Chestnut (Castanea sativa Mill.) is one of the most important tree nuts in the world. According to the Food and Agriculture Organization (FAO) Statistical Database, the worldwide chestnut production is 1,998,880 tons. Chestnut fruits are highly regarded and widely consumed throughout Europe, America, and Asia. In addition, chestnuts are one of the most popular nuts in the oriental world. Chestnuts are mainly cultivated in China (1,650,000 tons), Republic of Korea (70,000 tons), Turkey (59,789 tons), and Italy (52,000 tons) (FAO, 2014).
Chestnuts are rich in starch and sugars, primarily monosaccharides and disaccharides such as sucrose, glucose, fructose, and raffinose (Bernardez et al., 2004; De la Montana Miguelez et al., 2004). In addition, chestnuts differ from other nuts for their low fat content which makes them ideally suited for high complex carbohydrate and low fat diets (Bounous, 2009) and they have a unique flavor and taste. Due to large proportion of moisture and sugar content, enzyme activity and pericarp characteristics, the shelf life of chestnuts is very limited (Correia et al., 2009). Therefore, chestnuts are frozen, cold stored, or dried to extend their storage period. However, the nuts have a high moisture content and are therefore susceptible to insect damage and fungal decay after harvest, resulting in high perishability (Miller, 2009; Tzortzakis and Metzidakis, 2012).
The main storage problems affecting chestnuts are the presence of insect worms (Cydia splendana Hb, Cydia fagliglandana Zel., and Curculio elephas Gyll) and the development of fungi, mainly Cyboria, which blackens the flesh, but also Rhizopus sp., Fusarium sp., Collectotrichum sp., Phomopsis sp. (Breisch, 1993; Washington et al., 1997; Wells and Payne, 1980; Xiao-qing et al., 2009), Aspergillus sp., Penicillium sp. (Marinelli et al., 2009), Alternaria sp., Trichothecium sp., Botrytis sp., Fusicoccum sp., Phoma sp. (Xiao-qing et al., 2009), Sclerotinia sp., and Gibberella sp. (Donis-Gonzalez et al., 2009a).
Chestnut quality is measured by external factors such as color, shape, size, surface blemishes, and molds, which are very important for consumer acceptance. Internal disorders may result from anatomical or physiological changes such as moisture loss, chemical conversion, discoloration, senescence, microorganism attack, cell breakdown (physiological decay), or insect injury (Upchurch et al., 1993; Wang et al., 2000). Weight losses due to dehydration and infestation by insects and microorganisms are the two main problems in chestnut preservation (Marinelli et al., 2009; Pinto et al., 2007; Talasila et al., 1995; Tian et al., 2009). Different postharvest preservation treatments have been used to preserve the nutritional and sensory properties of the fruit (Bounous, 2002; Conedera et al., 2005) and to keep the fresh commodities against physiological and biological losses during postharvest periods, such as water curing (Bassi et al., 2005; Jermini et al., 2006; Marinelli et al., 2009), low temperature, MA storage (Miller, 2009), and CA storage (Tzortzakis and Metzidakis, 2012), coatings on the surface of chestnut fruits (i.e., chitosan, carrageenan) (Tian et al., 2009), and various chemical sanitizers (i.e., hydrogen peroxide, peracetic acid, ozone) (Donis-Gonzalez et al., 2009b). Notwithstanding, in Turkey, chestnut growers are not used any treatments to harvested chestnuts to reduce contaminants and water losses before storage.
Chestnut fruits should be considered as fresh fruit for storage purposes because they have a 40% to 45% humidity ratio under normal conditions (Karaçalı, 2004). The humidity ratio of fruits should be maintained within a certain level to ensure good storage. Cold storage (CS) is the best method to ensure appropriate storage conditions for fruit (Soylu, 2004). Chestnuts can withstand CS because they are not susceptible to damage caused by low temperatures. The best preservation conditions for chestnuts are −1 to −2 °C (Jermini et al., 2006; Rouves and Prunet, 2002) with a relative humidity (RH) of 90% (Mencarelli, 2004).
Harvest and postharvest losses are high due to incorrect storage methods (SM) and nut quality is threatened by pest and diseases. Many SM exist to prolong and maintain the quality of nuts but many growers lack the technique (Bounous, 2009).
Miller (2009) stated that, quality of chestnut has two major components: characteristics and condition. Condition is mainly determined by environmental factors, especially postharvest handling, and the time interval after harvest. Condition is comprised of attributes like moisture content, insect infestation, fungal decay (mold), and sugar content. The most important environmental factors are temperature and humidity. These factors directly affect the moisture and sugar content of chestnut kernels.
In Turkey, chestnut growers typically store their crops using traditional methods. For example, chestnuts are buried with their burs in a pit under trees in the orchard and are covered with plants such as fern. This is the most commonly used method, especially in the Aegean Region in the western part of Turkey. Using this method for postharvest storage, the moisture level of the chestnut fruit is maintained and the sugar content increases from the time that the fruit separates from the burs until the middle of winter (Soylu, 2004), after which the nuts are sold.
Extensive research has been conducted on the nutrient content of chestnuts, effect of storage on fruit quality properties, and protection against microbes. However, there are no studies on the effects of different SM on the quality parameters of chestnuts. Some researchers evaluated soluble sugars, starch, and polyphenols as quality parameters, of the chestnut kernel in their articles (Cristofori et al., 2009; Tian et al., 2009; Portela et al., 2009; Vasconcelos et al., 2009).
To maintain the quality and extend the shelf life of chestnuts, it is essential that they are adequately stored. This study aimed to evaluate the effects of different SM (i.e., traditional storage (TS) and CS) and length of storage (0, 15, 30, 45, and 60 d) on the quality attributes of chestnut fruits (i.e., kernel and shell color, water activity, total sugar, total starch, total carbohydrate, and tannin content).
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