More predictability with MCP needed

Jake Gutzwiler said pear packers need to be able to use MCP accurately, effectively, and efficiently.

Fruit packers in Washington State say they’d like to feel more confident about using SmartFresh (1-methylcyclopropene) on pears to reduce problems with storage scald and enhance storability, but results are not yet predictable. What they need is a formula that will tell them how to treat a given lot of pears with SmartFresh so they can get the results they want.

Use of SmartFresh on pears involves a lot more management than using it on apples, Welcome Sauer, president of AgroFresh, which manufactures and sells the product, said during a discussion at the Washington State Horticultural Association’s annual meeting last winter.

Research is going on around the world—in AgroFresh’s labs, research labs, and many fruit packing houses—on how to successfully treat pears with SmartFresh, Sauer said. AgroFresh has seven researchers working in laboratories in ­Washington State, California, and Chile, who are ­analyzing over a ­million fruit samples a year.

For many packers, however, it’s been a case of trial and error so far, with some shipments ripening too slowly and ­others too fast. An incident where SmartFresh-treated pears were mixed in bins with untreated pears and diverted for processing was a learning experience both for the producer and the processor that received them, as the pears ripened at ­different times, Sauer said.

Dr. Jim Mattheis, postharvest physiologist with the U.S. Department of Agriculture in Wenatchee, Washington, said SmartFresh has proven effective for slowing ripening, controlling scald, and warding off disorders that are related to senescence in pears, but many factors can influence how well it works. These include: maturity of the fruit at harvest, the interval between harvest and treatment, the SmartFresh concentration, temperature of the fruit when treated, storage conditions, storage ­duration, and poststorage ­conditions.

Not like an apple

Jake Gutzwiler, quality control supervisor at Stemilt Growers, Inc., in Wenatchee, Washington, said SmartFresh does exactly what it’s supposed to do: delay maturity of climacteric fruit. “From that aspect, it’s a ­complete ­success,” he said.

“But a pear is not like an apple. On an apple, we want to delay maturity and keep the apple crunchy. On a pear, we want to delay maturity long enough so we can store it, and then turn it back on somehow.”

In small, controlled trials in a lab setting, the company has been able to treat pears and have them ripen perfectly, Gutzwiler said. But with commercial fruit, there’s been great variability. One lot of fruit might have a two-day delay in ripening, while in another lot, ripening might be delayed by five or six days.

“But, then, we also know we have a wide range of maturity at harvest and as we pull the fruit out of storage. What we don’t know is what’s the formula to make it stop ripening and then start ripening again and get it to the customer in perfect condition and then to the consumer in an ­edible state,” he said.

Gutzwiler said it’s obvious that a packer can’t just put five different grower lots into a room and treat them, and expect the same results. Packers will need a lot of information about each lot of fruit to determine how to treat it to get the best results.

Stemilt is using SmartFresh on pears, but believes it is rolling the dice in terms of the ultimate condition of the pears, he said. “How do we get to the point of using it accurately, effectively, and efficiently?”

Bob Gix at Blue Star Growers, Cashmere, Washington, said the biggest challenge, in his experience, is getting the fruit to uniformly ripen and fitting the treatment into the commercial system.

If a way could be found to treat pears and have them ripen predictably, SmartFresh would be particularly useful for fruit shipped to export markets that don’t have good cold storage, he said. It also has great potential as an alternative to the antioxidant ethoxyquin for scald control.

But packers will also need to have the discipline to treat and package fruit to ship to a specific place within a specific time frame and not be tempted to send it to another buyer instead, he said.

Variable

Jordan Matson, warehouse manager with Matson Fruit Company, Selah, Washington, said his company has seen variable responses in treated Bartletts. Some pears became overripe, while others didn’t ripen well.

Commenting on research showing that conditioning at 68°F for five days after storage can enhance the ripenability of treated pears, Matson said it would be challenging on a commercial scale to warm up the pears for a specific time because of the large volumes of fruit being handled.

“You almost need forced air to warm it up to get a consistent five days—if that’s what you’re trying to do—and forced air to cool it back down,” he said.

Another obstacle to using it on Bartlett pears is that pear canners will not accept MCP-treated fruit, Matson said. “If you treat it in the bin and want to run some third-grade or off sizes to the cannery, the canneries definitely don’t want SmartFresh.”

If there were some protocol that canners could use to ripen treated pears, that would open up the possibility of ­producers using it more on Bartletts, he said.

Argentina

Sauer said there are innovative packers around the world who are successfully treating pears with SmartFresh, but they are not sharing their secrets with their competitors. Argentine pear packers are using more SmartFresh than Washington producers are.

“Argentina is a couple of years ahead of Washington State in this technology,” he said. “We have shippers in Argentina who are storing Bartlett pears for six months at least in regular-atmosphere storage and selling a ­beautifully conditioned pear in the marketplace.”

Dr. Enrique Sanchez, researcher with the National Institute for Agricultural Technology at General Roca, Argentina, said Packham, an important pear variety in that country, tends to develop scald in storage, and SmartFresh will be an important alternative to ethoxyquin, which will be banned in Europe this year. The United Kingdom is the only European market that will not accept SmartFresh-treated pears, he added.

Sanchez said the main pear shippers in Argentina are using SmartFresh and finding that treated pears take longer to ripen.

Sauer said experience with treated Bartletts has shown that they can take longer to ripen to between three and five pounds pressure (which he refers to as the consumer zone of acceptance), but they stay within that zone for much longer than untreated fruit, which continue to soften and deteriorate.

“I think that’s a really desirable outcome,” he said. “That’s what we’re shooting for. I think over the next ­couple of years, we’ll learn a lot more and start to come to an agreement about what’s best.”