## 3 Results
### Effects of Different Treatments on Nutritional Qualities of Blood Orange Fruit  
As shown in Figure 3, bagging and NO treatment increased the content of soluble sugar (SSC) in fruits (Figure 3A). The glucose content of the bagged fruit increased by 1.59 times, compared to the control. However, NO treatment inhibited the accumulation of glucose, which was the same result as the control treatment (Figure 3B). NO treatment increased the fructose content, which was 2.52 times that of the control (Figure 3C). Moreover, NO treatment increased the sucrose content in fruit (Figure 3D). However, the contents of fructose and sucrose were similar between the bagged fruit and the control. NO treatment increased the sugar-acid ratio and VC content of fruits (Figure 3E,F), and the sugar-acid ratio of fruits treated with NO was 1.48 times higher than that of the control.  
Figure 2: Effects of different treatments on the physical properties (single fruit weight, fruit shape index (size), firmness, water content, and pulp color) (**A**), aroma, and flavor compounds (tittatable acids (sourness), total soluble solids (sweetness), limonene content (aroma), naringin content (bitterness), and tannin content (astringency)) (**B**). Relative value = measured value/max value \(\times\) 100%. All measured values are shown in Table S1.  
NO treatment enhanced the contents of threonine, phenylalanine, glutamine, arginine, tyrosine, serine, glycine, asparagine, lysine, tryptophan, tryptophan, glutamic acid, and histidine (Figure 4). Among them, the histidine content in the fruit increased most significantly (by 1.09 and 3.23 times, respectively) after bagging and NO treatment. In the bagged and NO-treated fruit, the contents of leucine, isoleucine, aspartic acid, methionine, valine, proline, and alanine were reduced (Figure 4). In particular, the content of proline in the bagged and NO-treated fruit was dramatically reduced to 158.65 \(\upmu\)g/g and 243.77 \(\upmu\)g/g, respectively, less than that of the control. Moreover, cystine was not detected in the fruit.  
The contents of oxalic acid, formic acid, malonic acid, malonic acid, a ketovalerate, lactic acid, citric acid, and succinic acid increased in the bagged and NO-treated fruit (Figure 5). Notably, the content of citric acid was 2.34 and 2.76 times that of the control, and the content of succinic acid was 1.93 and 1.99 times that of the control, respectively. In addition, the contents of malic acid, oxalic acid, formic acid, and ketovalerate also increased in the fruit. However, the content of malonic acid and lactic acid increased in NO-treated fruit but decreased in bagged fruit, similar to that of the control. Additionally, NO treatment reduced the content of acetic acid in fruit (Figure 5).  
Figure 3: Effects of different treatments on the soluble sugar content (SSC; **A**), glucose content (**B**), fructose content (**C**), sucrose content (**D**), sugar–acid ratio (**E**), and vitamin C (VC) content (**F**) of blood orange fruit pulp. Error bars show standard deviations (\(n=3\)). Different lowercase letters indicate significant differences at 0.05 (\(p<0.05\)) levels.  
The content of Ca, Fe, Zn, and Ni increased in the bagged and NO-treated fruit (Figure 6), and the Fe content increased the most, by 1.27 and 1.75 times, respectively. The Ca content increased by 1.10 and 1.26 times in the bagged and NO-treated fruit, respectively, compared with the control. In addition, the content of N and Mg decreased, and the content of N decreased substantially. The contents of P and Mn also decreased in bagged fruit. Interestingly, there was no significant difference in the Cu content between different treatments (Figure 6).  
Figure 4: Heatmaps of amino acids in blood orange fruits after different treatments. The bar represents the relative value (measured value/max value \(\times\) 100%).  
Figure 5: Heatmaps of organic acids in blood orange fruits after different treatments. The bar represents the relative value (measured value/max value \(\times\) 100%).