## 3 Results and Discussion
### Physicochemical Properties
#### 3.2.6 Retrogradation  
Retrogradation is defined as a process by which amylose and amylopectin molecules reassociate through hydrogen bonding, consequently developing a three-dimensional network structure [78]. Figure 3 shows the retrogradation curve for rice flour samples.  
Table 2 presents the retrogradation profiles of the control and treatment samples. The T\({}_{\text{o}}\) range is between 41.80 \({}^{\circ}\)C and 50.79 \({}^{\circ}\)C. The highest T\({}_{\text{o}}\) was exhibited by the Bario Tuan variety (50.79 \({}^{\circ}\)C), followed in descending order by Bario Merah Sederhana (45.90 \({}^{\circ}\)C); Bario Adan Halus (44.50 \({}^{\circ}\)C); Bario Celum (42.65 \({}^{\circ}\)C); and the control sample, TQR (41.80 \({}^{\circ}\)C). There was a significant difference (\(p<0.05\)) in the T\({}_{\text{o}}\) of Bario Tuan compared with other varieties. Moreover, the T\({}_{\text{p}}\) and T\({}_{\text{f}}\) ranged between 44.36 \({}^{\circ}\)C and 56.15 \({}^{\circ}\)C, and between 48.71 \({}^{\circ}\)C and 61.25 \({}^{\circ}\)C, respectively. The highest T\({}_{\text{p}}\) was shown by Bario Tuan (56.15 \({}^{\circ}\)C), whereas the lowest T\({}_{\text{p}}\) was showed by the control sample, TQR (44.36 \({}^{\circ}\)C). Generally, there are no significant differences (\(p>0.05\)) shown by all varieties, except TQR, which had the significantly (\(p<0.05\)) lowest T\({}_{\text{p}}\). On the other hand, Bario Merah Sederhana (61.25 \({}^{\circ}\)C) had the highest T\({}_{\text{f}}\), whereas the lowest was presented by TQR (48.71 \({}^{\circ}\)C). Similarly, all varieties showed no significant difference (\(p>0.05\)), except the TQR variety. In addition, the gap between temperature range (T\({}_{\text{f}}\)-T\({}_{\text{o}}\)) can be determined and related to the length of the double helix, so a wider endotherm suggests a wider range of double-helical lengths [79]. The \(\Delta\)H\({}_{\text{ret}}\) range was between 0.13 J /g and 0.87 J/g. The highest \(\Delta\)H\({}_{\text{ret}}\) was exhibited by Bario Celum (0.87 J/g), and the lowest was the control sample, TQR (0.13 J/g). A high value of \(\Delta\)H\({}_{\text{ret}}\) means more energy is required to break down the reassociated amylopectin formed during the storage period, indicating a higher retrogradation process [80]. Thus, Bario Celum (0.87 J/g) and Bario Adan Halus (0.76 J/g) exhibited significantly (\(p<0.05\)) higher retrogradation processes compared with the other varieties.  
According to [PERSON] et al. [81], amylose content is one of the significant factors influencing starch's retrogradation. Nonetheless, the highest amylose content exhibited by Bario Tuan and \(\Delta\)H\({}_{\text{ret}}\) of Bario Tuan (0.19 J/g) was lower than that in Bario Adan Halus (0.76 J/g). This indicates that the retrogradation enthalpy was less pronounced in Bario Tuan even though the amylose content was high within this variety. This possibly results from the higher fat content within Bario Tuan (2.45%) than within Bario Adan Halus (0.16%), which might develop starch-lipid complexes, consequently decreasing the amount of starch retrogradation. In general, lipid reduces the movement of amylose due to the development of complexes constructed between amylose and lipid [82]. The starch-lipid complex is developed through a hydrophobic effect due to hydrophilic and hydrophobic groups in lipids. The latter group leads the lipids to move closer to the internal hydrophobic  
Figure 3: Retrogradation curve of rice flour samples for TQR, Bario Adan Halus, Bario Tuan, Bario Celum, and Bario Merah Sederhana.  
cavities of amylose [81]. On the other hand, factors such as small molecular sugar and non-polysaccharides, salt ions, granule size, and the ratio of amylose and amylopectin within starch granules could influence the retrogradation profiles [83; 84; 85; 86].