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The present research aimed at evaluating the vitamin C, total phenolic content (TPC), phenolic compounds, carotenoids, and chlorophyll contents, as well as antioxidant activity (AAC) of six Actinidia species fruit. Vitamin C, phenolic compounds, carotenoids and chlorophylls were measured using high-performance liquid chromatography. TPC was determined using the Folin-Ciocalteau reagent, and AAC using 2,2-diphenyl-1-picryl hydrazyl (DPPH) assay. The highest concentrations of vitamin C and TPC were found for Actinidia kolomikta fruit (1008.3 and 634.1 mg/100 g fresh weight [FW], respectively). Among phenolic compounds, seven phenolic acids and three flavonoids were identified. The 2,5-dihydroxybenzoic acid prevailed in A. kolomikta (425.54 mg/100 g FW), while tannic acid dominated in other species (4.63-100.43 mg/100 g FW). The largest amounts of chlorophylls and carotenoids were identified as Actinidia macrosperma (4.02 and 2.09 mg/100 g FW, respectively). The AAC of fruit extracts decreased in the order of A. kolomikta > Actinidia purpurea > Actinidia melanandra > A. macrosperma > Actinidia arguta > Actinidia deliciosa according to the DPPH assay.

Hardy kiwifruit are an important source of vitamin C and phenolics, which resulted in their good antioxidant potential. A significantly higher content of these compounds was found in fruit of hybrid origin, which suggests that A. purpurea × A. arguta clones may be useful genetic resources for further interspecific hybridization.

BACKGROUND Apple concentrate and honey were spray‐dried with traditional carriers (maltodextrin, Nutriose®, Kleptose®) and with skimmed milk powder as a carrier substitute offering added value for the final product. RESULTS Skimmed milk powder, although having the lowest glass transition temperature, was the best carrier in terms of the highest powder recovery (higher than 80% was achieved) and with powder physical properties comparable to those obtained with other carriers. Thus, skimmed milk powder was used to produce honey powder of reduced carrier content (to 25% solids). The physical properties of the powders obtained and lower powder recovery indicated more problematic drying of AC. Powders produced with skimmed milk were characterized by enhanced nutritional value compared with variants with traditional carriers. CONCLUSION Thus, skimmed milk is proposed as a natural carrier for spray‐drying, offering high processing yield, the possibility to reduce carrier content in honey powder, and to create products of nutritional added value. © 2020 Society of Chemical Industry

The influence of low-temperature spray drying (inlet/outlet air, 75/50°C) with the use of dehumidified air on rapeseed honey phenolics, antioxidant activity, and aroma compounds was investigated. Maltodextrin and NUTRIOSE® were used as carriers. Additionally, skimmed milk was tested as water substitute for feed solution preparation. Honey powders obtained by this method were characterized by high antioxidant activity and rich aroma. Changes in aroma profile during drying at low temperature were recognized as favorable and creating desirable fragrance of the product. In the case of 80% honey powders (20% of carrier), the investigated properties were not deteriorated comparing to pure honey before drying. Thus, this level of carrier addition can be treated as optimal from the point of view of bioactive properties retention during low-temperature spray drying. Such low carrier addition was not presented before in case of honey spray drying, and is favorable due to the perception of such product as natural. If used as food component, the dose of such honey-rich powder can be reduced comparing to traditional products containing higher amount of carrier (usually not lower than 50%).

The ABTS and DPPH methods are among the most popular assays of antioxidant activity determination. Attempts to adapt them to different analytes and the search for the highest values of antioxidant activity has resulted in a large variety of assay conditions to be presented in the literature, including the way the measurement is made. This makes it difficult to relate the results to real oxidation systems, and often makes it impossible to compare them. Such a comparison is limited in advance by the use of stable radicals that do not exist in nature and that react differently from those generated in food or in vivo. Therefore, it is important to introduce measures aimed at standardizing the conditions of the activity assay, including reaction time and several reaction environments suitable for testing different groups of compounds. In this study, we used natural antioxidants of various structures: phenolic acids, flavonoids, peptides and corresponding amino acids, ascorbic acid and α-tocopherol, and also synthetic analogues of selected compounds. The curves of dependence of the measured absorbance on the concentration of antioxidants were described, the ranges of linearity were determined, and the value of the error made when reading in various ranges of dependencies was estimated. We also determined and compared the activity values using two popular methods (IC50 and TEAC), taking into account different environments and reaction times. Based on the collected data, recommendations were formulated regarding the reaction conditions adapted to the studies of individual groups of antioxidants, and unified reaction times were proposed. Taking into account the state before reaching the equilibrium of antioxidants reacting in a complex manner, this approach may introduce a simplified reference to the competing reaction that occurs in reality.

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