Rupture force and color of quince during osmotic drying

Quince fruit is characterized by pleasant smell, taste and ability of long-term storage. However, beside these good characteristics, the high quality of hardness and firmness of the fruit influences the decrease in its usage in the fresh state. Drying process is not a regular method in processing this type of fruit. Combined drying is a method developed at the Faculty of Agriculture in Novi Sad, Serbia and it consists of osmotic and convective drying. Disadvantages of the product got from convective drying only are eliminated with this method. The experiment tested the influence of osmotic drying on the force of rupture and quince color. Osmotic drying was done with the following combinations of temperature and concentration of sucrose solution in water: 40 deg C and 50 degrees Bx, 60 deg C and 50 degrees Bx, 40 deg C and 65 degrees Bx, and 60 deg C and 65 degrees Bx. The convective drying of the samples was uniformly done by air drying at the temperature of 40 deg C for 20 hours. Osmotic drying time was 180 minutes. Every 20 minutes samples were taken for the measurement of color, force of rupture and moisture. Sample testing by pressure was used for the analysis of rupture force of the quince. During osmotic drying on the samples, test was done on the samples of approximate size 10x10x10 mm. After convective drying, the same test was done on the samples with the original dimensions of 15x15x15 mm. The measuring instrument used in testing rupture force was TMS-PRO (Food Technology Coorporation - USA). Color measurement was performed by Konica Minolta colorimeter CR-400. CIE Lab values were used for color parameters. The change in color is defined by overall change in size of deltaE. With the analysis it was determined that the concentration of osmotic solution is an important factor in rupture force of the quince samples. The concentration of osmotic solution, has also shown an important influence on the changes in quince color. The collected results have been statistically processed in software Statistica 9.1.