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  • Author or Editor: Z. Kohajdová x
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In recent years, great interest has been dedicated to vegetable juices processed by lactic acid fermentation because they contain high amount of beneficial substances such as vitamins, mineral compounds, dietary fibre and anticancer compounds. Six types of vegetable juices were inoculated by Lactobacillus plantarum 92H and fermented at 22 °C during 150 h. On the basis of analytical (pH, total acidity, content of reducing sugars, organic acids and biogenic amines) and sensory test results (evaluation of colour, turbidity, appearance, odour and taste), cabbage and cabbage-carrot (2:1, v/v) juices were selected as the most suitable for consumers. We recommend stopping the fermentation of these juices after 72 and 96 h of fermentation.

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A capillary isotachophoretic (cITP) method to determine the concentration of nitrates and nitrites in vegetables and lactic acid fermented tomato, cucumber and cucumber-onion juices is described. Method characteristics (selectivity, response function, linearity, precision, accuracy and limit of quantification) were determined. The minimal sample pretreatment and relatively low running make isotachophoresis a good alternative to existing methods.

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Dietary fibre rich powder obtained from grapefruit by-products was analysed for its chemical composition and functional properties. The results revealed that grapefruit powder contained 50.39% of total dietary fibre, 17.36% of pectin substances, 6.65% of proteins, and 2.77% of fats. Grapefruit powder also exhibited good hydration properties (water holding, water retention, and swelling capacity), whereas its fat absorption capacity and emulsifying activity were very low. The effect of grapefruit powder as partial substitution of wheat flour in biscuit making (substitution levels 5, 10, and 15%) on the farinographic properties of wheat dough, physical characteristics, and sensory parameters of produced biscuits were also investigated. It was observed that increasing the level of grapefruit powder in dough increased water absorption and dough development time, while dough stability and mixing tolerance index decreased. Physical characteristics of biscuits (specific volume, volume index, width, thickness, and spread ratio) significantly decreased with the increasing level of grapefruit powder in biscuits. Biscuits containing 5% of grapefruit powder were the most acceptable for assessors, higher levels of grapefruit powder in biscuits negatively affected overall acceptance presumably due to the high intensity of bitter taste and increased hardness of biscuits.

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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.

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