## 2 Materials and Methods
### Physico-Chemical Analysis  
**Apple water extract** for determination of active acidity, titratable acidity, total soluble solids contents and electrical conductivity was prepared as follows: 50 mL of distilled water was added to 20 g of fresh/dried apples measured with a precision of 0.01 g. The  
Figure 1: Steps included in sample preparation and drying. content was heated on a water bath brought to boil for 30 min. After boiling, the extract was cooled, and the content was brought to 250 mL with distilled water and then filtered. **Moisture** (\(M\)) was determined by oven-drying method; thus 5 g of apple slices from each sample was weighed and dried at 105 \({}^{\circ}\)C until constant weight [20; 33]. **Water activity** (_aw_) was determined by using a water activity meter AquaLab Lite (Decagon, WA, USA). The determinations were performed at 25 \({}^{\circ}\)C, and all samples were measured in triplicates. In a special cuvette was introduced approximately 3 g of the sample; after that, the cuvette was placed in _aw_ chamber, and the water activity was measured and displayed on the water activity meter screen [33]. **Active acidity** was determined by \(pH\) measurements at ambient temperature using laboratory \(pH\) meter Fisher Scientific ACCUMET Bio Set AE150 (Fisher, Waltham, MA, USA). For each sample, a 10 mL volume of apple extract was measured, the \(pH\) electrode was inserted, and after stabilization, the \(pH\) value was displayed on the \(pH\) meter screen [34]. **Titratable acidity** (_TA_) was obtained by titrating 50 mL of apple water extract with 0.1 N NaOH solution, in the presence of 1% phenolphthalein solution. The _TA_ values were calculated according to [PERSON] and [PERSON] [35], and the results are expressed as malic acid (%) [36]. In apple, malic acid is the predominant acid (80-90% of the organic acids) that contributes to sourness of fruits [35; 37]. **Total soluble solids contents** (\(TSS\)) were measured by using a digital hand-held refractometer standardized with distilled water. Two drops of fresh/dried apple extract were placed on the refractometer lens and measured. The obtained values were corrected to the equivalent reading at 20 \({}^{\circ}\)C [38; 39] and reported as 'degrees Brix' (\({}^{\circ}\)Brix) which is equivalent to percentage (%) [40]. **Total sugar contents** in fresh and dried apple samples were determined by applying [PERSON]'s method. Into a 300 mL Erlenmeyer flask, was placed 20 mL of the defecated extract, then 10 mL of Fehling I solution and 10 mL of Fehling II solution. The vessel was heated on an asbestos sieve, adjusting the flame for boiling, and boiled for exactly 2 min. The flask was cooled rapidly under running water, and then 20 mL of KI solution and 15 mL H\({}_{2}\)SO\({}_{4}\) were added. Released iodine was titrated with 0.1 N Na\({}_{2}\)S\({}_{2}\)O\({}_{3}\) in the presence of starch (1%) as an indicator. Results were expressed in %. Sugar/acid ratio was calculated as the total sugars content divided by titratable acidity. **Electrical conductivity** (_EC_) of samples was measured with a laboratory conductometer VioLab COND 51+ Set (ROTH, Germany) and was expressed in \(\upmu\)S/cm. The conductometer electrode, after calibration, was inserted into 10 mL of apple extract, and after stabilization, the electrical conductivity value was displayed on the conductometer screen. Three readings were performed for each sample analyzed. **Color analysis** was performed by using Konika Minolta CR 400 colorimeter (Konica Minolta, Tokyo, Japan). The samples were introduced in a 20 mm cuvette and measured in a white spectrum. In order to establish the results, three readings were performed. The measurements were displayed in \(L^{*}\) (light-dark spectrum, from 0 = black to 100 = white), \(a^{*}\) (green-red spectrum; \(-a\) = green, \(+a\) = red), \(b^{*}\) (blue-yellow spectrum; \(-b\) = blue, \(+b\) = yellow) and \(\Delta E\) (total change in the color of samples) values [9; 39; 41].