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The Effect of Osmotic Dehydration Conditions on the Magnesium Content in Beetroot (Beta vulgaris L.)
Osmotic dehydration is a process involving a two-way mass transfer, during which water and substances dissolved in it are removed from the product and, at the same time, substances dissolved in a hypertonic solution penetrate into the tissues. This process has a significant effect on, among other things, the nutritional and sensory parameters, as well as the texture and shelf life of the dehydrated product. This study analyzed the effect of osmotic dehydration of beet on magnesium content following the addition of various chemical forms of magnesium (magnesium oxide, magnesium citrate, magnesium chloride) to a hypertonic solution. Magnesium was added in concentrations of 2.5 or 5.0% relative to the mass of the solution. The following compounds were used to prepare hypertonic solutions (25 and 50%): inulin, xylitol, erythritol, and sucrose. The control sample was water. A significant increase in magnesium content in the dehydrated material was confirmed. This effect was determined by many factors, among which the most important were the chemical form of magnesium, the type of osmotically active substance, magnesium concentration, and process time. The highest magnesium content was found in samples dehydrated in a 50% inulin solution with a 5.0% addition of magnesium chloride under the following conditions: 120 min/30 °C. It was also demonstrated that osmotically dehydrated samples exhibited approximately 3–5 times lower antioxidant activity in DPPH, ABTS, and ORAC tests.
Product Development Study of Freeze-Dried Apples Enriched with Sea Buckthorn Juice and Calcium Lactate
Enriched or fortified foods are typically linked to ultra-processed foods, limiting the choice of functional food in the market. Addressing the market potential, particularly the elder population with osteoporosis, the functional food industry should consider developing a healthy snack enriched with bioactive substances. This study aimed to produce freeze-dried Polish Gala apple with improved antioxidant properties and calcium content via impregnation or osmotic dehydration process. The solutions containing various concentrations of sea buckthorn (SB) juice and inulin were prepared at different temperatures and times, then analyzed by response surface regression modelling. Subsequently, the effect of the addition of 0–6% calcium lactate (CaL) on antioxidant properties and calcium content was also studied. Freeze-dried apple, after impregnation with 93.8% SB juice, 0:100 inulin–SB juice ratio, at 30 °C for 120 min, with the addition of 4% CaL (hereafter called “4% CaL” treatment), possessed a minimum yet acceptable loss of antioxidant properties and increased calcium content (2209.13 mg Ca/100 g). UPLC-PDA revealed the altered compositions of phenolics (flavonols were dominated by isorhamnetin-3-O-glucoside and isorhamnetin-3-O-rutinoside) and carotenoids in 4% CaL. The 4% CaL also exhibited lower polyphenol oxidase and peroxidase activities, moderate sensory acceptability with soft texture, and better nutritional values with lower calories when compared to the controls. This work is a scalable study, covering aspects of process design, physicochemical, nutritional, and enzymatic properties, as well as sensory profiling, which has potential for industrial implementation.