Citrus Harvesting, Quality, & Maturity by Cindy Fake UCCE

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

2. Citrus Harvesting, Quality, & Maturity
1. Citrus 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,
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. Citrus 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%
2. Coloring: typical of the variety
>1/3 of fruit surface
3. Sugar: Acid ratio
TSS:1% acid
Moderate Maturity
• >8% Total Soluble Solids (°Brix):1 % acids
– 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. 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. Defects: Misshapen Fruit

14. Defects:
Rind Breakdown and Decay/Rot

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

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

17. Best Pre-Harvest 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. Best Harvest Practices
for High Quality Fruit

22. 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 rind:
– Clip fingernails or wear gloves
– Pour fruit gently into container
– Do not overfill containers

23. 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

24. 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

25. 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.

26. 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

27. 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

28. 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

29. 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

30. 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

31. • 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
Titratable Acidity (TA)

32. • 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!
Sugar: Acid Ratio (TSS:TA)

33. 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.

34. Harvesting for Quality
Thank you!
Cindy Fake
University of California Cooperative Extension
October 2012