Toona sinensis (A. Juss.) Roem (Figure 1) belongs to the Meliaceae family and is commonly called Chinese toon or Chinese mahogany. It is a woody perennial deciduous tree [1]. T. sinensis has a cultivation history stretching back more than 2000 years in China [2]; it is widely distributed throughout China, ranging from Liaoning in the east to Gansu in the west, Guangdong, Guangxi, and Yunnan in the south, and southern Inner Mongolia in the north. Of all the provinces, Anhui, Shandong, Henan, and Hebei have the most areas under T. sinensis cultivation ^[3][4][3,4]. T. sinensis is a medicinal and edible vegetable, and different tissues of this plant have been used to treat a wide variety of diseases ^[5][6][5,6]. Phytochemical investigations of T. sinensis have showed that its main constituents include terpenoids, phenylpropanoids, and flavonoids ^[7][8][9][7,8,9], and that the plant has many pharmacological activities, including anti-tumor, anti-oxidant, anti-diabetic, anti-inflammatory, antibacterial, and anti-virus action ^[10][11][12][10,11,12].

T. sinensis is divided into two types based on the color of tender leaves and petioles: red T. sinensis and green T. sinensis ^[13][14][13,14]. Red T. sinensis is rich in anthocyanins, thus the leaves and petioles are purple [15]. Red T. sinensis is more popular with consumers. This plant has a short harvest period, and storage is difficult; the edibility and commodity value is lost after 2–3 days at normal temperature [16].

Storage environmental conditions, including temperature [17], humidity [18], gas composition [19], etc., have been shown to affect the quality of the T. sinensis buds. Currently, researchers often use physical, chemical, and biological means to store and preserve T. sinensis buds. Although the principles of the three means are different, they all delay the duration and rot process of T. sinensis by controlling the water evaporation, respiration, and relative humidity of the environment of this plant and improve preservation time and quality of T. sinensis buds.

Temperature control preservation technology mainly includes low temperature preservation, low temperature and high humidity preservation, and quick-frozen preservation. Low temperature preservation can delay the metabolic process of T. sinensis after harvest; the buds of T. sinensis are packed into a plastic bag and stored at 0 °C, and can be stored for up to two months [20]. The low temperature and high humidity preservation method can slow down the loss of nutrients in the vegetables; this method can effectively inhibit the activity of polyphenol oxidase and maintain the quality of the plant ^[21][22][21,22]. Quick-frozen preservation can maximally maintain the natural quality of T. sinensis buds, which could be stored for about a year using this method [23].

Fresh buds of T. sinensis contain up to 90% water, and the leaves are prone to wilting after picking. Dehydration preservation technology reduces the water content of vegetables to keep the color and nutrient content of vegetables unchanged [24]. Zhao et al. (2014) used the methods of hot drying, microwave drying, vacuum drying, and vacuum freeze drying to treat T. sinensis, among which vacuum freeze drying best maintained the nutritional composition of the plant [25]; the sensory quality was better and the rehydration rate reached 51.05%. Lv (2010) conducted research about vacuum freeze-drying of T. sinensis buds. The products were obviously better than those obtained by pickled storage and ordinary refrigeration; the buds of T. sinensis had a shelf life of up to two years and were essentially the same in terms of nutrient content [26].

Modified atmosphere preservation is used to adjust the proportion of gases in the storage environment, in order to inhibit the respiration and evaporation of fruits and vegetables ^[27][28][27,28]. Zhu et al. (2014) used two types of modified atmosphere packaging materials with difference thickness (0.01 and 0.03 mm), namely, low density polyethylene (LDPE) and high density polyethylene (HDPE), on T. sinensis storage, and the experimental results showed that the packaging material of low-density polyethylene (thickness 0.03 mm) effectively inhibited the defoliation phenomenon of T. sinensis buds and delayed the aging of T. sinensis [29].

Chemical preservation means are mainly used to extend the preservation time of buds of T. sinensis by adding chemical preservatives. Although the preservation effect is good, it may be harmful to the human body and the environment. There are three main types of preservatives: adsorption, anti-corrosion, and inhibition. Ethylene adsorbent is often used in the storage and preservation of T. sinensis. It can delay post-ripening and achieve the preservation effect of buds of T. sinensis [30]. Preservatives mainly use carbendazim to kill pathogenic microorganisms on the surface of T. sinensis buds to attain the effect of preventing T. sinensis bud rot [31]. 6-Benzylaminopurine is a common inhibitory preservative in T. sinensis preservation which can prevent the aging of T. sinensis. Results show that after 45 days of storage, the color and fragrance of T. sinensis are basically unchanged [32].

Bio-preservatives are natural substances extracted from plants or animals. With the advantages of low pollution and low cost, bio-preservation technology is widely used in the market [33]. Chen et al. (2015) treated T. sinensis with 8 mmol·L⁻¹ exogenous betaine; the resulting rotting of T. sinensis buds after sixteen days of storage was not serious, the loss of chlorophyll, Vc, and total flavonoid content was alleviated, and the plant retained its commercial value [34]. Zhang et al. (2009) treated T. sinensis buds with Allium macrostemon Bunge extracts; the results showed that A. macrostemon Bunge extracts could significantly reduce the decay rate of T. sinensis and inhibit the decline of Vc content while extending the shelf life of T. sinensis buds by more than seven days [35].

There are three traditional ways to eat T. sinensis buds: (1) fresh T. sinensis buds; (2) old dish T. sinensis buds; and (3) fried T. sinensis buds. Fried T. sinensis buds are mainly eaten with flour or lotus root. T. sinensis buds can be wrapped directly with flour paste, or the T. sinensis buds can be chopped and used to fill the holes of lotus root, then wrapped with flour paste and fried with oil before sprinkling them with spices. These edible methods are very popular and taste very delicious.

In recent years, with people obtaining a deeper understanding of the health value of T. sinensis, more and more ways to eat T. sinensis have been developed. In addition to traditional eating methods, this plant is often processed into various products (Table 1). There are no studies reporting on T. sinensis bud preservation using radiation exposure, which could be a safe and low-cost procedure.