Biochemical Composition of Persimmon Fruit (Diospyros kaki L.) Bred in Ukraine

The fruit of persimmon (Diospyros kaki L.), known also as the fruit of Sharon, kaki, and Japanese persimmon, is a fleshy and fibrous tropical fruit. Persimmon belongs to the Ebenaceae family (Díaz et al. 2020), with more than 500 species. The quality and taste of the fruit depend on the growing conditions (Bejanidze et al. 2019). The People's Republic of China ranks first in the world in the area of cultivation of this crop and produced more than 3.2 million tons (approximately 76.04% of global production) in 2020 (FAO 2021). There are no industrial plantations of persimmon in Ukraine due to adverse climatic conditions, but homeowners received good yields from homestead plots. In 2022, the State Register of Plant Varieties Suitable for Distribution in Ukraine entered six persimmon cultivars bred by Ukrainian breeders N.V. Derevianko and V.M. Derevianko.

They are winter- and frost-resistant (can withstand a decrease in temperature to −32 °C), of high productivity, and good fruit quality (Derevianko et al. 2018, 2020). The high yield and high fruit quality are essential for accepting cultivars for growing (Lv et al. 2020). The mass and the size of the fruit, the index of its shape, and the hardness of the flesh are the main components of external quality, which are consequences of the content of nutrients and biologically active substances (Del Bubba et al. 2009; Veberic et al. 2010), including vitamin C, soluble sugar, anthocyanins, flavonoids, polyphenols, etc. (Lv et al. 2020). In addition, persimmon fruits contain a significant amount of pectins, which have gelling and thickening properties (Wu et al. 2021). This paper presents the characteristics of five newly bred Ukrainian persimmon cultivars in terms of fruit quality to identify those most useful for wider cultivation.

This study was conducted in the laboratory of postharvest quality of fruit and berry products of the Institute of Horticulture of the National Academy of Agrarian Sciences (NAAS) of Ukraine in 2020. The fruits of ‘Bozhyi Dar’, ‘Chuchupaka’, ‘Dar Sofiivky’, ‘Pamiat Cherniaeva’, and ‘Sosnivska’ were selected from the research plantation of the Research Farm “Novokakhovskoye” of the Rice Institute of the NAAS of Ukraine, Kherson region, at the altitude above sea level of 8 m, 46°08′34″ N and 32°57′15″ E. The climate of this territory of the southern part of the Steppe of Ukraine is moderately arid. The weather is characterized by insufficient precipitation, at a level of 355 mm per year, and the average annual sum of air temperatures is +9.6 °C (in July +23.7 °C, in January −3.4 °C).

The care of persimmon plantation was conducted according to the recommendation for the Steppe zone of Ukraine. All cultivars were grafted on the seedlings of Diospyros virginiana L. and planted in the research field in a spacing of 6 × 6 m. The fruits were harvested in a state of commercial stiffness when their firmness was 5.8 ± 1.2 kg·cm⁻². Samples for the study were taken according to the recommendations of the Methodology for assessing the quality of fruit and berry products (Kondratenko et al. 2008). The sample weight met the requirements of State Standard ISO 874. All measures were performed in triplicate.

The fresh mass of evaluated fruits varied from 48.4 g (‘Chuchupaka’) to 113.2 g (‘Pamiat Cherniaeva’). The fruit of ‘Dar Sofiivky’ also had a high fresh mass – 102 g (Table). ‘Pamiat Cherniaeva’ produced the largest fruits in addition to the heaviest. Only ‘Pamiat Cherniaeva’ formed elongated-oval fruits with shape index of 1.11. The remaining cultivars produced flat-rounded shape fruits with ratios ranging from 0.79 to 0.91. Compared to Ukrainian-bred persimmons, persimmon fruits grown in Spain have diverse masses, ranging from 52.4 g to 186.7 g, as well as their size (Diaz et al. 2020). Similar results were reported from Turkey (Altuntas et al. 2011), which means that some fruits of Ukrainian cultivars are smaller and lighter.

‘Pamiat Cherniaeva’ cultivar produced the softest fruits, with the lowest dry matter, 19.2%. Similar values were obtained by Young and How (1986). According to Díaz et al. (2020), the water content in persimmon depends on the genotype and the course of the weather. ‘Pamiat Cherniaeva’ fruits had the least soluble dry solids, sugars, and acids. ‘Chuchupaka’ fruits had the highest content of dry solids, soluble dry substances, sugars, and acids. ‘Dar Sofiivky’ produced relatively heavy and large fruits with high dry solids, soluble dry substances, and sugars but with low content of acids.

With soluble solid contents ranging from 15.97% to 24.70% (Table), fruits of Ukrainian persimmon cultivars contain more soluble solids than cultivars from Turkey, with soluble solid contents from 16.2% to 21.2% (Baltacioğlu & Artik 2013), and cultivars in Spain, with soluble solids from 15.8% to 19.4% (Díaz et al. 2020). The sugar content of Ukrainian persimmon fruits ranged from 10.27% to 12.73% (Table). Yaqub et al. (2016) reported fruit sugariness of 12.5% in Pakistani persimmons, which is comparable to Ukrainian cultivars. In contrast, sugar contents in Georgian fruit ranged from 13.0% to 19.1% (Bejanidze et al. 2019), and the sugar content in Turkish fruit was recorded as 16.3% (Altuntas et al. 2011) and 14.6% (Candir et al. 2009). The titrated acids content in Ukrainian persimmon ranged from 0.12% to 0.32% (Table). Baltacioğlu and Artik (2013), recorded that the content of titrated acids in persimmon fruits produced in Turkey ranged from 0.28% to 0.46%, while in Georgia, the titrated acid contents ranged from 0.05% to 0.18% (Bejanidze et al. 2019).

The sweetness of the fruits depends on the sugar-acid index (SAI). The higher the index value, the sweeter the fruit. The highest SAI (97.8) was found in the fruits of ‘Dar Sofiivky’, and the lowest in ‘Chuchupaka’ (39.8) and ‘Bozhyi Dar’ (37.8) (Table). These chemical results corresponded with the results of the taste test. Persimmon fruits of ‘Dar Sofiivky’ were the sweetest; the overall tasting score was 5 points (data not shown) whereas, the fruits of ‘Pamiat Cherniaeva’ and ‘Sosnivska’ had a balanced, pleasant taste, the corresponding rating was 3.5 points for both cultivars. The fruits of ‘Chuchupaka’ and ‘Bozhyi Dar’ had an unbalanced, closer to sour taste.

The structural characterization of persimmon pectin indicates that it belongs to a low-methoxy acetylated genotype (Jiang et al. 2020). The total amount of pectin ranged from 0.836% (‘Pamiat Cherniaeva’) to 1.407% (‘Dar Sofiivky’), including 1.293% of insoluble pectin. In the remaining cultivars, the amount of pectin in insoluble form was less than one percent. Given the significant range of pectin in persimmon fruits from 0.29 to 2.77% (Méndez et al. 2022), the cultivars of Ukrainian breeding can be considered highly pectin-containing.

The amount of ascorbic acid in Ukrainian cultivars varied from 28.9 mg·100 g⁻¹ (‘Bozhyi Dar’) to 59.1 mg·100 g⁻¹ (‘Sosnivska’), which is significantly more than in Turkish and Spanish persimmon fruits but less than in the genotypes studied by Homnava et al. (1990) and Butt et al. (2015). In particular, Giordani et al. (2011) found high ascorbic acid content in persimmon fruits, 47 ± 39 mg·100 g⁻¹, and Homnava et al. (1990) from 35 mg·100 g⁻¹ to 218 mg·100 g⁻¹. The concentration of ascorbic acid in persimmon grown in Turkey ranged from 14.9 mg·100 g⁻¹ to 15.8 mg·100 g⁻¹ (Baltacioğlu & Artik 2013). Persimmon fruits are a good source of polyphenols (Zillich et al. 2015), which attributes them to products with high antioxidant capacity (Yaqub et al. 2016). The results of our studies confirm the significant dependence of the level of total polyphenols on the cultivar, with a coefficient of variation of 47% (Table). The most polyphenolic substances were noted in the fruits of ‘Bozhyi Dar’ (1251 mg·100 g⁻¹) and the least in ‘Sosnivska’ (423 mg·100 g⁻¹).

As a result of this preliminary evaluation, it was found that the persimmons of ‘Dar Sofiivky’ and ‘Pamiat Cherniaeva’ grow fruits of a mass higher than 100 g. The fruits of the cultivar ‘Chuchupaka’ had the highest content of dry matter (28.9%), soluble dry substances (24.7%), sugars (12.7%), and titrated acids (0.3%) per raw mass. The fruits of ‘Dar Sofiivky’ are the sweetest (with an SAI of 97.8), and ‘Pamiat Cherniaeva’ and ‘Sosnivska’ were distinguished by a pleasant, balanced taste. The maximum ascorbic acid content was found in ‘Sosnivska’, more than 95 mg·100 g⁻¹, a polyphenols content in ‘Bozhyi Dar’ was 1251 mg·100 g⁻¹. This demonstrated that this five persimmon cultivars can be grown in the Steppe zone of Ukraine as they can accumulate fruit mass with a high-quality biochemical composition, similar to the persimmon cultivars grown in the world-leader countries in persimmon production. Among them there are cultivars more suitable for fresh consumption and others for processing.