This document discusses best practices for harvesting high quality mandarin oranges. It outlines factors that influence mandarin quality like maturity, sugar to acid ratio, and appearance. Good production practices are recommended like pruning, pest management, and fertilization. Proper harvesting techniques like picking dry fruit gently and sorting are emphasized. Maturity is assessed through juice content, brix, and acidity tests. Maintaining quality through proper storage, packing and meeting market standards is key to receiving best prices.

1. Harvesting Quality Mandarins
Cindy Fake
University of California Cooperative Extension
October 2012

2. Mandarin Harvesting, Quality, & Maturity
1. Mandarin Quality
• Factors & Standards
2. Field Practices
• Growing practices that promote quality
• Harvesting practices
3. Assessing Maturity & Quality
• Maturity tests

3. To receive the best prices in markets,
Georgian mandarins must be:
• Grown using good practices to produce good
tasting fruit of the right size
• Picked at maturity, using good harvest practices
• Free of major cosmetic defects
• Able to surpass minimum maturity standards for
juice content and sugar to acid ratio (TSS:TA)
• Packed and stored properly
to maintain quality

4. Terminology
• °Brix = “sugars” = Total Soluble Solids (TSS)
• Acidity = titratable acidity, Total Acidity (TA),
not the same as pH
• Maturity = having completed natural growth &
development
• Minimum maturity = standards fruit must
reach before treatment or shipping
• Defect = visual damage, such as cuts,
scars, dirt, decay or other foreign matter

5. Mandarin Fruit Quality Factors
• Maturity
• Sugars/TSS (total
soluble solids ): acid
ratio
• Juice content
• Firmness
• Appearance: freedom
from defects or rot
• Color : 75% of surface
• Size
• Shape
• Peel thickness
• Ease of peeling
• Seed content
• Flavor or taste

6. Quality & Maturity Standards
EU standards – Minimum maturity
1. Minimum juice content:
33% Mandarins (except Clementines)
2. Coloring: typical of the variety
>1/3 of fruit surface
3. Sugar: Acid ratio
Satsumas > 6.5% TSS:1% acid - too low for consumer!
California Legal Maturity
• 8% Total Soluble Solids (°Brix):1 % acids – still too
low for consumer!
– Sugars rise as mature, acids decline

7. Quality & Maturity Standards
EU standards – Minimum maturity

8. Why is Maturity Important?
• Immature fruit is subject to
– Shriveling
– Mechanical damage
– Physiological disorders
– Shorter shelf life
• Sugars are preservatives and also act like antifreeze
• Taste is important to consumers:
• Immature citrus have high acid and low sugars, and
taste sour

9. When is fruit mature enough to pick?
• Color: at least1/3 of fruit must be properly colored
• No longer rock hard; softening
• Fruit “gives” with finger pressure
• Peel has “give” = slightly loose
• Taste may still be slightly tart in early season, but
must be “sweet-tart” so is palatable
• Early picking should be
“picked to color” AND taste!

10. Quality Standards: Standard Pack
• Fruit fairly uniform in size
• EU minimum size =43 mm, 10% tolerance in size
range
• Packed in boxes or cartons and arranged according
to the approved and recognized methods
• Tightly packed and well filled but no “excessive
or unnecessary bruising” because of overfilling
• Container shall be at least level full
at time of packing

11. Mandarin Defects: rough or thick skin

12. Consequences of Poor Cultural Practices
• Excess water and/or N =>
– Lack of flavor
– Puffiness
– Delayed maturity
– Short shelf life
• Water stress, irregular or inadequate
water
– dry sections, bitter or sour flavor

13. Mandarin Defects: Misshapen Fruit

14. Mandarin Defects:
Rind Breakdown and Decay/Rot

15. Defects: dirt or foreign material:
sooty mold & scale honeydew

16. Mandarin Defects: Insect & Mite Damage
California red scale Citrus thripsRust mite damage

17. Best Production Practices
for High Quality Fruit

18. Best Production Practices for High Quality Fruit
Timely pruning
• Open up canopy to increase light & air
– Reduces scale pests and sooty mold
– Increases inside fruit which is protected
from hail
• Prune out overly vigorous branches that
produce ugly fruit (gourmands )
– Usually produce unattractive fruit
– Rough, misshapen fruit
– Thick skins
– Overly large fruit
• Prune out dead or crossing branches
that may damage fruit

19. Best Production Practices for High Quality Fruit
• Use mulch or compost to keep
tree roots healthy
• Do not dig soil around tree roots
• Use fertilizer to keep trees healthy and
productive
• Mature tree needs 0.2-0.5 kg actual Nitrogen per
year; depending on size of tree
• Reduce N applications after spring growth flush
• Stop N fertilization in July
• Too much N late in season leads to puffiness &
ugly fruit

20. Best Production Practices for High Quality Fruit
• Prevent or manage pests that affect
fruit quality
• Prevent diseases such as Citrus scab or
Brown rot before they happen
• Manage insect and mite pests through
appropriate sprays and encouraging
natural enemies

21. Good Harvesting Practices
• Pick DRY fruit
– Wet fruit is more easily bruised as
cells are swollen with water
– Wet fruit promotes fungus which may
cause decay
• Handle fruit as gently as possible
• Prevent damage to mandarin rind:
– Clip fingernails or wear gloves
– Pour fruit gently into container
– Do not overfill containers

22. Good Harvesting Practices
• Always cut fruit from tree
• Use sharp clippers and clip
stem as short as possible
These long stems will damage other fruit
These short stems will
minimize damage to other fruit

23. Good Harvesting Practices
• Cut and remove diseased fruit first
so fungal spores don’t scatter
• Do not pick fruit off the ground
• If branches are heavy with fruit,
prop them up off the ground at
least 1 month before harvest
• Sanitary practices
– Clean hands
– Use hand cleaner after touching
infected fruit
– Wash hands after using bathroom

24. Sorting Practices
• Do not expect to sell all your fruit – sort for quality!
• Cull any rind defects that will shorten shelf life
• Keep cull pile away from trees or packing area
• Handle diseased fruit carefully so spores do not spread
• Clean hands & equipment after any infected fruit
• Keep to a similar size range in each container
vs.

25. Storage Practices
• Only store DRY fruit
• Optimum temperature 7.2°C
• Optimum relative humidity
(RH) = 85-90%
• Cool storage with airflow
• Avoid build up of ethylene
• Maximum 20-25 cm depth of
fruit for storage

26. Packing Practices
• Do not squeeze the fruit into the box
• Do not stack bagged fruit more than 3 or 4 high
• Do not pack too much ahead of time
• Fingernails! - Wear gloves

27. Maturity Testing
• Important objective measures
of fruit maturity
• Must meet standards for exports or for high end
markets
• Fruit is judged by color standards and
• Maturity Testing : 3 major tests:
• Juice Content (%)
• Sugar: Acid Ratio, based on:
• Total Soluble Solids (TSS) = Sugars
• Titratable acidity (total acids)
• Most buyers will want to taste as well

28. Juice Content = % juice
• Weigh 10 mandarins, record weight.
• Weigh the juice container,
record weight.
• Juice the mandarins. Strain juice into container.
• Weigh the juice, then subtract the weight of the
container.
• Juice %=
Weight of juice ÷Total fruit weight x 100

29. Total Soluble Solids (TSS)
• °Brix, TSS = measurement of
sugar content or sweetness
• Measured with temperature-compensating
refractometer
• Be sure the glass surface is clean & dry
• Place a few drops of juice on the glass
• Close the lid
• Look through the eyepiece and read where the juice
sits on the scale
• Clean and dry the refractometer immediately

30. Titratable Acidity (TA)
• Critical measurement for Georgian
mandarins
• Quality issue with fruit is high
acidity, not low sugars
• Measure of total acidity of the juice
• Not the same as pH
• Measured by using a measured amount of a base
(NaOH) and a color indicator to bring the juice
solution to neutrality
• The acidity is then calculated with a standard formula
ml NaOH x 0.064 = citric acid concentration

31. Sugar: Acid Ratio (TSS:TA)
• Sugar: Acid Ratio is the major component of
mandarin flavor
• Early in season, TSS:TA is low because sugar is low
and acid is high
• As fruit ripens, sugars increase and acid decreases
• Sugar: Acid ratio = °Brix ÷ Citric Acid Concentration
• Consumer preference for sugar content varies with
markets, so KNOW your market!

32. Points to remember
• Quality fruit is mature fruit
• Quality standards are based on
size, color, and freedom from defects
• To the consumer, quality is all about flavor!
• Flavor preferences always favor sweetness
• Maturity standards are based on color, juice content,
sugar content and acid content.
• Good growing practices and good harvesting practices
will bring higher prices for fruit.

33. Questions?
Thank you!