Browning in lychee fruit and leaves is a common issue. Understanding the reasons behind this discoloration helps in addressing the problem effectively. This article clarifies what brown lychee signifies and provides insights into preventing and managing it.
What Brown Lychee Fruit Means
Brown lychee fruit indicates a change in the pericarp, or outer skin, ranging from slight discoloration to a darkened, shriveled appearance. The vibrant red or pink hue of fresh lychees comes from anthocyanin pigments; their degradation leads to browning. Fresh lychees are firm but yield slightly to pressure, while overly soft or mushy fruit suggests advanced deterioration.
Is it Safe to Eat?
Superficial browning of the lychee skin, often from air exposure or cool, dry conditions, does not mean the fruit is unsafe to eat. The flesh inside might still be sweet and juicy, especially if browning is minor and the fruit remains firm. However, if browning is accompanied by a sour or fermented smell, a very soft or mushy texture, or visible mold, the fruit is likely spoiled and should not be consumed. Flesh breakdown, becoming soft and losing turgidity, can also occur after prolonged storage or over-maturity.
Why Lychee Fruit Turns Brown
Lychee fruit browning is a complex process influenced by factors both after harvest and during growth. The fruit’s attractive red color is highly susceptible to change, rapidly turning brown.
Post-Harvest Factors
After harvest, enzymatic oxidation is a primary cause of browning. Enzymes like polyphenol oxidase (PPO) and peroxidase (POD) react with phenolic compounds and anthocyanin pigments in the pericarp when cell compartmentalization is lost, forming brown polymers. Dehydration, or water loss, also contributes to skin browning. Chilling injury, from suboptimal low temperatures, manifests as pericarp browning and increased susceptibility to decay due to membrane damage. Mechanical damage, such as bruising or cracking during handling, can accelerate browning by disrupting the skin and exposing the fruit’s interior to air and enzymes.
Environmental and Growing Factors
While on the tree, environmental conditions can lead to browning. Sunburn causes localized discoloration on the fruit’s skin, especially in areas exposed to intense direct sunlight. Nutrient imbalances in the soil can affect fruit quality and color. Fungal diseases, such as Anthracnose or Spots disease, cause dark, irregularly shaped patches on the fruit, reducing its commercial value. Pests can also damage the fruit’s rind, creating entry points for pathogens and leading to localized browning or decay.
Preventing Brown Lychee Fruit
Preventing lychee browning involves careful handling and appropriate storage conditions. These practices minimize factors that trigger discoloration and spoilage.
Proper Handling and Storage
To maintain freshness and color, store lychees in a refrigerator. Placing them in a perforated plastic bag or a container with ventilation prevents excess moisture buildup and protects against dry air that causes browning. The optimal storage temperature is between 2 to 5°C (36 to 41°F) with 90-95% relative humidity. Under these conditions, lychees maintain quality for several weeks, longer than at room temperature. Avoiding direct exposure to ambient air is important, as the skin rapidly browns.
Purchasing and Selection Tips
Selecting fresh lychees at the market prevents premature browning. Choose fruit with vibrant red or pink skin, indicating ripeness and freshness. The skin should feel slightly bumpy but not overly dry, and the fruit should be firm, not soft or mushy. A sweet, floral aroma indicates quality.
Avoid lychees with green patches, dark brown spots, cracks, or leaking juices, as these suggest the fruit is unripe, overripe, damaged, or spoiled. Since lychees do not ripen after being picked, selecting ripe fruit at purchase is important.
When Lychee Tree Leaves Turn Brown
Browning leaves on a lychee tree indicate underlying health issues, distinct from fruit browning. Addressing these concerns helps maintain a healthy tree.
Common Causes for Leaf Browning
Leaf browning on lychee trees stems from several factors. Watering imbalances are a frequent culprit: both underwatering (leading to drought stress and dried-out leaves) and overwatering (causing root rot and hindering nutrient absorption) result in brown leaf tips or discoloration. Nutrient deficiencies, such as a lack of iron or potassium, can cause leaves to yellow or brown, particularly at the tips or edges.
Over-fertilization can lead to “fertilizer burn,” where excessive salts prevent water absorption, causing leaf edges to brown. Pests like mites or scale insects can damage leaves, leading to discoloration. Fungal diseases such as Phyllosticta leaf spot or Lychee leaf necrosis cause brown or black lesions and can lead to defoliation. Environmental stresses, including strong winds, extreme temperatures (especially cold), or excessive direct sunlight, can also cause leaf burn and browning.
Solutions for Healthy Lychee Trees
To resolve browning leaves, adjust watering practices. Allow the soil to dry slightly between waterings to prevent root rot, and ensure deep watering during dry periods. For nutrient issues, a balanced, general-purpose fertilizer for fruit trees can address deficiencies, but avoid over-fertilization.
Protect young or potted lychee trees from strong winds to prevent windburn, and provide afternoon shade in hot climates to mitigate sunburn. Managing pests and diseases may involve specific treatments, such as horticultural oils for insects or fungicides for fungal infections, combined with cultural practices like improving air circulation and removing affected foliage. Regular inspection allows for early detection and intervention, promoting overall tree health.