In addition, it is said that when persimmons ripen and become sweet, the abovementioned water-soluble tannin is further oxidatively polymerized by the action of polyphenol oxidase and becomes insoluble polymers, which reduce the astringency of the fruit. There are more than 800 to 1000 cultivars of persimmon in Japan, but only 10 well known cultivars, such as the ‘Fuyu’ and ‘Hira Tanenashi’, which are widely cultivated throughout the country. Among these cultivars, Tone Wase and Fuyu were used in this study. At harvest time, Tone Wase, which is a partially astringent persimmon, contains 1% to 2% soluble tannins and is intensely astringent. Anaerobic treatment with carbon dioxide or ethanol increases the acetaldehyde content, allowing the removal of its astringency . Meanwhile, Fuyu was first reported by Dr. Onda in 1902, and since then has rapidly spread. The Fuyu’s tree is robust and produces large fruits; however, excessive fruiting causes the lateral branches to droop, which in turn results in poor fruit growth and an increase in the proportion of small fruit.
Consequently, it is necessary to regulate fruiting, mainly through disbudding. The ripening period varies by region, but in the Kinki region of Japan, it is from late October to mid-November. The process of growing persimmons is shown in Figure 1, and fruit thinning, which is the process of cutting off unripe fruit, is done in July and August. The unripe fruits that are cut off are called immature persimmons, or ‘Tekka-kaki’. The immature persimmons are left on the ground after being cut off and can be considered a discarded, unused resource. Therefore, the purpose of this study was to investigate “the effective use of immature persimmons”. An example of the use of immature fruit includes unripe Citrus unshiu. The extract of unripe Citrus unshiuhas shown anti-allergic effects in in vivo studies using type I allergy models and type IV allergy models . The relationships between fruit ripeness and the intensity of the anti-type I and anti-type IV allergic effects were investigated, and it was reported that these effects were stronger in unripe fruit and weakened as the fruit ripened. This effect has gained attention, resulting in the use of unripe Citrus unshiuas a dietary supplement .
One of the best examples of the use of persimmons in processed foods includes the use of dried persimmons; however, compared to other fruits, their application is limited. Furthermore, the processing ofimmature persimmons into dried products has the potential of minimizing the associated labor cost, as it does not directly generate income and the fruit that have already grown to a certain size are cut off before harvesting. If immature persimmons could be used for processed foods,it is expected that it would increase the motivation of persimmon growers because it would be possible to generate income from that work, and it would also increase the consumption of processed persimmons. The first step in the microencapsulation process is to emulsify a two-phase solution consisting of an oil phase and a water phase containing a gelling agent. At this stage, flavoring is added to the oil phase as a secondary function, and functional components are added to the water phase as a tertiary function. These are then used to make emulsions, which are then dried and microencapsulated. Regard for functional components is necessary, as they are intended for the elderly, prevention of aging, and age-related diseases such as skin aging, arteriosclerosis, osteoporosis, and diabetic complications.
Therefore, we searched for AGE formation inhibitors in immature persimmons. The term “AGEs” is a general term for a group of structures produced by glycation reactions and does not indicate a fixed structure. Various structures of AGEs have been elucidated to date, including those produced in vitro. AGEs are characterized by their yellowish-brown color, fluorescence, and the formation of cross-links between proteins. In recent years, AGEs have been suggested to be involved in diabetic complications, atherosclerosis, tumor growth, metastasis, inflflammatory reactions, osteoporosis, and skin aging . Therefore, we focused on anti-glycation and conducted tests to inhibit AGE formation to prevent the progression of disease and aging. Regarding flavoring and fragrances, citral, a citrus fragrance, was used to mask odors and add flavoring because when the food is ground into a gel, its flavor degrades. The flavoring and fragrance industry has been expanding annually, and the global market for food flavoring agents is estimated to be 1.5 trillion yen . Flavoring and fragrances generally contribute to the taste and flavor of foods. The citral used in this study is also widely used as a flavoring agent in citrus fruit juice beverages and foods . However, odor problems may occur during the process from food production to actual consumption. Off-flavors refer to the “odor” perceived by the addition of odorous components not originally present in the food, the increase or decrease of some odorous components present in the food, or the change in the overall balance of the odorous components . The elucidation of the conditions for the formation of off-flavors and the study of the methods to control them may lead to improvement in food processing technology and ultimately to improvement in food quality.