# Shaping the Properties of Osmo-Dehydrated Strawberries in Fruit Juice Concentrates
## 3 Results and Discussion  
### The Influence of Fruit Concentrates on the Kinetics of the Strawberry Osmotic Dehydration Process  
During osmotic dehydration, water from the food matrix passes into the hypertonic solution and solutes present in the solution flow into the food matrix. This is due to the difference in osmotic pressure between the food tissue and the osmotic solution. The mass transfer rate depends on many factors, among which is the type of osmotic agent [13; 28]. Mass transfer parameters in terms of weight reduction (WR), water loss (WL), and solid gain (SG) are reported in Figure 1. A statistically significant effect of the type of osmotic agent was found only on the WR and WL of dehydrated strawberries. Moreover, both of these parameters, as well as SG, were significantly dependent on the dehydration time (\(p\) < 0.05). The highest rate of weight reduction, water loss, and solid gain were at the initial stage of the process, regardless of the type of hypertonic solution. The longer the osmotic dehydration was, the bigger the mass transfer was observed. However, in all cases, the mass transfer decreased after 30 min, which was caused by a decreasing osmotic pressure difference between the dehydrated tissue and the surrounding solution. A similar tendency was observed during the osmotic dehydration of apples in grape juice, apple juice, and cranberry juice as described by [PERSON] et al. [29]. At the end of the process, strawberries osmodehydrated in a sucrose solution were characterized by the lowest values of both WR and WL. These values were significantly smaller than in the cases of the use of chokeberry or cherry juices. Each of the juice concentrates contains many substances with different molecular sizes that can increase the osmotic pressure that determines water loss but can also increase solid gain in dehydrated fruit tissue. For example, according to [PERSON] and [PERSON] [30], unconcentrated chokeberry juice, containing 11-17% dry matter, contains 110-143 g/L of sugar, including glucose, fructose, and sorbitol, approximately 32-40, 30-39, and 48-64 g, respectively/L. Other ingredients include polyphenols 4.7-9.0 g/L, fiber 3.0 g/L, as well as minerals 5.0 g/L, proteins 2 g/L, and fat <1 g/L. [PERSON] et al. [7] presented a detailed composition of polyphenic compounds in chokeberry juice used as an osmotic agent, the total content of which was about 2919.4 mg/100 g d.m. Among the identified compounds were the highest content of polymeric procyanidins (1857.4 mg/100 g d.m. ), as well as phenolic acids, such as chlorogenic (400.1 mg/100 g d.m. ), neochlorogenic (251.2 mg/100 g d.m. ), and many other flavonoid compounds, as indicated. Although there was no significant effect of the type of osmotic agent on the solid gain of strawberries, it was observed that, compared with the sucrose solution, the values of this index were slightly higher when using juice concentrates. Due to the content of many components of different molecular weights contained in the juice concentrates, these osmotic agents showed a higher osmotic potential than the sucrose solution. Although all osmotic agents had the same concentration, the water activity of the concentrates was in the range of 0.90-0.91; that of sucrose was 0.95 (Table 1). In addition to the particle size of the osmotic agent components, the viscosity may determine the differences in the penetration of osmotic substances into the food material. Juice concentrates may contain ingredients that increase this effect, e.g., pectins. The higher the viscosity, the higher the adhesive forces to maintain adsorbed solids on the surface and inner capillaries of the strawberry tissue. Such an effect may affect the mass transfer resistance during osmotic dehydration. In the literature studies, a varied effect of chokeberry juice concentrate on solid gain was found. [PERSON] et al.