Increasing awareness about healthy eating drives health-conscious consumers to eat peaches (Prunus persica) because this fruit is a good source of antioxidants, including vitamin C (Hashem et al., 2019; Noratto et al., 2014). The United States occupied the fourth position in peach production worldwide, with 638,020 tons of used production in 2018 with a value of $511,226 (U.S. Department of Agriculture, 2019). Peach acreage in Florida had increased from 1231 in 2012 to 3000 in 2014 (Olmstead and Morgan, 2013; Olmstead et al., 2015; Singerman et al., 2017), though there has been a slight decrease with current estimates of ≈2000 acres (A. Sarkhosh, personal communication). One of the main drivers for increased production is the availability of new peach cultivars from the University of Florida/Institute of Food and Agriculture Sciences breeding programs that are firmer, more flavorful, and better adapted to Florida’s varied microclimates (Sarkhosh et al., 2016; Singerman et al., 2017). In addition, citrus (Citrus sp.) growers, facing declining production due to plant disease such as citrus greening (also known as Huanglongbing or HLB) caused by the bacteria Candidatus Liberibacter asiaticus, have started replacing citrus acreage with peaches (Nickel, 2018). During 2015, the Florida Department of Agriculture and Consumer Services (FDACS) Division of Food, Nutrition, and Wellness assisted 24 Florida school districts in procuring an estimated 108,595 lb of peaches and was responsible for their incorporation into school meal menus (FDACS, 2015). Considering the increasing demand for peaches, postharvest processes that extend shelf life need further study for the benefit of the producer as well as the consumer.
Peach, as a temperate, climacteric fruit (Guohua et al., 2012; Hayama et al., 2006; Minas et al., 2018; Tonutti et al., 1991; Zhang et al., 2011) undergoes rapid ripening, which accounts for its short shelf life and represents a serious constraint for its efficient handling and transportation (Hussain et al., 2008). For this reason, peaches are often picked at a preclimacteric stage to withstand the handling process. However, in Florida, ripening initiated (“tree-ripe”) peaches can be picked due to widespread planting of cultivars with the nonmelting flesh trait that imparts very firm texture (Sarkhosh et al., 2016). Owing to rapid ripening after harvest that results in a shortened shelf life, refrigeration is often used to store peaches. This has the beneficial effect of extending shelf life both by maintaining fruit quality and by reducing storage decay (Wang et al., 2005; Xi et al., 2012). Conversely, even though postharvest refrigeration prolongs shelf life of peaches, this fruit can easily suffer from chilling injury (CI) and thereby become more susceptible to microbial decay. CI, commonly called “internal breakdown,” can cause flesh browning and poor overall texture (“mealiness”) in the fruit (Anderson and Penney, 1975; Artés et al., 2006; Brovelli et al., 1998; Byrne, 2002; Crisosto et al., 1995, 1996; Lurie and Crisosto, 2005). As a result, several nondestructive methods have been developed that use acoustical or infrared (IR) energy to detect CI in peaches (Byrne, 2002), as well as irradiation treatment that inhibits ripening and decay (Hussain et al., 2008). However, such treatments still need more research before they can become commercially viable.
Proper temperature management has been shown to be critical in maintaining postharvest peach quality (Crisosto and Valero, 2008; Kader, 2003). However, current cooling practices used by peach growers often result in cooling delays up to 24 h, compromising potential quality. In many production areas, peaches are typically picked and placed in a cold room on the day of harvest and packed and shipped on the following day (De et al., 2017). This form of cooling (room cooling) is the slowest method and requires 20 h or more for fruit to achieve 7/8 cooling—a decrease in fruit temperature equal to 7/8 of the difference between the initial fruit temperature and the cooling medium temperature (Sargent et al., 2017). Tree-ripe peaches are already undergoing rapid, climacteric ripening when they are harvested, which makes them highly perishable, thus making temperature management critical for long distance marketing to be successful. In addition to ripening, the longer the delay to cooling, the more moisture is lost, and the more sensitive peaches are to bruising (Ahmadi et al., 2010; Opara and Pathare, 2014). The need exists to investigate the impact of cooling practices on postharvest quality and shelf life of peaches. Locally grown peaches have the potential to have far better quality than imported product during the harvest season. The increase in production of peaches and the growing demand is leading grower/shippers to explore alternative ways to expand their markets while still maintaining quality. With the increase in acreage and burgeoning markets for peaches comes a need for Florida grower/shippers to expand packing and cooling capabilities within the state. There is currently a lack of research on effective cooling practices, which is essential in decision making to assist in the upgrading of these facilities and the implementation of improved handling procedures.
This research was performed to compare and evaluate forced-air cooling (FAC) and hydrocooling by chilled water with sanitizer (HS) as alternatives to room cooling (RC). Determination of microbial load from the surface of untreated field (uncooled), and treated (cooled by RC, FAC, and HS) peaches (pre- and post-pack) were performed to compare the efficacy of different postharvest cooling methods. In addition, the effect of these cooling methods in maintaining microbiological quality during a 21-d storage was evaluated. The goal of this research was to increase the competitiveness of growers, packers, and shippers of fresh-market peaches by improving and extending postharvest quality and ensuring microbiological safety by investigating the efficacy of cooling methods and postharvest temperature management.
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