Posts Tagged: postharvest
Ripening Fruit
You no doubt have noticed that those green bananas you bought at the store a few days ago have...
Hot Avocados Dont Ripen Right
California avocados often are exposed to high temperatures after harvest, either in the field or during preconditioning (ethylene treatment), especially in summer. It's been known that long periods of high temperatures can delay ripening time and reduce fruit quality, but a new study indicates pronounced effects after only short periods of high temperature following harvest. Authors of the study concluded that it's important to maintain avocados at temperatures below 25°C following harvest and that the ideal temperature to ripen the fruit is 20°C. The authors also found that ripening below 20°C resulted in significantly longer ripening times and resulted in poorer coloration of the ripened fruit.
Mary Lu Arpaia, UC Cooperative Extension specialist, Jim Sievert and Sue Collin, staff research associates (retired) in the Department of Botany and Plant Sciences at UC Riverside, working with David Obenland, research physiologist with the USDA Agricultural Research Service, Parlier, studied for two seasons holding avocados from multiple harvest times for the first 24 or 48 hours of the ripening period at high temperatures (20°C to 35°C), with and without ethylene. In the third season, they made a detailed assessment of ripening temperatures (15°C to 25°C) on ripening time and fruit quality.
Results from the first two seasons showed that even a 24-hour exposure to temperatures of 25°C and above inhibits ripening and increases postharvest disorders such as stem end rot and body rot. In season 1, the incidence of stem end rot increased from 9.7% at 20°C to 32.3% at 35°C, and body rot increased from 3.9% to 20.2% for the same treatment comparison. Ethylene applied during the exposure period was ineffective in preventing the disorders.
In the third-season trial, temperature was also shown to be critical. Fruit ripened below 20°C took slightly longer to ripen. Additionally, the authors found that the ripened fruit at either 15°C or 18°C remained more green then fruit ripened at the higher temperatures. Avocados ripened above 20°C were more likely to develop pink discoloration in the mesocarp. Ripening temperature had no effect on overall likeability, or ratings of grassy or rich flavor.
Arpaia ML, Collin S, Sievert J, Obenland D. ‘Hass' avocado quality as influenced by temperature and ethylene prior to and during final ripening. Postharvest Biol Tec. 2018. 140:76-84.
Photo: Damaged fruit from the recent heat wave was more than 24 hours of overheating on the tree
avocado fruit hot
Hot Mandarins. What to Look forward to After a Fire
Mandarins, also known as “zipper skins” and “easy peelers” can have very fragile peels/skins/rinds/exocarp that make them easily subject to more damage than most oranges and lemons. Some are a bit tougher skinned than others, but some are so fragile that any rough handling often prevents them from going through conventional packing operations.
These skins were recently put to the test in the recent fires in Ojai. There was a mix of different varieties - ‘Pixie', ‘Gold Nugget', ‘W. Murcott', ‘Yosemite Gold', ‘Tahoe Gold' and others. Some of them were more sensitive than others, some were closer to the fire, all were affected by smoke to some degree. In Matilija Canyon where smoke was present for many more days than in the east of the Ojai Valley and possibly more ash, the trees have started flowering sooner. That might be temperature difference, either cooler or warmer, so it is hard to say how much effect the smoke has had versus, the ash and/or heat. Smoke has many different gasses in it, one of which is ethylene which is a naturally occurring ripening agent. Smoke not only has gasses, but it occludes the sun so less or more or altered light might have an effect on these fruit. It's not a controlled experiment, so some little scientist is going to have to come along and wriggle out these different effects. Whatever. Fire and smoke have an effect on mandarins as we have seen in other crops, such as cherimoya, avocados and other citrus.
Heat damage. Fruit facing the fire.
Ash effects on fruit coloring. Fruit was covered with ash for several days until rain washed it off. Might be a pH effect (ash is alkaline), temperature effect, uneven light radiation, or other…….
Same sort of uneven coloring, that actually looks like an ashy color, but the ash has washed off the cluster by rain
And here's something interesting where fruit facing the fire is much lighter colored than fruit facing away from the fire. Here are two pieces of fruit, one from the side directly facing the fire, and the other from the other side of the tree. The side of that fruit facing the fire was also lighter colored. So, it had an effect through the canopy (small tree). The canopy was otherwise intact, unaffected heat or flames.
Oh yeah, and there is the characteristic fruit drop from either the heat, smoke gases, water stress or ….
And then there's the fruit that looks like it had actual embers on the skin.
If the tree survives and keeps its green leaves, sometimes the fruit is affected in ways that don't appear for a while. The peel may be affected, but in many cases the fruit is just as sweet as it could be. It just looks terrible. That might even be a selling point. "Here have a wonderous piece of history that braved the horror of the Ojai fires."
Connecting with farmers over pineapple postharvest practices
At the end of a long year, sometimes it helps to reconnect with what motivates your work.
For Karin Albornoz — a Ph.D. student who works in the Diane Beckles Lab at UC Davis on molecular biology related to tomato postharvest chilling injury — that means getting out into the world to work directly with small-scale farmers.
"I spend so much time in the lab," she said. "Sometimes I spend a whole day in the lab extracting RNA or writing a paper. This reminds me why I am doing this work: to make a real-world impact."
Just over a week ago, she returned from a trip to Uganda where she did exactly that. In partnership with a local organization called Ndibwami Integrated Rescue Project (NIRP), Albornoz shared her expertise with farmers through several hands-on workshops about improving harvest practices and postharvest handling of pineapple, passion fruit and tomatoes. Her work was supported by the Horticulture Innovation Lab, an international agricultural research program led by UC Davis with funding from the U.S. Agency for International Development as part of Feed the Future, the U.S. government's global hunger and food security initiative.
Though Albornoz has worked with rural farmers before, this was her first time working in Africa.
"Everywhere I looked, things were growing. There were people working in the field, women cooking, and everyone was working with food," she said. "I know there's a lot of stigma – when you talk about Africa, you see people's faces change and they're thinking about things like drought and famine and starving children. But what I saw doesn't fit that stereotype. The challenges they are facing seem to be about not having access to opportunities."
The workshops she led are part of the NIRP organization's efforts to connect farmers with more lucrative markets that pay higher prices for quality produce.
In this 2-minute video, Karin Albornoz visits a pineapple farm, leads a pineapple training and discusses next steps for this project led by NIRP in Uganda. The video clips and photos were taken by Karin while she was working and edited by Hallie Casey for the Horticulture Innovation Lab.
For months, Albornoz has been in contact with NIRP and making plans for the farmer workshops. She prepared postharvest handling manuals for each crop — pineapple, passion fruit and tomato — and asked questions to better understand local resources and the farmers' existing knowledge.
During her 2 weeks in Uganda, she visited farmers' fields and led three full-day workshops. The first workshop for about 50 farmers focused on pineapple — starting with understanding local quality parameters for this fruit, then best practices for harvesting, sanitation, storage and transportation. The second workshop was focused on tomato, with a similar structure, and the third workshop on passion fruit.
Her favorite moment? The farmers' first chance to use a refractometer, to measure soluble solids and learn about sugar levels in the fruit. The refractometers were part of a small toolkit the organization will continue to use.
"They were excited to handle this device and see, in numbers, how the sugar levels of the fruit changed depending on the stage of maturity," she said. "Everyone in the room had a chance to try it."
The experience reinforced her commitment to working with farmers and solving agricultural problems.
"A major mistake is to think that you are going just to train or teach other people because those people are always going to end up teaching you too," Albornoz said. "I made a promise to myself years ago, a personal commitment to working with people in vulnerable situations. I have to do this. Working in agriculture can be a very powerful tool to have an impact in the world."
As Karin's mentor and an Associate Professor in the UC Davis Department of Plant Sciences and Agricultural Experiment Station, Diane Beckles supported Karin's work outside of the lab and views such an experience as important to scholarly development.
"Something magical happens when we teach and engage in outreach," Beckles said. "We often deepen our understanding of what we are teaching, and interacting and engaging with others changes us in that process. It alters how we view and think about science in a way that is positive and rewarding, even though it is not easily quantified."
More information:
- More about Trellis Fund projects with the Horticulture Innovation Lab
- Pineapple recommendations from the UC Postharvest Center
thumbnail: Karin Albornoz leads a workshop in postharvest handling of pineapple in Uganda.
Red Discoloration in My Avocado Flesh
The questions that come in stump many of us, but we often have ways of finding answers. Here's a recent request and Mary Lu Arpaia's response. She's one of our Postharvest Physiologist Specialists.
The Question:
"I am an extension specialist in NH, and I work with (mostly temperate!) fruit/veg crops. A consumer has reached out to the NH Division of Public Health here, with concerns about an avocado they purchased. I'm reaching out to you because you have written some outreach materials relating to avocado, and I suspect that you are much more familiar with this crop than we in New Hampshire are.
Would you have any insights about red discoloration inside an avocado fruit (see attached photo)? It does not look like typical chilling injury to me. Any thoughts would be welcome. Thank you for your time!"
Mary Lu's Response:
"You occasionally see this problem in ripe fruit, especially in lower maturity fruit.
Anyway the best guess is that it is phenolics from the seed coat leaking into the flesh of the fruit.
Not dangerous but the affected flesh may be bitter. I would cut it out and eat around the discolored flesh which is surface only."
Consumers in far away places often will see problems that we in avocado growing regions may never see. Increasingly though, the fruit is grown not so close to home and has traveled long distances, been handled by many different people and treated in less than acceptable fashion. So we may see more fruit problems in California as we import more fruit.
avocado red staining