Effectively Cooling Peaches Post-Harvest

Peaches were a coveted and pricey luxury in the 16th and 17th centuries, when Spanish explorers brought them to North America. Although they are more accessible today, they are still a delicious snack and are enjoyed in both desserts and savory dishes, not to mention their prized spot as an iced tea and beverage flavoring. While a growing peach requires a specific cycle of precipitation and increasing temperatures to thrive, they are best preserved using appropriate methods for cooling peaches after harvest.

General Facts About Peaches

Peaches are categorized into one of two main groupings – clingstones or freestones. Clingstone varieties consist of flesh that grips tightly to the pit while freestone peaches tend to cleanly separate. The main difference between these varieties is that cling peaches are better for canning while freestone peaches can be eaten right after picking. Peach trees flower in March and produce a mature harvest in the summer heat, as long as they do not experience a late frost, which tends to kill the blossoms.

There are hundreds of cultivars of peaches bred for less fuzz, more color, or levels of firmness. This has led to varieties that are easier to pack and ship, some with more juice and flavor and others that are easier to wash and eat fresh. Most significantly are the variety called nectarines, which are so popular as to have their own name and their own distinct cultivars as well.

Information About Cooling and Storing Peaches

Peaches are a delicate fruit, and deciding when to harvest can be challenging. A peach should be ripe enough to cultivate flavor and yet not so developed as to soften or bruise during packing and shipping. The art of picking peaches is developed over time and experienced pickers are an asset to an orchard. Often times the same grove will have to be picked over multiple times to ensure each piece of fruit is removed at the peak of freshness. In order to ensure this effort isn’t for naught, it’s important to use appropriate methods for cooling peaches after harvest, and storing them in the meantime. The principal factors are:

Handling – Peaches are prone to bruising. The thin skin and flesh fruit can be easily damaged, so careful packaging is necessary to keep them protected. A damaged peach will release ethylene which causes other peaches to over ripen and can ruin an entire crate of fruit.

Temperature – Like many fruits, peaches will continue to ripen as they are exposed to heat. To counteract that tendency, the fruit should be cooled and stored at 31°F-32°F. Cooling peaches will only stave this off for so long before rot or internal breakdown occurs. A peach with a chilling injury will fail to ripen when the temperature is increased causing dry flesh and discoloration.

Relative Humidity – Peaches are mostly water, and should be exposed to high humidity in order to thrive in storage. Levels of 90-95% are necessary to ensure peach moisture.

Shelf Life – Peaches have a relatively short shelf life compared to other fruits. They can be stored for approximately 2-4 weeks, after which they are unlikely to be appetizing or safe to eat.

Methods of Cooling Peaches

Peaches need to be pre-cooled to quickly remove field heat and bring down overall fruit temperature. This should occur within the first 24 hours of harvest to ensure the best quality. Simply refrigerating the fruit will not be an effective method of temperature reduction particularly for fruit that will be shipped and continue to be stored. The following are effective methods of cooling peaches after harvest:

Hydrocooling – The longer that peaches are kept at the high field temperatures after picking, the more quickly they will be damaged and over ripen. Hyrdocooling is a quick and efficient method of cooling fruit that consists of running the fruit under cool water. This reduces heat rapidly while also cleaning the fruit at the same time.

Forced-Air Cooling – Instead of simply setting peaches in a freezer, forced-air cooling adds circulation by using fans to move the cold air rapidly around the fruit. When used alone or in conjunction with hydrocooling, forced-air cooling removes field heat to help ensure a good crop.

Farmers work hard to harvest their peach crops and need a quality product to meet their cooling and storage needs. Using modern methods for cooling peaches after harvest is the key to winding up with the most desired and sellable crop. SEMCO/SEMCOLD LLC offers industrial cooling systems that are designed and manufactured to individual specifications ideal for keeping peaches cool until delivery and consumption.