Until the third quarter of the last century, potatoes were a local staple. It was consumed and processed within a few hundred kilometers of where it was grown, but gradually moved into the category of significant global trade commodities. All-season guaranteed transportation of fresh consignments, i.e. natural, potatoes has its own characteristics and is accompanied by many risks. Potatoes as a cargo are officially classified according to generally accepted logistical standards. In the international potato trade, maritime transport regulations are the most elaborate (CargoHandbook.com). With some amendments, these regulations are also applicable to the road delivery method, which for many reasons has become the main one in the Russian Federation. At the same time, Russian potato growers should start looking at the sea delivery method, as the level of development of the industry is increasing, and climate change will only increase the competitiveness of Russian potatoes in the future and facilitate its export. A return to an adequate level of tariffs for rail transportation of potatoes between remote regions of the country, which seems unlikely so far, cannot be ruled out.
Potatoes as an object of transportation, risk factors and prevention of losses during transportation
1. Temperature transport should be such that respiration losses and therefore weight loss due to evaporation are as low as possible. The intensity of potato respiration is minimal at a temperature of 3-5 °C, and from 12-18 °C it increases two to three times for every 10 °C, decreasing at 40-50 °C with damage to the tuber. Critical temperatures range from 21 to 29 °C. As the period of deep dormancy ends, potatoes begin to germinate (at temperatures > 6-7 °C). Therefore, before the potatoes are transported, it is important to establish under what conditions the potatoes were stored before, as this is important in relation to the dormancy of the sprouts. If the storage temperature was above 6-7 °C, seedlings should be expected. At temperatures < 3 °C, potatoes begin to become sweet and lose their flavor (cold damage). At temperatures from -2 to -3 ° C, the tubers freeze. Only short-term cooling is allowed during cargo handling at temperatures even down to -2 °C; however, potatoes permanently damaged by frost should be discarded.
The standard temperature range used for transporting potatoes is from 4 to 15 оC. For seed, most often, 3-4 оC, for table: 5-7 оC, for technical and early from the field: 10-15 оC.
2. Air humidity when transporting potatoes, it is necessary to maintain in the range of 85-90%. 95% is sometimes recommended, but this is a very dangerous level at low transport and storage temperatures. If the potato for one reason or another is cooled below the dew point temperature, then moisture condenses on the tubers. And condensate is the most harmful phenomenon for the quality of the product. Drops from condensate provide optimal conditions for the activation of potential rot pathogens. Excessively humid warm storage leads to the formation of roots at the bottom of the sprouts, then there is a massive loss of weight and nutrients. When the potatoes are delivered for loading, it is necessary to make sure that the bags or boxes with the goods are dry. When loading in rain or snow, the cargo must be protected from precipitation, as moisture can lead to rotting and premature deterioration. Potatoes should not come into contact with salts, as they absorb water vapor due to their hygroscopicity.
3. Ventilation. During transportation, potatoes must be in a certain gaseous environment (oxygen content - at the level of 16-18%, carbon dioxide - 2-3%. The oxygen supply must be provided by active ventilation, since its lack (O2 in room air < 6% by volume) leads to the onset of anaerobic respiration and fermentation. Recommended ventilation conditions: 60-80 volumes of air per hour (air exchange with continuous supply of fresh air). As potatoes place high demands on the ventilation system, it is recommended to maintain a stack height of eight bags whenever possible (maximum stack height 12-13 bags) in the case of a normal load, in order to ensure sufficient ventilation of the loading unit. For this reason, ventilation gaps must also be provided, which must be protected from possible blockage by sliding bags.
4. Biotic activity. Potato tubers are classified as a transport commodity with secondary biotic activity. Care of the cargo during transport should be aimed at controlling breathing processes (emission of CO2, water vapour, ethylene and heat) so that the product is at the desired stage of maturity upon arrival at the destination.
Potatoes must also be protected from light (daylight, sunlight and even artificial lighting in the hold), since it, on the one hand, causes the activation of enzymes that stimulate growth (=> germination), and on the other hand, contributes to the greening of the tubers.
5. Gases. Emission of CO2 during dormancy of potato sprouts (relative to 100 g fresh weight): at 5-10 °C: 0,8-1,4 mg/h, at 20 °C: 2,0-4,0 mg/h. Upper CO limit2 – 0,5 volume percent. Potatoes are moderately sensitive to ethylene, which causes the germination process to begin prematurely. The release of ethylene by the potato itself is very low, less than 0,1 µl/kg*h. But foods that release a lot of ethylene (like apples) lead to premature sprouting of potatoes (allelopathy). For this reason, potatoes should not be stored and transported with similar commodities, as the entire shipment may be lost.
6. Self-heating/self-ignition - there is no risk of transportation for this parameter in potatoes.
7. Smell. Potatoes emit a strong specific (earthy) smell. Tubers also easily absorb foreign odors, such as gasoline, kerosene, chemicals and food.
8. Pollution. Transportation of potatoes is associated with the formation of dust. At the same time, the potato itself is sensitive to dirt, fats and oils.
9. Mechanical effects. Potatoes are sensitive to mechanical influences; they cannot be transported over long distances immediately after harvesting. The "rest period" should be at least 10-14 days.
10. Health hazard. If ventilation was insufficient or failed due to a defect, life-threatening concentrations of CO2 or lack of O2. (Therefore, for sea transport only, before anyone enters the hold, it must be ventilated and the gas level measured. MPC for CO concentration2 is 0,49 volume percent).
11. Weight loss. During long-term (more than a month) transportation, potatoes can lose up to 10-15% of their weight due to the processes of respiration and the release of water vapor. Due to the high water content, potatoes tend to have high losses caused by various factors:
- mechanical damage (we are talking about torn, crushed, crushed or cut tubers; in cases where the damage is more than 5 mm below the surface). Potatoes with very loose skins also fall into this category if more than 25% of their skins are missing or damaged;
- damage caused by animals (insects, snails, mice);
- frost damage
- damage caused by chemicals: if potatoes come into contact with fertilizer salts or other aggressive chemicals, the skin and flesh of the tubers are destroyed by their action;
- rotting of potatoes due to the development of late blight, wet and dry rot. Late blight is not always clearly detectable at the time of loading, but can spread massively in just a few days during maritime transport. Soft rot is caused by pectolytic bacteria that enter the flesh of wet or damaged potatoes, often through small cracks. The disease can spread throughout the cargo in a few weeks. Bacteria are always present on the surface of the tubers, and their development is prevented by cool, dry air and regular ventilation. Diseased tubers are often crushed under the mass of potatoes on top, allowing bacteria to infect healthy potatoes. This makes it difficult to control wet rot and can lead to the loss of the entire load. Silver scab can also spread rapidly during the delivery of potatoes. It significantly impairs the appearance of table potatoes and reduces the germination and productivity potential of seed potatoes.
Regulations for the transportation of potatoes
When determining the methods and conditions for the delivery of potatoes, batch biological parameters. It is necessary to consider the type of use of the product (table, technical (for industrial processing) or seed potatoes); Harvest time: very early potatoes have a loose skin, they have a thin skin that easily peels off, as a result of which they easily spoil; when harvested late, the tubers have a dense skin and are therefore more suitable for transportation.
Quality/Storage duration. When loaded, the potatoes must be fully mature (sprout dormant stage), hard-skinned, intact, firm, of the same variety, not green, damp or smeared. The total mass of products should not contain soil (pathogen), organic components and stones (otherwise there will not be enough space between the tubers for ventilation).
It is generally accepted that the maximum guaranteed storage time for potatoes at 4-6 °C and 90% humidity for possible further transport is 10 months. The use of a controlled atmosphere cannot significantly affect the duration of storage and transportation of potatoes. The introduction of germination inhibitors increases the possible storage period up to 12 months. In fact, transportation is the final stage of long-term storage of potatoes. The consumer is interested in receiving the product in the same form and condition as it was in the warehouse upon loading. The key to achieving the best storage and transport quality is to ensure optimal pre-harvest and post-harvest quality potential, thoughtful handling procedures and, above all, optimum storage temperature and humidity. Therefore, it is necessary to make sure that the potatoes were stored correctly before shipment. After harvest, a distinction is made between three periods of storage and shipment.
Drying period (1-2 days after harvest)
Immediately after harvest, the tubers must be dried to provide favorable conditions for the subsequent wound healing period. At the same time, it must be understood that if drying is extended for more than two days, its effectiveness is significantly reduced. Wet potatoes are transported only from the field to the storage, the goods cannot be transported to the buyer in this way. Drying should be carried out using the maximum possible volume of air (50-100 m3/h) at a temperature of 2-3°C below the temperature of the tubers, but the temperature of the potatoes should not fall below 8°C. If the tubers are covered with a film of water, oxygen is depleted, which increases the risk of rapid decay.
Wound healing period (10-14 days after harvest)
Damaged areas are protected from the penetration of rotting microorganisms by suberization, for which it is necessary to provide a room temperature of 10-15 ° C and a relative humidity of 85-95%. Lack of oxygen and increased CO2 (> 0,5%) contribute to the suppression of respiration and, consequently, wound healing, and stimulate the onset of putrefaction. If the temperature is too low (< 8 °C) and the air is too dry, unripe tubers with loose skins will evaporate excessively. In the first month after harvest, weight loss can be 4-6%; the tubers become soft and are more prone to bruising and Fusarium dry rot. Mature hard-skinned tubers lose only 1-3% weight due to evaporation. If potatoes are shipped during the wound healing period, the climatic conditions typical of this period must be taken into account.
Cooling down/cooling down period
At low temperatures, potatoes can warm up to 0,25 °C per day due to the respiration process. Table potatoes should be stored at 4-6°C and 90-95% relative humidity. Seed potatoes need to be cooled to 2-3 оC, and technical should be stored for a long time at 8-15 оWith the use of germination inhibitors. The decrease in temperature to operating indicators should be carried out gradually and by no more than 0,5-1,0 ° C / day. Preparation (warming up) for the shipment of chilled potatoes is carried out at the same pace, it should be started in a timely manner, taking into account the terms and temperature of transportation stipulated by the contracts.
Packaging. Potatoes are mainly transported in jute or plastic bags with a wide mesh, also in perforated plastic big bags and boxes, cardboard boxes and baskets, paper bags.
Transport symbols:
Means of transport. Sea or river ship, car, railway car, aircraft. Container transport: containers with active ventilation, containers with open sides, flat trucks (for loading below deck).
Cargo handling. In wet weather (rain, snow), potatoes should be protected from moisture. It must be taken into account that the high water content makes the tubers particularly susceptible to bruising. The required transportation temperature must also be maintained during cargo handling, short-term (no more than an hour) deviations of 1-2 degrees are allowed.
Stacking factor: 1,95 - 2,03 m3/t (bags of jute fabric, 25 kg), 1,53 - 1,81 m3/t (bags), 1,62 - 1,90 m3/t (cartons), 1,70 - 2,25 m3/t (bags), 1,98 - 2,25 m3/t (cartons), 1,62 - 1,90 m3/t (corrugated cardboard boxes), 1,53 - 1,67 m3/t (bulk cargo) - according to different sources.
Storage space requirements: cool, dry, good ventilation, as dark as possible.
Segregation (separation of parties): mats, jute coverings, fiber rope, fine fiber nets.
Load fastening. If the potatoes are loaded in bags, it is desirable that the height of the stack does not exceed eight bags (maximum stack height is 12-13 bags) and sufficient ventilation of the load block is ensured. If potatoes are loaded into crates or cartons, they must be positioned so that the space between the packages or pallets is filled to prevent slipping or tipping.
Requirements for packaging for transportation of tubers
Craft paper bags absorb moisture from the atmosphere and lose strength during the transportation of potatoes. Therefore, it is recommended to use two- or three-layer bags. It is not recommended to use paper packaging if the total storage time of potatoes will exceed 10 days.
Knitted jute or polypropylene bags must be used for flights longer than 10 days. A loose-weave jute or linen bag is the best packaging for seed potatoes. Natural fabrics well pass air and moisture, absorb excess moisture, exclude the formation of condensate.
vegetable mesh for potatoes has only one indisputable advantage - it is the cheapest type of packaging. Among the main disadvantages: high permeability to sunlight and low tensile strength. If palletizing and loading onto vehicles is done manually by unmotivated personnel, many meshes will inevitably break. However, with careful handling and a relatively strong thread (the weight of a mesh of 50x80 cm is at least 28 g), many manage not only to transport, but also to store potatoes for a long time. Much stronger onion nets (their weight at a size of 50x80 cm is at least 38 g), but they are also significantly more expensive.
50 kg polypropylene bags less often used for packaging potatoes, despite the relatively low cost. The fact is that you have to burn holes in them on the spot to provide at least some kind of ventilation. For the same reason, general industrial big bags are also used to a limited extent. And here special potato big bags, with sufficient ventilation, become the main container for potatoes. Big bags are best for flights up to 10 days. It is undesirable to allow sudden changes in temperature, which can lead to moisture condensation. In the absence of active ventilation, potatoes in big bags begin to warm up. This provokes the germination and development of diseases, primarily silver scab. Therefore, immediately after delivery in big bags, seed potatoes must be smashed into bulk or containers.
Transportation of potatoes in cardboard and plastic boxes is rarely used, mainly in relation to premium quality products packaged in 2-5 kg in paper or combined bags. In all cases of transportation, it is strongly recommended to place potatoes in containers on wooden pallets. The drip tray provides uniform handling and good air circulation from below. Potatoes for processing into chips, fries, starch are traditionally transported in bulk.
Transportation regulations must be observed equally carefully when transporting potatoes of all categories - table, seed and technical.
It is important to avoid mixing different types/lots of potatoes as this can lead to cross-contamination.
Potatoes must be kept within the same temperature range throughout the entire transportation process, from filling to unloading. Due to excess heat and moisture, it begins to germinate, and excessive dryness causes evaporation and shrinkage. If the air humidity is below 80%, then the weight of a bag of potatoes of 25 kg is reduced by 200 grams per day. Wet conditions allow any bacterial and fungal diseases present to spread more rapidly throughout the bag, with subsequent damage to the surrounding bags. Proper temperature and humidity must be maintained through ventilation, providing a minimum of 14 but preferably 16 volumes of fresh air supplied per hour to prevent CO buildup.2. Higher ventilation rates are required to correct the temperature.
Potatoes must be transported in accordance with the requirements for the product in closed, insulated vehicles or refrigerators, taking into account the destination of the lot, type of product, transport distance and outdoor temperature. Potatoes transported in open bags on open vehicles must be properly covered. The embankment must be transported in such a way as to prevent contamination.
High standards of cleanliness and hygiene must be observed in the cargo compartments and compartments of vehicles during the delivery process to ensure the absence of parasites. Packaged foods and containers must not be placed directly on the floor. Unwrapped potatoes can be stored directly on the floor or on appropriate equipment, but floors or material must be kept clean. The product must be stored and transported in such a way that there is no risk of contamination.
Organization of transportation of potatoes. Suppliers and buyers of potatoes have the opportunity and can timely agree and fix in the contract all the important terms of delivery. The essential delivery conditions include: delivery basis according to INCOTERMS, delivery time, responsibility for hiring and providing transport, type and rate of transport loading, type, method and cost of packaging, conditions and procedure for loading and unloading, ownership and responsibility for the goods during transportation , the procedure for acceptance by quality and quantity, the means of monitoring the agreed conditions of transportation, liability for violation of the terms of delivery, the procedure for presenting and considering claims. Simplification of this section of the supply agreement very often leads to misunderstandings and unfounded claims, reaching litigation.
The seller and the buyer have the right to establish non-standard modes of transportation of potatoes. Unsprouted seed potatoes can be started to warm during transport if planting is planned immediately after delivery. And table potatoes for further storage, on the contrary, should be transported at an optimally low temperature. The temperature of the potatoes and the air temperature in the cargo compartment of the vehicle must be checked and documented before starting loading. The temperature throughout the journey must be maintained and continuously documented in accordance with contractual specifications. From the customer it is necessary to send in writing before the start of loading an instruction to the carrier on the temperature regime. This instruction must be observed throughout the entire transport chain.
The modern level of electronics allows you to objectively record the actual conditions of transportation. A temperature and humidity logger can be placed in each transport unit, and after the end of the trip, a schedule of transport modes can be printed.
Suppliers and buyers of potatoes must understand that delivery in a refrigerated truck cannot guarantee a 100% result just because the potatoes were in good condition before loading. Serious losses can occur even within one week under suboptimal transport conditions. However, thoroughness and caution must be exercised when identifying the causes of problems with the quality and safety of tubers during or after delivery. The fact is that the quality of plant products depends and is determined by many factors before and after harvest, including the physiological state of the tubers at the date of shipment. Sub-optimal conditions in the pre-growing and storage phase often only become apparent and negatively impacted during or after transport. Many unacceptable symptoms have clear causes: for example, the presence of blackened soft tubers may indicate poor ventilation during storage or delivery, while the darkening of the flesh just under the skin is likely to indicate freezing, in which case wet spots may appear on the surface of the tubers. . Greening of the peel indicates excessive exposure to sunlight during storage or transport.
The transportation of potatoes, even with very strict adherence to the temperature regime, is associated with one potential danger, which is often overlooked. If cold potatoes are unloaded into a room with a warm, humid atmosphere (which, for example, often happens when seed potatoes are shipped in spring or summer), there is a serious risk of condensation, followed by anaerobiosis, followed over time by massive bacterial rot and silver scab. Even in the absence of condensation, there is still a chance of disease losses if the potatoes are stored in containers in warm, poorly ventilated conditions after unloading. It is reasonable (a few days before arrival) to allow the cargo to warm up to a temperature above the expected dew point in the room. The temperature of the unloaded potatoes must be above the dew point in the room into which the unloading takes place. Otherwise, you need to organize a quick drying of the product.
In non-obvious cases, it is difficult to determine whether the problem is caused by the original defects of the product or by improper handling during and after delivery. A thorough investigation will be required, carrying out the necessary analyzes, comparing the results of deliveries of potatoes of the same batch on other dates and to other addresses. In cases where the opinions of the parties differ, it is useful to involve independent experts, however, in terms of arbitrating the quality of potatoes, the regulatory framework of the Russian Federation is poorly specified. The potato trade is a rather specific type of business, since the product has a short life cycle, is very sensitive to environmental conditions, and its quality can deteriorate very quickly, moreover, many quality indicators are assessed subjectively. Therefore, Europe has long approved and applies a separate set of rules for the potato trade, which regulates, among other things, the procedure for peer review and arbitration (RUCIP-2017). These norms are universally recognized in European countries, it would be logical to take them as a basis for the development of a corresponding document in Russia. Regarding the deterioration of the quality of potatoes during transportation, RUCIP has the following clause: “If there is no reference to INCOTERMS in the contract between the parties, regardless of the agreed type of sale, with the exception of sales with delivery, the risk of deterioration in quality during transportation (of potatoes) shall be borne by the buyer, with the exception of cases where the seller is at fault either before or during loading. In every word of this wording, the essential conditions and circumstances of the delivery of potatoes are taken into account.
Thus, fresh potatoes have become a commodity of world trade and are transported throughout the year in significant volumes over long distances. The logistical assessment of the crop takes into account the specifics and optimal conditions for the supply of table, seed and technical potatoes, biological activity, high sensitivity and risks during the transportation of this product. Regulations for the transportation of potatoes have been developed for all categories of products and all types of transport. All essential terms of delivery must be fixed in contracts, the actual regimes must be controlled and documented. Problems of reducing the quality of potatoes during transportation are encountered, the establishment of their causes in many cases is possible only on the basis of a qualified and thorough analysis of all available information, including for the period preceding transportation.
Sergey Banadysev, Doctor of Agricultural Sciences Sciences, Doka-Gene Technologies LLC