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fresh NOTES (106) 3 February 2015 www.hortgroscience.co.za

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Post-harvest Seminar

About 64 people braved the sweltering Stellenbosch sun to attend the HORTGRO Science Post-

harvest Seminar on the 22 January 2015. The event had an international flavour with two

presenters from Italy, Andrea Cucchi and Dr Luca Buglia, as well as British exhibitors and

delegates.

Topics unpacked, ranged from the latest research to a stock-take of cold chain management, as

well as exploring the exciting prospect of solar panel usage.

The need to revive the CA Group was also discussed and HORTGRO Science’s Research and

Technology Manager, Richard Hurndall, will launch some initiatives in this regard.

The Seminar kicked off with Asanda Mditshwa, a researcher from Stellenbosch University/ARC,

who discussed recent developments in controlling superficial scald in apples.



Apple Scald – a Complex Problem When apples are harvested growers apply various treatments

to protect the fruit during cold storage, which can last as long

as a year. Superficial scald is a skin disorder of apples and

pears. It involves brown or grey discoloration of irregularly

shaped areas on the surface of the fruit during or following

storage.

Prolonged cold storage could lead to superficial scald which

results in brown or black patches on fruit surface. For many

years the treatment of choice to try and slow down or prevent

superficial scald was Diphenylamine (DPA). But, following

health concerns, especially in the European Union (EU), export

markets restricted DPA usage. Alternative methods, such as

dynamic controlled atmosphere (DCA), suddenly became very

important.

In their research Mditshwa reported that they investigated the potential of DCA to control

superficial scald in ‘Granny Smith’ apples. Research was conducted to determine the

minimum critical storage period for DCA to control scald and to assess the influence of

intermittent breaks on the efficacy of DCA treatment to control scald. The fruit was

evaluated according to the incidence of scald, flesh firmness and ground colour.

The researchers found that DCA is effective in controlling superficial scald. However

storing apples for 10 weeks at RA after DCA treatment increased

the risk of superficial scald. They also found that DCA

effectiveness was not reduced by intermittent breaks.

“In future we need to evaluate the evolution of superficial scald

associated with metabolites under DCA and develop a prediction

model for superficial scald,” Mditshwa said.

The research team consisted of: L Opara, K van der Merwe, F

Vries, E Crouch



The many shades of browning. The occurrence of flesh browning in ‘Cripps’ Pink’ apples caused major economic losses

to the South African fresh fruit export industry in recent years. Factors believed to have the

biggest influence on such browning include storage temperatures and duration, cooling

rate (rapid cooling versus stepwise cooling), harvest maturity, cell membranes, and

biochemical antioxidants.

Dr Elke Crouch, researcher from the Department of Horticulture at the University of

Stellenbosch, discussed the differences between radial, diffuse and combination browning

of ‘Cripps’ Pink’ apples.

From left to right: Examples of radial, diffuse and combination browning.

The researchers assessed soil type, tree age and mineral content of fruit of six farms in

the Koue Bokkeveld on the susceptibility towards browning types. Studies showed that the

incidence of three different types of browning was influenced in different ways by pre-

harvest factors such as temperature, soil type, tree age, and mineral composition of the

fruit.

Especially the potassium and magnesium ratio, and low potassium levels had an influence

on the incidence of browning. Potassium was known to be involved in reducing stress and

chilling injury. Crouch said that this needs to be studied further and the context evaluated

before recommendations could be made.



She emphasized that the current data was

preliminary and that a third season of climatic and

mineral trials was underway. Similar browning

trials were also being conducted on ‘Rosy Glow’.

The rest of the research team were: L Butler, E

Lotze, K Theron, H Bergman and I Crouch.

Dr Elke

Crouch



What you see is not what you get

Mealiness in especially ‘Forelle’ pears,

has been an ongoing headache for

growers, said Tavagwisa Muziri, a

researcher from the Department of

Horticulture at Stellenbosch University.

In an effort to shed light on this

phenomenon and hoping to predict

mealiness in intact fruit, researchers

conducted tests using CT scanning and

Near Infrared Spectroscopy (NIR).

They found that NIR can classify

mealiness non-destructively, possibly at

farm and pack house level, though more

data was needed to develop a universal

model.

The findings of the CT scans were

divided into macro CT and micro CT.

“Macro CT has the potential to predict

mealiness before ripening,” Muziri said.

“In order to do that the mealiness porosity

(the pore spaces inside the fruit)

threshold for what can be considered

mealy needs to be established.”

With Micro CT scans the researchers

could observe that the mealy fruit had

larger pores, consisting of intercellular

spaces and damaged cells. “Cells of

mealy fruit were larger and more

ellipsoidal than non-mealy fruit cells,

which were spherical.”

“CT scans provides us with important

clues about mealiness, especially since

mealiness is there even before ripening

begins,” said Muziri. “We can conclude

that storage does not cause mealiness.

There are pre-harvest factors influencing

mealiness that we need to study.

Research team: E Crouch.



The need for Container Temperature Management

About 1.8 m tonnes of fruit are annually exported from South

Africa using mainly refrigerated shipping containers (reefers).

Since the 1970’s when reefers were first used, very little about

the internal architecture, the manufacturing methods, and the

materials used in the bodies of these units has changed, said

Prof. Malcolm Dodd, from the University of Stellenbosch, who

studied fruit pulp temperature management in containers.

“This is in contrast to constant innovation of refrigeration units,

which has made them more efficient in terms of refrigerants

used, refrigeration capacity, energy consumption and the

control systems.”

According to Dodd the containers have an inherent problem of uneven air delivery and

short circuiting, which negatively impacts on product temperature, quality, relative humidity

and cold-steri loads.

“Most shipments with insurance claims invariably come about as a result of incorrect

temperatures,” he said. “Precise temperature control is the only way to manage the post-

harvest quality and shelf life of perishables. The reality is that as many as 30% of

shipments suffer from incorrect temperature management. This equates to 27,000

FEU/annum.”

“Just think about it,” he said. “Fruit spends more than 50% of its post-harvest

life somewhere in a reefer. When the port of destination is an Asian market,

fruit can easily expect to be in a reefer for 35 days or even more.”



According to Dodd, trials have shown that several benefits are achieved by changing the delivery

method of air flow inside a reefer container:

• The fruit pulp temperature can be held closer to set point.

• The range of temperatures (difference between warmest and coldest) is reduced.

• The relative humidity inside the storage area can be increased.

• These improvements in storage environment assist in the maintenance of product

quality and shelf life.

• Probe 3 in cold steri-loads can be held closer to set point.

According to Dodd there is huge opportunity to innovate the design and manufacture of

refrigerated shipping containers. Interior architecture of the container can be improved by:

Reducing the amount of expensive extruded aluminium used by replacing the “T” bar floor

with a grooved floor,

Using modern extruded plastics where appropriate,

Upgrade the humidity management system.

Build in temperature and relative humidity recorders that can provide real time information

as to the environment within the containers.

A disposable horizontal airflow kit from Cordstrap, has been designed and commercially tested, to

aid in monitoring temperature inside containers. “When we control container temperature we

control post-harvest quality,” he said.



Unpacking packing Fruit packing is not just a simple process. It is an art, as

Stellenbosch University researcher, Tarl Berry, explained when

he spoke about the design of future ventilated packaging and the

value of a multi-scale modelling approach.

“Multi-scale packaging is the division of packaging systems into multiple

components/scales, representing levels of complexity in the cold chain. From individual

fruit to internal packaging, carton/box, pallet stack, refrigerated shipping container to reefer

ship.

“By examining all the ‘scales’ as a whole, as well as in isolation, it is possible to identify

new areas of optimisation and even suggest new directions,” he said.

Berry said that there are certain optimisation criteria in package design.

“First we have to look at the mechanical strength – the carton must withstand dynamic

loads over an extended duration in various environmental conditions and protect fruit.

Second we have to look at ventilation – such as forced-air cooling, shipping containers and

atmospheric conditions. Then transport and logistics are important. Shipping systems are

facilitated by the packaging system, which includes

trucks, shipping containers, shipping vessels and finally

destination pack houses. Lastly we look at marketing –

which includes aspects like aesthetics, ergonomics and

convenience.”

About vent design, Berry, said that “we need optimal

designs to enhance the competitiveness of the South

African fruit export”. Here, factors to consider are the

type of fruit, internal packaging, carton production

method and costs, expected fruit cooling rate and energy

efficiency.

“Something such as a vent area is an important factor in

determining airflow and other cooling characteristics.

When we increase the vent area from 1% to 7% the

cooling rate increased by 183.85%, while increasing the



vent area from 7% to 100% showed cooling rate increase of only 62.04%. Increasing the

number of vents improved airflow and uniformity of produce temperature. Effects of vent

shape on airflow and produce cooling behaviour were minimal.”

So what’s next?

Berry said they plan to use multiple parameters to determine best packaging designs for pallet stack handling. They expect the following outcomes:

• Demonstration of the effects of vent configuration on cooling performance and

energy efficiency of different packing configurations and types of internal packaging

for individual cartons

• Demonstration of the effect of vent configuration on cooling performance and

energy efficiency of stacked cartons

• Development of a design methodology for the optimisation of ventilated multi-scale

packaging systems

First session presenters, from left: Tarl Berry, Asanda Mditshwa, Dr Elke Crouch, Tavagwisa Muziri and Prof.

Malcolm Dodd.



Time to fill the gaps!

There is great concern in the fruit industry that large amount of fruit and money is lost

every season due to breaks in the cold chain of SA export fruit, said Dr Leila Goedhals-

Gerber.

A research team investigated this worrying trend to determine possible causes of breaks in

the cold chain from pack house to vessel and to develop a Good Cold Chain Practice

guide.

The main focus of the study was on fruit that is exported in reefers and that is very sensitive to temperature and breaks in the cold chain, such as grapes, summer pears and plums. “In order to determine the causes of temperature breaks in the cold chain, we made observations on fruit farms, in pack houses, in cold stores as well as at the Container Terminal in the Port of Cape Town; we analysed temperature data received from exporters, and conducted temperature trials. “We know that temperature is the main determinant of the deterioration rate and potential shelf life of fresh produce. Humidity is also extremely important, but the higher the temperature, the higher the risk of quality problems such as fungus growth. We believe the effect of the temperature breaks are additive.”



According to Goedhals-Gerber the team observed the

following:

At Farms:

Protocols state that fruit should be picked early in the morning when it’s cool, but fruit is sometimes picked in high temperatures in the middle of the day because it must be harvested urgently.

Once the fruit has been picked it must be transported to the pack house as soon as possible and cooled to remove the field heat, but sometimes the tractors and trailers are busy elsewhere and then the fruit still stands in the vineyard or orchard until noon.

At pack houses:

The receiving area does not always have sufficient shade, depending on the position of the sun.

The pack houses are usually not cooled or well insulated leading to temperatures inside that often exceed 30°C, as opposed to the 25°C in the protocol.

Although the field heat is normally removed before the fruit is packed and in the case of pome fruit it is often packed from cold storage, summer pears sometimes had a pulp temperature of 29.5°C after packaging. As a result of the packaging, the fruit also takes longer to cool to the required -1.5°C.

At cold stores:

The cold stores usually do not have airlock loading bays leading to the pallets being stacked outside in the shade while the container is being loaded.

It takes at least 20 minutes to load the container, during which time the fruit pulp temperature increases, especially when the ambient temp is above 30°C.

If an airlock loading bay is available, the container can be pre-cooled and the fruit will be loaded without a break in the cold chain.

Some cold stores load at night to minimise the impact of the break.

At ports:

At times there are long queues at the port (e.g. due to wind delays) and containers that travel from cold stores with less than 2 hours travel time are not fitted with gensets.

Some cold stores load at night to avoid queues.



Containers should be offloaded on a FCFS basis at the stacks, which does not

always happen. Containers are also not always immediately plugged into the power

source.

The team also analysed historic temperature data received from a number of exporters.

The data covered the ambient temperatures inside the container, measured near the door every 20 or 30 minutes from the time of loading until the container is reopened at the destination.

“We received data from past seasons for the grape, plum, apple & pear export supply chains from the Port of CT to Europe and the UK. The optimum storage and shipping temperature for most of the summer fruit is -0.5°C. For the purposes of the study, a cold chain break was defined as any rise in ambient temp above 2°C for longer than 90 minutes,” said Goedhals-Gerber. “The sample included 123 containers for which 183 breaks were identified.”

As a final output of the study, a good cold chain practice guide for the export of table grapes was developed to help the fruit industry to minimise these cold chain breaks. The guide was developed from a logistics point of view and is presented in pictorial form for easy understanding by all role-players. It contains a section for each segment of the supply chain, e.g. pack house, cold store, etc., which can be displayed in poster format. Recommendations Pack houses: The roofs of pack houses should be insulated for reduced temperatures inside. Pack houses should not become warmer than 25°C.

Loading of container:

Making use of airlock loading bays is the ideal. Cold stores could also invest in air lock loading bays enabling pallets that can be loaded straight out of the cold store into the container without coming into contact with the warmer air outside. This will eliminate breaks during the loading process, said Goedhals-Gerber.

(The rest of the team consisted of: L Haasbroek, C Stander, M Dodd, E van Dyk, H Freiboth)



Controlling your atmosphere Dynamic feedback systems to control CA composition

should be reliable, continuous, non-destructive, measurable

at distance from commodity, capable of automation, and

correlate directly with specific quality parameters,” said

Andrew Brink from Gas At Site.

According to Brink, a chlorophyll fluorescence-based dynamic controlled atmosphere

(DCA-CF) allows one to store fruit at the lowest possible oxygen level with a high degree

of confidence. “It extends storage life, improves flavour and ripening, firmness and scald

control.”

However, there are prerequisites for effective DCA storage:

Well-sealed CA Stores (Pressure Drop 25-18mm water gauge in less than 30 mins).‏ Adequate On-Site Nitrogen supply. High-performance CO2 scrubbers that can operate at low CO2 levels, without

adding O2 to the CA store.

Brink said that there are numerous benefits to DCA – CF. “Chemical-free scald control,

better firmness and flavour, and a marked reduction of internal browning, are all

possibilities. It also benefits pear storage.”

According to Brink, future technologies to keep an eye on include ozone - used in the USA

mainly for moulds; DCA-CF and 1-MCP – used in both Italy and USA; and DCA-CF and 1

MCP and Ozone: Zirkle Fruit, Columbia Reach.



Modern CA-ULO-Dynamic technology Dr Luca Buglia, from Fruit Control Equipment in Italy, made some recommendations for

DCA and explained why the Swinglos System is so impressive.

The Swinglos System

“Certain conditions must be met to fully utilise modern CA-ULO-Dynamic technology,” said

Buglia. These include:

Rooms with perfect gas tightness and a well-sized refrigerated plant.

Apples with same ripening parameters, harvested in the right period.

Rooms filled with the same variety.

Apples cooled before the first stress (pulp temp. 1,3 – 1,5°C).



Mantaintenance of the same parameters during the

stress periods (+/- 0,1%).

Preparation of significant samples that represent the

main part of the room (5-8 wood box close to the

inspection window).

Alcohol analysis during stress period (total analysis 6-7).

Check fruits (samples), leaving them in RA storage

According to Buglia the Swinglos System is reliable, safe,

successful and economical. “It is reliable because the

occurrence of alcohol is strictly related to scald control.

Therefore alcohol is the most important parameter to control.

“Because alcohol is the only real risk of the system, it is completely safe. It is also hugely

successful. Over the last 10 years, Swinglos has been applied more than 3 000 times

without any single scald loss or instance of high alcohol levels. Lastly Swinglos is cheap –

the alcohol detection kit is a simple unit and easy to use.”

Simple and easy! The alcohol test kit



Best of Both Andrea Cucchi, from Agrofresh in Italy, explained how to

get the best out of AdvanStore and SmartFresh and the role

it plays in the automatic control of respiration.

“Apples are alive – they respire, produce heat, loose water,

get sick and can even die,” said Cucchi.

“If we want to extend the post-harvest life of apples we need

to understand the biological process of respiration - the process of obtaining energy from

the oxidation of organic compounds, accompanied by the consumption of oxygen (when

available) and the release of carbon dioxide.”

By utilizing O2 and CO2 sensors, AdvanStore measures the changes in the Respiration

Quotient (RQ, CO2 / O2) of the entire room fruit load.

After the initial pull-down, oxygen levels will be decreased stepwise till the RQ readings

show a significant decrease in the fruit respiration. If and when RQ values go up, the

oxygen levels will be slowly and automatically increased to avoid fruit fermentation.

“AdvanStore allows for more comprehensive and robust fruit quality management during

storage by automatically controlling and adjusting the O2 levels in the room. It is the only

system able to measure the respiration of all fruits stored,” he said.

According to Cucchi, the combination of AdvanStore with the SmartFresh technology,

create increased confidence about fruit quality.

“What we have seen is excellent shelf life and quality maintenance benefits even during

long distance exports and breaks of the cold chain; SmartFresh reduces the fruit

respiration and consequently the risk for fermentation at low oxygen levels; The

combination of the technologies will further reduce the risk for storage disorders such as

scald or bitter pit, especially for long-term storage. According to Cucchi, there is also huge

opportunity for energy saving. “One can compare different rooms based on their

Respiration Quotients. Lastly, controlling the ethylene production and monitoring the

respiration maximizes the storage potential of your fruit.”



Solar Resourcefulness Any business needs continuous and regular access to energy. None more so than fruit

pack houses and cold stores, said Clemens Brandt from Red Engineering.

“The solar generation is growing up fast and timing couldn’t be better with ever looming

power outages and soaring energy bills on the horizon.”

Brandt said that in 2007 South Africa had a “wake-up call”.

“We have an energy crisis. The reliability of energy supply is under strain. Energy costs

are escalating and will continue to do so for some time. Carbon tax is looming and there is

greater carbon footprint awareness than ever before.”



According to Brandt the only way to solve the power problem is “to improve our energy

efficiency and generate our own electricity”.

South Africa has access to an abundance of sunshine compared to Europe, and yet we

lag behind. “Since June last year, Germany managed to generate over half its electricity

from solar, and the UK, France, Italy and Denmark are also believed to have generated

record amounts.”

The cost of photovoltaic (PV) systems in South Africa has fallen dramatically over the past

6 to 7 years. Large solar farms are being built by IPPs, providing electricity to the grid and

small to medium systems can provide decentralised energy for own use which will reduce

the load locally.

Brandt used the installation of 1876 PV modules at Arbeidsvreugd Fruit Packers,

Villiersdorp as a case study. During 2014 they had a 700,000 kWh/a ouput; saved 680t/a

CO2and 990,000 l/a H

2O.

“Pack houses and cold stores are ideal candidates for PV installations with pay-back as

low as 4 years. It can significantly reduce loads and has

a direct impact on one’s CO2 footprint.”

Brandt urged delegates to familiarise themselves with

the solar decision-making tool and investigate alternative

sources of energy.

http://phi.redengineering.co.za/index.php?id=306

Clemens Brandt



Reviving the CA Group? To end off the Seminar, Richard Hurndall, Research and Technology Manager of HORTGRO Science, discussed the possible revival of the CA Group which was originally created in 1997. Hurndall explained the value and function of such a group and asked delegates whether such a group should be revived. There were some positive indications that it should be explored further. Topics covered by the previous CA Group included looking at new technologies, equipment, storage regimes, safety and post-harvest issues in general. It also oversaw CA room inspections by the ARC and produced the CA Operator's Manual. “We need to consider existing forums and groups,” Hurndall said, “but we need to explore whether there is an industry need for an additional CA Group.” One such endeavour that the CA Group could undertake is an international tour to visit other CA facilities. The current CA manual can be found on: http://www.hortgro.co.za/production-techical-information/packhouse-action-group-pag/

All the way from the UK: Jason Knowels, Redpack, and David Hind, locally, from Fruit Sizer’s & Allied.

http://www.hortgro.co.za/production-techical-information/packhouse-action-group-pag/

http://www.hortgro.co.za/production-techical-information/packhouse-action-group-pag/

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