Comparison of the quality of dried persimmon (Diospyros kaki THUNB.) treated with medicinal plant extracts and food additives

Abstract We evaluated the direct application of different extracts from plant‐derived compounds at different ratios. The best effect was observed with the combination of 18.18% clove, 9.90% cinnamon, 9.09% licorice, 4.55% firmament, 4.55% grapefruit seed extract, and 54.54% apple cider vinegar. The combination of these compounds improved the moisture content of the fruit and showed antifungal, antibrowning, and antifungal/antibrowning effects as compared with the control following 6‐week treatment. The treatment resulted in an increase in the overall sugar concentration of dried persimmons. Antibrowning/antifungal test showed high sugar content of 30–39 °brix. The hardness of the treatment groups was similar to that of the control and decreased by 0.5 to 0.8 after 6 weeks. The evaluation of color change revealed a decreasing tendency in the value of △E during the drying period. Thus, natural extracts effectively suppressed the quality degradation during drying of persimmon and may be used to replace sulfur fumigation.

hypertension Kim, 2005;Moon et al., 2004;Park et al., 2006). Persimmon is classified as sweet and astringent persimmon. Diospyrin, a type of tannin, imparts astringency to persimmon and its water-soluble nature may impart an evident bitter taste. In combination with acetaldehyde, it changes into its insoluble form that suppresses the bitter taste . Sweet persimmon is usually eaten raw, but astringent persimmon is used to make ripen persimmon, dried persimmon, and other products. Dried persimmon displays the advantage of long-term storage; more than 50% astringent persimmon is processed into dried persimmon (Hong et al., 2001;Park et al., 2006). Studies on astringent persimmon have described the qualitative differences in persimmon tannin and natural methods for the removal of astringency as well as the physiological/ functional characteristics of tannins isolated from astringent persimmon (Seo, Jeong, & Kim, 2000;Seong & Han, 1999). Drying persimmon increases the sweetness and vitamin A content and is an important method for extending the availability period of persimmon. Dried persimmon has rich flavor and specific physical properties. Dried persimmon may be classified into dried and semidried persimmon based on its water content. In general, dried persimmon is more distributed than its semidried form because semidried persimmon containing high moisture is easily contaminated by fungus, reducing its storage and distribution period. However, there is an increase in the consumption of semidried persimmon in recent years (Hong et al., 2001). The quality of dried persimmon is dramatically affected by the drying method (Moon, Kim, & Sohn, 1993), quality of persimmon, storage and packing method, and local quality characteristics .
Dried persimmon is difficult to store at room temperature, owing to its susceptibility to fungal contamination. Dried persimmon is usually produced by solar drying method, which may cause deterioration through the incorporation of foreign matter, discoloration, and fungal contamination. During storage and distribution, the quality of dried persimmon may be rapidly decreased owing to several factors such as fungal contamination, structural hardening, sugar discoloration, powdering, and browning . Moon, Lee, Kim, and Kim (1996) observed dried persimmon produced domestically and confirmed the presence of white powder on its surface with an electron microscope.
The white powder was found to be crystallized glucose from the sugar present inside the flesh. This sugar moved to the surface with moisture and dried to form powder during the drying period. The contamination by microorganisms during drying, storage, and distribution may cause fruit deterioration and is known to be unhygienic. To prevent deterioration during the drying period for improved storage, many farmers use sulfurate after peeling. However, there are safety concerns related to the harmful effects of sulfur dioxide produced from the combustion of sulfur (Im & Lee, 2007). The use of active components separated from medicinal plants is rapidly increasing in recent years to prevent and cure various human diseases. The study of natural bioactive substances that are secondary metabolites is gaining interest. As bioactive substances display strong activities at relatively small amounts, regulation is reinforced on their use, owing to safety problems caused by some artificial synthetic products. The increase in human safety and health issues has highlighted the need for the extraction of bioactive substances from natural sources to replace artificial synthetic products (Heo et al., 2011;Kim, Hong, & Shin, 2012;Kim, Kwon, Cho, & Lee, 2012).
At present, several studies are focusing on the identification of compounds with high antioxidative activities and several health benefits from natural sources such as plants in the form of medicines and health supplements (Lee, Oh, & Hong, 2002;Shin, Kim, & Han, 1997).
Molecules such as α-tocopherol, vitamin C, carotenoid, and flavonoid are known for their natural antioxidant activities and are usually extracted from animals and plants. Secondary metabolites from plants that prevent cell damage through the removal or suppression of active oxide are identified . According to recent reports, most natural antioxidants are derived from plants and usually identified as polyphenol components (Pratt, 1992). Flavonoids are known to prevent lipid oxidation, remove active oxides, and reduce oxidative stress.
Flavonoids are widely used in food, medicines, and cosmetics to prevent or delay cancer, antiaging, heart diseases, etc. . Studies on antibiotic substances from natural sources have been performed for a long time (Ha, Lee, & Kang, 2000;Kim, Shu, & Chung, 2006) and include investigation of natural preservatives and antibiotics from herbs and spices. In addition, antibiotics from natural sources are used to suppress fungal parasites from food and human body (Lee et al., 2002;Shin et al., 1997). Garlic, onion, Thymus vulgaris (Buchanan & Shepherd, 1981;Montes-Belmont & Carvajal, 1998;Yin & Cheng, 1998), clove, cinnamon, Paeonia suffruticosa (Hwang & Han, 2003), Salvia miltiorrhiza Bunge (Choi & Han, 2003), Rhodiola sachalinensis (Choi & Han, 2003), and Morus alba root barks (Shim et al., 2004) have been used for the extraction of natural antibiotics and to extend storage life of several products through their antibiotic effects. Studies have reported the effects of pretreatment with grapefruit seed extract and cinnamon on the quality of dried persimmon (Park, Kim, Kim, Kim, & Chang, 1995;Park, Lee, Cha, Kim, & Kim, 2005;Park et al., 2006). Hong et al. (2001) reported changes in the microflora of dried persimmon during processing, preservation, manufacturing, and storage. The longer storage time was yeast and acetic acid reduced. Microbial contamination during drying of persimmon was detected using a variety of media. Penicillium was the most widely detected fungus. During the manufacturing and storage of persimmon, contamination with Penicillium and bacteria has been reported (Kim, Park, Lee, Kim, & Cha, 2004;Kwon, Jeong, Hong, Chae, & Park, 2006). In recent years, studies have reported the identification and prevention of microbial contamination. However, there are several shortcomings in the established methods to prevent contamination. In this direction, we investigated the effected of natural extracts and food additives on the quality of dried persimmons.

| Persimmon materials and treatment
Persimmons produced in 2012 were used for the antibrowning, antifungal, and antibrowning/antifungal experiments. The samples were subjected to the extraction method as described below. To obtain 5% plant extract, 50 g sample was extracted in 950 ml hot water for 2 hr, followed by centrifugation at 120 x g for 20 min.
The concentration of compounds was as follows: citric acid 3%, vitamin C 3%, potassium pyrosulfate 3%, sodium chloride 3%, cysteine 0.3%, acetic acid 1%, and extract of grapefruit seed 1%. The extraction method for four natural products was the same as mentioned above. After peeling, persimmon was soaked in 50 ml extraction liquid and air-dried, followed by the investigation of its food quality characteristics.

| Unique number and ingredient mark for antifungal
Medicinal plant extract and food additive mixing rate for dried persimmon antibacterial effect experiment. The numbers and com-

| Unique number and ingredient mark for antibrowning/antifungal
Medicinal plant extract and food additive mixing rate for dried persimmon browning prevention effect/antifungal effect experiment.

| Persimmon quality investigation and statistics
In total, 2,340 persimmons were collected from each area. The number used in the treatment was 39, of which there were nine combinations. These were hung on the drying racks similar to those used in Korean farms. Ten dried persimmons were randomly selected from each region. The investigation was conducted six times every week. Briefly, 5.0-5.5 g persimmon samples were evaluated at 110°C for 60 min. The moisture content was analyzed with a moisture analyzer (MB45 Moisture Analyzer, Ohaus, U.S.A.).
An electronic balance (Adventurer Pro, AVG264C, Ohaus, U.S.A.) TA B L E 1 Changes in the water content with antibrowning, antifungal, and antibrowning/antifungal treatments during 6-week drying of persimmon. C: control, numbers are according to materials and method

| RE SULTS AND D ISCUSS I ON
The treatment with different combinations of medicinal plant extracts and food additives showed different degree of antibrowning activity ( Table 1). As shown in Figure 1, combinations 19 Results are presented as means ± standard deviation of three replicates. DMRT analysis was performed at 6 weeks.
The treatment with different combinations of medicinal plant extracts and food additives resulted in different degree of antifungal activity ( Table 2). As shown in Figure (Table 1). The water content was the highest for the treatment group (75.8%). After 6 weeks, the water content increased as compared to that observed after 1 week, while the control showed relatively lower moisture content as compared with the treatment groups. The water content of the control group was higher than that of the treatment groups during early days but decreased in a time-dependent manner. Kim, Kang, et al. (2004) reported the water content distribution of dried persimmon of Sangju to be 32.23%-38.20%. Here, we observed around 70% moisture content in semidried persimmon after 6 weeks. This is judged that very suitable semidried persimmon quality because it is similar to the typical moisture content of 45%-50%.
TA B L E 3 Changes in hardness with antibrowning, antifungal, and antibrowning/antifungal treatments and during 6-week persimmon drying. C: control, numbers are according to materials and method. It is the period that represents the best value of the product in dried persimmon.
TA B L E 4 Changes in the color difference with antibrowning, antifungal, and antibrowning/antifungal treatments during 4-6 week drying of persimmon. C: control, numbers are according to materials and method  period. The sugar content of untreated persimmon was about 20 °brix, which increased to about 30-37 °brix after drying. The highest sugar content was reported to be 38 °brix in treatment condition 20. Kim, Kang, et al. (2004) reported a sugar content of 55 °brix for dried persimmon of Sangju area. These variations in the results may be associated with the differences in the production environment as well as the drying conditions employed.
The overall hardness of persimmon was lower throughout the drying period following treatment with medicinal plant extracts and food additives (Table 3). At 6 weeks, the hardness was higher in treatment 20, 6 weeks after on average treatment 37's hardness was lessen about 0.5, so hardness go higher than the first as a whole.
According to Lee et al. (1994), between drying period 5 days and 20 days, hardness was so soft below 0.5 kg/mm 2 that the result was similar.
Following treatment with medicinal plant extracts and food additives (Table 4)

| CON CLUS IONS
The combination of natural bioactive compounds that showed excellent activity included 18.18% clove, 9.90% cinnamon, 9.09% licorice, 4.55% firmament, 4.55% grapefruit seed extract, and 54.54% apple cider vinegar. The combination of these compounds improved the moisture content of the fruit and showed antifungal, antibrowning, and antifungal/antibrowning effects.
Thus, natural extracts effectively suppress the quality degradation during drying of persimmon and may be used to replace sulfur fumigation.

CO N FLI C T O F I NTE R E S T
None declared.

E TH I C A L S TATEM ENT
This study does not include people and animals.