From the field to the table, harvest of the pumpkin seeds

Still little known in Italy for consumption as such, in other countries pumpkin seed are widely used for salads or added to sweets and/or bakery products. They are offered both natural or roasted and salted in a shell or shelled, and they are excellent ingredients of a modern diet because of their high content of amino acids and unsaturated fats

Pumpkin, belonging to the Cucurbitaceae family, genus Cucurbita, despite not being an autochthonous species (it was imported from the American continent around the sixteenth century), has been used for a long time in the Italian cooking and food tradition, mainly because of the versatility of its mesocarp (pulp). In the Mediterranean area, pumpkins reach the highest productivity in autumn and wintertime; however, thanks to the globality of markets, they are available almost all year round on the shelves of supermarkets.

Pumpkin seeds, often mistakenly considered waste, since sometimes represent valuable co-products for interesting uses for direct consumption or as ingredients in cooking. In this case, they are obtained from dedicated cultivars, which ensure a good production, a significant average size and an adequate uniformity in caliber.

 

Planting system and harvesting machinery

The genus Cucurbita is featured, in all its species, by annual herbaceous plants with creeping or climbing habits, which can vastly exceed 2-3 m of growth. Specifically, the climbing habit of the plant is made possible by the tendrils, which can cling to different types of support in order to adequately support the weight of the vegetation and, most of all, of the fruits. In fact, the latter is characterized by dimensions and weight, sometimes remarkable, and therefore in the open field, it is almost always preferred to keep the plant's carriage creeping. Because of the large surface occupied by the vegetation of a single plant during its full development, it is advisable to adopt a relatively comprehensive planting scheme, that is, a distance of at least 1.5 m on the row and 2 m between rows.

For valuable pumpkins for fresh consumption, but mainly for the ornamental ones (which, given their intended use, must not be damaged by processing), harvesting is usually done manually. For the remaining part of the production, we have moved towards the mechanization of this operation in order to maximize productivity and reduce the time the ripe fruit stays on the ground.

To extract pumpkin seeds, where the pulp is the by-product, harvesting is carried out by machines, both trailed and self-propelled, equipped with a harvesting head and an apparatus to separate the product from residues. The collection of material from the field can be preceded by a windrower to gather pumpkins in a linear heap to facilitate the actual harvesting.

 

Swathing and harvesting header

In the open field, pumpkins grow in a sliding way, therefore without a precise geometrical pattern thus fruits develop in random positions. The windrower usually brought to the front 3-point hitch of the tractor, has the task of intercepting pumpkins and gathering them in a linear heap. The machine design features different levels of complexity, ranging from a simple metal bar sliding on the ground at an angle to the direction of travel of the tractor (similar to a snowplow) to more complex devices equipped with sidearms or augers. Either way, the aim is to convey the product into linear heaps, easy to intercept later.

Moreover, to complete this work routine, a mulcher can be mounted on the rear 3-point hitch of the tractor to act on the resulting vegetation to better prepare the soil for the next harvesting phase.

The harvester consists of a toothed cylindrical drum of large diameter, equipped on its outer side with many pointed metal teeth of about 20 cm in length. Given the rounded shape of the fruit, the progress of the drum over the previously created windrow makes the pumpkins be pierced by the long teeth which hold them in rotation. The product is then removed from the teeth by an interceptor blade placed at the top and then loaded on a conveyor belt perpendicular to the direction of rotation of the drum.

Self-propelled models can combine the picking of the fruit and its loading in a single solution, thanks to a picking head equipped with conveying augers and a suitably shaped reel able to load the pumpkins onto the conveyor belt. For road circulation, the drum rotates 90° at the top so as to make it fit inside the machine's shape.

 

Seed and fruit sorting

The conveyor belt conveys the pumpkins still intact towards a rotor equipped with knives, which chops the fruit. In order to limit damage to the rotor from the possible presence of stones or pebbles in the product mass, Austrian Moty GmbH fits a protection device on its models that causes the drum to move away from the feed inlet abruptly, thus facilitating the removal of foreign material and preventing blockage and damage to the mechanism.

The seeds are sorted from the rest of the shredded pulp and peeled inside a rotating screened drum with openings of about 2-2.5 cm typical size.

The seeds (lighter than the pulp) are sorted from the stirred material in several ways, most often by an external suction airflow generated by a fan and eventually conveyed into a storage hopper. The waste is then scattered in the field, to be then buried. Finally, the seeds are periodically discharged from the hopper into the trailers via a steerable auger, much like what happens on combine harvesters.

The latest harvester models are equipped with video cameras to monitor the different stages of the harvesting routine.