Introduction
It is increasingly difficult for UK growers to make a profit from their apple crop. Many factors contribute to this situation. It is clear that the future of the UK apple industry is dependent on the production of fruit with the quality characteristics demanded by the consumer. Moreover, in the future, the industry will need to respond to inevitable changes in consumer requirements. The information provided in this part of the Guide should help growers to provide UK consumers with fruit of the highest quality over the longest period possible.
This part of the Guide is divided in to a number of sections, each concerned with a key area in the attainment of quality fruit to the consumer. The order of the sections reflects the biology of the apple through its phases of development from cell division through to maturity on the tree and finally to ripening and senescence changes that take place during and after storage. The factors that affect storage potential and eating quality are indicated for each phase of development. At any point, failure to adopt best practice can compromise the quality of fruit from store.
Good orchard management is crucial to achieve high yields of large fruit without compromising eating quality or storage potential. It is particularly important to achieve the correct mineral balance in the fruit especially in Cox and Bramley and an accurate prediction of storage quality that helps implement a storage and marketing strategy. Picking at the correct stage of maturity for the intended market is probably the single most critical factor affecting quality to the consumer.
Care must be taken with the physical harvesting of fruits and their handling prior to placement in the cold stores. Fruit quality can be lost through bad picking and handling practice and the wastage in stored fruit may be unacceptable where post-harvest chemical treatments are not applied correctly.
It is important to follow strategies for improving quality of stored apples by reducing ethylene production and improving flavour. The SmartFreshSM Quality System is being used increasingly within the UK apple industry to supplement existing best practice.
It is critical to maintain storage conditions that are most appropriate for each cultivar and for the duration of storage required. Stores must be capable of achieving the holding temperature and controlled atmosphere conditions within the limits prescribed.
Careful monitoring of the quality of each consignment of fruit in each store needs to be carried out regularly. This will ensure that fruit is removed from store before it declines to the minimum quality required and before any development of disorders or diseases reaches a commercially significant level. Monitoring of fruit condition and identification of the major storage disorders affecting UK apples are described in the Guide, along with post-storage grading, packing and distribution of fruit to the wholesaler or retailer.
Storage facilities and operation
The engineering aspects of storage are not covered in this Guide. The decision to exclude engineering was based mainly on the variability in store construction and in ancillary and control equipment that exists in the UK.
It would be impossible to suggest best practice for the maintenance and operation of stores that vary so much in age, construction, refrigeration plant, coolers, scrubbers, instruments and atmosphere control systems. Moreover modern storage and ancillary equipment has become more complicated and generally requires appropriately trained service engineers to carry out maintenance and rectify problems.
For the purposes of this Guide it is assumed that the stores being used meet the requirements to cool fruit promptly and to maintain temperature and CA conditions accurately. Where these requirements cannot be fulfilled the duration of storage must be adjusted accordingly or the storage facilities must be improved.
In recognition of the range in capabilities within the UK industry, particularly as regards the level of gas-tightness of stores for CA, a range of possible CA conditions is provided wherever possible.
Store operators should also be aware of the information provided in the DVD entitled ‘Operators guide to Top Fruit Management’ that was issued by the HDC in 2006.
Stores in the UK that are used for the storage of apples range in quality depending on their age and the technology which was incorporated at the time of construction. Since the late 1990’s many growers have made substantial investment to up-grade and construct new storage facilities which have the capability to employ Dynamic controlled atmosphere (DCA) storage using Fluorescence and Respiration Quotient (RQ) type analysis.
Additionally, the operation of many of the stores is less than ideal, particularly around loading time, with the result that fruit quality is compromised. In many instances, often through lack of appropriate training, the operators and often their managers do not appreciate the significance to ultimate fruit quality of such matters as pre-cooling of stores, slow loading, slow cooling, or deviation from the recommended storage conditions for the specific cultivars. Also, many of the rooms are used for CA storage when they are not sufficiently gas-tight.
For the best practice contained in the post harvest section of this Guide to be put to maximum effect in providing consistently high quality fruit from store, the stores must operate efficiently.
Growers must diligently record the performance of the store as regards temperature pull-down, temperature variation within the store, control of carbon dioxide and oxygen concentrations and weight (water) loss in the fruit.
Where a store under-performs this should be discussed with an appropriate technical expert to resolve the problem. This should be done as soon as the problems/shortcomings are recognised and remedial action taken prior to the next season.
Likewise at this time preventative maintenance schedules must be in place. It is particularly important that the question of gas-tightness of CA stores is not overlooked.
Growers often have maintenance contracts for their refrigeration plant, ancillary equipment and instruments but may overlook the vital need to check gas-tightness. It is important to test stores scheduled for CA operation for gas-tightness every season.
It is particularly important that operators of fruit stores receive adequate training in the following aspects:
- Store construction
- Monitoring and controlling store conditions
- Refrigeration
- Scrubbing systems and gas generators
- Pre-season checking and maintenance
- Store loading and routine operation
It is also helpful for fruit store operators to have some knowledge of fruit behaviour so that they can associate store performance with the quality of fruit. The HDC DVD entitled ‘Operators guide to Top Fruit Management’ issued in 2006 is particularly helpful in this regard.