## 2 Results  
### Effects of Different Calcium Preparation Treatments on Browning of Fresh-Cut Apples  
Figure 1a illustrates that the apple epidermal cells treated with CK and T1 are not uniformly colored, have irregular sizes, and are not densely grouped. In contrast, the epidermal cells treated with T2 exhibit consistent cell size, minimal cell gaps, a tight arrangement, and uniform staining. Following a new cut, the degree of browning varied among the apples, with the T2 treatment showing superior color (Figure 1b). The L values for CK, T1, and T3 treatments significantly decreased after cutting, dropping by 13.96%, 12.02%, and 11.58%, respectively. However, the L value for the T2 treatment showed a smaller decrease, dropping by 7.75%, indicating minimal browning. The negative L values for all treatments suggest a reddish hue in the newly cut flesh. Specifically, the flesh treated with CK had a reddish hue, while the other treatments did not show substantial changes. Additionally, there was no discernible difference in the b value between the pre- and postcut apples (Table 1). Overall, the T2 treatment effectively inhibited browning in freshly cut apples. Figure 1: Changes in color difference after fresh-cutting of apples in different calcium preparation treatment groups. (**a**) Epidermal cells of Starkrimson apples, bars correspond to 20 μm. (**b**) The degree of browning of Starkrimson apples, bars correspond to 5 μm. Effects of Different Calcium Preparation Treatments on Hardness, Cellulose Content, and Pectin Content of Fresh-Cut Apples  
As shown in Figure 2a, the hardness of the fruit continuously decreases after fresh-cutting. The hardness decreases slowly from 0 to 9 days and significantly from 9 to 12 days. The hardness difference between treatments is significant at 12 days after fresh-cutting. The T2 treatment maintains a relatively high hardness of 0.269 kg, which is 35.71% higher than of the CK treatment, while that of the T3 treatment is 20.78% higher than that of the T1 treatment. This indicates that the T2 treatment is beneficial for maintaining the hardness of the fruit after fresh-cutting. As seen in Figure 2b, the cellulose content of the fruit tends to stabilize after fresh-cutting. The cellulose content of the T2 treatment is consistently at the lowest level, reaching its peak on the 12 th day, which is 14.88% lower than that of the CK treatment. This demonstrates that the sorbitol-chelated calcium treatment significantly inhibits the increase in cellulose content in fresh-cut fruits. As presented in Figure 2c, the content of soluble pectin gradually increased during the softening process of the apple after fresh-cutting, while the original pectin and total pectin contents gradually decreased. There were no significant changes from 0 to 6 days after fresh-cutting, but significant changes occurred from 6 to 12 days. On the 12 th day, the pectin content of each treatment was significantly different. The soluble pectin content of the T2 treatment was 0.48%, which was 21.31% lower than that of the CK treatment. However, the original pectin content was up to 1.21%, which was 36% higher than that of the CK treatment. The original pectin ensures the fresh-cut hardness. Between 0 and 6 days after fresh-cutting, the T2 treatment had no significant effect on pectin content, but the regulatory effect was significant from 9 to 12 days. This indicates that the sorbitol-chelated calcium treatment had a noticeable inhibitory effect on the conversion of original pectin into soluble pectin after fresh-cutting, mainly occurring in the middle and late stages of fresh-cutting.