'Diffuse skin browning' in 1-MCP-treated apples: etiology and systems of control

Membrane Fatty Acids and Physiological Disorders in Cold-Stored ‘Golden Delicious’ Apples Treated with 1-MCP and Calcium Chloride

The present research intents to study skin fatty acids and physiological disorders developed during cold storage in ‘Golden Delicious’ apples treated with 1-MCP and calcium. Harvested fruits were treated with calcium chloride (Ca), 1-MCP (MCP), Ca + MCP or no treatment (control) and then subjected to cold storage at 0.5 °C for 6 months. Fatty acids’ composition, malondialdehyde (MDA) and the physiological disorders bitter pit (BP), superficial scald and diffuse skin browning (DSB) were measured at harvest and after storage plus 7 days of shelf-life at room temperature ≈22 °C. Palmitic acid decreased and linoleic acid increased over time, while oleic and stearic acids had few changes. Generally, unsaturated/saturated fatty acids and MDA increased over the storage period. Treatment with Ca showed that, at the end of the experiment, the lowest MDA values and the highest unsaturated/saturated fatty acids ratio were mainly due to higher linoleic and lower palmitic acids concentrations, which are coincident with less severe BP. There was no clear correlation between the measured fatty acids (palmitic, linoleic, oleic and stearic), unsaturated-to-saturated fatty acids ratio or MDA with chilling skin physiological disorders. Further research is needed to clarify the changes in membrane properties and the effect of some treatments in response to chilling injury during storage.

Maintaining high moisture content of macadamia nuts-in-shell during storage induces brown centres in raw kernels

BACKGROUND

Kernel brown centres in macadamia are a defect causing internal discolouration of kernels. This study investigates the effect on the incidence of brown centres in raw kernel after maintaining high moisture content in macadamia nuts-in-shell stored at temperatures of 30°C, 35°C, 40°C and 45°C.

RESULTS

Brown centres of raw kernel increased with nuts-in-shell storage time and temperature when high moisture content was maintained by sealing in polyethylene bags. Almost all kernels developed the defect when kept at high moisture content for 5 days at 45°C, and 44% developed brown centres after only 2 days of storage at high moisture content at 45°C. This contrasted with only 0.76% when stored for 2 days at 45°C but allowed to dry in open-mesh bags. At storage temperatures below 45°C, there were fewer brown centres, but there were still significant differences between those stored at high moisture content and those allowed to dry (P < 0.05).

CONCLUSION

Maintenance of high moisture content during macadamia nuts-in-shell storage increases the incidence of brown centres in raw kernels and the defect increases with time and temperature. On-farm nuts-in-shell drying and storage practices should rapidly remove moisture to reduce losses. Ideally, nuts-in-shell should not be stored at high moisture content on-farm at temperatures over 30°C.