Effect of vacuum impregnation with melatonin, γ‐aminobutyric acid, and oxalic acid on chilling injury and quality of carambola

Carambola is a nutrient‐rich tropical fruit that ripens and spoils rapidly at ambient temperature, making low‐temperature storage a preferable method to address this problem. Unfortunately, carambola suffered a chilling injury when stored at low temperatures. Carambola was vacuum impregnated with melatonin (MT), γ‐aminobutyric acid (GABA), and oxalic acid (OA) to mitigate chilling injury and improve its quality during cold storage. Carambola fruits were stored at 4 °C for 28 days and analysed every 7 days. Weight loss, firmness, physicochemical properties, phenolic content, flavonoid content, and proline content were assessed. MT‐treated carambola has the highest firmness, 146.31 g and lowest weight loss, 1.53% in comparison to others by the end of the storage period. Visual observations showed that MT‐treated carambola ripened evenly, without any chilling injury symptoms and decay was also delayed, whereas OA‐ and GABA‐treated carambola started to decay on day 28. Instead of degrading, phenolics and flavonoids were retained with 6.10% and 12.67% increase when compared to the initial level. GABA‐treated carambola can also retain its phenolic and flavonoid content; meanwhile, OA‐treated carambola can only retain its phenolic content. Therefore, MT can be applied to mitigate chilling injury and maintain the quality of carambola.