This week NAREI in Focus will look at the production of tangerine. Tangerines (Citrus reticulata) are the second most important type of citrus grown in Guyana. Most of the tangerines produced in the country are seeded fruit, with Dancy being a leading cultivar.
The tangerine fruit has a short shelf life compared to other types of citrus. Nearly all the tangerines produced in Guyana are sold as fresh fruits in the domestic fresh market, although small volumes are exported to Barbados and Canada.

Harvest Maturity Indices
There is no dependable non-destructive method of determining the maturity of tangerine fruit. The number of days from flowering is a sizeable period and is not a reliable index of harvest maturity. Also, fruit size is not always linked with maturity. The most common nondestructive method of assessing fruit maturity is based on peel colour. Tangerines are mature and ready for harvest when 50Yo of the peel surface has started to turn yellow.
A commonly used method for determining fruit maturity is an assessment of the fruit’s juice characteristics. Random samples of fruit of similar size are obtained and measured for the percent of soluble solids (percent SS), titratable acidity (TA), and the percent SS:TA ratio. To reduce inconsistency, the juice sample should be obtained from a minimum of l0 randomly selected fruit. Each fruit should be cut in half, squeezed, and filtered to clarify the juice. The combined juice sample should have a SS:TA ratio of 6.5 or higher. Soluble solids content is determined by squeezing a few drops of juice on a hand-held refractometer. A 10 ml (2 teaspoon) sample of filtered juice is titrated with 0.1 N sodium hydroxide to an end point of 8.1. The volume of 0.1 N sodium hydroxide required to reach the pH end point of 8.1 is then multiplied by the factor of 0.0064 to obtain the percent acidity.
Harvest Methods

Tangerine fruit should be carefully harvested by hand using clippers to detach the fruit. The fruit should not be pulled off the tree, as part of the skin tissue will remain attached to the stem, creating a small opening in the peel surface. This is known as ‘plugging’ and it results in an open wound in the skin for micro-organisms to enter and decay. Various styles of clippers or pruning shears can be used, but they should be small enough to prevent worker fatigue. The harvested fruit should be carefully placed into padded field crates, well-ventilated plastic containers, or small picking bags. Avoid rough harvesting practices which cause bruise damage and subsequent fruit decay. Ladders may be needed to facilitate harvesting of fruit borne on tall trees.

The harvested fruit should not be left exposed to the sun. Large non-ventilated synthetic sacks that contain more than 20 kg a lb) of fruit are not recommended as harvest. These sacks do not protect the fruit against compression injury, particularly if they are stacked on top of each other. They also do not allow for release of heat and the tangerines inside will be more likely to decay, especially if the fruit remains in the sack for several days.