*4.5. Correlation Analysis*

Negative correlations were found between superficial scald and both RSA and TPC, which may indicate minimal involvement of phenolic compounds in superficial scald induction. These results agree with Shaham et al. [57], who observed a fluctuation and little change in phenolic compound constitution and attributed the development of superficial scald to antioxidant enzyme activity. The accumulation of oxidative compounds of αfarnesene and MHO has been associated with superficial scald induction [6,7]. However, in this study, correlation analysis suggested that other volatiles, such as conjugated trienols (CTols) and antioxidants (ascorbic acid and tocopherol), not quantified in this study, may be responsible for the development of superficial scald in 'Granny Smith' apples [8,9,60].

#### **5. Conclusions**

This study showed that storing fruit under low oxygen controlled atmosphere technologies (RLOS and DCA-CF) at 0 ◦C can inhibit the development of superficial scald on 'Granny Smith' apples in a season of low superficial scald potential. Applying RLOS and DCA-CF maintained some internal quality parameters for up to 10 months of storage at 0 ºC and after a simulated 6 w of shipment and handling period plus 7 d shelf life (20 ◦C). This study demonstrated that both RLOS and DCA-CF inhibited superficial scald in 'Granny Smith' apples, possibly suppressing α-farnesene oxidation. The results from this study confirmed the hypothesis that MHO causes superficial scald; however, other underlying mechanisms may have substantial contributions to the induction of superficial scald. This study also showed that RLOS and DCA-CF storage technologies maintain the antioxidant status of 'Granny Smith' apples, which is important in quality preservation. This study also highlighted that, while phenolic compounds possibly contribute to the inhibition of superficial incidence, their role varies significantly with harvest season. Further studies that focus on the emission of other volatiles such as conjugated trienes during storage, lipid peroxidation, and the relationship of superficial scald with other metabolites can elaborate more on the mechanism of action of RLOS technology. Additionally, the possibility of RLOS technology being used in combination with 1-MCP, currently applied on 'Granny Smith' apples, presents an innovative technology that could be investigated on 'Granny Smith' apples and other cultivars.

**Author Contributions:** Conceptualization, O.A.F. and U.L.O.; methodology, T.G.K., O.A.F., and U.L.O.; software, T.G.K. and O.A.F.; formal analysis, T.G.K. and O.A.F.; investigation, T.G.K.; resources, O.A.F. and U.L.O.; writing—original draft preparation, T.G.K., writing—review and editing, O.A.F. and U.L.O.; supervision, O.A.F. and U.L.O.; project administration, U.L.O. and O.A.F.; funding acquisition, U.L.O. and O.A.F. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors are grateful to the Agricultural Research Council of South Africa, Postharvest Innovation Programme (PHI) and Hortgro Science for financial support.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Restrictions apply to the availability of these data. Data are available from the authors with the permission of funder.

**Acknowledgments:** This work is based on the research supported wholly or in part by the National Research Foundation of South Africa (Grant Numbers: 64813). Research reported in this publication was supported in part by the Foundation for Food and Agriculture Research under award number— Grant ID: DFs-18-0000000008.

**Conflicts of Interest:** The opinions, findings and conclusions or recommendations expressed are those of the author(s) alone, and the NRF accepts no liability whatsoever in this regard.
