The influence of the pretreatment of garlic (Allium sativum L.) and tomato (Solanum lycopersicum L.) osmotic solution on physical properties of the material

Abstract

AbstractThe study investigates the osmotic dehydration of garlic in osmotic solution (OS) prepared from tomato juice with the addition of basil extract. Garlic was pretreated using blanching and freezing at different temperatures in order to determine the effect of thermal pretreatments on mass transfer during osmotic dehydration (OD). Moreover, the pH of OS was gradually lowered (with citric acid or ascorbic acid) from pH = 3.5 to 2.0 prior to OD to study the effect of pH on the mass transfer during OD process. The study found that thermal pretreatment significantly affected solid gain and water loss during OD. It was shown that acidification of the OS improved mass transfer between garlic and OS, and the relationship between viscosity and pH of the solution was sinusoidal. It means that by changing the pH of the solution, the viscosity of the solution could be lowered. Moreover, it was shown that the lower the viscosity of the OS, the higher the water loss and solid gain, and the relationship between the two is linear.Practical ApplicationsThe presented research can be of interest to the food industry due to the results regarding the pretreatment of the raw material and OS that lead to the significant improvement of the mass transfer during osmotic dehydration. It is especially important since osmotic dehydration process can allow to improve the shelf life of the product by reducing the water activity of the material. Moreover, when osmotic dehydration is performed in concentrated juices it can affect the quality of the material by incorporating health‐promoting compounds from the solution. The study found that lowering the pH of the OS to an appropriate degree significantly increases water loss and solid gain. Similar results can be obtained when freezing the raw material at −20°C, which, however, increases the overall energy consumption of the process. In addition, the study shows that other thermal treatments (freezing at −40°C, −80°C, freezing in N2, and blanching) affected mass transfer less effectively than acidification of OS. Moreover, changing the pH of the solution generates much lower energy consumption than the thermal treatment of the material, while saving overall processing time.