Raspberries and cultivated blackberries: Harvesting
Note Number: AG 057
Published: July 1996
Updated: December 2011 and August 2013
Harvesting is the single most expensive operation in commercial berry production. Rigid control over the quality of harvested fruit is essential for maintaining a sound reputation for quality, particularly for the fresh fruit market. Given the pressures involved in harvesting a crop, it is to many growers the single most difficult area of management faced in commercial berry production.
Ripe fruit detach themselves from their parent plant by formation of a layer of cells which disintegrate while the rest of the fruit remains intact. This process is called abscission, and the layer of cells responsible is termed an abscission layer. In the raspberry, each drupelet abscises from the plug, whereas in blackberries the plug is part of the fruit, and plug-plus-drupelets detach from the fruit stalk, or pedicel. Raspberries are ready to harvest when the fruit can be pulled away from the plug, without gripping so hard that the fruit is damaged.
Blackberries are harvested by bending the fruit to create a hinge point at the base of the fruit. Do not simply pull away from the plant. Unless fruit are over-ripe, something will break at the wrong place - usually the fruit stalk below the sepals, which will then require removal as a separate operation.
All Rubus fruit are harvested at a firm-ripe stage; for raspberries, this is before full colour is reached. Blackberries (including Loganberries) are similarly harvested at less than full colour, as soon as they part readily from the plant by bending. Flavour as detected by taste panels is optimal about 24 hours post-harvest, due to losses of acidity and consequent rise in the sugar: acid ratio.
The precise colour point for each cultivar must be agreed between buyer and seller before harvest commences. To the extent that colour is an indicator of ripeness, it is an indicator of the shelf life which can be expected from fruit. Rubus fruits have a short shelf life, therefore colour is a major component of quality. This single point is the most common area of disagreement between growers and market agents. Growers are always afraid that the product specified will be so green that it can never ripen, but will simply become tired, and market agents are concerned that what growers would rather supply, through an appreciation of taste, has an inadequate shelf life. Much of this longstanding conflict can be diminished through appropriate quality control and post-harvest temperature management.
Sequence of operations
Fruit must be picked, packed and cooled as quickly as possible. Fruit continues to live after harvest, and respiration continues at a rate largely determined by core temperature For this reason, fruit should be taken to the packing shed, packed and cooled within two hours of picking to minimise the internal temperature.
It takes about two days and careful supervision to train new pickers to harvest all available fruit, and only fruit that should be picked. Pickers should be equipped with a receptacle for discarded fruit, such as a 1 L billy which can be clipped to a belt. Fruit is picked directly into punnets. It is extremely difficult to grade fruit over a sorting belt without causing some skin abrasion and consequent loss of quality, therefore field grading is to be preferred. Punnets should be carried in a box which suits stacking and handling, and should permit air flow. Detachable handles are a good policy.
Make sure pickers know precisely how full the punnets should appear. The height varies with different cultivars, different types of berry, and different punnets, and all these considerations form part of the quality specifications which should be specified in detail between buyer and seller.
Packing should be a minimal operation, to avoid handling the fruit at all if possible, and to minimise delays between harvest and cooling. Rubus fruits cannot cope with the packing operations applied to apples or strawberries. If pickers are well trained, packing consists of checking the punnet weight and wrapping. Some topping may be necessary, but should be minimised.
Ideally, packed fruit should be cooled using forced-air cooling prior to cool storage. Forced air cooling units are available in a range of sizes designed to operate within a cool room. They effectively reduce core temperature much faster than can be achieved through passive cooling and thereby increase shelf life. Aim to achieve a core temperature of 2oC and maintain it until dispatch.
Punnet sizes and labels
There are currently no regulations regarding preferred punnet sizes, nor tray sizes. There are state regulations regarding labelling which require every punnet to bear the name and address of the grower, plus a declared nett weight of the contents. The print size of each item is specified by regulation; consult your label printer to determine current requirements. Current practice does not include juice absorption pads sometimes seen in overseas markets. Punnets contain 125 grams of fruit. Some growers usually add an extra 10% weight to punnets to allow for moisture loss down the supply chain.
Barcodes are required by some supermarkets. Rubus barcodes are currently registered by the Raspbrries and Blackberries Australia, who should be contacted for details. Contact the Rubus Industry Development Manager at email@example.com or, Barcodes are available to growers on the RABA website in the members' section.
Do not pick wet fruit for fresh fruit sales. When rain is prolonged, a clean-up pick will be required prior to harvesting for the fresh fruit market; this is more cost effective than asking pickers to field grade when more than 10 % of fruit is of reject class. Do not leave over-ripe fruit on the plants, or it will exacerbate the spread of grey mould, caused by the fungus Botrytis cinerea.
Mechanical harvesting requires specific consideration at all stages of management. You should consult the machine manufacturers before establishing a crop, to ensure that constraints imposed by the machines can be incorporated into your farm. The economics of machine harvesting depend on the prices of fuel and labour, machine, and fruit. Currently this equation dictates that a planting of at least five ha is required to justify purchase of a machine.
Two styles of machine are currently available from the USA; the older mechanism uses slapping rods pivoted on two vertical axes on either side of the row, and the newer mechanism uses two drums of fingers arranged as a stack of hubs with protruding spokes, which shake in a vertical plane as they pass along the row. Both machine styles are designed to straddle vertical rows of canes, grown either as stoolbeds (separate crowns) or hedgerows. Harvesters are manufactured in a range of sizes, from small trailed units to large self-propelled machines. None of the manufacturers claim that machine harvested fruit will keep well enough for fresh fruit sales. Both machines beat the canes, causing fruit to fall through foliage onto catcher plates, from where it is conveyed by belts to a sorting belt, and finally tipped into trays or buckets.
Some growers find that fruit harvested in cold weather (for example, before dawn) will keep long enough for carefully graded fruit to be accepted for local fresh fruit sales. This should be considered a bonus; it should not be included in calculating the economics of mechanical harvesting. It is more advisable to employ pickers to harvest a top grade of fruit for the fresh market, and follow them the next day with a mechanical harvester. Current specifications for headlands, row width, alleyway management etc are included in relevant sections in the Agriculture Note: Raspberries and Blackberries; site selection, establishment and management.
This Agriculture note was developed by Graeme McGregor of FFSR in July 1996.
It was reviewed by Mark Hincksman of Farm Services Victoria in December 2011 and 2013.