Urszula Trych

This study analyzed the effects of thermal pre-treatments such as convective drying (P-CD), water (BL_W), and microwave blanching (M_BL) and osmotic enrichment pre-treatments with juices from pomegranate (PG), chokeberry (CH), and sea buckthorn (SB) on microwave-vacuum-dried (MVD) carrot properties. Convective drying (CD) and freeze-drying (FD) were used as a comparative method. The dry matter content and water activity of MVD carrots were varied, but in many cases, the values were comparable to those of FD-dried carrots. Pre-enrichment in CH juice significantly reduced the values of the color parameters L*, a*, and b*, regardless of the drying method. The smallest changes were observed in microwave pre-blanching (M_BL). The lowest loss in carotenoid content was observed in CD-dried carrots (14–34 mg/100 g d.m.). Blanching and enrichment in SB juice allowed significant retention of these compounds. As a result of drying carrots, the total phenolic content (TPC) increased. Compared to the raw material, the TPC content in dried carrots increased 3–9 times. Drying using the FD and MVD methods gave a similar effect of increasing the TPC content, including a greater effect after enrichment in CH juice. The highest average antioxidant activity against the DPPH• and ABTS•+ radicals was recorded for FD-dried carrots (6.9 and 30.0 mg Trolox/g d.m.). SB juice contributed to a significant increase in the total vitamin C content, even by 89.1%, compared to raw carrots. Applying osmotic pre-enrichment in PG juice increased the sugar content in dried FD and CD samples by 37.4–49.9%, and in MVD by 21–59%.

This study emphasizes the significance of optimizing salt content during the fermentation of red beetroot to produce healthier and high-quality fermented products. It investigates the impact of different salt levels on fermentation, analyzing various parameters such as pH levels, dry matter content, total acidity, salt content, color changes, pigment content, and lactic acid bacteria count. This study identifies the most favorable salt concentration for bacterial growth during fermentation and storage as 2–3%. It was evaluated that salt levels fluctuated significantly during fermentation, with nearly 50% of the added salt absorbed by the beetroot tissues, mainly when lower salt concentrations were used. The fermentation process had a negative effect on the content of betalain pigments, as well as yellow pigments, including vulgaxanthin-I. It was also found that fermentation and storage affected the proportions of red pigments, with betacyanins proving to be more stable than betaxanthins, and that salt addition affected negatively pH and total acidity while causing an increase in yellow color. The pH was negatively correlated with the duration of the process, the amount of red pigment, and bacterial count. The results indicate that lower salt levels can lead to favorable physicochemical and microbiological parameters, allowing for the production of fermented red beetroot with reduced salt content without compromising quality.

Pumpkin is a highly nutritious plant, rich in valuable nutrients that benefit human health. Due to the high perishability of this fruit, the production of pumpkin juice is a practical way to use it effectively. Recently, fermented vegetable juices have been used as a dairy alternative due to their nutritional and potential probiotic properties. This study investigated the fermentation of pumpkin juice using different strains of lactic acid bacteria (LAB), with and without heat treatment. The effects of fermentation on microbial growth, pH, acidity, extract, sugars, carotenoids, polyphenols, and antioxidant properties were analyzed. The heat-treatment process did not greatly impact the dry matter content, pH, acidity, extract, or sugar content. However, it led to a reduction in carotenoid and polyphenol levels. During fermentation, there was a consistent decrease in pH and an increase in total acidity, with no noticeable differences between bacterial strains regarding their influence on these parameters. The study revealed that there were no distinctions between LAB strains in their effects on pH, acidity, and carotenoid content in fermented pumpkin juice. Nonetheless, both L. sakei and L. plantarum proved to be effective in the fermentation process, with L. sakei demonstrating greater adaptability. The expected pH, acidity, and sugar content changes were consistently observed throughout the fermentation process. Overall, results confirm the efficacy of the used Lactobacillus strains in fermenting pumpkin juice and highlight the potential impact of heat treatment on the nutritional composition of the juice. The purpose of thermal processing of pumpkin juice, which is conducted with lactic acid fermentation, is crucial for the food industry. It extends the product’s shelf life, improves its nutritional and taste profiles, and guarantees its microbiological safety.

The study aimed to assess the nutritional properties of fruit juices using the microwave flow pasteurization (MFP) method. The innovative spray deaeration process was also employed at two different temperatures, 25 °C and 50 °C, with three rotational speeds for the spray nozzle: 150, 450, and 750 rpm. The research focused on two not-from-concentrate (NFC) juices: apple–peach and apple–chokeberry. The innovative MFP method demonstrated significant results over 12 months of storage: no presence of Listeria monocytogenes or Salmonella spp. bacteria was detected. Polyphenol oxidases (PPOs) were inactivated, while peroxidase (POD) activity in apple–peach juice was minimal. The total polyphenol content (TPC) in the juices gradually decreased over storage time, but MFP resulted in a slower degradation of TPC than traditional pasteurization (TP). Additionally, anthocyanin and carotenoid content gradually decreased during storage time. Still, with MFP, higher concentrations of these compounds were noted up to 4 and 6 months of storage in apple–peach and apple–chokeberry juices, respectively, than with TP. The research findings indicate that MFP may be a suitable and promising technique for preserving high-quality juices with superior retention of essential nutrients. However, the recommended storage time should be at most four months.

Fermented foods have gained popularity recently, especially lactofermented vegetable juice products that provide a rich source of nutrients. This study analyzed the properties of fermented beetroot, carrot and beetroot-carrot juices fermented with bacterial strains Lactiplantibacillus plantarum or Levilactobacillus brevis. Density, extract, dry matter content, pH, total acidity, pigments (betalain or carotenoids), color and LAB count were measured. The results showed that the LAB strains used were capable of fermenting the analyzed juices. It was proven that Lactiplantibacillus plantarum was the better strain for fermentation of vegetable juice. This might have been influenced by the fermentation temperature and the duration time. The highest number of lactic acid bacteria was observed for carrot juice fermented with L. brevis on the 4th day (9.41 log CFU/mL), while for L. plantarum the highest numbers were observed on the 5th–6th day (8.9–9.1 log CFU/mL). For beetroot and its mixture with carrot juices, higher results were observed on the 5th day for L. plantarum (9.0 and 8.3 log CFU/mL, respectively). In most variants of this process, fermentation can be completed after 4–5 days. During the fermentation of carrot and mixed juice slow degradation of carotenoids was observed, while in mixed juice an increase of red pigment (betanin) was observed. In beetroot juices huge degradation was observed for fermentation with L. brevis, while the second bacteria kept the same level of red pigment almost until the last day, while yellow decreased from the 3rd day. It can be concluded that the mixed juice was most stable according to the bacteria count and the pigment content. In our opinion, L. plantarum was better for the fermentation of juices than L. brevis. However, in future tests the time of fermentation can be shortened to 5 days and other LAB strains can be tested.

Recently, the popularity of fermented foods has increased significantly. Lactofermented vegetable juice products are particularly important for our diet. The combination of the richness of the ingredients derived from vegetable juices and the products formed during lactic fermentation is a valuable source of nutrients. This study aimed to analyse the selected properties of fermented beetroot, carrot, and beetroot-carrot juices. The juices obtained from beetroot and carrot were fermented with bacterial strains Lactiplantibacillus plantarum or Levilactobacillus brevis. Density, extract, dry matter content, pH, total acidity, pigments (betalain or carotenoids), color, and LAB count were measured in the samples. The results obtained in this study showed that the used LAB strains were capable of fermenting the analyzed juices. It was proven that Lactiplantibacillus plantarum was a better strain for fermentation ion of vegetable juice. This might have been influenced by the fermentation temperature and the duration of the fermentation. However, this strain had a lower effect on carotenoids, which are water-insoluble pigments, than Lactiplantibacillus plantarum. The opposite observation was made for betalain, a water-soluble pigment with nitrogen in its structure.

In the current work, the influence of high-pressure homogenization (HPH) (200, 250, and 300 MPa) on pH, Brix, turbidity, viscosity, particle size distribution (PSD), zeta potential, color, polyphenol oxidase (PPO), peroxidase (POD), polyphenol profile and bioaccessibility of total phenolic compounds was studied. The results show no change in the apple juice’s pH, TSS and density. In contrast, other physiochemical properties of apple juice treated with HPH were significantly changed. Besides total phenolic content (15% degradation) in the HPH-treated apple juice at 300 MPa, the PPO and POD activities were reduced by a maximum of 70 and 35%, respectively. Furthermore, among different digestion stages, various values corresponding to PSD and zeta potential were recorded; the total phenolic content was gradually reduced from the mouth to the intestine stage. The polyphenol bioaccessibility of HPH-treated apple juice was 17% higher compared to the untreated apple juice.

The influence of high hydrostatic pressure (HHP) and supercritical carbon dioxide (SCCD) on the bioaccessibility of betalains in beetroot (Beta vulgaris L.) juice was investigated. Freshly squeezed juice (FJ) was treated at a mild temperature of 45 °C for 10 min (T45), pasteurization at 85 °C for 10 min (T85), HHP at 200, 400, and 500 MPa at 20 °C for 5 min (HHP200, HHP400, HHP500) and SCCD at 10, 30 and 60 MPa at 45 °C for 10 min (SCCD10, SCCD30, SCCD60). The juice was subjected to an in vitro digestion system equipped with dialysis. The content of betalains was measured with the aid of a High-Performance Liquid Chromatography (HPLC), the antioxidant capacity (AC) (ABTS•+, DPPH•) was analyzed during each digestion step, and the bioaccessibility of betacyanins and betaxanthins was assessed. The SCCD at 30 and 60 MPa significantly increased pigments’ bioaccessibility compared with other samples. The 30 MPa proved particularly advantageous, as it increased the bioaccessibility of the total betacyanins and the betaxanthins by 58% and 64%, respectively, compared to the T85 samples. Additionally, higher bioaccessibility of betacyanins was noted in HHP200 and HHP400, by 35% and 32%, respectively, compared to FJ, T45, and T85 samples. AC measured by ABTS•+ and DPPH• assays were not unequivocal. However, both assays showed significantly higher AC in SCCD60 compared to T85 (21% and 31%, respectively). This research contributed to the extended use of the HHP and/or SCCD to design food with higher health-promoting potentials.

Blackcurrant juice (Ribes nigrum L.) was subjected to supercritical carbon dioxide (SCCD) at 10, 30, and 60 MPa for 10 min at 45 °C, as well as thermally treated at 45 and 85 °C for 10 min to determine the stability, antioxidant capacity (AC), and bioaccessibility (BAc) of vitamin C, total anthocyanins, and their individual monomers. An in vitro gastrointestinal digestion model completed with dialysis was used to assess BAc. The use of SCCD at each of the pressures applied improved the stability of vitamin C, total anthocyanins, and AC before in vitro digestion. As a result of digestion, the total content of vitamin C, anthocyanins, and AC decreased. The highest BAc of vitamin C was noted in fresh juice (FJ) (40%) and after mild heat treatment at 45 °C (T45) (46%). The highest BAc of total anthocyanins was also noted in the FJ (4.4%). The positive effect of the application of SCCD on the BAc of the delphinidin-3-O-glycosides was observed compared to T45 and thermal pasteurization at 85 °C (T85). Although SCCD did not significantly improve the BAc of vitamin C and total anthocyanins, the higher AC of SCCD samples after intestinal digestion (ABTS+• and DPPH•) and in dialysate (ABTS+•) compared to thermally treated was observed. The protocatechuic acid was detected by UPLC-PDA-MS/MS as the major metabolite formed during the digestion of delphinidin-3-O-rutinoside. This may indicate the influence of SCCD on improvement of the accessibility of antioxidants for digestion, thanks to which more metabolites with high antioxidant activity were released.