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.

Antioxidants in fruit and vegetable juices have become increasingly popular because of their potential health benefits. Nowadays, juice mixes made from berries present frequent consumer choices, due to their nutritive value and high content of bioactive compounds. Commercial fruit and vegetable juices available in Serbian markets (n = 32) were analyzed for the physicochemical properties, chemical composition, and antioxidant activity. Relative antioxidant capacity index was used for the ranking of the juices according to antioxidant capacity, while antioxidant effectiveness of phenolic compounds contained in juice samples was investigated depending on phenolic antioxidant coefficients. Principal component analysis was applied to study the data structure. In addition, a multi-layer perceptron model was used for modeling an artificial neural network model (ANN) for prediction antioxidant activity (DPPH, reducing power, and ABTS) based on total phenolic, total pigments, and vitamin C content. The obtained ANN showed good prediction capabilities (the r² values during training cycle for output variables were 0.942). Phenolic, pigments, and vitamin C contents showed a positive correlation with the investigated antioxidant activity. The consumption of commercial berry fruit juices available in Serbian markets may deliver great health benefits through the supply of natural antioxidants.

Regular physical activity and healthy diet have a significant positive impact on children’s health. Lack of physical activity increases the risk of various diseases, while obesity has become an alarming health problem worldwide. The aim of this study is to investigate the patterns of physical activity and diet among 11–14-year-old school children in Serbia. The sample included 623 primary school children, of whom 333 were boys (53.45%) and 290 were girls (46.55%). The children were also divided according to their age/grade: fifth grade/11 years (24.40% (n = 152; M = 84, F = 68)), sixth grade/12 years (25.68% (n = 160; M = 91, F = 69)), seventh grade/13 years (26.81% (n = 167; M = 83, F = 84)) and eighth grade/14 years (23.11% (n = 144; M = 75, F = 69)). Children’s lifestyle was assessed using two subscales of questionnaires based on the Health-Promoting Lifestyle Profile model II. The Mann–Whitney U test showed no statistically significant difference between boys and girls in the variables Nutrition (p = 0.81) and Physical Activity (p = 0.91). The Kruskal–Wallis test was applied and showed no statistically significant differences between children of different ages, regardless of gender, in the variable Nutrition (p = 0.63). However, differences were evident in the variable Physical Activity (p < 0.001), with the highest mean scores recorded in 12- and 13-year-old children and the lowest in 14-year-old children. Additionally, no statistically significant differences were found among boys as a function of age in the variables Nutrition (p = 0.55) and Physical Activity (p = 0.15), nor among girls in the variable Nutrition (p = 0.43), but in the variable Physical Activity (p = 0.01). In general, it can be concluded that the older primary school children have relatively satisfactory dietary and physical activity habits, but that these behaviors decrease with age, especially the level of physical activity. There is a need for better and more effective education of children about the benefits and importance of proper nutrition and regular physical activity.

The COVID-19 pandemic has impacted almost every aspect of life, especially daily physical activity and healthy eating habits but also mental health. Our study aimed to examine the relationship between the physical activity level, eating habits and mental health of Serbian adolescents during the COVID-19 pandemic. A total of 3506 students from the territory of the Republic of Serbia participated in this study. IPAQ-short version and HBSC-FFQ were used to assess physical activity level and eating habits, along with self-rated health. Moderate correlations were identified between physical activity, eating habits and mental health, along with average physical activity, very high life satisfaction (β = 0.177, p < 0.01) and very low emotional distress (β = −0.150, p < 0.01). A significant predictor of mental health was the frequency of breakfast on weekdays (β = 0.167, p < 0.01 for life satisfaction and β = −0.153, p < 0.01 for emotional distress), but not on weekends. Since the pandemic’s course is uncertain, the focus should be on maintaining good physical activity, nutrition and well-being.

Plum skin, a by-product of industrial plum juice production, is rich in phenolic bioactives, functional compounds, and dietary fibers. These compounds support health, while the fibers may also act as structuring agents in food processing. This study investigated the structuring properties of lyophilized plum skin (LPS) in functional plum spreads produced in laboratory (F-LS) and semi-industrial (F-IS) environments, compared to a control spread (CS). Textural and rheological properties were analyzed through penetration, spreadability, flow, and dynamic oscillatory tests. Total, soluble, and insoluble dietary fibers (TDF, SDF, and IDF) in LPS and plum purée (PP) were measured using the enzymatic gravimetric method, and pectic substances contents were quantified using the colorimetric carbazole method. Fourier transform infrared spectroscopy confirmed the presence of polysaccharides and pectins in LPS. LPS had higher TDF, SDF, and IDF compared to PP, with TDF in LPS at 38.98 ± 0.52 g/100 g d.m. and IDF as the predominant fraction. The pectin content in LPS was 0.73 ± 0.03 g/100 g d.m., and water retention capacity ranged from 3.63 to 3.86 g/g depending on temperature (room, 50, and 82 °C). Incorporating LPS into the F-IS spread significantly increased all textural and rheological parameters, with TDF three times higher (6.69 g/100 g) compared to CS. All samples exhibited viscoelastic gel-like behavior, and LPS was a statistically significant structuring agent in both functional spreads compared to CS.