Saffron, towards mechanized harvesting
Saffron, with a price which can reach 35 euro per gram, is one of the most expensive spices on the market. Hence, over the years, its cultivation has attracted an increasing number of operators. And the research for its progressive mechanization is growing up
Whether in spice blends or used as is, saffron is a spice widely used globally. Marketed as a powder or in the form of whole stigmas, saffron is the most expensive spice globally, reaching prices up to 30-40 €/g (that is 30-40,000 €/kg!).
Saffron is a product obtained from the stigmas of Crocus Sativus, a plant belonging to the family of Iridaceae. This culture originated in the eastern area of the Middle Eastern basin and has been known since ancient times.
Although the leading producer in the world is Iran, the Mediterranean area has been playing an essential role in the production of saffron for a long time. In Italy as well, and in particular, in Sardinia, this cultivation plays a significant role.
Saffron is perennial cultivation, which develops in plants having a height from 20 to 30 cm; the plant's epigean apparatus, known as corm or group of corms, is an accumulation organ for the storage of starches. Saffron plant is sterile, therefore propagation is done by manually picking up lateral corms, which can be separated and transplanted. Leaves are green, thin, straight, and lanceolate, with 1-3 mm diameter. They grow after the appearance of flowers or at the same time as their opening. In the Italian climate, flowering is progressive, starting from October. Each plant produces 3-5 fleshy, lilac-colored flowers; each flower has a three-pronged style, on which there is an intense crimson-red stigma, with a size of 25-30 mm.
Planting system and cultivation techniques
Although saffron is a pretty resistant crop, even when cultivated in a suitable area (such as the Mediterranean one), its planting requires some care. Plants can stand very well sudden changes in temperature and eventual problems caused by lack of water. However, it requires proper exposure to the sun, and it is susceptible to water excesses. As with all bulbous plants, saffron fears water stagnation, which is the cause of molds, fungi, and rottenness which would irreparably damage the crop. That is why saffron groves are usually planted in well-drained soils, with a frank or frank-sandy texture, often previously stripped and possibly fertilized. In order to avoid water excess, after the usual primary works, it is advisable to make a baying, in order to create raised areas of soil in which to bury the bulbs, at a depth of about 10-15 cm (increasing it to 14-15 cm for polyannual cultivation). The distance on the row is usually 8-10 cm (12-15 cm for polyannual cultivation), whereas about 20 cm are to be considered between the rows. In Italy, the planting is done in August; except in the case of arid years, there is no need for irrigation, as the development of the plant (and of the bulbs) takes place in September and then in March-April, times which are usually rather rainy in Italy. It is possible to provide hoeing or weeding between the rows in order to control weeds.
Traditional saffron harvesting
It is carried out by hand, picking single flowers between mid-October and the beginning of November. Because of the typical nature of the product, it is not possible to consider complete mechanization of harvesting. As a matter of fact, the harvesting process is the most delicate of the whole production chain since the flowering takes place in rather rainy periods in the Mediterranean area. Therefore, it is essential to pick the flowers as soon as they open to avoid damaging losses due to heavy rainfall.
As the saffron plant is only a few tens of centimeters high, manual harvesting is done with the operators facing the ground, a particularly tiring and uncomfortable position. For this reason, some manufacturers have developed facilitating devices intended to improve the operators' ergonomics while increasing the efficiency of the operation.
The harvest that will be: Italian prototypes
The Mechanical Engineering Department of the University of Cagliari has designed and developed two prototypes of mechanical facilitators to improve the ergonomics of saffron harvesting in Sardinia. The first device is designed to remove the flower from the base of the calyx and is made of a rigid "C" frame moved by a cam that cuts the flower by rubbing without damaging the leaves (which are more consistent than the flower, which is much more yielding). In order to limit undesirable moisture deposits that could cause "maceration" of the calyx during flower picking, the materials used for the cam and C-frame are appropriately differentiated. The entire cutting apparatus is applied to a portable (but not handheld) device for picking cut flowers.
From this first prototype, a further one has been developed, of smaller mass and therefore really portable, consisting of a "hand" which, exploiting the different consistency between flower and stem, picks up the flower and sucks it into the upper part of the device. The fingertips of the hand, which pick up the flower, move with helical motion, driven by a pneumatic cylinder. In its turn, the hand is hinged to the main body and, through an elastic return (adjustable), it turns the flower to facilitate its detachment from the stem.
From flower to "red gold
The following phase is the peeling, which is the separation of stigmas from the calyx. This processing must be done in the shortest time possible (absolutely in one day) because the degradation of the flower, and the consequent release of humidity, could irreparably damage the product. Separating the stigmas from the rest of the flower is only done by hand; afterward, the saffron is dried at low temperature (40-50°C) to guarantee its preservability without altering its appearance and aroma.
Propagation of saffron: harvesting (and selling) of corms: Harvesting (and sale) of corms
The trade of the saffron corms (bulbs) has an independent market from the spices. Corms are removed and harvested with dedicated machines similar to those used to harvest other types of bulbs, such as onions and tulips.
This equipment is usually towed, with a head with inclined disks that dislodges and conveys the bulbs towards the collection belt for loading on board. A series of mobile grid carpets divide the bulbs from the clods of soil inevitably present through constant oscillating movements at low frequency. Then bulbs are transferred to a trailer driven to the side of the machine by a conveyor belt, which takes them to the company center for screening according to their size. The caliber of corms defines their commercial value (0.2-0.3 euro/unit). Besides, some growers and corm dealers also offer advice and assistance for saffron cultivation.
Cultivation Yield
Saffron is a spice with a very intense and characteristic taste and color; usually, 2-3 stigmas are enough to properly flavor dishes for six people. The worldwide production is quantitatively minimal, that is about 300 tons/year. However, the amount used for cooking is always minimal, also because of its very high cost. As a matter of fact, saffron is marketed (in dry form) in one gram or even fewer packages. To be noticed that in order to produce one kg of dried product (in Sardinia), the stigmas of about 200,000 flowers are required. Thus, only five-thousandths of a gram of the final product are extracted from each flower.
