ONION QUALITY CONTROL
The onion requires several treatments previous to its storage. The first step is to dry it, in order to improve its conservation during the onion packing process. The bulbs are also treated to avoid their sprouting; this ii done with chemical products or irradiation. Conservation is done at 65-75% of relative humidity and temperatures around 0ºC.
Before onions are put in storage rooms, it is important to dry or cure them. The aim is to dry the neck and the outer layers to protect them from possible diseases and maintain onion traceability. The moisture content must be reduced in 10%, which is equivalent to 3 to 10% loss of weight. The drying process may take place in the field if the environmental conditions allow to do so (dry climate). If not, they use artificial drying systems, like forced air, either environmental temperature or hot air.
During storage, it is important to avoid the bulb sprouting and the secondary roots. For this purpose it is important to keep low temperatures and modified atmospheres. However, in some cases other methods are used, like the application of chemical products and irradiation. Among the chemical products used there is the maleic hydracid, that is applied shortly before harvesting. Irradiation consists of exposing the bulbs to ionizing gamma ray radiation to inhibit sprouting. For this process they use very low doses.
After the harvesting it is not usual to subject onions to pre-cooling. It is only recommended in case of tender onions, since a fast decrease of temperature improves their conservation.
The storage time depends on the variety. Early onions cannot be stored more than 4 months. The bulbs are stored in bulk in piles, in sacks on pallets, in field boxes or palots. In any case, ventilation in all the produce surface must be allowed.
Storage can be done in different ways. One can use traditional storage facilities. This method is suitable for cold areas and when we do not want to store the bulbs for a long time.
Storage under forced ventilation is also used. For this treatment they use fans, that renew the store room’s air, removing the heat produced by the bulbs.
Another storage system is under controlled conditions. The onions are not sensitive to chilling injuries, so one must take advantage of this characteristic for its storage. Thanks to this system, some varieties are preserved up to 32 weeks. The moisture levels must be kept between 65 and 75%, and temperatures should not be lower than -0,8ºC. However, for short storage up to 5 weeks, the temperature recommended is 15ºC. The use of modified atmospheres is not recommended, because it gives contradictory results.
The onions must not be transported at temperatures over 20ºC, and they must be lowered in relation to the length of the journey.
The onions are transported at temperatures between -1 and 20ºC, according to the distance of the trip. Relative humidity must be kept between 65 and 75%. Onions give off their smell to other products; thus, they must not be transported in mixed loads.
There must be a suitable ventilation during the transport. For transoceanic trips they use containers with apertures. By means of a fan the air circulates through them. In case of palletized onions, the air must be distributed through the palets.
Distribution is due to be at temperatures between 5 and 20ºC, with average moisture and ventilation levels.
Onions have different problems in their storage. There appear several physiological alterations like translucent scales, sun burns and greening. They can also suffer diseases caused by Botrytis, Fusarium, Sclerotinia, Aspergillus, Penicillium and Colletotrichum or by the bacteria Erwinia and Pseudomonas.
Among the alterations we find the following ones.
Translucent scales: it consists of a paling of the scales colour, that later on turn brown. Although the reasons for these changes are not clear, it is thought that high temperatures before the harvesting favour them.
Sun burn: it takes place during the drying, and it affects mainly the onions with few protective dry scales.
Greening: the outer scales acquire a greenish colour, and there appear unpleasant tastes. This phenomenon takes place if the bulbs have been exposed to the sun for too much time.
Some of the diseases that affect the onions during their storage are:
Botrytis rot, caused by the Botrytis fungus. It is one of the main postharvest alterations. It is characterized by a wet rotting in the outer tunics of the affected area, covered with very short gray hairs. In order to control this disease it is important to harvest the bulbs in their maturation, in dry wheather, and to let them dry appropriately.
Rotting in the base of the bulb. This alteration appears already in the field, and it fully developed in the warehouse. It is caused by the Fusarium oxysporum fungus, that infects the bulb through the roots, reaching the base of the bulb and producing the rot.
White rot. Caused by the fungus Sclerotinia sclerotiorum, and characterized by the presence of a white down on the affected areas; there develop a kind of small black spots of 1-2mm of diameter, similar to a pin’s tip.
Black mouldy rot. This disease originates from the fungus Aspergillus niger. This organism penetrates through damages, normally in the top area, producing black efflorescences and rotting in the tissues affected.
Another fungus belonging to the same genus, Aspergillus alliaceus, has the same characteristics but it produces a yellow efflorescence.
Blue mould. This disease is caused by the Penicillium fungus, and it is characterized by a rotting on which a blue down grows.
Coletotrichum circinans is a fungus that produces anthracnose or grime. This alteration is characterized by the presence of circular black spots on the external tunics of the onion.
Onion Mildew. The fungus Peronospora schleidenii attacks the onion during the culture cycle, and it is lodged in the apex of the bulb, producing blossom-end-rot if there is enough moisture.
ONION QUALITY INSPECTIONS
Production and quality of the onion crop (Allium cepa L.) cultivated under controlled deficit irrigation conditions in a semi-arid climate
The experiment discussed below was carried out on an onion crop cultivated under controlled deficit irrigation (CDI) conditions in a semi-arid climate. Eight treatments were used in which different water doses were applied according to the water requirements at each stage of the crop cycle. The effect of water deficit was studied at three vegetative stages (development, bulbification and ripening).
Although, the dry matter yield was not affected by the total volume of water intake (with volumes ranging from 603.1 to 772.0 mm), the statistical analyses made have shown that there is some interaction between the volumes of water received by the crop at the bulbification and ripening stages, which means that inducing a shortage in both stages at the same time does lead to significant differences in the yield obtained.
As to bulb sizes, the treatments which received the greatest volumes of water during the development and ripening stages yielded harvests with higher percentages of large-size bulbs, whereas the water shortages induced during the growth and bulbification stages led to higher percentages of small-size bulbs.
ONION INSPECTIONS AND IMPROVING QUALITY
Nutrition programmes based on crop nutrient needs are key to influencing both yield and quality. Crop nutrition influences dry matter content, firmness and storability as well as taste and pungency, all important factors in determining the quality of onion crops.
Firmness is a critical characteristic of onion crops, particularly in dry bulb onions which are stored for long periods. Growers can influence bulb firmness by applying balanced nutrition. Nitrogen can help to increase the specific weight of the outer skin, which results in an improvement of the bulb’s resistance to pressure, therefore reducing handling and storage damages. However, overall bulb firmness may decrease with high rates of nitrogen due to a softening of internal tissue.
ONION SKIN QUALITY
A uniform skin is a major element of onion appearance for the fresh market. In addition, the strength of the onion skin is important to help keep diseases and storage problems away. Skin cracking can be a result of poor soil moisture. A balanced nutrition program is also essential to ensure that the overall skin quality of an onion crop meets market demands. A balanced crop nutrition programme can help to reduce onion storage rots by promoting healthier plants. Onions need a period of curing or drying in order to seal the neck, prevent invasion of diseases and rot and to create a bright, crack-free skin. Calcium, magnesium, boron and nitrogen all have an effect on onion storage rots.
Processing factory MSP Onions foresees every customer of programmed quality onions
"Internal quality sorting for onions demanded from all European supermarkets within two years"
The new onion processing factory of MSP Onions in Nieuwdorp is almost serene. Nevertheless, an impressive volume passes through the factory every day with a capacity of 1,000 tons per day with good demand. "In a traditional situation you would work with 70 people, we do it here with seven people and that includes cleaning and technical service," says Lindert Moerdijk. He gave the AGF / FreshPlaza editors a tour of the new automated and sustainable onion factory, where the overarching software layer Eqontrol controls the various machines in the factory's process and takes care of stock management.
In this dream factory, as Moerdijk calls it, he can provide his worldwide customers with programmed quality onions. "Customers in Asia, Africa and Central and South America all have their specific requirements with a corresponding price. We can now serve them perfectly according to their wishes thanks to our internal quality control. The reactions are positive and it feels really great as a seller to do this. The Eqrader is the only machine in the world that can assess the entire onion internally at this rate. Many people say they have quality onions, but with this sorting machine we can guarantee it. The quality sorting is programmed for each customer. how the customer wants to receive the product, accurate to the millimeter and checked internally and externally."
"In this new factory we run from early in the morning until late at night. No human hands are involved, so it's a very Corona-proof, no-touch policy. We have four machines that together can sort 160 onions per second. Six photos are taken of each onion. We select based on seventeen quality qualifications, such as colouring, disease symptoms, hardness, internal and external quality. This makes it easy to select the class I onions from a batch.
"At the end of last season we even had the situation where a customer thought I was kidding him and had delivered a batch of New Zealand imported onions, says Lindert. "Every batch can be traced in Eqontrol thanks to advanced tracking and tracing software. For example, we have a proven tracking & tracing, per onion, per box, per second. This gives us an astounding database. This way we know exactly how. the different varieties and onions from the different growing areas are performing well. "
Not a single rotten onion in the bag
In 2010 MSP took the step to start exporting its onions itself as a packing station. The Nieuwdorp company has mastered this trick by now and the onions are shipped all over the world all year round. Thanks to the new factory, the company also hopes to gain attention in the supermarket channel. "We can guarantee a supermarket - or supplier of a supermarket - that there will not be any rotten onion in its bag. When I sometimes see onions lying on the supermarket shelf, I get tears in my eyes. Thanks to this programmed quality sorting, that is a thing of the past. I expect that this technique will revolutionize the shelf and that within two years every supermarket in Europe will make it a condition that all onions have been checked for internal quality. "
"In addition to a wealth of data, this also provides great export opportunities. We can open new sales areas and supply the existing areas for longer. For example, I now send onions to certain destinations, where I previously really did not dare with a transit time of five weeks. Like when Brazil comes onto the market, for example, I do not have to worry about discoloration, but we can go full throttle. It is a matter of programming out those few onions that are too dark and what remains is a fantastic batch. This is immediately an added value for the grower who does not need to have 100% suitable onions, but can also get added value if the color of his batch is 90% suitable. Especially in the spring when many countries often switch to onions from other countries for quality reasons, this becomes very interesting if we can therefore guarantee top quality," says Lindert, while he automatically orders three different samples from the control room. "All from the same party, they used to leave as one party. Now we are sending them to three different customers, all of whom are very satisfied with it."
"In addition, I firmly believe in the principle of machine learning. Our Profix ERP is now directly linked to the machines via Eqontrol. For example, a trailer can be linked to my sorting programme with one mouse click and we have virtually no changeover time. Based on parameters dictated by purchasing. Eqontrol then sets the speeds and determines the routes needed to sort the trailer as efficiently as possible. On the output side, it then continues and Eqontrol sets the receipts of the entire packing department on the basis of the order data. The software determines the moment from starting the processing of the order, from retrieving the appropriate product from the warehouse to setting up all machines in the line. A fantastic combination of new software techniques that reduces downtime and makes mistakes a thing of the past. "
"An additional advantage is that performance is now transparent and schedules are updated live. Now we really know everything, while traditional sorting and packaging was a black box where assumptions were used. I want the role of operator to no longer be so determining. One wrong setting on any machine in the line is already causing a huge disruption. It has to be removed! It simply has to be able to pack 120 tons of onions per hour in peace and quiet and in fact have only three options: start, stop and pause," laughs Lindert.
Artificial Intelligence has been mentioned by Lindert for years as the big difference for sorting onions. "To make optimal use of that, you need a lot of exits. Sixteen exits is not a luxury if you know that the waste onions are already programmed in three types. We started at the beginning of September and the margin of error was 2% because the neural networks were not yet available. trained for certain syndromes. We are now at 0.2% and that percentage is only getting lower," says Moerdijk.
"For retail customers we now set up the machine in such a way that it is 100% right, in terms of colour, size and internal quality. Although this company has decades of experience in sorting onions, the machine judges more accurately than meets the eye. The margin of error of the machine is considerably lower and the machines can also be used every hour of the day."
Circular production process
When asked whether there are many onions that are left out, Moerdijk answers in the negative. "In fact, we are increasingly moving towards a circular production process without food waste. We have included waste separation in every phase of the design. As a traditional sorter, you have one big pile of leftover, but that food waste is a thing of the past. Of the onions that in the past were sorted out, 75% are now processed into food and the remaining 25% goes into the bio-digester. This is also positive for the grower. The sustainability of agriculture and the more extreme weather conditions are still creating more uncertainty. This factory can really add a lot of value for the growers."
The storage is based on a condensation drying system and the entire factory is fully electric. The onions are picked from an automatic warehouse, referred to by Moerdijk as a black box. "MSP has been able to come up with the 'rules' of the warehouse itself and Eqontrol has given substance to this. On a dashboard we can now see the stock accurately to the kilo live without the operators having to know where it is located in the warehouse. This was a special experience and incomparable with the traditional working method. As a seller I also have the dashboard open and I can see exactly what can be sold. As a result, the current floor area of 13,000 m2 on several floors has remained relatively limited in view of the capacity. save 60% on internal logistics movements. If we had worked in the traditional way, we would have needed three times as much space," says Lindert.
He hopes that the entire Dutch onion sector will get a boost from this investment of approximately 20 million euros. "About forty Dutch onion processors have been working in the same way for decades, at the same cost price and also largely to the same customers. The changing climate with long wet and dry periods requires a quality impulse, which could not be absorbed by manual sorting. But while many new demands are being made of farmers, the processors have lagged behind. In our view, we are not going to win the world with this and that gave the incentive to set up this project. Let the sorting and packaging process become Planet Proof! Our sustainability requirement may become stricter than a BRC certificate."