Submitted to: International Journal of Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 1995
Publication Date: N/A
Interpretive Summary: Acceptable, effective quarantine treatments involving methyl bromide, heat and cold for pest disinfestation and quality maintenance of fruit commodities are essential for international trade. These treatments often cause damage to the rind of lemon, greatly reducing market value. We studied the release of oil from lemons following hot water or cold treatments to determine if released oil might be involved in causing rind injury. Hot water treatments for 10 min at 48-58C caused fruit injury and were related to greater release of oil from the rind. Cold treatment at 1C for four to five weeks also caused rind injury and a greater amount of oil release. Information regarding the oil release associated with rind injury due to hot water or cold will be useful for predicting and developing quarantine treatments that are less injurious to lemons.
Volatile emanation from whole lemon fruits was determined following hot water or cold treatments to examine the relationship between liberation of essential oils from the oil glands and the phytotoxicity of these treatments. Headspace analysis indicated that B-pinene, d-limonene and y- terpinene were the most abundant volatiles, composing 8, 42 and 21%, respectively, of the total amount. Due to its abundance, d-limonene was selected as the essential oil component to be quantified following treatment. Hot water treatments for ten minutes at 48C and below were non- injurious to both yellow and green fruit, with injury in the form of lesions on the rind beginning to occur at 50C (yellow) and 52C (green), and increasing in severity up to 58C, the highest temperature tested. D- limonene emanation increased correspondingly with increasing injury. Green lemons were injured more severely than yellow and tended to release more d- -limonene, especially at higher temperatures. Curing at 15 and 20C for 6 d acted to reduce injury to green lemons treated with hot water at 54C, but was ineffective at 58C. No significant differences were present in d- limonene emanation between cured and non-cured fruit at 54 or 58C. Storage of fruit for 18 d at 7C following hot water treatment at 58C doubled the amount of d-limonene detected during measurement, indicating the increased release of d-limonene as rind damage developed. Cold treatment at 1C for four to five weeks, followed by one week at 20C, caused the development of chilling injury lesions on the rind. In comparison to lemons stored for the same periods of time at a non-injurious temp. of 7C, chilling-damaged fruit released d-limonene in far greater amounts. Overall, injury due to hot water or cold treatments was associated with increased d-limonene release.