Short-duration, hot water treatment for the control of chilling injury and postharvest decay in citrus

Karthik-Joseph John-Karuppiah, Mark A. Ritenour, Michael S. Burton, Jeffrey K. Brecht, T. Greyory McCollum

Abstract


Hot water treatments have been studied and used as non-chemical methods to reduce postharvest decay and chilling injury (CI) in fresh citrus fruit. While many studies have been performed in Mediterranean climates, there exists relatively little work evaluating the effects of hot water on Florida grapefruit quality and quality retention during postharvest handling. In current studies, 'Ruby Red' grapefruit dipped in water at 56 or 59 C for 30 s developed 18% or 32%, respectively, less CI after storage at 5 C for 6 weeks plus 1 week at 16 C, compared to fruit dipped at 25 C. The fruit were not washed or coated with shellac and no fungicides were used. Hot water dip treatment (HWDT) had the greatest effect on reducing CI of less CI-sensitive inner-canopy fruit (32%) compared to more CI-sensitive outer-canopy fruit (10%). In a separate experiment, washing and coating the fruit with shellac (no fungicide) immediately after the 30 s HWDT significantly reduced scalding (i.e., hot water injury) by 45% or 37% in fruit treated at 59 or 62 C, respectively, compared to unwashed and uncoated fruit. Fruit treated at 56 or 59 C developed less total decay after 12 weeks of storage at 10 C than did 25, 53 or 62 C-treated fruit. None of the treatments resulted in consistent differences in total soluble solids or titratable acidity in grapefruit. Higher electrolyte leakage and lower peroxidase activity were observed in heat-treated 'Valencia' oranges, but there was no correlation with visible heat injury. HWDT did not affect total phenolics or total protein content of 'Valencia' oranges.

Keywords


citrus paradisi; grapefruit; orange; citrus sinensis; peel scalding; electrolyte leakage; peroxidase activity; total phenolics; total protein; anthracnose; colletotrichum gloeosporioides

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283