How to measure and reduce postharvest losses in fresh produce supply chains?

By |2019-05-16T12:46:57+00:00agosto 14th, 2018|

How to measure and reduce postharvest losses in fresh produce supply chains? Interview with Dr. Lisa Kitinoja

Dr. Lisa Kitinoja is a Postharvest Extension Specialist with a PhD from Ohio University. Graduate education at the University of California, Davis in International Agricultural Development, vegetable crops and postharvest technologies. She also worked with Dr. Adel Kader for 30 years (1982 to 2012), and worked as an independent consultant in postharvest technology. She is the author of “Small-scale Postharvest Handling Practices” manual, founder of The Postharvest Education Foundation (PEF, a non-profit org in the USA), 2011.

1. What are the most critical aspects a producer needs to consider in order to limit or reduce fresh produce losses during the first-mile distribution phase of fresh horticultural value chains?

I have worked mostly with small-scale growers and I can tell you that of some of the problems that they have, a lot of them start with harvesting. So if they are not paying attention to the harvest index and if their harvested crops are under-ripe or over-ripe or also immature or over mature, all of these can cause problems because they will need to chill faster than the optimal temperature and time for that crop.

The second thing is there is very little understanding of how gentle handling is a bridge to reduce damage, sometimes you don´t really see the damage until later in the handling chain. You don’t see damage at the farm, such as those caused by tools or if you drop them into the ground. For example, with bananas, sometimes there are heavy bunches and they get bruised during harvest. If they are using containers to collect the produce that are rough inside then they are creating damage at that moment during harvest. So that first distribution creates damage that will show up later.

The third thing is what the produce is being packed into when it moves from the farm. If it is a packhouse or into a transport vehicle or temporary storage, it really matters what type of container it is being put into. For instance, in one of the places I work, they are still using baskets, sacks, or very poorly constructed containers that don’t provide any kind of protection, and they are stacked one on top of each other. So we recommend using sturdy containers and plastic crates, even if you are going to distribute the produce close to where the farm is.

And four, it is really important to keep the produce cooled. The producer needs to realize that as soon as they remove the product from the plant it is going to start deteriorating and they should cool it down immediately. The producer needs to at least provide shade, and if there’s any delay between the harvest and when the produce moves out of the farm, the producer needs to think about how to keep the produce out of the sun and to keep it cool.

2. What key skills, knowledge or technology do farmers and agribusinesses operating in fresh horticultural value chains need to have in order to reduce post-harvest losses and quality issues during the first-mile distribution?

 We are talking about so many different crops, fresh horticulture can be very perishable crops, root crops, it can be crops that ripen and so many kinds of food. So the farmer and the handlers first need to understand the crop and the specific post-harvest needs. They are a lot of ways to learn about that, such as manuals and guidelines for that specific crop. The farmer needs to understand the temperature it requires, the environment adequate for that specific crop, as well as ethylene sensitivity etc.

Then the second thing is the importance of identifying the causes and the sources of quality problems that can cause losses. They are specific things that affect crops, for instance, for some crops from the tropics and subtropics, the cooling temperatures can be too cold if they are handled in refrigerators or cold storage, so they can cause chilling injuries if that happens. So you have to learn the lowest safest crop temperature and then about the potential chilling injury for that crop. Often in places where there are limited resources, such as Africa and Asia, the farmers and small agribusiness will have one cold room and so they will mix different crops together, not being aware that one crop can cause damage to the other crops. This is especially important for those agribusinesses managing ripening fruits and also green vegetables, as they need to keep those two crops separated in independent storage facilities or in any transport.

3. Does lack of knowledge about post-harvest good practices play an important contributing factor in post-harvest losses?

Yes, many growers do not know much about how to handle the crop after the harvest.

I’m a specialist in education and agricultural extension, so I have been always been pushing access to knowledge and training, getting growers to learn things by using technologies and practices, and learning by doing. Growers don’t know much about the crop and its postharvest management. They consider themselves as producers, as spend most of their time taking care of the land, providing irrigation and all the things needed for growing the crop. So as soon as they harvest they kind of pass on the responsibility to someone else, and this becomes a factor contributing to a postharvest loss.

4. What are the major challenges for measuring produce losses during first-mile distribution? And why are producers often not able to collect this information appropriately?

Growers sometimes consider their work to be “all done” when the crop is harvested. So someone else will either purchase the crop such as a trader, buyer or retailer who will come to the farm and then the crop will pass to the hands of that person or company. So measuring at the farm level may or may not help the farmer at all because they don’t know what happens later in the chain, so there will be nothing to compare to.

So one of the biggest challenges is that in order to get any information, it implies that the crop will be weighed or assessed for quality at harvest and again later in the handling chain (at arrival at a distribution center or market) but this is rarely done. This requires people to have a lot of coordination and cooperation with each other along the chain and plan so they can repeat the measurement. For example, if the measurement is done at harvest, it has to be repeated once it reaches the distribution center and once again when it reaches the cooler or the market. Some crops are handled in bulk, other crops are packed into containers that hold a certain volume, and if crops are weighed or assessed for quality during packing it is typically done only once rather than via repeated measurements.

5. What are some practical ways for agribusinesses and farmers to measure produce losses during the first-mile distribution? What should they be measuring? And what methodologies should they use?

First, there must be cooperation between the growers, buyers, traders and they should plan this together so that they can follow the crop from the farm and the first-mile distribution phase. The measurements can be simple—the weight of a sample container or the quality of a sample of the crop (ripeness, color, freshness). These measurements need to be done initially at harvest (or packing) and then again at various points in the distribution chain. For instance, what is the weight and/or quality when the sample arrives at the pack-house? After pre-cooling? After transport? If you measure the weight at the farm, you will measure the weight of the container at packing and you will measure that again when you arrive at a cooler, transport, or market.

The methodology can be very simple, if you are looking just at the quality you can just measure something as simple as the color, to look at ripeness or an indication of freshness or whether is wilting. Then you need to make sure measurements are replicated, at least three times for each data point (start with three samples at harvest, measure again to get three data points after packing, three after cooling).

6. To what extent can access to small-scale, off-grid enabled cold storage facilities in rural areas help reduce post-harvest losses for smallholder farmers?

Cold storage for perishables can extend the time the grower has to reach the packhouse or market. Most perishables cannot be stored for a long time, so it is more of a logistical aid, for example, to make sure that during transport delays the produce is not left sitting in the sun.

7. Although pre-cooling fresh produce, to remove field heat, is crucial for assuring longer shelf-life of produce, very few producers in developing countries implement it. Why is this the case? And what can be done to promote pre-cooling?

This is a great question, because most growers, small and large, and also cold storage operators don’t realize that they need to pre-cool before putting the produce into a cold storage, in order to get the best results and to reduce the energy use in the cold storage. Most growers assume that pre-cooling is costly and will not provide any economic gain.

In some cases, growers do not have access to electricity or other sources of power.

About 10 years ago my colleague Jim Thompson and I were working on this topic, and we wrote an article on pre-cooling for small producers, and provided examples of lower cost methods – shade, evaporative cooling, hydrocooling, forced air, etc. http://ucce.ucdavis.edu/files/datastore/234-1594.pdf

The faster you can get the pulp temperature down or remove that field heat, not necessarily at the production but closer to that point (5-7 Has), it will push out that field heat faster, thus increasing the shelf life of the product and giving you more time. If the cold storage is taking produce at ambient temperature or that is hot from the field, then they are not going to be really able to provide the cooling services they are offering because it will take days for that produce to slowly get down to that set point temperature. Also, if you are bringing warm produce from the field and you are stacking it close to something that is already cold, you will be also affecting someone else`s produce.

Off-grid (solar powered) systems need to be demonstrated for growers, and they need to better understand what the costs and benefits will be. There is the assumption that precooling is costly, although this is usually wrong and if a farmer can get into a situation where they can precool produce, before putting the produce into a cold storage at the right temperature, you will be seeing a higher acquisition of farmers using pre-cooling and cooling technologies.

8. What types of post-harvest management projects and practices are you currently focused on?

As a consultant, I am working with large donor organizations (World Bank, USAID, FAO) to assess postharvest food losses and develop methodologies that can be used to assess losses in the field. Many of the documents and training manuals that I have developed are available online free of charge. “Small-scale Postharvest Handling Practices” manuals in 12 languages. http://postharvest.ucdavis.edu/Library/Postharvest_Center_Publications/

You can find many more documents and resources links and courses on the PEF website www.postharvest.org

With PEF I am managing postharvest e-learning programs, speaking at conferences and postharvest events and designing PTSCs (Postharvest Training and Services Centers). We offer a free e-learning program for young horticultural professionals that takes about one year to complete, where the trainee learns about loss assessment, tools,  resources for reducing losses, costs and benefits of making changes in postharvest practices, designing postharvest training programs and more.

For information on PEF e-learning programs and free training manual download: http://postharvest.org/postharvest_elearning_program1.aspx