Well regulated and controlled processes
The activities at the packhouse facility for melons must be well regulated and controlled. The process of washing (if applicable), sizing and grading is usually carried out through an automated system, such as roller conveyors with adjustable speed, but always well supervised. Cooling of the products should follow immediately. Forced air cooling or hydrocooling are effective tools to quickly lower the melon temperature. However, melons should not be stored below their critical temperature, as chilling injury may then occur which would result in risks on discolourations of skin, poor flavour and increased susceptibility to decay. Because melons have a high weight, the skin is vulnerable to machine damage or damage from falls.
Activities at packhouse before packing
Unloading of melons at the packhouse. Photo by WUR.
Receipt and unloadingWhen the melons arrive from the field, unloading should begin immediately in order not to delay further processing and the beginning of cooling. A first quality control can take place simultaneously with unloading. A quality supervisor registers this data of the product. The treatments of the melons received at the facility take place fieldwise and lots must be clearly identifiable to maintain traceability.
Cleaning of melons in a packhouse. Photo by WUR.
Cleaning and washingCleaning the melons is important to remove surface dirt or pathogens. Melons are cleaned using brushes and clean water. In this washing process, the melons are transferred into a dump tank, and water flume system, before entering the grading line. To avoid infestation with plant pathogens in the dump tank, the water must be sanitized. As a final washing step, the fruit should be rinsed with fresh clean water. The subsequent surface drying can be done on a belt consisting of rolls where air turbines remove excess water.
Melons on a sorting line in a packhouse. Photo by WUR.
SizingThe purpose of sizing is to ensure uniformity within the same package. The size of muskmelons is often based on count per container, for example 4 to 6 (small boxes) or 7 to 12 (large boxes). The size of the larger watermelons is usually based on weight per unit and packed in larger boxes. To ensure uniformity in size, the range in size between melons in the same package should not exceed the specifications of the buyer.
Melons ready to be graded. Photo by WUR.
Grading and classificationThe process of grading and classification should result in uniformity in origin, variety, size and quality. Make sure to sort out melons with signs of decay and damages. Always handle fruit carefully during this grading process. Melons are classified into classes such as: Class Extra, Class I and Class II. Examples of minimum requirements for all classes are that fruits must be intact and sound.
Waxed melon. Photo by sirtravelalot/Shutterstock.com
WaxingWaxing can be done to reduce water loss and obtain a shinier appearance. The need for waxing will depend on the requirements of the client. Fruits must be dry prior to waxing. Then a food-grade wax is used, approved by the importing country. The wax can be applied by automatically spraying it on the fruit surface. Brushing during application helps to obtain a uniform application to the fruit. After waxing, the fruits pass through a forced-air dryer.
Activities at packhouse from packing onwards
Melons packed in boxes. Photo by WUR.
PackingThe packaging needs to provide physical protection to the fruit. Therefore, a strong protective packaging is used. Mostly melons are traded in bulk, that means without pre-packaging. The loose melons are packed in cardboard boxes or wood or plastic transport boxes, possibly with inlet tray and linerbag. A partition in the carton boxes can be used to further protect the melons from impact damages. The boxes must be packed based on weight and classification. Packaging requirements vary between customers and market segments.
Labels on boxes with melons including information such as product, variety name, packhouse code, size/class and batch number. Photo by WUR.
Labelling and palletizingFilled packages must be stacked on a pallet and labelled with information including packhouse code, size/class, and batch number. Further the name of the fruit (melon) + variety, and net weight must be on each box label. The exact requirements can differ depending on local regulations and client demands. Completed pallets must be strapped well in such a way that the packaging cannot shift or fall. As soon as pallets are completed, they need to be moved to the cold storage.
Measuring melon fruit temperature. Photo by WUR.
Pre-cooling before storage or shipmentA fast temperature reduction is necessary to remove field heat from the melons as soon as possible. This extends the storage life of the melon, retards the breakdown of sugars and inhibits growth of moulds. Forced-air cooling and hyrdrocooling are effective tools. During this pre-cooling process, the fruit pulp temperature should be regularly checked in the coldest and warmest place of the pile.
Cold storage of melons. Photo by WUR.
StorageThe optimal storage temperature for melons depends on cultivar, maturity stage and storage time. At very low temperatures, the melons are subject to symptoms of chilling injury, and at high temperatures they are subject to decay. For cantaloupe types most references indicate temperatures between 2 and 5 °C as optimal. For honeydew types and watermelon, 7-10 °C is usually recommended. The lower temperatures within this range are more suitable for the riper melons. High relative humidity (90-95%) can further help to prevent desiccation.
Good cleaning of equipment and materials is paramount. Photo by Sorn340 Studio Images/Shutterstock.com
Cleaning and maintenanceProper cleaning and sanitizing of building and equipment is part of good packhouse practice. Besides maintenance as prescribed by the supplier, a good cleaning and sanitizing of equipment such as the grading line is necessary prior to use. Sorting belts must be clean and have smooth surfaces. All surfaces that could lead to bruising or puncturing of fruit should be well covered for example with impact absorbing foam.