- The United States provides one quarter of the world’s peach supply.
- Peaches are a member of the rose family
- Peaches are a stone fruit.
- There are hundreds of varieties of peaches, but they are mainly sold based on their flesh color of yellow or white.
- Peaches must be hand-picked off trees and not all fruit ripen at the same time
- Once picked, they must be picked in the early morning and cooled rapidly to prevent further ripening
- Peaches are a low glycemic fruit
Peaches (Prunus persica), from the rose family (Rosaceae), are a popular fruit consumed most frequently during the summer months. Peaches originated in China and spread across Asia and into Europe before eventually making their way to North America. The first peach tree was grown in Florida in the 1500s. Large-scale peach production the United States began in the 19th century. (Warner and Johnson, 2015)
Peach trees can grow up to 21 feet but are usually cultivated to be around 13 feet tall. The life of a peach tree is between eight and ten years on average but can be up to 25 years. They must be grown in areas that do not have severe cold (-10°F to -15°F) but also cannot grow in areas with mild winters because of a minimum cold temperature requirement for proper fruit set. This makes locations such as Colorado, Georgia, California and Michigan perfect for growing these fruits.Peaches are characterized by a fuzzy exterior, yellow, red, or white colored interior and a large pit in the middle. Peaches are categorized into either “clingstone” or “freestone” where the flesh either clings to the stone or is easily freed from it. Freestones are peaches that have a pit that easily separates from the ripe fruit while clingstones have a pit that adheres to the flesh. Freestone peaches are the most consumed fresh in the US and the two most popular varieties are the Elegant Lady and the O-Henry. Clingstone peaches are commonly used to make canned peaches. Overall, peaches are a prominent fruit in the United States and are frequently enjoyed in cobblers and pies as well as fresh. (Wisconsin Department of Public Instruction)
Historically, foodborne outbreaks and recalls of peaches in the U.S. and Canada have been rare. During the summer of 2020, the U.S. Centers for Disease Control and Prevention (CDC), state partners, and Canadian officials (Public Health Agency of Canada and Canadian Food Inspection Agency), announced an investigation into an outbreak of Salmonella Enteritidis infections in multiple U.S. states and Canadian provinces associated with the consumption of bagged peaches. By interviewing ill people, 81% reported that they ate fresh peaches in the week before the illness onset. Grocery store records were collected, and it was determined that Wawona Packing Company (Fresno, California) distributed the peaches that were associated with salmonellosis. (US FDA 2021)
A voluntary recall notice was released in August 2020 by the U.S. Food and Drug Administration (FDA) on behalf of Prima® Wawona (Fresno, California). The notice specified that the bulk/loose peaches distributed and sold from June 1 through August 3 and its bagged Wawona and Wawona Organic peaches distributed and sold from June 1 through August 19th could possibly be contaminated with Salmonella. (US FDA 2020)
PulseNet, a national subtyping network, was used to compare the genetic fingerprints of bacteria of various isolates associated with documented infections to connect the cases. The CDC reported that 101 people became infected with the organism related to consumption of those peaches and of those cases, 28 reported needing hospitalization. Fortunately, there were no deaths reported for this outbreak. (CDC 2020)
The epidemiological and traceback investigation identified a large grower/producer’s packinghouses, cooling facilities and/or orchards as a potential source of the peaches and helped prioritize investigational activities. Whole genome sequencing (WGS) was utilized to evaluate the peaches and surrounding environmental samples from the orchards. Multiple Salmonella isolates from the fruit and peach tree leaf sampling activities conducted during this investigation genetically resembled historical chicken and cattle isolates. These animal isolates were not associated with this outbreak or any known foodborne illnesses.
Several plausible scenarios were put forth to explain potential contamination. Geospatial analyses of the orchards producing fresh peaches during the period of interest along with WGS analysis that demonstrated closely related Salmonella isolates from peach/leaf and historical animal samples. Fugitive dust via airborne transmission with possible origin from adjacent animal operations (e.g., poultry or cattle) was proposed as the most likely source.
The large grower/producer cooperated with FDA throughout the investigation and were responsive to the agency’s findings and recommendations. As of October 16, 2020, the CDC reported that the outbreak appeared to be over (CDC 2020). An executive summary was published by the US FDA in 2021 (US FDA)
In addition to the 2020 outbreak, there have been three other outbreaks ranging from 1999 to 2014, where peaches were associated with foodborne illnesses according to the CDC’s National Outbreak Reporting System (CDC 2018). In 1999, the state of Maryland experienced an outbreak that affected two individuals, resulting in one individual hospitalized. The suspected source of the outbreak was catered food prepped off-site. The CDC reported no deaths for this outbreak. In 2012, the CDC reported an outbreak at a college in Ohio. Seventeen individuals were affected, and no hospitalizations were reported. In 2014, a multistate outbreak of Listeria monocytogenes was reported and confirmed to be linked to a private home setting. Two individuals were affected. Both reported hospitalization and one death resulted from this outbreak. (CDC 2018)
Production Level 1 – Location
Growing peaches requires special soil and climate conditions for maximum yield and quality. Most commercial peaches are produced in four states, including California, South Carolina, Georgia, and New Jersey, but there are a total of twenty states in the U.S. that produce peaches commercially (Agricultural Marketing Resource Center. Peaches. 2019) Colorado is in a unique situation in the USA as it receives the highest “farmgate price” (price/kg) in the country due to its exceptional quality at harvest. (USDA-NASS, 2020). Loamy soil consisting of 28-50% silt, 2-27% clay, and less than 52% sand is required to promote efficient water retention, proper drainage, and nutrient availability (Taylor). Unlike many other fruit crops, most peach cultivars are self-fruitful, so there is minimal need for other cultivars to be used specifically as pollinizers. This allows cultivars to be planted together in solid blocks for easy harvesting. In the U.S., peach growers are starting to build orchards suited for mechanization (i.e., dwarfing rootstocks, high-density plantings and planar canopy architecture/training systems). These are facilitated using trellising, using materials such as bamboo or metal conduit poles attached to the trellis to serve as temporary training aides from planting to production, to train straight scaffold limbs in the desired directions. The canopy architecture and orchard design facilitate the use of vehicle-mounted string thinners (e.g., Darwin). Thinning the number of flowers and/or small immature green fruit is necessary for large fruit size and high -fruit quality at harvest. Due to a lack of commercially available and reliable chemical thinners for peaches, they must be hand or mechanically thinned. As mentioned previously, mechanical thinning can be accomplished by using a string thinner which can be mounted to vehicle-mounted string thinners. (Shane)
During the growing season, peaches require a generally warm climate with lots of sun, high soil moisture content and where frost is not expected past April or prior to October due to early blooming in Spring and/or late ripening /acclimation in Fall. In dormant stages during fall and winter, peach trees must have between 50-1,000 hours, depending on the cultivar. Chilling hours include hours spent between the temperatures of 32°F and 45°F for proper chilling accumulation. This enables maximum bloom in the Spring to achieve maximum harvest in the spring (Rhoades).
Production Level 2 – Peach Harvest
Peaches are harvested slightly before they are ready for consumption (i.e., commercial harvest maturity of ~50 N or flesh firmness); thus, ripeness is achieved after they reach the consumer as peaches are a climacteric fruit as they ripen off the tree. (Taylor)
Harvest usually begins in May and can continue through the end of August/early September depending on the location and strength of the bloom. Given the canopy complexity of traditional peach orchards and training systems, all fruit will not ripen at one. It is normal protocol to conduct two to four picks per tree at harvest. Length between harvests is dictated by the weather as well as location of the fruit within the tree. The more sun-exposed fruit will ripen faster than shaded fruit. When ready for harvest, peaches are handpicked from trees in the cool morning hours and transported to a processing facility. At the processing facility, the peaches are run through a hydro-cooler and cooled to a temperature between 32°F and 37°F to prevent further ripening (Taylor) The hydro-cooling process is one of the most vulnerable steps for microbial contamination because water is used, so it is crucial that the water being used is tested and changed as needed to reduce the risk of microbial transfer to the fruit. After cooling, peaches are washed, defuzzed, and filtered through a grater that removes leaves. (Yancey) At some processing facilities, fungicides are applied to the peaches to prevent fungal contamination during distribution (Taylor)
Production Level 3 – Post-Harvest and Distribution
Peaches can only be stored for two to three weeks due to chilling injury susceptibility. The use of controlled atmosphere conditions, reducing oxygen to 4% and increasing carbon dioxide to 4%, can be used to reduce respiration rates to control ripening and extend storage life.
After processing, peaches are sorted based on quality and size, then are packaged in padded boxes and loaded onto refrigerated trucks for distribution. These trucks are designed to keep the peach temperature between 31°F to 34°F, and to keep relative air humidity at 90% to prevent deterioration (Taylor) These refrigerated trucks then transport the peaches to supermarkets and smaller grocery stores, restaurants, and other businesses (Yancey).
Peaches contain natural sugars called polyol – specifically, d-glucitol; a 6-carbon polyol. It is stable at high temperatures, and unlike other polyols, it has a high hygroscopicity. Regarding the gut microbiome, moderate doses of polyols have been shown to shift the microbiome toward an increase in Bifidobacteria spp. in healthy individuals and may therefore be beneficial as a prebiotic. However, polyol ingestion can lead to intestinal dysmotility in patients with Irritable Bowel Syndrome (IBS). (Lenhart & Chey, 2017)
Seeds and pits should never be crushed or placed in a blender for consumption as they contain amygdalin which breaks down into hydrogen cyanide when ingested. (National Capitol Poison Control, 2021)
In the last decade, total production of new yellow and white flesh peach cultivars with different titratable acidities and flavors has increased rapidly. Consumption, however, has fluctuated. USA peach consumption has declined over the last few decades from 3.0 per person in 1980 to 0.96 per person in 2019. (USDA-NASS, 2020; Crisosto, 2002) This is due to poor consumer acceptance of inconsistent fruit quality has led to a dramatic decrease in production from 1,002 kilotons (Kt) in 2007 to 560 Kt in 2020 (USDA-Nass, 2020). Consumer surveys have associated low peach consumption mainly to the lack of consumer understanding between mature and ripe peaches, and to the presence of flesh browning and flesh mealiness (chilling injury or internal breakdown). (Ware, 2019) The consumption of peaches, although it has been on a slow decrease still results in a significant number of pounds per capita in the United States.
As exemplified in a study conducted by Consumer Goods & FMCG, the U.S. consumption of fresh peaches was approximately 2.13 pounds per capita in 2019. (Shahbandeh, 2020) The amount of fresh peach consumption has been on a steady decline since the year 2000 when consumption of fresh peaches was reported to be approximately 5.3 pounds per capita. (Shahbandeh, 2020) This decline in consumption can be linked to various factors including lower quality of wholesale peaches, increased competition from imported tropical fruits, and berries that can now be bought year around. (Marini, 2019) Another factor that can be attributed to the decline is related to lack of consumer knowledge of ripe fruit selection, susceptibility of peaches to bruising and their short shelf life. (Marini, 2019)
Peaches are a low-glycemic fruit, which means they have a minimal effect on blood sugar. The glycemic index for peaches is 28 and glycemic load is 4, placing them in the lower ranges for fresh fruit.
The following nutrition information is for one one small peach measuring approximately 2.5 inches in diameter (130g). (Ensle, 2015). A cup of peaches contains approximately 11.1 milligrams of vitamin C, this results in 12-14% of the Recommended Dietary Allowances (RDA) according to the USDA. (Ware, 2019) Vitamin C is a strong antioxidant that has been linked to reducing the risk of cancer. (Ensle, 2015) Vitamin C can also aid in collagen production which is connected to maintenance of healthy skin. (Ware, 2019) Peaches also have a fair amount of fiber with 2.52 g of fiber per cup which equals to approximately this 7.5% of the daily recommend dose. Peaches contain a few other vitamins and nutrients, including vitamins A, E, K, iron, and potassium. (Ware, 2019; USDA, 2019) One cup serving of peaches is made up of 1.53 g of protein and 0.42 g of fat. (Ware 2019; USDA 2019) Peaches are very low in cholesterol and sodium containing 0 g of cholesterol and sodium in a 1 cup serving. Fresh peaches have a sugar content with 14.10 g of sugar/1 cup serving size. (Ware, 2019 USDA, 2019)
- Agricultural Marketing Resource Center. Peaches. 2019 March https://www.agmrc.org/commodities-products/fruits/peaches downloaded March 28, 2021.
- Centers for Disease Control and Prevention (CDC) (2018, December 7). National Outbreak Reporting System (NORS). https://wwwn.cdc.gov/norsdashboard/
- Centers for Disease Control and Prevention (CDC). (2020, October 16). Outbreak of Salmonella Enteritidis Infections Linked to Peaches. Current Outbreaks. https://www.cdc.gov/salmonella/enteritidis-08-20/index.html
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- U. S. Department of Agriculture. Food Data Central. Yellow Peaches. Published April 1, 2019. https://fdc.nal.usda.gov/fdc-app.html#/food-details/325430/nutrients downloaded June 3, 2021.
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Colorado State University Students
Bianca Chima (Food Science and Human Nutrition) Carly Lipke (Environmental Health), Jason Boedigheimer (Environmental Health), Ada Wilmer (Environmental Health)
Brendon Anthony, MS (Horticulture Ph.D. Student CSU), Jeff Piper, MS (Horticulture Ph.D. Student CSU)