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This study analyzed the phenolic compounds, organic acids, sugars, and antioxidant activity in different conventional apple cultivars (Malus domestica) from the Serbian market. Polyphenol profiles, sugars, and organic acid contents were analyzed by HPLC, and antioxidant activity was examined by DPPH and FRAP. Notable findings included variations in phenolic compound presence, with certain compounds detected only in specific cultivars. 'Red Jonaprince' exhibited the highest arbutin (0.86 mg/kg FW) and quercetin-3-rhamnoside content (22.90 mg/kg FW), while 'Idared' stood out for its gallic acid content (0.22 mg/kg FW) and 'Granny Smith' for its catechin levels (21.19 mg/kg FW). Additionally, malic acid dominated among organic acids, with 'Granny Smith' showing the highest content (6958.48 mg/kg FW). Fructose was the predominant sugar across all cultivars. Chemometric analysis revealed distinct groupings based on phenolic and organic acid profiles, with 'Granny Smith' and 'Golden Delicious' exhibiting unique characteristics. Artificial neural network modeling effectively predicted antioxidant activity based on the input parameters. Global sensitivity analysis highlighted the significant influence of certain phenolic compounds and organic acids on antioxidant activity. [ABSTRACT FROM AUTHOR]

This research aimed to develop a reliable, easy-to-perform and cheap method for measuring protein oxidation in complex samples such as aquaculture feed within various protein sources. For that purpose modified 2,4-dinitrophenylhydrazine (DNPH)-based method for quantification of protein carbonyls was employed whilst the modification of the method consisted of using different solutions for the extraction (distilled water and different concentrations of KCl and NaCl solutions), time of protein extraction (after homogenization and over the night) and concentration of trichloroacetic acid (10 and 25% TCA) for protein precipitation. Extraction during the night, higher TCA concentration and the use of 0.5 M KCl extraction solution resulted in the highest protein amount measured by the Lowry method and 280 nm protein estimation. On the other hand, the lowest protein yield was obtained by using distilled water for the extraction. Furthermore, the lowest amount of protein carbonyls was in the case when extraction was performed with distilled water (DW), while the highest content of protein carbonyls was reached with 0.15 M KCl and 0.5 M KCl extraction solutions. It was observed that the amount of proteinbound carbonyls compounds was increasing during storage under accelerated conditions and, in comparison to the original method, the modified method for measuring protein oxidation resulted in a higher amount of carbonyls during all points of storage.

Oxidative changes in fish feed during storage are a major problem in aquaculture nutrition. The current study aims to present fast and simple spectrometric method to measure thiobarbituric acid reactive substances (TBARS) in the commercial rainbow trout feeds without hydrolysis step, as a method for determination of lipid peroxidation. The proposed test was validated and relevant method characteristics which were evaluated within the validation protocol were: linearity (range), limit of detection, limit of quantification, precision (repeatability and intra-laboratory reproducibility), accuracy and method performance (Xand R-control charts). The obtained results indicated that presented TBARS test was linear in the range of 1.11-13.33 nmol/mL and precise under both repeatability and reproducibility test conditions. The method was characterized by acceptable accuracy considering low analyte concentration in the samples. The method also showed to be stable in terms of changes in the average level and variability. The results in the present work indicated that the proposed test could be successfully applied for TBARS quantification in rainbow trout feed for routine quality control in aquaculture sector, especially in case when need to analyse a great number of samples in a short time.

In the past few decades the diet preparation in feed production has evolved towards more complicated technological operations, which include different liquid addition. A wide scale of different liquids is used in contemporary animal feed production, from oils and glycerol to more expensive products in a liquid form, such as enzymes, flavourings, amino acids, vitamins and others. In the presented study the liquid addition in feed production was observed, with a specific goal to investigate the spraying systems in order to better understand the effects of fluids, such as soybean oil and glycerol, on feed production. The dispersion angles of spraying nozzle for glycerol and soybean oil were determined as an indicator of the uniform application of liquids during feed production. Dispersion of the material was accomplished using the two-fluid nozzle. The performance of Artificial Neural Network (ANN) was compared with experimental data in order to develop rapid and accurate method for prediction of dispersion angle. The ANN model showed high prediction accuracy (r2 = 0.945). [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III46012]

For many consumers egg yolk color is a very important characteristic of egg quality. Since hens are not able to synthesize coloring pigments, the intensity of the yolk color depends directly on the content and profile of pigmenting carotenoids present in their feed. The aim of this study was to assess the combined pigmenting effect of paprika and carrot and their ability to achieve egg yolks in the desired color range. Biological tests lasted for 30 days and were conducted on 180 Lohmann Brown layers. The laying hens were divided in six groups. Every group was assigned to one of six possible treatments, control 1 (C1) treatment without any pigments added, control 2 (C2) treatment with synthetic pigments added and four experimental diets (D1, D2, D3, D4) with the addition of natural color sources (paprika and carrot). After experimental period collected eggs were analyzed regarding physical characteristics of eggs, content of β-carotene and yolk color of eggs. Obtained results has shown that dried carrot and milled paprika can successfully replace synthetic pigments, with no negative effects on physical characteristics of produced eggs, egg yolk color, acceptability or β-carotene content.