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11/2/2013 7:00 AM

To Manage Freeze Damage <\n>in Your Apple Crop

Recent morning freezes have raised the question of damage to the remaining apple crop. Extension pomologist Jim Schupp tells us the fruit tissues of apples have sugar and other constituents that lower the freezing point of fruit below 32 degrees F.

The freezing point of fruit varies between varieties and with fruit maturity, probably due to differences in sugar content. Even so, apples begin to freeze at 28.5 to 28 degrees F. The lower the air temperature and the longer the exposure, the greater is the risk of damage.

A general rule is that apples will withstand up to four hours at 28 degrees before serious injury occurs, but it is difficult to give a hard and fast rule to predict injury based on minimum temperatures and duration, as the recovery depends not only on the extent of freezing, but also the rate of thawing.

During the time the fruits are frozen, they should not be touched or moved. Handling frozen fruits invariably leads to fatal damage in the form of deep and lasting bruising.

One must wait until the fruits have completely thawed before handing them. This likely means waiting several hours after the air temperature has risen above freezing.

Slow thawing is actually beneficial for preserving fruit tissue integrity for apples that just had a near-death experience. A fast warming or exposure to direct sunlight will make the damage worse.

Bins of fruit that must remain in the orchard overnight during potentially freezing weather should be left where they will be shaded from the morning sun — on the west side of a row, wood line or other tall structure.

Though the method is destructive and not very sophisticated, there is a way to determine if apples are frozen. Sample some and jab your thumbnail through the skin and into the fruit.

Fruit that is not frozen will “pop” as the skin breaks, and the resulting wound will be juicy. Conversely, fruit that is frozen will give the sensation of sticking your thumbnail into a popsicle, and the wound won’t be juicy.

The same test can be used to gain some confidence that the fruits have thawed long enough to be harvested or moved.

Fruit that experienced only a mild — 28 or above — freeze of less than four hours may recover and be perfectly salable but should not be considered candidates for long-term storage.

Such lots of fruit should be stored separately and pressure tested frequently during storage for evidence of fruit softening. Unacceptable softening is a key indication that the damage is worse than predicted.

Apples that were fatally frozen will exhibit flesh browning after thawing once the temperature has risen far enough for oxidation to take place. This browning can appear at the skin surface or below, and generally takes around 24 hours to appear, longer if temperatures remain cold.

After the apples have warmed enough to exhibit flesh browning, cut them open and inspect them. If browning appears, the fruit is obviously unfit for use.

It is also possible for fruit that does not have obvious browning to have serious freeze damage. This fruit will rapidly soften in storage. It is good only for making juice and only if processed right away.

Generally speaking in the apple business, your first loss is your best loss. If the fruit has been in a freeze that was too close for comfort, you should consider selling it for juice and telling your customer about the potential condition of the fruit.

If you determine that the fruit is going to be held and sold as fresh, such apples should be stored separately and pressure tested over several days or weeks to ensure they are truly sound.

To Understand Grain Price Trends

Last week, some export demand strengthened the prices for soybeans and corn. John Perkins of Brownfield Ag News reports soybeans were higher on short covering and commercial buying.

Demand remains strong with Russia buying 120,000 tons of U.S. beans for delivery this marketing year and the short-term supply is tight.

That was the third major purchase of U.S. soybeans last week. Past that, the trade’s watching the harvest with some delays over the near term, but long-term forecasts are generally considered good. Soybean meal was higher and bean oil was weak on the adjustment of product spreads.

Corn was higher on technical buying and spillover from beans. Ethanol demand is strong and corn’s also looking at harvest delays with a lot left to be harvested.

Still, export demand has been a little scattershot, and U.S. corn prices remain relatively high, limiting interest somewhat. Ethanol futures were lower.

Vietnam bought 400,000 tons of corn from Brazil, and Taiwan picked up 60,000 tons of corn, also from Brazil.

South Korea’s Corn Processing Industry Association canceled a tender for 55,000 tons of food-grade corn with the lowest offer at $254.82 per ton, and then bought 55,000 tons of either U.S. or South American food grade corn at $254.70.

South Korea’s Nonghyup Feed Inc. canceled a tender for 140,000 tons of corn due to high prices. This would suggest that corn prices are under downward pressure due to market resistance.

The wheat complex was higher on commercial and technical buying. Additionally, export demand for high-quality milling wheat is good, giving extra support to Kansas City and Minneapolis.

Jordan bought 100,000 tons of optional origin milling wheat and in a sell-buy-sell trade, Japan picked up 49,800 tons of feed wheat out of a tender for 180,000 tons.

Quote of the Week

“I’ve never seen a monument erected to a pessimist.”

— Paul Harvey

Leon Ressler is district director of Penn State Cooperative Extension for Chester, Lancaster and Lebanon counties.


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12/22/2014 | Last Updated: 5:45 PM