Horticultural Productivity and Quality

Do mature fruit or immature fruit show greater responses to harvesting?

Immature fruit. Mature fruit have already stored carbs and reduced respiration and transpiration

True or False: Produce is essentially dead once harvested

False

What processes continue after the produce has been harvested and which affect long term quality?

Transpiration, respiration, softening and metabolising

What kind of tissues exhibit the most dramatic response to harvesting?

Rapidly metabolising tissues such as leafy vegetables

What time of day is best for harvesting?

In the cool of the morning

Why is the early morning better for harvesting?

It’s cooler and therefore the produce metabolism and respiration are lowest

What is oleocellosis?

Skin cell death and discolouration resulting from the release of citrus oil from burst oil cells in citrus fruits

Why might one wait to harvest until the dew is gone?

To reduce fruit turgor at time of harvest

What is the result of harvesting oranges when the fruit is still turgid?

oleocellosis

What effect does terpinolene have on mangos?

It can stain and burn the fruit surface

What is terpinolene?

A compound found in mango sap

What is desapping in mangoes?

a common postharvest operation in many mango cultivars that drains the latex cap from the fruit preventing skin damage and resultant rots and infections

How can sap residue be removed from mango skins?

Specific detergents coated on the fruit followed by water sprays

When are harvest platforms used?

In greenhouses to harvest vegetables such as cucumbers where the plants are trellised

What is the downside to a motorised cherry picker harvest aid?

It’s expensive

How is the harvest method determined?

It depends on the strength of the attachment of the produce organs, the degree of damage that is tolerable, and economic considerations

What kind of harvesting is predominate in most countries?

Hand harvesting

When is mechanical harvesting used?

In regions where labour costs are high in robust, low-unit value, ground crops like potatoes and onions and in processing crops such as peas

What are some examples of mechanical aids to hand harvesting?

conveyers, platforms, flying foxes

What is a flying fox? (Not a bat)

overhead ropeways

What secondary issues might mechanical harvest damage cause?

microbial growth and water loss

What are two examples of devices which help to reduce harvest damage?

deceleration chutes and padded farm trailers

What is a deceleration chute?

Special chutes which slow down produce as they transfer from picking bags to bins

What aspect of in-field postharvest care is key to maximising storage life and quality?

Minimising field heat, often with shade

What is the downside to washing produce?

Contaminated wash water is a carrier of plant and human pathogens

Why do we wash produce after picking?

To remove dirt and debris

What are the three most widespread sanitisers used in packing sheds?

Chlorine, peroxyacetic acid, ozone

What is the most commonly used sanitiser in packhouses?

Chlorine

What forms of chlorine are used in packhouse sanitisation?

sodium or calcium hypochlorite

What is the main advantage of using chlorine sanitisers?

They’re inexpensive and have broad-spectrum effects

What pH does chlorine sanitiser require?

between 6.5 and 7.5

For which two sanitisers does organic matter affect activity?

Chlorine and Ozone

What are the benefits to using an ozone sanitiser?

They’re highly effective, break down to oxygen, and are less sensitive to pH than chlorine

What are the disadvantages of using ozone sanitisers?

Organic matter affects activity, it’s highly corrosive to equipment, it is very volatile and must be made on-site, and can be toxic to people

What are the advantages of using peroxyacetic acid sanitisers?

They’re stable, they work in a broad pH range, and work well in the cold

What are the disadvantages of using a peroxyacetic acid sanitiser?

It’s somewhat corrosive to equipment, difficult to monitor, and more expensive than chlorine

What is another name for peroxyacetic acid?

Paracetic acid

What concentration is paracetic acid used at?

50-80 microlitres per litre

What are some less common packhouse sanitisers?

organic compounds with bioflavanoids and organic acides

gas based sanitisers such as chlorine dioxide

bromo-chlorodimethyl hydantoin

ELECTRICITY ZIP ZAP BACTERIA

What postharvest treatment is often used in conjunction with washing?

Brushing

What is an alternative to mechanical brushing which is also effective at removing chemical residues?

high-pressure washers

What is ‘Quality’?

Any attribute which is associated with the product that the consumer considers important which influences their decision whether or not to purchase

What are the quality attributes that can be determined by the consumer at point of sale?

• Product type

• Cultivar

• Shape

• Size

• Colour

  • Blemishes

What quality attributes contribute to repeat purchase?

• Sweetness

• Sourness

• Texture

  • Flavour

What are the hidden quality attributes?

• Nutritional value

• Safety

• Health benefits

  • Free from contaminants

What are the production attributes?

• Price

• Organic

• Genetic engineering

• Plastic free

• Carbon footprint

• Water impact

• Biodiversity impact

• Brand

• Locally Grown

• Fair trade

  • Ready to eat

What makes an attribute a hidden attribute?

The consumer can’t tell from simply handling or eating it. Determining these qualities requires highly technical and costly tests.

What makes something a production attribute?

It has to do with how the produce was produced or marketed.

What is a downside of using environmentally friendly packaging?

It’s less effective at reducing water loss and extending shelf life

What is a Spife?

A spoon/knife version of a spork. Zespri developed a biodegradable version to include with their products so that consumers can eat the kiwifruit easily.

For what purpose is image capture used during grading?

Size, colour, and detecting external defects such as surface blemishes.

Which fruit crops now have specialised commercial graders?

citrus, apples, peaches, cherries, kiwifruit, carrots, capsicum, onions

For what purpose is an accelerometer used?

To conduct force-deformation tests to check the de-acceleration rate of a light object striking the surface of the fruit as a non-destructive quality check using acoustic waves. It’s had limited commercial success

Why is wax applied to fruit?

To reduce water loss and increase consumer appeal

To what degree can wax prevent water loss in produce?

30-50 % under commercial conditions, especially if the stem scar and other injuries are completely coated

What is the interaction between washing and waxing produce?

Washing can remove the natural cuticle of the produce thereby increasing fruit shrivel, and waxing replaces the cuticle

What do most commercial wax formulations contain?

A mixture of waxes from plant and/or petroleum sources

What are the benefits and downsides of paraffin wax?

Good control of water loss, bad lustre

What are the upsides and downsides of carnauba wax?

Attractive lustre, poor control of water loss

What are polyethelyne, synthetic resin materials, sugars and sugar derivatives, chitosans, and emulsifying and wetting agents used for?

Waxing

Other than water loss control, what else may waxes be used for?

As a carrier of fungicides and inhibitors of senescence and sprouting

How are waxes applied to produce?

Brushing, dipping, spraying, fogging, and foaming

Why is it important that wax layers be thin?

Gas exchange may be overly hindered with thick layers, causing anaerobiosis and associated quality loss such as icky flavours

Why do underground storage organ crops generally need curing?

They have poorly developed cuticles and are therefore susceptible to mechanical wounding, postharvest water loss, and decay

What is curing?

Exposure to high temperatures and high humidity before regular storage

At what temperature and RH are sweet potatoes cured?

30 C and 90-95% RH for 4-7 days

At what RH and temperature are potatoes cured?

10-15 C and 95% RH for 10-14 days

What happens during curing?

A surface layer of protective suberised wound periderm forms over the produce, especially at wound sites.

Most rapid periderm formation on potatoes occurs at 20C, why aren’t they cured at this temperature?

The risk of decay is too high

What additional benefit might curing have in citrus?

Wound healing

What influences the postharvest dormancy of potato tuber buds?

maturity and cultivar, but not temperature

What does temperature influence in postharvest bud dormancy?

The rate of sprouting after dormancy is broken

Below what temperature does sprouting rarely occur in potatoes?

4C

Why is the storage of potatoes at 4C not a great idea?

The conversion of starch to sugars

In storage temperatures above 4C how long can potatoes be stored before they start to sprout?

2-3 months

What is CIPC?

3-Chlorisopropyl-N-phenylcarbamate, a strong sprout inhibitor and the most commonly used for the storage of potatoes

How can CIPC be applied?

As a dust, water dip, vapour, or aerosol

What are the downsides of sprout inhibitors?

Their use and MRLs can differ between countries, and they can inhibit the formation of periderm so must be applied after curing

How is the sprouting of onions during long-term storage prevented?

The application of maleic hydrazide several weeks before harvest

What non-synthetic chemical treatments is the industry researching for sprouting inhibition?

Essential oils, ethylene, and controlled atmospheres

Why are fruits such as bananas, european pears, kiwifruit, and mangoes harvested when they are still green?

To make them more resilient against bruising and other types of damage, and improve uniformity of ripening among fruits after exposure to ripening agents

How are bananas unique in terms of ripening?

They can be harvested over a wide range of physiological maturity stages from half-grown to fully grown and ripened to high quality with the use of ethylene

How is Acetylene formed and why is ethylene more effective?

Adding water to calcium carbide, but a concentration at least 100 times higher than ethylene is needed. Also carbide use is banned in many countries for health reasons

Which is the most active of the known ripening gases?

Ethylene

True or False: the concentration of ethylene to ripen bananas is quite high

False, it’s very low

Why might higher concentrations of ethylene be used initially to ripen bananas

The ripening rooms are not sufficiently airtight

At what concentration is a chamber charged with ethylene to batch ripen bananas?

20-200 microlitres per litre, then ventilated after 24 hours to prevent accumulation of carbon dioxide

Above what concentration does carbon dioxide become unsafe for workers?

5000 microlitres per litre (0.5%)

After how long should one recharge a banana ripening chamber with ethylene if the chamber is poorly sealed?

12 hours

When using the trickle method to maintain ethylene levels in banana ripening chambers, what rule of thumb should be used in ventilation to avoid CO2 buildup?

Ventilate at the rate of one room volume every 6 hours

What is the RH recommended for bananas during ripening?

85-80% until stage 2 after which it should be reduced to 70-75%

If bananas are kept in RH above 75% after stage 2 of ripening, what might happen?

Skin splitting

What sanitary issues may arise in high RH ripening chambers?

Mould growth

What happens to non-banana climacteric fruit when they are harvested before their mature green stage and exposed to ethylene?

They ripen to poor quality

What is the optimum harvest maturity for cantaloupes which will be ethylene ripened?

Full-slip

What is the optimum harvest maturity for papayas which will be ethylene ripened?

The first appearance of the yellow colour in the blossom end

What is the optimum harvest maturity for tomatoes which will be ethylene ripened?

First colour breaker stage

If we harvest a cantaloup at full eating maturity, do we need to expose it to ehtylene?

No, it just needs to be kept at the appropriate temperature and RH

What are the temperature, ethylene concentration, and treatment time for avocados?

18-21 C, 10 microlitres per litre, 24-72 hrs

What are the temperature, ethylene concentration, and treatment time for banana?

15-21, 10 microlitres per litre, 24 hrs