Harvesting Quality Citrus

Cindy Fake University of California Cooperative Extension

October 2012

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

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

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

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

Quality & Maturity StandardsEU standards – Minimum maturity1. Minimum juice content:

33%2. Coloring: typical of the variety

>1/3 of fruit surface3. Sugar: Acid ratio

TSS:1% acidModerate Maturity

• >8% Total Soluble Solids (°Brix):1 % acids–Sugars rise as mature, acids decline

Quality & Maturity Standards

EU standards – Minimum maturity

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

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!

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

Defects: rough or thick skin

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

Defects: Misshapen Fruit

Defects: Rind Breakdown and Decay/Rot

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

Defects: Insect & Mite Damage

California red scale Citrus thripsRust mite damage

Best Pre-Harvest Practices for High Quality Fruit

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

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

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

Best Harvest Practices for High Quality Fruit

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

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

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

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.

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

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

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

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

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

• 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)

• 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)

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.

Harvesting for Quality

Thank you!

Cindy Fake University of California Cooperative Extension

October 2012