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Retail handling of fresh potatoes | AG0957 |
Andrew Henderson, Knoxfield
January, 2001 |  |
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Fresh potatoes are subject to quality loss at all stages of the supply chain, but presentation of an attractive product to the final consumer at the retail outlet is particularly important. This Agriculture Note provides recommendations for retail produce handlers to ensure that the best possible product is presented for sale.
Check quality on arrival
A quality check of potatoes as they arrive at the retail store helps to identify where quality losses may be occurring and allows them to be addressed. If there are any problems with the supply chain, it is better that they be resolved at this stage, rather than after complaints from consumers. A quality check on arrival can also serve as a baseline for assessing handling practices in the retail store, so that product quality and shelf-life can be continually improved.
In a supply chain with a quality assurance system, it is likely that there will be product specifications against which potatoes should be checked. There are many factors to consider, including firmness, sprouting, skin blemishes, greening, cuts and bruises, rots, insect damage and physiological defects. Some of these may not be externally visible and require tubers to be cut or peeled for assessment. In brushed potato lines, the amount of soil adhering to the tubers is important. It may also be advisable to set aside a few sample tubers for a couple of days to assess levels of bruising (see Agriculture Note: Potatoes - mechanical damage).
Apart from the tubers themselves, the conditions under which they arrive should be checked eg. the carriage temperature and the packaging. In some systems, a particular type of transport vehicle is also specified.
Regrade any bags that are dropped or damaged
Mechanical damage resulting from mishandling of bags of potatoes is not only a problem in itself, but can also allow rots to develop in tubers. This can be a particular problem in prepacks, where the defects may not be noticed until the consumer uses the product at home and is dissatisfied with the purchase.
Store potatoes in a dark, well-ventilated place at 4-10șC
Potatoes should always be stored in a dark place, to prevent both greening and increased levels of toxic compounds (glycoalkaloids) (see Agriculture Note: Greening of potatoes). However, dark conditions alone will not prevent tubers from sprouting.
If potatoes are not well-ventilated, the resulting lack of oxygen may lead to black heart, a grey/black discolouration of internal parts of the tuber. Black heart makes the tubers unusable and it cannot be detected unless tubers are cut.
The long-term storage temperature range for fresh potatoes is 4-10șC, under which they should retain their quality for at least two months. For short-term storage (eg. at a retail store), temperatures between 4șC and store temperature are generally sufficient. It is important that the potatoes are not allowed to drop much below 4șC, because at around 3șC they begin to chill and accumulate sugars, which will discolour them when they are cooked. Overheating of potatoes can lead to water loss and shrivelling, particularly in those with skin wounds (often seen in "new" potatoes), and can also result in black heart.
Humidity is also important in storing potatoes. The ideal relative humidity for all potatoes is 90%, with an acceptable range of 85-95%.
Do not handle cold potatoes
Refrigerated potatoes should not be moved directly into the retail display, which may be at around 20șC. Such a sudden temperature increase can cause them to split. Potato temperature should be increased in stages. Cold potatoes are also more susceptible to bruising, so it is better to handle them when they are warmer.
Handle potatoes carefully
Too many people treat potatoes as if they were rocks or similar objects. In fact, a potato is a living product until it is cooked and needs to be handled very carefully if it is to reach the consumer as a safe, high-quality product. Potatoes can bruise easily, but the damage may not be immediately evident. To minimise bruising, potatoes should never be allowed to drop more than 15cm. In a retail store, there should be no need for potatoes to be dropped from damaging heights. Potatoes which fall from a display to the floor should be discarded.
Treat potatoes as food
Like all foods, potatoes are subject to physical, chemical and biological hazards which are potentially harmful to consumers. Treating potatoes as food means minimising the chances of these hazards occurring.
In a retail situation, physical hazards such pieces of glass, plastic, wire or wood could find their way into potato displays. Measures such as routine checks of displays and ensuring that lights above displays are protected can minimise such hazards.
No chemicals should be applied to fresh potatoes at the point of retail sale. The major chemical hazard at retail is increased levels of toxic glycoalkaloid compounds produced when potatoes are exposed to light. Greening of potatoes is an indicator of increased glycoalkaloid levels; however, the highest levels are found in the sprouts. If ingested in sufficient quantities, green or sprouted potatoes can be poisonous to humans.
Biological hazards include any microbes (fungi, bacteria, viruses) which are capable of contaminating produce and harming consumers. They are usually a result of poor hygiene during handling. In a retail situation, this could be due to staff not washing their hands or the presence of rats, mice or insect pests in storage and handling areas. Staff education in hygiene and regular pest control should minimise the hazard.
To some extent, potatoes are a special case with respect to biological hazards, because they always need to be cooked before consumption and this should kill any microbial infestation. However, consumers might store or transport potatoes with other produce which may not require cooking (eg. carrots, celery). Problems could then arise with cross-contamination from the potatoes, so hygiene standards need to be maintained.
Ensure good inventory - first in, first out
Potato stocks should be placed on display in the order in which they were received. This should prevent an accumulation of older potatoes which are more likely to lose quality through sprouting or shrivelling (which can occur despite correct storage).
Minimise exposure to heat and light
Heat and light are the main influences on the shelf-life of fresh potatoes and, in general, retail outlets cannot provide optimum conditions in their displays.
Maximising the shelf-life of fresh potatoes means minimising the time they are not in their ideal storage environment. However, there must be a compromise between this and the provision of a display which will attract consumers, as well as the allocation of labour for maintaining the display.
Greening is probably the greatest threat to potato quality in retail displays. Unfortunately, the white fluorescent lights common to most retail stores are among the worst possible for prevention of greening. Displaying potatoes under yellow or green light, or covering the stock to exclude light, are methods by which greening could be reduced, but these have practical limitations. Shielding potatoes from light when not open for business will also help, but will not be applicable to many modern-day supermarkets. It should also be remembered that the soil on brushed potatoes tends to hide greening rather than prevent it.
With such limitations on prevention of greening once potatoes are displayed, it is even more important to minimise the time in which they are exposed to light.
Limiting the size of the display to about a half-day's sales will help to minimise exposure to both light and elevated temperatures, and thus reduce wastage. As the display is replenished, stock should be rotated, with older potatoes placed on top Stock rotation may be improved by using "retail-ready" cartons of potatoes in the display, rather than the traditional pile of loose potatoes. Poor quality stock should be removed from any display whenever it is detected.
The actions of retail produce handlers largely influence the consumer's impressions of fresh potato quality and so they are a critical link in the supply chain. It is vital that produce-handling staff are trained in best potato handling practices so that the consumer will continue to recognise fresh potatoes as a worthwhile purchase.
Further reading
See Agriculture Notes:
- Potatoes - mechanical damage
- Greening of potatoes
Henderson, A. & Bennett, R. Product description language – potatoes.
Henderson, A. & Coleman, E. Potato grading chart (poster)
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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