## 4 Discussion  
The results presented in Table 1 provide valuable insights into the impact of curative applications of individual and combined EOs on the terpene composition of apples, subsequently influencing their VOC profile. These findings are not only fascinating but also in line with previous research in the field. The underlying mechanism for terpene compositional changes is hypothesized to involve enzyme activation and metabolic pathway modulation in response to essential oil treatments, potentially triggered by the stress response of apple tissues to antimicrobial compounds. Notably, this study reveals that different EO treatments significantly affect the concentrations of various terpen in apples. For example, \(\alpha\)-Pinene, recognized for its pine-like aroma, exhibited its highest concentration in the Fun+Thy+Cin+Eug treatment, indicating that specific combinations of EOs can enhance the production of this compound (Table 1). This discovery supports earlier research [18] that explored the potential of EO combinations to influence terpene production in plants. Similarly, the elevated levels of \(\beta\)-Pinene, known for its woody and earthy aroma, in the Fun+Thy+Cin+Eug treatment further underscore the capacity of EOs to impact the terpene profile of fruits, as suggested by [19]. Phellandrene, responsible for a minty and citrusy aroma, demonstrated notable increases in the Fun+Thy+Cin+Eug treatment, consistent with previous findings [20] highlighting the role of EOs in enhancing phellan  
Figure 2: CDP 25, 50, 75 values (\({}^{\circ}\)C, X \(\pm\) SE, n = 54) detected in volatile organic compounds of essential oils applied to apples (mCDP, \(p\leq\) 0.01). drene production in plants. The elevation of D-Limonene levels in the Fun+Thy+Cin+Eug treatment is consistent with existing literature [21], underscoring the potential of EOs to stimulate D-Limonene production in fruits. On the other hand, D-Limonene, with its zesty, citrus-like aroma, is a common terpene in citrus fruits. Neral, contributing to a lemony aroma, showed the highest concentration in the Fun+Cin+Eug treatment (Table 1), in line with [22], which suggests that certain EO combinations may influence near concentrations in plants. This result has implications for enhancing the fruity scent of apples. Moreover, geraniol, known for its rose-like and fruity aroma, exhibited significant variation across treatments, with the highest concentration in Fun+Thy+Cin+Eug (Table 1). This aligns with the findings of [23], which explored the enhancement of geraniol levels through essential oil treatments, underlining its potential to positively affect the overall scent of apples. E-Nerolidol, contributing a sweet, woody scent, was found in higher concentrations in the Fun+Thy+Cin+Eug treatment (Table 1), aligning with the general understanding that essential oils can influence the presence of E-Nerolidol in plants, as suggested by [24]. Cedrol, which adds a woody and earthy fragrance, exhibited variations in concentrations among treatments, with the Fun+Thy+Cin+Eug group having the lowest levels (Table 1). This consistency with earlier studies [23; 25] highlights the influence of essential oils on ecdrol production and its potential to contribute to the aroma profile of apples. Lastly, geranic acid, with its rose-like aroma, showed the highest concentration in the Fun+Cin+Eug treatment (Table 1), in agreement with prior research [26] that indicates how specific essential oil treatments can enhance the presence of geranic acid in fruits. Our previous study investigating the protective effect of essential oils determined that the group with the highest terpene content was Thy+Eug+Fun [12]. However, our study investigating the curative effect of essential oils determined that the group with the highest terpene content was Fun+Thy+Cin+Eug. These findings show the potential differences between the protective and curative effects of essential oil combinations of terpene content.