# Properties of Different Varieties of Durian
## 2 Materials and Methods
### Determination of Physicochemical Properties  
The immature (young) durians were kept at room temperature until the overripe stage. The maturity of durian was characterized using the following criteria: Immature (young) durian was harvested before mature level 3-5 days, but at this level durian is not consumed, having a hard texture and without any smell. At the mature level durian can be consumed with a firm texture and desirable smell. When mature durian is left for 1-2 days, then it becomes ripe. At this level, durian has a soft texture and a desirable smell. The levels between ripe and overripe (Ripe+) durians are achieved when the ripe durian is left for 1-2 days. This stage of durian had a softer texture and stronger smell than ripe level. In some cases, ripe durian is left for 3-5 days. Durian at this time has a sloppy, mushy texture and odoriferous. This is a standard procedure for durian ripening, taking about 3-5 days from stage to stage, but the duration of the fruit is variable depending on the cultivar and the size of the fruit.  
According to Table 1, the first day of each cultivar from the orchard was in the young stage at 0 day. The mature stage began from Kanyao to Monthong (3-5 days). The ripe stage started from Kanyao to Monthong (5-7 days). The ripe + 1 stage began from Kanyao to Monthong (7-9 days). The overripe stage was found in Kanyao (9 days) and in two other investigated cultivars Chanee and Monthong at 10 days (10 days).  
The pH, acidity, \({}^{\circ}\)Brix and total soluble solids of durian in the ripe stage of three cultivars (Monthong, Chanee and Puangmanee) were determined. The pH, acidity, \({}^{\circ}\)Brix, and total soluble solids of durian in different maturity levels of three slightly different cultivars (Monthong, Chanee and Kanyao) were determined as well in order to recheck the ripe stage of durian harvested in 2018. The pH of the durian was determined by the following method: minced durian pulp (10 g) was mixed with 90 mL of distilled water. The mixture was filtered, and the pH was measured using a digital pH meter [19]. The acidity was measured by titrating the samples of durian with 0.1 N NaOH solution, according to AOAC Method 942.15 [20]. Ten grams of sample were diluted with 75 mL of distilled water. Then, the mixture was homogenized and 2-3 drops of phenolphthalein were added. The mixture was titrated with 0.1 N NaOH until the color of the solution turned pink and remained stable for 30 s. The value of titrated acidity was expressed as g malic acid/100 g wet weight, using the following formula: % acid = [NaOH (mL) \(\times\) molarity of NaOH \(\times\) (0.067) \(\times\) 100]/sample (g), where a milliequivalent factor of 0.067 was used, with the assumption that malic acid is the predominant acid [21]. Total soluble solids (\({}^{\circ}\)Brix) of  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Cultivars**} & \multicolumn{5}{c}{**Maturity Levels (Day)**} \\ \cline{2-6}  & **Young** & **Mature** & **Ripe** & **Ripe + 1** & **Overripe** \\ \hline Monthong & 0 & 5 & 7 & 9 & 10 \\ Chanee & 0 & 4 & 6 & 8 & 10 \\ Kanyao & 0 & 3 & 5 & 7 & 9 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The duration (days) of durian ripening at different maturity levels and cultivars.  
fresh durian pulps were determined by the method of [PERSON] et al. [21]. Minced durian pulp (10.0 g) was mixed with 20 mL of distilled water and filtered. The total soluble solids were measured in the mixture, using a digital refractometer. The total soluble solids (%) value was obtained by multiplying \"Brix values by 3.