different temperatures indicated that heat inactivation of crude myrosinase enzyme follows first-order kinetics. Characterising the rate of inactivation by the slope of the curve, significant differences were established in heat stability between genotypes at 60 °C. There were no significant differences between varieties at higher temperatures (70 and 80 °C). Longer than 10 min heat treatment causes more than 90% inactivation of the enzyme.

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The investigations carried out so far on high pigment tomatoes are confined to their nutritional aspects only. We present the comparative results of the first study on the kinetics of changes in chemical and sensory quality attributes in puree prepared from two colour mutants [dark green (dg) and old gold crimson (og c)] and seven normal tomato genotypes during storage. Puree of mutant tomatoes BCT-115 and BCT-119, carrying dg and og c genes, showed the less significant changes in TSS (7.52 and 6.02 °Brix), acidity (3.16 and 3.05%), pH (4.04 and 4.03), total sugar (12.4 and 11.13%), ascorbic acid (20.74 and 19.69 mg/100 g), lycopene (7.78 and 542 mg/100 g), and β-carotene (3.08 and 2.26 mg/100 g) during two months storage at 25 °C. Nevertheless, puree prepared from Berika and BCT-115 (dg) had higher colour (7.63 and 7.13), taste (7.4 and 7.37) and flavour (7.3 and 7.37) sensory scores during two months of storage at 25°C. These results provide new data on the effect of genotypes on the stability of quality for storage of tomato puree and insist on the utilization of these genotypes for breeding new processing cultivars in the near future.

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