Zdravko Šumić

Optimization of frozen sour cherries vacuum drying process.

The objective of this research was to optimize the vacuum-drying of frozen sour cherries in order to preserve health-beneficial phytochemicals, as well as textural characteristics. Investigated range of temperature was 46-74°C and, of pressure, 17-583mbar, in a new design of vacuum-dryer equipment. The total solids, a(w) value, total phenolics, vitamin C, antioxidant activity, anthocyanin content, total colour change and firmness were used as quality indicators of dried sour cherry. Within the experimental range of studied variables, the optimum conditions of 54.03°C and 148.16mbar were established for vacuum drying of sour cherry. Separate validation experiments were conducted, under optimum conditions, to verify predictions and adequacy of the second-order polynomial models. Under these optimal conditions, the predicted amount of total phenolics was 744mg CAE/100 dw, vitamin C 1.44mg/100g per dry weight (g dw), anthocyanin content 125mg/100g dw, IC(50) 3.23mg/ml, total solids 70.72%, a(w) value 0.646, total colour change 52.61 and firmness 3395.4g. The investigated parameters had a significant effect on the quality of the dried sour cherries.

Modeling and optimization of red currants vacuum drying process by response surface methodology (RSM).

Fresh red currants were dried by vacuum drying process under different drying conditions. Box-Behnken experimental design with response surface methodology was used for optimization of drying process in terms of physical (moisture content, water activity, total color change, firmness and rehydratation power) and chemical (total phenols, total flavonoids, monomeric anthocyanins and ascorbic acid content and antioxidant activity) properties of dried samples. Temperature (48-78 °C), pressure (30-330 mbar) and drying time (8-16 h) were investigated as independent variables. Experimental results were fitted to a second-order polynomial model where regression analysis and analysis of variance were used to determine model fitness and optimal drying conditions. The optimal conditions of simultaneously optimized responses were temperature of 70.2 °C, pressure of 39 mbar and drying time of 8 h. It could be concluded that vacuum drying provides samples with good physico-chemical properties, similar to lyophilized sample and better than conventionally dried sample.

Sensory, physical and chemical characteristics of cooked ham manufactured from rapidly chilled and earlier deboned M. semimembranosus

Effects of rapid chilling of carcasses (at -31°C in the first 3h of chilling, and then at 2-4°C) and earlier deboning (8h post-mortem), compared to rapid (till 24h post-mortem) and conventional chilling (at 2-4°C, till 24h post-mortem), on quality characteristics of pork M. semimebranosus and cooked ham were investigated. Quality measurements included pH value, colour (CIEL a b values) and total aerobic count of M. semimebranosus, as well as sensory (colour, juiciness, texture, and flavour), physical (pH value, colour - CIEL a b values and texture - Warner-Bratzler shear and penetration forces) and chemical (protein, total fat, and moisture content) characteristics of cooked ham. The cooked ham was manufactured from pieces of M. semimebranosus with ultimate lightness (CIEL value) lower than 50. Rapid chilling and earlier deboning significantly increased quantity of M. semimebranosus desirable for cooked ham manufacturing. Earlier start of pork fabrication did not affect important quality characteristics of cooked ham.

Chemical characteristics of cultivated elderberry fruit

This work is consered with the processing value of Elderberry fruit (berries) from domestic plantation selection (Horgos region). Chemical analyses of reference parameters (dry matter, acidity, pectin, pectic acid, protopectin, Capectat, ash, cellulose, total and reducing sugars, mineral substances, proteins and aminoacids, surface color, anthocyanins and vitamin C) confirmed high nutritional and physiological value of samples and full validity of work on this selection and production in plantation conditions.

Chemometric guidelines for selection of cultivation conditions influencing the antioxidant potential of beetroot extracts

Display Omitted 64 beetroot samples were cultivated under different conditions.Novel approach to samples similarity analysis was applied.The differences between the samples were detected.ANN-R model best predicts antioxidant activity of beetroot extracts. The estimation of influences of different cultivation conditions on chemical composition of crops can be quite complex task. Usually, the classical statistic approach (comparison of statistical characteristics of different populations) is applied. However, this study presents the analysis of the influence of different cultivation conditions (cultivation with or without foil cover, different preceding crops and fertilization) on the contents of dry matter, betalains and phenolic compounds in 64 beetroot (Beta vulgaris L. ssp. vulgaris) samples and their antioxidant potential (IC50) by using powerful chemometric tools, such as Wald-Wolfowitz run test, cluster analysis and sum of ranking differences, in order to obtain groupings of the samples which share similar properties or to test if the samples come from the same population. Besides the aforementioned classification or pattern recognition analysis, the regression methods (linear, multiple linear and artificial neural network regressions) were carried out in order to establish reliable linear and non-linear relationships between IC50 and contents of betalains, phenolic compounds and dry matter. The results reveal certain influence of foil cover, used during the cultivation, on beetroot antioxidant potential and content of the determined betalains and phenolic compounds, as well as the strong non-linear relationship between the analyzed variables. Certain influence of preceding crops on phenolic compounds content is detected by Wald-Wolfowitz run test.

Influence of particle diameter on the colour of ground pepper (Capsicum annuum L.)

The influence of particle diameter of ground paprika on its colour was examined in this study. Six samples of industrial ground paprika, from various phases of milling, and different particle size were purchased from the factory. Extractable colour (ASTA) and surface colour (L, a*, b*, C, λ), as the most important colour indicators, were measured. Increasing the grinding level caused the increase of ASTA and red coordinate (a*) value, and decrease of yellow coordinate (b*) value, as well as lightness of the samples, as a consequence of the increase of the specific surface area of sample particles.

Variation of bioactive compounds content in fermented cabbage: influence of fermentation temperature

The aim of this study was to analyze the effect of different fermentation temperature on bioactive compounds content of cabbage heads (Brassica oleracea var. capitata). Fermentation process was carried out at the temperature intervals 16-18 °C, 18-20 °C and 20-22 °C for 40 days. Dry weight, soluble dry weight, pH value, water activity, salt and sugar concentration, total acidity, penetration force, total color change, total phenolic compounds and organic acidswere investigated as the most important quality parameters. The highest content of total phenol compounds, as well as the highest contents of oxalic and acetic acidswas obtained in cabbage and brine sample fermented at 16-18 °C. The highest content of lactic acid in the cabbage sample fermented at 20-22 °C was obtained. In the case of brine samples, the highest contents of oxalic and lactic acids in samples fermented at 16-18 °C were observed, while the highest content of acetic acid in the sample fermented at 20-22 °C was obtained. Formic acid in cabbage and brine samples only in samples fermented at 20-22 °C was detected.