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ABSTRACTStrawberries intended for processing are usually frozen to withstand storage and distribution. However, freezing and thawing can cause the degradation of bioactive compounds. The aim of this study was to determine the optimal conditions for frozen storage and thawing to minimize any loss of nutrients prior processing. Different freezing treatments (−20°C, shock-freezing with liquid nitrogen, −80 °C) up to 6 months of storage and thawing treatments (4°C, room temperature, 37°C, microwave) were compared based on the content of organic acids, sugars, and phenolic compounds as well as the activity of peroxidase and polyphenol oxidase. During frozen storage at −20°C over 6 months, the sucrose content decreased by 59%, but only a 17% loss of ascorbic acid was observed, and no significant loss of anthocyanins was detected. However, more significant changes in composition were detected after thawing. When thawed at 4°C for 24 h, ascorbic acid content decreased by 32%, anthocyanin content by 30%, and sucrose content by 66%. Based on our study, the frozen storage caused smaller changes in the fruit’s composition than thawing. From the thawing procedures, the microwave thawing showed minimal changes in the composition of strawberries.

This study researched the combined effects of heat treatment and varying concentrations of the pectolytic enzyme on the improvement of yield, color, and extraction of sugars, acids, and bioactive compounds of the ‘Merlot Kanthus’ grape juice. Application of low (0.05 IU/mL) and high (0.09 IU/mL) enzyme treatment substantially increased the yield of unpasteurized and pasteurized juice. Color intensity significantly improved in the pasteurized juice with a high enzyme concentration (CIRG 4.4) and the pasteurized juice without enzymes (4.5). No considerable differences in the total sugar concentration between the treatments were observed; however, the concentration of organic acids was improved by 27 and 13% in unpasteurized and pasteurized juice with a high enzyme concentration, respectively. A total of 78 individual phenolic compounds were identified, and the treatment with a high enzyme concentration had the most notable effect on the total anthocyanins, improving their concentration by 33.6% and increasing the concentration of 18 individual compounds. The heat treatment increased flavonol concentration by 41%. Overall, heat and enzyme treatment, mainly the high enzyme concentration, had a very favorable effect on the parameters of the analyzed ‘Merlot Kanthus’ grape juice, with a significant increase in the yield of bioactive components.

Secondary metabolites, namely, phenolic and volatile organic compounds, contribute to the nutritional and organoleptic quality of the strawberry fruit. This study focuses on the changes in the content of phenolic compounds and volatile organic compounds during the ripening, from green to overripe fruit, of five strawberry cultivars (‘Asia’, ‘CIVN 766’, ‘Aprica’, ‘Clery’, and ‘Malwina’). Additionally, these changes are compared with the colour of the fruit and peroxidase and polyphenol oxidase activity. Our results show that the accumulation of secondary metabolites (phenolic and volatile organic compounds) significantly changed during the ripening process for all of the studied cultivars. As for phenolic compounds, flavanols and hydroxybenzoic acid derivatives comprised between 87 and 95% of the total phenolic compound content in unripe green fruit. In contrast, anthocyanins and hydroxycinnamic acid derivatives comprised between 64 and 77% of the total phenolic compound content in overripe fruit, except in the fruit of the cultivar ‘CIVN766’. When it comes to the aroma profile, the content of aldehydes decreased by 24–49% as the fruit ripened, and the accumulation of esters increased. Our study also shows that the ripening process differs among cultivars, and it is therefore necessary to define ripening indicators separately for each cultivar.

The distribution of primary and secondary metabolites within a fruit can affect its nutritional and organoleptic quality, as fruit can vary in size and shape. This study investigated the differences in the distribution of the primary and secondary metabolites in the fruit of four strawberry cultivars (‘Asia’, ‘Clery’, ‘Frederica’, and ‘Sandra’) that were collected at one harvest point. The study included an analysis of the individual sugars, organic acids, phenolic compounds, and enzymes responsible for the degradation of phenolics. All of the studied cultivars showed a lower pH, higher total organic acid content, and lower glucose and fructose content in the outer part of the fruit. Differences were also observed in the total phenolic and anthocyanin contents, which were always higher in the outer part. The absolute differences in the total phenolic content ranged from 3723 to 6154 mg kg−1 dry weight. Our results provide a basis for understanding the differences in the biosynthesis of these metabolites within this fruit and prove that it is essential to mix samples well before extractions to obtain results that are representative of the whole fruit.

Strawberries are appreciated by consumers for their characteristic taste and health benefits, which enhance their demand throughout the year. Everbearing strawberries can produce fruits for a longer period and could thus meet this demand, but the fruit quality depends on environmental factors and the cultivar. This study focused on the effect of environmental conditions on the physical attributes and the composition of everbearing Capri cultivar fruit harvested from the end of June to the end of October. A positive correlation was observed between temperature and organic acid content (r = 0.87), and a positive correlation was observed between sunshine duration, anthocyanin (r = 0.87) and phenolic compound contents (r = 0.89). Additionally, the composition of sugars was affected by the environmental conditions. While strawberries harvested towards the end of October, when lower temperatures predominated, were larger in size and had a higher sugar/acid ratio, fruit harvested in the middle of August, when there were longer periods of sunshine, had higher anthocyanin and phenolic compound contents. In conclusion, strawberries with higher sugar/acid ratios are obtained when temperatures are lower, while strawberries exposed to longer periods of sunshine are richer in health-promoting compounds.

This study verified the in vitro activity of red cabbage and beetroot against the formation of advanced glycation end-products (AGEs) and their relationship with the biomolecules’ content. Fermentation of cabbage increased the total phenolic (~10%) and flavonoid contents (~14%), whereas decreased total phenolics/flavonoids in beetroot. Fermented cabbage exhibited higher ability against AGEs, i.e., 17% in the bovine serum albumin–methylglyoxal (BSA-MGO) model and 25% in the BSA–glucose model, while beetroot exhibited 23% and 18%, respectively. The major compounds of cabbage products were cyanidin 3-(sinapoyl)(sinapoyl)-diglucoside-5-glucoside, sinapic acid, and epicatechin. Syringic acid and epicatechin were predominantly present in fermented beetroot. 2,17-bidecarboxy- and 2,15,17-tridecarboxy-betanin were the major betalains. Fermented vegetables can be effective inhibitors of the AGE formation/accumulation and could be recommended in the prevention of diet-related diseases.

In comparison to conventional bread, gluten-free bread (GF) shows many post-baking defects and a lower nutritional and functional value. Although broccoli leaves are perceived as waste products, they are characterised by a high content of nutrients and bioactive compounds. The present study evaluated the nutritional value, technological quality, antioxidant properties, and inhibitory activity against the formation of advanced glycation end-products (AGEs) of GF enriched with broccoli leaf powder (BLP). Compared to the control, gluten-free bread with BLP (GFB) was characterised by a significantly (p < 0.05) higher content of nutrients (proteins and minerals), as well as improved specific volume and bake loss. However, what needs to be emphasised is that BLP significantly (p < 0.05) improved the antioxidant potential and anti-AGE activity of GFB. The obtained results indicate that BLP can be successfully used as a component of gluten-free baked products. In conclusion, the newly developed GFB with improved technological and functional properties is an added-value bakery product that could provide health benefits to subjects on a gluten-free diet.